Lv genset protection

M M M M
MMMM
M M M M
LV generator
protection
LowVoltageExpertGuidesN°8
E89627
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1
Contents
The Generator Set and Electrical Distribution 3
1.1. The 2 applications 4
1.1.1. Replacement energy 4
1.1.2. Energy production 6
1.2. Quality Energy 8
1.3. Services to be provided 10
The Generator Set application in LV 12
2.1. Choice of HV or LV system 12
2.2. Transfer device 13
2.2.1. Layout of feeders 13
2.2.2. Sequence 14
Protection and Monitoring of a LV Generator Set 16
3.1. Generator protection 15
3.1.1. Overload protection 16
3.1.2. Short-circuit current protection 16
3.2. Downstream LV network protection 18
3.2.1. Priority circuit protection 19
3.2.2. Safety of persons 19
3.3. The monitoring functions 19
3.3.1. Capacitor banks 20
3.3.2. Motor restart and re-acceleration 20
3.3.3. Non-linear loads - Example of a UPS 21
3.4. Generator Set parallel connection 25
3.4.1. Parallel operation 25
3.4.2. Grounding a parallel-connected Generator Set 26
3.5. The installation standards 27
3.5.1. Power definition 27
3.5.2. Safety standard requirements 27
The Schneider protection solution 29
4 .1. Micrologic and generator protection 29
4.1.1. Long Time Delay protection of the “Inverse Definite Minimum
Time Lag” type of phases (3) 29
4.1.2. Generator protection 30
4.2. Micrologic P & H for generator monitoring 31
4.2.1. Implementation 31
4.2.2. The monitoring functions 31
4.3. Micrologic for insulation fault protection 38
4.3.1. The ground protection 38
4.3.2. Residual current device (RCD) protection 39
Summary 40
5.1. Diagram 40
5.2. Comments 41
5.3. Summary 42
"Additional technical informations" chapter 43

3
The Generator Set and
Electrical Distribution
Users’ LV electrical distribution is normally supplied by an electrical utility by
means of HV/MV and MV/LV voltage transformers.
To ensure better continuity of the electricity supply, the user can implement a
direct supply from an independent thermal source (Generator Set or GS) as a
Replacement source. On isolated sites or for economic reasons, he can use this
energy source as the Main source.
This Generator Set mainly consists of:
b a thermal motor
b a generator converting this mechanical energy into electrical energy
b an electrical cubicle performing the excitation regulation and control/monitoring
functions of the various Generator Set components (thermal and electrical).
Generator Set installation must conform to installation rules and satisfy the safety
regulations applicable to the premises on which they are installed or to the
equipment that they are intended to supply.
Inshort
Generator Sets (GS) are used in HV
and LV electrical distribution.
In LV they are used as:
b replacement source
b safety source
b sometimes as a Production
Source.
When the need for Energy Quality is
essential, the Generator Set is
associated with an Uninterruptible
Power Supply (UPS).
The Protection Plan and Monitoring
of downstream LV distribution must
be defined specifically taking the
generator characteristics into
account.

4
1.1.The 2 applications
According to the application - Main electrical power supply source (Production
Set) or Replacement source of the Main source - the sizing characteristics of the
Generator Sets vary (power, output voltage, MV or LV generator, etc.).
1.1.1. Replacement energy
Principle
As a Replacement source, the Generator Set operates only should the mains
supply fail.
Mains failure can be due to:
b a random cause: fault on the network
b a voluntary cause: placing the network out of operation for maintenance
purposes.
Operation
In the Replacement source function, the Generator Set supplies the loads via a
source changeover switch.
As operation is exceptional, the Generator Set is sized strictly to supply the
power P required. The power of these Generator Sets is rarely greater than an
MVA. The power of the Replacement source LV Generator Sets ranges typically
from 250 to 800 kVA.
Main
source
Replacement
source
NC
MV
NO
LV
GS
NC: normally closed.
NO: normally open.
Figure 1: Replacement source GS.
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5
Implementation
The Generator Sets normally operate independently without connection to the
mains supply, but can be connected if necessary (parallel-connected Generator
Set) in the case of high power requirements.
NO: normally open.
Figure 2: Block diagram of a high power LV replacement GS.
E79354E
MV MV
LV LV
NCNC
NC
GS GS

6
1.1.2. Energy production
Principle
The Generator Set operates in the “Main” operating mode: it must be able to
withstand operating overloads:
b one hour overload
b one hour overload every 12 hours (Prime Power)
For example: independent energy production for a cement works.
Operation
Powers are normally high or very high (up to several tens of MVA).
Note 1: The production source Set can be LV - if it is low or medium power - and
directly supply a LV/MV step-up transformer. In this case, we can consider that
the Generator Set management functions, excluding generator protection, are at
MV level (Generator Set + MV/LV transformer global function).
HV
busbar
NC
LV
LV
HV
GS
NO: normally open.
Figure 3: Block diagram of a LV production GS with step-up transformer.
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7
E79355E
Note 2: If there is an MV Set in Production, it may be useful to have one or more
Replacement Sets in LV according to network typology (maintenance of network,
Production Set, MV fault, etc.) (maintenance du réseau, du Groupe de
Production, défaut HTA, ...).
GSGSGS
MV production set
LV replacement set
NC
LVLV
NCNC
NO: normally open.
Figure 4: Block diagram of an MV production GS with LV replacement GS.
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8
1.2.Quality Energy
To supply sensitive loads (computer, etc.), a quality energy must be implemented
that is free from breaking and with a perfectly regulated voltage.
A number of systems can be used to ensure break-free switching. These
systems are implemented in the LV system:
b reversible synchronous machine
the Set generator is permanently connected to the mains supply:
v when operating in the Main function, it operates as a synchronous motor driving
its inertia flywheel
v when operating in the Replacement function. When the Mains supply fails, the
synchronous machine, driven by its flywheel, starts to operate as a generator.
The Set’s thermal motor starts (off-load) and automatically connects as soon as it
reaches its speed at the generator.
When the Main source is restored, the Set is then synchronised on the Main
source, the Main source circuit-breaker closes and the thermal motor is
disengaged and stopped.
Electrical utility network
SN
main
source
Synchronous
machine
(compensator
or generator)
Flywheel
Magnetic
coupling
Thermal
motor
NCNC
Backed up
feeders
Non-backed up
feeders
NO: normally open.
Figure 5: Block diagram of a reversible synchronous machine.
This type of solution is not very common as it is relatively expensive to
implement.
b generator Set associated with a UPS
the generator set ensures continuity of the electrical supply. Electrical supply
involves breaking (from a few minutes to a few seconds). Energy Quality
(elimination of outages/brownouts and waveform) is obtained by an
Uninterruptible Power Supply (UPS) - equipped with a battery- which continually
supplies sensitive loads in LV.
This type of solution is advantageous as it provides sensitive loads with quality
energy during use on a Main or Replacement source.
E79357E
Inshort
Replacement Set or Safety Set.
The same functions are required:
ensure continuity of the electrical
supply should the main source fail.
However, a Safety Set must satisfy
far more exacting operating
requirements in order to guarantee
safety of the electrical installation at
all costs.

9
Electrical utility
HV incomer
NC
Mains 1
feeder
Mains 2
feeder
Sensitive feeders
Uninterruptible
power supply
Non-sensitive
load
NO: normally open.
Figure 6: Replacement GS and UPS.
Note: for very sensitive applications, should the UPS stop, the operator can ask
not to be switched to the MS in operation on Generator Set. In this case the MS is
replaced by a redundant UPS.
This system is naturally compulsory if frequency of the upstream (source) and
downstream (application) networks is different (for example source in 50 Hz,
application in 60 Hz).
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1.3.Services to be provided
According to the choice of customer or the type of risk anticipated, the Generator
Set is defined in priority as:
Safety Source only
A separate Set manages the Replacement Source function. Safety regulations,
mainly concerning buildings open to the general public such as hospitals, public
buildings, etc. define in detail electrical distribution for safety equipment
(emergency lighting, fume extraction, etc.).
These regulations aim at:
b providing fire protection (defective main source, supply of extinguishing means)
b evacuating people in the best possible conditions (emergency lighting,
evacuation path, elevator supply, etc.).
The Safety Set only supplies the loads necessary for the Safety function.
NC
Semi-lighting
1
Semi-lighting
2
Fumes extraction, elevator,
water supply, telecommunication,
other specific equipment
Other
installation
Safety
Main or replacement
Electrical safety supply
Safety
source
GS
Replacement
source
Main
source
NC
NCNC
Safety
switchboard
Main safety
switchboard
Safety
Main
NO: normally open.
Figure 7: Block diagram of an installation with a replacement GS and a safety GS.
Note: the various switches can be replaced by circuit-breakers if required by
their need for protection.
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11
Replacement Source
The Set’s purpose is to perform process controlled shutdown correctly. The
“energy quality” function, if necessary, is taken into account thanks to supplying
of sensitive loads via an Uninterruptible Power Supply (UPS) downstream from
the Set.
The Set can be specifically dedicated to the Replacement source function, but it
is allowed to operate as a Safety source if the specific Safety function
requirements are fully satisfied: for example maximum time of 10 s to obtain
voltage and frequency.
This allows more frequent operation of these Sets and thus allows them to be
more operational if necessary.
Autonomous Production Source
As a rule the set is implemented:
b to supply electrical power at lesser cost (isolated site)
b to guard against serious long-term energy downtime risks (areas with seismic
risks, etc.).

12
2.1. Choice of HV or LV system
Supply voltage is chosen mainly with respect to Generator Set power
requirements.
Generator Set as HV source
The Generator Set is normally a generator activated by a diesel motor or a gas
turbine.
The production Set application, requiring high installed powers, is thus normally
carried out using the MV system.
Generator Set as LV source
The Generator Set is normally a generator activated by a diesel motor.
The following table summarises the system choice criteria:
criteria LV HV comments
power < 2500 kVA > 2500 kVA
facility +++ +
regulations ++
LV Generator Set applications
LV Generator Sets are mainly used:
b to supply safety equipment
b to replace the Main source
b to supply temporary installations
The sectors of activity where it is necessary to have a Replacement and/or
Safety source, are very vast ranging from Tertiary to Industry.
The following table lists the main application sectors:
tertiary industrial
hospitals process,
computer Centre (bank, etc.) cement works (furnace
public building motor), …
The Generator Set
Application in LV
Inshort
A LV Generator Set normally has a
power of less than 2 500 kVA: the
typical value is around 800 kVA.
The LV Generator Set is mainly
used as a replacement and/or
safety source. The main source is
switched to the replacement source:
b with load-shedding of non-priority
loads
b by means of an automatic source
changeover switch controlled by
voltage.

13
2.2. Transfer device
It is interesting to make the source transfer (or source switching) device using
standard switchgear, adding specific features. Thus the devices will be:
b withdrawable for easier maintenance
b electrically and mechanically locked
For implementation, the distribution architecture and transfer sequence must be
studied.
2.2.1. Layout of feeders
As a rule it is not necessary to back up the entire installation. An economic
measure is to size the Generator Set for supply of the priority feeders only.
For example: sizing the Generator Set at 700 kW for a LV distribution of 2000 kVA
(only one third of feeders are considered priority).
Transfer of load supply to the replacement source can be considered in 2 ways.
Transfer with load-shedding of non-priority loads
Priority and non-priority loads are not specifically grouped: management (load-
shedding) of loads must be performed by a dedicated automation device or relay.
This configuration type requires a management auxiliary but is easier to modify or
upgrade.
NC
GS
MV
LV
Main LV board
Load-
shedding
Non-priority Priority
NO: normally open.
Figure 8: Management of priorities by load-shedding.
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14
Transfer for priority feeders only
Priority feeders are directly grouped at a specific busbar in this system. This
system requires no management auxiliaries.
GS
MV
LV
NC
NC
D1 D2
NO
Main/Standby
Non-priority circuits Priority circuits
Source 1
NO: normally open.
Figure 9: Management of priorities by grouping.
The Generator Set
Application in LV
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15
2.2.2. Sequence
Main source / Generator Set transfer
Transfer generally takes place with a short break (a few seconds) the time
required to start the Generator Set and to switch over:
b switching to Generator Set sequence
v loss of mains voltage at TA
- load-shedding of non-priority feeders (if necessary) and important feeders
v after time delay starting of Generator Set at TB
v on appearance of Generator Set voltage at TC
- opening of Main source circuit-breaker
v closing of Replacement source circuit-breaker (Generator Set) at TD
v sequenced restoration of important feeders
b switching to Main source sequence
v restoration of mains voltage at TA
v after time delay at T'B
- opening of Replacement source circuit-breaker
- restoration of non-priority feeders
v closing of Main source circuit-breaker at T'C
v stopping of Generator Set at T'D.
Main Replacement Main
Figure 11:Type 3 chronogram.
Transfer of loads on the Generator Set, the Replacement source, implies
consideration of the generator’s specific characteristics. This takes the form of an
additional study concerning:
b the protection plan (setting and discrimination)
b load management (putting back into operation)
b supply of sensitive and non-linear loads
In addition, to ensure optimised operation and maintenance, it is important to
implement additional monitoring and supervision functions (frequency and voltage
monitoring, phase unbalance, etc.).
Note: return to the Main source can be performed using a synchrocoupler to
ensure switching without voltage breaking.
E88045E
Non-priority Priority
E88044E
Figure 10: Block diagram.

16
3.1. Generator protection
The following diagram shows the electrical sizing parameters of a Generator Set.
Pn, Un and In are, respectively, the power of the thermal motor, the rated voltage
and the rated current of the generator.
Thermal
motor
Figure 12: Block diagram of a Generator Set.
Nota 1: Also remember that Generator Set sizing is optimised, i.e. that Pn is
normally around one third of normal installed power.
3.1.1. Overload protection
The generator protection curve must be analysed.
Overloads
Figure 13: Example of an overload curve T=f(I).
Standards and requirements of applications can also stipulate specific overload
conditions:
For example:
I / In t
1.1 > 1 h
1.5 30 s
The setting possibilities of the overload protection devices (or Long Time
Delay) will closely follow these requirements.
Note on overloads
b for economic reasons, the thermal motor of a Replacement Set may be strictly
sized for its nominal power. If there is an active power overload, the diesel motor
will stall. The active power balance of the priority loads must take this into account
b a production Set must be able to withstand operating overloads:
v one hour overload
v one hour overload every 12 hours (Prime Power).
(see chapter 3.5 “The installation standards”)
Protection and Monitoring
of a LV Generator Set
E79476EE79364E
Inshort
A Generator Set has specific
overload and short-circuit withstand
characteristics as a result of the
high generator reactances.
This has the following
consequences:
b for protection of people and
equipment, specific circuit-breaker
settings providing both protection of
the installation set and co-
ordination with the downstream
protection devices.
b for proper operation on duty of the
monitoring functions preventing
malfunctions and ensuring alarm
management if necessary in event
of:
v non-linear loads (harmonics)
v loads with a high energising
current (motors, LV/LV transformers,
etc.)
v parallel-connection of Generator
Sets
v operation in prolonged overload
conditions (Standby Set).
Standards specify the specific
power available according to the
type of application of a Generator
Set - production, transfer, standby.

17
3.1.2. Short-circuit current protection
3.1.2.1. Making the short-circuit current
The short-circuit current is the sum:
b of an aperiodic current
b of a damped sinusoidal current.
The short-circuit current equation shows that it is made according to three
phases.
I rms 1
subtransient
conditions
2
transient
conditions
3
steady state
conditions
generator with
compound
excitation or
over-excitation
generator with
serial exitation
T (s)fault
appears
10 to 20 ms 0.1 to 0.3 s
Figure 14: Short-circuit current level during the 3 phases.
Subtransient phase
When a short-circuit appears at the terminals of a generator, the current is first
made at a relatively high value of around 6 to 12 ln during the first cycle
(0 to 20 milliseconds).
The amplitude of the short-circuit output current is defined by three parameters:
b the subtransient reactance of the generator
b the level of excitation prior to the time of the fault and
b the impedance of the faulty circuit.
The short-circuit impedance of the generator to be considered is the subtransient
reactance expressed as a % of Uo (phase-to-neutral voltage) by the
manufacturer x”d. The typical value is 10 to 15 %.
We determine the subtransient short-circuit impedance of the generator:
X"d
U2
n
S
x"d
100
= where S = 3UN
IN
.
Transient phase
The transient phase is placed 100 to 500 ms after the time of the fault. Starting
from the value of the fault current of the subtransient period, the current drops to
1.5 to 2 times the current ln.
The short-circuit impedance to be considered for this period is the transient
reactance expressed as a % Uo by the manufacturer x'd. The typical value is 20
to 30 %.
Steady state phase
The steady state occurs above 500 ms.
When the fault persists, Set output voltage collapses and the exciter regulation
seeks to raise this output voltage. The result is a stabilised sustained short-circuit
current:
b if generator excitation does not increase during a short-circuit (no field over-
excitation) but is maintained at the level preceding the fault, the current stabilises
at a value that is given by the synchronous reactance Xd of the generator. The
typical value of xd is greater than 200 %. Consequently, the final current will be
less than the full-load current of the generator, normally around 0.5 ln.
b If the generator is equipped with maximum field excitation (field overriding) or
with compound excitation, the excitation “surge” voltage will cause the fault
current to increase for 10 seconds, normally to 2 to 3 times the full-load current
of the generator.
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3.1.2.2. Calculating the short-circuit current
Manufacturers normally specify the impedance values and time constants
required for analysis of operation in transient or steady state conditions.
Impedance table: Leroy Somer generator
(kVA) 75 200 400 800 1600 2500
x"d (%) 10.5 10.4 12.9 10.5 18.8 19.1
x'd (%) 21 15.6 19.4 18 33.8 30.2
x'd (%) 280 291 358 280 404 292
Resistances are always negligible compared with reactances.
The parameters for the short-circuit current study are:
Value of the short-circuit current at generator terminals
Short-circuit current strength in transient conditions is:
ors s
UN
is the generator output phase-to-phase voltage (Main source).
Note: this value can be compared with the short-circuit current at the terminals
of a transformer. Thus, for the same power, currents in event of a short-circuit
close to a generator will be 5 to 6 times weaker than those that may occur with a
transformer (main source).
This difference is accentuated further still by the fact that generator set power is
normally less than that of the transformer.
Example
GS
MV
LV
NC
NC
Main/standby
Non-priority circuits Priority circuits
NO: normally open.
Figure 15.
When the LV network is supplied by the Main source 1 of 2000 kA, the short-
circuit current is 42 kA at the main LV board busbar. When the LV network is
supplied by the Replacement Source 2 of 500 kVA with transient reactance of
30 %, the short-circuit current is made at approx. 2.5 kA, i.e. at a value 16 times
weaker than with the Main source.
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19
3.2. Downstream LV network protection
3.2.1. Priority circuit protection
Choice of breaking capacity
This must be systematically checked with the characteristics of the main source
(HV/LV transformer).
Choice and setting of the Short Time Delay releases
b subdistribution boards
the ratings of the protection devices for the subdistribution and final distribution
circuits are always lower than Generator Set rated current. Consequently, except
in special cases, conditions are similar to supply by the transformer.
b main LV switchboard
v the sizing of the main feeder protection devices is normally similar to that of the
Generator Set. Setting of the STD must allow for the short-circuit characteristic of
the Generator Set (see 3.1.2.).
v discrimination of protection devices on the priority feeders must be provided in
generator set operation (it can even be compulsory for safety feeders).
It is necessary to check proper staggering of STD setting of the protection
devices of the main feeders with that of the subdistribution protection devices
downstream (normally set for distribution circuits at 10 ln).
Note: when operating on the Generator Set, use of a low sensitivity RCD
enables management of the insulation fault and ensures very simple
discrimination.
3.2.2. Safety of people
In the IT (2nd
fault) and TN grounding systems, protection of people against
indirect contacts is provided by the STD protection of circuit-breakers. Their
operation on a fault must be ensured, whether the installation is supplied by the
Main source (Transformer) or by the Replacement source (Generator Set).
Calculating the insulation fault current
Zero-sequence reactance formulated as a % of Uo by the manufacturer x’o.
The typical value is 8 %.
The phase-to-neutral single-phase short-circuit current is given by:
The insulation fault current in the TN system is slightly greater than the three-
phase fault current: for example, in event of an insulation fault on the system in
the previous example, the insulation fault current is equal to 3 kA.

20
3.3.The monitoring functions
Due to the specific characteristics of the generator and its regulation, the proper
operating parameters of the Generator Set must be monitored when special
loads are implemented.
The behaviour of the generator is different from that of the transformer:
b the active power it supplies is optimised for a power factor = 0.8
b at less than power factor 0.8, the generator may, by increased excitation,
supply part of the reactive power.
3.3.1. Capacitor bank
An off-load generator connected to a capacitor bank may self-arc, consequently
increasing its overvoltage.
The capacitor banks used for power factor regulation must therefore be
disconnected. This operation can be performed by sending the stopping setpoint
to the regulator (if it is connected to the system managing the source switchings)
or by opening the circuit-breaker supplying the capacitors.
If capacitors continue to be necessary, do not use regulation of the power factor
relay in this case (incorrect and over-slow setting).
3.3.2. Motor restart and re-acceleration
A generator can supply at most in transient period a current of between 3 and 5
times its nominal current.
A motor absorbs roughly 6 ln for 2 to 20 s during start-up.
If Σ Pmotors is high, simultaneous start-up of loads generates a high pick-up
current that can be damaging: large voltage drop, due to the high value of the
Generator Set transient and subtransient reactances (20 % to 30 %), with a risk
of:
b non-starting of motors
b temperature rise linked to the prolonged starting time due to the voltage drop
b tripping of the thermal protection devices.
Moreover, the network and the actuators are disturbed by the voltage drop.
Application
A generator supplies a set of motors.
Generator short-circuit characteristics: PN = 130 kVA at a power factor of 0.8,
ln = 150 A
X’d = 20 % (for example) hence lsc = 750 A.
b the Σ Pmotors is 45 kW (45 % of generator power)
Calculating voltage drop at start-up:
Σ Motors = 45 kW, lM = 81 A, hence a starting current ld = 480 A for 2 to 20 s.
Voltage drop on the busbar for simultaneous motor starting:
≈
IN-Id
Icc-IN
∆U
U
en %
∆U ≈ 55 %
which is not supportable for motors (failure to start).
b the Σ Pmotors is 20 kW (20 % of generator power)
Calculating voltage drop at start-up:
Σ Motors = 20 kW, lM = 35 A, hence a starting current ld = 210 A for 2 to 20 s.
Voltage drop on the busbar:
≈
IN-Id
Icc-IN
∆U
U
en %
∆U ≈ 10 %
which is supportable but high.

21
GS
Remote control 2
Remote control 1
Priority
motors
Priority
resistive loads
Figure 16: Restarting of priority motors (Σ P > 1/3 Pn).
Restarting tips:
b if the Pmax of the largest motor > 1/3 Pn, a progressive starter must be
installed on this motor
b if Σ Pmotors > 1/3 Pn, motor cascade restarting must be managed by a PLC
b if Σ Pmotors < 1/3 Pn, there are no restarting problems.
3.3.3. Non-linear loads - Example of a UPS
Non-linear loads
These are mainly:
b saturated magnetic circuits
b discharge lamps, fluorescent lights
b electronic converters:
v computer processing systems: PC, computers, etc.
v etc.
These loads generate harmonic currents: supplied by a Generator Set, this can
create high voltage distortion due to the low short-circuit power of the generator.
Uninterruptible Power Supply (UPS)
The combination of a UPS and generator set is the best solution for ensuring
quality power supply with long autonomy for the supply of sensitive loads.
It is also a non-linear load due to the input rectifier. On source switching, the
autonomy of the UPS on battery must allow starting and connection of the
Generator Set.
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22
Electrical utility
HV incomer
NC
Mains 1
feeder
Mains 2
feeder
Sensitive feeders
Uninterruptible
power supply
Non-sensitive
load
Figure 17: GS-UPS combination for Quality Energy.
UPS power
UPS inrush power must allow for:
b nominal power of the downstream loads. This is the sum of the apparent
powers Pa absorbed by each application. Furthermore, so as not to oversize the
installation, the overload capacities at UPS level must be considered (for
example: 1.5 ln for 1 minute and 1.25 ln for 10 minutes).
b the power required to recharge the battery: this current is proportional to the
autonomy required for a given power. The sizing Sr of a UPS is given by:
Sr = 1.17 x Pn.
The table below defines the pick-up currents and protection devices for supplying
the rectifier (Mains 1) and the standby mains (Mains 2).
Table: pick-up currents and protection devices
nominal power current value (A)
Pn mains 1 with 3Ph battery mains 2 or 3Ph application
400 V - l1 400 V lu
40 kVA 86 60.5
60 kVA 123 91
80 kVA 158 121
100 kVA 198 151
120 kVA 240 182
160 kVA 317 243
200 kVA 395 304
250 kVA 493 360
300 kVA 590 456
400 kVA 793 608
500 kVA 990 760
600 kVA 1180 912
800 kVA 1648 1215
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23
Short-circuit downstream of a UPS
The UPS use PWM switch mode power supply to reproduce the output voltage.
As a rule their current regulation will limit current to 1.5 times ln. The output filter
will be able to supply for 1/4 of a period loads at 4 or 5 times ln: this may be
sufficient to selectively eliminate short-circuits on small feeders and thus
guarantee continuity of supply.
On the other hand, on large feeders, as current is limited, the short-circuit may
remain steady and the UPS immediately switches to the standby supply source
to increase short-circuit current and ensure tripping of the downstream protection
devices.
Generator Set/UPS combination
b restarting the Rectifier on a Generator Set
The UPS rectifier can be equipped with a progressive starting system of the
charger to prevent harmful pick-up currents when installation supply switches to
the Generator Set.
Mains1
GS starting
UPS charger
starting
5 to 10 s
Figure 18: Progressive starting of a type 2 UPS rectifier.
b harmonics and voltage distortion
total voltage distortion t is defined by:
τ(%) =
Uh2
n
Uf
where Uhn is the n order voltage harmonic.
This value depends on:
v the harmonic currents generated by the rectifier (proportional to the power Sr of
the rectifier)
v the longitudinal subtransient reactance X”d of the generator
v the power Sg of the generator.
We define U'Rcc (%) = X"d
SR
SG
the generator relative short-circuit voltage,
brought to rectifier power
i.e. τ = f(U’RCC
).
Note 1: as subtransient reactance is great, harmonic distortion is normally too
high compared with the tolerated value (7 to 8 %) for reasonable economic sizing
of the generator: use of a suitable filter is an appropriate and cost-effective
solution.
Note 2: harmonic distortion is not harmful for the rectifier but may be harmful for
the other loads supplied in parallel on the rectifier.
E79477E

24
Application
A chart is used to find the distortion t as a function of U’RCC
Without filter
With filter
(incorporated)
(voltage harmonic distortion)
Figure 19: Chart for calculating type 3 harmonic distortion.
The chart gives:
b either t as a function of U’RCC
b or U’RCC
as a function of τ
From which Generator Set sizing, Sg, is determined.
Example
b generator sizing
v 300 kVA UPS without filter, subtransient reactance of 15 %
The power Sr of the rectifier is Sr = 1.17 x 300 kVA = 351 kVA
For a τ < 7 %, the chart gives U’RCC
= 4 %, power Sg is:
SG = 351 x
15
4
= 1 400 kVA
v 300 kVA UPS with filter, subtransient reactance of 15 %
For τ = 5 %, the calculation gives U’RCC
= 12 %, power Sg is:
SG = 351 x
15
12
= 500 kVA
Note: with an upstream transformer of 630 kVA on the 300 kVA UPS without filter,
the 5 % ratio would be obtained.
The result is that operation on Generator Set must be continually monitored for
harmonic currents.
If voltage harmonic distortion is too great, use of a filter on the network is the
most effective solution to bring it back to values that can be tolerated by sensitive
loads.
E79366E

25
3.4.Generator Set parallel-connection
Parallel-connection of the Generator Set irrespective of the application type -
Safety source, Replacement source or Production source - requires finer
management of connection, i.e. additional monitoring functions.
3.4.1. Parallel operation
As Generator Sets generate energy in parallel on the same load, they must be
synchronised properly (voltage, frequency) and load distribution must be
balanced properly. This function is performed by the regulator of each Generator
Set (thermal and excitation regulation). The parameters (frequency, voltage) are
monitored before connection: if the values of these parameters are correct,
connection can take place.
3.4.1.1. Insulation faults
An insulation fault inside the metal casing of a generator set may seriously
damage the generator of this set if the latter resembles a phase-to-neutral short-
circuit. The fault must be detected and eliminated quickly, else the other
generators will generate energy in the fault and trip on overload: installation
continuity of supply will no longer be guaranteed. Ground Fault Protection (GFP)
built into the generator circuit is used to:
b quickly disconnect the faulty generator and preserve continuity of supply
b act at the faulty generator control circuits to stop it and reduce the risk of
damage.
This GFP is of the “Residual sensing” type and must be installed as close as
possible to the protection device as per a TN-C/TN-S* system at each generator
set with grounding of frames by a separate PE.
* The system is in TN-C for sets seen as the “generator” and in TN-S for sets seen as “loads”.
RS RS
N
PE
PE
PE
Phases
PEN PE PEN
generator no. 1 generator no. 2
protected
area
unprotected
area
Figure 20.
E51145E

26
3.4.1.2. Generator Set faults as a load
One of the parallel-connected Generator Sets may no longer operate as a
generator but as a motor (by loss of its excitation for example). This may
generate overloading of the other Generator Set(s) and thus place the electrical
installation out of operation.
To check that the Generator Set really is supplying the installation with power
(operation as a generator), you need to check the proper flow direction of energy
on the coupling busbar using a specific “reverse power” check. Should a fault
occur, i.e. the Set operates as a motor, this function will eliminate the faulty Set.
SetSet.
MV incomer
HV busbar
LV
GS
Figure 21: Energy transfer direction - GS as a generator.
GS
LV
HV busbar
MV incomer
Figure 22: Energy transfer direction - GS as a load.
3.4.2. Grounding parallel-connected Generator Sets
Grounding of connected Generator Sets may lead to circulation of earth fault
currents (3rd
order and multiple of 3 harmonics) by connection of Neutrals for
common grounding (grounding system of the TN or TT type). Consequently, to
prevent these currents from flowing between the Generator Sets, we recommend
that you install a decoupling resistance in the grounding circuit.
E88043EE88015E

27
3.5.The installation standards
There are no specific electrical installation rules for Generator Sets performing
Replacement or Production functions.
Continuity of supply requirements must be taken into account for Safety Sets.
For mobile Sets, installation of residual current protection at 30 mA may be
required to guarantee safety of people whatever the connection.
3.5.1. Power definition
The notion of active power delivered is defined by thermal motor sizing. Standard
ISO 3046-1 for diesel motors states three alternatives for defining nominal power
and specifies the overload capacity definition. The notion of power is thus defined
by:
b continuous power
the motor can supply 100 % of its nominal power for an unlimited period of time.
This is the notion used for a Production Set.
b prime Power (PP)
the motor can supply a basic power for an unlimited period of time and 100 % of
nominal power for a specific period of time. Both period and basic power vary
according to the manufacturer. A typical example would be a basic power of 70 %
of nominal power and 100 % of nominal load for 500 hours a year.
Overload capacity: this is defined by 10 % of additional power for 1 hour in a
period of 12 operating hours.
b standby power
this is the maximum power that the machine can deliver over a limited period,
normally less than 500 hours a year. This definition must only be applied to
generator sets operating solely as standby sets. As the motor is not able to
supply greater power, a safety factor of at least 10 % must be applied to
determine necessary standby power. If nominal power is determined by standby
power, there is no more margin left for overload.
Thus, the same diesel set can be defined by:
b a continuous power of 1550 kW
b a prime power PP of 1760 kW and
b a standby power of 1880 kW.
3.5.1.1. Protection device settings
Available power values and tolerated overload times must be considered to
calculate installation sizing and protection device settings. This can be specified
by installation standards.
For example, even if the NEC (National Electrical Code - US Standard in Section
445-4 (a)) does not indicate a precise acceptable overload percentage, the
values normally specified for generator protection range between 100 % and
125 % of generator nominal current at nominal power and at nominal power factor
(typically for 0.8). Moreover, Section 445-4 (a) to (e) EX. allows a 100 %
overshoot of nominal current for more than 60 seconds.
3.5.2. Safety standard requirements
3.5.2.1. Protection device discrimination
In safety terms, electrical installation standards can recommend selective tripping
of protection devices for all circuits supplying equipment:
b safety equipment (fire pump, smoke extraction motor, etc.)
b or for which interruption in energy supply would generate a serious risk.
For example, the NEC requires co-ordination of protection devices for most
elevator supply circuits (Section 620-62). Furthermore, section 4-5-1 of
publication NFPA (1) 1110, Emergency and Stand-by Power Systems, requires
that manufacturers “optimise selective tripping of Short-Circuit Protection
Devices”.
(1) Publication of the National Association of Fire Protection

28
3.5.2.2. Alarm processing
A Safety set must never stop, but must supply safety equipment and anti-panic
devices even if this means damage to itself.
On the other hand, safety regulations will require increasingly rigorous preventive
maintenance of the Set to ensure safer operation. Consequently, certain thermal
motor alarms - water temperature, oil temperature, oil level - or generator alarms
- temperature, overloads - must not cause the Safety Set to trip but must be
locked to ensure maintenance or subsequent repairs once installation supply
switches back to the Main Source.

29
The Schneider
protection solution
4 .1. Micrologic and generator protection
With respect to generator protection, the Micrologic releases of the Masterpact
NT, NW and Compact NS ranges allow optimised settings for fine generator
protection.
4.1.1. LongTime Delay protection of the “Inverse
Definite MinimumTime Lag” type of phases (3)
The Micrologic P and H include in the microprocessor the various IDMTL type
curves. These curves of variable slope are used to enhance:
b discrimination with fuses placed upstream (HV) of the power circuit-breaker
b co-ordination with the MV protection relays that may be of the IDMTL type
b protection of specific applications.
Five slopes are proposed:
b definite Time DT
b standard inverse time SIT, curve in i0.5t
b very inverse time VIT, curve in it
b extremely inverse time EIT, curve in l2t
b high voltage fuse HVF, curve in i4t
The slope is calculated as per the formula:
)(
( ) .
Tr =time delay band
B = type of curve DT, SIT, VIT, EIT, HVF
For the various time delay bands and slopes, the tripping thresholds in seconds
at 1.5 lr are as follows:
time delay 0,5 s 1 s 2 s 4 s 8 s 12 s 16 s 20 s 24 s
band
DT 0,5 1 2 4 8 12 16 20 24
SIT 3,2 6,4 12,9 25,8 51,6 77,4 103 129 155
VIT 5 10 20 40 80 120 160 200 240
EIT 14 28 56 112 224 336 448 560 672
HVF 159 319 637 1300 2600 3800 5100 6400 7700
b intermittent overloads and IDMTL slopes
As long as the circuit-breaker remains closed, the intermittent overloads are
taken into account to simulate their effects on the conductors. This function
optimises the circuit-breaker tripping time.
Inshort
Via the Micrologic releases of the
Masterpact and Compact NS circuit-
breaker ranges, Schneider has
taken into account the specific
features of the set generators.
These devices perform:
b the essential protection functions
b additional monitoring functions
such as measurement of relevant
proper operation parameters
b connection functions, …
This switchgear guarantees
optimised continuity of supply for
operators.
E89636

30
4.1.2. Generator protection
The many setting possibilities of the LTD protection slope allow the generator
thermal overload curve to be followed closely. The low setting of the STD
protection is compatible with the short-circuit behaviour of the generator.
Optimised protection of the generator thanks to the Micrologic releases of the NT,
NW and Compact NS ranges guarantees optimum continuity of supply.
Figure 23: Masterpact NW/NT and Compact NS overload curves.
Generator overload
conditions
Circuit-breaker VIT
protection curve
Generator
short-circuit
conditions
Figure 24: IDMTL curves and generator overload curve.
.
The Schneider
protection solution
E88696EE89628

31
4.2.Micrologic P & H for generator
monitoring
The Micrologic P and H incorporate other current, voltage, power and frequency
protection and/or monitoring functions suited to loads such as motors, generators
and transformers.
4.2.1. Implementation
In the control unit “setting” menu, the operator selectors the functions that he
wishes to activate and accesses the various thresholds to be configured.
All the settings are made via the keys available on the front face or by remote
transmission.
For all functions, except for phase rotation direction, four thresholds must be set:
b activation threshold (1)
b activation time delay (2)
b de-activation threshold (3)
b de-activation time delay (4).
Activation
threshold
De-activation
threshold
Relay
output
Activation
time delay
De-activation
time delay
Figure 25.
When the function is activated, according to operator configuration, it can result
either in tripping or in an alarm, or in both.
E88008E

32
The Schneider
protection solution
4.2.2.The monitoring functions
4.2.1.1. Current unbalance
b application:
the acceptable values for current negative phase sequence components are
approximately:
v 15 % for generators
v 20 % for motors
As current unbalance effects are thermal and thus slow, the tripping threshold for
this protection must be configured according to the thermal time constant of the
equipment (a few minutes).
It can be used as an alarm to allow better distribution of single-phase loads.
I mean
Figure 26.
b principle:
the function compares a current unbalance to the threshold previously set by the
user. The current unbalance Dl is the value as a % of the difference, E max,
between maximum current and mean current, lmean.
Imean = (I1+I2+I3)/3.
Emax = max (Ii) - Imean.
∆I = Emax/Imean.
The activation and de-activation thresholds, configured by the user, are a % of
Imean:
∆l = 5 % represents a relatively small unbalance (l1 = 4000 A, l2 = 3800 A, l3 =
3600 A).
∆l = 90 % represents a strongly unbalanced power supply (l1 = 4000 A, l2 = 1200
A, l3 = 1120 A).
Example 1: I1 = 4000 A, I2 = 2000 A, I3 = 3300 A.
Imean = 3100 A.
Emax = I2 - Imoy.
∆I = Emax/Imean, ∆I = 35 %.
Nota : calculation of current (or voltage) unbalance in HV distribution is normally
used: Iunbal(%) = 100 x (Iinverse)/(Idirect)
Micrologic calculates current unbalance as per the formula:
Iunbal(%) = 100 x (lmax)/(lmean)
Both calculation modes yield similar results.
b current unbalance setting:
setting range setting step accuracy
activation 5 à 60 % of Imean 1 % -10 % to 0 %
threshold
activation 1 to 40 s 1 s -20 % to 0 %
time delay
de-activation -5 % to 0 % of 1 % -10 % to 0 %
threshold activation threshold
de-activation 10 to 360 s 1 s -20 % to 0 %
time delay
E88009E

33
4.2.2.2. Overcurrent
b application:
overcurrent protection is suitable for:
v monitoring cyclic loads (prevent temperature rise of loads, etc.)
v managing consumption (guard against overshoots).
I consumed
I sizing
Activation
1 h
Ta = activation time delay
Td = de-activation time delay
Figure 27: Consumption monitoring.
This is used to calculate the mean value of consumed current. It can deliver a
load shedding order to remain within the limits:
v of the supplier’s contract - Main source -
v or of delivered power - Replacement source.
It provides thermal type protection for each phase and for the neutral (dry
transformers).
b principle:
this function calculates the mean value of each current of the three phases and
the neutral over a time programmable between 5 minutes and one hour and over
a sliding window refreshed every 15 seconds.
b overcurrent setting
activation 0.2 to 10 In 1 A ± 6.6 %
threshold
activation 1500 s 15 s -20 % to 0 %
time delay
de-activation 0.2 to 10 In of 1 A ± 6.6 %
time delay
4.2.2.3.Voltage unbalance
b application:
detection of voltage unbalance or loss.
Voltage unbalance protection is more suitable to the installation as a whole,
whereas current unbalance protection is more suitable for loads.
This is because voltage unbalance will affect all the feeders of this installation,
while current unbalance may vary according to its position in the installation.
b principle:
the function compares voltage unbalance to the threshold set beforehand by the
user.
Voltage unbalance DU is the value as a % of the difference, E max, between
maximum voltage and the mean value of the phase-to-phase voltages, Umean.
Umean = (U12 + U23 + U31)/3.
Emax = max(Ui) - Umean.
DU= Emax/Umean.
E88010E

34
The Schneider
protection solution
The activation and de-activation thresholds, configured by the user, are a % of U
max:
∆U = 5 % represents a relatively small unbalance
∆U = 90 % represents a strongly unbalanced power supply
Example
Case similar to a phase loss associated with unbalance on the other phases.
U12 = 330 V, U23 = 390 V, U31 = 10 V.
Umean = 243,3 V.
Emax = U31 - Umean.
∆U = Emax/Umean, ∆U = 96 %.
b voltage unbalance setting:
activation 2 à 30 % of Umean 1 % -10 % to 0 %
threshold
activation 1 to 40 s 1 s -20 % to 0 %
time delay
de-activation 2 % of activation 1 % -10 % to 0 %
threshold threshold
time delay
4.2.2.4. Overvoltage and undervoltage
b application:
the overvoltage and undervoltage protections can be used to:
v check output voltage of a generator
v prevent transformer saturation (overvoltage)
v switch from the Main to the Replacement source
v prevent temperature rise on motor starting (undervoltage)
Note: in actual fact, voltage drops and rises seriously affect the performance of
the loads supplied (see motor characteristics table below).
Voltage variation as a %
Motor characteristics Un -10 % Un -5 % Un Un +5 % Un+10%
Torque curve 0,81 0,90 1 1,10 1,21
Slipping 1,23 1,11 1 0,91 0,83
Nominal current 1,10 1,05 1 0,98 0,98
Nominal efficiency 0,97 0,98 1 1,00 0,98
Nominal power factor 1,03 1,02 1 0,97 0,94
Starting current 0,90 0,95 1 1,05 1,10
Nominal temp. rise 1,18 1,05 1 1 1,10
Off-load P (Watt) 0,85 0,92 1 1,12 1,25
b principle:
the function is activated when one of the three phase-to-phase voltages (U12,
U23, U31) is below (or above) the threshold set by the user for a time longer than
the time delay. It is de-activated when the 3 phase-to-phase voltages move back
above (or below) the de-activation threshold for a time longer than the time delay.
U max.
U12 U23 U31
U min.
Figure 28.
E88011E

35
b undervoltage setting:
activation 100 à 690 V 5 V 0 % to 5 %
threshold
activation 0.2 to 5 s 0.1 s 0 % to 20 %
time delay
de-activation 690 V of activation 5 V 0 % to 5 %
threshold threshold
de-activation 0.2 to 36 s 0.1 s 0 % to 20 %
time delay
b overvoltage setting:
activation 100 à 1200 V 5 V -5 % to 0 %
threshold
activation 0.2 to 5 s 0.1 s 0 % to 20 %
time delay
de-activation 100 V of activation 5 V -5 % to 0 %
threshold threshold
de-activation 0.2 to 36 s 0.1 s 0 % to 20 %
time delay
4.2.2.5 Reverse active power
b application
reverse power protection is used to protect generators connected with the mains
(as an auxiliary or standby source) and generators operating in parallel
autonomously (e.g. marine).
Note
For protection of generators driven by diesel sets, the threshold must be set
between 5 and 20 % of generator active power for a period of 2 seconds.
For protection of generators driven by steam turbines, the threshold must be set
between 1 and 5 % of active power for a period of 2 seconds
b principle:
the function is activated when the active power flowing in the opposite flow
direction to the energy defined by the user, is greater than the activation
threshold for a time longer than the time delay.
Activation zone De-activation
zone
De-activation time delay
Activation time delay
Activation
threshold
De-activation
threshold
Reverse power
Figure 29.
E88012E

36
The Schneider
protection solution
b reverse power setting:
activation 5 kW to 500 kW 5 kW ± 2.5 %
threshold
activation 0.2 to 20 s 0.1 s -20 % to 0 %
time delay
de-activation 5 kW of activation 5 kW ± 2.5 %
threshold threshold
de-activation 1 to 360 s 0.1 s -20 % to 0 %
time delay
4.2.2.6. Over frequency and under frequency
b causes
incorrect operation of generator / motor set
frequency reduction is possible when a generator is on overload
frequency increase is possible should the generator begin racing after losing its
load.
b application:
over frequency and under frequency protection is used to:
Check generator frequency
Check frequency at motor terminals
Prevent saturation of transformers further to a frequency reduction.
b principle:
the function is activated when frequency exceeds the programmed threshold for
a time longer than the time delay.
Over frequency monitoring
De-activation
time delay
Activation
time delay
Over F
de-activation
zone Over F
activation
zone
De-activation
threshold
Activation
threshold
Frequency
Figure 30: Operation for overfrequency.
De-activation
time delay
Activation
time delay
Under F
de-activation
zoneUnder F
activation
zone
De-activation
threshold
Activation
threshold
Frequency
Figure 31: Operation for underfrequency.
E88013EE88007E

37
b overfrequency setting:
activation 45 to 540 Hz 0.5 Hz ± 0.5 Hz
threshold
time delay
de-activation 540 Hz of 0.5 Hz ± 0.5 Hz
time delay
b underfrequency setting:
activation 45 to 540 Hz 0.5 Hz ± 0.5 Hz
threshold
time delay
de-activation 45 Hz of 0.5 Hz ± 0.5 Hz
time delay
4.2.2.7 Phase rotation direction
b application:
phase reversal protection is used to:
v check the rotation direction of three-phase motors (e.g. boats berthed)
v prevent connection of generators to the electrical network if rotation direction is
reversed
b principle:
the function compares the phase succession order.
In event of reversal, protection is activated after 300 ms (tripping or alarm).
b phase rotation direction setting:
setting range
DF Φ1, Φ2, Φ3 or Φ1, Φ3, Φ2
time delay 300 ms

38
The Schneider
protection solution
4.3.Micrologic for insulation fault
protection
Currents due to insulation faults can be dangerous for people (risk of indirect
contact) and equipment (fire risk).
To provide protection and satisfy all installation systems as completely as
possible, the Micrologic range incorporates as standard:
b on 6.0 units, ground protection
b on 7.0 units, residual current protection.
4.3.1. Ground protection
b fire protection:
this is stipulated by the NEC (National Electric Code) in the USA to avoid risk of
fire that could occur in event of an impedance-grounded (arc) fault, not detected
by the standard L, S, I protection devices (fault smaller than the STD threshold or
intermittent fault).
b protection of people:
this is also used on TN-S networks with very long cables to guarantee
instantaneous tripping in event of an insulation fault. Ground protection is
performed according to two systems.
4.3.1.1. Residual sensor
The “residual” type protection determines earth fault current by the vector sum of
phase and neutral currents.
This protection detects faults downstream of the circuit-breaker.
A CT is placed on each of the phases and the neutral (if distributed).
For the Masterpacts, the CTs are built into the circuit-breakers.
Circuit-breaker
with built-in
MX protection
Figure 32.
The Neutral CT provides both ground/residual protection and overload protection
of the neutral conductor.
E88017E

39
4.3.1.2. Source Ground Return (SGR)
The “Source Ground Return” system directly measures the earth fault current by
a specific external sensor.
This protection detects faults upstream and downstream of the circuit-breaker.
It is only possible at the supply end of the LV installation.
Figure 33.
Note: the SGR CT is specific to this application.
The Ground protection and Neutral protection are separate and thus can be
combined.
Setting the protection devices
Ground protection can be set for its threshold (limited to 1200 A) by 9 bands and
by its time delay (same as the Short Time Delay).
To enhance discrimination with fuses or other circuit-breakers, part of the ground
protection curve can be converted into a reverse curve by choosing the l2
tON
setting.
The SGR protection requires use of the MDGF module.
4.3.2. Residual current device (RCD) protection or
“zero sequence” system
RCD protection is stipulated by installation standards (IEC 60 364) for protection
of people and equipment in the following cases:
b TT type grounding systems, in which currents resulting from insulation faults
are small
b TN-S type networks with very long cables, in which the instantaneous threshold
is not sufficient to protect a short-circuit at the end of the line
b IT networks with very long cables.
This protection is also used to provide additional fire protection.
Its threshold from 500 mA to 30 A and time delay can be set to ensure residual
current discrimination.
Figure 34.
An external rectangular toroid sensor is compulsory.
E88019E88018

40
Source IT safety
source
TN-S replacement
source
GS GS
GS GS
Non-priority
feeders,
heating, etc.
Safety
feeders
Non-sensitive
priority feeders,
lighting, elevator, etc.
Sensitive
feeders,
computer, etc.300 kVA
Chassis
COM
module
Source
IT safety
source
TN-S
replacement
source
Communication
bus
Proprietary
bus
Non-priority
feeders
Chassis
COM
moduleMain LV board
Main LV board
Summary
5.1.Diagram
A typical example of a high power electrical installation for an office building (see
Note 1).
E88014E

41
5.2. Comments
Source to protect Protection Monitoring
Main source
Replacement source
Safety source
E88104
E88103E
Note 1: in the diagram on the previous page, the
Safety Set and the Replacement Set are separate:
this is advantageous only if the priority and safety
feeders are physically separate. As explained in
paragraph 1.3, the 2 functions are normally grouped.
The following diagram gives an example of this:
The Long and Short Time Delay protection settings
are of the Distribution type. Discrimination with
downstream feeders is of the time type and total.
The set is optimised with exact dimensioning.
Setting of the LTD protection will follow the Set’s
protection curve and setting of the STD protection
will be low (from 1.5 to 2.5 lg).
Discrimination with downstream priority feeders
must allow for the low settings (in particular for the
STD).
For feeders supplied by the UPS, discrimination
must be ensured with the downstream feeders (this
is because the UPS switches to mains 2 to perform
the discrimination function).
The Set must operate in all circumstances.
The settings made will eliminate nuisance tripping.
Discrimination must allow for these settings and
choose a downstream circuit distribution that will
enable this.
The monitoring functions mainly concern
verification of inrush power: this allows use, if
necessary, of load shedding to cope with load
peaks.
The Set supplies priority feeders. As our
example is an office building, these feeders are
often not linear. Due to the power ratio and high
subtransient impedances between the Set and
the Main source (transformer), voltage total
harmonic distortion (THDu) is often very high
and greater than load withstand value (even for
non-sensitive loads).
1. Installation of a Micrologic H ensures
permanent monitoring, if necessary, of the
relevant harmonic pollution parameters.
l measurement and H spectrum vignettes
2. Use of a UPS incorporating a harmonic-
suppression filter is the ideal solution for using a
Generator Set/UPS combination with optimised
sizing and to bring upstream total harmonic
distortion down to a completely acceptable value.
Fine network analysis in real time is not required.
However, alarm transfer and storage are
recommended. If necessary, network
parameters (voltage, current, etc.) can be
measured for analysis after the fault.
Safety and
replacement source
GS
Non-priority
feeders
Safety Priority
feeders
Source
E88698
E88697
Figure 35.

42
Summary
5.3. Summary
functions production set replacement safety set parallel- comments
set connected sets*
generator overload protection
overloads b b v b v (1) (1) for Production GS allow for:
- one hour overload
- one hour overload every 12 hours
Note: disabling of thermal memory may be requested
short-circuits b b v b v Magnetic setting at 1.5 ln
insulation fault protection
fire ground protection b b v b v Use in case of TN-S grounding system
ground fault protection v v v v For uncoupling and placing the GS out of operation if fault
restricted differential
protection of people b b b b Protection, if necessary, of the RCD type (Zero Sequence)
network monitoring
current unbalance v v v (2) v (2) Safety GS: the Generator Set must operate whatever
current unbalance
Production and/or Replacement GS: same problem as with
supply by transformers
overcurrent v (3) v (3) v v (3) (3) to be used to perform load shedding
voltage unbalance v v v v
overvoltage and b (4) b (4) v b v (4) (4) use Protection only if risk of breaking equipment /or loss
undervoltage of safety is greater in the event of overvoltage /
frequency b (4) b (4) v b v (4) undervoltage than in the event of breaking
reverse active power ns ns ns v If the GS operates as a motor, there is a risk of:
- deterioration of the diesel set
- placing all sources out of operation (by overload)
harmonic measurement v v v In particular, if non-linear loads are great during operation
on GS (>50 %)
For example Replacement GS with high power UPS
(computer centre)
b Important or compulsory
v Recommended
ns Not significant
* In case of two choices, choose that for the parallel-connected generator set category.

43
Additional technical
informations
Applications
E89629
6.1.Characteristics tables of circuit breakers 44
Compact NS and Masterpact
6.2. Control units characteristics
STR and Micrologic A, H and P 52
6.3. Communication characteristics
for Compact NS and Masterpact 71

44
(1) 2P in 3P case for type N only
(2) specific trip units are available for operational
voltages > 525 V
(3) operational voltage y 500 V.
Compact circuit breakers
number of poles
control manual toggle
direct or extended rotary handle
electric
connections fixed front connection
rear connection
plug-in (on base) front connection
rear connection
withdrawable (on chassis) front connection
rear connection
electrical characteristics as per IEC 60947-2 and EN 60947-2
rated current (A) In 40 °C
65 °C
rated insulation voltage (V) Ui
rated impulse withstand voltage kV) Uimp
rated operational voltage (V) Ue AC 50/60 Hz
DC
type of circuit breaker
ultimate breaking capacity (kA rms) lcu AC 50/60 Hz 220/240 V
380/415 V
440 V
500 V
525 V
660/690 V
DC 250 V (1P)
500 V (2P in series)
service breaking capacity lcs % Icu
suitability for isolation
utilisation category
durability (C-O cycles) mechanical
electrical 440 V In/2
In
electrical characteristics as per NEMA AB1
breaking capacity (kA) 240 V
480 V
600 V
electrical characteristics as per UL508
480 V
600 V
protection
trip units
overload protection long time Ir (In x …)
short-circuit protection short time lsd (Ir x …)
instantaneous Ii (In x …)
earth-fault protection lg (In x …)
zone selective interlocking ZSI
add-on earth-leakage protection add-on Vigi module
combination with Vigirex relay
current measurements
additional measurement, indication and control auxiliaries
indication contacts
MX shunt and MN undervoltage releases
voltage-presence indicator
current-transformer module and ammeter module
insulation-monitoring module
remote communication by bus
device-status indication
device remote operation
transmission of settings
indication and identification of protection devices and alarms
transmission of measured current values
installation
accessories terminal extensions and spreaders
terminal shields and interphase barriers
escutcheons
dimensions (mm) W x H x D fixed, front connections 2-3P / 4P
weight (kg) fixed, front connections 3P / 4P
source changeover system (see section on source changeover systems)
manual, remote-operated and automatic source changeover systems
045345si
Compact NS250H.
Compact NS630L.
048286si
6.1. Characteristics tables
of circuit breakers
Compact NS up to 630 A

45
NS125E NS100 NS160 NS250 NS400 NS630
3, 4 2(1), 3, 4 2(1), 3, 4 2(1), 3, 4 3, 4 3, 4
b b b b b b
- b b b b b
- b b b b b
b b b b b b
b b b b b b
- b b b b b
- b b b b b
- b b b b b
- b b b b b
125 100 160 250 400 630
- 100 150 220 320 500
750 750 750 750 750 750
8 8 8 8 8 8
500 690 690 690 690 690
- 500 500 500 500 500
E N H L N H L N H L N H L N H L
25 85 100 150 85 100 150 85 100 150 85 100 150 85 100 150
16/10 25 70 150 36 70 150 36 70 150 45 70 150 45 70 150
10 25 65 130 35 65 130 35 65 130 42 65 130 42 65 130
6 18 50 100 30 50 70 30 50 70 30 50 100 30 50 70
- 18 35 100 22 35 50 22 35 50 22 35 100 22 35 50
- 8 10 75 8 10 20 8 10 20 10(2) 20(2) 75(2) 10(2) 20(2) 35(2)
50 85 100 50 85 100 50 85 100 - 85 - - 85 -
50 85 100 50 85 100 50 85 100 - 85 - - 85 -
50% 100% 100% 100% 100% 100%(3)
b b b b b b
A A A A A A
10 000 50 000 40 000 20 000 15 000 15 000
6 000 50 000 40 000 20 000 12 000 8 000
6 000 30 000 20 000 10 000 6 000 4 000
5 85 100 200 85 100 200 85 100 200 85 100 200 85 100 200
5 25 65 130 35 65 130 35 65 130 42 65 130 42 65 130
- 10 35 50 20 35 50 20 35 50 20 35 50 20 35 50
- 85 85 - 85 85 - 85 85 - 85 85 - 85 85 -
- 25 65 - 35 65 - 35 65 - 42 65 - 42 65 -
- 10 10 - 10 10 - 18 18 - 18 18 - 30 30 -
non interchangeable TM (thermal-magnetic) STR22 (electronic) STR23 (electronic) STR53 (electronic)
12.5… 125 (A) b b b b
- - b b b
- b b b b
- - - - b
- - - - b
b b b b b
b b b b b
- - - - b
b b b
b b b
- b b
- b b
- b b
- b b b b
- b b b b
- - - - b
- - - - b
- - - - b
b b b
b b b
b b b
105 x 161 x 86 105 x 161 x 86 / 140 x 161 x 86 140 x 255 x 110 / 185 x 255 x 110
1.7 / 2.3 1.6 to 1.9 / 2.1 to 2.3 6.0 / 7.8
- b b

46
045151si045178si
Compact NS800H.
Compact NS2000H.
of circuit breakers
(1) 65°C with vertical connections. See the temperature
derating tables for other types of connections.
Compact NS
from 630 up to 3200 A
Compact circuit breakers
number of poles
control manual toggle
direct or extended rotary handle
electric
connections fixed front connection
rear connection
withdrawable (on chassis) front connection
rear connection
electrical characteristics as per IEC 60947-2 and EN 60947-2
rated current (A) In 50 °C
65 °C (1)
rated insulation voltage (V) Ui
rated impulse withstand voltage (kV) Uimp
rated operational voltage (V) Ue AC 50/60 Hz
DC
ultimate breaking capacity (kA rms) lcu AC 50/60 Hz 220/240 V
380/415 V
440 V
500/525 V
660/690 V
DC 250 V
500 V
service breaking capacity (kA rms) lcs Value or % Icu
short-time withstand current (kA rms) lcw 0.5 s
V AC 50/60 Hz 1 s
suitability for isolation
utilisation category
durability (C-O cycles) mechanical
electrical 440 V In/2
In
690 V In/2
In
pollution degree
electrical characteristics as per Nema AB1
breaking capacity at 60 Hz (kA) 240 V
480 V
600 V
protection and measurements
interchangeable control units
overload protection long time Ir (In x …)
short-circuit protection short time Isd (Ir x …)
instantaneous Ii (In x …)
earth-fault protection lg (In x …)
residual earth-leakage protection I∆∆∆∆∆n
zone selective interlocking ZSI
protection of the fourth pole
current measurements
additional indication and control auxiliaries
indication contacts
voltage releases MX shunt release
MN undervoltage release
remote communication by bus
device-status indication
device remote operation
transmission of settings
indication and identification of protection devices and alarms
transmission of measured current values
installation
accessories terminal extensions and spreaders
terminal shields and interphase barriers
escutcheons
dimensions fixed devices, front connections (mm) 3P
H x W x D 4P
weight fixed devices, front connections (kg) 3P
4P
source changeover system (see section on source changeover systems)
manual, remote-operated and automatic source changeover systems

47
NS630b NS800 NS1000 NS1250 NS1600 NS1600b NS2000 NS2500 NS3200
3, 4 3, 4 3, 4
b b b
b b -
b b -
N H L N H N H
b b b b b b b
b b b b b - -
b b b b b - -
b b b b b - -
630 800 1000 1250 1600 1600 2000 2500 3200
630 800 1000 1250 1510 1550 1900 2500 2970
750 750 750
8 8 8
690 690 690
500 500 500
N H L N H N H
50 70 150 50 70 85 125
50 70 150 50 70 70 85
50 65 130 50 65 65 85
40 50 100 40 50 65 -
30 42 25 30 42 65 -
- - - - - - -
- - - - - - -
75% 50% 100% 75% 50% 65 kA 75%
25 25 10 25 25 40 40
17 17 7 17 17 28 28
b b b
B B A B B B B
10000 10000 5000
6000 5000 5000 3000
5000 4000 2000 2000
4000 3000 2000 2000
2000 2000 1000 1000
III III III
N H L N H N H
50 65 125 50 65 - 85 125 -
35 50 100 35 50 - 65 85 -
25 50 - 25 50 - 50 - -
Micrologic 2.0 Micrologic 5.0 Micrologic 2.0 A Micrologic 5.0 A Micrologic 6.0 A Micrologic 7.0 A
b b b b b b
- b - b b b
b b b b b b
- - - - b -
- - - - - b
- - b b b b
b b b b b b
- - b b b b
b b
b b
b b
b b b b b b
b b b b - -
- - b b b b
- - b b b b
- - b b b b
b -
b -
b b
327 x 210 x 147 350 x 420 x 160
327 x 280 x 147 350 x 535 x 160
14 24
18 36
b

48
Masterpact NT06 to NT16
056408si
of circuit breakers
circuit-breaker characteristics as per IEC 60947-2
rated current (A) In at40°C/50°C**
rating of 4th pole (A)
sensor ratings (A)
ultimate breaking capacity (kA rms) Icu 220/415 V
V AC 50/60 Hz 440 V
525 V
690 V
rated service breaking capacity (kA rms) Ics % Icu
rated short-time withstand current (kA rms) Icw 0.5 s
V AC 50/60 Hz 3 s
integrated instantaneous protection (kA peak ±10%)
rated making capacity (kA peak) Icm 220/415 V
V AC 50/60 H 440 V
525 V
690 V
break time (ms)
closing time (ms)
circuit-breaker characteristics as per NEMA AB1
V AC 50/60 Hz 480 V
600 V
switch-disconnector characteristics as per IEC 60947-3
type of switch-disconnector
V AC 50/60 Hz 440 V
500/690 V
rated short-time withstand current (kA rms) Icw 0.5 s
V AC 50/60 Hz 3 s
ultimate breaking capacity (Icu) with external protection relay,
maximum delay 350 ms
installation, connection and maintenance
service life mechanical with maintenance
C/O cycles x 1000 without maintenance
electrical without maintenance 440 V
690 V
motor control (AC3-947-4) 690 V
connection drawout FC
RC
fixed FC
RC
dimensions (mm) drawout 3P
H x W x D 4P
fixed 3P
4P
weight (kg) drawout 3P/4P
(approximate) fixed 3P/4P
* see the current-limiting curve in the "additional characteristics" section
** 50 °C: rear vertical connected. Refer to temperature derating tables
for other connection types.
(1) SELLIM system.
common characteristics
number of poles 3 / 4
rated insulation voltage (V) Ui 1000/1250
impulse withstand voltage (kV) Uimp 12
rated operational voltage (V AC 50/60 Hz) Ue 690
suitability for isolation IEC 60947-2
degree of pollution IEC 60664-1 3

49
NT06 NT08 NT10 NT12 NT16
630 800 1000 1250 1600
630 800 1000 1250 1600
400 400 400 630 800
to 630 to 800 to 1000 to 1250 to 1600
H1 L1* H1
42 150 42
42 130 42
42 100 42
42 25 42
100 % 100 %
42 10 42
20 - 20
- 1(1) -
88 330 88
88 286 88
88 220 88
88 52 88
25 9 25
< 50 < 50
42 150 42
42 100 42
42 25 42
HA HA
75 75
75 75
75 75
42 42
20 20
35 35
25 25 25
12.5 12.5 12.5
6 3 6 (NT16: 3)
3 2 2 (NT16: 1)
3 2 2 (NT16: 1)
b b b
b b b
b b b
b b b
322 x 288 x 280
322 x 358 x 280
301 x 274 x 211
301 x 344 x 211
30/39
14/18
sensor selection
sensor rating (A) 400 630 800 1000 1250 1600
Ir threshold setting (A) 160 to 400 250 to 630 320 to 800 400 to 1000 500 to 1250 640 to 1600

50
Masterpact NW08 à NW63
056409si056410si
of circuit breakers
circuit-breaker characteristics as per IEC 60947-2
rated current (A) In at40°C/50°C**
rating of 4th pole (A)
sensor ratings (A)
ultimate breaking capacity (kA rms) Icu 220/415 V
V AC 50/60 Hz 440 V
525 V
690 V
1150 V
rated service breaking capacity (kA rms) Ics % Icu
rated short-time withstand current (kA rms) Icw 1s
V AC 50/60 Hz 3s
integrated instantaneous protection (kA peak ± 10%)
V AC 50/60 Hz 440 V
525 V
690 V
1150 V
break time (ms)
closing time (ms)
circuit-breaker characteristics as per NEMA AB1
V AC 50/60 Hz 480 V
600 V
switch-disconnector characteristics as per IEC 60947-3
type of switch-disconnector
V AC 50/60 Hz 440 V
500/690 V
1150 V
rated short-time withstand current (kA rms) Icw 1 s
V AC 50/60 Hz 3 s
ultimate breaking capacity (Icu) with external protection relay,
maximum delay 350 ms
installation, connection and maintenance
service life mechanical with maintenance
C/O cycles x 1000 without maintenance
electrical without maintenance 440 V
690 V
1150 V
motor control (AC3-947-4) 690 V
connection drawout FC
RC
fixed FC
RC
dimensions (mm) drawout 3P
H x W x D 4P
fixed 3P
4P
weight (kg) drawout 3P/4P
(approximate) fixed 3P/4P
* see the current-limiting curve in the "additional characteristics" section
** 50°C: rear vertical connected. Refer to temperature derating tables
for other connection types.
(1) except 4000 A.
common characteristics
number of poles 3 / 4
rated insulation voltage (V) Ui 1000/1250
impulse withstand voltage (kV) Uimp 12
rated operational voltage (V AC 50/60 Hz) Ue 690/1150
suitability for isolation IEC 60947-2
degree of pollution IEC 60664-1 4

51
NW08 NW10 NW12 NW16 NW20 NW25 NW32 NW40 NW40b NW50 NW63
800 1000 1250 1600 2000 2500 3200 4000 4000 5000 6300
800 1000 1250 1600 2000 2500 3200 4000 4000 5000 6300
400 400 630 800 1000 1250 1600 2000 2000 2500 3200
to 800 to 1000 to 1250 to 1600 to 2000 to 2500 to 3200 to 4000 to 4000 to 5000 to 6300
N1 H1 H2 L1* H10 H1 H2 H3 L1* H10 H1 H2 H3 H10 H1 H2
42 65 100 150 - 65 100 150 150 - 65 100 150 - 100 150
42 65 100 150 - 65 100 150 150 - 65 100 150 - 100 150
42 65 85 130 - 65 85 130 130 - 65 85 130 - 100 130
42 65 85 100 - 65 85 100 100 - 65 85 100 - 100 100
- - - - 50 - - - - 50 - - - 50 - -
100 % 100 % 100 % 100 %
42 65 85 30 50 65 85 65 30 50 65 85 65 50 100 100
22 36 50 30 50 36 75 65 30 50 65 75 65 50 100 100
without without 190 80 without without 190 150 80 without without 190 150 without without 270
88 143 220 330 - 143 220 330 330 - 143 220 330 - 220 330
88 143 220 330 - 143 220 330 330 - 143 220 330 - 220 330
88 143 187 286 - 143 187 286 286 - 143 187 286 - 220 286
88 143 187 220 - 143 187 220 220 - 143 187 220 - 220 220
- - - - 105 - - - - 105 - - - 105 - -
25 25 25 10 25 25 25 25 10 25 25 25 25 25 25 25
< 70 < 70 < 70 < 80
42 65 100 150 - 65 100 150 150 - 65 100 150 - 100 150
42 65 100 150 - 65 100 150 150 - 65 100 150 - 100 150
42 65 85 100 - 65 85 100 100 - 65 85 100 - 100 100
NA HA HF HA10 HA HF HA10 HA HF HA10 HA
88 105 187 - 105 187 - 121 187 - 187
88 105 187 - 105 187 - 121 187 - 187
88 105 187 - 105 187 - 121 187 - 187
- - - 105 - - 105 - - 105 -
42 50 85 50 50 85 50 55 85 50 85
- 36 50 50 36 75 50 55 75 50 85
42 50 85 50 50 85 50 55 85 50 85
25 20 20 10
12.5 10 10 5
10 10 10 3 - 8 8 2 3 - 5 5 1.25 - 1.5 1.5
10 10 10 3 - 6 6 2 3 - 2.5 2.5 1.25 - 1.5 1.5
- - - - 0.5 - - - - 0.5 - - - 0.5 - -
10 10 10 - - 6 6 6 - - 2.5 2.5 2.5 - - -
b b b b b b b b b b b b b b - -
b b b b b b b b b b b b b b b b
b b b - - b b - - - b (1) b (1) - - - -
b b b - - b b - - - b b - - b b
439 x 441 x 395 479 x 786 x 395
439 x 556 x 395 479 x 1016 x 395
352 x 422x 297 352 x 767x 297
352 x 537x 297 352 x 997x 297
90/120 225/300
60/80 120/160
sensor selection
sensor rating (A) 400 630 800 1000 1250 1600 2000 2500 3200 4000 5000 6300
Ir threshold 160 250 320 400 500 630 800 1000 1250 1600 2000 2500
setting (A) to 400 to 630 to 800 to 1000 to 1250 to 1600 to 2000 to 2500 to 3200 to 4000 to 5000 to 6300

52
Compact NS400 to 630
60 250 400 500 630
STR23SE / STR53UE
STR23SE / STR53UE
MP
STR23SV / STR53SV
Standard protection
with selectivity
Protection of DC
distribution systems
Protection of systems supplied by
generators. Protection of long cables
Protection of systems U > 525 V
Selection of the trip unit depends on the type of distribution system protected and
the operational voltage of the circuit breaker.
Protection for all types of circuits, from 60 to 630 A, is possible with only four trip-
unit catalogue numbers, whatever the circuit-breaker operational voltage:
b U y 525 V: STR23SE or STR53UE
b U > 525 V: STR23SV or STR53SV.
Trip units do not have a predefined rating. The tripping threshold depends on the
circuit breaker rating and the LT (long time) current setting.
For example, for an STR23SE trip unit set to the maximum value, the tripping
threshold is:
v 250 A, when installed on a Compact NS400 250 A
v 630 A, when installed on a Compact NS630.
Inshort
Compact NS400 to 630 circuit
breakers, types N, H and L, 3-pole
and 4-pole, may be equipped with
any of the STR23SE, STR23SV,
STR53UE and STR53SV electronic
trip units.
The STR53UE and STR53SV trip
units offer a wider range of settings
and the STR53UE offers a number
of optional protection, measurement
and communications functions.
For DC applications, the Compact
NS400H and 630H circuit breakers
are equipped with a built-in MP
magnetic trip unit.
E88733E
6.2. Control units
characteristics

53
STR23SE (U y 525 V) and STR23SV (U > 525 V)
electronic trip units
IsdIr
STR 23 SE
Ir
x Io
Io
-
test
+
90
105 %Iralarm
x In
6 1 37
.5
.63
.7
.9
1
.8
.85
.9
.95
1
.88
.93
.98
.8
2
3
4
5 6
7
8
10
Isd
x Ir
t
I0 Ir Im
1
2
3
4
5
1 long-time threshold (overload protection)
2 long-time tripping delay
3 short-time pick-up (short-circuit protection)
4 short-time tripping delay
5 instantaneous pick-up (short-circuit protection)
6 test connector
7 percent load indication.
Protection
The protection functions may be set using the adjustment dials.
Overload protection
Long-time protection with an adjustable threshold and fixed tripping delay:
b Io base setting (6-position dial from 0.5 to 1)
b Ir fine adjustment (8-position dial from 0.8 to 1).
Short-circuit protection
Short-time and instantaneous protection:
b short-time protection with an adjustable pick-up and fixed tripping delay
b instantaneous protection with fixed pick-up.
Protection of the fourth pole
On four-pole circuit breakers, neutral protection is set using a three-position
switch to 4P 3d (neutral unprotected), 4P 3d + N/2 (neutral protection at 0.5 In) or
4P 4d (neutral protection at In).
Indications
A LED on the front indicates the percent load:
b ON - load is > 90 % of Ir setting
b flashing - load is > 105 % of Ir setting.
Test
A mini test kit or a portable test kit may be connected to the test connector on the
front to check circuit-breaker operation after installing the trip unit or accessories.
E88734E88735

54
STR53UE (U y 525 V) and STR53SV (U > 525 V)
electronic trip units
> Ih
> Im
> Ir
µ P
faulttestSTR 53 UE
Io
x In
-
test
+
32 4 5
8 16
16
4
2
0,5
(s) @ 6 Ir
.3 .3
.2
.1
0
.2
.1
0
on I2
t off
.9 .93
.95
.98
1
.88
.85
.8
.8 .9
1
.7
.6
.5
1
4 5
6
8
10
3
2
1.5
4 6
8
10
11
3
2
1.5
.5 .6
.7
.8
1
.4
.3
.2
x Io
Ir Isd
x Ir
Ii
x In
Ig
g
x In
tr tsd
(s)
.4 .4
.3
.2
.1
.3
.2
.1
on I2
t off
tg
(s)
%Ir >Ir >Isd >Ig
A
In I1 I2 I3 IsdIr li
tr
tsd
8 6 79(*) (*)1
t
0 Ir Isd Ii
5
4
3
2
1
6
7
I
1 long-time threshold (overload protection)
2 long-time tripping delay
3 short-time pick-up (short-circuit protection)
4 short-time tripping delay
5 instantaneous pick-up (short-circuit protection)
6 optional earth-fault pick-up
7 optional earth-fault tripping delay
8 test connector
9 battery and lamp test pushbutton.
(*) STR avec l'option "défaut terre".
Earth-fault protection (T) (see the "Options for the STR53UE electronic
trip unit" section on the following pages).
With the earth-fault option (T) on the STR53UE electronic trip unit, an external
neutral sensor can be installed (situation for a three-pole circuit breaker in a
distribution system with a neutral). Available ratings of external neutral
sensors: 150, 250, 400, 630 A.
Protection
The protection functions may be set using the adjustment dials.
Overload protection
Long-time protection with adjustable threshold and tripping delay:
b Io base setting (6-position dial from 0.5 to 1)
b Ir fine adjustment (8-position dial from 0.8 to 1).
Short-time and instantaneous protection:
b short-time protection with adjustable pick-up and tripping delay,
with or without constant I2
t
b instantaneous protection with adjustable pick-up.
Protection of the fourth pole
On four-pole circuit breakers, neutral protection is set using a three-position
switch to 4P 3d (neutral unprotected), 4P 3d + N/2 (neutral protection at 0.5 In) or
4P 4d (neutral protection at In).
Overload LED (% Ir)
A LED on the front indicates the percent load:
b when ON, the load is > 90 % of Ir setting
b when flashing, the load is > 105 % of Ir setting.
E88737E88736
Compact NS400 to 6306.2. Control units
characteristics

55
trip units STR23SE (U y 525V) STR53UE (U y 525V)
STR23SV (U > 525V) STR53SV (U > 525V)
ratings (A) In 20 to 70 ° C (1) 150 250 400 630 150 250 400 630
circuit breaker Compact NS400 N/H/L b b b - b b b -
Compact NS630 N/H/L - - - b - - - b
overload protection (Long time)
current setting Ir = In x … 0.4...1 0.4...1
adjustable, 48 settings adjustable, 48 settings
time delay (s) fixed adjustable
(min.…max.) at 1.5 x Ir 90...180 8...15 34...50 69...100 138...200 277...400
at 6 x Ir 5...7.5 0.4...0.5 1.5...2 3...4 6...8 12...16
at 7.2 Ir 3.2...5.0 0.2...0.74 1...1.4 2...2.8 4...5.5 8.2...11
short-circuit protection (Short time)
pick-up (A) Isd = Ir x … 2...10 1.5...10
accuracy ± 15 % adjustable, 8 settings adjustable, 8 settings
time delay (ms) fixed adjustable, 4 settings + "constant I2t" option
max. resettable time y 40 y 15 y 60 y 140 y 230
max. break time y 60 y 60 y 140 y 230 y 350
short-circuit protection (instantaneous)
pick-up (A) Ii = In x … 11 1.5...11
fixed adjustable, 8 settings
protection of the fourth pole
neutral unprotected 4P 3d no protection no protection
neutral protection at 0.5 In 4P 3d + N/2 0.5 x Ir 0.5 x Ir
neutral protection at In 4P 4d 1 x Ir 1 x Ir
options
indication of fault type - b (standard)
zone selective interlocking ZSI - b (2)
communications COM - b (2)
built-in ammeter I - b (2)
earth-fault protection T - b (2)
(1) If the trip units are used in high-temperature environments, the setting must take into account the thermal limitations of the circuit breaker. The overload
protection setting may not exceed 0.95 at 60° C or 0.9 at 70° C for the Compact NS400, and 0.95 at 50° C, 0.9 at 60° C or 0.85 at 70° C for the Compact NS630.
(2) This option is not available for the STR53SV trip unit.
Fault indications
A LED signals the type of fault:
b overload (long-time protection) or abnormal internal temperature (> Ir)
b short-circuit (short-time protection) or instantaneous (> Isd)
b earth fault (if earth-fault protection option installed) (> Ig)
b microprocessor malfunction:
v both (> Ig) and (> Isd) LEDs ON
v (> Ig) LED ON (if earth-fault protection option (T) installed).
Battery powered. Spare batteries are supplied in an adapter box. The LED
indicating the type of fault goes OFF after approximately ten minutes to conserve
battery power. The information is however stored in memory and the LED can be
turned back ON by pressing the battery/LED test pushbutton. The LED
automatically goes OFF and the memory is cleared when the circuit breaker is
reset.
Test
The test pushbutton tests the battery and the (% Ir), (> Ir), (> Isd) and (> Ig)
LEDs.
Self monitoring
The circuit breaker trips if a microprocessor fault or an abnormal temperature
is detected.
Options
Four options are available:
b earth-fault protection T
b ammeter I
b zone selective interlocking ZSI
b communications option COM.
E88738
Setting example
What is the overload-protection threshold of a
Compact NS400 circuit breaker equipped with
an STR23SE (or STR23SV) trip unit set
to Io = 0.5 and Ir = 0.8 ?
x In
Ir
x Io
.8
.85
.9
.95
1
.88
.93
.98
Io
.5
.63
.7
.9
1
.8
Answer
In x Io x Ir = 400 x 0.5 x 0.8 = 160 A.
The identical trip unit, with identical settings but
installed on a Compact NS630 circuit breaker, will
have an overload-protection threshold of:
630 x 0.5 x 0.8 = 250 A.

56
Options for the STR53UE electronic trip unit
Earth-fault protection (T)
type Residual
pick-up Ig = In x … 0.2 to 1
accuracy ± 15% adjustable, 8 settings
time delay adjustable, 4 settings
"constant I2t" function max. resettable time 60 140 230 350
max. break time y 140 y 230 y 350 y 500
Ammeter (I)
A digital display continuously indicates the current of the phase with the greatest
load. The value of each current (I1, I2, I3, Ineutral) may be successively
displayed by pressing a scroll button.
LEDs indicate the phase for which the current is displayed.
Ammeter display limits:
b minimum current u 0.2 x In. Lower currents are not displayed
b maximum current y 10 x In.
Zone selective interlocking (ZSI)
A number of circuit breakers are interconnected one after another by a pilot wire.
In the event of a short-time or earth fault:
b if a given STR53UE trip unit detects the fault, it informs the upstream circuit
breaker, which applies the set time delay
b if the STR53UE trip unit does not detect the fault, the upstream circuit breaker
trips after its shortest time delay.
In this manner, the fault is cleared rapidly by the nearest circuit breaker.
The thermal stresses on the circuits are minimised and time discrimination is
maintained throughout the installation.
The STR53UE trip unit can handle only the downstream end of a zone selective
interlocking function. Consequently, the ZSI option cannot be implemented
between two Compact NS circuit breakers.
Opto-electronic outputs
Using opto-transistors, these outputs ensure total isolation between the internal
circuits of the trip unit and the circuits wired by the user.
Communications option (COM)
This option transmits data to Digipact distribution monitoring and control modules.
Transmitted data:
b settings
b phase and neutral currents (rms values)
b highest current of the three phases
b overload-condition alarm
b cause of tripping (overload, short-circuit, etc.).
Inshort
Possible combinations:
b I
bT
b I + T
b I + COM
b I + T + COM
b ZSI
b ZSI + I
b ZSI + T
b ZSI + I + T
b ZSI +I + COM
b ZSI + I + T + COM
Compact NS400 to 6306.2. Control units
characteristics

57
MP DC trip units
ImIn
Im(A)
2000
3800
4400 5000
5700
4000
2500
3000
3500
Magnetic trip units for Compact NS400/630 three-pole, type H circuit breakers.
These trip units are specifically designed to protect DC distribution systems.
They are not interchangeable. The circuit breaker and trip unit are supplied
fully assembled.
built-in trip units MP1 MP2 MP3
circuit breaker Compact NS400H b b -
Compact NS630H b b b
short-circuit protection (magnetic)
pick-up (A) Im adjustable adjustable adjustable
800...1600 1250...2500 2000...4000
E88739

58
Micrologic 5.0
.4
.5
.6
.7
.8
.9
.95
.98
1
delay
short time
I itsd
(s)
on I
2
t
.2
.3
.4 .4
.1
.2
.3
.1
0
off
instantaneous
long time
alarmIr
x In
5
2
1
6
.5
1
2
4
8
12
16
20
tr
(s)
@ 6 Ir
24
setting
x Ir
2
2.5
3
4
5
6
8
10
Isd
1.5
x In
test
3
2
4
10
3
6 8
12
15
off
4
Micrologic for Compact
NS630b to 3200
Protection
Protection thresholds and delays are set using the adjustment dials.
Overload protection
True rms long-time protection.
Thermal memory: thermal image before and after tripping.
Setting accuracy may be enhanced by limiting the setting range using a different
long-time rating plug.
Overload protection can be cancelled using a specific LT rating plug "Off".
Short-time (rms) and instantaneous protection.
Selection of I2
t type (ON or OFF) for short-time delay.
Neutral protection
On three-pole circuit breakers, neutral protection is not possible.
On four-pole circuit breakers, neutral protection may be set using a three-
position switch: neutral unprotected (4P 3d), neutral protection at 0.5 In (4P 3d +
N/2) or neutral protection at In (4P 4d).
Indications
Overload indication by alarm LED on the front; the LED goes on when the current
exceeds the long-time trip threshold.
Test
Note.
Micrologic A control units come with a transparent lead-seal cover as standard.
Inshort
Micrologic 2.0 and 5.0 control units
protect power circuits. Micrologic 5.0
offers time discrimination for short-
circuits as well.
E88740
1 long-time threshold and tripping delay
2 overload alarm (LED)
3 short-time pick-up and tripping delay
4 instantaneous pick-up
5 fixing screw for long-time rating plug
6 test connector.
6.2. Control units
characteristics

59
0 I
t
Ir
tr
Isd
Ir
tr
Isd
Ii
0 I
t
tsd
E88741E88742
protection Micrologic 2.0
long time
current setting (A) Ir = In x … 0.4 0.5 0.6 0.7 0.8 0.9 0.95 0.98 1
tripping between 1.05 and 1.20 Ir other ranges or disable by changing rating plug
time delay (s) accuracy 0 to -30% tr at 1.5 x Ir 12.5 25 50 100 200 300 400 500 600
accuracy 0 to -20% tr at 6 x Ir 0.5 1 2 4 8 12 16 20 24
accuracy 0 to -20% tr at 7.2 x Ir 0.34 0.69 1.38 2.7 5.5 8.3 11 13.8 16.6
thermal memory 20 minutes before and after tripping
instantaneous
pick-up (A) Isd = Ir x … 1.5 2 2.5 3 4 5 6 8 10
accuracy ± 10%
time delay fixed: 20 ms
protection Micrologic 5.0
long time
tripping between 1.05 and 1.20 Ir other ranges or disable by changing rating plug
time delay (s) accuracy 0 to -30% tr at 1.5 x Ir 12.5 25 50 100 200 300 400 500 600
accuracy 0 to -20% tr at 6 x Ir 0.5 1 2 4 8 12 16 20 24
accuracy 0 to -20% tr at 7.2 x Ir 0.34 0.69 1.38 2.7 5.5 8.3 11 13.8 16.6
short time
pick-up (A) Isd = Ir x … 1.5 2 2.5 3 4 5 6 8 10
accuracy ± 10%
time delay (ms) at 10 x Ir settings I2t Off 0 0.1 0.2 0.3 0.4
I2t On 0.1 0.2 0.3 0.4
tsd (max resettable time) 20 80 140 230 350
tsd (max break time) 80 140 200 320 500
instantaneous
pick-up (A) Ii = In x … 2 3 4 6 8 10 12 15 off
accuracy ± 10%

60
Micrologic A "ammeter"
Protection settings .................................................
Protection thresholds and delays are set using the adjustment dials.
The selected values are momentarily displayed in amperes and in seconds.
Overload protection
True rms long-time protection.
Thermal memory: thermal image before and after tripping.
Setting accuracy may be enhanced by limiting the setting range using a different
long-time rating plug.
The long-time rating plug "OFF" enables to cancel the overload protection.
Short-time (rms) and instantaneous protection.
Selection of I2
t type (ON or OFF) for short-time delay.
Earth fault protection
Residual or source ground return.
Selection of I2
t type (ON or OFF) for delay.
Residual earth-leakage protection (Vigi).
Operation without an external power supply.
d Protected against nuisance tripping.
k DC-component withstand class A up to 10 A.
Neutral protection
On three-pole circuit breakers, neutral protection is not possible.
position switch: neutral unprotected (4P 3t), neutral protection at 0.5 In (4P 3t + N/
2), neutral protection at In (4P 4t).
Zone selective interlocking (ZSI)
A ZSI terminal block may be used to interconnect a number of control units to
provide total discrimination for short-time and earth-fault protection, without a
delay before tripping.
"Ammeter" measurements .................................... menu
Micrologic A control units measure the true rms value of currents.
A digital LCD screen continuously displays the most heavily loaded phase (Imax)
or displays the I1
, I2
, I3
, IN
, Ig
, I∆n
, stored-current (maximeter) and setting values by
successively pressing the navigation button.
The optional external power supply makes it possible to display currents < 20% In.
Communication option
In conjunction with the COM communication option, the control unit transmits the
following:
b setting values
b all "ammeter" measurements
b tripping causes
b maximeter reset.
Note.
Micrologic A control units come with a transparent lead-seal cover as standard.
Micrologic A control units protect
power circuits.
They also offer measurements,
display, communication and current
maximeters. Version 6 provides
earth-fault protection, version 7
provides earth-leakage protection.
E88743
Micrologic 6.0 A
40
100%
%
menu
.4
.5
.6
.7
.8
.9
.95
.98
1
delay
short time
I itsd
(s)
on I
2
t
.2
.3
.4 .4
.1
.2
.3
.1
0
off
instantaneous
long time
alarmIr
x In
13
10
ground fault
B
C
D
E
F
G
H
J
Ig tg
(s)
on I
2
t
.2
.3
.4 .4
.1
.2
.3
.1
0
off
A
.5
1
2
4
8
12
16
20
tr
(s)
@ 6 Ir
24
setting
x Ir
2
2.5
3
4
5
6
8
10
Isd
1.5
x In
test
6
3
5
71
2
12
11
9
8
2
4
10
3
6 8
12
15
off
4
kA
s
Ir=Ii=
tr=
Isd=
Ig=
tsd=
Dt=
tg=
IDn=
MAX
1 long-time current setting and tripping delay
2 overload signal (LED)
5 earth-leakage or earth-fault pick-up and tripping delay
6 earth-leakage or earth-fault test button
7 long-time rating plug screw
8 test connector
9 lamp test, reset and battery test
10 indication of tripping cause
11 digital display
12 three-phase bargraph and ammeter
13 navigation buttons.
Inshort
6.2. Control units
characteristics

61
protections Micrologic 2.0 A
long time
tripping between 1.05 and 1.20 x Ir other ranges or disable by changing rating plug
time delay (s) accuracy: 0 to -30 % tr at 1.5 x Ir 12.5 25 50 100 200 300 400 500 600
accuracy: 0 to -20 % tr at 6 x Ir 0.5 1 2 4 8 12 16 20 24
accuracy: 0 to -20 % tr at 7.2 x Ir 0.34(1) 0.69 1.38 2.7 5.5 8.3 11 13.8 16.6
(1) with tsd = 0.4 off, tr = 0.5 s.
instantaneous
pick-up (A) Isd = Ir x … 1.5 2 2.5 3 4 5 6 8 10
accuracy: ±10 %
time delay fixed: 20 ms
ammeter Micrologic 2.0 A
menu
continuous current measurements
measurements from 20 to 200 % of In I1 I2 I3 IN
accuracy: 1.5% (including sensors) no auxiliary source (where I > 20 % In)
maximeters I1 max I2 max I3 max IN max
protection Micrologic 5.0 / 6.0 / 7.0 A
long time Micrologic 5.0 / 6.0 / 7.0 A
tripping between 1.05 and 1.20 x Ir other ranges or disable by changing rating plug
time delay (s) accuracy: 0 to -30 % tr at 1.5 x Ir 12.5 25 50 100 200 300 400 500 600
accuracy: 0 to -20 % tr at 6 x Ir 0.5 1 2 4 8 12 16 20 24
accuracy: 0 to -20 % tr at 7.2 x Ir 0.34 0.69 1.38 2.7 5.5 8.3 11 13.8 16.6
short time
pick-up (A) Isd = Ir x … 1.5 2 2.5 3 4 5 6 8 10
accuracy: ±10 %
time delay (ms) at 10 Ir settings I2t Off 0 0.1 0.2 0.3 0.4
I2t On 0.1 0.2 0.3 0.4
tsd (max resettable time) 20 80 140 230 350
tsd (max break time) 80 140 200 320 500
instantaneous
pick-up (A) Ii = In x … 2 3 4 6 8 10 12 15 off
accuracy: ±10 %
earth fault Micrologic 6.0 A
pick up (A) Ig = In x … A B C D E F G H J
accuracy: ±10 % In y 400 A 0.3 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
400 A < In y 1200 A 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
In > 1200 A 500 640 720 800 880 960 1040 1120 1200
time delay (ms) settings I2t Off 0 0.1 0.2 0.3 0.4
at In or 1200 A I2t On 0.1 0.2 0.3 0.4
tg (max resettable time) 20 80 140 230 350
tg (max break time) 80 140 200 320 500
residual earth leakage (Vigi) Micrologic 7.0 A
sensitivity (A) I∆∆∆∆∆n 0.5 1 2 3 5 7 10 20 30
accuracy: 0 to -20 %
time delay (ms.) settings 60 140 230 350 800
t∆∆∆∆∆n (max resettable time) 80 140 230 350 800
t∆∆∆∆∆n (max break time) 140 200 320 500 1000
ammeter Micrologic 5.0 / 6.0 / 7.0 A
menu
continuous current measurements
measurements from 20 to 200 % of In I1 I2 I3 IN Ig I∆n
accuracy: 1.5 % (including sensors) no auxiliary source (where I > 20 % In)
maximeters I1 max I2 max I3 max IN max Ig max I∆n max
0 I
t
IDn
tDn
0 I
t
Ig
tg
I
2
t off
I
2
t on
E88744E88745
0 I
t
Ir
tr
Isd
Ir
tr
Isd
Ii
0 I
t
tsd
E88741E88742
Note:
All current-based protection functions require no auxiliary source.
The test / reset button resets maximeters, clears the tripping indication and tests
the battery.

62
Micrologic P "power"
Protection settings ........................................ + menu
The adjustable protection functions are identical to those of Micrologic A
(overloads, short-circuits, earth-fault and earth-leakage protection).
Double setting
Within the range determined by the adjustment dial, fine adjustment of thresholds
(to within one ampere) and time delays (to within one second) is possible on the
keypad or remotely using the COM option.
IDMTL setting
Coordination with fuse-type or medium-voltage protection systems is optimised
by adjusting the slope of the overload-protection curve. This setting also ensures
better operation of this protection function with certain loads.
Neutral protection
On three-pole circuit breakers, neutral protection may be set using the keypad or
remotely using the COM option, to one of four positions: neutral unprotected (4P
3t), neutral protection at 0.5 In (4P 3t + N/2), neutral protection at In (4P 4t) and
neutral protection at 2 In (4P 3t + 2N). Neutral protection at 2 In is used when the
neutral conductor is twice the size of the phase conductors (major load
imbalance, high level of third order harmonics).
position switch or the keypad: neutral unprotected (4P 3t), neutral protection at
0.5 In (4P 3t + N/2), neutral protection at In (4P 4t). Neutral protection produces
no effect if the long-time curve is set to one of the IDMTL protection settings.
Programmable alarms and other protection ........
Depending on the thresholds and time delays set using the keypad or remotely
using the COM option, the Micrologic P control unit monitors currents and
voltage, power, frequency and the phase sequence. Each threshold overrun is
signalled remotely via the COM option. Each threshold overrun may be combined
with tripping (protection) or an indication carried out by an optional M2C or M6C
programmable contact (alarm), or both (protection and alarm).
Load shedding and reconnection.........................
Load shedding and reconnection parameters may be set according to the power
or the current flowing through the circuit breaker. Load shedding is carried out by
a supervisor via the COM option or by an M2C or M6C programmable contact.
Measurements ........................................................
The Micrologic P control unit calculates in real time all the electrical values (V, A,
W, VAR, VA, Wh, VARh, VAh, Hz), power factors and crest factors.
The Micrologic P control unit also calculates demand current and demand power
over an adjustable time period. Each measurement is associated with a minimeter
and a maximeter.
In the event of tripping on a fault, the interrupted current is stored. The optional
external power supply makes it possible to display the value with the circuit
breaker open or not supplied.
Note:
Micrologic P control units come with a non-transparent lead-seal cover as
standard.
Micrologic 6.0 P
.4
.5
.6
.7
.8
.9
.95
.98
1
delay
short time
I itsd
(s)
on I
2
t
.2
.3
.4 .4
.1
.2
.3
.1
0
off
instantaneous
long time
alarmIr
x In
ground fault
B
C
D
E
FG
H
J
Ig tg
(s)
on I
2
t
.2
.3
.4 .4
.1
.2
.3
.1
0
off
A
setting
x Ir
2
2.5
3
4
5
6
8
10
Isd
1.5
.5
1
2
4
8
12
16
20
tr
(s)
@ 6 Ir
24
x In
test
2
4
10
3
6 8
12
15
off
I(A)
Trip
20 kA
0.4s
Off
24s
2000A
13
5
10
15
16
6
1
8
2
7
43
9
11
12 14
Micrologic P control units include all the
functions offered by Micrologic A.
In addition, they measure voltages and
calculate power and energy values.
They also offer new protection functions
based on currents, voltages, frequency
and power reinforce load protection.
E88746
1 long-time current setting and tripping delay
2 overload signal (LED)
5 earth-leakage or earth-fault pick-up and tripping delay
6 earth-leakage or earth-fault test button
7 long-time rating plug screw
8 test connector
9 lamp + battery test and indications reset
10 indication of tripping cause
11 high-resolution screen
12 measurement display
13 maintenance indicators
14 protection settings
15 navigation buttons
16 hole for settings lockout pin on cover.
Inshort
6.2. Control units
characteristics

63
Histories and maintenance indicators ..................
The last ten trips and alarms are recorded in two separate history files.
Maintenance indications (contact wear, operation cycles, etc.) are recorded for
local access.
Option de signalisation par contact programmables
The M2C (two contacts) and M6C (six contacts) auxiliary contacts may be used
to signal threshold overruns or status changes. They can be programmed using
the keypad on the Micrologic P control unit or remotely using the COM option.
Communication option (COM)
The communication option may be used to:
b remotely read and set parameters for the protection functions
b transmit all the calculated indicators and measurements
b signal the causes of tripping and alarms
b consult the history files and the maintenance-indicator register.
An event log and a maintenance register, stored in control-unit memory but not
available locally, may be accessed in addition via the COM option.

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