Motor & generator protective relays example settings

1. Motor protection example
Assume you have a motor rated 500 HP, .95 power factor & 90 % efficiency energized from a 4.16 Kv
source, using a microprocessor motor protection relay, provide the typical settings.
The full load current can be taken from the motor nameplate as well as the service factor. The motor
full load current can be calculated from the following: I = 500 (.746)/1.732 (4.16)(.85)(.9) =60 amps
Motor and Line Data Functions
Function Description Adjustment / Display Range Setting Increments Setting
Motor Nameplate FLA 1 – 2000A, adjustable between
50-100% of Max Amp Rating.
FLA must be programmed Upper limit of range automatically adjusts 1 60
for relay to function downward as Service factor is increased.
Motor Nameplate 1.00 - 1.30 SF .05 1
Overload Class During Start NEMA / UL Class 5 – 20 5 Class 20
Overload Class During Run NEMA / UL Class 5 – 30 5 Class 10
Overload Reset 0 = Manual,1 = Auto,2 = Disabled Overload 1 1
kV Voltage Input (nominal line, Medium Voltage) .60 – 15kV .01 4.16
Line Frequency 50 or 60 Hz 60
Acceleration Time 0-300 seconds [0=Disabled] 1 30
Current Imbalance Trip % 0.1 - 30% of FLA [0=Disabled] 1(%) 15
Current Imbalance Trip Delay 1 - 20 seconds 1 (Second) 5
Over Current Trip % 0,.50 – 300% of FLA [0=Disabled] 1 (%) 200
Over Current Trip Delay 1 - 20 seconds 1 8
Under Current % 0, 10 – 90% of FLA [0=Disabled] 1 (%) 35
Under Current Trip Delay 1 - 60 seconds 1 15
Stall Detection Trip Level 0.100 – 600% of FLA [0=Disabled] 5 (%) 600
Stall Detection Trip Delay 1 - 10 seconds 1 4
Peak Current Trip % 0.800 – 1400% [0=Disabled] 10(%) 1000 (%)
Peak Current Trip Delay 0..01 - .5 seconds .01 .05
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2. Ground Fault Current Trip Value 0.5 – 90% of CT Value [0=Disabled] 1 (%) 50
Ground Fault Current Trip Delay 1 – 60 seconds 1 5
Voltage Protection Settings
Voltage Imbalance Trip % 0.1 – 30% [0=Disabled] 1 (%) 20
Voltage Imbalance Trip Delay 1 – 20 seconds 1 10
Over Voltage Trip % 0.1 – 10% [0=Disabled] 1 (%) 5
Over Voltage Trip Delay 1 – 20 seconds 1 10
Under Voltage Trip on Start % 0.1 – 20% [0=Disabled] 1 (%) 20
UV Trip on Start Delay 1 – 180 seconds 1 20
Under Voltage Trip on Run % 0.1 – 20% [0=Disabled] 1 (%) 20
UV Trip Delay during Run 1 – 20 seconds 1 10
Phase and Frequency Protection Settings
Phase Rotation Trip 0.1 or 2 0=Disabled, 1=ABC, 2=ACB] 1 2
Phase Rotation Trip Delay 1 – 20 seconds 1 2
Phase Loss Trip and Delay 0.1-20 Seconds [0= Disabled] 1 5
Over Frequency Trip Limit 0.1 – 10Hz [0=Disabled] 1 1
Over Frequency Trip Delay 1 – 20 seconds 1 5
Under Frequency Trip Limit 0.1 – 10Hz [0=Disabled] 1 1
Under Frequency Trip Delay 1 – 20 seconds 1 5
Motor KW Trip 0-2.0 = Disabled,1 = Over KW Trip,2 = Under KW Trip 1 0
Motor KW Trip Point 20 – 100% of full load KW (disabled) 1% 20(%)
Motor KW Trip Delay Time 1 – 999 minutes (disabled) 1 1
Power Factor Trip Range 0.1 – 3 [0=Disabled, 1=lag, 2=lead, 3= lead/lag] 1 2
Power Factor Trip Point .01 – 1 .01 .10
Power Factor Trip Delay Time 1 – 20 seconds 1 10
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3. Power Factor Current Direction 0 - 1, [0=Normal, 1= Reversed] 1 1
Lockout / Inhibit Settings
Coast Down (Back Spin) Lockout Timer 0 = Disabled, or 1 - 60 minutes 1 minute 1
Maximum Starts per Hour 0 = Disabled, or 1 – 10 starts 1 5
Minimum Time Between Starts Inhibit 0 = Disabled, or 1 - 60 minutes 1 minute 12
Note: NEMA Class trip curves are based on a common tripping point of 600% of motor Full Load
Amps (FLA). Curves vary by the amount of time before the unit trips. As an example, a Class 20 curve
will trip in 20 seconds at 600% of FLA. Another example, Class 10 will trip in 10 seconds at 600% of
FLA.
PT Value:1-200 (: 1) 1:1 = direct voltage input, 2-200: 1 = kV Voltage Input 1 40 (4160/104) V
CT Value: 5-2000 (:5) 5 60
Number of Turns through CT: 1 – 5 (in 1 increments) 1
Generator protection example
Ratings of generators:
Rated output (eg. 1,120 MVA), Maximum output (1230 MVA), Rated rotation speed (300 rpm), Power
factor (0.9), Number of poles (2), Terminal voltage (27), Rated Armature current (23949), Maximum
Armature current (26302), Short-circuit ratio (> or = 0.5), Hydrogen gas pressure (0.52 Mpa G),
Insulation type (F), Temperature rise class (B), Cooling method (Stator: direct water), Efficiency
(99 %), Hydrogen consumption (12 m3/day).
Functional Specifications of generator protective relay
NOMINAL SYSTEM FREQUENCY SETTING RANGE.............................................50 or 60 Hz
RATED PRIMARY INPUT CURRENT OF PHASE AND NEUTRAL CTS .........1 - 9999A in 1A steps
RATED PRIMARY SYSTEM PHASE-TO-PHASE VOLTAGE OF PTS......2 – 655 kV in .0.1 kV steps
RATED PT SECONDARY LINE-TO-LINE VOLTAGE ...............................50 – 125 V in 1 V steps
LOW SET OVERCURRENT ELEMENT
Characteristic: .......................................................................................Definite time or inverse
Pickup: ...........................................................................................1.0 – 2.5 pu of rated generator current
Time delay: ...........................................................................................0.05 – 30.0 seconds (at 5pu Igen)
HIGH SET OVERCURRENT ELEMENT
Characteristic: .......................................................................................Definite time
Pickup: ............................................................................................1.0 – 9.9pu of rated generator current
Time delay: ...........................................................................................0.05 – 3.0 seconds (at 5pu Igen)
CURRENT UNBALANCE ELEMENT
Maximum negative sequence current rating;.................................0.05 – 0.5pu of rated generator current
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4. Time multiplier of I2 t curve ...................................................................5 – 80 seconds
Cooling time to rated.............................................................................10 – 1800 seconds
Alarm level pickup.................................................................................0.03 – 0.5pu generator current
Alarm level time delay...........................................................................1 – 100 seconds
REVERSE POWER ELEMENT PICKUP ......................................0.02 to 0.2pu rated generator current
Time delay ...........................................................................................1 – 100 seconds
LOSS OF FIELD ELEMENT
Mho circle size ..........................................................................50 – 300% of rated generator impedance
Mho offset .................................................................................5 – 50% of rated generator impedance
Time delay ............................................................................................0.2 – 60 seconds
Integration time .....................................................................................0 – 10 seconds
VOLTAGE ELEMENTS
Characteristic ........................................................................................Over, Under or Over+Under
Pick-up level.......................................................................................1 – 50% change from rated voltage
Time delay ............................................................................................0.1 – 60.0 seconds
FREQUENCY ELEMENTS
Characteristic ........................................................................................Over, Under or Over+Under
Pick-up level..........................................................................................0.05 – 9.99Hz from nominal
Time delay ............................................................................................0.1 – 60.0 seconds
THERMAL IMAGE ELEMENT
Trip level ...............................................................................................Fixed at 110% rated
Thermal time constant of alternator ......................................................1 – 400 minutes
Pre-alarm level......................................................................................50 – 110% of rated
UNDERPOWER ELEMENT PICKUP LEVEL ..........................................................0.05 – 1.00 of
rated power output
Time delay ............................................................................................0.1 – 60.0 seconds
UNDERIMPEDANCE ELEMENTS
Pickup level...........................................................................................01 – 1.0 pu rated impedance
Time delay ............................................................................................0.02 – 9.99 seconds
FIRST LEVEL OVEREXCITATION ELEMENT
Characteristic ........................................................................................Inverse
Pickup level...........................................................................................1.0 - 2.0 pu
Time multiplier.......................................................................................0.5 – 5.0
SECOND LEVEL OVEREXCITATION ELEMENT
Characteristic ........................................................................................Definite time
Pickup level...........................................................................................1.0 - 2.0 pu
Time multiplier.......................................................................................0.1 – 60.0 seconds
95% STATOR GROUND FAULT ELEMENTS
Pickup level.....................................................................................5 – 99% Rated zero sequence voltage
Time delay ............................................................................................0.05 – 99.0 seconds
100% STATOR GROUND FAULT ELEMENT
3rd Harmonic Pickup level ..............................................................1 – 30% Rated zero sequence voltage
Time delay ............................................................................................0.05 – 99.0 seconds
Typical Settings
IEEE No. Function Typical Settings and Remarks
24 Overexcitation PU: 1.1*VNOM/60; TD: 0.3; reset TD: 5 alarm P.U.: 1.18*VNOM/60
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5. alarm delay: 2.5s
25 Synchronism Check Max Slip: 6RPM; Max phase angle error: 10° Max VMAG error:
2.5% VNOM
32 Reverse Power (one stage) PU: turbine 1% of rated; 15 s . PU: Reciprocating engine:
10% of rated; 5 s
32-1 Reverse Power (non-electrical, trip supervision) PU: same as 32; 3 s
40 Loss-of-field (VAR Flow approach) Level 1 PU: 60% VA rating; Delay: 0.2s; Level 2
PU: 100% VA rating: 0.1s
46 Negative Sequence overcurrent I2 PU: 10% Irated; K=10
49 Stator Temperature (RTD) Lower: 95°C; upper: 105°C
50/87 Differential via flux summation Cts PU:10% INOM or less if 1A relay may be used
50/27 IE Inadvertent Energization Overcurrent with 27, 81 50: 0.5A (10% INOM) 27: 85%
Supervision VNOM (81: Similar)
51N Stator Ground Over- current (Low, Med Z Gnd, PU: 10% INOM; curve: EI; TD: 4. Inst:
Phase CT Residual) none. Higher PU required to coordinate
with load. No higher than 25% INOM.
50/51N Stator Ground Over- current (Low, Med Z Gnd, P.U.: 10% INOM; Curve EI**, TD4; Inst
Neutral CT or Flux Summation CT) 100% INOM. Higher PU if required to
coordinate with load. No higher than
25% INOM.
51GN, 51N Stator Ground Over- current (High Z Gnd) PU: 10% IFAULT at HV Term.; Curve:
VI***; TD:4.
51VC Voltage Controlled overcurrent PU: 50% INOM; Curve: VI***; TD: 4.
Control voltage: 80%VNOM.
51VR Voltage Restrained overcurrent PU: 175% INOM; Curve: VI***; TD: 4. Zero
Restraint Voltage: 100% VNOM L-L
59N, 27-3N, 59P Ground Overvoltage 59N: 5% VNEU during HV terminal fault; 27-3N:
25% V3rd during normal operation; TD: 10s 59P:
80% VNOM
67IE Directional O/C for Inadvertent Energization PU: 75-100% INOM GEN; Definite Time (0.1-
0.25 sec.) ; Inst: 200% INOM GEN
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6. 81 Over/under frequency For Generator protection: 57, 62Hz, 0.5s; For
Island detection condition: 59, 61Hz, 0.1s
87G Generator Phase Differential Fixed: 0.4A; or Variable: Min P.U.: 0.1 * Tap;
Tap: INOM; Slope: 15%
87N Generator Ground Variable: Min P.U.: 0.1 times tap; Slope 15%;
Differential Time delay: 0.1s; choose low tap
67N: current polarization; time: 0.25A; Curve:
VI***; TD: 2; Instantaneous: disconnect
87UD 13 Unit Differential Min PU: 0.35*Tap; Tap: INOM; Slope 30%
**: EI: extremely inverse.
***: VI: very inverse.
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