Discover what our ABB experts presented at the 2013 mining technology roadshow

1. - David Stonebridge Roadshow October 2013
L.V/ MV Switchgear Safety Hazards
Passive & Active Arc Fault protection
© ABB Group
November 4, 2013 | Slide 1

2. LV/MV Switchgear
Safety Hazards

The new Work Health & Safety (WH&S) acts and codes of
practices makes the person conducting the business or
undertaking (PCBU) & the worker responsible for
maintaining safety in the work place.

They need to be aware of the Safety Hazards in LV/MV
Switchgear and develop a safe systems of work.
Type tested
switchgear


2 trained
electricians
© ABB Group
Month DD, Year
What are the primary Safety Hazards
| Slide 2
Contact with live parts

Arc Flash & Fire

3. LV/MV Switchgear- Safety Hazards
IEC 61439 ( AS/NZS 3439) IEC62271-200

The primary focus of the Standard has been to provide
protection again electric shock. To protect against touching
“Live Parts”
While the standards provides guidance to the purchaser it
does not recommend the safety requirements. For example
arguable the most important safety requirement for
switchgear is internal arc fault containment (IAC), this is not
a mandatory requirement of the standard.


© ABB Group
Month DD, Year
| Slide 3
AS/NZS 3000:2007 states for all LV switchboards with a
current rating greater than 800A Arc Fault protection shall
be provided Clause 2.5.5 looks at the reduction of
internal arcing faults by improving the design of the
switchgear with high degrees of insulation and separation .
The Australian WH&S regulations & codes of practices and
the US NFPA 70E regulations basically are trending
towards “No Live Work“ under any circumstance

4. LV/MV Switchgear
Safety Hazards- Summary

Ageing switchgear is a major risk of an arcing faults



Sluggish old breakers. Deterioration of insulation
Open door operation. No arc fault containment
The US regulations provide the calculation model to
determine the incident energy & arc flash boundaries .

PPE does not provide 100% protection against an arc

Arcing faults don’t depend on making contact with “Live
Parts”

People take too many risks especially on LV switchgear.



© ABB Group
Month DD, Year
| Slide 4
Arc Flash is all about Current not Volts
The duration of the arc is critical – milliseconds
To maintain Safety you must protect the worker from
“Arcing Faults” and contact with “Live Parts”

5. Arc Fault Behaviour
Summary

There are controlled Arcs & then there are Fault Arcs

High impedance Arcing Faults

In-Line Arcing Faults

Travelling Arcs

Arcing time is critical to be safe the arc needs to be
extinguished in 35 milliseconds.
The Arc Pressure is established in 5 to 10 milliseconds

Conventional S/C protection is too slow to protect people
and will not detect against an In-Line arcing fault
Knowing how an Arc will behave, switchgear can be
designed to minimise the risk of arc burn incidents
© ABB Group
Month DD, Year
| Slide 5

6. Safety Strategy
US Regulations- IEEE1584 & NFPA 70E

The calculated Arc Flash Data is used to develop
strategies to minimise burn injuries. The strategies include:

The specific rating of PPE (personal protective
equipment)

Working de-energised

Applying arc-resistant switchgear - Internal Arc Fault
Containment (IAC)
(Refer IEEE 1584 2002 Clause 4.1 Analysis Process)
IEE1584 stresses that PPE is the last line of defence


| Slide 6
Poor Visibility

© ABB Group
Month DD, Year
Heat Stress
Limited Body & Hand Movement

7. LV Switchgear – Arc Flash Requirements
IEEE1584 & NFPA 70E
Non IAC LV switchgear
IAC LV Switchgear

The US regulations do not require the use of Arc rated PPE
on IAC switchgear when carrying out normal operations.

Refer NFPA 70E-12 Hazard Risk Category 130C)(15)(a)

8. LV/MV Switchgear
Safety Strategy Summary

TOP Safety Strategy (Technical - Organisational - Personal)
Risk
Personal
Action
Eliminate the risk
Keep distance
to the risk
Contain the risk
Personal protection
against the risk
PPE ( Cat 3 & above ) is the last option
© BU 3101 Low Voltage Systems
November 4, 2013 | Slide 9

9. Arc Fault Protection
IAC Internal Arc Fault Testing


1996 LV IEC 61641 IAC
guidelines

2001 US ANSI IEE C37 IAC
guidelines

2002 LV AS/NZS 3439 IAC
guidelines

2003 MV IEC 26771-200 IAC
guidelines

| Slide 10
1974 LV AS1136 included IAC
guidelines and MV IEC 298 App
AA

© ABB Group
Month DD, Year
1960’s Testing to BS4070 &
Phela guidelines
2013 LV proposed adopting IEC

10. Internal Arc Fault Testing
Summary


| Slide 11
Testing on the load side of the outgoing functional SCPD
only can only be regarded as a limited test. The arc fault
energy is limited by the SCPD and the tests are limited –
What if the arc is initiated on the line side of the SCPD or
on the busbars and incomer ? To protect worker the
complete switchgear should be IAC tested.

© ABB Group
Month DD, Year
The IAC tests procedures are only guidelines. The
purchaser needs to specify what tests are required
ABB has carried out over 400 tests on LV switchgear alone
including many tests which are not shown in the IAC
guidelines in order to provide the additional information for
a customer arc flash risk assessment .

11. Active Arc Fault Protection Options
1. Short-circuit
protection on the LV switchboard
incoming supply.
AS/NZS 3000:2007 clause 2.5.5.3 looks at limiting the
damage to a switchboard due to an internal arcing.
2. Arc detection Systems
AS/NZS 3000:2007 clause 2.5.5.3 also look at arc fault
protection using arc detectors and warn of the problems of
extraneous light sources and discrimination.
3. Arc Detectors in conjunction with an Ultra Fast
Earthing Switch (UFES)
The NFPA 70E-12 Hazard Risk Category 130C)(15)(a)
says for non IAC LV MCC’s up to 65kA where the arc
duration is 30ms Arc Rated PPE is not required to carry
out normal operations

12. Active Arc Protection Devices
Arc Monitors


TVOC-2 Monitor mounted on a
compartment door can be
used to check to see what
sensor tripped and at what
time

| Slide 13
A trip signal is sent to the
breaker (Q1) in less than 2.5
milliseconds

© ABB Group
Month DD, Year
The Arc in compartment A1 is
detected by sensor D and
transferred by optical fibre to
the TVOC-2 Monitor (F11) .
Monitor up to 10 detectors 2
extension modules can be
added allowing up to 30
detectors

13. Active Arc Protection Devices
Arc Monitors Plus UFES


The earthing device short
circuits the bus eliminating
the arc voltage,
extinguishing the arc in
less than 5 milliseconds

| Slide 14
The electronic arc detection
system initiates the
operation of a high speed
earthing switch(UFES).

© ABB Group
Month DD, Year
The intense light associated
with an arc is detected by an
arc detector (QRU)
The Incoming breaker(CB)
trips on instantaneous
overcurrent finally clearing of
the fault.

14. Arc Fault Protection
Safety by Design

Active protection devices, in comparison to passive
protection, are more susceptible to failure owing to the
additional electromechanical and electronic devices

The proven way is to prevent the fault arcs from occurring
in the first place, eliminate the need to work live and then in
the unlikely event of an internal arc contain the arc to that
compartment
Safety by Design
• Withdrawable Design.
• All operations behind closed
doors
• Internal Arc Fault
Containment