© ABB Group

November 4, 2013 | Slide 1

- David Stonebridge Roadshow October 2013

L.V/ MV Switchgear Safety HazardsPassive & Active Arc Fault protection

LV/MV Switchgear

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.

What are the primary Safety Hazards

Contact with live parts

Arc Flash & Fire

Safety Hazards

Month DD, Year | Slide 2

© ABB Group

Type tested

switchgear

2 trained

electricians

LV/MV Switchgear- Safety Hazards

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.

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

IEC 61439 ( AS/NZS 3439) IEC62271-200

Month DD, Year | Slide 3

© ABB Group

LV/MV Switchgear

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.

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”

Safety Hazards- Summary

Month DD, Year | Slide 4

© ABB Group

Arc Fault Behaviour

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

Summary

Month DD, Year | Slide 5

© ABB Group

Safety Strategy

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

Heat Stress

Poor Visibility

Limited Body & Hand Movement

US Regulations- IEEE1584 & NFPA 70E

Month DD, Year | Slide 6

© ABB Group

LV Switchgear – Arc Flash RequirementsIEEE1584 & NFPA 70E

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)

Non IAC LV switchgear IAC LV Switchgear

© BU 3101 Low Voltage Systems

November 4, 2013 | Slide 9

TOP Safety Strategy (Technical - Organisational - Personal)

Risk Personal Action

LV/MV SwitchgearSafety Strategy Summary

Eliminate the risk

Keep distance

to the risk

Contain the risk

Personal protection

against the risk

PPE ( Cat 3 & above ) is the last option

Arc Fault Protection

1960’s Testing to BS4070 &

Phela guidelines

1974 LV AS1136 included IAC

guidelines and MV IEC 298 App

AA

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

2013 LV proposed adopting IEC

IAC Internal Arc Fault Testing

Month DD, Year | Slide 10

© ABB Group

Internal Arc Fault Testing

The IAC tests procedures are only guidelines. The

purchaser needs to specify what tests are required

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 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 .

Summary

Month DD, Year | Slide 11

© ABB Group

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

Active Arc Protection Devices

The Arc in compartment A1 is detected by sensor D and transferred by optical fibre to the TVOC-2 Monitor (F11) .

A trip signal is sent to the breaker (Q1) in less than 2.5 milliseconds

TVOC-2 Monitor mounted on a compartment door can be used to check to see what sensor tripped and at what time

Monitor up to 10 detectors 2 extension modules can be added allowing up to 30 detectors

Arc Monitors

Month DD, Year | Slide 13

© ABB Group

Active Arc Protection Devices

The intense light associated with an arc is detected by an arc detector (QRU)

The electronic arc detection system initiates the operation of a high speed earthing switch(UFES).

The earthing device short circuits the bus eliminating the arc voltage, extinguishing the arc in less than 5 milliseconds

The Incoming breaker(CB) trips on instantaneous overcurrent finally clearing of the fault.

Arc Monitors Plus UFES

Month DD, Year | Slide 14

© ABB Group

Arc Fault ProtectionSafety 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