abb passive & active arc fault protection by david stonebridge
DESCRIPTION
Discover what our ABB experts presented at the 2013 mining technology roadshowTRANSCRIPT
© 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