OPERATOR AND PUBLIC SAFETY REVISITED: THE APPLICATION OF IEC 62271-200

1. OPERATOR AND PUBLIC SAFETY REVISITED: THE APPLICATION OF IEC 62271-200/202 WITH SPECIFIC FOCUS ON INTERNAL ARC TESTING OF METAL-ENCLOSED SWITCHGEAR AND CONTROLGEAR (PAPER 0256) R A Kelly (Eskom – SOUTH AFRICA) B Meyer (Previously Eskom – SOUTH AFRICA)

2. Introduction Purpose – to share Eskom’s philosophy behind the recent developments in the re-testing of metal-enclosed switchgear products to meet the safety requirements of the South African Occupational Health and Safety Act with particular respect to internal arc compliance utilizing the recently published IEC 62271-200 and IEC 62271-202 as reference. Operator and public safety has been put under the spotlight in Eskom following various catastrophic failures of metal-enclosed switchgear.

3. Introduction Users in South Africa have a duty, in terms of safety legislation (most notably the Occupational Health and Safety Act 85 of 1993 [1]) to their employees and the public to provide an acceptably safe environment and to take reasonable measures to mitigate against possible dangers. With developments in both technology and knowledge, it is now possible to specify and use switchgear that is tested not only to withstand the effects of, but to safely ‘vent’ the emissions generated by an internal (arc) fault.

4. History of MV S/G in SA EDI For many years – primary insulation/interrupting medium was oil Historically maintained on an interval and event-based maintenance schedule Alarming trend – inadequately maintained Maintenance simply not being scheduled pressure on maintenance budgets increasingly difficult to schedule onerous outages required for maintenance In some cases – ‘run-to-failure’ philosophy

5. History of MV S/G in SA EDI The result: gradual deterioration in the insulating and interrupting properties of oil increased probability of mechanism failure increased risk and number of failures with associated injuries / fatalities

6. History of MV S/G in SA EDI As a direct result, numerous switchgear failures have occurred which have been accompanied, in many instances, by serious injuries, and in some more severe cases, fatalities. Issues pertaining to internal arc testing have emerged in the process of addressing the safety concerns around increasing switchgear failure risks.

7. History of MV S/G in SA EDI Prior to the advent of suitable alternatives to oil-filled switchgear (e.g. air/gas-insulated metal-enclosed switchgear), requirements such as internal arc classification could not be seriously considered. IAC only possible with ‘dry-arcs’ can be simulated in laboratory associated with air, SF6 filled switchgear Simply not practical for oil-filled switchgear – damage to surrounding property

8. History of MV S/G in SA EDI “In general, oil-filled switchgear has a proven record of reliability and performance. Failures are rare but, where they occur, the results may be catastrophic. Tanks may rupture, resulting in the ejection of burning oil and gas clouds, causing death or serious injury to persons and major damage to plant and buildings in the vicinity of the failed equipment. Accident experience has shown that failure usually occurs at, or shortly after, operation of the equipment. Thus, the way switchgear is operated, its condition and the circumstances existing in the system at the time of operation, to a large extent, determines whether the equipment will safely perform its duty.” Clause 5, HSE 483/27 – Oil-filled electrical distribution and other switchgear’

9. History of MV S/G in SA EDI

10. Safety – Eskom’s approach Safety is achieved by reducing risk to a tolerable level. ‘freedom from an unacceptable risk’ (IEC 51) Tolerable risk is determined by the search for an optimal balance between the ideal of absolute safety and the demands to be met by a product, process or service, and factors such as benefit to the user, suitability for purpose, cost effectiveness, and conventions of the society concerned. ‘Risk’ is considered to be the combination of the probability of occurrence of a harm and the severity of the harm.

11. Safety – Eskom’s approach It follows that there is a need to continually review the tolerable level of risk – in particular when developments in both technology and knowledge can lead to economically feasible improvements – in order to greatly reduce the risk associated with the use of a product, process or service.

12. Internal arc Arc energy = f (voltage, S/C current, time) Incident energy = f (arc energy, distance) Energy absorbed by person = f (incident energy, PPE)

13. Internal arc Result of inadequate pressure release mechanisms

14. Risk Reduction (IEC 51) It is emphasized that the additional protective devices, personal protective equipment and provision of information to users should not be used as substitutes for design improvements

15. Risk Reduction

16. Risk Reduction Arc flash hazard risk analysis, requiring: ‘arc flash protection’ boundary be established based on the incident energy in order to manage the risk of injury and ensure that personnel have adequate PPE. employees are trained and aware of potential hazards when operating, changing the position of, or working in the proximity of energized electrical equipment.

17. Risk Reduction

18. Risk Reduction If an employee needs to enter a flash boundary to perform work that could possibly cause an arc flash, then appropriate PPE (personal protective equipment) needs to be worn. The type of PPE depends on the amount of energy to which an employee could be exposed.

19. Risk Reduction

20. Risk Reduction For new equipment, through the specification and design of internal arc classified switchgear, where the energy and emissions resulting from and internal arc are suitably vented away from the operator and/or people in the vicinity, the ‘safe’ working distance (flash boundary) can be effectively managed without the need for excessive PPE (category ‘0’) IEC IAC provides a tested level of protection under normal operating conditions not under maintenance conditions not concerned with service continuity

21. Risk Reduction additional ‘supplementary’ measures arc detection, arc eliminators / suppressors, CLDs (e.g. ACRs, NERs), pressure relief devices, remote control, motorised racking devices, transfer of withdrawable parts with front doors closed requires a co-ordinated approach Measures are continually sought to mitigate against internal arc faults caused by known common problems.

22. Specifications for new S/G 1998 – internal arc testing of primary S/G 2002 – specification of IAC secondary switchgear (e.g. RMUs) 2005 – present - Eskom has recently been involved in the development and re-testing of switchgear products to meet the safety requirements of the Occupational Health and Safety Act and industry-aligned requirements utilising the recently published IEC 62271-200 as well as IEC 62271-202 (prev IEC 61330) as reference IAC philosophy revisited

23. Specifications for new S/G IEC 62271-200 caters for two relevant categories of IAC – based on the type of accessibility required by the user. Type A accessibility is restricted to authorised personnel only; and Type B accessibility caters for unrestricted accessibility – including that of the general public. IEC 62271-202 defines accessibility Type A and B as follows: Type A accessibility – protection of operators (authorised personnel) performing normal operations Type B accessibility – protection of public – unrestricted accessibility (doors closed)

24. Specifications for new S/G Primary switchgear: AR-BFL (IEC 62271-200) 25kA 0,2 s (12kV & 24kV) transfer of withdrawable parts with front doors closed venting upwards, room dimensions specified pressure relief devices in switchroom supplementary measures: arc detection system (2/2) remote switching (separate room for control panels) motorised racking devices with remote control Secondary switchgear: AB IEC 62271-202 (AF-BFLR (IEC 61330)) 20kA 0,5 s (12kV) 16kA 0,5 s (24kV) venting upwards – 2 m duct

25. Specifications for new S/G Recently tested secondary switchgear

26. Conclusions Ever increasing focus on human safety, service delivery and cost reduction. Eskom and other major utilities have responded to the changing risk profile in the light of developments in both technology and knowledge The introduction of mandatory type testing for internal arc classified (IAC) switchgear as detailed in IEC 62271-200 and IEC 62271-202, together with the implementation of safe working practices (such as those detailed in NFPA 70E), has greatly enhanced Eskom’s ability to specify acceptable equipment that significantly improves both operator and public safety.