INDOOR MEDIUM VOLTAGE SWITCHGEAR - UP TO 24kV. A division of ACTOM Pty Ltd

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1 INDOOR MEDIUM VOLTAGE SWITCHGEAR - UP TO 24kV A division of ACTOM Pty Ltd

2 ACTOM Indoor Medium Voltage Switchgear SBV range of products Prior to 1980, ACTOM s indoor vacuum arc switching is the switchgear business centered lowest of all switching media. around J&P designed AG and Of the four switching media (air, Statter designed ACO ranges of bulk oil, SF6 and vacuum), vacuum oil circuit breaker equipment. has by far the best dielectric recovery properties after short- A requirement for modern tech- circuit interruption. nology switchgear was identified in Vacuum arc switching produces the mid-1970s and in 1976, equip- no adverse environmental proment based on the B-Vac fixed ucts, precluding harmful charac pattern vacuum circuit breaker was teristics either towards people introduced. This equipment how- or materials. ever, was not well accepted on the Freestanding SBV 5 capacitor feeders. Increased safety due to the local market and by 1978 had made absence of oil products in the no significant inroads into the that will result from the unlikely equipment make-up. modern technology business. In event of an internal arc fault 1978 it was realised that a more thus affording inherent operator Tests cost-effective range of draw-out safety. In the case of the dupli- The relevant international and pattern switchgear would have to be cate busbar compartment, national type tests applicable to the introduced. At that time no suitable venting of the lower busbar ACTOM range of switchgear have designs in GEC distribution compartment is effected at the been carried out by accredited switchgear were available and the longitudinal end of the switch testing authorities such as KEMA decision that would lead to the board. and the SABS. Copies of these tests development of ACTOM s SBV Vacuum interrupters are employed are available on request. It can be range of switchgear was taken. as a switching medium. The advan- stated that, among SouthAfrican tages of switching in vacuum are m a n u f a c t u r e r s o f i n d o o r SBV vacuum switchgear considerable. switchgear, ACTOM Switchgear has The SBV equipment was designed They include: been a leader in implementing to meet virtually all known cus- Small interrupter gaps (as low as internal arc testing and actively tomer requirements. It includes 6 mm for 12 kv applications) promotes internal arc testing of single and double busbar units. result in low-energy mecha- switchgear. SBV switchgear has Integral circuit (cable) earthing is nisms, ensuring long mecha- been internally arc tested at 25 ka offered as an option. Busbar nism life. for 200 milliseconds, as per Eskom earthing via the circuit breaker is Low-peak arc voltages result in requirements. also an available option.sbv very low arc energy which in equipment is designed for horizonfor the vacuum interrupter and a turn ensures a long electrical life TYPES OF SWITCHGEAR tal isolation and withdrawal, offering inter alia, the following no-maintenance device. In 1965 advantages: three outdoor, fixed-type Type SBV 3 & SBV 3E vacuum circuit breakers, fitted This version is available in single or Natural venting of the circuit with auto-reclose facilities, were duplicate busbar arrangements. break er compartments is installed on Great Britain s Circuit and busbar earthing via the permitted and, subsequently, Eastern Electricity Board 11kV circuit breaker are available higher continuously rated networks to assess their perforcurrents. options. The operating mechanism mance. Five arduous years of allows for hand charged spring or Pressure relief vents, fitted as a service were insufficient to motor charged spring application. standard to all equipment, are evaluate the contact wear and The mechanism design allows for accommodated at the top of the loss of vacuum integrity, as none the following optional features: circuit breaker panels. The could be detected. second shunt trip facility purpose of the relief vents is to The current chopping level of under voltage (no-volt) trip open and relieve over-pressure facility 2

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4 Medium voltage switchboard undergoing preparations for acceptance testing. including 12 kv including A Rated short circuit capability: up to and including 40 ka for 3 seconds BIL: 95 kv Type SBV4 & SBV4E The SBV4 equipment is available in single busbar configuration only and is of low-profile construction, permitting overall height reduction of the switchgear. Circuit and busbar earthing via the circuit breaker are available options. The operating mechanism allows for hand charged spring or motor charged spring application. The mechanism design allows for the provision of the following optional features: second shunt trip facility under voltage (no-volt) trip facility direct acting (series) trip facility including 12 kv including A Rated short circuit capability: up to and including 31,5 ka for 3 seconds BIL: 95 kv Type SBV5 & SBV5E The SBV 5 circuit breaker was designed for utilisation in the lowprofile SBV4 housings and is interchangeable with the SBV4 circuit breaker and vacuum contactors. Circuit and busbar earthing via the circuit breaker are available options. The operating mechanism is of the magnetic actuator type, using closing and tripping coils with the plunger being held magnetically in the closed or open positions by permanent magnets. The material used for the magnets is neodymium-iron-boron, the field strength of which is almost twice that of samarium cobalt and up to 280 times that of steel. The circuit breaker has been type tested in excess of no-load mechanical operations without discernable component wear. The combination of magnetic actuators with long-life vacuum interrupters has resulted in circuit breaker life that was previously not possible. Further features include a low component count, reliability and minimal maintenance. including 12 kv including A Rated short circuit capability: up to and including 25 ka for 3 seconds BIL: 95 kv Type SBV24 This version is for 22 kv indoor utilisation and is of single busbar configuration. Circuit and busbar earthing via the circuit breaker are available options. The operating mechanism allows for hand charged spring or motor charged spring application. The mechanism design allows for the provision of the following features: second shunt trip facility under voltage (no-volt) trip facility direct acting (series) trip facility. including 24 kv including A Rated short circuit capability: up to and including 25 ka for 3 seconds. BIL: 125 kv Type SBV-C These are fused vacuum contactors m o u n t e d o n w i t h d r a w a b l e Carriages and are extensible on SBV3 and SBV4 switchgear. A manually operated cable dis- charge switch is an available option. Operating mechanisms are electri- cally held or mechanically latched options. Mechanical life of the vacuum contactors is in excess of 3 x 106 operations; electrical endurance in excess of 106 opera- tions. Fused contactors have an advantage over circuit breakers in that the fuses greatly limit the magnitude and duration of short- circuit currents. Where the equip- ment is used in switching of motors, cables can be sized to carry load and starting currents only. Possible fault damage to motors can thus be restricted. (of contactor unit only) including 12 kv including 400 A Rated short circuit capability: 4kA 4

5 Internal arc testing of MV switchgear A major hazard of electrical medium the case of segregated phase they start burning, the assessment voltage installations is the danger of conductors, between one phase criterion may be regarded as having an internal arc fault. The most and earth. All the relevant compart- been met if proof is established that common causes of an internal arc ments must be individually tested the ignition was caused by glowing fault are tools left on the busbars to ensure the integrity of the com- particles rather that hot gases. after the initial installation or during plete switch panel, not just one Highspeed camera pictures should maintenance, and binding wire particular section. For the effects of be produced in evidence. used during commissioning tests, the explosion to be monitored 6 Whether all the earthing connecnot having been removed prior to under actual conditions, two walls, tions are still effective. energising. An internal arc condi- a ceiling and the floor are required It is advisable to record the tests in tion constitutes a potentially to be simulated. As operator safety a high-speed video of up to dangerous situation for the opera- is of prime importance, indicators frames per second in order to tor. are positioned both horizontally and analyse the physical phenomena. vertically in metal racks 300 mm The ever increasing safety needs Internal arc testing requirements from the switchgear being tested. call for switchgear manufacturers to were initiated by the German The above indicators are positioned comply with international and PHELA organisation. A procedure front and sides, facing all the points national standards. for internal arc testing was then where gas is likely to be emitted, developed, resulting in Appendix and positioned in such a way that Internal arc fault testing in A of the IEC standard. hot gas escaping in slant directions accordance with IEC can be monitored. The design of the SBV range of Arc duration of 0,1 second is vacuum switchgear commenced in considered sufficient to prove the These indicators consist of metal Even at that early stage the operation of pressure relief devices. frames covered with black cretonne importance of internal arc fault Internal arc faults are normally cloth of 150 g/m². venting and safety was recognised. simulated by a thin copper wire of The design of the horizontal approximately 0,5 mm in diameter To successfully complete the withdrawable switchgear was stretched across two or more internal arc tests the equipment chosen so as to incorporate top p h a s e s i n s i d e t h e v a r i o u s needs to meet the criteria set out in venting. Following ACTOM s switchgear compartments, and in IEC Appendix A as repeated success at KEMA in 1997 when the below: SBV4 was successfully internal arc 1 Whether correctly secured doors, fault tested for 20 ka at 12 kv for 0,1 covers, etc, do not open. second, more onerous tests were 2 Whether parts (of the metal- carried out at the SABS high power enclosed switchgear and control laboratory. The tests provided for gear), which may cause a hazard, do side access in addition to front not fly off - including large parts or access and the internal arc was for those with sharp edges, e. g. 25 ka with a duration of 0,2 sec. inspection windows, pressure relief flaps, cover plates, etc, made of Internal arc classification in metal or plastic. accordance with IEC Whether arcing does not cause The introduction of IEC holes to develop in the accessible and internal arc classification (IAC) external parts of the enclosure as a lead to ACTOM enhancing its result of burning or other effects. proven SBV range of circuit break- 4 Whether the indicators arranged ers (i.e. SBVE). The SBVE range is vertically do not ignite. Indicators presently classified as BFL-AR 25 ka that ignite as a result of paint or 0.2 sec in accordance with IEC stickers burning are excluded from Development and this assessment. testing with SBVE is ongoing, 5 Whether the indicators arranged SBV3 double busbar switchpanel after internal arc test. horizontally do not ignite. Should ensuring safer and more reliable products. 5

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8 2 Magnet Road Knights 1413 P O Box Knights 1413 Tel: +27 (0) Fax: +27 (0) sg.info@actom.co.za