MV Switchgear has boosted the marketability of its AMV17 and AMV12 brands of air-insulated withdrawable pattern indoor switchgear after successfully completing additional IEC Standards type testing of the AMV17 product incorporating several new state-of-the-art features.
The advanced new features it has introduced in partnership with its international Chinese partner YIHE are the embedded pole design circuit breakers, in place of the formerly used shrouded pole units, and the 31.5kA 1 second rated arc coolers, in place of the arc deflector solution originally type tested at KEMA.
The arc deflectors have been less widely accepted in the marketplace compared to the latest technology arc coolers – primarily due to the compact design of the coolers, which don’t overhang the switchboard perimeter nor obstruct top cable entry.
“Furthermore arc coolers have the advantage of not only reducing the temperature of the hot gases emitted from the switchgear during an internal arc fault, but they also reduce the pressure rise within the switchroom,” said Rhett Kelly, MV Switchgear’s Design & Development Manager.
“Where customers prefer arc venting to the outside of the switchroom, we have the arc ducting solution – type tested in 2021,” he added.
MV Switchgear arranged for the type tests to be carried out in accordance with IEC 62271-200 at the XIHARI laboratory in Jimo City, Qingdao Province, China, under the supervision of TUV Rheinland, an international certification body, in mid-April this year.
The internal arc tests were conducted on two models of embedded pole AMV17 panels, both fitted with arc coolers, namely:
- a 1250A 31.5kA 650mm wide panel, and
- a 2500A 31.5kA 1000mm wide panel.
A series of tests, each for 31.5kA for 1 sec, were done on the cable compartment, the circuit breaker compartment and the busbar compartment to verify an internal arc classification of AFLR 31.5kA 1 sec (i.e. providing a tested level of safety for authorised personnel on all sides of the switchgear – Front, Lateral and Rear).
“In addition to the requirements of the IEC standard, we also fitted internal arc indicators on the inside of the LV compartment door to determine if the internal arc tests in the MV compartments had any effect on it. The outcome was that negligible heat and carbon transfer to the LV compartment took place,” said Johan Jordaan, MV Switchgear’s Technology Development Specialist.
“Also forming part of the round of tests was a temperature rise type test that was done on the 650mm wide panel,” said Rhett.
“This was because we sought to increase the current rating of the 650mm wide switch-panel from 800A to 1250A. Temperature rise tests conducted in YIHE’s plant in 2023 on the embedded pole circuit-breaker and panel combination showed that the lower overall main circuit resistance of the embedded pole resulted in substantially lower thermal losses during operation, resulting in turn in a lower temperature rise of the circuit breaker and thus an opportunity to increase the current rating. The increased current rating therefore had to be verified with a formal temperature rise test at an independent accredited test facility,” he explained.
Advantages of the embedded pole design over shrouded pole circuit breakers include:
- Increased reliability, due mainly to simplified primary circuit design, fewer parts and lower main circuit resistance.
- Increased mechanical strength, due to the more robust structure of the embedded pole.
- Improved insulation technology. The vacuum interrupter is embedded within epoxy resin, so keeping it free from exposure to pollution.
- Reduced maintenance. The embedded design results in greatly simplified maintenance.
“Following the latest successful type tests, we now have a complete test certificate for arc coolers, while the incorporation of embedded pole circuit breakers also represents important technological improvements in the product,“ said Johan, adding that the extended certification applies not only to AMV17, but also to the AMV12 product range.