Typical scheme structure of North American gas filling cabinet

North American standard inflatable cabinet

Rated voltage: 5/15/27/38kV

Rated current: 1200/2000/3000A

Rated short-time withstand current: 2 seconds 31.5/40kA

Peak withstand current: 82/104kA

38kV BIL lightning impulse withstand voltage 150kV

Power frequency withstand voltage 80kV

IEEE C37.20.9 Gas Insulated Switchgear

IEEE C37.20.7 North American switchgear internal arc fault test standard

IEEE C37.09 AC Circuit Breaker

IEEE C37.20.4 Isolation Switch Standard

IEEE Std 693 Seismic Rating Standard

Relevant IEC standards

IEC 62271-200, LSC2B and AFLR

IEC 62271-1 General Technical Requirements for Medium Voltage Switchgear IEC 62271-100 Medium Voltage Circuit Breakers

IEC 62271-102 Medium voltage isolating switches and grounding switches

IEC 60529, Protection level IP3X IP4X optional

CSA C22.2 No 31-2018 Canadian Standard

A typical one-time solution includes a three position switch+circuit breaker, current transformer, bus side voltage transformer (with/without isolation switch), cable side voltage transformer (with/without isolation switch), and bus current transformer.

The 3000A 40kA incoming cabinet is the most complex, and the one-time solution is as follows

Dual gas box structure, with one gas box for busbar and isolation switch, and one gas box for circuit breaker and current transformer. The maximum current of a single tube in the IEEE 386 standard conduit of a North American inflatable cabinet is 900A. Therefore, for a current of 3000A, it is necessary to connect 4 outgoing cables to the conduit for each phase, which means connecting 4 1000kcmil cables for each phase.

The current transformer is built-in in the gas box, which can be a through type or an epoxy pillar type. The voltage transformer is connected or disconnected through a three position switch, and then connected by a plug-in head, making it easy to replace the fuse inside the voltage transformer.

For bus voltage transformers, the same scheme is used.

The three position switch position viewing system is equipped with a digital camera. According to IEEE C37.20.9 standard, the switch cabinet must have a visible isolation fracture or a device that can observe the status of the isolation switch, such as a camera. The camera should be detachable and equipped with a normally closed cover plate. The camera has a fault free time of more than 150000 hours.

The remote operation and monitoring system, voltage monitoring system, operation, monitoring, and viewing device status are all accessed from the front, which is also a common requirement for North American switchgear installation and maintenance.

The busbar connector is used for connecting the main busbar between switchgear cabinets. The busbar connection sleeve is specified on the flange surface, and the fully solid sealing insulation is achieved by compressing silicone rubber. The connector has a grounding coating in the middle and is connected to the cabinet through a grounding wire.

The cable conduit for the incoming and outgoing lines of North American gas insulated switchgear should use cable terminations (American standard conduit) that comply with the IEEE Std 386-1995 standard.

The internal arc fault level is IEEE C37.20.7 standard Type 2B, and the instrument room door is opened during the internal arc fault test.