Switchgear high voltage

Frequently switchgear is used for motor control, particularly for large high-voltage motors. Switchgear (Fig, 29-6) must be used for motors... 

Common specifications for high voltage switchgear and 3427/1991 controlgear standards BSEN 60694/1997 -... 

Specification for control transformers for switchgear and controlgear for voltages not exceeding lOOOV a.c. Specification for high voltage busbars and busbar connections... 

The procedure will be the same as that discussed for switchgear assemblies (Section 14.3.3). The test voltage may be applied for one minute as shown in Tables 32.1 (A) or (B) for series I and Table 32.2 for series II voltage systems. Any disruptive discharge or insulation breakdown during the application of high voltage will be considered to be dielectric failure. 

Lightning and switching surges that damage motors are related to high-voltage motors. The insulation level of motors is below that of many other types of apparatus such as transformers, switchgear, cables,... 

BS 5311, High voltage alternating current circuit breaker BS 6867, Code of Practice for maintenance of electrical switchgear for voltages above 36 kV BS 158, Insulating oil for transformers and switchgear BS 5622, Insulation co-ordination... 

Switchgear is available up to at least 400 kV, whereas motor control centres are only designed for voltages up to approximately 15 kV because this is the normal limit for high voltage motors. 

The following description of integrated motor control systems (IMCS) is based upon Reference 7, for which permission to use the material therein was kindly given by Switchgear and Instrumentation Ltd. The principles described can be used for low and high voltage switchgear that contain plain feeders, interconnectors, incomers and busbar section circuit breakers, in addition to... 

High voltage power fuses. Document No. AD 36-661, pages 1 to 8, May 1968. Westinghouse Electric Corporation, Switchgear Division. East Pittsburgh, Pennsylvania, USA. 

In order to restrict the detection of earth faults to those within the stator winding, and those from the stator terminals to the switchgear current transformers, a sensitive relay (64) is used. Three current transformers are used in the stator live lines and one in the star to NER connection. All four current transformers are connected in parallel such that any unbalance in the currents due to an internal fault is detected by the restricted earth fault relay (64). A sensitive high impedance relay is used to achieve an instantaneous response. However, if a high impedance is connected across a current transformer it is possible that very high voltages will appear across the impedance. This is due to the action of... 

The main purpose of preparing a specification for an item of equipment is to ensure that the purchaser, who may also become the owner, obtains the equipment required, rather than what the supplier or manufacturer thinks the purchaser should have. In many situations the difference in perception of the requirements may be small and insignificant. However, for complicated equipment such as high-voltage switchgear and generation systems the differences may be very significant. 

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