Metal enclosed gas-filled, three-phase medium-voltage switchgear installation

摘要

An encapsulated medium-voltage electrical load switching apparatus has four, three-position rotary switches, supported by pairs of opposing insulated half-shells, two-over-two in parallel alignment within a gas-filled sealed shut shell housing. The housing front and back have dome-shaped protrusions to maintain the seal against fluctuations in gas pressure. Bushings in the floor and ceiling of the housing, aligned with the switch face plane, provide gastight connections between the switches and external cables, enclosed fuses and transformer terminals. Switch control is provided by drives mounted on a plate at the front of the housing exterior which operate actuator arms that extend in a gastight way through the housing front and manipulate selector shafts that connect to set the switches into closed-circuited, open-circuited and grounded positions. Internal conductors establish connection from a cable through a fuse to a transformer terminal when the two upper switches and one of the lower switches are closed-circuited. The disclosed apparatus offers the advantages of low cost, compactness and freedom from maintenance.