CSS — 25.8 kV solid insulated compact substation with 500 kVA transformer

Description

CSS (Compact Secondary Substation) combines a vacuum circuit breaker, load break switches and a step-down transformer in one enclosure. The substation is designed for underground cable lines of the 25.8 kV class, in the base version with a 500 kVA transformer. The enclosure diameter depends on the transformer rating. Typical use is supplying consumers of 22.9 kV cable networks in dense urban areas, where small dimensions and switching and transformation in one unit are needed. For a network company this is one delivery instead of separate switchgear, transformer and substation building.

The switching part contains no oil or gas. The arc is extinguished by vacuum interrupters embedded in epoxy bushings, and the main circuits are insulated with hydrophobic cycloaliphatic epoxy resin HCEP. The material resists surface tracking, ultraviolet radiation and vandalism and keeps its insulating properties in polluted and coastal areas and in harsh climates. Solid insulation removes the need to maintain the main circuit. The vacuum interrupter extinguishes the arc in a closed volume, so the enclosure holds no medium that has to be topped up, dried or checked for leaks.

The circuit breaker is driven by a permanent magnet actuator PMA, and the load break switches have a spring toggle mechanism. The simple mechanism with minimal moving parts needs no regular maintenance, so installation and operating costs are lower. According to the manufacturer's table, the rated current of the circuit breaker is 200 A, of the load break switches 630 A. Short-time withstand current is 10 kA for the circuit breaker and 12.5 kA for the load break switches, the short-circuit breaking current of the circuit breaker is 12.5 kA. Power frequency test voltage is 60 kV, lightning impulse 125 kV for the main circuit and 150 kV for the earthing circuit. Operating temperature is from −30 to +70 °C.

CSS is equipped with the microprocessor controller ETMFC303, which performs measurement, monitoring, event recording and communication with the dispatch level. Type tests of the substation were carried out at KERI to IEC 255-5, IEEE C62.41, IEEE C37.90 and IEC 60255-21-2. They cover electromagnetic compatibility and vibration resistance of the control system. The controller measurement and communication functions allow the substation to join the cable network distribution automation system.

Technical specifications

Customs codes

Codes are for reference: the final code is determined at declaration for the specific model.

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