Current transformer for HV gas-insulated switching installation - has inbuilt HF capacitor providing shunt path for travelling waves due to switching transients for instrument protection and accuracy

摘要

A current transformer for a gas-insulated HV switching installation has a control HV phase-conductor forming the primary winding and a concentric gas-tight metal encapsulation. The encapsulation comprises an earthed disc (1) sealed to a hollow cylinder (4) with which it is in electrical contact via the four peripheral metal rods (2). The cylinder (4) provides a carrier surface for a number of magnetic ring cores (5) set within the rods (2) and which are wound with the transformer secondary (6) whose output is proportional to the primary current. The carrier (4) is stepped (8) to form a cylindrical HF capacitor of e.g. InF with the ring electrode (9) and dielectric (7) of casting resin. USE/ADVANTAGE - Ensures that HF switching transients causing travelling waves are provided with a shunt path and do not influence the magnetic region of transformer. Current readings are thereby true indication of LF network line current and connected instruments are protected from steep-fronted voltage transients.