FM Techie

  Buchholtz Relay – A Quick Overview What is a Buchholtz Relay? The Buchholtz relay, also known as a gas relay or sudden pressure relay, is a protective device used in oil filled transformers. It is mounted in the pipeline between the conservator oil tank and the main transformer tank. This relay helps in detecting incipient faults and prevents severe damage by triggering alarms and circuit breaker mechanisms. Working Principle of Buchholtz Relay The relay functions using two distinct detection modes: 1. Slow Gas Accumulation Detection Over time, gas is generated due to insulating oil decomposition caused by slight overloading or minor faults. This gas accumulates at the top of the relay, pushing the oil level down. A float switch is triggered, activating an alarm signal, which may also indicate slow oil leaks. 2. Rapid Gas Accumulation Detection (Arc Faults) If an internal fault occurs, gas production increases rapidly, and oil flows quickly into the conservator. A vane switch, lo...

Current Transformers a. A current transformer is a step down instrument for measuring the high value current in L.T /H.T/ E.H.T lines b. It has one or two windings or a bus bar or a heavy line conductor surmounted by a core having large number of thin wires. c. In a C.T the number of turns is inversely proportional to the current and it is connected in series in the line d. C.T is used for metering, recording and relay circuits for different requirements. e .C.T must have its secondary always closed through relays/short circuited and no fuse should be used. However the fuses can be used in shunt circuits while in service. f. Never open a secondary circuit of a C.T which may have high potential due to high impedance and endanger to personnel operating. g. Polarity is important in connecting a C.T in the circuit h. In calibrating a C.T’s impedance burden the configuration of different coil connection in series or in parallel is to be kept in mind. For safety purposes one of the secondary...