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...

Procedure for Breakdown test: 1) 3 to 4 litres of oil needs to be let out before collecting the oil sample.  2) oil sample from Transformer before filtration. 3) The gap between the test electrodes must be 2.5mm.  4) The oil can withstand 40kV for a minute if it is having good dielectric strength. Voltage should be gradually increased from zero.  5) At one point Flash will take place and that point is termed as Bread down Voltage In Oil filtration process, the oil passes through three chambers in the oil filter. They are 1.Paper Filter, 2.Heater, 3.Vacuum Chamber Paper Filter removes carbon particles from the oil. Heater & Vacuum Chamber removes moisture content from the oil. Mainly transformer oil is used for insulation purpose.  When the oil contacts with atmospheric air in the conservator, the air moisturize the oil and reduce its dielectric strength.  So, the transformer oil should be filtered once in a year. This process should repeat at least for 6 to ...