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...

 CONSERVATOR:  This is mounted on top of the oil tank. This should have oil two third of its volume and the remaining filled with air. The conservator is used to accommodate the expanded volume of the transformer oil when ever the oil gets heated up owing to loading of the transformer. Also when the oil cools down, the oil from the conservator will flow into the transformer tank. The oil level in the conservator varies depending upon the temperature of the oil on various load conditions. Whenever the oil level reduces in the conservator, atmospheric air from outside will flow through the breather into the conservator and during this process the silica gel will absorb the moisture from the atmospheric air. When the oil level in the conservator rises, the air from the conservator will go to atmosphere through the breather. The breather will have oil to arrest the suspended impurities from the atmospheric air. BREATHER: The breather is connected through a small pipe line to the c...

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 ...

Daily Transformer Inspection Checklist Regular inspection of transformers is essential for their efficient operation and long life. Below is a simple checklist for daily transformer inspection to ensure safety and performance. 1. Check and Record Winding Temperature Monitor the winding temperature and note it down. Abnormal temperature rise may indicate a fault. 2. Check and Record Oil Temperature Measure and record the oil temperature. Overheating of oil can reduce its insulating properties. 3. Check Conservator Tank Oil Level Ensure the oil level in the conservator tank is adequate. A low level may indicate leakage or oil degradation. 4. Check for Oil Leakages Inspect the transformer for any visible oil leaks, which can lead to serious operational issues. 5. Check the Colour of Silica Gel The silica gel in the breather should be pale blue. If it turns pink or white, it needs to be replaced as it has absorbed moisture. 6. Check the Explosion Vent Diaphragm Inspect the explosion vent d...

Causes of Faults in Transformers Transformers are critical components in electrical power systems, and their failure can lead to significant operational disruptions. Various factors contribute to transformer faults, which can be classified based on their origin and impact. Here are some of the most common causes of transformer faults:   1. Winding to Core Faults (Insulation Failure) One of the most common transformer faults occurs due to weakening of insulation between the winding and core. Over time, insulation deteriorates due to aging, overheating, or moisture, leading to short circuits. Key Points: Phase to phase faults inside transformers are rare. Faults may occur at terminals, which are within the transformer protection zone. 2. On Load Tap Changer (OLTC) Faults Power transformers are often equipped with an On Load Tap Changer (OLTC) to regulate voltage levels. This component is prone to mechanical failures, contact wear, or improper operation, leading to transformer faults....