What type of relay is a Buchholz relay?

Buchholz relay is a type of oil and gas actuated protection relay universally used on all oil immersed transformers having rating more than 500 kVA. Buchholz relay is not provided in relays having rating below 500 kVA from the point of view of economic considerations.

What is the purpose of a Buchholz relay?

The Buchholz relay purpose is to give the protection to a transformer from the different faults happening in the transformer like the Short circuit, inter-turn, core, incipient, etc. This relay will sense these faults and shuts the alarm circuit.

Is Buchholz relay is an overcurrent relay?

Definition: The Buchholz relay protects the transformer from internal faults. It is the gas actuated relay. The Buchholz relay is placed between the main tank and the conservator. Such type of relay is used in the transformer having the rating higher than 500KVA.

What are the limitation of Buchholz relay?

Only fault below the oil level are detected. Mercury switch setting should be very accurate, otherwise even for vibration, there can be a false operation. The relay is of slow operating type, which is unsatisfactory.

Why Buchholz relay is connected between tank and conservator?

The generation of gases depend on intensity the of fault. Gas bubbles tend to flow in upward direction towards conservator and hence they are collected in the buchholz relay which is placed on the pipe connecting the transformer tank and conservator.

Why mercury is used in Buchholz relay?

Gas produced by abnormal conditions in the transformer, collects in the Buchholz relay which lowers the oil level so that the top float gradually comes down and ultimately operates the mercury switch when it reaches a certain level. This surge displaces the lower float operation the mercury switch associated with it.

How do you test a Buchholz relay?

On-site testing of Buchholz Relays

1. Place pump on stable area of ground.
2. Open unit and attach flexible pipe to non-return valve outlet using suitable spanner.
3. Ensure that outlet valve is closed at right angle to ballvalve body.
4. When access clear, connect flexible hose to TEST ballvalve upon Buchholz.

Why Buchholz relay is inclined?

The Buchholz Relay is always inclined at an angle of 5–7 or 3–7 degrees to the horizontal in different designs in order to entrap the gases generated due to various faults or hotspots. If the gasses are not entrapped properly then the Buchholz relay will not operate properly.

What is smart Buchholz relay?

In addition to the standard function of the Buchholz relay, i.e. a mechanical switching mechanism responds to the release of gas, oil surge or complete loss of oil, the sensor technology offers a number of useful functions allowing extended and reliable monitoring of the transformer.