Question

How does a Buchholz relay protect a transformer?

Answer 1

A Buchholz relay is a protective device used in oil-immersed transformers. Its main purpose is to detect faults within the transformer, such as internal short circuits, winding faults, or oil leakage, and to provide an early warning before the fault becomes severe.

Here's how it works to protect a transformer:

1. Location: The Buchholz relay is typically installed in the pipe connecting the conservator tank and the main transformer tank. It is positioned to monitor the flow of transformer oil.
   

1. Detection of gas or oil movement: During normal operation, the transformer oil circulates between the main tank and the conservator tank. If a fault occurs inside the transformer, it can produce gases due to arcing or overheating of components.
   

    - Gas Detection: The Buchholz relay detects these gases. The relay has a float or a chamber that captures the gas produced by the fault. A build-up of gas inside the relay indicates a fault inside the transformer.
    - Oil Movement Detection: If there's a sudden loss of oil due to a severe internal fault (like a ruptured winding), the oil level change will trigger the relay.

1. Warning Signals:
   

    - Minor Faults: If gases are detected but the fault is not too severe, the Buchholz relay sends a warning signal. This alerts the operator to check for potential issues before they escalate.
    - Severe Faults: In case of a more serious fault, like a major internal short circuit or oil loss, the relay triggers a trip signal that disconnects the transformer from the electrical network, preventing further damage.

Summary of Functions:

1. Detects gas from faults like overheating, arcing, or partial discharges.
   

1. Monitors oil movement, indicating leakage or a major fault.
   

1. Provides early warning (minor faults) or trips the transformer (severe faults) to prevent extensive damage.
   

The Buchholz relay is a crucial safety device, especially for large transformers, as it helps detect faults early, reducing the risk of catastrophic failures and extending the transformer’s lifespan.