Question

How does Buchholz work?

Answer 1

The **Buchholz relay** is a protective device used in **oil-immersed transformers** to detect faults inside the transformer. It works based on the principle of detecting gas accumulation and oil flow caused by electrical faults like short circuits, overheating, or internal breakdowns of the transformer. It’s usually installed in the oil pipeline that connects the transformer’s tank to its conservator (a storage tank for oil).

Here’s how it works in simple terms:

### 1. **Gas Accumulation Detection:**
   - When a fault occurs inside the transformer (such as a short circuit or insulation breakdown), it leads to a rise in temperature and pressure.
   - This heating causes the transformer oil to break down and produce gases like hydrogen, methane, or acetylene.
   - The **Buchholz relay** detects these gases. It has a chamber that collects these gases as they rise.
   - If a sufficient amount of gas accumulates, it triggers the relay, indicating a fault inside the transformer.

### 2. **Oil Flow Detection:**
   - If a severe fault occurs, it might cause the oil to flow due to a sudden increase in pressure (for example, from a transformer burst or internal explosion).
   - The **Buchholz relay** is sensitive to this oil movement. It has a float mechanism that detects changes in the oil level.
   - If the oil level drops too much due to a fault, the relay activates and signals that something is wrong inside the transformer.

### 3. **Relay Action:**
   - When the Buchholz relay detects either gas accumulation or oil movement, it triggers an alarm or can directly disconnect the transformer from the circuit (if set up for automatic tripping).
   - This action helps protect the transformer by alerting operators to take action before the fault becomes more severe, such as preventing fire or further damage.

### 4. **Types of Faults Detected:**
   - **Minor faults** like partial discharges or small overheating events may generate gases but not necessarily cause a large oil flow. These can be detected by gas accumulation.
   - **Severe faults**, such as a short circuit or insulation breakdown, may cause oil movement and a larger volume of gas to form.

### Buchholz Relay Components:
   - **Gas Detection Chamber**: For gas accumulation.
   - **Float Mechanism**: Detects oil level changes.
   - **Relay Contacts**: To signal alarms or initiate disconnection.
  
In summary, the Buchholz relay works by monitoring gas buildup and oil movement in a transformer to detect faults early and protect the equipment from severe damage.