What are the non-electricity protections?

The types of non-electricity protection include: 1. Gas protection; 2. Light gas protection; 3. Heavy gas protection; 4. Pressure protection; 5. Temperature and oil level protection; 6. Cooler full stop protection. .

Types of non-electricity protection

1. Gas protection

Gas protection is the main protection against short-circuit faults and abnormalities in the windings in the transformer tank. Its working principle is: when there is an internal fault in the transformer, a short-circuit current that is often accompanied by an arc is generated at the fault point, causing local overheating in the tank and decomposing the transformer oil, producing gas (gas), which in turn causes fuel injection, impulsive relays, and gas protection. action.

Gas protection is divided into two types: light gas protection and heavy gas protection. Light gas protection acts on signals, heavy gas protection acts on action tripping, and heavy gas protection acts on cut-off transformers.

2. Light gas protection

The light gas protection relay consists of an open cup, a dry reed contact, etc. During operation, the relay is filled with transformer oil, the open cup is immersed in the oil and is in a floating position, and the dry reed contact is disconnected. When a minor fault or abnormality occurs inside the transformer, the fault point is locally overheated, causing part of the oil to expand. The gas in the oil is expelled, forming bubbles, which enter the gas relay, causing the oil level to drop, and the open cup to rotate, causing the dry reed contact to Closed, giving a signal.

3. Heavy gas protection

The heavy gas protection relay is composed of a baffle, a spring and a dry reed contact.

When a serious fault occurs in the transformer oil tank, the large fault current and arc cause the transformer oil to decompose in large quantities and produce a large amount of gas, causing the transformer to inject oil. The oil flow impacts the baffle, drives the magnet and makes the dry reed The contacts are closed, acting to cut off the transformer.

It should be pointed out that heavy gas protection is the main protection for internal faults in the oil tank, and it can reflect various faults inside the transformer. When an inter-turn short circuit occurs in a small number of windings of the transformer, although the fault current at the fault point is large, the differential current generated in the differential protection may not be large, and the differential protection may refuse to operate. At this time, rely on heavy gas protection to remove the fault.

4. Pressure protection

Pressure protection is also the main protection for internal faults in the transformer tank. Its principle of action is basically the same as that of heavy gas protection, but it responds to the pressure of the transformer oil.

Pressure relay, also known as pressure switch, is composed of spring and contacts. Place it on the upper part of the oil tank of the transformer body.

When there is an internal fault in the transformer, the temperature rises, the oil expansion pressure increases, and the spring action drives the relay moving contact, closing the contact and cutting off the transformer.

5. Temperature and oil level protection

When the temperature of the transformer rises, the temperature protection action sends an alarm signal.

The oil level is a protection that reflects the abnormal oil level in the tank. During operation, it will act and send out an alarm signal when the oil level drops due to oil leakage from the transformer or other reasons.

6. Cooler full stop protection

In order to improve transmission capacity, large transformers are equipped with various cooling systems. During operation, if the cooling system is completely stopped, the temperature of the transformer will increase. If not handled immediately, the insulation of the transformer winding may be damaged.

Cooler full stop protection is activated when the cooler is completely stopped during transformer operation. After its action, an alarm signal should be issued immediately, and the transformer should be cut off after a long delay.

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