Buchholz relay positioned between conservator tank and tank cover. If some fault occur in transformer (short circuit between winding layers or turns, deformation on insulation materials etc.), various gases are released. These gases rise up due to their density and accumulate in the buchholz relay. And switches in the buchholz relay is actived due to this accumulation.

There are two 5 Amps electrical contacts into the relay. Any signalization and monitoring system can be controlled by electrical contacts in buchholz relay.

It generally used for hermetically sealed oil immersed transformers and can be used for transformer with conservator tank in case of customer request. PRD (Pressure Relief Device) protects  transformers tank against the high pressure. In case of over pressure situation, the valve opened and oil discharged to out of tank. 

If this device is not used or if its defective:

Tank pressure may increase,
The over pressure situation causes an increase in temperature,
The over temperature situation causes an increase in load losses/copper losses,
The temperature increase, shortens life of oil and other insulation materials,
In Datsan, We use pressure relief device as a standard protection device on all hermetically sealed transformers and as an optional on our transformers with conservator tank.

DMCR by another name its called RIS is used with hermetically type transformers as a protection and monitoring device. It used to monitoring or measuring parameters below:

Oil level,
Gas content,
Tank pressure,
Oil temperature.
DMCR/RIS equipped with electrical contacts below:

Tank pressure,
Oil temperature,
Oil level.

Oil level indicators are used to see and/or inspect the oil level in transformer tank (hermetically sealed) or in conservator tank. In many cases we used contact type oil level indicator as an option which equipped with electrical contacts.