Protection of transformer

Protection of Power Transformer

BUCHHOLTZ RELAY: - It is used for protection of oil filled transformer from
incipient faults below oil level. It is installed between tank and conservator. In this relay two mercury contacts are provided. . Each float is filled with the mercury switch; leads of a switch are connected to a terminal box for tripping.

PRESSURE RELIEF VALVE: A relief valve or pressure relief valve is a type of safety valve used to control or limit the pressure in a system; pressure might otherwise build
up and create a process upset, instrument or equipment failure, or fire.

OIL TEMPERATURE INDICATOR: - It is the distance thermometer operated on principle of liquid expansion. It indicates the top oil temp. At marshaling box. The connection between the thermometer and the dial indicator is made by steel capillary tube.

TRIPPING = 110 deg C
ALARM = 95 deg C

WINDING TEMPERATURE INDICATOR: it operates on principles of liquid expansion. It indicates the top oil temp. Winding temperature indicators consist of sensor
bulb placed in oil filled pocket in the transformer tank top cover.

OIL LEVEL INDICATOR: - Magnetic Oil Gauge (MOG) in Power Transformer. Magnetic Oil Level gauge or MOG is provided in a Power Transformer to indicate the level of insulating oil in the Conservator. A decrease in level of Transformer Oil in Conservator is an ndication of leak and therefore MOG level is animportant parameter to be monitored.
DEHYDRATING BREATHER: - The conservator or the air cell is connected
to the outside atmosphere through the breather (silica gel) to make sure that the air in the conservator or cell is dry. When silica is saturated with moisture its color changes to pink. It can be made reusable by heating it at 100 deg C. for 48 hours.