Temp. monitor for HV transformer winding - has three limb transformer between sensor-relay and power supply-indicator circuits with two windings on each outer limb

摘要

The application is typically to the winding temp. monitoring of dry type power transformers with a rated voltage in excess of 1150 volt. Sensors (15) and relay circuits (11, 12) with low insulation levels can be used by placing an isolating transformer (8) between the high voltage side components and the power supply (1, 2) and indicating instrument (3, 4). The isolating transformer has a three limb core with power supply primary (Ia) and secondary (Ib) on one outer limb, and indicating winding primary (IIb) and secondary (IIa) on the other. Normally the indicator primary is short circuited (13). At high temperature the relay picks up (12) connecting the indicator primary winding (IIb) across the power supply secondary (Ib) thereby giving an output to the indicator.