The safe operation and service life of oil immersed test transformers depend heavily on the safety and reliability of transformer winding insulation. One of the main reasons why the winding temperature exceeds the insulation withstand temperature, causing insulation damage and affecting the normal operation of transformers, is that monitoring and alarm control of the operating temperature of transformers are very necessary
1. Overtemperature alarm and trip: The temperature signal of the winding or iron core is collected through a PTC nonlinear thermistor embedded in the low-voltage winding. When the temperature of the transformer winding continues to rise and reaches 155 ℃, the system outputs an over temperature alarm signal; If the temperature continues to rise to 170 ℃, the transformer cannot continue to operate and an over temperature trip signal must be sent to the secondary protection circuit to quickly trip the transformer.
Active control of fan 2: The temperature signal is measured by a Pt100 thermistor embedded in the hottest part of the low-voltage winding. As the load on the transformer increases, the operating temperature rises. When the winding temperature reaches 110 ℃, the system actively starts the fan for cooling; When the winding temperature drops to 90 ℃, the system automatically stops the fan.
3 Temperature Display System: The temperature change value is measured by a Pt100 thermistor embedded in the low-voltage winding, and the temperature of each phase winding is directly displayed (three-phase inspection and maximum value display, and can record the highest temperature in history). The highest temperature can be output as an analog quantity of 420mA. If it needs to be transmitted to a remote location (with an interval of up to 1200m), an accounting machine interface can be added, and one transmitter can be used to monitor up to 31 transformers together. The system's over temperature alarm and tripping can also be triggered by Pt100 thermistor signals, further improving the reliability of the temperature control protection system.
Post time:2021-07-06 10:15:38