Self-protected trip device for immersed electrical transformer

摘要

The arrangement comprises a light lever (6) made from, e.g. polypropylene. The lever is asymmetrically arranged about a pivot (7). When the lever is horizontal, its shorter arm (8) just fails to contact, with its finger (11), an actuator (2) of a trip-switch (5) that controls a primary side circuit-breaker. An open-topped (20) cup (10), terminates a longer arm (9) of the lever and is filled with oil. Initially, at the end of the tank filling process the arm swings up vertically as the oil rises in the tank; its movement being halted by a tank lid stop (12). If the tank leaks (17,13), the finger rises against the actuator to apply a force (Fd) mainly due to the weight of oil in the cup, which, at a preset value, overcomes the actuator resistance and trips the circuit-breaker, optionally, after a time delay.