Distribution transformer winding temp. detector - designed to produce correct thermal image of winding hot spot under any overload

摘要

The winding temperature detection produces a thermal image of the distribution transformer windings hot spot. The detector (61) is connected into an electronic circuit which controls a trip relay. The thermal image transducer (4) includes at least a non linear resistance (61) whose ohmic value increases rapidly after a given temperature level is exceeded. The resistance (61) is connected to a current transformer (41) on a line phase conductor (1) and is supplied with a current proportional to the current circulating in this phase conductor. At the terminals of the resistance a voltage is developed which is passed to the trip relay winding (10) and which assures the operation of the latter when this voltage exceeds a determined step value.