| 摘要 |
A test circuit (39) which is passed via the encapsulation and earth (E) and in its further course contains a current transformer (28) is formed by closing two earthing switches (16, 17) which are arranged on both sides of the switching apparatus (9) to be tested. This test circuit (39) is disconnected from the remainder of the switching installation (1) by opening adjacent isolating switches (14, 20, 21). When the switching apparatus (9) is open, the current transformer (28) is supplied on the secondary side. The contact arrangement (10) of the switching apparatus (9) is now closed, and the time of closing is determined by detecting the start of the current flow (I1) in the test circuit (39). Furthermore, the distance is measured which the moving contact element (11) travels before the closing time is determined. A comparison of this measured distance with a required value which corresponds to the closing movement in the new state produces the measure of the contact erosion. <IMAGE>
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