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EN 61242中关于线盘的接地电阻的测量中,有如下规定:* I u5 p8 D$ }, |! M; O/ a
9.7 Internal earthing circuit in cable reels, including any joints contacts and the like, shall be of low
8 i! L$ a7 E( V/ `! N# Q2 Oelectrical resistance.
0 d4 Q+ z! _7 Z0 D% O" YCompliance is checked by the following measurement which is made after the test specified in Clause 21.
: B ]' _ x% j( F+ b8 r6 ]& @3 oA current derived from an a.c. source, having a no load voltage not exceeding 12 V, and equal 1.5 times rated! A) h- M& b3 Y! h
current of the cable or 25 A, whichever is the greater, is passed through the earthing circuit.2 @/ H N) W2 b
The voltage drop is measured and the resistance calculated from the current and this voltage drop.6 h+ a! _% k/ K* J7 h& _
The resistance shall not exceed 0,05 Ω..5 _" I0 Q% f( P- ?2 |
# j5 O7 d! s5 m: p4 a+ H测量时,发现如果包含其线盘所带的电缆在内测接地电阻,是绝对大于0.05的,而且主要的电阻产生于电缆本身, 1 g" v- S H0 }5 h
我知道在60335中测接地电阻时将电源线是排除在外了的,但是在这个标准里面并没有提到这一点,但是考虑到一般电缆在一定长度下也达不到0.05的限值,那是否意味着这时也应将电源线排除在外呢?但有个问题就是,如果将电源线排除,那么绞线盘的接地电阻还有什么意义呢?0 F+ C; d+ d( ^4 F" ?
4 r1 _4 E. Z6 e W/ I6 v希望大家能讨论一下,指点迷津..谢谢~!! |
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