At short circuit on the case of trailer seal there has to be a current of single-phase short circuit exceeding rated current of a fusible insert of the next safety lock or rastsepitel of the automatic switch. Excess has to be not less, than is specified in PUE
1 – transformer of the VP-60 rectifier, 0,22/42,5 kV; 2 - transformer of the VP-5/10 rectifier, 7 kV And; 3 – VP-10/5 switch; 4 – generator of sound frequency of ATO-8; 5 – the transformer coordinating 8 kV And, 1000/500/380/110 B; 6 – switch; 7 – adjusting transformer of tension of 250 Century.
At fast definition of a place of damage repair of the line is limited to replacement of a site of a cable 3 — 5 m long and two connecting couplings, in opportunities one coupling can be installed. If works on definition of a place of damage are tightened that conducts to moisture penetration, there is a need of replacement of a site of a cable with a length moistened with isolation already in some tens meters, It, in turn, increases the volume of earthwork and conducts to rise in price of repair of the line.
Damages of C have various character: damage of isolation with short circuit of one vein on the earth; damage of isolation with short circuit of two or three veins on the earth, two or three veins among themselves in one or in different places; break of one, two or three veins with grounding and without grounding of veins; the swimming-away isolation breakdown; the difficult damages containing the specified types of damages. The most widespread case is a damage between a vein and a cover of a cable, i.e. single-phase damages, especially for cables with veins in independent covers.
Test by the straightened tension, unfortunately, reveals not all weakened places of isolation of C. In particular, do not come to light: electric aging of isolation; drainage of isolation because of movement or running off of impregnating structure; drying of isolation because of a heavy thermal operating mode of cable lines.