1000V Insulation Resistance Test on incoming phone line???

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Just wondering what would happen if one was to apply a 1000 volt insulation resistance test to the incoming phone line wires before the master socket.

I would hope the system has protection mechanisms built in and nothing would get damaged at the exchange end.

Not that I am going to try - certainly don't want to start WW3 with BT Openreach; just curious.
 
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Hopefully your insulation tester has protection and wouldn't apply test voltage to an energised circuit.
 
I believe there is a lightening protector in the master socket. Perhaps it would blow.
 
I believe there is a lightening protector in the master socket. Perhaps it would blow.

I meant if you unwired the master socket (what BT supposedly own, even though I bought and fitted my own.) and applied it to the incoming line from the street.

Would it affect other customers, or only damage your individual line. How about the DSLAM's in the Road fibre cabinets/Exchange, would they/it survive?

I have got a cheap Chinese 1000v IR tester what I doubt has any protection against energized circuits. :idea: :arrow: :evil: :arrow: :mad:
 
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In the old days of electromechanical exchange equipment ( Strowger ) a 1000 volt pulse would be very unlikely to do any harm. Even a few seconds of 1000 volt would ( probably ) be survivable although the coils in the line relay for that line would get hot. Most often these were 2 by 200 in series.

I doubt if the line card in a modern electronic exchange would survive 1000 volts. If I recall correctly the design specification for a German line card in 1970 was to survive and recover after 600 volts but the line involved need not remain operational ( there were several lines on a line card ).
 
Let's say in theory that I applied 1000v DC like I said (don't worry, I won't), would just me be affected or would other customers be affected to?

Also if I did it while connected to line test/fast test on 17070, would I also damage the loop diagnostic units in the exchange?

Wonder what also would be damaged apart from the Line Cards such as the DSLAM's?


Sure bet BT openreach would not be happy with me; wonder what sort of bill I would get from them?

In reality, I some how doubt it would do that much damage to the exchange, otherwise lighting strikes would be a constant issue.
 
In the good old days when all phone lines were over head

http://www.britishtelephones.com/gpo/overhead.htm

lightning strikes were a problem. Arrestors were fitted at both ends of the lines. Damage to the exchange equipment could be very costly as nnot all equipment was plug and socket, a replacing a damaged relay might require unsoldering between 8 to 20 wires from the relay. Hence protection from lightning ( and insulation testers ) was taken into account when the relays and general exchange construction were designed.

Today with most cable routes underground and plug in line cards with a few mass produced components it is cost effective to accept that a lightning strike does happen then damage to a line card is acceptable as the repair is to simply plug in a replacement line card.
 
Sure bet BT openreach would not be happy with me; wonder what sort of bill I would get from them?

Full cost of replacing damaged equipment including loss of profit and consequential losses.

I think a DSLAM is about £250 per port.
 
I think you'd get away with it at least once and the tech would arrange a new port without questioning much as they do fail from time to time. Second time would flag up though.

Think 1000v would be more likely to blow off a weak connection on your line and it could be anywhere - in your house, on the overhead line or in the underground somewhere. We used to use a 500v IR test when a line was intermittent crackly, and this would blow off the bad connection making it disconnected and a lot easier to locate using a TDR.

If you ran it at any point while the loop diagnostic was running it would record a message on the result saying dangerous voltages detected. The working part of the exchange is supposed to be shut down to personnel if anything over 200v is detected on the frame, until that line is isolated but I dont know if anyone cares these days. I have seen the 'dangerous voltage' placard being used to prop windows open and stabilise chairs so probably not.
 

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