[TCUG] Re: 6 year electrical testing
- From: "Bill Emett" <bill.emett@xxxxxxxxxxxxxxxxxxxxxxx>
- To: <tcug@xxxxxxxxxxxxx>
- Date: Tue, 15 Jun 2004 14:44:18 +0100
Why would you need to disconnect all cores at pole top, surely only one
core would be necessary to form a circuit to test and an ELI test will
also prove armoring.
Most courses on this subject relate to house wiring which suggests you
only have to test 20% of the system this should reduce the down time if
applied to signals. Unless this 20% shows a problem then the whole
system has to be checked.
One of the queries I have is with E.L.I testing at poles is as
follows,
Our contractors tell me they use a spare live feed but this would only
test straight from the origin via whatever fuse they use to the pole
back via the armored cable and the usual Manweb path to the substation
this is bound to give a favourable result.
This can't give the practical reading via the phase drive circuits
which are essentially in series and have there own resistance which must
be included in the E.L.I figure.
A figure quoted for a max E.L.I test for a particular controller is 5
ohms which is down to the 10A fuse on the phase drive card, not the main
20 or 30 amp fuse in the supply which this figure would fail.
>>> chris.gladwyn@xxxxxxxxxxxxxxxxxx 15-Jun-04 1:33:39 pm >>>
I am currently looking at TCUG guidance Note 1 which in section 2.4.7
suggests that core to core testing may be omitted as there is a
possibility of :-
1. Reduced safety for highway users whilst installation inoperative
for
lengthy periods (perhaps up to 3 days at complex sites).
2. Insecure reconnection of cables especially on older installations.
3. Incorrect retermination of cables at either street equipment or
controller.
4. Additional traffic congestion while temporary arrangements in
operation.
5. Loss of special facilities (pedestrians, cycles, bus priority) for
long periods
Whilst I agree with this the document then recommends that the
continuity of the steel wire armour be tested. The test procedure for
this is to disconnect every core at the pole cap and then connect all
cores together and connect to the SWA.
Surely some of the arguments for core to core testing apply to this as
well.
Does anyone have advice on this and is there an alternative test that
could be carried out that would meet the requirements of BS7671
without
having to disconnect all connections in the pole cap.
Chris Gladwyn
Hertfordshire Highways
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