[TCUG] Re: 6 year electrical testing
- From: "Bill Emett" <bill.emett@xxxxxxxxxxxxxxxxxxxxxxx>
- To: <tcug@xxxxxxxxxxxxx>
- Date: Tue, 15 Jun 2004 15:11:46 +0100
I also agree with a test on all poles, also that damage could occure to
the lamp drives during testing, but as the lamp drives form part of the
path to the pole then they would have to be included in any ELI results
to prove a low enough impedance to isolate the pole within 5s of a live
short to the pole.
>>> Paul.Welsh@xxxxxxxxxxxxxxxxxx 15-Jun-04 2:54:06 pm >>>
The acceptable impedance has to take account of the actual circuit.
The
fuse used for the test needs to have a reasonable value to ensure that
it
withstands the test current. Which is why testing through the lamp
drives
should be avoided, it could damage them. There are claims that they
should
not be damaged, but why take a risk of abusing a device not designed
for the
test load?
As for 20% testing, don't risk it! Remember there have been knock downs
etc
in the preceding six years, this isn't a nice cosy house, it is a much
harsher environment. The site file should have copied of impedance
tests
from each repair, but are they being done/recorded? (If not why not?)
The
six year test updates the whole site record and needs to be completed
and
filed.
PW
-----Original Message-----
From: Bill Emett [mailto:bill.emett@xxxxxxxxxxxxxxxxxxxxxxx]
Sent: 15 June 2004 14:44
To: tcug@xxxxxxxxxxxxx
Subject: [TCUG] Re: 6 year electrical testing
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 >>>
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