Sector Conductor - DC Conductor Resistance

Sector of what?? But if you are measuring the resistance of copper or another metal, then +/- 15 Celsius variation of temperature would cause resistance variation you mention. Specification ought to give standard temperature.

Dear 67model

I am referring the DC Res of sector shaped conductor of aluminium of sizes 50 Sqmm to 400 Sqmm corrected to 20 Deg at stranding machine practically seen at our factory.

As redfred has indicated, I shall provide case studies to help pinpoint the cause.

Regards

Reuben

Are you finding +/- 5% variation :-

1. Production batch to production batch?
2. Sample to sample from the same production batch?
3. Test to retest on same sample?

If 3. , a measurement problem is indicated, but the others, in the absence of 3., are likely to be material quality.

If it were possible, I would do a "reality check". This would be done by testing ~ 100m drum from a batch (I am sure you know very well the exact length) of 50 sq mm. Passing e.g. about 10 amps DC from a 12V car battery through a resistor and an accurate meter/shunt and measuring end to end drop with a good portable DVM (400 mV basic range 0.1 % grade) should give a resistance with a probable error of +/-1%. N.B. Resistor could mean 100m drum of 2 core 2.5 sq.mm copper cable (in 200m loop), so long as you measure amps/mV together, because they will change as it warms-up, due to current.

Calculate resistance V/I , correct for storage temperature, then compare with your sample conductor test result on that batch (and product spec).

Not knowing your test method (it might be a precision current source and precision millivoltmeter or a bridge arrangement and AC or DC), the following checks might be made :-

* To check sample clamp effectiveness, measure potential differences around a circumference of conductor. A difference indicates non-uniformity of current in sample.
* Measure longitudinal potential difference over a length near each clamp.
* measure potential from common, across any conductor tails, to each clamp segment.
* If possible, test sample with potential pickups moved to different positions around a circumference.
* Measure any test voltages or currents with an independent instrument(s) and compare with those built-in, and with values given in manual.
* Reverse test polarities, if possible.
* Apply test potentials (carefully!) to any critical instruments, to be sure there are no offset errors (a polarity reversal should find such errors).

There has been a post recently about calibration errors due to electromagnetic pickup [EMC], this cannot be excluded, particularly if you have recently added some computers to your installation, or your measurement equipment is very electronic. A good suggestion was to power the test equipment from a UPS (mains unplugged, running on batteries, hopefully not a serious EMC noise maker itself),turn off all other equipment in room and seeing if this caused different readings. DC bridges and mirror galvanometers were much less susceptible!

Regards,

67model

It might be a clamp problem. It could even be a problem with your instrumentation, but I doubt this. If it is your instrumentation then you will have to replace your equipment and depending on where the fault lies that can be very expensive. Depending on your situation it might even be actual variations in your cable resistance that is showing a poor manufacturing process somewhere. Most likely you have an operator error that has not been accounted for. Unfortunately to properly identify your problem will require a knowledgeable individual on site to investigate your methodology and instrumentation. If you bring us some real details on your testing techniques we will gladly provide countless suggestions where your problem might lie.

Thanks for the positive response. I shall take a few case studies and put it across.

Regards

Reuben