Medium Voltage Terminations

[Norman Miller]

We are experiencing rejection of Medium Voltage terminations by our Russian Q.C. Inspectors. Construction personnel are removing Semi conductive layer with tool suplied by Termination kit provide leaving some slight indentations in the inulation layer, these identations are so slight that you have to use a magnifying glass to see them. I have had the contractor clean the identation areas with very fine sandpaper and wipe the insualtion down to make the surface smooth, however the intereptation by the QC Inspectors state that their information is that any blemish is unacceptable and theref ore the cable needs to be changed. Can expert in MV or HV terminations or splicing provide any information to me that can be shown that what maybe or not be done in preparation of terminations or splicing.

Norman Miller
Electrical Superintendent
PFD

 

[celtic]

Re: Medium Voltage Terminations

W...Construction personnel are removing Semi conductive layer ...eaving some slight indentations in the inulation layer, these identations are so slight that you have to use a magnifying glass to see them. I have had the contractor clean the identation areas with very fine sandpaper and wipe the insualtion down to make the surface smooth, however the intereptation by the QC Inspectors state that their information is that any blemish is unacceptable and theref ore the cable needs to be changed.

Many times when removing the semi-con. layer, a gouge or other undesirable mark is make on the di-electric layer. This mark is smoothed out using a fine grit sandpaper (just as the contractors on your job have done).
As long as the gouge/mark is superficial and does NOT compromise the di-electric insulation, the sandpaper should completely eradicate any evidence that an "error" occurred.
There should be NO blemishes on the di-electric insulation.
After the cables are terminated, they should be proof tested by a 3rd party to ensure the integrity of the termination.


This is a typical Okoguard?-Okoseal? Type MV-105 5/8kV Shielded Power Cable (Okonite) that is used in MV applications:

A Uncoated, Okopact (Compact Stranded) Copper Conductor
B Strand Screen-Extruded Semiconducting EPR
C Insulation-Okoguard EPR (di-electric insulation)
D Insulation Screen-Extruded Semiconducting EPR
E Shielding-Copper Tape
F Jacket-Okoseal

There should be no blemishes on item "C".


How are your people removing the semi-con. layer?
It can be a difficult to remove without damaging the di-electric. I have found that a heat gun (or even a blow dryer) will soften up the semi-con. and make it a bit easier to manipulate.

What brand of kits are you using?
What brand of cable are you using?

Can expert in MV or HV terminations or splicing provide any information to me that can be shown that what maybe or not be done in preparation of terminations or splicing.

I'm no "expert" on MV cables, but I have done a few hundred terminations.

My comments are my OPINION - based on my experiences and my training.

 

[Norman Miller]

MV Terminations

MV Terminations

Thanks for the information.
We are using Raychem termination kits. The cable is Noskab XLPESWA. This cable is metric Compacted Copper cable and is also presenting a problem with the type of Cable Lugs. The standard lugs e.g. 185 mm2 conductors are smaller than the 185mm lugs and the contractor has been using a 150mm die for the compresion. The resultant cross section of the lug looks good when we have cut a sample. however the lug manufacturers say the correct die must be used i.e. 185mm lug = 185 mm die. This has also presented another problem the lug ID and OD varies based on the lug some appear to be a heavy wall and some a thinner wall. The lugs are Burndy-Bicon.

 

[celtic]

I have used Raychem products - haven't had the opportunity to land a Noskab cable.
Are/will these cables be underwater?