PAD MOUNTED TRANSFORMER PRIMARY CABLE

Status
Not open for further replies.
R

RLMJR

Member
Location
British Indian Ocean Territory (Diego Garcia)
Occupation
Electrical Engineer
I am handling a project that will replace a pad mounted transformer. 500KVA , 13.8KV to 480/277 V, the transformer is old and the oil insulation are leaking that is why it's need to be replace. I am not sure if i will include the replacement of primary cable as well in the scope. the primary cable is 1 AWG XLPE cable connected to 1200A Vacuum breaker from 13.8KV medium voltage switchgear , the primary cable is 32 years old base on the as built / year of installation. another challenge is the terminals of the new transformer is a few feet away from the existing conduit stub out, therefore we will need to extend the cable and SPLICE old XLPE cable into new EPR cable to extend the cable into the termination, i am thinking if i will replace the whole cable rather than perform splicing.

(As far as i know cable splicing is permitted and allowed as long as you use a pre manufactured splicing KIT like 3M 15kv splicing KIT) and the XLPE cables will last about 40 to 60 years but should be replace before it reach that age. Therefore i am confused and unsure if is it worth it to replace the primary cable.

Is there a reference or document or code that mandates to when (exact age) should you replace a primary cable?


Thank you in advance for the answer.
 
I don’t think there is a code, but “industry expectations“ are 35-40 years.
I wouldn’t splice new cable onto that old cable. The old XLPE is probably showing signs of treeing. Plus once you push and pull on it trying to splice it I doubt it will last another couple of years.
Its just not worth it to save what will have to be replaced anyway.
FWIW, every manufacturer will tell you it’s at end of life.

Edit. The EPR will also be so much easier to terminate. The old cable will take some time to prepare properly. The semi-con may not peel off like your used to with new cable.
 
I would suggest this. If you can easily replace the conductors in question and the added cost is relatively minimal, I would just do it. An extra $1,000 to avoid a service call down the road or finding out that there's something really wrong with those conductors that you didn't notice when you quoted it makes it worthwhile to just replace them.

Presumably you took a good look at the installation before quoting it and have a good idea of what condition the conductors are in and how much of them you would need to replace.

You should also consider the amount of time it will take you to accomplish the splicing and the cost of the splicing kits.
 
Hv&Lv said:
I don’t think there is a code, but “industry expectations“ are 35-40 years.
I wouldn’t splice new cable onto that old cable. The old XLPE is probably showing signs of treeing. Plus once you push and pull on it trying to splice it I doubt it will last another couple of years.
Its just not worth it to save what will have to be replaced anyway.
FWIW, every manufacturer will tell you it’s at end of life.

Edit. The EPR will also be so much easier to terminate. The old cable will take some time to prepare properly. The semi-con may not peel off like your used to with new cable.
Click to expand...
@HvLv,Thank you for your response. Another question is, does EPR cable have same cable diameter with XLPE, cause I'm planning to use the existing conduit to minimize the cost for new excavation and concrete breaking. Existing cable 3 x - 1 AWG 15kv XLPE in existing 3" PVC conduit. Planning to replace with new 3 x 1 awg 15kv EPR in existing 3" PVC conduit.
 
petersonra said:
I would suggest this. If you can easily replace the conductors in question and the added cost is relatively minimal, I would just do it. An extra $1,000 to avoid a service call down the road or finding out that there's something really wrong with those conductors that you didn't notice when you quoted it makes it worthwhile to just replace them.

Presumably you took a good look at the installation before quoting it and have a good idea of what condition the conductors are in and how much of them you would need to replace.

You should also consider the amount of time it will take you to accomplish the splicing and the cost of the splicing kits.
Click to expand...
@ Petersona, Thank you for the answer. Yes, decided to include the replacement of primary cables in the scope.
 
RLMJR said:
@HvLv,Thank you for your response. Another question is, does EPR cable have same cable diameter with XLPE, cause I'm planning to use the existing conduit to minimize the cost for new excavation and concrete breaking. Existing cable 3 x - 1 AWG 15kv XLPE in existing 3" PVC conduit. Planning to replace with new 3 x 1 awg 15kv EPR in existing 3" PVC conduit.
Click to expand...
The diameter differences are so minute I don’t think you need to worry about it. EPR will be smaller by thousandths

XLPE 1.120 inches vs EPR 1.085 inches
 
Status
Not open for further replies.
Top