Parallel incomers
Parallel incomers
(OP)
I have a strange situation at one of my customers, and was wondering if anyone else has seen this before.
I have just completed load and harmonic recordings at the South Africa national broadcaster. They have the 3 incomers with 2 x bus ties between them. These ties are closed and thus the incomers are all in parallel. The CT's on the incomers are identical, and they are all fed from the utility substation about 1kM from the substation.
The Transformers feeding the system are all identical.
When the customer switches off his capacitor banks (directely connected to the busbar), the current only goes up on the 1 incomer.
I would have thought that because the incomers are in parallel the current would have gone up equally on each incomer. We have tested the system and all breakers are in and there doesnt seem to be a problem with any of the CT's.
The problem transmits to the council metering as well, but they cant tell me what the problem could be..
Please help.
I have just completed load and harmonic recordings at the South Africa national broadcaster. They have the 3 incomers with 2 x bus ties between them. These ties are closed and thus the incomers are all in parallel. The CT's on the incomers are identical, and they are all fed from the utility substation about 1kM from the substation.
The Transformers feeding the system are all identical.
When the customer switches off his capacitor banks (directely connected to the busbar), the current only goes up on the 1 incomer.
I would have thought that because the incomers are in parallel the current would have gone up equally on each incomer. We have tested the system and all breakers are in and there doesnt seem to be a problem with any of the CT's.
The problem transmits to the council metering as well, but they cant tell me what the problem could be..
Please help.






RE: Parallel incomers
Regards
Marmite
RE: Parallel incomers
What Marmite said.
Best Regards.
Slava
RE: Parallel incomers
Is the load at the bottom end of the ct capacity?
I agree with Marmite cable route length and impeadance play a big part in what you are seeing.
It would be unusual for a supply company to parallel his network entirely through customers switchgear, more likely the 3-feeders are tied together at both ends.
RE: Parallel incomers
They have 400/5 CT's and are running about 150A at 11kV on each incomer.
3 incomers have identical current readings when cap bank is in.
They havent thought it through but all three cables run next to each other from one busbar (3 x feeders) in the utility sub.
They might have bus ties between the feeders in the utility sub though. I will enquire about the bus ties changing position in the utility substation.
Thanks