Coordination with Utility settings
Coordination with Utility settings
(OP)
I am doing a coordination study for a ficility. I got a TCC curve from a Utility company.They set their Curve way below our main incomer curve. This a radial distribution sytem. A 5MVA transformer (69kV/4.16kV) is supplying power to a 4160V SWGR, which is a single power source.Secondary cable is underground buried.Primary is overhead. The transformer is delta/wye(high resistance)connected. Utilty comapny set their curve based on frequent fault and WYE sencondary grounded so that the curve was shifted to the left to be 58% of normal TCC curve. My understanding is, the transformer damage curve should be based on infrequent fault and normal curve, because ony when the transformer is wye solid grounded, primary side will see 58% fault current.58%rule doesn't apply to high resistance grounded system.
We can't move our curve down, but how can we convince the utility company to accept our suggested curve? Possibly we will have to get our client to be involved and get this conflict to be solved.
Who have a better suggetion for this?
ThanX in advance.
We can't move our curve down, but how can we convince the utility company to accept our suggested curve? Possibly we will have to get our client to be involved and get this conflict to be solved.
Who have a better suggetion for this?
ThanX in advance.






RE: Coordination with Utility settings
The use of frequent vs. infrequent damage curves is subject to debate and interpretation. If the utility owns the transformer, they will decide how to protect it. If your client owns the transformer, you should be able to negotiate this.
ANSI defines "frequent" as 10 or more through faults in the life of the transformer.
You're correct regarding the shifted damage curve - for a resistance grounded system, this is a non-issue.
I would try to discuss with the utility and offer them some alternative settings. It won't hurt to ask.
And actually, you CAN move your curve down - you just may have to compromise on downstream coordination.
RE: Coordination with Utility settings
I think I will get our client to be involved to solve this issue.
RE: Coordination with Utility settings
RE: Coordination with Utility settings
RE: Coordination with Utility settings
RE: Coordination with Utility settings