500kV Surge arrester (MOV)

[vangiang]

Dear All,
I have a problem about using 500kV MOV for replacing pre-insert resistor of 500kV CB .
Does anyone have document, calculation method, ... or experience this problem.

Thank you

Van Giang

 

[Skogsgurra]

Is this in a simulation? Or are you actually fiddling around with 500 000 volt circuit breakers on your own?

Please do not. The HV guys should do that.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[vangiang]

Hi Gunar,
I really want to find the document around this problem. When we close the EHV Tranmission line, the switching overvoltage is big problem and in this case the pre-insert resistor is one of a choice. However this solution is very expensive. Normally, MOV (surge arreter) for line feeder is installed already, so everybody use it to replace the pre-insert resistor of CB.
I'm worry about how can I choose the best spec for MOV in this case.
And now, I have two papers from IEEE ("Elimination of closing resistors on EHV CB - 1988" and "An application Metal oxide SA in elimination of need for closing resistor in EHV CB - 1989", however It is only the general information.

Does anyone help me?

Tuan

 

[Skogsgurra]

Sorry that I cannot help you. I saw those monsters long time ago when I was doing work at the ABB HV lab in Ludvika. But never touched them or learned about them. What does the HV equipment manufacturer say?

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Bahram7]

Hi Tuan,

It is true that by using MOV line-entrance arresters you can eliminate the need of closing resistors on a majority of transmission lines from 400 kV up to 800 kV.
If you do fast reclosing (0.5 s) on long lines you need to make sure about the arresters energy capability.

Bahram7

http://www.simtech-intl.com

 

[vangiang]

Hi Bahram7,
Could you talk clearly about "If you do fast reclosing (0.5 s) on long lines you need to make sure about the arresters energy capability" ?

Thanks,
Van Giang

 

[Bahram7]

Van Giang,

Fast reclosing means that the breaker will reclose on the line with almost full trap charges. This may dissipate a lot of energy in the arrester. Utilities buy normally 2 columns line arresters at 500 & 800 kV to make sure that the line arresters will not fail during line discharges.

Bahram7

 

[vangiang]

Thank you, Bahram7.

A B
-O--------------------O--
When breaker A closed and breaker B still opened, maybe the highest voltage will drop on MOV of B. In restricted case, this switching voltage is about 3pu (3x449kV)in 500kV system.
You may be right. Could you tell me about the spec of MOV (two columns) which can protect against switching voltage during reclosing?

Van Giang

 

[cuky2000]

Even though surge arresters and closing resistors are the most popular methods for limiting switching surge magnitude in transmission systems, there are other means to limits overvoltages such as adding shunt reactors, operating restrictions, shorter lines by adding intermediate switching stations or using breaker timing (synchronous closing).

Closing resistor is still one of the most effective methods to reduce the breaker stresses. The enclose figures show a typical performance of surge arrester and closing resistor reducing the magnitude of the overvoltage seen by the circuit breaker contacts.

http://cuky2000.250free.com/Switching_Surge_1.jpg