Surge Arrester 1

[Linspire]

Dear all,

I would like to request reading material on regards Surge Arrester.
I have came across the different class for SA such as distribution class for teaser reactor and station class IV.
So, would like to learn more.



Thank you.

Regards,
Goh Kian Hui

 

[Linspire]

Anyone here can guide me or provide the information ?

 

[dpc]

How hard have you looked? Check the Cooper Power, and ABB websites. You should be able to find plenty of background info on surge arresters.

 

[rcw retired EE]

Search for Ohio Brass Hubbell arrestors. Their website used to have good tutorial data.

 

[Linspire]

Anyone know why for 275kV system , the rated surge arrester is lower than system voltage, 264 KV ?

and why for 33 kV system, the rated surge arrester is higher than system voltage, 36 kV ?

 

[davidbeach]

How are the two systems grounded?

 

[Tufael]

I too want an answer for this?

 

[Linspire]

What do you mean how systems grounded ?

Sorry if this is simple question, I'm not sure.

 

[magoo2]

If a system is effectively grounded, then it will use a lower rated surge arrester relative to the line to line operating voltage. An ungrounded system or one that is not effectively grounded will require one that is rated above the rated line to line voltage.

 

[Linspire]

Well, what do you mean by not effectively grounded ?

 

[davidbeach]

What is the source of the 33kV system? Is it from a delta winding or from a wye winding? If from a delta is there a separate grounding bank or is it the system ungrounded? If from a wye winding, how is the neutral grounded?

 

[magoo2]

Effectively grounded is usually described in terms of a bunch of ratios of sequence impedance quantities.

From a high level perspective, an effectively grounded system is one where, under mainly single-line-to-ground faults, the voltage on the unfaulted phases will be no higher than around 1.25 per unit. So you won't see more than a 25% voltage rise. Based on this, you can get by with an arrester rating close to 80% of the phase-to-phase voltage.

For a system that is not effectively grounded, the unfaulted phase-to-ground voltage will approach 100% phase-to-phase voltage so you can't use an 80% arrester; you'll need a 100% arrester (again referring to the % of phase-to-phase voltage).

I can give you the sequence impedance ratios if you like, but I wanted to give you a better understanding of what we're dealing with first.

 

[Linspire]

It would be great if you guys show diagram / figure to explain it.

If not mistaken for 275 kV system, if there is delta-winding, usually use earthing transformer for grounding.

As for wye-winding, I think is straight grounding to the copper tape. Sorry, if I'm not answering to the question.