Surge arrestors and circuit breakers
Surge arrestors and circuit breakers
(OP)
Hello,
I have a colleague who is causing quite a bit of a stir at the moment. He is insisting that you need to connect a circuit breaker in series with a surge arrestor. He insists it is a new law or standard that he heard about that is coming into effect in my country (Australia).
Since most Australian standards come from changes already made overseas, I was wondering if anybody in other countries have to do this?
I personally think it all sounds a bit odd - a 100kA surge arrestor in series with a 10kA circuit breaker. What's the point if the circuit breaker might blow off the wall with the next lightning strike.
I have a colleague who is causing quite a bit of a stir at the moment. He is insisting that you need to connect a circuit breaker in series with a surge arrestor. He insists it is a new law or standard that he heard about that is coming into effect in my country (Australia).
Since most Australian standards come from changes already made overseas, I was wondering if anybody in other countries have to do this?
I personally think it all sounds a bit odd - a 100kA surge arrestor in series with a 10kA circuit breaker. What's the point if the circuit breaker might blow off the wall with the next lightning strike.






RE: Surge arrestors and circuit breakers
Typically, in the USA, TVSS are connected through a breaker or fuse to protect against the shorted TVSS. The kA rating of the breaker needs to be greater than the available SCC current.
Rafiq Bulsara
http://www.srengineersct.com
RE: Surge arrestors and circuit breakers
RE: Surge arrestors and circuit breakers
David Castor
www.cvoes.com
RE: Surge arrestors and circuit breakers
As to the kA rating, they need to be taken with a grain of salt. Having a quick look at a curve for a 100 kA device for a 60mm MOV, the curve states that the surge arrestor can withstand a 100 kA pulse for 20 micro-seconds and do this only once, after which it needs to be replaced.
The same device can only withstand a 1 kA pulse for 1000 micro-seconds again after which it needs to be replaced.
Always check the data sheets when claims of large kA ratings are made and compare them against the standard short and long pulse curves.
RE: Surge arrestors and circuit breakers
I have literally hundreds of drawings on my computer from various projects where the surge arrestors are connected directly to the load side of the main circuit breaker. Sometimes there is an isolator connected in series, but only sometimes.
I guess this is a good example of "Don't do something just because everyone else does it that way".
Thanks
RE: Surge arrestors and circuit breakers
David Castor
www.cvoes.com
RE: Surge arrestors and circuit breakers
Perhaps we should have asked what voltage you are talking about. The original post read like it is talking about LV system, your last post sounds like an HV system.
Rafiq Bulsara
http://www.srengineersct.com
RE: Surge arrestors and circuit breakers