Surge Arrestors installation location 1

[gdeep]

Hi everyone,

I am working on a project that has a 1.5 km of transmission line feeding a 230kV substation with a disconnect switch, breaker and a 230kV/35kV transformer. I understand we need to install a surge arrestor in front of the transformer to protect it, but would there be one needed in front of the disconnect switch to protect the breaker and the disconnect switch? I haven't run any insulation coordination studies but wondering if there is anything specific in the IEEE/IEC standard that talks about it?

Thanks in advance

 

[Power0020]

well, there is no one correct answer here, however, the disconnector open isolating distance should have a BIL greater than insulators so we shouldn't worry about the DS in open position in the case of flashing away. The IC study will tell the need of line entrance SA with the DS open however I understand in your case you won't worry of such outage and you may use a small arc gap to protect the DS (with a setting greater than SA level).

With the other case of closed DS and CB, if the distance between the SA and CB/DS isn't too long (I suggest ~ 20 m), you will be well protected with the SA installed on the 220 kV side of the transformer. Detailed IC should be carried out to confirm this however we shouldn't worry about DS CB damage if in closed position.

 

[magoo2]

You can find some information on this in IEEE C62.22, particularly in Annex C, which goes through the calculation in detail. Also, there's some in IEC 60099-5.