Arrestor Configuration on 230kV Delta Winding 2

[fluxcap]

IEEE C62.22 recommends that for a delta connected primary you configure 3 arrestors in a wye configuration (rated at line to neutral voltage) with a fourth arrestor connecting these three to ground. Ref IEEE C62.22 Figure Eight on Page 28 (Sect 5.5.4.2).

Does anyone have any physical drawings showing this applied for a 230kV primary (utilizing 144kV MCOV arrestors)? The height of the arrestors and/or insulator requirements appears to preclude us from applying directly at the transformer, and a horizontal arrangement may be difficult with the fourth arrestor.

 

[bacon4life]

Does your utility usually configure arrestors that way? No one I have asked at my utility has heard of using more than 3.

 

[cuky2000]

The enclose sketch present two options to install 4 surge arresters as described in IEEE Std C62.22. Even thought this is not a usual lightning arrester configuration, there are conditions that that conventional 3 phase-to-ground SA do not meet the protection requirement.

There are other possible configurations for phase-to-phase protection using polymer arrester downward or installing OH line arrester.

I hope this could help.

 

[doctorbou]

What are the conditions that the 3 line to ground arresters are not sufficient?

My case is the following, I have 30kV/0,69kV transformers (Delta primary) on which the manufacturer only installed phase to phase arresters. The local authority (TUV) questions this practice.
All our power distribution is with underground cables, the plant incoming 30kV feed comes also in underground cables from an outside 110kV/30kV substation. Do I need to have line to ground arresters on the transformers?

 

[rconnett]

I had to do it a number of years ago, Frank, at a steel mill to give equal BIL protection for phase-phase transients as phase - ground transients.

GE mounted all 3 on a plate, then supported the plate with post insulators, and then tied the plate to ground with a single arrestor of the same rating.

 

[wfowfo]

In a rather unique application, we back-fed 3 single phase 69 kv/12.47 kv transformers connected wye on the low side and delta on the high. The 69 kv in this case had no ground reference.
The problem was that if a line went to ground, or an arrester collapsed a phase to ground during a surge, it put phase to phase voltage across the other two arresters.