Generator Neutral Arrester

[Schwatzernov]

Hi,

I have seen the standard generator single line diagram of Siemens always shows the surge arrester between generator neutral grounding transformer and ground for gas turbine generator started with static frequency converter.

The question is that why the arrester is need to be connected bewteen NGT and ground ?

I have not seen other generator manufacturers connect such arrester like this.

Can anyone explian why it is need for machine started with SFC ?

Thank you very much.

Schwatzernov.

 

[7anoter4]

Usually for directional grounding protection a CT is provided beside the VT. Since for grounding current measurement a shunt is provided and it can not be insulated for 10/sqrt(3)kV [in one phase grounding case] an arrester is required to protect the shunt, I think.

 

[Alex68]

During start up with SFC, Siemens usually isolated the neutral from grond to avoid harmonics flows and improper trip of protections.
In this condition, the surge arrester protects against overvoltages

Regards
Alex