PT rating

[Sargardani]

While going through single line diagram of a power plant I found that the PT installed on a 66 kV line is rated as 42000-70/129v. I have a fairly basic question ; Is the PT of a correct rating? I shall be thankful for an explaination in this regard. Thank you.

 

[davidbeach]

If it is one of three PTs connected in a wye on a solidly grounded system it should be fine. The primary of the PT will only see Line-to-Neutral voltage, or about 38kV.

 

[busbar]

For ANSI regions, the closest standard PT rating is 350/600:1 or 40,250:120/69.3V.

For WXMYZ burdens [200VA or less] on the 120V secondary, the primary current on a single ø-g PT would be 5mA or less. This is trivial ground current for subtransmission/transmission voltage (C57.13 group 3 PTs.) [Typical AC test current for routine fall-of-potential ground-resistance testing in 40mA.]

 

[jbartos]

Comment on the previous posting: Would it be possible to verify that 42000-70/129V is correct, namely 129V appears to be a typo. 120V would be more appropriate.

 

[Sargardani]

jbartos (Electrical) ... you are right as ever. Its 120 v. Sorry for the typo error!

 

[jbartos]

Comment on Sargardani (Electrical) Apr 14, 2004 marked ///\\While going through single line diagram of a power plant I found that the PT installed on a 66 kV line is rated as 42000-70/129v. I have a fairly basic question ; Is the PT of a correct rating?
///It depends on its application on the one-line. Would you post what is this PT for? Some PT applications must have their primary connected to line conductors.\\