How to determine if a metrosil is required? 1

[veritas]

Hi

With a high impedance diff application how does one actually determine whether a voltage limiter (like a Metrosil) is required? Easiest is to determine the inzone fault current (secondary value) and multiply by the stabilising resistor. If answer is > 2kV then Metrosil needed.

Is it really so simple considering that the output from the CT will be severely distorted, thus applying rms calcs don't make sense???

Is there a formula to calculate the peak secondary circuit voltage for an inzone fault with a high z scheme?

Thanks.

 

[electricnewbie123]

Refer MCAG14 relay application guide to calculate the peak voltage during an internal fault. The guide is available from

http://www.gegridsolutions.com/alst...urces/Documents/Automation/HIREFBP/R6136D.pdf

 

[veritas]

Thanks electricnewbie123