51N Relay Settings for Unigrounded Systems Feeding Delta Connected Loads

[bwen08]

I'm trying to find some further reference material on determining the ground relay settings for a 3 wire solidly grounded system that feeds delta connected loads. (i.e. sub-transmission feeders with Dy1 power transformers) What situations would cause sympathetic trips to occur if the ground settings were set too low other than accuracy of the CT's & relay?

Thanks!

 

[cranky108]

How about single phase to ground connected loads that the field guys fail to tell you about. Or capacitor banks with fused primarys (where one fuse may blow). Or a somewhat conducting arrestor. Or leakage current from a contamated insulator. Or a primary metered customer tap.

 

[LiteYear]

Also, non-linear loads (eg. rectifiers/switching devices) causing high frequency components that flow via parasitic capacitance to ground.