Has anyone looked into applying directional INST (50P) setting to reduce the IE levels at the pad mount transformers?

Where is the relay? If on the high side, an instantaneous relay set as a maintenance setting could be used to reduce incident energy for a secondary fault. In most situations, it would not have to be directional.

the relay is on the 34.5kV side, in theory the wtg would be sending power towards the utility hence any current coming towards the wtg would indicate a fault condition correct? My plan would be to set the 50P about the FLA or the wtg, probably 150% of the FLA in the direction towards the wtg. While i agree that would not have to be dirctional you would mae it less inclined to be sensitive to nuisance trip if you allow a directional.

34.5kv - is this primary side to a transformer with the fault on the secondary side?

what does wtg stand for.

I have never set a 50P relay and could only find a minimal amount of info. From what I read they work off the principle of a phase shift. Under fault conditions there is a wide and severe phase shift between voltage and current, and pf of .1 to .15 can be observed. The only problem I would see for arc flash is that the arc current may be only 25% to 50% of Isc. So the phase shift would not be as severe.

Agree with Haze.....what is wtg? Unless you have more than one source, no need for directional relays. Unless these are maintenance setings, 150% inst. will most likely not allow enough margin to pick up the pad mount from dead start for normal ops.

My assumptions:
1. wtg means "wind turbine generator".
2. 50P is a phase instantaneous overcurrent relay.
A non-directional instaneous overcurrent relay will not coordinate with downstream relays for faults on the 34.5 kV system. If this is a maintenance setting only, you probably want to trip for any fault anyway.

T24177,
Sorry I missed your reply on my post. It seems as if we share the same concerns. I recently discussed a push button program activation on the 351(SEL) to drop the instantaneous while work being performed on a circuit. It appears SEL already has the software ready (personally unconfirmed). This could be part of a LOTO, Switching order, JSA etc. with a signoff so that the settings go back to normal after the job is completed.

I recieved a wiring diagram from SEL that showed how to wire up a "maintenance switch" with an input into the relay. I used a shotgun stick (72") for operating the disconnect switch on the 34.5kV side in addition to placing barriers (glastic) on the 600V side thus allowing me to change the Working Distance from 18" to 72" and it dropped the Incident Energy from above 90 cal/cm^2 to below 40 cal/cm^2. without having to use a INST setting.