Directional Relay VS Negative-Sequence Relay 1

[unclebob]

Do these relays do the same thing?

SEL literature describes Device Number 67 as Negative-Sequence Relay and ANSI as AC Directional OC Relay.

One Hydro-Quebec guy just told me they're not...

Your comments please.

 

[dpc]

Not the same thing. 67 is directional OC relay. 46 is generally used for negative sequence current relay.

I think SEL uses a suffix on the 67 to denote the a negative sequence directional overcurrent relay:

67P = directional phase OC
67Q = directional neg seq OC
67G = directional ground OC

They do the same thing with their non-directional OC elements.

But SEL is not always consistent between the relay models. And their use of "N" and "G" suffix is backwards from what most people use.

 

[Eleceng01]

dpc is right on both. I used to work for SEL and I have heard the comment of "N" ad "G" before.

 

[jghrist]

Schweitzer uses G for residual (calculated from phase currents) ground overcurrent and N for neutral (separate neutral current input) ground overcurrent.

 

[dpc]

In Blackburn's book and in nearly every other reference, the convention is exactly the opposite for G and N, IIRC.

Just Dr. Schweitzer's way of keeping us on our toes, I guess.

 

[npower0073]

Negative phase sequence relays 46A and 46T are used mainly to protect generators coupled to the grid from problems initiated by the grid itself, like single phase operation, fast auto reclosure of grid circuit breakers and any other incidence that cuases ayssmetry on the generator loading.

 

[slavag]

Hi.
Nu, now are next new terms 46A, 46T,in additional to 67P,G,N,Q and 32N,Q,P.
Are each US company used other terms ( GE, Basler, SEL)?
Regards.
Slava