Schweitzer Relay- 51a & 51b
Schweitzer Relay- 51a & 51b
(OP)
Under relay settings for 50 , I see two settings 50a,50b
50Na and 50Nb, what are these parameters represent?
50Na and 50Nb, what are these parameters represent?
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Schweitzer Relay- 51a & 51b
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RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
These are settings that customer set their relay at,so it maybe their own designation type. the values are
50a:3840
50b:640
51:640
50Na:3840
50Nb:900
50N:400
RE: Schweitzer Relay- 51a & 51b
I don't know this relay, but here my 0.02$.
50a and 50b are two steps of DT overcurrent protection
51 is IDMT OC
51Na and 50Nb are two steps of DT ground overcurrent protection. 51N is IDMT GP.
For my pinion are standard IEEE codes.
50a and 50Na are inst steps.
Best Regards.
Slava
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
Like all the rest of us do.
RE: Schweitzer Relay- 51a & 51b
Please for me and others. Once and forever.
Are 50N means residual connection ( or internal calculation) of 3 phases.?
Are 50G is connection to the zero-CT?
it's terible mix of termenolgy
Best Regards.
Slava
RE: Schweitzer Relay- 51a & 51b
50P1P=50b=640
50P2P=50a=3840
there is a 50P3P which is not used anywhere( at least i cant find it).
So what are these two values ( 51B and 51a) represent. I know that they have defined 50a as Hi set instantanious, what about 50b ?
RE: Schweitzer Relay- 51a & 51b
Then there are other manufacturers of relays that have N (or G, could be) elements that you have to select whether they are residual or measured.
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
Prior to digital relays, there was a "general" consensus in the US regarding this terminology:
G = relay connected to a single CT in grounded neutral
N = relay connected to the neutral of three CT secondary circuits ("residual") connection.
But this was never a standard, AFAIK. SEL decided to (mostly) do it the opposite of this. I guess whoever sells the most relays gets to make the standards.
I have to double-check this every time I set a relay.
RE: Schweitzer Relay- 51a & 51b
Are the 51B and 51a typos or are you throwing in some settings you didn't discuss before?
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
RE: Schweitzer Relay- 51a & 51b
This seems to match the Schweitzer convention except for the SEL-321.
RE: Schweitzer Relay- 51a & 51b
Broken delta VT secondary connection - N
Current in grounded wye neutral of transformer - G*
* G is preferred, past practice make N acceptable
Generator with high-impedance ground - G
Residually connected CT secondaries (or internally derived by device) - N
Tank ground - G
CT in delta tertiary of auto transformer - N
Donut CT enclosing three phases - G
You can see that a relay manufacturer can only guess how the fourth current input might generally be used. The same pair of terminals might be used for a donut CT, residual connection, tank ground, tertiary, or grounded neutral CT in different applications.