Humble2000
Electrical
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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C37.2 Annex A gives several examples with schematics.
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.
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.
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