Synchronism check relay
AssigneeGeneral Electric Company
InventorThomas B. Breen
Life of this patent
Estimating the term…
Abstract
A synchronism check relay includes both a high set and a low set slip cut-off circuit. The low slip cut-off setting is based upon the maximum slip frequency that can be tolerated and still allow reclosing. The high slip cut-off setting is a function of the maximum phase angle difference permissible between the voltages on the bus and line sides of the circuit breaker, and the time that the line is de-energized.
Claims27
An apparatus for determining synchronism between first and second voltages present on opposite sides of an open circuit breaker in an AC power distribution system, said apparatus comprising:
- a. means for setting a closing angle limit .theta.;
- b. means for setting a high slip frequency limit F.sub.H ;
- c. means for setting a low slip frequency limit F.sub.L ;
- d. means for measuring phase angle difference .phi. between said first and second voltages;
- e. means for measuring slip frequency F.sub.S between said first and second voltages;
- f. means for comparing .phi. with .theta. and generating a circuit breaker reclose enable signal whenever .phi. remains less than .theta. for a predetermined period of time T.sub.H which is a function of F.sub.H ;
- and
- g. means for detecting predetermined low set measurement conditions and, whenever said measurement conditions are detected, comparing F.sub.S with F.sub.L and preventing the generation of said reclose enable signal when F.sub.S is greater than F.sub.L.
A method for determining synchronism between first and second voltages present on opposite sides of an open circuit breaker in an AC power distribution system, said method comprising the steps of:
- a. setting a closing angle limit .theta.;
- b. setting a high slip frequency limit F.sub.H ;
- c. setting a low slip frequency F.sub.L ;
- d. measuring phase angle difference .phi. between said first and second voltages;
- e. measuring slip frequency F.sub.S between said first and second voltages;
- f. comparing .phi. with .theta. and generating a circuit breaker reclose enable signal whenever .phi. remains less than .theta. for a predetermined period of time T.sub.H ;
- and
- g. detecting predetermined low set measurement conditions and, whenever said measurement conditions are detected, comparing F.sub.S with F.sub.L and preventing the generation of said reclose enable signal when F.sub.S is greater than F.sub.L.
Dependencies are inferred from the claim text.