Sequence based network protector relay with forward overcurrent protection and antipumping feature
First Claim
1. A network protector relay for controlling a circuit breaker connected between a polyphase feeder bus and a polyphase network bus, said network protector relay comprising:
- digital sensing means digitally sampling polyphase current flowing through said circuit breaker and polyphase network voltage on said network bus at least sixteen times per cycle to generate digital polyphase current samples and digital polyphase network voltage samples;
digital processor means comprising means for generating positive sequence current and voltage vectors from said digital polyphase current samples and digital polyphase network voltage samples, and means tripping said circuit breaker open in response to a selected relationship between said positive sequence current and voltage vectors indicating flow of current from said polyphase network bus to said polyphase feeder bus above a predetermined threshold;
wherein said digital sensing means digitally samples said polyphase current and said polyphase network voltage sequentially and wherein said digital processor means includes means adjusting phase angles of said digital polyphase current samples and digital polyphase network voltage samples for such sequential sampling; and
wherein said digital processor means includes means deriving from said digital polyphase current samples and said digital polyphase voltage samples metered parameters, and wherein said digital sensing means digitally samples said polyphase current and said polyphase network voltage alternately in a first order for a given number of cycles and then in a second order which is a reverse of the first order for said given number of cycles.
1 Assignment
0 Petitions
Accused Products
Abstract
A digital network protector relay samples the polyphase current, network voltage and phasing voltage at 16, and preferably 32, times per cycle so that up to the seventh and fifteenth harmonics, respectively, are eliminated from the sequence calculation used to make trip and close decisions. The relay also provides metering, forward overcurrent protection, and an anti-pumping feature, the latter of which locks the circuit breaker out if a selected number of breaker operations is exceeded during a given time interval. Sequential sampling of the polyphase current and voltages by a single analog to digital converter reduces the cost of the relay. In order to accommodate metering and extraction of the fundamental components of the current and voltages for the sequence calculations, the polyphase current and network voltage are sampled sequentially in a first order for a given number of cycles and then in a second reverse order for the same given number of cycles.
103 Citations
5 Claims
-
1. A network protector relay for controlling a circuit breaker connected between a polyphase feeder bus and a polyphase network bus, said network protector relay comprising:
-
digital sensing means digitally sampling polyphase current flowing through said circuit breaker and polyphase network voltage on said network bus at least sixteen times per cycle to generate digital polyphase current samples and digital polyphase network voltage samples; digital processor means comprising means for generating positive sequence current and voltage vectors from said digital polyphase current samples and digital polyphase network voltage samples, and means tripping said circuit breaker open in response to a selected relationship between said positive sequence current and voltage vectors indicating flow of current from said polyphase network bus to said polyphase feeder bus above a predetermined threshold; wherein said digital sensing means digitally samples said polyphase current and said polyphase network voltage sequentially and wherein said digital processor means includes means adjusting phase angles of said digital polyphase current samples and digital polyphase network voltage samples for such sequential sampling; and wherein said digital processor means includes means deriving from said digital polyphase current samples and said digital polyphase voltage samples metered parameters, and wherein said digital sensing means digitally samples said polyphase current and said polyphase network voltage alternately in a first order for a given number of cycles and then in a second order which is a reverse of the first order for said given number of cycles. - View Dependent Claims (2, 3, 4, 5)
-
Specification