Directional current relay

Claim 2

In an electrical power system for producing alternating polarity voltage and current quantities, the combination comprising: circuit means for performing a predetermined operation in said electrical power system; control means coupled to said circuiT means and operative independently of the magnitude of said current and voltage quantities for controlling said operating circuit means; and a current direction indicator including: first circuit means coupled to said system for producing a first signal in response to the change in polarity of one of said quantities; second circuit means coupled to said system for producing a second signal when the other one of said quantities has a predetermined polarity; and third circuit means coupled to said first circuit means, said second circuit means and said control means and being responsive toe the occurrence of both of said signals during a predetermined time period to produce a third signal to the control means whereby the latter is actuated to control the operating circuit means.

Claim 3

The combination according to claim 1 wherein said control means comprises circuit means for modifying current flow to the operating circuit means.

Claim 4

The combination according to claim 2 wherein said operating circuit means comprise current level sensing means coupled to said control means and being responsive to said current flow for initiating interruption of the voltage and current quantities in said system, said level sensing means being operative after a time delay inversely proportional to the level of said current flow whereby said control means controls said time delay as a function of the current direction in said system.

Claim 5

The combination according to claim 1 wherein: said first circuit means includes a phase current circuit coupled to said system and producing said first signal in response to change in polarity of a phase current in said system, said first circuit means also including a ground current circuit coupled to said system and producing said first signal in response to change in polarity of ground current in said system; said second circuit means includes a phase-to-phase voltage circuit coupled to said system and producing said second signal when a phase-to-phase voltage in said system has said predetermined polarity, said second circuit means also including a phase-to-neutral voltage circuit coupled to said system and producing said second signal when the phase-to-neutral voltage has said predetermined polarity; said third circuit means includes output circuit means connected to said control means, said output circuit means producing said third signal in response to the occurrence during said predetermined time period of the first and second signals respectively from the phase current circuit and the phase-to-phase voltage circuit or in response to the occurrence during said predetermined time period of the first and second signals respectively from the ground current circuit and the phase-to-neutral voltage circuit.

Claim 6

In an electrical power system producing alternating polarity voltage and current quantities, a current direction indicator comprising: first circuit means coupled to said system and including a relaxation oscillator circuit for producing a first signal in response to a change in polarity of one of said quantities; second circuit means coupled to said system for producing a second signal when the other one of said quantities has a predetermined polarity; and third circuit means coupled to said first circuit means and said second circuit means and being responsive to the occurrence of both of said signals during a predetermined time period to produce a third signal indicative of current flow in said system in a predetermined direction.

Claim 7

In an electrical power system producing alternating polarity voltage and current quantities, a current direction indicator comprising: first circuit means coupled to said system and including a relaxation oscillator circuit for producing a first signal in response to a change in polarity of one of said quantities; second circuit means coupled to said system for producing a second signal when the other one of said quantities has a predetermined polarity; and third circuit means coupled to said first circuit means and said second circuit means and being responsive to the occurrence of both of said signals during a predetermined time period to produce a third signal indicative of current flow in said system in a predetermined direction.

Claim 8

The combination according to claim 5 wherein said first circuit means includes a current transformer coupled to said system and having a secondary winding producing an alternating polarity current to said relaxation oscillator circuit, the operation of said relaxation oscillator circuit being inhibited while said transformer current has a predetermined polarity.

Claim 9

The combination according to claim 6 wherein said relaxation oscillator circuit produces a fourth signal and comprises a three electrode static switch including an anode receiving said fourth signal, said static switch being conductive in response to receipt of the fourth signal at said anode.

Claim 10

The combination according to claim 6 further comprising control means coupled to the third circuit means and being operative independently of the magnitude of said current quantity for performing a predetermined modification to said electrical power system in response to said third signal.

Claim 11

The combination according to claim 7 further comprising: time delay means having a controllable variable time delay period for delaying interruption of said electrical power system; and wherein said control means is operative to control said variable time delay period.

Claim 12

In an electrical power system producing an alternating polarity voltage quantity, a current quantity flowing in either of two opposite directions, and including a circuit breaker for interrupting said system, the combination comprising; circuit breaker operating means including time delay circuit means for delaying operation of the circuit breaker, said time delay circuit means having two different conditions each corresponding to one of the opposite flow directions of the current quantity and having a variable time delay determined by said conditions; first circuit means coupled to said system for producing a first signal in response to a change in polarity of one of said quantities; second circuit means coupled to said system for producing a second signal when the other one of said quantities has a predetermined polarity; and third circuit means for sensing the occurrence of said first and second signals within a predetermined time period, the occurrence of said signals within said time period indicating a flow of said current quantity in one of said opposite directions, said third circuit means being responsive to the occurrence of said signals within said predetermined time period to operate the time delay circuit means from one of said conditions to the other of the conditions whereby said time delay period is varied.

Claim 13

In an electrical power system producing an alternating polarity voltage quantity, a current quantity flowing in either of two opposite directions, and including a circuit breaker for interrupting said system, the combination comprising; circuit breaker operating means including time delay circuit means for delaying operation of the circuit breaker, said time delay circuit means having two different conditions each corresponding to one of the opposite flow directions of the current quantity and having a variable time delay determined by said conditions; first circuit means coupled to said system for producing a first signal in response to a change in polarity of one of said quantities; second circuit means coupled to said system for producing a second signal when the other one of said quantities has a predetermined polarity; and third circuit means for sensing the occurrence of said first and second signals within a predetermined time period, the occurrence of said signals within said time period indicating a flow of said current quantity in one of said opposite directions, said third circuit means being responsive to the occurrence of said signals within said predetermined time period to operate the time delay circuit means from one of said conditions to the other of the conditions whereby said time delay period is varied.

Claim 14

The combination according to claim 10 wherein the third circuit means is responsive to the simultaneous occurrence of said first and second signals to operate the time delay circuit means from one of said conditions to the other.

Claim 15

The combination according to claim 10 wherein: said circuit breaker operating means includes a current transformer coupled to said system and having a secondary winding producing current proportional to the current in said system; the time delay of said time delay circuit means is inversely proportional to the magnitude of said secondary winding current, and the time delay circuit means has a different magnitude of secondary current flowing in it in each of said different conditions.

Claim 16

The combination according to claim 11 wherein said first circuit means includes: a current transformer coupled to said system and having a secondary coil producing an alternating polarity current; and a relaxation oscillator circuit coupled to said secondary coil and operative signal in response to the alternating current from the secondary coil.

Claim 17

The combination according to claim 10 wherein: said electrical power system comprises a three phase system; said first circuit means produces a first signal for each one of said phases; said second circuit means produces a second signal for each one of said phases; said third circuit means is responsive to the occurrence of said first and second signals related to the same one of any of said three phases within said predetermined time period to operate the time delay circuit means from one of said conditions to the other of the conditions; and the coupling of said first and second circuit means to said three phases is removable from the same one of any of said phases, said first and second circuit means producing the first aNd second signals related to the remaining coupled phases to the third circuit means independently of the removal of the coupling of the first and second circuit means to the one phase.