Phase shift detector

Claim 2

A reverse power flow detector for indicating the direction of power flow in an alternating current electrical power line comprising, in combination, means coupled to said electrical power line for deriving a voltage signal indicative of the voltage on said power line, means coupled to said electrical power line for deriving a current signal indicative of the current flowing in said power line, means coupled to said voltage signal deriving means for shifting the phase of said voltage signal through a predetermined angle, means coupled to said phase shifting means for deriving a voltage pulse at the leading edge of the positive half cycle of the phase-shifted voltage signal, means coupled to said current signal deriving means for deriving a first rectangular current pulse from the half cycle of one polarity of said current signal, means coupled to said first rectangular current pulse deriving means for deriving a second rectangular current pulse which is shifted 180* in phase from said first rectangular current pulse, and logic means coupled to said voltage pulse deriving means and to said first current pulse deriving means and also to said second current pulse deriving means for providing a first output when said voltage pulse coincides with said first rectangular current pulse and for providing a second output when said voltage pulse coincides with said second rectangular current pulse.

Claim 3

A reverse power flow detector in accordance with claim 1 wherein said means for deriving a voltage pulse includes high gain amplifier means for shaping said voltage signal into a rectangular wave, diode means coupled to said high gain amplifier means for passing half cycles of one polarity of said rectangular wave, and differentiating means coupled to said diode means for generating said voltage pulse at the leading edge of said half cycle of one polarity of said rectangular wave.

Claim 4

A reverse power flow detector in accordance with claim 1 wherein said means for deriving a voltage pulse includes a first high gain operational amplifier, said means for deriving a first rectangular current pulse includes a second high gain amplifier, and said detector includes an integrated circuit element which incorporates both said first and said second operational amplifiers.

Claim 5

A reverse power flow detector in accordance with claim 1 wherein said logic means includes first NAND gate means receiving said voltage pulse and said first rectangular current pulse as inputs and second NAND gate means receiving said voltage pulse and said second rectangular current pulse as inputs.

Claim 6

A reverse power flow detector in accordance with claim 4 wherein said logic means also includes a latch circuit receiving the outputs of said first and second NAND gate means as inputs.

Claim 7

A reverse power flow detector in accordance with claim 1 wherein said means for deriving a first rectangular current pulse includes a high gain amplifier in series with a diode.

Claim 8

A reverse power flow detector in accordance with claim 1 wherein said means for deriving a first rectangular current pulse includes a hiGh gain operational amplifier and positive feedback means from the output of said logic means to the input of said operational amplifier for biasing said operational amplifier so that its output is positive when no current flows in said power line.

Claim 9

A reverse power flow detector in accordance with claim 1 wherein said means for deriving a first rectangular current pulse includes a high gain operational amplifier in series with a diode, said logic means includes first NAND gate means receiving said voltage pulse and said first rectangular current pulse as inputs, second NAND gate means receiving said voltage pulse and said second rectangular current pulse as inputs, and a latch circuit receiving the outputs of said first and second NAND gate means as inputs, and positive feedback means from said latch circuit to the input of said operational amplifier for biasing said operational amplifier so that its output is positive when no current flows in said power line.

Claim 10

A reverse power flow detector for indicating direction of power flow in an alternating current electrical power line comprising, in combination, means coupled to said electrical power line for deriving voltage and current signals indicative respectively of the voltage on and the current in said power line, means coupled to said voltage signal deriving means for shifting the phase of said voltage signal approximately 90* , a dual amplifier integrated circuit embodying first and second operational amplifiers, means coupled to said phase shifting means and including said first operational amplifier for deriving a rectangular voltage pulse from the positive half cycle of said voltage signal, differentiating means coupled to said rectangular voltage pulse deriving means for generating a sharp voltage pulse at the leading edge of said rectangular voltage pulse, means coupled to said current signal deriving means and including said second operational amplifier for deriving a first rectangular current pulse from the positive half cycle of said current signal, means coupled to said first current pulse deriving means for deriving a second rectangular current pulse shifted 180* from said first rectangular current pulse, and logic means coupled to said differentiating means and to said first rectangular pulse deriving means and also to said second rectangular pulse deriving means for providing a first output when said sharp voltage pulse coincides with said first rectangular current pulse and for providing a second output when said sharp voltage pulse coincides with said second rectangular current pulse.

Claim 11

A reverse power flow detector for indicating direction of power flow in an alternating current electrical power line comprising, in combination, means coupled to said electrical power line for deriving voltage and current signals indicative respectively of the voltage on and the current in said power line, means coupled to said voltage signal deriving means for shifting the phase of said voltage signal approximately 90* , a dual amplifier integrated circuit embodying first and second operational amplifiers, means coupled to said phase shifting means and including said first operational amplifier for deriving a rectangular voltage pulse from the positive half cycle of said voltage signal, differentiating means coupled to said rectangular voltage pulse deriving means for generating a sharp voltage pulse at the leading edge of said rectangular voltage pulse, means coupled to said current signal deriving means and including said second operational amplifier for deriving a first rectangular current pulse from the positive half cycle of said current signal, means coupled to said first current pulse deriving means for deriving a second rectangular current pulse shifted 180* from said first rectangular current pulse, and logic means coupled to said differentiating means and to said first rectangular pulse deriving means and also to said second rectangular pulse deriving means for providing a first output when said sharp voltage pulse coincides with said first rectangular current pulse and for providing a second output when said sharp voltage pulse coincides with said second rectangular current pulse.

Claim 12

A power flow detector in accordance with claim 9 including a four NAND gate integrated circuit embodying first, second, third, and fourth NAND gates and wherein said logic means includes said first NAND gate receiving said voltage pulse and said first rectangular current pulse as inputs, said second NAND gate receiving said voltage pulse and said second rectangular current pulse as inputs, and a latch circuit including said third and fourth NAND gates and wherein said third NAND gate receives as inputs the output of said first and fourth NAND gates and said fourth NAND gate receives as an input the output of said second NAND gate.

Claim 13

A reverse power flow detector for indicating the direction of power flow in an alternating current power line comprising, in combination, means coupled to said power line for deriving voltage and current signals indicative of the voltage on and the current in said power line, means coupled to said voltage signal deriving means for shifting the phase of said voltage signal approximately 90* , means coupled to said phase shifting means and including a first high gain operational amplifier and a diode for deriving rectangular voltage pulses from the positive half cycles of said phase-shifted voltage signal, differentiating means coupled to said diode for generating a sharp vOltage pulse at the leading edge of each said rectangular voltage pulse, means coupled to said current signal deriving means and including a second high gain operational amplifier and a diode for deriving first rectangular current pulses from the positive half cycles of said current signal, means coupled to said first current pulse deriving means for deriving second rectangular current pulses which are shifted 180* in phase from said first rectangular current pulses, logic means including first NAND gate means receiving said sharp voltage pulses and said first rectangular current pulses as inputs for providing a first output when said sharp voltage pulses coincide with said first rectangular current pulses, thereby indicating that said power flow is in the forward direction, and second NAND gate means receiving said sharp voltage pulses and said second rectangular current pulses as inputs for providing a second output when said sharp voltage pulses coincide with said second rectangular current pulses, thereby indicating that the power flow is in the reverse direction, and positive feedback means from said logic means to said second high gain operational amplifier for biasing said second operational amplifier positive when no current flows in said power line.

Claim 14

A reverse power flow detector for indicating the direction of power flow in an alternating current power line comprising, in combination, means coupled to said power line for deriving voltage and current signals indicative of the voltage on and the current in said power line, means coupled to said voltage signal deriving means for shifting the phase of said voltage signal approximately 90* , means coupled to said phase shifting means and including a first high gain operational amplifier and a diode for deriving rectangular voltage pulses from the positive half cycles of said phase-shifted voltage signal, differentiating means coupled to said diode for generating a sharp vOltage pulse at the leading edge of each said rectangular voltage pulse, means coupled to said current signal deriving means and including a second high gain operational amplifier and a diode for deriving first rectangular current pulses from the positive half cycles of said current signal, means coupled to said first current pulse deriving means for deriving second rectangular current pulses which are shifted 180* in phase from said first rectangular current pulses, logic means including first NAND gate means receiving said sharp voltage pulses and said first rectangular current pulses as inputs for providing a first output when said sharp voltage pulses coincide with said first rectangular current pulses, thereby indicating that said power flow is in the forward direction, and second NAND gate means receiving said sharp voltage pulses and said second rectangular current pulses as inputs for providing a second output when said sharp voltage pulses coincide with said second rectangular current pulses, thereby indicating that the power flow is in the reverse direction, and positive feedback means from said logic means to said second high gain operational amplifier for biasing said second operational amplifier positive when no current flows in said power line.