Protective relay device

• US 4,246,623 A
• Filed: 09/08/1978
• Issued: 01/20/1981
• Est. Priority Date: 09/08/1978
• Status: Expired due to Term

• Current Assignee: ABB Power T&D Limited (ABB Limited)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Sun, Shan C.
• Primary Examiner(s): Salce, Patrick R.
• Application Number:
  US05/940,801
• Time in Patent Office: 865 Days
• Field of Search: 361/93, 361/94, 361/95, 361/96, 361/97, 361/98, 361/100, 361/31, 361/196, 361/44, 361/45, 307/293
• US Class Current: 361/97
• CPC Class Codes: H02H 1/066 and comprising a shunt regulator
• CPC Class Codes: H02H 3/0935 the timing being determined by numerical means

Abstract

An electrical device for protecting an alternating current network in which a static inverse time-overcurrent relay obtains network current information and relay circuit operating power from a current transformer having two secondary windings. Low transformer burden and accurate network information signals that are linearly responsive to a wide range of network current magnitudes are achieved through the use of a switching circuit that prevents the simultaneous operation of both secondary windings. The relay circuit employs an RC network with a short, precision time constant for curve shaping and employs digital counting techniques to provide time delay multiplication, precision time scale selection and a variable delay time variable in accordance with the magnitude of system current.

Claims

1. An electrical quantity responding device comprising;

a current transformer,

said current transformer including a primary winding adapted to be energized by an alternating current, and first and second output windings,

power supply means responsive to said first output winding,

current sensing means responsive to said second output winding,

and control means controlling said first and second output windings to achieve substantially complete balancing of the ampere turns of the primary winding in a selected one of said first and second output windings, and then in the other, within the same half cycle of the alternating current.

2. The electrical quantity responding device of claim 1 including first and second rectifier means for providing unidirectional signals for the power supply means and for the current sensing means, responsive to the outputs of the first and second output windings, respectively.

3. The electrical quantity responding device of claim 1 wherein the control means includes switching means switchable between conductive and nonconductive states, said switching means being connected to activate and deactivate the second output winding in response to the conductive state of the switching means, and means for controlling the conductive state of said switching means.

4. The electrical quantity responding device of claim 1 wherein the control means includes regulator means for regulating the power supply means, switching means switchable between conductive and nonconductive states, said switching means being connected to activate and deactivate the second output winding in response to the conductive state of the switching means, and means responsive to said regulator means for controlling the conductive state of said switching means.

5. An electrical quantity responding device comprising:

a current transformer,

said current transformer including an input winding adapted to be energized by an alternating current, and first and second output windings providing first and second electrical quantities, respectively,

rectifying means rectifying said first electrical quantity,

energy storage means adapted to be energized by said rectified first electrical quantity,

a detecting circuit for providing an output electrical quantity when the magnitude of said second electrical quantity exceeds a predetermined value,

and control means controlling said first and second output windings to provide their first and second electrical quantities during different portions of the same half cycle of the alternating current, such that the energy storage means provides no load on the current transformer when the second output winding is providing its second electrical quantity to said detecting circuit.

6. The electrical quantity responding device of claim 5 wherein the first and second output windings are interlinked by the same flux path, said first output winding having N₁ turns and when effective providing said first electrical quantity, said second output winding having N₂ turns which exceeds N₁ turns, and when effective providing said second electrical quantity.

7. The electrical quantity responding device of claim 5 wherein the control means comprises first and second switching means switchable between conductive and non-conductive states, said second switching means being connected to the second output winding, said second switching means changing to its non-conductive state at the end of each half cycle of the alternating current, to render said second output winding ineffective and said first output winding effective at the start of each half cycle of the alternating current, said first switching means being connected to the first output winding and to the second switching means, said first switching means changing from its non-conductive state to its conductive state during each half cycle of the alternating current which causes said second switching means to switch to its conductive state, said second switching means, upon switching to its conductive state, rendering the second output winding effective and the first input winding ineffective.

8. The electrical quantity responding device of claim 7 including impedance means connected to be responsive to said second electrical quantity when the second switching means is conductive, and semiconductive means connected to limit the maximum voltage magnitude across said energy storage means to substantially a predetermined value and to operate the first switching means when said predetermined maximum voltage magnitude across said storage device is reached, to cause the first switching means to switch to its conductive state.

9. The electrical quantity responding device of claim 8 wherein the impedance means is a resistor connected such that the second output electrical quantity provides a voltage across said resistor when said second output winding means is rendered effective.

10. The electrical quantity responding device of claim 9 wherein the voltage applied to the energy storage means in response to the first electrical quantity drops below the predetermined value of the energy storage means when the second output winding becomes effective, and including unidirectional means connected between the first output winding and the energy storage means which effectively disconnects the energy storage means from the first output winding to render it ineffective, when the voltage of the energy storage means exceeds the voltage applied thereto in response to the first electrical quantity.

11. The electrical quantity responding device of claim 9 wherein said resitor has a magnitude such that for all expected magnitudes of the alternating current in the input winding of the transformer, the ratio of the turns in the first output winding to the turns in the second output winding multiplied by the magnitude of the voltage across said resistor provides a magnitude less than the magnitude of the predetermined maximum voltage across the energy storage means.

12. The electrical quantity responding device of claim 10 wherein the second switching means is a thyristor.

13. The electrical quantity responding device of claim 10 wherein said second switching means comprises means for deenergizing said switch device when the magnitude of said second electrical quantity falls below a predetermined value.

14. The electrical quantity responding device of claim 10 wherein the semiconductive means comprises at least one Zener diode.

15. An electrical quantity responding device, comprising:

a current transformer,

said current transformer having an input winding adapted for energization by an alternating current, and first and second output windings providing first and second electrical quantities, respectively,

energy storage means, said energy storage means including first and second capacitors, diode mean interconnecting said first and second capacitors with said first output winding such that said first capacitor provides a negative regulated voltage supply, and said second capacitor provides a positive regulated voltage supply,

detector means providing an output electrical quantity when the magnitude of said second electrical quantity exceeds a predetermined value,

and control means controlling said first and second output windings to provide their first and second electrical quantities during different portions of a half cycle of the alternating current, such that said energy storage means provides no load on said current transformer when the second output winding is providing its second electrical quantity to said detector means.

16. An electrical quantity responding device comprising:

a current transformer,

said current transformer including an input winding adapted to be energized from an alternating current network, and a first and second output winding means that are interlinked by the same flux path, said first output winding means when effective providing a first output current and having a fewer number of winding turns N₁ than the number of winding turns N₂ in said second output winding means, said second output winding means when effective providing a second output current having a magnitude proportional to the magnitude of the current in said alternating current network,

control means controlling said first and second output winding means when that substantial magnitudes of said first and second output currents are provided by said output winding means in a sequential manner,

an energy storage device to be energized by said first output current,

a detecting circuit providing an output electrical quantity when the magnitude of said second output current exceeds a predetermined value,

and limiting means for desensitizing said electrical quantity responding device when the magnitude of said current in said alternating current network exceeds a predetermined value.

17. The electrical quantity responding device of claim 16 wherein the detector circuit includes a resistor, and wherein the limiting means comprises a shunt circuit for shunting the second output current from said resistor when the current in the alternating current network exceeds the predetermined value of the limiting means.

18. The electrical quantity responding device of claim 17 wherein the shunt circuit comprises a voltage responsive switch device and means connecting said switch device in parallel with said resistor such that when the voltage across the resistor exceeds a predetermined magnitude, the second output current will be shunted from the resistor and through said switch device.

19. The electrical quantity responding device of claim 18 wherein the voltage responsive switch device comprises a Zener diode, a thyristor, and connecting means connecting said Zener diode to said thyristor such that said second output current flows through said thyristor when the voltage magnitude across said Zener diode exceeds the breakover voltage of said Zener diode.

20. A detecting circuit for an electrical quantity sensing device for the protection of an alternating current network, said detecting circuit comprising:

an input circuit,

said input circuit providing a DC voltage having a magnitude responsive to the magnitude of the electrical quantity in said alternating current network,

and a time delay circuit connected with said input circuit such that an output electrical quantity is provided by said time delay circuit at a predetermined time TD after the magnitude of said DC input voltage exceeds a predetermined pickup value,

said time delay circuit comprising circuit activating means, an RC network having at least one branch connected between input and output means, pulse generating means and counting means, said circuit activating means inhibiting and resetting the operation of said time delay circuit until the magnitude of said DC input voltage exceeds said pickup value, said RC network having its input means connected to be responsive to the DC voltage provided by said input circuit, said RC network providing an output at its output means responsive to the DC voltage, said pulse generating means providing a pulse when the output of said RC network reaches a predetermined value, with said pulse advancing said counting means and also resetting and freeing said RC network to again be responsive to the DC input voltage, said counting means providing said output electrical quantity upon receipt of a predetermined number of the pulses from said pulse generating means.

21. The detecting circuit of claim 20 wherein said pulse generating means comprises a monostable multivibrator and triggering means, said triggering means generating a voltage pulse when the output of the RC network reaches the predetermined level, with the voltage pulse having a magnitude sufficient to energize said monostable multivibrator, said monostable multivibrator providing, in response to said voltage pulse a rectangular pulse shaped voltage having a predetermined pulse width TD2, said rectangular pulse shaped voltage advancing the counting means and resetting the RC network.

22. The detecting circuit of claim 21 wherein the RC network includes resistive and capacitive elements, and reset means for momentarily deenergizing all of said capacitive elements, said RC network requiring, after said capacitive elements have been momentarily deenergized, a predetermined time period TD1 to generate an RC network voltage signal having a magnitude large enough to energize the triggering means, said time delay TD1 varying inversely with the magnitude of the DC input voltage.

23. The detecting circuit of claim 22 wherein the RC network comprises a plurality of parallel branches, each of said branches having resistive and capacitive elements, connecting means connecting said branches such that each of said branches provides a predetermined branch voltage having an inverse time characteristic, with the summation of said branch voltages providing the output of the RC network.

24. The detecting circuit of claim 20 wherein the counting means includes means for selecting the number of output pulses from the pulse generating means which will cause the counting means to provide the output electrical quantity.

25. The detecting circuit of claim 20 wherein the counting means includes binary counting means responsive to the output pulses from the pulse generating means, decade counting means connected to be responsive to said binary counting means, and selector switch means connected to said decade counting means for selecting a desired time scale reference curve.

26. A polyphase electrical quantity sensing device for use with a polyphase alternating current network, said sensing device comprising:

an input circuit,

said input circuit providing a DC voltage having a magnitude responsive to the highest magnitude of the phase currents in said network,

and a detecting circuit comprising a time delay circuit, said time delay circuit comprising an RC circuit having an input and output means, circuit activating means, pulse generating means and counting means, said circuit activating means inhibiting and resetting the operation of said time delay circuit until the magnitude of said DC input voltage exceeds a predetermined value, said RC network having its input means connected to be responsive to the DC voltage provided by said input circuit, said RC network providing an output at its output means responsive to the DC voltage, said pulse generating means providing a pulse when the output of said RC circuit exceeds a predetermined value, with said pulse advancing said counting means and resetting said RC circuit to again be responsive to the DC voltage, said counting means generating an output electrical quantity upon receipt of a predetermined number of pulses from said pulse generating means, to multiply the time delay of the RC circuit.

27. An electrical quantity responding device comprising:

a current transformer;

said current transformer including a primary winding adapted to be energized by an alternating current, and first and second output windings;

power supply means responsive to said first output winding;

current-sensing means responsive to said second output winding;

first and second rectifier means for providing unidirectional signals for the power supply means and for the current-sensing means, responsive to the outputs of the first and second output windings, respectively;

and control means controlling said first and second output windings to achieve substantially complete balancing of the ampere turns of the primary winding in a selected one of said first and second output windings, and then in the other, within the same half cycle of the alternating current, said control means including unidirectional means connected between the first rectifier means and the power supply means, switching means connected to the second rectifier means to activate and deactivate the second output winding in response to its conductive state, and means responsive to said power supply means for controlling the conductive state of said switching means, said unidirectional means effectively disconnecting the power supply means from the first rectifier means when said switching means activates the second output winding, to deactivate the first output winding.

28. An electrical quantity responding device comprising:

a current transformer;

said current transformer including a primary winding adapted to be energized by an alternating current, and first and second output windings;

power supply means responsive to said first output winding, said power supply means including energy storage means;

current-sensing means responsive to said second output winding;

first and second rectifier means for providing unidirectional signals for the power supply means and for the current-sensing means, responsive to the outputs of the first and second output windings, respectively;

and control means controlling said first and second output windings to achieve substantially complete balancing of the ampere turns of the primary winding in a selected one of said first and second output windings, and then in the other, within the same half cycle of the alternating current, said control means including unidirectional means connected between the first rectifier means and the power supply means, regulator means connected to regulate the voltage of said energy storage means, switching means connected to the second rectifier means to activate and deactivate the second output winding in response to its conductive state, and means responsive to said regulator means for controlling the conductive state of said switching means, said unidirectional means effectively disconnecting the power supply means from the first rectifier means when said switching means activates the second output winding, to deactivate the first output winding.

29. An electrical quantity responding device comprising:

a current transformer;

said current transformer including a primary winding adapted to be energized by an alternating current, and first and second output windings;

power supply means connected to be charged by said first output windings;

current-sensing means responsive to said second output winding;

and control means controlling said first and second output windings to achieve substantially complete balancing of the ampere turns of the primary winding in a selected one of said first and second output windings, and then in the other, within the same half cycle of the alternating current, said control means including regulator means responsive to the power supply means for providing a signal when the power supply means is charged by the first output winding, and including a controllable bridge rectifier connected to the second output winding, said controllable bridge rectifier being switched to a conductive state in response to the signal from said regulating means, to allow current flow through the second output winding and provide a unidirectional signal for the current-sensing means.

30. An electrical circuit for providing a predetermined current versus time response, comprising:

RC network means having at least one RC branch connected between input and output terminal means,

means applying a DC input voltage to the input terminal means of said RC network means;

means applying a DC reference voltage to the output terminal means of said RC network means,

said DC input voltage and said DC reference voltage both being in a charging relationship with said RC network means, with said DC input voltage and said DC reference voltage causing current to flow in said RC network means which results in current flow in a predetermined direction relative to said output terminal means when the DC reference voltage exceeds the DC input voltage;

said RC network means causing a predetermined change in said current at the output terminal means in response to the DC input voltage exceeding said DC reference voltage, with the time required to cause said predetermined change following the exceeding of the DC reference voltage by the DC input voltage being inversely proportional to the magnitude of said DC input voltage;

and detector means providing an output signal in response to the occurrence of said predetermined change in said current.

31. The electrical circuit of claim 30 wherein the detector means provides its output signal when the current flow into the output terminal means drops to zero.

32. The electrical circuit of claim 30 wherein the predetermined direction of the current caused by the DC reference voltage is into the output terminal means of the RC network means, with the detector means providing its output signal when the current into the output terminal means drops to zero.

33. The electrical circuit of claim 30 including a circuit breaker having trip setting means and trip actuating means, with the means providing the DC reference voltage being responsive to the trip setting means, and with the output of the detector means being applied to said trip actuating means.

34. The electrical circuit of claim 30 wherein the RC network means includes a plurality of RC branches connected in parallel between the input and output terminal means.

35. The electrical circuit of claim 34 wherein each RC branch has a different RC time constant.

36. An electrical circuit for providing a predetermined current versus time response, comprising:

RC network means having at least one RC branch connected between input and output terminal means,

means applying a DC input voltage to the input terminal means of said RC network means,

means applying a DC reference voltage to the output terminal means of said RC network means,

said DC reference voltage causing current to flow in a predetermined direction relative to said output terminal means when the DC reference voltage exceeds the DC input voltage,

said RC network means causing a predetermined change in said current in response to the DC input voltage exceeding said DC reference voltage, with the time required to cause said predetermined change following the exceeding of the DC reference voltage by the DC input voltage being inversely proportional to the magnitude of said DC input voltage,

detector means providing an output signal in response to the occurrence of said predetermined change in said current,

a circuit breaker having trip setting means and trip actuating means,

pulse generating means,

counting means,

reset means for the RC network means,

and decoding means,

said means providing the DC reference voltage being responsive to said trip setting means,

said pulse generating means providing a pulse when the detector means provides its output signal, said pulse advancing said counting means and causing said reset means to reset the RC network means and free it to again be responsive to the DC input voltage,

said decoding means providing a trip signal for said trip actuating means in response to a predetermined count on said counting means, to multiply the time delay provided by the RC network means.