JP3013215B2 - Zero-phase voltage detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zero-phase voltage detecting device for detecting a zero-phase voltage of a three-phase electric line.

[0002]

2. Description of the Related Art In a three-phase distribution line, a monitoring device is provided to detect a line fault or to isolate a faulty section, and detects and outputs the current or voltage of the line or its zero-phase component. An apparatus for detecting the zero-phase voltage is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-96868. In this zero-phase voltage detecting device, a voltage dividing electrode is provided for each phase, and each divided voltage is detected by each voltage sensor head and converted into an optical signal. After correcting each optical signal converted by the voltage sensor head, the signals are combined to detect a zero-phase voltage.

[0003]

However, in order to detect an accident, four data of current of each phase, zero-phase current, voltage of each phase and zero-phase voltage can be detected. It is not always necessary to detect the voltage. Also, if the divided voltage of each phase is detected and converted into an optical signal by each voltage sensor head, and the obtained signals of each phase are simply synthesized, the output characteristics of each voltage sensor head will be reduced. It was not possible to obtain an accurate zero-sequence voltage due to the variation, and it was necessary to correct the individual values before combining. For this reason, not only an expensive voltage sensor head is required for each phase, but also a correction amplifier for correcting each phase is required, and the zero-phase voltage device is complicated and expensive.

In order to solve these problems, an object of the present invention is to provide a zero-sequence voltage detecting device having a simple structure.

[0005]

In order to achieve the above object, a voltage applied to each phase of a three-phase circuit is synthesized to detect a zero-phase voltage, and the detected zero-phase voltage signal is converted to a signal. In the zero-phase voltage detection device that transmits to the control unit by wires, the voltage dividing case, which is attached closely to the inner surface of the metal equipment case into which the conductors of each phase are drawn and loosely fits the conductors of each phase, has an inner wall. An annular storage groove is formed between the hollow portion formed by the above and the outer wall provided concentrically outside the inner wall to form a cylindrical shape, and the voltage dividing electrode is formed on the inner wall in the storage groove. And a ground electrode having an L-shaped cross section is disposed along the outer wall so as to cover the storage groove, and is provided in each of the phases. The voltage dividing electrode and the ground electrode are connected to each other, and the voltage dividing electrode and the ground electrode are connected to each other. A capacitor for capacitance correction is connected to the optical fiber, and an optical fiber is pulled out of an equipment case from a voltage sensor head that converts a divided voltage into an optical signal in parallel with the capacitor, and an optical signal transmitted by the optical fiber is electrically transmitted. The signal is converted into a signal and transmitted to the control unit.

[0006]

The voltage dividing case is attached closely to the inner surface of the metal equipment case into which the conductors of each phase are drawn. The voltage dividing case is formed in a cylindrical shape by forming an annular storage groove between a hollow portion formed by the inner wall and an outer wall provided concentrically outside the inner wall, and the voltage dividing electrode is formed in the storage groove. A ground electrode having an L-shaped cross section is disposed along the inner side wall in a loop, and is disposed along the outer side wall so as to cover the storage groove. For this reason, the voltage dividing electrode is surrounded by the device case and the ground electrode and is shielded from electrostatic induction, and both electrodes are arranged to face each other with a predetermined gap, so that the voltage applied to the conductor is accurately divided. Can be pressed. In this voltage dividing case, a potential difference is generated between the voltage dividing electrode loosely fitted around the conductor of each phase and the ground electrode due to the capacitance of the capacitor, and the voltage applied to each conductor is divided. , The shared voltage is detected. Since the voltage dividing electrodes are connected to each other, the respective shared voltages are combined to become a zero-phase voltage. This combined zero-phase voltage is applied to one voltage sensor head and converted into an optical signal. This optical signal is transmitted to the control unit by an optical fiber drawn from the device case. Therefore, it is sufficient for the control unit to convert the optical signal of one path into an electric signal.

Here, in normal times, the three phases are balanced and no zero-phase voltage signal is output. When a ground fault occurs, the zero-phase voltage signal, the current of each phase, and the zero-phase current signal are integrated to detect the fault.

[0008]

According to the present invention, the partial pressure case, which is attached closely to the inner surface of the metal equipment case into which the conductors of each phase are drawn and loosely fits the conductors of each phase, is formed by a hollow formed by the inner wall. An annular storage groove is formed between the portion and the outer wall provided concentrically outside the inner wall to form a cylindrical shape, and the voltage dividing electrode is formed in a loop along the inner wall inside the storage groove. And a ground electrode having an L-shaped cross section is disposed in a loop along the outer wall and covers the storage groove.
Further, a voltage dividing electrode and a ground electrode provided for each phase are connected to each other, and a capacitor for capacitance correction is connected between the voltage dividing electrode and the ground electrode. Since the optical fiber is pulled out of the device case from the voltage sensor head that converts the pressure voltage to the optical signal, the optical signal transmitted by the optical fiber is converted into an electric signal and transmitted to the control unit. A zero-phase voltage detection device that can be detected in one path, has a simple structure, and has few failures can be obtained, and the voltage applied to the conductor can be accurately divided.

[0009]

【Example】

(Embodiment 1) Hereinafter, an example in which the zero-phase voltage detecting device of the present invention is mounted on a switch 1 of a distribution line will be described in detail.
As shown in FIG. 2, the switch 1 is suspended from the hook metal 4 of the arm 3 of the utility pole, and the hanging metal 2 is hung. Three bushings 6 for drawing in the conductors U, V, W of the three-phase electric circuit are mounted in a horizontal line on outer shells before and after the device case 5 made of a non-magnetic metal of the switch 1.
These conductors U, V, and W are connected to open / close terminals (not shown) to open and close electric circuits.

A control box 7 is provided on one side of the equipment case 5.
And an opening / closing operation mechanism 8 for opening / closing an opening / closing terminal and an opening / closing control mechanism 9 for controlling the opening / closing operation are housed. On the outside of the control box 7, a manual operation lever 1 is attached to an operation shaft 10 for manually operating the opening / closing operation mechanism 8.
1 is provided so that the open / close terminal can be opened and closed. A signal line 13 is drawn out from the bottom of the control box 7 in an airtight manner by an electric connector 12. This signal line is connected to a control unit (not shown), and drives the opening / closing operation mechanism 8 based on a drive signal from the control unit to open and close the electric circuit.

Each of the bushings 6 is inserted into the equipment case 5 and pressure dividing cases 14a, 14b, and 14c are attached to the case. Each of the voltage dividing cases 14a, 14b, and 14c is formed in the same shape by insulating plastic, and is inserted into each of the bushings 6 of the conductors U, V, and W, and is formed with metal mounting screws 15 (see FIG. 3). Is attached to the equipment case 5 via a mounting flange 16 formed at the bottom.

The pressure dividing case 14b is formed in a thin cylindrical shape as shown in FIGS. 3 and 4, and the bushing 6 is inserted into a hollow formed by the inner wall 17. An outer wall 18 is provided concentrically outside the inner wall 17, and an annular storage groove 20 is formed between the inner wall 17 and the outer wall 18 by a bottom plate 19 at the bottom. The lower part of the storage groove 20 is opened, and the bottom plate 19 is provided to extend. A voltage-dividing electrode 21 made of a non-magnetic metal plate is provided in the storage groove 20 in a loop along the inner wall 17. The voltage dividing electrode 21 is provided with a connection terminal 23 and is connected to a capacitor 30 described later via a connection line 24. Similarly, a ground electrode 22 made of a band-shaped nonmagnetic metal plate is arranged in a loop along the outer wall 18. The ground electrode 22 has an L-shaped cross section, and is attached so as to cover the storage groove 20.

The end of the ground electrode 22 is attached to the outer wall 18 by a metal mounting screw 25.
And the mounting flange 16 are connected to the equipment case 5 by a ground wire 26 and are grounded. Therefore, the device case 5, the voltage dividing electrode 21 and the ground electrode 22 shield the four circumferences of the storage groove 20 except for an open lower part, and the two electrodes 21 and 22 are opposed to each other with a predetermined gap. Thus, the voltage applied to the conductor W can be accurately divided.

The connection terminal 23 of the voltage dividing electrode 21 is connected to the connection line 2
4 is connected to a voltage sensor head 31 for converting an applied voltage to an optical signal by a Pockels element via one end of a capacitor 30 for capacitance correction. The voltage sensor head 31 converts the line voltage divided by the capacitance C of the capacitor 30 between the voltage dividing electrode 21 and the ground electrode 22 into an optical signal by the Pockels effect. This optical signal is connected by an optical fiber 32 to a control unit 41 attached to the middle part of the telephone pole via an optical connector 33 attached to the bottom of the equipment case 5.

The left and right conductors U and W are provided with a voltage dividing case 1.
4a and 14c are respectively attached through the bushing 6. As shown in FIG. 5, these voltage dividing cases 14a and 14c have the same configuration as the voltage dividing case 14b, and are attached to the equipment case 5 by attaching screws 15 fastened to an attaching flange 16 formed on the outer edge. ing. The difference from the voltage dividing case 14b is that the capacitor 30 for capacitance correction and the voltage sensor head 31 are not mounted on the bottom plate 19 of the voltage dividing case 14b. The connection terminal 23 of the voltage dividing electrode 21 is connected to the capacitor 30 for capacitance correction of the voltage dividing case 14b by connection lines 34 and 35. For this reason, the partial pressure cases 14a, 14b, 1
The three voltage dividing electrodes 21 of 4c are connected to generate a potential difference due to the vector composite voltage of the three-phase alternating current. After the voltage dividing electrode 21, the ground electrode 22, the capacitor 30, the voltage sensor head 31, and the like are arranged and connected in the storage groove 20, the insulator (not shown) is filled and fixed.

As shown in FIG. 1, the voltage sensor head 31
Is provided with a light emitting module 43 for outputting a signal light power by a drive power supply unit 42. The light emitting module 43 receives the light signal polarized by the voltage sensor head 31 and converts it into an electric signal. A light receiving module 44 is provided. The converted electric signal is corrected and amplified by the correction amplification unit 45, and then transmitted from the zero-phase voltage signal output unit 46 to the control unit 48 via the signal line 47.

Next, the operation of this embodiment will be described.

The zero-phase voltage synthesized by the voltage dividing electrodes 21 provided for each phase is detected by the voltage sensor head 31.
In the voltage sensor head 31, the drive power supply unit 4 of the control unit 41
The light emitting module 43 emits light by the power supplied from the power supply 2, and supplies the input light to the voltage sensor head 31. Then, an optical signal corresponding to the combined voltage based on the voltage dividing electrode 21 is transmitted to the light receiving module 44 by the Pockels effect of the voltage sensor head 31 and is converted into an electric signal, and then the correction amplifier 4
5 to correct and amplify. For this reason, it is sufficient for the control unit 41 to process the optical signal of one path, so that the configuration is simplified and factors such as malfunctions can be reduced. The amplified electric signal is output from the zero-phase voltage signal output unit 46 and transmitted to the signal control unit 48 via the signal line 47. In normal times, since the voltage of each phase of the three-phase circuit is balanced, the combined value becomes zero and no voltage is detected.

As a result of the ground fault, the equilibrium state of the voltage of each phase is broken, and a voltage signal of the synthesized voltage is detected by the voltage sensor head 31 and transmitted to the signal control unit 48. In addition, the signal control unit 48 determines the occurrence of an accident based on the current signal detected by other means in addition to the zero-phase voltage signal.

(Embodiment 2) Embodiment 2 shows an example in which current detecting means of each phase is arranged in the zero-phase voltage detecting device of Embodiment 1. As shown in FIG. 6, in the second embodiment, the central voltage dividing case 14b has the same configuration as that of the first embodiment, and the current detecting device is attached to the left and right voltage dividing cases 14d and 14e. Since the voltage dividing case 14d and the voltage dividing case 14e have the same configuration, the voltage dividing case 14d will be described below.

As shown in FIG. 7, an annular magnetic core 50 having a rectangular cross section is housed in the housing groove 20 of the pressure dividing case 14d. The core 50 is notched at a lower portion to provide a gap 51. The head of a magnetic field sensor head 52 having a Faraday element is inserted into the gap 51 and is fixed with a screw 54 by a clamp 53. The magnetic field sensor head 52 detects a magnetic field due to the current flowing through the conductors U and W, and converts the passing light into an optical signal proportional to the intensity. Then, the converted optical signal is supplied to the optical fiber 55.
Is transmitted to the control unit 61 via the optical connector 33 provided in the device case 5. Since the core 50 is arranged concentrically with the conductors U and W arranged at the center of the bushing 6 and the head of the magnetic field sensor head 52 is inserted into the gap 51, the change in current can be detected accurately. can do. Further, since the detected current signal is converted into an optical signal, it is accurately transmitted that it is guided by the outside world.

As shown in FIG. 6, the control section 61 is provided with a light emitting module 63 driven by a drive power supply section 62. The light emitting module 63 receives a light signal by the magnetic field sensor head 52 and converts the light signal into an electric signal. Module 64
Is provided. The converted electric signal is corrected and amplified by the correction amplifier 65, and then the current signal output 66
Is transmitted to the control unit 48 via the signal line 47.

In the second embodiment, the voltage dividing case 14d, 1
By providing the magnetic field sensor heads 52 in each of the conductors 4e, not only the current flowing through the conductors U and W can be detected, but also the signal V in the signal detection section can be combined with the current signals flowing in the two phases by vector synthesis. Can also be detected.

In the first and second embodiments,
Since the device case 5, the voltage dividing electrode 21 and the ground electrode 22 are formed of a non-magnetic metal and shielded from being affected by other phases, the detection accuracy can be stabilized.

In the second embodiment, the voltage dividing case 14
By attaching d, 14b and 14e to the equipment case 5 of the switch 1, both signals for detecting each phase current and zero-phase voltage can be easily attached with a simple structure.

[Brief description of the drawings]

FIG. 1 is a circuit diagram.

FIG. 2 is a partially cutaway front view of a switch.

FIG. 3 is a partial sectional view of a partial pressure case.

FIG. 4 is a partial sectional view of a partial pressure case.

FIG. 5 is a partially cutaway side view of a partial pressure case.

FIG. 6 is a circuit diagram of a second embodiment.

FIG. 7 is a partial sectional view of a partial pressure case.

[Explanation of symbols]

 5: Device case 14a, 14b, 14e ... Voltage dividing case 21 ... Voltage dividing electrode 22 ... Ground electrode 30 ... Capacitor 31 ... Voltage sensor head 32 ... Optical fiber 41 ... Control unit 47 ... Signal line 48 ... Signal control unit U, V , W ... conductor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 15/06 G01R 15/24 G01R 29/16

Claims (1)

(57) [Claims] 1. A zero-phase voltage detecting device which combines a voltage applied to each phase of a three-phase circuit to detect a zero-phase voltage, and transmits the detected zero-phase voltage signal to a control unit via a signal line. The partial pressure case, which is closely attached to the inner surface of the metal equipment case into which the conductor of each phase is drawn and loosely fits the conductor of each phase, has a hollow portion formed by the inner wall and an outer side of the inner wall. An annular storage groove is formed between the outer wall and the outer wall provided concentrically, the storage groove is formed in a cylindrical shape, and a voltage dividing electrode is disposed in a loop along the inner wall in the storage groove and has an L-shaped cross section. A ground electrode is disposed in a loop along the outer wall and covers the storage groove, and further connects the voltage-dividing electrode and the ground electrode provided for each phase to each other, A capacitor for capacitance correction is connected between the voltage dividing electrode and the ground electrode, An optical fiber is pulled out of a device case from a voltage sensor head that converts a divided voltage into an optical signal in parallel with a capacitor, and a zero-phase that converts an optical signal transmitted by the optical fiber into an electric signal and transmits the electric signal to a control unit. Voltage detector.