JPH0668505B2 - Voltage sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention (Field of Industrial Application) The present invention relates to a voltage sensor.

(Prior Art) Conventionally, as a method for detecting an AC voltage, an instrument transformer (hereinafter referred to as PT) or a capacitor voltage dividing type instrument transformer (hereinafter referred to as PD) is generally used at a commercial frequency. There is.

(Problems to be Solved by the Invention) The conventional PT or PD as described above is a contact type that is directly attached to a charging portion such as a cable with respect to a power distribution line, and therefore insulation must be considered. Not only PT, P
In D, since a coil, an iron core, a capacitor and the like are used, there is a problem that the whole becomes large and the weight becomes heavy. Therefore, there is a problem that the mounting work is troublesome.

The present invention has been made in order to solve the above-mentioned problems, and can be arranged separately from the charging section, and the signal waveform similar to the charging section potential can be accurately measured with a simple and inexpensive structure. It is an object of the present invention to provide a collector electrode of a voltage sensor that can be used.

Structure of the Invention (Means for Solving the Problems) In order to solve the above problems, the present invention is arranged with a predetermined gap with respect to an upper power distribution line, and a window is formed on the upper surface. A box-shaped shield electrode, which can face the power distribution line through the window in the shield electrode, and which is hung and supported by an insulating support member from the upper surface of the shield electrode without contacting each inner surface of the shield electrode. A flat plate-shaped detection electrode is provided, and a lead wire connected to the detection electrode is provided with a signal processing circuit including an amplifier circuit and a bandpass filter.

(Operation) With the above configuration, the voltage of the charging section is detected without being affected by the other charging section by the detection electrode arranged apart from the charging section and the shield electrode having the detection electrode therein. Further, since the detection electrode is suspended and supported by the insulating support member protruding from the lower surface of the shield electrode, even if rainwater enters from the displacement current inflow portion, rainwater will directly adhere to the surface of the insulating support member. The leakage current flowing through the surface of the insulating support member is reduced.

(Embodiment) An embodiment in which the present invention is embodied in a voltage sensor of a zero-phase voltage detecting device will be described below with reference to FIGS. 1 to 6.

60Hz or 50Hz phase distribution lines Lu, Lv, Lw
A voltage sensor S that is arranged at a substantially equal distance from the voltage sensor S
Since u, Sv, and Sw have the same configuration, the voltage sensor Su will be described. This voltage sensor Su is composed of a detection unit 7 and a signal processing circuit 8.

The case 1 of the detection part 7 is formed in a channel shape in cross section, and the detection electrode support parts 2 of reverse channel shape in cross section are bent inward at the upper ends of both side walls 1a facing each other.
Further, mounting pieces 3 are bent inward at right angles on both side portions of the side wall 1a and both end portions of the bottom wall. A lid 4 formed in a reverse channel shape so as to cover both end openings and an upper portion of the case 1 is fixed to the mounting piece 3 of the case 1 with screws 4a inserted from both end walls thereof.
On the upper surface of the window 5 as a displacement current inflow portion having a rectangular shape
Is transparently installed. The case 1 and the lid 4 are formed of a conductor such as aluminum into a box shape, and the detection electrode 1 described later is used.
It is a shield electrode containing 0.

A flat plate-shaped detection electrode 10 is suspended and supported on the upper surface of the central portion of the case 1 through columnar insulating support members 6 projecting from both ends of the inner surface of the detection electrode support portion 2, and then, on a screw 11. It is fixed. Further, the insulating support member 6
A plurality of insulating folds 6a are formed on the surface so as to project in an annular shape to increase the insulating distance between the insulating support member 6 and the detection electrode 10. Further, the detection electrode 10 is arranged parallel to the lid 4 below the lid 4 and corresponding to the window 6, and is housed at a predetermined interval without contacting each inner surface of the shield electrode. ing. As a result, the detection electrode 1
0 is in a state in which the periphery thereof is covered by the shield electrode except for the window 5. The detection electrode 10 is made of a conductive material such as metal, conductive resin, conductive rubber or the like, and in this embodiment, aluminum which is easy to process is used.

As shown in FIG. 1, the detection unit 7 is composed of the case 1, the lid 4, the detection electrode 10 and the like, and the detection unit 7 corresponds to each phase electric line Lu, Lv, Lw serving as a charging unit for each phase. They are spaced apart at substantially equal distances. Therefore, the detection electrodes 10 of the detection unit 7 arranged for each phase pass through the window 5 and the electric wire L for each phase.
u, Lv, and Lw are opposed to each other at a predetermined interval.

One end of a lead wire 31 is connected to the detection electrode 10 of the detection section 7, and the lead wire 31 is led out from the case 1 and connected to a zero-phase voltage detector 20 via a signal processing circuit 8 described later. The signal processing circuit 8 includes voltage sensors Su, S
Since v and Sw have the same configuration, the signal processing circuit 8 connected to the detection electrode 10 will be described.

The signal processing circuit 8 is roughly divided into an amplifier circuit A and a bandpass filter B.

When the displacement current from the detection electrode 10 is input, the amplification circuit A amplifies the displacement current and outputs a waveform similar to the displacement current. Specifically, it is configured as follows. . That is, the input terminal P of the signal processing circuit 8
1 is connected to the ground line E1 via the resistor R1, and the case 1 and the lid 4 forming the shield electrode are connected to the ground line E1 via the terminal P2. A parallel circuit of a pair of diodes D1 and D2 facing in opposite directions is connected between both terminals of the resistor R1 to form a protection circuit for preventing an excessive input from the detection electrode 10.

The input terminal P1 is connected to the operational amplifier OP1 via the resistor R2.
Of the operational amplifier O.
The non-inverting input terminal of P1 is connected to the ground line E1 via the resistor R3. A parallel circuit of a capacitor C1 and a resistor R4 is connected between the inverting input terminal and the output terminal of the operational amplifier OP1. The capacitors C2 and C3 are for stabilizing the power supply of the operational amplifier OP1.

An amplifier circuit A is composed of the resistors R1 to R4, the diodes D1 and D2, the capacitor C1 and the operational amplifier OP1.

The band-pass filter B is set so that when a signal similar to the displacement current is applied from the amplifier circuit A, it selectively amplifies and takes out with a frequency of 60 Hz as the center frequency based on the signal. Is configured as follows. That is, the series circuit of the capacitor C6 and the resistor R5 is connected between the output terminal of the operational amplifier OP1 and the inverting input terminal of the operational amplifier OP2, and the non-inverting input terminal of the operational amplifier OP2 is grounded via the resistor R6. It is connected to E1. Between the inverting input terminal and the output terminal of the operational amplifier OP2, a series circuit of capacitors C4 and C5 and a resistor R
A parallel circuit composed of a series circuit of 7 and R8 is connected. A capacitor C7 is connected between the point R and the ground line E1 between the resistors R7 and R8.

The resistors R5 to R9, the capacitors C4 to C7, and the operational amplifier OP2 constitute a bandpass filter B, and the output terminal of the bandpass filter B is connected to the output terminal Pu. Then, the detection electrodes 10,
A voltage sensor Su is configured by the signal processing circuit 8. The output terminals of the other voltage sensors Sv and Sw are represented by Pv and Pw instead of Pu for convenience of description.

The voltage sensors Su, Sv, Sw arranged on the distribution lines Lu, Lv, Lw of the respective phases are connected to the zero-phase voltage detector 20, and the detection circuit 21 incorporated in the zero-phase voltage detector 20 includes It is composed of an adding circuit 22, an adding circuit 22, and a power supply circuit 23 for the voltage sensor.

The adder circuit 22 is adapted to combine the signals selected from the voltage sensors Su, Sv, Sw with a predetermined frequency and output the _zero phase voltage V ₀ signal to the output terminal P thereof. Specifically, the adder circuit 22 is as follows.

That is, at the point G of the inverting input terminal of the operational amplifier OP3, output terminals Pu, P of the voltage sensors Su, Sv, Sw are respectively connected via variable input resistors R11, R12, R13.
v and Pw are connected, and the non-inverting input terminal is a resistor R
It is grounded through 14.

The output terminal of the operational amplifier OP3 is connected to the point G via the resistor R15.

Further, the output terminal of the operational amplifier OP3 is an operational amplifier O
A voltage follower using P4 and a resistor R16 are connected to the output terminal P. This voltage follower raises the input impedance and lowers the output impedance to convert the impedance.

The resistors R11 to R16 and operational amplifiers OP3 and OP4
The adder circuit 22 is configured by.

Explaining the power supply circuit 23, the power supply voltage AC100
A full-wave rectifier 25 is connected to the secondary side of the power transformer 24 whose primary side is connected to V. A ground line E2 is connected to a point d on the secondary side of the power transformer 24, and smoothing capacitors C14 and C15 are connected between the positive terminal of the full-wave rectifier 25 and the ground line E2. .

A three-terminal regulator 26 is connected between the positive terminal of the full-wave rectifier 25 and the ground line E2, the output terminal of the three-terminal regulator 26 is connected to the + Vcc terminal, and the output terminal of the three-terminal regulator 26 is grounded. A capacitor C8 and a capacitor C9 are connected between the line E2.

A smoothing capacitor C10 and a capacitor C11 are connected between the negative terminal of the full-wave rectifier 25 and the ground line E2. A three-terminal regulator 27 is connected between the negative terminal of the full-wave rectifier 25 and the ground wire E2.
The output terminal of the three-terminal regulator 27 is connected to the -Vcc terminal, and the capacitors C12 and C13 are connected between the output terminal of the three-terminal regulator 27 and the ground line E2.

Now, the operation of the zero-phase voltage detecting device configured as described above will be described.

In FIG. 3, the distribution lines Lu, Lv of each phase as the charging unit,
Corresponding to Lw, the voltage sensors Su, Sv, Sw are arranged at substantially the same distance. When a three-phase voltage according to normal phase rotation is applied to the distribution line, electrostatic capacitances Cu, Cv, formed between the distribution lines Lu, Lv, Lw and the ground, which is the reference potential point, respectively. The displacement current flowing through Cw is collected by the detection electrode 10 through the window 5 of each voltage sensor Su, Sv, Sw.

Then, this displacement current is applied to each of the voltage sensors Su, Sv, Sw.
In the signal processing circuit 8, the amplification circuit A amplifies the displacement current and outputs a waveform similar to the displacement current to the bandpass filter B.

In this case, the input impedance seen from the terminals P1 and P2 is considered to be the parallel value of the resistors R1 and R2. In a typical use case of an operational amplifier, R2 has a value on the order of KΩ. The closed loop gain R4 / R2 is set to about 1000 in order to obtain a sufficient output. Further, R1 is set to a value lower than the creeping leakage resistance of the insulating support member 6 that supports the detection electrode 10 and is used for stabilizing the input or finely adjusting the output, but the value is in the order of 10 KΩ or more. is there. Therefore, the above input impedance is effectively kept at a sufficiently low value by R2, and a large signal is obtained at the output of the operational amplifier OP1 due to the high closed loop gain. As is well known, the phase difference between the input and output of the operational amplifier OP1 changes depending on the magnitude relationship between the impedances of the resistor R4 and the capacitor C1. If the former is relatively small, the phase difference is ignored and an output proportional to the displacement current is output. can get.
In the opposite case, the phase difference is close to 90 °, and an integrated value of the displacement current, that is, a value proportional to the potential of the wiring line is obtained at the output. In any case, a waveform similar to the displacement current is obtained at this output.

Next, when a signal similar to the displacement current is applied, the bandpass filter B selectively amplifies and extracts a symbol having a center frequency of 60 Hz based on the signal. Then, the adder circuit 22 of the zero-phase voltage detector 20 synthesizes the signals selected from the voltage sensors Su, Sv, Sw with the predetermined frequency and outputs the _zero- phase voltage V ₀ signal to the output terminal P thereof. (See FIG. 6). In FIG. 6, α,
β and γ are the waveforms of the voltage applied to the wires installed in each phase.

As described above, in a normal case, the ground voltage of each phase is balanced, so that the zero-phase voltage V ₀ obtained by combining in the adding circuit 22 is zero.

Next, if a ground fault occurs in any one of the distribution lines Lu, Lv, and Lw, the ground voltage of each phase is unbalanced, and therefore the signal processing circuit 8 of each voltage sensor Su, Sv, Sw. When the signals output from the zero-phase voltage detector 20 through the above are combined in the adding circuit 22, the zero-phase voltage is detected.
As a result, it is detected that a ground fault has occurred in the distribution line.

Further, in the voltage sensors Su, Sv, Sw, the case 1 and the lid 4 serve as shield electrodes, and in order to effectively prevent the inflow of displacement current from other than the distribution line which is the object to be measured,
Virtually no adverse effects of the distribution lines other than the distribution line that is the object to be measured.

However, although slightly, displacement currents of other phases having different phases also flow into the voltage sensors Su, Sv, Sw. Also,
The effective gains of the phase voltage sensors Su, Sv, Sw also have some differences. In such a case, a zero-phase output is generated at the output terminal P even if the ground voltage of each phase is balanced. Therefore, the resistors R11, R12, and R13 are changed so that the zero-phase output approaches zero as much as possible. Adjust to.

Further, since the insulating support member 6 is supported by the insulating support member 6 projecting from both ends of the inner surface of the detection electrode support portion 2 formed in the reverse channel shape in cross section with respect to the upper portion of the case 1, rainwater enters through the window 5. However, rainwater does not directly adhere to the surface of the insulating support member 6, and the leakage current flowing through the surface of the insulating support member 6 is reduced.

Furthermore, since the insulating fold 6a is provided on the surface of the insulating support member 6 that supports the detection electrode 10, the insulation distance between the detection electrode 10 and the case 1 and the lid 4 as the shield electrode becomes long. The leakage current through the surface of the insulating support member 6 can be reduced.

In addition, since rainwater, dust, etc. do not easily adhere to the lower surface of the insulating folds 6a and the portion between the insulating folds 6a and the insulating folds 6a,
The support member has excellent anti-fouling performance, and leakage current due to the fouling can be reduced, so that accurate voltage detection can be performed.

EFFECTS OF THE INVENTION As described in detail above, according to the present invention, the detection electrode is housed in the shield electrode so as to cover the other portion except the portion corresponding to the displacement current inflow portion. The target voltage of the charging portion can be accurately measured without being affected by Further, since the detection electrode is suspended and supported through the insulating support member of the shield electrode, even if rainwater enters from the displacement current inflow portion, rainwater does not directly adhere to the surface of the insulating support member, Leakage current through the surface of the insulating support member is reduced.

In addition, since a non-contact method in which the charging unit is arranged apart from the charging unit can be adopted, it is possible to provide an accurate voltage sensor having a simple structure, a low cost, and the like, which is excellent in industrial use.

[Brief description of drawings]

FIG. 1 is a sectional view of a voltage sensor showing a first embodiment of the present invention, FIG. 2 is an exploded perspective view of the voltage sensor, FIG. 3 is an overall view of a zero-phase voltage detecting device, and FIG. Electric circuit diagram, FIG. 5 is an electric circuit diagram of the detection circuit of the zero-phase voltage detector,
FIG. 6 is a voltage oscillograph of the zero-phase voltage detected by the zero-phase voltage detecting device and the electric wire provided for each phase. 1 ... Case, 4 ... Lid, 5 ... Displacement current inflow section, 6 ...
... Insulating support member, 10 ... Detection electrode, 20 ... Zero-phase voltage detector, 21 ... Detection circuit, A ... Amplification circuit, B ... Band pass filter, E1, E2 ... Ground wire, OP1 to OP
P4 ... Operational amplifier, R1-R16 ... Resistors, C1-C
15 ... Capacitor, P1 ... Input terminal, P2 ... Terminal, Pu, Pv, Pw ... Output terminal, Cu, Cv, Cw
...... Capacitance, Lu, Lv, Lw ...... Distribution line.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Tanahashi, No. 1, Kamikokonee, Inuyama, Aichi Prefecture Takamatsu Denki Seisakusho Co., Ltd. (56) References JP-A-51-114167 (JP, A) -172877 (JP, U)

Claims (1)

[Claims] 1. A box-shaped shield electrode, which is spaced apart from an upper power distribution line with a predetermined gap and has a window on its upper surface, and a power distribution line in the shield electrode via the window. And a flat plate-shaped detection electrode suspended and supported by an insulating support member from the upper surface of the shield electrode without contacting each inner surface of the shield electrode,
Further, the lead wire connected to the detection electrode is provided with a signal processing circuit including an amplifier circuit and a band pass filter.