JPS62214369A - Zero-phase voltage detector - Google Patents

Abstract

PURPOSE:To obtain a detector which is easily fitted and low in manufacture cost by piercing three window holes at the top surface of a shield container and arranging plate type detection electrodes which are supported at every phase on rod type support members made of insulating materials in the container. CONSTITUTION:The three insulating support members 6 are fixed in the shield container C at positions corresponding to the window holes 5u-5w provided to the lid of the container. The flat plate type detection electrodes 7u-7w corresponding to respective power distribution lines Lu-Lw are fixed to the upper end parts of the members 6. Those electrodes 7u-7w are connected to lead wires R by connectors, etc., through branch lead wires Ru-Rw and led out to a signal processing circuit in a detector box K. In this constitution, a displacement current conducted from an electrostatic charging part through a space is utilized to simplify the structure of the detection part and also manufacture the detection electrodes for the three phases integrally, and further facilitates the opposite fitting operation of the detection part to the electrostatic charging part.

Description

[Detailed description of the invention] purpose of invention (Industrial application field) This invention relates to a zero-phase voltage detector.

(Prior art) In the conventional zero-sequence voltage detection method, the voltage sensor attached to the distribution line is a potential transformer (hereinafter referred to as PT) or a capacitor-divided voltage transformer (hereinafter referred to as PD). ) have been used, and in recent years, products other than PT that apply optoelectronic technology have also been proposed. The optoelectronic technology is called an optical power transformer (hereinafter referred to as optical PT), and many of them are being researched. This light PT is produced by placing an element with the Pockels effect in an electric field, and when linearly polarized light is incident on it in the same direction as the electric field, the curvature index for the two orthogonal components changes differently with the strength of the electric field and propagates. This method takes advantage of the fact that the speeds are different, and as a result, a phase difference occurs between two orthogonal components of light, and the emitted light becomes elliptically polarized light.

(Problems to be Solved by the Invention) The conventional PT or PD as described above is a contact type in which it is attached directly to a charged part of a cable, etc. for power distribution lines, and therefore it is necessary to consider insulation. Not only that, PT, P
In D, coil, iron core.

The use of capacitors and the like increases the overall size and weight of IT, which poses a problem in that it takes time and effort to install.

In addition, the latter optical PT is a non-contact type,
Although it has excellent insulation properties, it requires a laser oscillator or the like to obtain linearly polarized light, and there is a problem that the device as a whole becomes expensive.

Although the above-mentioned zero-phase voltage detector has become lightweight and relatively inexpensive, it is necessary to provide a detection part for each phase, making installation complicated and requiring a large number of parts. There still remained problems in terms of manufacturing costs. Therefore, it has been desired to realize a zero-sequence voltage detector that is easy to install and has a lower manufacturing cost. The present invention has been made in view of this point, and its object is to provide a zero-sequence voltage detector that is easy to install and has low manufacturing costs.

Structure of the Invention (Means for Solving Problems) In order to achieve the above-mentioned object, the present invention provides three window holes through the upper surface of an electrically grounded shielding container made of a conductive member. A plate-shaped detection electrode supported for each phase by a rod-shaped support member made of an insulating material is disposed in the container, and each window hole is connected to the container on the upper surface of each detection electrode. The branch lead wires Ru, Rv, and Rw are connected to each of the detection electrodes and led out, and are connected to the lead wire R using a connector or the like. The branch lead wires Ru, Rv
, Rw or the lead wire R is provided with a signal processing circuit including an amplifier circuit and a bandpass filter.

(Function) By adopting the above-mentioned means, the present invention not only has a simple structure of the detection part by utilizing the displacement current flowing from the charged part through the space, but also integrates three phases into one. It is easy to manufacture, and it is easy to mount the detection section opposite to the charging section.

(Example) The first example embodying the present invention will be described below in Figures 1 to 6.
The details will be explained according to the figures.

A shield container C of a voltage sensor S that is placed apart from three-phase power distribution lines Lu, Lv, and Lw is composed of a case 1 having a channel-shaped cross section and a lid 2 that is placed over the case 1.

As shown in FIG. 3, mounting pieces 3 are formed by bending inward at right angles at both ends of the side walls and both ends of the bottom wall of the case 1, which face each other. Further, as shown in FIG. 2, the lid 2 of the shield container C has a reverse channel shape so as to cover the upper part of the opening length d at both ends of the case 1, and the lid 2 of the shield container C has a reverse channel shape so as to cover the upper part of the opening length d at both ends of the case 1. It is fastened to the mounting piece. The lid 2 has first window holes 5u, 5v, and 5w each having a rectangular shape and serving as a displacement current inflow portion.
Three of them are lined up and transparently installed in the length direction so as to correspond to each of the distribution lines Lu, Lv, and Lw shown in the figure. In the shield container C, the case 1 has 3 f[! An insulating support member 6 is fixedly installed at the upper end of the support member 6 for each distribution line Lu, Lv.
.

Flat detection electrodes 7u, 7v, and 7W corresponding to Lw are fastened and fixed by screws 11, respectively.

The shield container C is made of a conductive material such as aluminum, and serves as a shield electrode for the detection electrodes 7u, 7v, and 7W.

The detection electrodes 7u, 7v, and 7w are made of a conductive member such as metal, conductive resin, or conductive rubber, and in this embodiment, aluminum, which is easy to process, is used. Then, as described above, the support member 6 and the detection electrodes 7u, 7 are attached to the case 1.
After the detection electrodes 7u and 7w are assembled, these detection electrodes 7u and 7v
, 7w are connected to a lead wire R via a connector or the like via branch lead wires Ru, Rv, and Rw, and are led out to a signal processing circuit 9 to be described later.

The signal processing circuit 9 will be explained according to FIG. 4. The signal processing circuit 9 is housed in a detector box together with a power supply circuit 20, which will be described later, and is roughly divided into an amplifier circuit A.
and a bandpass filter circuit B.

When the amplifier circuit A receives the combined displacement current from the detection electrodes 7u, 7v, and 7w, it amplifies the displacement current and outputs a waveform similar to the displacement current. It is composed of That is, the input terminal P1 of the signal processing circuit 9 is connected to the ground wire E1 via the resistor R1, and the shield container C is connected to the branch lead wire Ru.
, Rv.

Rw and the lead wire R are connected to the grounding wire E1 via the terminal P2 with a shielded braided wire by a method such as using a single-core shielded electric wire. A pair of diodes Di, D oriented in opposite directions are connected between both terminals of the resistor R1.
Two parallel circuits are connected, and the detection electrodes 7u, 7v, and 7w serve as a protection circuit to prevent excessive human power.

The resistor R1 is connected to the inverting input terminal of the operational amplifier OPI, and the non-inverting input terminal of the operational amplifier OPI is connected to the ground line E1 via the resistor R3. A parallel circuit including a capacitor C1 and a resistor R4 is connected between the inverting input terminal and the output terminal of the operational amplifier OPI.

Note that the capacitors C2 and C3 are used to stabilize the power supply of the operational amplifier OPI.

The resistors R1 to R4, the diode DI, the D2° capacitor C1, and the operational amplifier OPI constitute an amplifier circuit A, and the output terminal of the amplifier circuit A is connected to a bandpass filter B at the next stage.

The band pass filter B is set to selectively amplify and extract a frequency of 60 Hz or 50 Hz as a center frequency based on the applied signal when a signal similar to the displacement current sent from the amplifier circuit A is applied. , Specifically, it is structured as follows.

That is, the output terminal of the amplifier circuit A and the operational amplifier 5OP
A series circuit of a capacitor C4 and a resistor R5 is connected between the inverting input terminals of the operational amplifier OP2, and the non-inverting input terminal of the operational amplifier OP2 is connected to the ground line E1 via a resistor R6. A series circuit of capacitors C5 and C6 and resistors R7 and R8 are connected between the inverting input terminal and the output terminal of the operational amplifier OP2.
A parallel circuit consisting of a series circuit and a series circuit are connected. Further, a capacitor C7 is connected between a point a between the resistors R7 and R8 and the ground line E1. A resistor R is connected between the output terminal of the operational amplifier OP2 and the output terminal 23 of the signal processing circuit 9.
9 is connected.

A bandpass filter B is constituted by the resistors R5 to R8, the capacitors C4 to c7, and the operational amplifier OP2.

Next, the power supply circuit 20 will be explained according to FIG. 5. A power transformer 21 is connected to the 100VAC power terminal, and a full-wave rectifier 22 is connected to the secondary side of the power transformer 21.
is connected. A grounding wire E2 is connected to point b on the secondary side of the power transformer 21, and a smoothing capacitor c8 is connected between the positive terminal of the full-wave rectifier 22 and the grounding wire E2.
and a capacitor C9 are connected.

Further, a three-terminal regulator 23 is connected between the positive terminal of the full-wave rectifier 22 and the ground wire E2, and the output terminal of the three-terminal regulator 23 is connected to the +Vcc terminal, and the output terminal of the three-terminal regulator 23 is connected to the +Vcc terminal. A capacitor CIO and a capacitor C are connected between the terminal and the ground wire E2.
1l is connected.

In addition, the negative terminal of the full-wave rectifier 22 and the grounding wire E2
A smoothing capacitor C12 and a capacitor C13 are connected between
is connected. Further, a three-terminal regulator 24 is connected between the negative terminal of the full-wave rectifier 22 and the ground wire E2, and the output terminal of this three-terminal regulator 24 is -V
It is connected to the cc terminal, and the three-terminal regulator 2
A capacitor C14 is connected between the output terminal of 4 and the ground wire E2.
and a capacitor C15 are connected.

Now, the operation of the zero-sequence voltage detector configured as above will be explained.

In Fig. 1, when a steady load current is flowing through each distribution line Lu, Lv, Lw, the capacitance Cu formed between the distribution lines Lu, Lv, Lw and the ground, which is a reference potential point, is
The displacement current flowing through Cv and Cw passes through the window holes 5u, 5v, and 5w of the voltage sensor S as a displacement current inflow part to the detection electrode 7u.

It is collected by 7v and 7w.

After this displacement current is combined, the signal processing circuit 8
The amplifier circuit A amplifies the displacement current, and passes the waveform similar to the displacement current to the bandpass filter B.
Output to. In this case, the input impedance seen from the terminals Pi and P2 is considered to be a parallel value of resistors R1 and R2. As is well known, in typical applications of operational amplifiers, the resistance R2 has a value on the order of Ω. Also, the closed loop gain R
4/R2 is set to about 1000 to obtain sufficient output.

Therefore, the above-mentioned input impedance is effectively kept at a sufficiently low value by the resistor R2, yet a large signal is available at the output of the operational amplifier opi due to the high closed-loop gain. As is well known, the phase difference between the input and output of the operational amplifier OPI changes depending on the magnitude relationship between the impedances of the resistor R4 and the capacitor C1, and if the former is relatively small, the phase difference is ignored and the output is proportional to the displacement current. can get. In the opposite case, an integral value, ie a value proportional to the potential of the distribution line, is obtained. In any case, this output has a waveform similar to the displacement current.

Next, when a signal similar to the displacement current is applied, the bandpass filter B operates at a frequency of 60+1 based on the signal.
A signal whose center frequency is z or 50)1z is selectively amplified and extracted, and a zero-phase voltage 0 signal is output to the output terminal P (see FIG. 6). In this Figure 6, α, β,
T is each distribution line Lu.

This is the waveform of the voltage applied to LV, l, and w.

In this way, since the ground voltages of each phase are normally balanced, the zero-sequence voltage 0 obtained by combining the voltages of the three detection electrodes 7u, 7v, and 7W is O.

Next, if a ground fault occurs in any one phase of the distribution lines Lu, Lv, and Lw, the balance between the ground voltages of each phase will be disrupted, so the three-phase detection electrode 7u.

After the combined voltage of 7V and 7W is input to the signal processing circuit 9, a signal corresponding to the input voltage is outputted, and a zero-phase voltage is detected. As a result, it is detected that a ground fault has occurred in the power distribution line.

In addition, the shield capacity 'lAC of the voltage sensor S is such that the case 1 and the lid 2 serve as shield electrodes, and in order to prevent the inflow of displacement current from sources other than the distribution line that is the object to be measured,
There is no adverse effect from other power distribution lines other than the power distribution line that is the object to be measured.

Next, a second embodiment of the present invention will be described in detail with reference to FIGS. 7 and 8.

In this embodiment, as shown in FIG. 7, the lead wires of three-phase detection electrodes 7u, 7v, and 7w are not connected to each other, but are connected to an adder circuit 25 provided inside the detector box together with a power supply circuit 20. However, this adder circuit 25 is configured to combine three-phase voltages.

The adder circuit 25 is configured to synthesize signals output from the respective output electrodes 7u, 7v, and 7W and selected at a predetermined frequency, and output a zero-phase voltage Vo to its output terminal Po. The specific configuration of the adder circuit 25 will be described below with reference to FIG.

That is, the output terminals pv, pu of the detection electrodes 7u, 7v, 7w are connected to the inverting input terminal G of the operational amplifier OP3 via variable input resistors RIO, R11°R12, respectively.
, Pw are connected, and their non-inverting input terminals are grounded via a resistor R13. Further, the output terminal of the operational amplifier OP3 is connected to the point G via a resistor R14. Further, the output terminal of the operational amplifier OP3 is connected to the output terminal Po via a voltage follower using an operational amplifier OP4 and a resistor 15. This voltage follower converts impedance by increasing input impedance and decreasing output impedance.

The resistors RIO to R15 and operational amplifier OP 3°0P
4 constitutes an adder circuit 25.

Further, the addition circuit 25 is housed in a detector box together with the power supply circuit 20 to constitute a zero-phase voltage detector 26, but the configuration of the power supply circuit 20 is the same as that of the first embodiment. , the explanation thereof will be omitted.

Next, a third embodiment of the present invention will be described with reference to FIG.

In this embodiment, the shield container C is formed into a channel-shaped cross section, the bottom part is omitted, and three-phase detection electrodes 7u and 7v are formed.
, 7w are suspended from the inside of the upper surface of the shield container C via a pair of insulating support members 27, respectively. Insulating folds 28 are formed on the insulating support member 27 to form detection electrodes 7u and 7v.

From 7W onwards, the leakage of the current flowing into the shield electrode is reduced. Further, as in the second embodiment, each of the detection electrodes 7u, 7v, 7w is connected to an adder circuit 25 in the zero-phase voltage detector 26, and after the voltages are combined in the adder circuit 25, A zero-phase voltage Vo is output to the output terminal P.

Effects of the Invention As detailed above, the present invention has three transparent windows in the upper surface of the electrically grounded shield container made of a conductive material, and an insulating material inside the container. plate-shaped detection electrodes supported for each phase by rod-shaped support members made of At the same time, the branch lead wires Ru, Rv, and Rw connected to each of the detection electrodes and led out are connected to the lead wire R with a connector or the like, and the branch lead wires Ru, Rv, and Rw or the lead wires are By disposing a signal processing circuit consisting of an amplifier circuit and a bandpass filter on at least one lead wire of R, manufacturing costs can be reduced and installation is easy.

[Brief explanation of drawings]

FIG. 1 is an overall view of a zero-phase voltage detector according to a first embodiment embodying the present invention, FIG. 2 is a sectional view of the voltage sensor, and FIG. 3 is an exploded perspective view of the voltage sensor excluding the molding material. Figure 4 is an electric circuit diagram of the amplifier circuit and filter, Figure 5 is an electric circuit diagram of the detection circuit of the zero-phase voltage detector, and Figure 6 is the electric circuit diagram of the zero-phase voltage detected by this zero-phase voltage detector and each Voltage oscilloscope of phase distribution line, Fig. 7 is an overall diagram showing the second embodiment, Fig. 8 is an electric circuit diagram also showing the second embodiment, and Fig. 9 is a diagram showing the third embodiment.
FIG. Shield container C1 window holes 5u, 5v, 5w, support member 6,
Detection electrodes 7u, 7v, 7w, signal processing circuit 9, amplifier circuit A, bandpass filter B1 lead wire R1 branch lead wires Ru, Rv, Rw. Patent applicant: Nippon Insulators Co., Ltd. Takamatsu Electric Manufacturing Co., Ltd.

Claims (1)

[Claims] 1. Three window holes are made through the upper surface of an electrically grounded shielding container made of a conductive material, and a rod-shaped support member made of an insulating material is installed inside the container for each phase. Supported plate-shaped detection electrodes are arranged, each of the window holes is arranged on the upper surface of each detection electrode so as to be closed with a gap between them and the inner surface of the container, and is connected to each of the detection electrodes. The branch lead wires Ru, Rv, and Rw are connected to the lead wire R using a connector or the like, and an amplifier circuit is connected to at least one of the branch lead wires Ru, Rv, and Rw, or the lead wire R. A zero-phase voltage detector characterized in that it is equipped with a signal processing circuit consisting of a bandpass filter.