JPS62214361A - Voltage sensor - Google Patents

Abstract

PURPOSE:To obtain an inexpensive sensor of simple constitution which performs accurate detecting operation by arranging a detection electrode supported by an insulating material in a shield case which is made of a conductive member and grounded. CONSTITUTION:A window hole 5 is bored in the top surface of the shield container 1 which is made of the conductive member and electrically grounded and the plate type detection electrode 10 which is supported by the thin rod type support member 6 made of the insulating material is arranged in the container 1. The window hole 5 is closed with the top surface of the detection electrode 10 while a gap is left opposite the internal surface of the container. The detection electrode 10 is connected to a signal processing circuit composed of an amplifying circuit and a BPF. The sensor arranged at distance from an electrostatic charging part such as a power distribution line is not affected by other electrostatic charging parts because the detection electrode 10 faces it across the window hole 5 of the shield container 1. The window hole 5 is closed at the time of outdoor use, so rain and foil matter are prevented from entering the shield container 1.

Description

[Detailed description of the invention] purpose of invention (Industrial application field) TECHNICAL FIELD This invention relates to voltage sensors.

(Conventional Techniques Wi) Traditionally, as a method for detecting alternating current voltage, a potential transformer (hereinafter referred to as PT) or a capacitor voltage division type potential transformer (hereinafter referred to as PD) is generally used at commercial frequencies. ing.

(Problems to be Solved by the Invention) The conventional PT or PD as described above is a contact type that is attached to a charged part of a cable, etc., which is not directly connected to a distribution line.
Therefore, not only is it necessary to consider insulation, but also PT,
f) In D, coil, iron core.

The use of capacitors, etc. increases the overall size and weight, which makes the removal process time-consuming, so the detection electrode is placed between the electrically charged parts such as distribution lines and the space. A detection means has been invented that utilizes the displacement current flowing from the charging section via the capacitance of the space. However, when using this voltage sensor, it is necessary to consider a wide range of FIRs, such as indoors and outdoors or areas with JG dust, and avoidance of the influence of rainwater on the detection output is particularly problematic.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a voltage sensor that is simple in construction, inexpensive, and provides accurate detection operation. Structure of the Invention (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a transparent window hole in the upper surface of an electrically grounded shield container made of a conductive member, and A plate-shaped detection electrode supported by a thin rod-shaped support member made of an insulating material is arranged on the container, and the window hole is connected to the upper surface of the detection electrode with a gap between it and the inner surface of the container. In the voltage sensor of the present invention, which is arranged at a distance of 1 mm from one part of a belt of a distribution line, etc., the detection electrode is placed in the window hole of the shield container. Because they face each other through the shield, they are not affected by other charged parts, and when used outdoors, the detection electrode is placed so as to close the window hole, preventing rainwater or The intrusion of contaminants is prevented, and the adhesion of rainwater or contaminants to the support member located on the back side of the detection electrode is suppressed.Since the support member is thin and rod-shaped, its surface area is small, and rainwater is prevented from entering. Even if it does adhere, the area of the adhesion is small and has no effect on the detection output.

(Example) Hereinafter, an example in which the present invention is embodied in a voltage sensor of a zero-phase voltage detection device will be described with reference to FIGS. 1 to 6.

60Hz or 501-1 z each phase distribution line L("
.

Since the voltage sensors Su, Sv, and Sw arranged between mt at substantially equal distances from the LV and LW have the same configuration, the voltage sensor Su will be explained. This voltage sensor 3u is composed of a detection section 7 and a signal processing circuit 8.

The case 1 has a channel-shaped cross section, and mounting pieces 2 are formed at both ends of the side walls facing each other and at both ends of the bottom wall, respectively, to be bent inward at right angles. Said case 1
An M3 formed in a reverse channel shape so as to cover both end openings and the upper part of the case 10 is tightened and fixed to the mounting piece 2 by screws 4 inserted through both end walls, and a rectangular shaped M3 is attached to the upper surface of the mounting piece 3. A window hole 5 is provided as a displacement current inflow portion. The case 1 and M3 are formed of a 1ffi aluminum body, and serve as a shield container for a detection electrode 10, which will be described later.

A flat detection electrode 10 is fixed to the upper surface of the central part of the case 1 with screws 11 via an insulating support member 6 formed from an insulating material such as synthetic resin into a thin round bar shape. It is preferable to make the surface area as small as possible, and in experiments, the short side dimension of the detection electrode is
The diameter of the insulating support member is 17'5. The detection electrode 10G is arranged parallel to the lid 3, and is arranged so as to close the window hole 5 from the inside with a gap between the case 1 and the lid 3. The detection electrode 10 is made of a conductive material such as metal, S-conductive resin, or conductive rubber, and stainless steel is used in this embodiment.

And the above case 1. Lid 3. A detection section 7 is configured by the detection electrode 10 and the like.

A single-core shielded electric wire 31 is inserted into the inside of the insulating support member 6 of the detection section 7, and the same single-core shielded electric wire 1! The core wire of the wire 31 is connected to the detection electrode 10, and the single-core shielded electrode 31 is led out from the case 1 and connected to the zero-phase voltage detection tube 20 described later.
A signal processing circuit 8 installed inside the case (not shown)
It is connected to the.

Further, the shield braided wire of the single-core shielded electric wire 31 is connected to the case 1. Since this signal processing circuit 8 has the same configuration as each voltage sensor 3u, 3v, 3w, the signal processing circuit 8 connected to the detection electrode 10 will be explained.

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

Is the amplifier circuit A displaced from the detection electrode 10? When a ti current is input, the displacement current is amplified and a waveform similar to the displacement current is output. Specifically, the configuration is as follows. That is, the input terminal P1 of the signal processing circuit 8 is connected to the ground line E1 via the resistor R1, and
A case 1 constituting a shielded container is connected to a ground line E1 via a terminal P2. Between both terminals of the resistor R1, a pair of diodes D1. A parallel circuit of D2 is connected, and serves as a protection circuit for preventing excessive input from the detection electrode 10.

The input terminal P1 is connected to the operational amplifier OP1 via a resistor R2.
is connected to the inverting input terminal of the operational amplifier O.
The non-inverting input terminal of P1 is connected to the ground line E1 via a 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 ○P1. J3 and capacitors C2 and C3 are for stabilizing the power supply of the operational amplifier OP1.

The resistors R1 to R4, the diode D1. An amplifier circuit A is constituted by D2, a capacitor C1, and an operational amplifier OP1.

When a signal proportional to the displacement current is applied from the amplifier circuit Δ, the bandpass filter B is set to selectively amplify the frequency 601'Z or 5011z based on the signal and not extract it. Specifically, it is structured as follows. That is, a series circuit of a capacitor C6 and a resistor R5 is connected between the output terminal of the operational amplifier oP1 and the inverting input terminal of the operational amplifier OP2.
Further, the non-inverting input terminal of the operational amplifier ○P2 is connected to the ground line E1 via a resistor R6. Masked tube amplifier ○
A capacitor C4 is connected between the inverting input terminal and the output terminal of P2.
A parallel circuit consisting of a series circuit of C5 and a series circuit of resistors R7 and R8 is connected. Moreover, the resistors R7 and R8
A capacitor C7 is connected between a point a in between and the ground line E1.

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 electrode 10. The signal processing circuit 8 constitutes a voltage sensor 3u. Note that the output terminals of the other voltage sensors Sv and Sw are pv instead of pu for convenience of explanation.
, pw.

The voltage sensors 3u, 3v, 3w arranged on the power distribution lines Lu, Lv, LW of each phase are connected to a zero-phase voltage detector 20, and a detection circuit 21 installed in the zero-phase voltage detector 20 is Adder circuit 22; Adder circuit 22. and a power supply circuit 23 for the voltage sensor.

The adding circuit 22 connects each voltage sensor Su, Sv.

The signals outputted from Sw and selected at a predetermined frequency are synthesized and a signal multiplied by the zero-phase voltage Vo is outputted to the output terminal P thereof. Specifically, the adder circuit 22 is configured as follows.

That is, the output terminals Pu, P of the voltage sensors Su, Sv, Sw are connected to the G point of the inverting input terminal of the operational amplifier OP3 via variable input resistors R11, R12 and R13, respectively.
v and Pw are connected, and the non-inverting input horn terminal is grounded via a resistor R14.

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

Further, the output terminal of the operational amplifier OP3 is connected to the operational amplifier O.
It is connected to the output terminal P via a voltage follower using P4 and a resistor R16. This voltage borrow increases the input impedance and lowers the output impedance, thereby performing impedance conversion.

The resistors R11 to R16 and the operational amplifier OP3°OR3
The adder circuit 22 is configured by:

To explain the power supply circuit 23, M applied 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.

The point d on the secondary side of the power transformer 24 is connected to the ground wire E2.
A smoothing capacitor C14 and a capacitor C15 are connected between the positive terminal of the full-wave rectifier 25 and the ground line E2.

Further, a three-terminal regulator 26 is connected between the positive terminal of the full-wave rectifier 25 and the ground wire E2, and the output terminal of the three-terminal regulator 26 is connected to the VCCE terminal, and the output terminal of the three-terminal regulator 26 is also connected to the VCCE terminal. and ground wire E2
A capacitor C8 and a capacitor C9 are connected between them.

Further, a smoothing capacitor C10 and a capacitor C11 are connected between the negative terminal of the full-wave rectifier 25 and the ground wire E2. Further, a three-terminal regulator 27 is connected between the negative terminal of the full-wave rectifier 25 and the ground wire 12,
The output terminal of the three-terminal regulator 27 is connected to the -Vcc terminal, and a capacitor C12 and a capacitor C13 are connected between the output terminal of the three-terminal regulator 27 and the ground line 12.

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

In FIG. 3, the power distribution line 1u of each phase serves as a charging section.

Corresponding to LV and 1w, the voltage sensors su, sv, and sW are approximately the same distance 11! They are spaced apart from each other. When a three-phase voltage according to normal phase rotation is applied to the distribution line, the capacitance ff1cu formed between the distribution lines Lu, LV, LW and the ground, which is the base Jv potential point, is
, cv, cw is collected by the detection electrode 10 through the window hole 5 of each voltage sensor Su, Sv, Sw, which serves as a displacement current inflow section.

Then, this displacement current is applied to each voltage sensor SU, Sv, 3w.
The displacement current is applied to the amplifier circuit A of the signal processing circuit 8, and the amplifier 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 Pi and P2 is considered to be a parallel value of the resistors R1 and R2. In typical operational amplifier applications, resistor R2 has a value on the order of Ω. The closed loop profit 10R4/R2 is taken to be around 1000 to obtain sufficient output. Furthermore, the resistance R1 is set to a value lower than the creepage leakage resistance of the insulating support member 6 that supports the detector wi10, and is used for stabilizing the input or finely adjusting the output, but its value is on the order of 10Ω or more. is the amount of Therefore, the input impedance mentioned above is effectively kept at a sufficiently low value by the resistor R2, yet a large signal 17 is provided at the output of the operational amplifier OP1 due to the high closed-loop gain. Furthermore, as is well known, the operational amplifier OP
The phase difference between the input and output of 1 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 an output proportional to the displacement current is obtained. In the opposite case, the phase difference is close to 90", and the output is an integral value of the displacement current, that is, a value proportional to the potential of the distribution line. In any case, this output has a waveform similar to the displacement current. It will be done.

Next, when a signal similar to the displacement current is applied to the bandpass filter B, based on the signal, it selectively amplifies and extracts a signal having a center frequency of 60H2 or 501-1z. Then, the adder circuit 22 of the zero-phase voltage detector 20 synthesizes the signals selected at a predetermined frequency output from each voltage sensor Su, SV, and 3w, and outputs a zero-phase voltage VO signal to its output terminal P. (See Figure 6). In FIG. 6, α, β, and γ are the waveforms of the voltages applied to the distribution lines of each phase.

In this way, in a normal case, the ground voltages of each phase are balanced, so the zero-phase voltage VO obtained by combining in the adding circuit 22 becomes O.

Next, if a ground fault occurs in the distribution line of one of the phases of LJ, Lv, and LW, the balance of the ground voltage of each phase will be 11, and each voltage sensor will be 1 Su.

Zero-phase voltage detector 20 via 3V, 3W signal processing circuit 8
When the signals outputted from the above are combined in the enhancement circuit 22, 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 case 1 and the lid 3 of the voltage sensors Su, Sv, and Sw serve as shield electrodes, and in order to effectively prevent the inflow of displacement current from sources other than the distribution line that is the object to be measured,
There is virtually no negative influence from other power distribution lines other than the power distribution line that is the object to be measured.

Furthermore, since the detection electrode 10 is supported by the case 1 by a thin round bar-shaped insulating support member 6, even if rainwater or dirt enters through the window hole 5, it will be located on the back side of the detection electrode 10, so it will not be insulated. Since it is difficult to adhere to the support member 6, and even if it does adhere, its surface area is small, sufficient creepage leakage resistance between the detection electrode 10 and the case 1 can be maintained. Therefore, this voltage sensor can perform accurate voltage detection even when wet with rain.

Moreover, each phase voltage sensor 311. Even if there is a slight difference in the effective gains of Sv and SW and a zero-phase output is generated at the output terminal P even if the ground voltages of each phase are balanced, resistors R11, R12, and R13 are Adjust each change so that the zero-phase output is as close to zero as possible.

(Second Embodiment) Next, the second embodiment will be described only with respect to the differences from the previous embodiment. In this embodiment, as shown in FIG.
has been established.

The detection electrode 10 is fixed to the insulating support member 6 at ports 1 to 33, and the core wire of a single-core shielded J electric wire 31 is connected thereto.

Therefore, rainwater, salt water, dust, etc. are difficult to adhere to the lower surface of the insulation folds 6a and the area between the insulation folds 6a, so that the insulation support member 6 has excellent stain resistance. Can cut off leakage current path. ,
Furthermore, since the insulation distance between the detection electrode 1o and the case 1 and lid 3 as shield electrodes is increased by the insulation folds 6a, sufficient creepage leakage resistance can be ensured through the surface of the insulation support member 6, and accurate Voltage detection can be performed. Other effects are the same as those of the first embodiment.

Effects of the Invention As detailed above, in the present invention, since the detection electrode is housed in the grounded case, it is possible to accurately measure the voltage of the target charged section without being influenced by other charged sections. or,
Since the detection electrode is supported by a rod-shaped support member made of an insulating material, a sufficient insulation state is ensured, and the support member does not affect the detection output. In other words, since a non-contact method can be adopted in which the charging part is placed at a distance, it is possible to provide an inexpensive and accurate voltage sensor with a simple configuration, making it an excellent invention for industrial use.

[Brief explanation 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 a voltage hinger, Fig. 3 is an overall view of a zero-phase voltage detection device, and Fig. 4 is a diagram of a voltage sensor. Electric circuit diagram, Figure 5 is an electric circuit diagram of the detection circuit of the zero-phase voltage detector, Figure 6 is the zero-phase voltage detected by this zero-phase voltage detection device and voltage oscilloscope of each phase distribution line, and Figure 7 is an electric circuit diagram of the detection circuit of the zero-phase voltage detector. The figure shows a second embodiment of the signal processing circuit, 10...detection electrode, 20...zero phase voltage detector, 21...detection circuit, A...amplification circuit, B...bandpass Filter, El, R2...Grounding wire, OP1-OP4...Operation amplifier, R1-R16.
・Resistance, C1~・C15...Capacitor, Pl...
・Input terminal, R2... terminal, pu, pv, pw...
Output terminal, Cu, cv. Cw...0 capacity ω, Lu+ LV, LW...distribution line. Patent applicant: Nippon Insulators Co., Ltd. Representative: Takamatsu Electric Works Co., Ltd. Patent attorney: On 1) Hironobu Figure 1

Claims (1)

[Claims] 1. A window hole is provided in the upper surface of an electrically grounded shield container made of a conductive material, and a thin rod-shaped support member made of an insulating material is provided inside the container. A supported plate-shaped detection electrode is arranged, and the window hole is arranged on the upper surface of the detection electrode so as to be closed with a gap between it and the inner surface of the container, and an amplifier circuit is connected to the detection electrode. A voltage sensor characterized in that a signal processing circuit consisting of a bandpass filter is connected. 2. The voltage sensor according to claim 1, wherein the support member has insulating folds on its surface.