JP3348522B2 - Insulation monitoring device for power equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for monitoring the insulation of power equipment such as a gas insulated switchgear.

[0002]

2. Description of the Related Art As an apparatus for monitoring the insulation state of power equipment such as a gas insulated switchgear, a gas insulated bus, and a transformer, means for detecting a partial discharge generated when an insulation abnormality occurs in the power equipment is provided. In this case, the presence or absence of the partial discharge is monitored to monitor the presence or absence of the insulation abnormality.

When a partial discharge occurs in a power device, a high-frequency potential oscillation occurs and an electromagnetic wave is generated. Therefore, an antenna for detecting the electromagnetic wave is often used as a means for detecting the partial discharge.

FIG. 4 shows a gas-insulated switchgear GIS as an example.
Antenna for detecting partial discharge in a metal container 1 containing components of the apparatus for detecting a partial discharge generated inside the antenna
1 shows an example of an insulation monitoring device into which is inserted. The container 1 includes a plurality of tubular containers 1A filled with SF ₆ gas,
The insulating spacer 2 is disposed between the flanges 1a and 1b of the adjacent containers 1A and 1B, and the main circuit conductor 4 is supported by the insulating spacer 2. In this example, a hole 5a is provided in a cover plate 5 that closes an opening of a container 1A accommodating a terminal portion of a main circuit conductor 4, and a partial discharge detection antenna 3 including a loop antenna is provided in the container 1A through the hole 5a. Has been inserted. A plate-shaped terminal block 6 is attached so as to close the hole 5a, and one end 3a and the other end 3b of the antenna 3 (feeding point) ) Is connected. One end of a coaxial cable 9 is connected to the other end of the coaxial conductor 7 via a connector 8, and the other end of the coaxial cable 9 is connected to an input terminal of a detection unit 10 installed at a location away from the gas insulated switchgear GIS. Have been. In many cases, an appropriate number of connectors 11 are present in the middle of the transmission path from the antenna 3 to the detection unit 10. FIG. 6 shows the electrical configuration of the insulation monitoring device shown in FIG.

[0005] When a partial discharge occurs in the gas insulated switchgear GIS shown in FIG. 4, an electromagnetic wave generated by the partial discharge is radiated from the conductor 4 and received by the antenna 3.
The signal received by the antenna 3 is transmitted to the detection unit 10 through the coaxial cable 9. The electromagnetic wave generated by the partial discharge has a pulse-like waveform and has a frequency component over a wide band. The detection unit 10 receives a signal transmitted through the coaxial cable 9 and determines the presence or absence of partial discharge. The detection unit includes, for example, a receiver that amplifies and detects a received signal, and a reception output of the receiver. And a signal processing device such as a computer for processing the data. The detection unit detects a level (frequency component) of a signal received at each measurement point, using a plurality of frequencies included in a frequency band with little noise such as broadcast radio waves as measurement points. The presence / absence of partial discharge is determined by comparing the average value of the signal levels detected respectively with the reference value.

If a partial discharge occurs in the power equipment, the frequency component of the signal received by the antenna 3 in a high frequency range increases. Therefore, a spectrum analyzer is provided in the detection unit 10 and a partial spectrum is obtained from the frequency spectrum obtained by the analyzer. The presence or absence of discharge may be determined.

In the example shown in FIG. 4, the antenna 3 for detecting partial discharge is arranged inside the power equipment, but the antenna may be arranged outside the power equipment. For example, in the case of a gas insulated switchgear, as shown in FIG.
The partial discharge detection antenna 3 may be attached to the outer periphery of the insulating spacer 2 that separates the gas between A and 1B. FIG.
Is a slot antenna having a structure in which a slot 3b is formed in a rectangular conductive plate 3a. The antenna 3 is disposed with the slot 3b facing the outer periphery of the insulating spacer 2, and the conductive plate 3a is 2 are fixed to the outer periphery of the flanges 1a and 1b on both sides.

[0008]

SUMMARY OF THE INVENTION In an insulation monitoring device in which the output of a partial discharge detection antenna attached to a power device is guided to a detection unit through a coaxial cable, a plurality of connectors are interposed between the antenna and the detection unit. Therefore, signal transmission may not be performed normally due to poor contact of the connector. Also, when performing any operation on the power equipment, an object may hit the coaxial cable laid from the antenna to the detection unit, and the coaxial cable may be disconnected.

As described above, if an abnormality has occurred in the transmission path from the antenna for detecting partial discharge to the detection section, even if partial discharge has occurred, it cannot be detected. No action can be taken and predictive maintenance of the equipment cannot be achieved.

An object of the present invention is to provide an insulation monitoring device for power equipment in which the state of a transmission path from an antenna for detecting partial discharge to a detection unit can be checked at any time to ensure reliability. Is to do.

[0011]

SUMMARY OF THE INVENTION The present invention provides an antenna provided to receive an electromagnetic wave generated by a partial discharge generated in a power device, and an antenna connected to the antenna via a cable to determine whether or not the partial discharge is present. The present invention relates to an insulation monitoring device for power equipment including a detection unit for detecting. In the present invention, a series branch connected in series to the antenna and a parallel branch connected in parallel to the antenna are provided between the feeding point of the antenna and the end of the cable on the antenna side. The test impedance is inserted. The series branch of the test impedance is configured to exhibit a sufficiently small impedance value at the frequency of the electromagnetic wave, but to exhibit a sufficiently large impedance value at a frequency (including direct current) lower than the frequency of the electromagnetic wave. The parallel branch of the test impedance is configured to exhibit a sufficiently large impedance value at the frequency of the electromagnetic wave.

The parallel branch of the test impedance shows a sufficiently large impedance value at the frequency of the electromagnetic wave, but at a frequency lower than the frequency of the electromagnetic wave, the impedance value is small enough to be measured from the detection unit side (the impedance value of the electromagnetic wave). It is preferable to have a configuration in which the impedance value is small enough to be distinguishable from the impedance value at the frequency.

[0013] The phrase "shows an impedance value small enough to be measurable from the detection unit side at a frequency lower than the frequency of the electromagnetic wave" means that the cable is normal from the detection unit side at a frequency lower than the frequency of the electromagnetic wave. The measured value when the impedance of the test impedance is measured through the sensor has a value small enough to be distinguishable from the measured value obtained when the impedance of the test impedance is measured through the cable in a disconnected state from the detection unit side. It is necessary.

[0014] The series branch of the test impedance can be constituted by a series capacitor provided so as to be interposed between one end of the antenna and one energizing path of the cable. And an inductive impedance connected in parallel to both ends of the antenna via a series capacitor with a resistor connected to the antenna and a high-frequency blocking coil.

In this case, the inductance of the high-frequency blocking coil should be sufficiently large so that its reactance can be considered to be almost infinite with respect to the frequency (several tens of MHz or more) of the electromagnetic wave generated by the partial discharge. Is preferred. Further, the capacitance of the series capacitor is set to be sufficiently large such that the reactance thereof can be regarded as substantially zero with respect to the frequency of the electromagnetic wave.

As the resistor, a temperature-sensitive resistor can be used if necessary.

The parallel branch of the test impedance includes a first diode and a first diode connected in series with each other.
A first inductive impedance having a resistor and a first high-frequency blocking coil, and a second inductive impedance connected in series with each other.
, A second resistor, and a second inductive impedance having a second high-frequency blocking coil. Also in this case, the series branch is constituted by a series capacitor provided so as to be interposed between one end of the antenna and one energizing path of the cable, and the first inductive impedance and the second inductive impedance are connected in series. Connect in parallel to both ends of the antenna via a capacitor.

In this case, the first diode and the second diode are provided in directions opposite to each other, and the first resistor is constituted by a resistor whose resistance value hardly changes depending on the ambient temperature. Further, the second resistor is constituted by a temperature-sensitive resistor.

[0019]

As described above, between the feeding point of the antenna and the end of the cable on the antenna side, a series branch exhibiting a sufficiently small impedance value at the frequency of the electromagnetic wave, and exhibiting a sufficiently large impedance value at the frequency of the electromagnetic wave. If a test impedance having a parallel branch is inserted, the impedance of the test impedance is measured through a coaxial cable from the detection unit at a frequency (including direct current) lower than the frequency of the electromagnetic wave, or When a voltage (including DC voltage) lower than the frequency of the electromagnetic wave is applied to the coaxial cable from the side, the current flowing through the test impedance is measured, and the measured value is confirmed. It is possible to confirm whether or not the transmission path of the incoming signal is normal.

Therefore, the insulation monitoring can be performed while checking the presence or absence of an abnormality in the connector of the transmission line, the disconnection of the coaxial cable, and the like as needed, thereby improving the reliability.

In the above insulation monitoring apparatus, when a DC current is passed from the detection section through a coaxial cable, the DC current flows through a resistor having a test impedance. Therefore, when a temperature-sensitive resistor is used as the resistor for the test impedance, the temperature near the antenna can be measured.

In this case, if the test impedance is arranged in the container of the power equipment, the temperature in the container can be measured.

When the power equipment is a gas-insulated equipment such as a gas-insulated switchgear, the gas density in the container is controlled by converting the gas pressure in the container into a pressure value at normal temperature in order to maintain the insulation performance. However, in this case, it is necessary to detect the temperature of the gas in the container in order to calculate the room temperature converted value of the gas pressure. In the present invention, when a resistor having a test impedance is disposed in a container and a temperature-sensitive resistor is used as the resistor, the temperature in the container can be detected. Can be done.

[0024]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 3 denotes an antenna for detecting partial discharge, and 9 denotes an antenna 3
Is a coaxial cable for transmitting the received signal, 10 is a detector for detecting the presence or absence of partial discharge from the signal transmitted through the coaxial cable 9, and 11 is a connector provided in the middle of the cable 9.

In the present invention, the feeding point 3 of the antenna 3
A test impedance Z is inserted between a, 3b and one end of the coaxial cable 9. This test impedance Z is connected in series with a series capacitor Cs provided so as to be interposed between one end of the antenna 3 and one end of a current path (center conductor in the illustrated example) of the cable 9. And an inductive impedance Zi connected in parallel to both ends of the antenna 3 via a series capacitor Cs having a resistor Rp and an inductance Lp. In this example, the series branch of the test impedance is formed by the series capacitor Cs, and the inductive impedance Z
i forms a parallel branch of the test impedance.

The antenna 3 for detecting partial discharge may be arranged in the container of the power equipment as shown in FIG. 4 or may be arranged outside the power equipment as shown in FIG. Antenna 3
When the test impedance Z is disposed in the container, the test impedance Z may be disposed in the container or may be disposed outside the container. For example, when the antenna 3 is provided as shown in FIG. 4, the impedance Z may be arranged at the connection between the feeding points 3a and 3b of the antenna 3 and the coaxial conductor 7 supporting the antenna.
The impedance Z may be arranged at the connection between the coaxial conductor 7 and the coaxial cable 9.

In this embodiment, the impedance Z and an equivalent circuit of the antenna 3 are as shown in FIG. 2A, and the impedance Za of the antenna 3 can be represented by a parallel circuit of a loss resistance Ra and a capacitance Ca. it can.

In the present invention, the capacitance of the series capacitor Cs is made sufficiently large so that the measurement frequency band (Equation 10) is obtained.
MHz or more), the reactance of the series capacitor Cs (the impedance value of the series branch of the test impedance) can be regarded as substantially zero. For example, if the capacitance of the series capacitor Cs is 2000 pF
Then the reactance becomes 0.6 Ω at 50 MHz,
It can be regarded as almost zero in the measurement frequency band. The inductance Lp of the parallel branch of the test impedance
Is sufficiently large so that its reactance can be considered to be substantially infinite in the measurement frequency band (so as to be sufficiently larger than the combined impedance of the series circuit of the series capacitor Cs and the impedance Za of the antenna). Keep it large.

Further, in order to enable detection of the temperature of the power equipment to be monitored, the resistor Rp is constituted by a temperature-sensitive resistor (side temperature resistor) whose resistance value changes in accordance with a change in ambient temperature. Can be.

As described above, when the power device to be monitored is a gas-insulated device such as a gas-insulated switchgear or a gas-insulated bus, the temperature of the gas is detected to control the gas density in the container. However, if the resistor Rp is composed of a temperature-sensitive resistor and the resistor is disposed in a container, the gas can be detected by detecting a change in the resistance value of the resistor. Temperature can be detected.

In this embodiment, assuming that a DC voltage is applied from the detection unit 10 side through the coaxial cable 9, the impedance when the test impedance Z and the antenna 3 are viewed from the coaxial cable 9 side is as shown in FIG. ) Can be represented substantially only by the resistor Rp. Therefore, when a constant DC voltage is applied to the coaxial cable 9 on the detection unit 10 side and a current flowing through the coaxial cable 9 and the test impedance Z is detected, the detected value of the current is determined by comparing the applied voltage with the coaxial cable 9 and the connector 11. And the resistance value of the resistance of the resistor Rp of the test impedance Z is reduced by the sum of the resistance of the impedance of the signal transmission path containing the signal and the current detection value is constant if the signal transmission path is normal. become. Also, the ratio of the applied voltage to the current (detection unit 1
The impedance when the antenna is viewed from the 0 side is constant. Therefore, a constant DC voltage is applied to the coaxial cable 9 from the detection unit 10 while the transmission path is confirmed to be normal, and the current flowing at that time is detected as a reference current value. By comparing the current flowing when the DC voltage is applied to the coaxial cable from the unit 10 with the reference current value, it can be determined whether the transmission line is normal.

That is, when a current equal to the reference current value flows when a DC voltage is applied to the coaxial cable 9 on the detection unit 10 side, it can be detected that the transmission line is normal. When a current flowing when a DC voltage is applied to the coaxial cable 9 on the detection unit 10 side is larger than the reference current, or when a DC current does not flow when the DC voltage is applied, the connector is connected to the connector in the middle of the transmission line. It is possible to detect that a contact failure has occurred or that a disconnection has occurred in the middle of the transfer path.

When the resistor Rp is formed of a temperature-sensitive resistor, the resistor Rp is arranged due to the magnitude of the current flowing when a DC voltage is applied to the test impedance from the detection unit 10 through the coaxial cable 9. It is possible to detect the temperature of the portion where the temperature is set.

Further, since the impedance of the antenna 3 in the measurement frequency band is sufficiently small and the reactance of the inductance Lp is sufficiently large, when the test impedance Z and the antenna 3 are viewed from the coaxial cable 9 side in the measurement frequency band. The equivalent circuit can be represented only by the series capacitor Cs as shown in FIG. Since the reactance of the series capacitor Cs in the measurement frequency band is sufficiently small, signal transmission from the antenna 3 to the detection unit 10 is performed without any trouble.

In the above description, whether the transmission line is normal or not is detected from the magnitude of the DC current flowing when a DC voltage is applied from the detection unit 10 to the test impedance Z through the coaxial cable 9. By applying a high-frequency signal of a predetermined frequency from the detection unit 10 through the coaxial cable 9 and measuring the impedance when the test impedance Z is viewed through the coaxial cable 9,
It is possible to detect whether or not the transmission path is normal.

FIG. 3 shows an equivalent circuit of another embodiment of the present invention. In this embodiment, a test impedance Z is shown.
Are connected between one end of the antenna 3 and one current path of the cable, a series capacitor Cs, a first diode D1, a first resistor Rp1 and a first resistor Rp1 connected in series with each other. , And a first inductive impedance Z connected in parallel to both ends of the antenna via a series capacitor Cs.
i1 and a second diode D2 connected in series with each other,
It comprises a second resistor Rp2 and a second high-frequency blocking inductance Lp2, and is composed of a second inductive impedance Zi2 connected in parallel to both ends of the antenna 3 via a series capacitor Cs. The first diode D1 and the second diode D2 are provided in directions opposite to each other. In this embodiment, the first resistor Rp1 is a reference resistor whose resistance hardly changes with temperature, and the second resistor Rp2 is a temperature-sensitive resistor.
If the power equipment to be monitored is gas-insulated equipment,
At least a second resistor Rp2 composed of a temperature-sensitive resistor
Is preferably located within the container of the device to detect the gas temperature of the device.

In the embodiment shown in FIG. 3, the series branch of the test impedance is formed by the series capacitor Cs, and the parallel branch of the test impedance is formed by the first inductive impedance Zi1 and the second inductive impedance Zi2. The road is configured.

When the test impedance is configured as shown in FIG. 3, one of the resistors Rp1 and Rp2 is selected by selecting the polarity of the DC voltage applied from the detection unit 10 through the coaxial cable 9. Only when a DC current is supplied, the state of the transmission path can be checked and the temperature of the power device can be detected.

That is, when a DC voltage having a polarity such that the anode side of the diode D1 becomes positive potential is applied to the coaxial cable 9 on the detection unit 10 side, a constant DC current flows through the resistor Rp1 having a constant resistance value. By checking the value, it is possible to detect whether the state of the transmission path is normal. When a DC voltage having a polarity at which the anode side of the diode D2 becomes positive potential is applied to the coaxial cable 9 on the detection unit 10 side, a DC current flows through a resistor Rp2 whose resistance value changes according to the ambient temperature. Since the magnitude of the current corresponds to the temperature at the place where the test impedance is arranged, the temperature at the place where the test impedance is arranged can be detected from the current value.

When the test impedance is configured as shown in FIG. 3, the test impedance shows a constant impedance value with respect to a specific frequency. The state of the transmission line can also be detected by applying a signal and measuring the impedance when the test impedance side is viewed from the detection unit.

While the preferred embodiments of the present invention have been described above, the main aspects of the present invention disclosed in this specification will be described below.

(1) An antenna provided to receive an electromagnetic wave generated by a partial discharge generated in a power device, and a detecting unit connected to the antenna via a cable to detect the presence or absence of the partial discharge. In the insulation monitoring device for power equipment, between the feeding point of the antenna and the end of the cable on the antenna side, a series branch connected in series to the antenna, and in parallel to the antenna A test impedance having a parallel branch connected thereto is inserted, and the series branch of the test impedance exhibits a sufficiently small impedance value at the frequency of the electromagnetic wave, but at a frequency lower than the frequency of the electromagnetic wave and at direct current. The test impedance parallel branch is configured to exhibit a sufficiently large impedance value. An insulation monitoring device for power equipment, which is configured to exhibit a large impedance value, but to exhibit an impedance value at a frequency lower than the frequency of the electromagnetic wave and a direct current sufficiently lower than the impedance value at the frequency of the electromagnetic wave. .

(2) The series branch of the test impedance is composed of a series capacitor provided between one end of the antenna and one of the current paths of the cable. The branch is composed of an inductive impedance having a resistor and a high-frequency blocking coil connected in series with each other and connected in parallel to both ends of the antenna via the series capacitor. An insulation monitoring device for power equipment according to the above (1).

(3) The insulation monitoring device for power equipment according to the above (2), wherein the resistor is a temperature-sensitive resistor.

(4) The series branch of the test impedance comprises a series capacitor provided between one end of the antenna and one of the current paths of the cable, and the parallel branch of the test impedance is provided. The road is
A first diode having a first diode, a first resistor, and a first high-frequency blocking coil connected in series with each other and connected in parallel to both ends of the antenna via the series capacitor.
And a second diode, a second resistor, and a second high-frequency blocking coil connected in series to each other, and connected in parallel to both ends of the antenna via the series capacitor. A second inductive impedance, the first diode and the second diode are provided in directions opposite to each other, and the first resistor is formed of a resistor whose resistance value hardly changes due to ambient temperature. 2. The insulation monitoring device for a power device according to the above item (1), wherein the resistor 2 is formed of a temperature-sensitive resistor.

[0046]

As described above, according to the present invention, since the test impedance is inserted between the antenna and the coaxial cable, the impedance of the test impedance is measured through the coaxial cable from the detection unit side. Or, by measuring the current flowing through the test impedance when a voltage is applied to the coaxial cable from the detection unit side and confirming the measured value, whether the transmission path of the signal from the antenna to the detection unit is normal Can be confirmed. Therefore, the insulation monitoring can be performed while checking the presence or absence of an abnormality in the connector of the transmission line, the disconnection of the coaxial cable, and the like at any time, and there is an advantage that the reliability can be improved.

The test impedance is configured such that the series branch shows a sufficiently small impedance value and the parallel branch shows a sufficiently large impedance value at the frequency of the electromagnetic wave. It is possible to confirm the presence or absence of an abnormality in the transmission path without affecting transmission of the signal to the transmission path.

According to the first or second aspect of the present invention, by passing a current through the temperature-sensitive resistor, the temperature near the temperature-sensitive resistor can be detected.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an electrical configuration of an embodiment of the present invention.

FIG. 2A is a circuit diagram showing an equivalent circuit of a test impedance and an antenna of the embodiment of FIG. 1;
(B) and (C) are circuit diagrams showing an equivalent circuit for direct current and an equivalent circuit for high frequency of the test impedance, respectively.

FIG. 3 is a circuit diagram showing an equivalent circuit of a main part of another embodiment of the present invention.

FIG. 4 is a configuration diagram showing a configuration example of an insulation monitoring device to which the present invention is applied.

FIG. 5 is a configuration diagram showing a main part of another configuration example of the insulation monitoring device to which the present invention is applied.

FIG. 6 is a circuit diagram showing an electrical configuration of a conventional insulation monitoring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gas-insulated switchgear container 2 Insulating spacer 3 Partial discharge detection antenna 3a, 3b Feed point 9 Coaxial cable 10 Detector 11 Connector GIS Gas-insulated switchgear Z Testing impedance Cs Series capacitor Lp High frequency blocking coil Rp Resistor Lp1 First high frequency blocking coil Lp2 Second high frequency blocking coil Rp1 First resistor Rp2 Second resistor D1 First diode D2 Second diode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01R 31/02 G08C 25/00 H02H 5/00

Claims (2)

(57) [Claims] 1. An electric power device which is generated by a partial discharge generated in a power device.
An antenna provided to receive the electromagnetic waves,
Presence or absence of partial discharge when connected to antenna via cable
And an insulation monitoring device for power equipment,
Oite antenna end of the feeding point and the cable of the antenna
Between the antenna and the
A row branch and a parallel connected in parallel to the antenna
A test impedance having a branch is inserted, and the series branch of the test impedance is connected to the antenna.
Between one end of the cable and one current path of the cable.
It is made up of a series capacitor
It shows a sufficiently small impedance value at the electromagnetic wave frequency.
However, it is sufficiently large at frequencies lower than the frequency of electromagnetic waves.
And the parallel branches of the test impedance are connected in series with each other.
Temperature-sensitive resistor and high-frequency blocking coil connected to
Parallel to both ends of the antenna via the series capacitor
Being connected to an inductive impedance,
Shows a sufficiently large impedance value at the frequency of electromagnetic waves
For power equipment characterized by being configured as follows
Monitoring device. 2. The electric power equipment is caused by partial discharge.
An antenna provided to receive the electromagnetic waves,
Presence or absence of partial discharge when connected to antenna via cable
And an insulation monitoring device for power equipment,
Oite antenna end of the feeding point and the cable of the antenna
Between the antenna and the
A row branch and a parallel connected in parallel to the antenna
A test impedance having a branch is inserted, and the series branch of the test impedance is connected to the antenna.
Between one end of the cable and one current path of the cable.
It is made up of a series capacitor
It shows a sufficiently small impedance value at the electromagnetic wave frequency.
However, it is sufficiently large at frequencies lower than the frequency of electromagnetic waves.
Configured to indicate have impedance values, the parallel branch of the test impedance is in series with one another
A first diode, a first resistor, and a first
A high-frequency blocking coil, and
And a first inductive inductor connected in parallel to both ends of the antenna.
Impedance and a second diode connected in series with each other.
A second resistor, a second resistor and a second high-frequency blocking coil.
Parallel to both ends of the antenna via the series capacitor
And a second inductive impedance connected to
And a sufficiently large impedance at the frequency of the electromagnetic wave
And the first diode and the second diode are opposite to each other.
And the resistance of the first resistor changes substantially with the ambient temperature.
It consists not of resistor, a second resistor and characterized in that it consists temperature sensitive resistor
Monitoring equipment for power equipment.