JP2001183403A - Insulation resistance monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation resistance monitoring system, realizing reduction in size and cost reduction by reducing signal interference among the measurement signal, modulation signal, and alarm signal. SOLUTION: A grounding conductor 2 for one-point grounding the ground phase of a transformer 1 is grounded to the ground 3, while the transformer 1 is connected to cable ways 4, 5. The cable ways 4, 5 are connected on their extensions to first branch cable ways 7, 8 connected with a first load apparatus 6, and the cable way has a first insulating resistance 9 and a first capacitance 10. Meanwhile, the cable ways 4, 5 are connected to second branch cable ways 12, 13 connected with a second load apparatus 11, and the cable way has a second insulating resistance 14 and a second capacitance 15. This insulation resistance monitoring system is constituted by arranging an insulation resistance monitoring device 33, a branch cable way insulation resistance measuring device 34, and an alarm signal receiver 35, to above cable ways.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation resistance monitoring system, and more particularly, to an insulation monitoring device which is installed on a low-voltage path and collectively monitors the insulation resistance of a plurality of electric circuits connected to a transformer. The present invention relates to an insulation resistance monitoring system configured by a measuring instrument installed in an electric circuit for enabling insulation resistance to be measured in a live state, and an alarm signal receiver for receiving monitoring information.

[0002]

2. Description of the Related Art Conventionally, a measurement signal composed of a low-frequency component is applied to an electric circuit via a ground line provided on a low voltage side of a transformer, and a leakage current flowing back to the ground line is detected by a zero-phase current transformer. An insulation monitoring device that measures all insulation resistance when looking at the load equipment side from the transformer by calculating the effective component from the measurement signal in the leakage current, and further measures the insulation resistance individually in the branch circuit A branch line insulation resistance measuring instrument capable of performing such operations is used. On the other hand, as a means for transmitting an alarm signal from the insulation monitoring device or the like installed in the power receiving room to an office where a person is resident or a control station, etc., an alarm signal receiver using a ground return method has been put into practical use, and together with the monitoring device. Used. As a specific method of the above, there is disclosed a method of measuring the insulation resistance of a branch circuit by Japanese Patent Application Laid-Open No. 2-353 by the same applicant.
No. 73, and a method of transmitting an alarm signal is disclosed in JP-A-61-112538, respectively.

FIG. 2 shows a configuration example of a conventional insulation resistance monitoring system. The first branch circuits 6, 7 and the second load apparatus 1 are connected to the transformer 1 by connecting the ground wire 2 and the electric circuits 4, 5 connected to the ground 3 and extending the first load apparatus 8 to the first load apparatus 8.
3 are connected to the second branch electric paths 11 and 12. The first branch circuits 6 and 7 include a first insulation resistance (including load equipment) 9 and a first capacitance (including load equipment) 10. Similarly, the second electric lines 11 and 12
Includes a second insulation resistance (including load equipment) 14 and a second capacitance (including load equipment) 15. FIG. 2 is a diagram in which an insulation monitoring device 16, a branch circuit insulation resistance measuring instrument 17 and a monitoring signal receiver 18 are installed on the electric circuit configured as described above to form a system.

The insulation monitor 16 includes a first oscillator 19 for outputting a measurement signal, a second oscillator 20 for outputting a carrier signal modulated by the measurement signal, a modulator 21, and a third oscillator for outputting an alarm signal. Oscillator 22, an adder 23 that adds the measurement signal, the modulation signal, and the alarm signal, an injection transformer 24 that applies the addition signal to a ground line, and a zero-phase current transformer that extracts a leakage current from the ground line. And a detector 26 for calculating an effective component from the extracted leakage current and detecting the insulation resistance. On the other hand, the branch circuit insulation resistance measuring instrument 1
7 is a zero-phase current transformer 27 for extracting the leakage current of the branch circuit.
And a detection unit 28 that calculates an effective component from the extracted leakage current and detects an insulation resistance, and a filter 29 that filters a modulation signal.
And a demodulator 30 for demodulating the modulated signal. The alarm signal receiver 18 includes a DC blocking capacitor 31 and a frequency variable filter 32.

[0005] The operation of FIG.
Reference numeral 6 denotes a measurement signal for measuring the insulation resistance of the electric circuit, a modulation signal used as a reference phase of the measurement signal in the branch electric circuit insulation resistance measuring device 17, and an alarm signal (monitoring signal) for determining a frequency based on the insulation resistance value. Is applied to the ground line via the injection transformer 24, the leakage current flowing back to the ground line is extracted by the zero-phase current transformer 25, and the effective component is calculated by performing synchronous detection of the measurement signal included in the leakage current. I do.
Therefore, all the insulation resistances including the branch circuit when the load device is viewed from the transformer are detected, the alarm type is determined based on the magnitude of the detected value, and the output signal frequency of the third oscillator 22 is controlled. Outputs an alarm signal.

Next, a branch circuit insulation resistance measuring device 17 extracts a leakage current flowing through the branch circuit by the zero-phase current transformer 27, obtains a measurement signal and a modulation signal included in the leakage current, and demodulates the modulation signal. Then, the effective phase is calculated by synchronously detecting the measurement signal, and the insulation resistance of the branch circuit is measured. The alarm signal receiver 18 extracts an alarm signal applied to the ground wire by the insulation monitoring device 16 between the ground phase of the electric circuit and the ground wire of the third type construction in an office or the like, and assigns a frequency to each alarm type. The detected alarm signal is detected by the frequency variable filter 32, and the frequency value of the alarm signal is specified to obtain monitoring information.

[0007]

However, in the conventional insulation resistance monitoring system as described above, three sets of oscillators included in the insulation monitoring device are provided for the measurement signal, the modulation for generating the carrier, and the monitoring signal. Is required, but 3
When a set of frequencies is applied to the ground circuit by an injection transformer, distortion occurs in the signal due to the distortion characteristics of the injection transformer and the like, and interference occurs between the signals due to the generated harmonic components, etc., and the insulation monitoring device and other loads It may adversely affect the equipment, and it is desirable to minimize the signal applied to the electric circuit in order to avoid the influence on the load equipment. The alarm signal oscillator associates each monitoring information with an individual frequency, f ₁ , f ₂ ,
f ₃ ,... f _n are output, but it is necessary to select an optimal value when determining each frequency value in order to minimize interference between signals. However, when there is a large amount of monitoring information, that is, when the number of signals used as the alarm signal is large, it is difficult to make a selection, and it has been an obstacle in reducing the size and cost of the device. The present invention has been made to solve the problems of the conventional insulation resistance monitoring system as described above, and provides an insulation resistance monitoring system that reduces interference between signals and realizes downsizing and cost reduction. The purpose is to do.

[0008]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The insulation resistance monitoring system according to the present invention has the following configuration.
Take. In the electric circuit, the frequency f, which is the measurement signal of the insulation resistance,₀of
Determined by low frequency signal and separately detected insulation resistance
Carrier signal f corresponding to alarm signal₁Or f_TwoOr f _n
When a modulation signal modulated with a measurement signal is applied,
The leakage current flowing back to the ground wire
Detects the effective insulation resistance value from the signal and issues an alarm signal.
Insulation monitoring device with means for applying
Extract the leakage current flowing to the ground in the provided branch circuit
And the carrier frequency f output by the insulation monitoring device.₁Some
Is f_TwoOr f_nDemodulates the modulated signal of
Synchronous detection of the measurement signal included in the leakage current as the reference phase
By doing so, the insulation resistance which is the effective component of the measurement signal
A branch circuit insulation resistance measuring device having means for calculating a value,
On the extension of the electric circuit, the insulation monitoring device outputs
Carrier frequency f corresponding to alarm signal type₁Or f_TwoSome
Is f_nOf the modulation signal, and the level fluctuation of the modulation signal
After correcting the
Detects the frequency of the signal to identify the type of alarm signal and displays the alarm.
And an alarm signal receiver provided with a means.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 shows an embodiment of an insulation resistance monitoring system according to the present invention. Among the low voltage side electric circuits 4 and 5 of the transformer 1, the electric circuit 5, which is a ground phase, is grounded at one point to the ground 3 by the ground line 2. On the extension of the electric circuits 4 and 5, first branch electric circuits 6 and 7 connecting a first load device 8 and second branch electric circuits 11 and 1 connecting a second load device 13 are provided.
2 is connected. The first branch circuit includes a first insulation resistance 9 and a first capacitance 10, and the second branch circuit includes a second insulation resistance 14 and a second capacitance 15. And FIG. 1 is a diagram in which an insulation monitoring device 33, a branch electric circuit insulation resistance measuring instrument 34, and an alarm signal receiver 35 are installed on the electric circuit configured as described above to form a system.

The insulation monitoring device 33 includes a first oscillator 19 that outputs a measurement signal, a second oscillator 36 that outputs a carrier signal that is modulated by the measurement signal and that varies according to the type of alarm signal, A modulator 21 for amplitude-modulating the carrier signal output from the two oscillators 36, an adder 37 for adding the measurement signal and the modulation signal, and an injection transformer 24 for applying the measurement signal and the modulation signal to a ground line.
And a ground line 2 from the electric circuit via insulation resistance and capacitance.
A zero-phase current transformer 25 for extracting a leakage current flowing back to the amplifier, an amplifier 38 for converting the extracted leakage current into a voltage and amplifying it to a desired level, and a filter 39 for filtering a low-frequency measurement signal output from the amplifier 38. A phase detector 40 that outputs a reference phase signal, and a synchronous detector 41 that synchronously detects the measurement signal based on the reference phase signal in order to calculate an effective component due to insulation resistance from the filtered measurement signal. An alarm determiner 42 that outputs a predetermined alarm signal according to the magnitude of the insulation resistance value.

On the other hand, the branch circuit insulation resistance measuring device 34 is a zero-phase current transformer 27 for extracting a leakage current flowing back to the ground via the insulation resistance and the capacitance from the circuit in the branch circuit.
An amplifier 43 for converting the extracted leakage current into a voltage and amplifying it to a desired level, a first filter 44 for filtering a low-frequency measurement signal output from the amplifier 43, and a filter for a modulated signal output from the amplifier 43. A second filter 45, a demodulator 30 for demodulating the modulated signal, a phase adjuster 46 for adjusting a phase of a measurement signal obtained from the demodulator 30 for use in calculating an effective component due to insulation resistance, and a phase shifter 46. Limiter 47 for limiting the reference phase signal output by the device to a signal of constant amplitude
And a synchronous detector 48 for synchronously detecting the measurement signal by the reference phase signal. The alarm signal receiver 35 includes a DC blocking capacitor 31, an automatic gain adjuster 49 for adjusting the amplitude-modulated alarm signal to a constant level, and a frequency variable filter 32 for detecting a frequency value of the alarm signal.

Each device configured as described above operates as follows. In the insulation monitoring device 33, the first insulation resistance 9 and the first capacitance 10 from the first branch circuits 6 and 7 connected to the transformer 1 and the second insulation circuit 9 from the second branch circuits 11 and 12 are connected. The zero-phase current transformer 25 extracts the leakage current flowing back to the ground via the insulation resistor 14 and the second capacitance, respectively, converts the leakage current into a voltage, amplifies it to a desired level, and then passes through the filter 39. Obtain a low frequency measurement signal. The low-frequency measurement signal is subjected to synchronous detection using a measurement signal having a reference phase obtained by adjusting the phase of the output of the first oscillator 19 by the phase shifter 40, and the effective component of the measurement signal is calculated to obtain the insulation resistance. , And outputs a predetermined alarm signal according to the magnitude of the value. The alarm signal is output from the insulation monitoring device 3 installed in the power receiving room.
As means for transmitting the alarm signal to the alarm signal receiver 35 installed in the office or the control office where the person resides from 3 and transmitting the alarm signal, the ground return method is used.

Therefore, hereinafter, as a type of alarm, a normal signal is output when the insulation resistance value is large and the circuit is healthy, and when the insulation resistance value falls below a predetermined value due to a precursory phenomenon of insulation deterioration. The warning alarm will be described with an example in which a warning alarm is set when the insulation resistance value further falls below a predetermined value in a dangerous state. The predetermined alarm signal is output from the alarm determination unit 42.
, And outputs respective warning signals of “normal”, “caution”, and “warning”. Next, the second oscillator 36 receives the three types of alarm signals from the alarm determination unit 42 and outputs signals of frequencies f ₁ , f ₂ , and f ₃ determined corresponding to the respective alarm signals. Oscillator for outputting such a plurality of frequency signals, obtained by varying correspondingly the dividing ratio in the frequency f _1, f ₂ and f ₃ in obtaining frequency signal by dividing the output of the original oscillator Can be The output of the second oscillator 36 is also used in the branch circuit insulation resistance measuring device 34 to calculate the effective component of the measurement signal obtained from the leakage current, and is used to transmit a measurement signal serving as a reference phase at the time of calculation. And a carrier signal constituting the amplitude modulation signal. Note that the carrier signal has a relationship of carrier signal≫measurement signal. When outputting the "normal" as an alarm signal, the output frequency is the frequency f ₁ next to the second oscillator 36, the carrier frequency f ₁ by the measurement signal first oscillator output amplitude modulated, not amplitude-modulated The signal is applied to the ground line 2 via the injection transformer 24 together with the measurement signal for measuring the insulation resistance. Hereinafter, similarly, when outputting the "note" as an alarm signal, the output frequency of the second oscillator 36 is a carrier frequency f ₂ is amplitude-modulated by a measurement signal whose frequency f ₂ becomes and the first oscillator output, and when outputting the "warning" as an alarm signal, the output frequency of the second oscillator 36 becomes a frequency f _3, has a carrier frequency f ₃ is an amplitude modulated respectively amplitude-modulated by the measuring signal first oscillator output Is applied to the ground line 2 via the injection transformer 24 together with a measurement signal for measuring insulation resistance.

The branch circuit insulation resistance measuring device 34 is used for the purpose of searching for an insulation fault of the circuit when an alarm is issued by the insulation monitoring device 33, and can measure the insulation resistance of each branch circuit. And First branch circuit 6,
After extracting the leakage current flowing from 7 through the first insulation resistor 9 and the first capacitance 10 to the ground by the zero-phase current transformer 27, converting the leakage current into a voltage and amplifying it to a desired level, A low-frequency measurement signal is obtained via the first filter 44. On the other hand, the amplified voltage is input to the second filter 45, to obtain an amplitude-modulated signal obtained by amplitude-modulating a carrier frequency f ₁ or f ₂ or f ₃ by the measurement signal. Therefore, the band of the second filter 45 is determined by the carrier frequencies f ₁ , f ₂ and f ₃
Are all passbands. Next, the amplitude modulation signal is input to the demodulator 30 and demodulated into the original measurement signal. The demodulated measurement signal is adjusted in phase by a phase shifter 46 to be used as a measurement signal serving as a reference phase when performing an operation for obtaining insulation resistance.
, The reference phase measurement signal is set to a constant level and input to the synchronous detection circuit 48. The synchronous detection circuit 48 performs synchronous detection of the measurement signal obtained through the first filter 44 using the reference phase measurement signal, and measures an insulation resistance that is an effective component of the measurement signal. The measured insulation resistance value is displayed on a digital display or the like, and the insulation failure portion of the electric circuit is detected.

The warning signal receiver 35 is installed in an office or a control center where a person is resident, and receives a warning signal by the ground return transmission method. The alarm signal is obtained by amplitude-modulating the carrier frequencies f ₁ , f ₂ and f ₃ by the measurement signal as described above. The frequency f ₁ is a “normal” signal, the frequency f ₂ is a “caution” signal, and the frequency f ₃ is assigned to the "Alert" signal. Therefore, the alarm signal receiver 35 is connected to the grounding phase side of the electric circuit and the grounding wire of the third type construction (may be a general ground).
Is input via a capacitor 31. This input circuit has a high input impedance and avoids adverse effects on the circuit connecting it. The capacitor 31 is a DC blocking capacitor in consideration of convenience when inspecting the electric circuit using a megger or the like. Next, in the automatic gain adjuster 49, in order to detect a carrier signal from the amplitude modulation signal, a level change due to amplitude modulation is guaranteed and input to the frequency variable filter 32. Variable frequency filter 32, an alarm signal inputted, sequentially scanned extracted with three frequency values of the frequency f _1, f ₂ and f _3, receives the alarm signal by identifying the receive frequency. As a known example of the frequency variable filter 32, there is a method of varying a clock signal in a switched capacitor type digital filter. Therefore, the extracted alarm signal is used to monitor the insulation resistance of the electric circuit by displaying it on a display panel or the like. In the description of the embodiment of the present invention, the case of a single-phase two-wire circuit is used. However, the present invention is not limited to this, and a single-phase three-wire circuit or a three-phase three-wire circuit having a ground circuit at one end is used. There may be.

[0016]

As described above, according to the present invention, the measurement signal, the amplitude modulation signal, and the alarm signal output by the insulation monitoring device are obtained by the two oscillators. Since it can be reduced and the performance is improved, and the cost and size of the device can be reduced, it is possible to exert a great effect in the operation of the insulation resistance monitoring system.

[Brief description of the drawings]

FIG. 1 shows an embodiment of an insulation resistance monitoring system according to the present invention.

FIG. 2 shows a configuration example of a conventional insulation resistance monitoring system.

[Explanation of symbols]

1, transformer 2, ground line 3, ground 4, 5, electric circuit 6, first load equipment 7, 8, first branch electric circuit 9, first insulation resistance 10, etc. One capacitance 11 Second load device 12, 13 Second branch circuit 14 Second insulation resistance 15 Second capacitance 16 Insulation monitoring device 17 Branch Circuit insulation resistance measuring device 18 Alarm signal receiver 19 First oscillator 20 Second oscillator 21 Modulator 22 Third oscillator 23 Adder 24 Injection transformer 25 Zero-phase current transformer 26 Detection unit 27 Zero-phase current transformer 28 Detection unit 29 Filter 30 Demodulator 31 Capacitor 32 Frequency variable filter 33 Insulation monitoring device 34 ..Branch circuit insulation resistance measuring instrument 35.Alarm signal receiver 36.Second oscillator 37. Adder 38 Amplifier 39 Filter 40 Phase detector 41 Synchronous detector 42 Alarm determiner 43 Amplifier 44 First filter 45 Second filter 46 Phaser 47 Limiter 48 Synchronous detector 49 Automatic gain adjuster

Claims (1)

[Claims] To 1. A path, a low-frequency signal of frequency f ₀ is the insulation resistance measurement signal, the detected carrier signal f ₁ or f ₂ or f corresponding to an alarm signal for determining the insulation resistance value
_{A means} for applying a modulation signal obtained by modulating _n with the measurement signal, extracting a leakage current flowing back to the ground line, detecting an insulation resistance value that is an effective component from the obtained measurement signal, and outputting a warning signal. and insulation monitoring device including, extracted leakage current flowing to earth at the branching path which is provided on the extension of paths, the insulation monitoring apparatus demodulates the modulated signal of the carrier frequency f ₁ or f _2, or f _n outputs ,
By performing synchronous detection of the measurement signal contained in the leakage current with the obtained signal as the reference phase, a branch circuit insulation resistance measuring device including means for calculating an insulation resistance value that is an effective component of the measurement signal, in an extension of path, after the insulation monitoring device receives the modulation signal of carrier frequency f ₁ or f _2, or f _n corresponding to the alarm signal type to be output, and corrects the level fluctuation of the modulated signal, a variable frequency An insulation resistance monitoring system, comprising: an alarm signal receiver having means for detecting any carrier frequency by a filter to specify an alarm signal type and displaying an alarm.