JPH10319077A - Insulation monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with a current transformer for detecting an earthing conductor current and miniaturize a current injection transformer by providing an injection current detecting part for measuring an injection current on the injection side of the current injection transformer. SOLUTION: This device comprises a current injection power source 3-1A for injecting a test current to a current injection transformer 4A, an injection current detecting part 3-2 for detecting the injection current on the injection side through a sensor 3-5, a current injection power source voltage detecting part 3-3 for measuring the current injection level of the power source 3-1A, and an insulation resistance current arithmetic part for inputting the injection voltage and current to determine the insulation resistance current. Since the current detecting part 3-2 measures the testing injection current of the current injection transformer 4A on the injection side of the transformer 4A according to this structure, a current transformer for detecting an earthing conductor current is unncessary, the separation from the earthing conductor current by commercial frequency voltage is also unnecessary, the measurement precision for measurement of a single waveform is improved, and the device can be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation monitoring device for monitoring a current corresponding to an insulation resistance of a low-voltage side electric circuit of a single-wire grounding system in a live state.

[0002]

2. Description of the Related Art The configuration and grounding example of a conventional insulation monitoring device will be described with reference to FIG. In FIG. 6, reference numeral 1 denotes a power receiving transformer. The high voltage side is connected to the high voltage side electric circuit L1, the low voltage side is connected to the low voltage side electric circuit L2, and one line of the low voltage side is grounded by the ground line 2. 3 is an insulation monitoring device, and a current injection transformer 4
A current injection power source 3A for injecting a low-frequency current for testing into a power supply, a current detection unit 3B for measuring the injection current via a current transformer 5 provided on the ground line 2, an injection voltage detection unit 3C,
B and 3C, and an insulation resistance component current calculation unit 3D for obtaining the insulation resistance component current.
The insulation monitoring device 3 having the above configuration is divided into a harmonic current and a commercial frequency current, that is, an insulation resistance component current flowing between the low-voltage side electric circuit L2 and the ground and a current due to the stray capacitance between the grounds. A current, for example, a test current of about 10 Hz is injected, and a current corresponding to the insulation resistance is calculated and specified from the level of the injected current and the phase of the injected current corresponding to the injected voltage. The level of the injection current is, of course, almost proportional to the insulation resistance, and the current detection unit 3B is provided with a filter (not shown) for separating low-frequency current.

[0003]

However, in the configuration of the conventional insulation monitoring apparatus described above, two current injection transformers 4 and current transformers 5 for detecting the ground line current must be provided on the ground line 2. However, there is a problem that a large installation space is required and the current injection transformer 4 becomes very large due to the low frequency current. An object of the present invention is to provide an insulation monitoring device that can eliminate the current transformer 5 for detecting the ground line current and can downsize the current injection transformer 4.

[0004]

In order to achieve the above-mentioned object, a first means of the insulation monitoring apparatus according to the present invention comprises an injection current measuring an injection level of an injected low-frequency current at an injection side of a current injection transformer. A detection unit is provided, and an insulation resistance component current calculation unit for calculating an insulation resistance component current from the injection current and the injection voltage by calculation is provided.

A second means of the insulation monitoring apparatus according to the present invention is such that, in addition to the first means, a test current is always injected by the current injection transformer 4, and when the injected current exceeds a specific value. A switch for switching the current injection transformer from the current injection power supply to a ground line current detection unit is provided, and a ground line current detection unit that detects a ground line current through the current injection transformer.
An insulation resistance component current specifying unit for specifying the insulation resistance component current based on the ground line current is provided.

Further, a third aspect of the insulation resistance monitoring apparatus according to the present invention
The means includes a low-frequency / high-frequency combined power supply in which a high-frequency current is superimposed on a low-frequency test current and the test current is injected from a transformer for injection into a ground line. .

Further, the fourth means of the insulation resistance monitoring apparatus of the present invention comprises the step of, prior to superimposing the low frequency test current on the high frequency current, of the current injected into the ground line by the third means. It is provided with an insulation resistance component current calculation unit for detecting and obtaining an insulation resistance component current from the test injection current and the injection voltage.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first means of the present invention comprises a current injection power supply, a current injection power supply voltage detection section, and a current injection power supply for injecting a test current for detecting an insulation resistance component current into a current injection transformer. And an insulation resistance component current calculation unit for calculating an insulation resistance component current by calculating from the detected current and the current injection power supply voltage, and detecting a ground line current. This eliminates the need for a current transformer for detection and does not measure the injected current via the ground line, so that when measured on the ground line side, there is no need to separate the injected current from the current originally flowing in the ground line. Have.

The second means of the present invention comprises a current injection power supply for injecting a test current into a current injection transformer installed on a ground line, a current injection power supply voltage detector, an injection current detector, A line current detection unit, and an insulation resistance component current calculation unit that receives a detection voltage of the current injection power supply voltage detection unit and a detection current from the injection current detection unit and calculates an insulation resistance component current by calculation, and A switch is provided for switching the current injection transformer from the current injection power supply to the ground line current detection section when the current obtained by the resistance component current calculation section exceeds a specific value,
A ground line current detection unit that detects a ground line current via the current injection transformer, and an insulation resistance component current specification unit that specifies the insulation resistance component current based on the calculated insulation resistance component current and the ground current. With the configuration, the capacity of the current injection power supply and the capacity of the current injection current transformer do not need to be increased unnecessarily, and the current transformer for the current measurement is unnecessary even though the ground line current is measured. Has the effect of

Further, the third means of the present invention is that the current injection power supply includes a low frequency current and a high frequency power supply for testing, and a low frequency / high frequency combined power supply obtained by combining the two power supplies. This is to inject the test current into the current injection transformer installed on the grounding wire, which means that it was injected as a high-frequency current when viewed from the current injection transformer,
This has the effect that the core cross-sectional area can be made much smaller than that of the low frequency current injection transformer because the magnetic flux density of the current transformer is inversely proportional to the frequency.

Further, the fourth means of the present invention, in addition to the third means, comprises an injection circuit for detecting a low-frequency test current before superimposing the low-frequency test current on the high-frequency current among the currents injected into the ground line. A current detection unit is provided to obtain an insulation resistance component current from the test injection current and the injection voltage, whereby only the test low frequency current is filtered from the current injected into the current injection transformer of the third means. This has the effect that separate measurement is not required.

Embodiments 1 to 4 of the present invention will be described below with reference to FIGS. 1 to 5.

(Embodiment 1) In Embodiment 1, one line of a low-voltage side electric circuit (not shown) of a power receiving transformer is grounded by a ground line 2, and a current injection transformer 4 provided on the ground line 2 is provided.
FIG. 1 shows an insulation monitoring device 3 for calculating an insulation resistance component current from an injection current / voltage to A by calculation. FIG.
In the above, the current detecting unit 3-2 measures the test injection current of the current injection transformer 4 on the injection side of the current injection transformer 4A, thereby eliminating the conventionally required current transformer for ground line current detection (FIG. 6). This has the effect of making it unnecessary and not necessary to separate it from the ground line current by the commercial frequency voltage. Then, the configuration is such that a current injection power supply 3-1A for injecting a test current into the current injection transformer 4A, and an injection current detection unit 3-3 for detecting an injection current from the power supply on the injection side via a sensor 3-5. 2 and a power injection power supply voltage detection section 3-3 for measuring the injection level of the current injection power supply 3-1-A, and an insulation resistance current calculation section 3 for calculating the insulation resistance current by inputting the injection voltage and current. 4 is provided.

(Embodiment 2) In Embodiment 2, in addition to Embodiment 1, a connection is made so that a test current is always injected by the current injection transformer 4A, and the injected current exceeds a specific value. In this case, that is, if the insulation resistance becomes extremely poor and a large ground line current flows, the current may be regarded as a resistance component current. In this state, the current injection transformer 4A is connected to the current injection power supply 3- 1B is connected to the ground line current detection section 3-2-2 via a switch 3-6. Then, the ground line current is measured via the current injection transformer 4A, and the detected current is used as the insulation resistance current. Therefore, in the second embodiment, the current injection power supply 3-1B, the injection current detection unit 3-2-1 for detecting the injection current via the sensor 3-5, and the current injection transformer 4A are connected to the current injection power supply 3-A. 1B or ground line current detector 3
Switch 3-6 for switching connection to any of -2-2
A ground line current detection unit 3-2-2, a current injection power supply voltage detection unit 3-3, and an insulation resistance component current calculation unit 3 that calculates an insulation resistance component current by inputting the detected injection voltage and current.
-4, and an insulation resistance component current identification unit 3-6 that sets the current of the ground line current detection unit 3-4 to the insulation resistance component current when the current obtained by the insulation resistance component current calculation unit exceeds a specific value. It is provided.

(Embodiment 3) In Embodiment 3, as shown in FIG. 4, the current injected from the current injection power supply 3-1B into the current injection transformer 4A is such that the test low-frequency current f1 and the high-frequency current f2 are equal to each other. It is configured to be superimposed and injected.
Therefore, when viewed from the current injection transformer 4A, the injection is performed as a high-frequency current.
Since the magnetic flux density of the core A is inversely proportional to the frequency, it has the effect of reducing the core cross-sectional area of the current injection transformer 4A. The current injection power supply 3-1B according to the third embodiment includes a low-frequency power supply 3-1-2 and a high-frequency power supply 3-1.
-1 and a low-frequency / high-frequency combined power supply 3-1-3 for combining the currents of the two power supplies.

(Embodiment 4) Embodiment 4 shows another example of an insulation monitoring device using the current injection power supply 3-1B of Embodiment 3. That is, in the fourth embodiment, as shown in FIG. 5, of the currents injected into the ground line 2, the test low-frequency current is detected before being superimposed on the high-frequency current, and is detected from the test injection current and the injection voltage. This is an insulation monitoring device for obtaining a current corresponding to an insulation resistance. This configuration has the effect that it is not necessary to separate and measure only the test low-frequency current from the current injected into the current injection transformer 4A of the third embodiment by a filter. In the fourth embodiment, a current injection power supply 3-1B for injecting a test current into the current injection transformer 4, a current injection power supply voltage detection unit 3-3, and a low-frequency power supply A current detection unit 3-2 for detecting a frequency current via a sensor 3-5; and an insulation resistance component current calculation unit 3 for calculating the insulation resistance component current by inputting the injection voltage and current.
4 is provided.

[0017]

As is clear from the above description, according to the means of the present invention, the following excellent effects can be obtained. (1) According to the first means of the present invention, a current transformer for detecting a ground line current is not required, and a means for separating an injection test current from a current other than the test current is unnecessary because the injection test current is measured on the injection side.
In addition, there is an effect that measurement can be performed with high accuracy because a single waveform is measured. (2) According to the second means of the present invention, the current transformer for current detection is unnecessary even though the ground line current is detected, and the capacity of the current injection power supply and the capacity of the current injection current transformer are reduced. It has the effect of miniaturization. (3) According to the third means of the present invention, there is an effect that the current injection current transformer can be significantly reduced in size. (4) According to the fourth means of the present invention, there is an effect that a filter is not required for detecting the test low-frequency current in the injection current of the third means.

[Brief description of the drawings]

FIG. 1 is a block diagram of an insulation monitoring device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an insulation monitoring device according to the second embodiment;

FIG. 3 is a block diagram of a current injection power supply of the insulation monitoring device according to the third embodiment;

FIG. 4 is an injection current waveform diagram of the third embodiment.

FIG. 5 is a block diagram of an insulation monitoring device according to the fourth embodiment.

FIG. 6 is a block diagram showing a configuration in which a conventional insulation monitoring device is installed on a ground wire of a power receiving transformer.

[Explanation of symbols]

 3A, 3B, 3C Insulation monitoring device 3-1A, 3-1B Current injection power supply 3-1-1 High frequency power supply 3-1-2 Low frequency power supply 3-1-3 Low frequency / high frequency combined power supply 3-2 Current detector 3-2-1 Injection current detection unit 3-2-2 Ground line current detection unit 3-4 Insulation resistance component current calculation unit 3-6 Switch 3-7 Insulation resistance component current specifying unit 4A Current injection transformer

Claims (4)

[Claims] 1. A current injection power supply for injecting a test current for detecting an insulation resistance component current into a current injection transformer, a current injection power supply voltage detection unit, and a primary side of a current injection transformer for injecting an injection current of the current injection power supply. An insulation monitoring device comprising: a current detection unit that detects the current by using the current injection power supply voltage and the injection current that have been detected. 2. A current injection power supply for injecting a test current into a current injection transformer installed on a ground line, a current injection power supply voltage detection unit, an injection current detection unit, and a ground line current detection unit. An insulation resistance component current calculation unit that obtains an insulation resistance component current by calculation by using a detection voltage of the current injection power supply voltage detection unit and a detection current from the injection current detection unit as inputs, and the insulation resistance component current calculation unit When the current obtained in step (c) exceeds a specific value, a switch is provided for switching the connection of the current injection transformer from the current injection power supply to the ground line current detection unit side, and the ground line current is detected via the current injection transformer. An insulation monitoring device comprising: a ground line current detection unit; and an insulation resistance component current specification unit that specifies an insulation resistance component current based on the ground line current. 3. A current injection power supply includes a test low-frequency power supply and a high-frequency power supply, and a low-frequency / high-frequency combined power supply for combining the test low-frequency current and the high-frequency current from the two power supplies, and a ground line. 3. The insulation monitoring device according to claim 2, wherein the test current is injected into a current injection transformer installed in the device. 4. An injection current detecting section for detecting a low-frequency current before superimposing a low-frequency test current on a high-frequency current among the currents injected into the ground line, and insulated from the test injection current and the injection voltage. 4. The insulation monitoring device according to claim 3, wherein a resistance component current is obtained.