JPH09229985A - Testing device for warning detection of insulation monitoring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a testing device for the warning detection of an insulation monitoring apparatus, by which an insulation detection level can be judged with high accuracy without being influenced by a leakage current which is returned to a grounding conductor. SOLUTION: A leakage current I0 which is returned to a grounding conductor 31 is supplied to a suppression circuit 43 via a current transformer (ZCT) 45 so as to be applied in the suppression circuit 43, and only a leakage current component is taken out by a filter so as to be amplified. Then, a suppression current which corresponds nearly to the leakage current is supplied in the reverse direction, and the influence of the leakage current I0 is suppressed to a prescribed small value or lower. Thereby, the influence of the leakage current is eliminated, and warning detection level can be judged with high accuracy in a detector 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alarm detecting / testing device for an insulation monitoring device for testing the insulation detection level of an insulation monitoring device for detecting a leakage current flowing through a ground wire to monitor the insulation state of an AC electric circuit.

[0002]

2. Description of the Related Art Conventionally, a ground fault detector or a ground fault protective relay has been used for detecting and protecting a ground fault on a low-voltage path, but the operation detection current of these is generally several hundred mA. Originally, these tests were performed after power failure of the electric circuit, but in order to shorten the power failure time and make the power uninterrupted, it is required to be performed in a charged state of the electric circuit.

Further, in the electric circuit charged state, the leakage current flowing back to the ground line often changes depending on the load state of the target electric circuit, which makes it difficult to accurately determine the alarm detection level. Since the detector and ground fault protection relay have a relatively large operation detection level of several hundred mA, even if the leakage current changes a little, the alarm detection level is relatively less affected and the alarm detection test can be performed. Has become.

In the insulation monitoring device, as shown in FIG. 3, a current transformer (ZCT) 33 is connected to a ground wire 31, and this ground wire 3 is connected.
The leakage current I _o flowing through the No. 1 is supplied to the detector 35 via the current transformer (ZCT) 33. The leak current I _o is the leak current I leaking from the first line 51.
₁ , leakage current I ₂ leaking from the second line 52, first
Leakage current I ₃ leaking from the load 53 of the second load 54
Of the leakage current I ₄ leaking from the third load 55 and the leakage current I ₅ leaking from the third load 55 (I _o = I ₁ + I ₂ + I ₃ + I ₄ +
I ₅ ).

The alarm detection test device for testing the alarm detection level is, as shown in FIG.
A test signal generated by a test signal generator including a variable resistor 39 and a meter 41 is supplied to a detector 35 via a current transformer (ZCT) 33, whereby the detector 35 detects a leakage current by a predetermined alarm. We are testing whether or not it can be detected with high accuracy at the level.

Incidentally, such a test is conventionally performed by turning off the switch 42 in FIG. 3 to remove the influence of the leakage current flowing through the load. That is, since the insulation monitoring device has an alarm detection level as low as several tens of mA, if the leakage current fluctuates, it is difficult to accurately determine the alarm detection level. I'm off.

[0007]

As described above, in the conventional alarm detection test device of the insulation monitoring device, the switch 42 is turned off to perform the alarm detection level test. In recent years, however, the power outage time has been shortened. It is required to perform the test while the switch is on, that is, in the state where the circuit is charged, due to the demands for switching on and uninterruptible power supply. There is a problem that it is difficult to determine the detection level with high accuracy.

[0008] The present invention has been made in view of the above,
It is an object of the present invention to provide an alarm detection test device of an insulation monitoring device capable of highly accurately determining an insulation detection level without being affected by a leakage current flowing back to a ground line.

[0009]

In order to achieve the above object, the present invention as set forth in claim 1, is an insulation detection level of an insulation monitoring device for detecting a leakage current flowing in a ground wire to monitor an insulation state of an AC electric circuit. An alarm detection test device of an insulation monitoring device for testing a test signal generating means for generating a test signal, a test signal superposing means for superposing a test signal from the test signal generating means on the ground line, and a ground line. Connected to the ground line, only the leakage current component flowing through the ground line is extracted by the filter means, the extracted leakage current component is amplified, and the suppression current substantially equivalent to the leakage current is supplied in the direction opposite to the leakage current flowing direction. The gist of the present invention is to have a suppression unit that supplies the leakage current to a predetermined small value or less, and a detection unit that is connected to the ground line and that detects the test signal flowing through the ground line.

According to the first aspect of the present invention, only the leakage current component flowing through the ground line is taken out by the filter means of the suppressing means, and the suppression current substantially corresponding to the taken out leakage current component is in the leakage current flowing direction. Since the test signal flowing through the ground line is detected after supplying the current in the opposite direction to reduce the leakage current below a specified small value, it is not affected by the leakage current flowing back to the ground line. The insulation detection level can be determined with high accuracy.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing the configuration of an alarm detection test device of an insulation monitoring device according to an embodiment of the present invention. This alarm detection test device has a circuit configuration until a test signal generated by a test signal generator including an oscillator 37, a variable resistor 39 and a meter 41 is supplied to a detector 35 via a current transformer (ZCT) 33. As shown in FIG. 3, this current detecting device is connected to the ground line 31 in order to eliminate the influence of leakage current so that the detecting operation can be performed in the electric circuit charging state in which the switch 42 is closed. The current transformer (ZCT) 45, which is different from the ZCT) 33, is provided.
The leak current I _o flowing through the ground line 31 is detected at 45, and the detected leak current I _o is supplied to the suppression circuit 43.

The suppression circuit 43 amplifies the leakage current I _o from the current transformer (ZCT) 45 and then the current transformer (ZCT).
Only a leakage current component is extracted by a filter having a characteristic equivalent to the frequency characteristic of 33, the extracted leakage current component is amplified, and a suppression current (0.99I _o ) substantially equivalent to the leakage current flows as a leakage current. The current is supplied in the direction opposite to the direction via the current transformer (ZCT) 45 and the current transformer (ZCT) 33, whereby the influence of the leakage current is suppressed below a predetermined small value.

Now, assuming that the amplification degree of the suppression circuit 43 is 100, the output I _x of the current transformer (ZCT) 33 is expressed by the following equation in terms of primary current.

I _x = I _b /100=0.01×I _o That is, the leakage current I _o flowing back to the ground line 31 as seen from the detector 35 is 1/100 (1/100), and therefore the load Even if the fluctuation causes the fluctuation of the leakage current I _o , the influence of the leakage current on the detector 35 is suppressed to 1/100, and is not affected by the fluctuation of the leakage current flowing back to the ground line. The detector 35 can detect the insulation detection level with high accuracy. That is, even when the insulation monitoring device detects a relatively small leakage current I _o ,
The alarm detection test device of the insulation monitoring device can determine the alarm detection level with high accuracy in the electric circuit charging state, that is, in the state where the switch 42 is closed without the influence of the leakage current.

FIG. 2 is a circuit diagram showing a configuration according to another embodiment of the present invention. This figure shows that the monitoring signal that is different from the commercial frequency is injected into the grounding wire of the second class grounding work of the transformer by an electromagnetic method, etc., and the insulation of the electric circuit is constantly monitored by the effective part of the leakage current of this monitoring signal. The alarm detection test device of the present invention is applied to an insulation monitoring device.

That is, in FIG. 2, the monitoring signal I _g from the effective type insulation monitoring device 47 is a current transformer (CT) 49.
The leakage current I _o and the monitoring current I _{g, which} are injected into the ground line 31 through the ground line 31 and flow through the ground line 31, are (I _o
+ I _g ) / 100 and is supplied to the insulation monitoring device 47, and the alarm detection level can be detected with high accuracy without being affected by the leakage current and the monitoring current.

[0018]

As described above, according to the present invention,
Only the leak current component flowing through the ground line is taken out by the filter means, and the suppression current substantially corresponding to the taken leak current component is supplied in the direction opposite to the leak current flowing direction,
The test signal flowing through the ground line is detected after the leak current is reduced to a predetermined small value or less, so the insulation detection level can be determined with high accuracy without being affected by the fluctuating leak current flowing back to the ground line. can do.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of an alarm detection test device of an insulation monitoring device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration according to another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of an alarm detection test device of a conventional insulation monitoring device.

[Explanation of symbols]

 31 Ground Wire 33, 45 Current Transformer (ZCT) 35 Detector 37 Oscillator 39 Variable Resistor 41 Meter 43 Suppression Circuit

Claims (1)

[Claims] 1. An alarm detection test device of an insulation monitoring device for testing an insulation detection level of an insulation monitoring device for detecting a leakage current flowing through a ground wire to monitor an insulation state of an AC electric circuit, the test signal being generated. Test signal generating means, test signal superimposing means for superimposing the test signal from the test signal generating means on the ground line, and a leak current component connected to the ground line and flowing through the ground line. Suppressing means for amplifying the extracted leakage current component and supplying a suppression current substantially equivalent to the leakage current in the direction opposite to the leakage current flowing direction to reduce the leakage current to a predetermined small value or less; An alarm detection test device for an insulation monitoring device, comprising: a detection unit that is connected to a wire and detects the test signal that flows to a ground wire.