JP3602904B2 - Alarm detection test equipment for insulation monitoring equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to 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 in a ground line in order to monitor an insulation state of an AC circuit.
[0002]
[Prior art]
Conventionally, a ground fault detector and a ground fault protection relay have 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. Although these tests were originally performed with the power supply interrupted, it is now required that the test be performed in a charged state of the electrical circuit in order to reduce the power outage time and eliminate the power outage.
[0003]
Also, in the state of electric circuit charging, the leakage current flowing back to the ground line often fluctuates depending on the load state of the target electric circuit, making it difficult to accurately determine the alarm detection level. The ground fault protection relay has a relatively large operation detection level of several hundred mA, so that even if the leakage current slightly changes, the influence on the alarm detection level is relatively small, and the alarm detection test can be performed. .
[0004]
As shown in FIG. 2 , the insulation monitoring device connects a current transformer (ZCT) 33 to a ground line 31 and detects a leakage current I ₀ flowing through the ground line 31 via a current transformer (ZCT) 33. 35. The leakage current I ₀ is the leakage current I ₁ leaking from the first line 51, the leakage current I ₂ leaking from the second line 52, the leakage current I ₃ leaking from the first load 53, the second current The sum of the leakage current I ₄ leaking from the load 54 and the leakage current I ₅ leaking from the third load 55 (I ₀ = I ₁ + I ₂ + I ₃ + I ₄ + I ₅ ).
[0005]
The alarm detection test apparatus for testing the alarm detection level converts a test signal generated by a test signal generator including an oscillator 37, a variable resistor 39, and a meter 41 into a current transformer (ZCT) as shown in FIG. ) 33 to a detector 35, which tests whether the detector 35 can detect leakage current with a predetermined alarm detection level with high accuracy.
[0006]
Conventionally, such a test is performed by turning off the switch 42 in FIG. 2 and removing the influence of the leakage current flowing to the load. That is, the insulation monitoring device has a low alarm detection level of several tens of mA, and if the leakage current fluctuates, it is difficult to accurately determine the alarm detection level. I went off.
[0007]
[Problems to be solved by the invention]
As described above, the conventional alarm detection test device of the insulation monitoring device performs the test of the alarm detection level by turning off the switch 42. However, due to recent demands for shortening the power outage time and uninterruptible power supply, It is required to perform the test with the switch turned on, that is, in the charged state of the circuit.In this state, it is necessary to determine the alarm detection level with high accuracy due to the influence of the leakage current that fluctuates to the load. There is a problem that is difficult.
[0008]
The present invention has been made in view of the above, and an object of the present invention is to detect an alarm of an insulation monitoring device capable of determining an insulation detection level with high accuracy without being affected by a leakage current flowing back to a ground line. To provide a test device.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, an alarm detection 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 line in order to monitor an insulation state of an AC circuit. A test apparatus, comprising: a test signal generating means for generating a test signal ; a current transformer coupled to a ground line for detecting a leakage current flowing through the ground line and a test signal from the test signal generating means; And only the leakage current component flowing through the ground wire is extracted by the filter means, the extracted leakage current component is amplified, and a suppression current substantially corresponding to the leakage current is supplied to the current transformer in the direction in which the leakage current flows. is a suppression unit that teapot subjected to reverse direction, which is connected to the current transformer, and summarized in that with the detection means for detecting the current and the test signal of the sum of the suppression current and the leakage current I do.
[0010]
According to the first aspect of the present invention, since the leakage current flowing back to the ground line as viewed from the detection means is a sum of the suppression current and the current, the leakage current can be reduced to a predetermined small value or less . The insulation detection level can be determined with high accuracy without being affected by the fluctuation of the leakage current flowing back to the ground line.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 is a circuit diagram showing a configuration of an alarm detection test device of an insulation monitoring device according to one embodiment of the present invention. This alarm detection test apparatus 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. Although the same operation as that shown in FIG. 2 is performed, this detection operation can be performed in a state where the switch 42 is closed and the current transformer ( A current transformer (ZCT) 45 separate from the ZCT 33 is provided. The current transformer (ZCT) 45 detects a leakage current I ₀ flowing through the ground line 31, and the detected leakage current I ₀ is suppressed by a suppression circuit 43. To supply.
[0013]
Suppression circuit 43 amplifies the leakage current I _o from the current transformer (ZCT) 45, extracts only the leakage current component therefrom by current transformer (ZCT) 33 filter having a frequency characteristic equivalent to the characteristics of, the extraction It was to amplify the leakage current component, suppressing current corresponds approximately to the leakage current (0.99I _o) current transformer in the opposite direction to the direction of flow of the leakage current (ZCT) 45 and current transformer (ZCT) 33 to suppress the influence of leakage current to a predetermined small value or less.
[0014]
Now, if the amplification degree of the suppression circuit 43 assuming 100, an output _{I x} of the current transformer (ZCT) 33 is expressed by the following equation in the primary current conversion.
[0015]
I _x = I _b /100=0.01×I _o
That is, since the detector 35 leakage current flows back to the ground line 31 as viewed from the _{I o} is one hundredth (1/100), even as the fluctuation of the leakage current _{I o} is generated by the load variation, the detector 35 Is reduced to 1/100, and the detector 35 can detect the insulation detection level with high accuracy without being affected by the fluctuation of the leakage current flowing back to the ground line. That is, even when the insulation monitoring device detects a relatively small leakage current _Io , the alarm detection test device of the insulation monitoring device can perform an alarm without any influence of the leakage current when the circuit is charged, that is, when the switch 42 is closed. The detection level can be determined with high accuracy.
[0018]
【The invention's effect】
As described above, according to the present invention, a test signal generating means for generating a test signal, a transformer connected to a ground line and detecting a leakage current flowing through the ground line and a test signal from the test signal generating means. the flow device is connected to the ground line, only the leakage current component flowing through the ground line extraction filter unit, amplifies the extracted leakage current component, substantially corresponding to suppress current to the leakage current to the current transformer and suppression means for subjected fed in the opposite direction to the direction of flow of the leakage current, is connected to the current transformer, and a detection means for detecting the current and the test signal of the sum of the suppression current and the leakage current since a configuration, leakage current flows back to the ground line as viewed from the detecting means can be reduced to less than a predetermined small value for the current of the sum of the suppression current, thereby, leakage reflux to the ground line of the variation of the current model Without receiving the sound, it is possible to determine the insulation detection level with high accuracy.
[Brief description of the 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 of a conventional alarm detection test device of an insulation monitoring device.
[Explanation of symbols]
31 Grounding wire 33, 45 Current transformer (ZCT)
35 Detector 37 Oscillator 39 Variable resistor 41 Meter 43 Suppression circuit

Claims (1)

An alarm detection test device of an insulation monitoring device that tests an insulation detection level of an insulation monitoring device that detects a leakage current flowing through a ground line to monitor an insulation state of an AC power line,
Test signal generating means for generating a test signal;
A current transformer connected to a ground line, for detecting a leakage current flowing through the ground line and a test signal from the test signal generating means ;
Only the leakage current component connected to the ground line and flowing through the ground line is extracted by the filter means, the extracted leakage current component is amplified, and a suppression current substantially corresponding to the leakage current flows through the current transformer. and suppressing means that teapot subjected in the opposite direction to the direction,
Detection means connected to the current transformer, for detecting the current of the sum of the leakage current and the suppression current and the test signal,
An alarm detection test device for an insulation monitoring device, comprising:

Images