JP3240185B2 - Method and apparatus for determining insulation deterioration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for judging insulation deterioration and an apparatus therefor, and more particularly to a means for correctly judging the state of insulation deterioration of a low-voltage path.

[0002]

2. Description of the Related Art A conventional insulation monitoring device for a low-voltage circuit is shown in FIG. This device applies a low-frequency measurement signal voltage different from the commercial frequency to electric lines 3, 4, and 5 via a ground wire 2 connected between a low-voltage path of a transformer T for converting a high-voltage power supply to a low voltage and a ground. The leakage current flowing through the injection transformer 6 and flowing back to the ground line is detected by the current transformer 7, and a current component in phase with the signal voltage for measurement, that is, an effective component current is detected. And the insulation resistance to the ground of the low-voltage path ｛1 / R = (1 / R ₁ ) + (1 / R ₂ ) +
(1 / R ₃ )｝ is monitored.

In FIG. 3, R ₁ , R ₂ , and R ₃ are insulation resistances between each electric circuit and the ground, and C ₁ , C ₂ , and C ₃ are capacitances between the electric circuit and the earth. These mean the sum including the insulation resistance and the earth capacitance of each load device connected to the electric circuit. That is, the conventional insulation monitoring device 1
Then, the insulation resistance R of the electric circuit is 1 / R = (1 / R ₁ ) + (1
/ R ₂ ) + (1 / R ₃ ) are collectively calculated using the effective component current. On the other hand, it is general to issue an alarm when the effective component current becomes equal to or more than a predetermined value as a result of the above measurement, but this detection threshold is a fixed value,
It is determined regardless of the number of load devices. However, as the number of load devices increases, the effective component current, which is naturally inversely proportional to the insulation resistance measured collectively, increases even if the insulation characteristics are sound, so insulation monitoring can be performed regardless of this fact. With the conventional monitoring method that has been performed, it has been difficult to make a correct determination of insulation deterioration from an alarm that is issued regardless of the operation state of the load device.

[0004] The insulation deterioration judging means is effective not only for the above-mentioned power transmission line but also for a wide range of earth resistance of a lightning arrester, and insulation deterioration between a circuit of an electronic device and a housing. .

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to eliminate the disadvantages of the conventional method for judging the state of insulation deterioration of an electric circuit or the like. It is an object of the present invention to provide a method and apparatus capable of accurately determining insulation deterioration regardless of a change.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a method for measuring an electric circuit or an impedance circuit having at least one end connected to the ground or another conductor through a connection line. It applies a frequency signal, effective component and disable the low-frequency signal the measurement refluxing the connecting line
Min detects or calculates the insulation resistance value between the electric path or the impedance circuit and earth or between other conductor on the basis of the active component, with or deriving a signal corresponding to the resistance value,
Detecting a change in increase and decrease of the reactive component, absolute based on the active component
The edge resistance value or a signal corresponding to the resistance value exceeds a predetermined reference value.
When the value of the invalid component is
If the increase is due to true insulation degradation
When it is determined that there is no increase and the invalid component does not increase,
By determining that this is due to true insulation degradation,
Thus , insulation deterioration can be accurately determined.

Further, in an apparatus for judging insulation deterioration between the earth or another conductor of an electric circuit or an impedance circuit having at least one end connected to the earth or another conductor via an insulating wire, a low-frequency signal source for measurement is provided. Means for applying the low-frequency signal for measurement to the electric circuit or impedance circuit, means for detecting an effective component and an invalid component of a leak signal of the applied low-frequency signal, and a circuit or impedance circuit from the effective component. means for determining the insulation resistance between earth or another conductor, and means for detecting an increase or decrease of the reactive component, wherein the active component
When the insulation resistance value based on exceeds a predetermined reference value,
Refer to the increase / decrease change of the invalid component, and if the invalid component is increasing,
In this case, it is determined that it is not due to true insulation deterioration,
If the reactive component does not increase, it is due to true insulation deterioration.
Means for judging that they are the ones.

When this method is applied to the judgment of insulation deterioration of an electric circuit, not only an effective component current inversely proportional to the insulation resistance but also a reactive component current proportional to the ground capacitance, that is, a measuring current applied to the electric circuit, A leakage current that is 90 degrees ahead of the signal voltage is detected, and insulation deterioration is determined based on the values of the two. That is, according to this method, since the reactive component current is proportional to the ground capacitance, the change in the reactive component current increases and decreases in relation to the number of operating load devices. Therefore, an accurate determination can be made by taking into account the operating state of the load device.

To explain this briefly, FIG. 4 is an actual measurement example of the active component current (a) and the reactive component current (b). This is a measurement of a low-voltage path (single-phase three-wire) at a certain factory. The effective component and the reactive component current both increase with the start of operation of the load device, and decrease with the stop of the operation. Since each load device has its own ground capacitance, the operating status of the load device can be estimated from the magnitude of the reactive current. It can be said that the capacitance to ground of each load device is almost independent of the insulation resistance of the load device, and is related to the structure thereof, the capacitance of the AC noise removing filter used in the load device, and the like.

Therefore, when the effective component current exceeds a predetermined value (alarm value), if the increase or decrease of the reactive component current at that time is known, the state of insulation deterioration can be determined in more detail. For example, when the active component current becomes a predetermined value or more, if the reactive component current does not change or shows a decreasing tendency,
This is not due to an increase in the number of operating load devices, but to the fact that insulation degradation has occurred in the operating devices. In particular, when the reactive component current tends to decrease, the number of operating load devices decreases, so when the active component current increases, the degree of insulation deterioration is large, and further attention is required. In some cases, maintenance is determined to be necessary. Naturally, when the reactive component current is on the increase, it can be said that the effective component current is increased due to the increase in the number of operating load devices and the insulation deterioration is combined.However, the degree of insulation deterioration is judged to be somewhat lighter than when the load device is reduced. I can do it.

As described above, it is possible to determine the necessity of the insulation deterioration investigation or the maintenance or repair by using the temporal change information of the reactive current together with the active current. Further, if the above-mentioned alarm value for generating an alarm is combined with the increase / decrease of the invalid component value in two steps and the above-described processing is performed when the effective component current exceeds each alarm value, more detailed monitoring and Necessary measures can be taken.
In particular, when receiving and processing an alarm signal from a monitoring device installed in a remote place, it is uneconomical to constantly transmit the detected valid and reactive currents to a remote place, but the above-mentioned method makes the alarm value effective. Only when the minute current exceeds,
Since the status of the reactive current can be transmitted, it is more effective to remotely monitor a large number of insulation monitoring devices at one place.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the accompanying drawings. FIG. 1 illustrates the method of the invention in single phase 3
FIG. 2 is a block diagram showing an embodiment of an insulation deterioration measuring device to be applied to a wire type electric circuit. In the figure, T is a transformer for converting high-voltage electricity to low-voltage electricity, and the electric lines 3, 4, and 5 are connected to its secondary side, and furthermore, a connection line (hereinafter referred to as a middle line 4) is connected to the ground. 2 is provided.

Further, a zero-phase current transformer 6 and an injection transformer 7 are coupled to the ground line 2, and an amplifier 8 is connected to the injection transformer 7.
Applying the output of the low frequency oscillator 9 via which the frequency f ₁ between the path 3, 4, 5 and the ground by (= ω _1/2
π) is applied.

On the other hand, the output of the zero-phase current transformer 6 coupled to the ground line 2 is amplified by an amplifier 10, and the output is applied to a filter 11 for separating a commercial frequency component and a frequency component of a measurement signal, and is applied to an electric circuit. A leakage current component due to the measured signal voltage is detected. The output of the filter 11 is two synchronous detectors 1
2 and 13 are applied to one of the input terminals. The output of the oscillator 9 is further applied to another input terminal of the synchronous detector 12 through a variable phase shifter 14, and the output of the variable phase shifter 14 is 90 degrees. The signal is applied to another input terminal of another synchronous detector 13 via the phase shifter 15. In addition, the synchronous detector 12
Is applied to one input terminal of each of two level comparators 17 and 18 via a low-pass filter 16. On the other hand, the output of the synchronous detector 13 is input to a differentiating circuit 20 via a low-pass filter 19. The output of the differentiating circuit 20 is input to one input terminal of each of the other two level comparators 21 and 22. The level comparators 17, 18, 2
Each of the other inputs of ₁ , 2 has its own reference voltage V ₁ ,
V ₂ , V ₃ and V ₄ are set.

The operation and control method of the above configuration will be described. First, both the leakage current due to the commercial frequency voltage of the electric circuits 3 and 5 and the leakage current due to the signal voltage for measurement return to the ground line 2 via insulation resistance and capacitance. Therefore, this current is detected by the zero-phase current transformer 6, amplified by the amplifier 10, and
If only the frequency component of the measurement signal is separated by the filter 11, the output Ig of the filter 11 can be obtained as a signal proportional to the following equation.

Ig = {(e / R) · sin ω ₁ t} + ωce · cos ω ₁ t (1) where 1 / R = (1 / R ₁ ) + (1 / R ₂ ) + (1 / R ₃ ), C = C ₁ + C ₂ + C ₃ . Known as the (1) right side first term active current of the second term is a reactive current. At this time, if the phase is adjusted so that the output voltage of the variable phase shifter 14 becomes e ₁ sinω ₁ t, the output Igr of the low-pass filter 16 becomes Igr = ee ₁ / R (2) output Igc of the low-pass filter 19 becomes _{Igc = ωce 1 e ··· (3} ). Here, since e and e ₁ are constant, Igr is inversely proportional to the insulation resistance R, and Igc is proportional to the ground capacitance.

FIG. 2 shows an example of an output waveform of each unit. In practice, each circuit of FIG. 1 can be realized by a digital operation circuit. However, in order to make the contents of the processing easy to understand, the waveform of each unit is converted into an analog signal. Indicated.

[0018] FIG. (B) The output of the filter 16, that is, the waveform of the effective component current Igr of measuring low-frequency signals flowing back to the ground line 2, Igr shown in this example time t ₁ ~
t exceed the ₂ and t ₃ ~t ₆ the first reference potential V1, it is further at the t ₄ ~t ₅ has become that exceeds the second reference voltage V2.

In this case, the output of the first comparator 17 having V1 as a reference potential generates a high potential at t _{1 to} t ₂ and t _{3 to} t _{6 as} shown in FIG. the output of the second comparator 18, the reference potential is a high potential in t ₄ ~t ₅ as shown in (e).

On the other hand, FIG. 2B shows a second synchronous detector 1.
3 shows a waveform obtained through the low-pass filter 19, that is, a waveform of the reactive component current Igc of the low-frequency signal for measurement which returns to the ground line 2 via the ground. FIG. 20 is a waveform I′gc passed through 20. (B)
Is differentiated as positive or negative depending on the inclination direction, and the reference voltages V of the third and fourth comparators 21 and 22 are differentiated.
_{If 3} and V ₄ are set as shown in FIG. 3C, the output of the comparator 21 is I′gc> V ₃ as shown in FIG.
1 ", and (g) as when the output of the comparator 22 I'gc <V _4" "next, in other cases," 1 0 ".

Therefore, an alarm signal is generated or insulation deterioration is determined as follows using the outputs of the above-described comparators. That is, at t = t ₁ , the effective component of the low-frequency signal for measurement returns to the ground line beyond the reference value V ₁ as shown in (a), so this V ₁ value is set as the first insulation deterioration alarm. At this time, since the output 25 of the third comparator 21 is "1", it is understood that the invalid component of the electric circuit to be measured has increased. As described above, among the load devices connected to the electric circuit, when the number in the operating state increases, the effective component and the ineffective component both increase with the increase.
It looks as if the insulation resistance had dropped, and according to the conventional insulation deterioration determination method, an alarm was immediately generated in this state.

Conventionally, upon receiving this warning, it is necessary to investigate whether the insulation is genuinely deteriorated or to increase the number of load devices in operation, or assume that the insulation is genuinely deteriorated for the time being. The inefficient work of searching for a defective part was performed. Therefore, in the present invention, when the first alarm is generated, the increase or decrease of the ineffective component is detected and referred to at the time of the first alarm generation, and the increase in the effective component, that is, the degree of the insulation resistance deterioration and the increase in the ineffective component are considered. It is determined whether or not the insulation resistance has deteriorated.

For example, the case shown in FIG. 2 will be described. In the period from t ₁ to t ₂ , the output of the third comparator 21 is “1” although it exceeds the _first alarm level V 1. , It can be understood that this is due to an increase in the number of operating load devices.

On the other hand, from t _{3 to} t ₆ , the outputs 23 and 24 of the first and second comparators 17 and 18 both become “1”, but the output of the fourth comparator 22 at this time is “1”. Output 26 is "1"
Indicates that the number of operating load devices has decreased. Therefore, in this case, despite the decrease in the number of operation of the load devices, it means that the effective component has increased, that is, the insulation resistance has decreased, and thus it is found that the insulation is truly deteriorated.

As described above, the present invention judges true insulation deterioration by adding means for detecting an increase or decrease of an invalid component to the conventional insulation deterioration detection means.
It goes without saying that various modifications are possible in the implementation. For example, in making the determination, the worker can make a determination by looking at the output value of each of the comparators, but it is also possible to determine the state of each output by a logic circuit and control whether or not an alarm is generated. Outputs 23, 24, 25, 2
6 to a remote location via a modem or the like, or output 23,
Alternatively, if the state of the outputs 25 and 26 is transmitted when 24 becomes "1", abundant information can be received at a remote place without transmitting constantly, and the response range is limited. Can be. Also by applying a low-frequency voltage having a frequency f ₁ to the path in the above embodiment, the effective amount, but detects the reactive current, etc. to detect these by applying a voltage of two-frequency it is not limited to this method Obviously, other methods may be used. In addition, such a means is not limited to the power transmission line, and is applicable to a wide range such as deterioration of the grounding resistance of a lightning arrester, insulation measurement of an antenna such as an antenna, or insulation measurement between an internal circuit of an electronic device and a housing. It is possible.

[0026]

As described above, according to the present invention, not only the insulation deterioration information due to the active component current but also the insulation deterioration due to the change in the number of operating load devices can be determined based on the change in the ground capacitance due to the reactive component current. This is extremely effective in enabling an effective response system when an alarm occurs.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIGS. 2A to 2G are diagrams showing waveforms for understanding the operation status of each unit in FIG. 1;

FIG. 3 is an explanatory diagram of a conventional insulation monitoring device.

FIGS. 4A and 4B are diagrams showing a relationship between an active component current and a reactive component current.

[Explanation of symbols]

2 Ground wire, 3, 4, 5 circuit, 6 current transformer, 7 injection transformer, 8, 10 amplifier, 9 oscillator, 11 filter, 12, 13 synchronous detector, 14 variable phase shifter, 1
5 90 ° phase shifter, 16, 19 Low-pass filter, 2
0 Differentiator circuit, 17, 18, 21, 22 Level comparator, T transformer.

Claims (2)

(57) [Claims] To claim 1 wherein at least one end connected path or impedance circuit to ground or other conductive via the connection line, and applies a low-frequency signal measured via the front Symbol connecting line, before Symbol connecting line <br/> the effective amount of the low-frequency signal the measurement refluxing detects invalid content, to calculate the insulation resistance value between the electric path or the impedance circuit and earth or between other conductor on the basis of the active component or together to derive a signal corresponding to the resistance value to detect a change in increase and decrease of the previous SL reactive component, Shin corresponding to insulation resistance value or the resistance value based on the active component
When the signal exceeds a predetermined reference value
If the ineffective component is increasing, the true insulation deterioration
If the ineffective component does not increase , it is determined that the insulation is not deteriorated.
A method for judging insulation deterioration, characterized in that insulation deterioration can be accurately judged by judging that the insulation deterioration has occurred. 2. An apparatus for judging insulation deterioration between an earth or another conductor of an electric circuit or an impedance circuit connected at least one end to the earth or another conductor via a connection line, wherein a low-frequency signal source for measurement is provided. If, before Symbol path or means for applying a low-frequency signal the measured impedance circuit, means for detecting the active component and reactive component of the leakage signal of the low frequency signal said applied electric path or the impedance circuit from the active component means for determining the insulation resistance between earth or another conductor, and means for detecting the increase or decrease in pre-Symbol reactive component, insulation resistance value based on the active component exceeds a predetermined reference value and
Sometimes, the invalid component increases by referring to the increase / decrease change of the invalid component.
If so, it is not due to true insulation degradation
Judgment, if the ineffective component does not increase, true insulation
Means for determining that the deterioration is due to deterioration.