JPH06209518A - Insulation-degradation diagnostic apparatus - Google Patents

Abstract

PURPOSE:To obtain an insulation-degradation diagnostic apparatus wherein its cost is low, its reliability is high and the maintenance of its electric installation is easy by providing a processing device which diagnoses the insulation-degradation degree of an insulation-degraded distribution feeder on the basis of a plurality of zero-phase currents. CONSTITUTION:A diagnostic apparatus is provided with a plurality of zero-phase current transformers 14 which measure a zero-phase current at each of individual feeders 12 and with a processing device 2 which takes into individual zero-phase current signals 16 output from the zero-phase current transformers 14 and which judges an insulation-degradation degree by specifying the insulation-degraded distribution feeders on the basis of the zero-phase current signals. When the insulation of an electric installation is degraded, the zero-phase current starts to increase with the time. When the current reaches a predetermined value, breakers 13 are isolated by a protective device, and the supply of electric power to loads 15 is stopped. Since the crest value of the zero-phase currents 16 output from the zero-phase current transformers 14 is actually small in this case, the currents are amplified up to a required crest value by amplifiers 17. As a result, the diagnosing apparatus whose cost is low, whose reliability is high an in which the maintenance of the electric installation is easy is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation deterioration diagnosis device for detecting and diagnosing insulation deterioration of electric equipment.

[0002]

2. Description of the Related Art Deterioration of insulation of electric equipment often progresses with time and eventually leads to a ground fault or a short circuit.
Although the mechanism of progress of insulation deterioration is complicated, it is generally as follows. First, current begins to leak from the scratches or deteriorated portions of the cable coating and the conductor supporting insulator, and the heat, pressure, ions, etc. generated by the leak currents progress damage and deterioration, and the leak current increases.

The leakage current has a very small value of several milliamperes or less at the early stage of insulation deterioration, and it is difficult to detect it in the state where the load current is flowing.

However, modern electric current equipment often has an electronic computer or the like as its load, and it is often difficult to stop the load.

Therefore, it is necessary to detect the minute leakage current and catch the insulation deterioration state in the initial state while the load current is still flowing.

Conventionally, there is the following insulation deterioration diagnosing device (Japanese Patent Laid-Open No. 4-42726). This insulation deterioration diagnosis device is usually used for GPT (Ground Potenti
A switch is provided between the neutral point and the ground. When diagnosing insulation deterioration, this switch is released, and a DC voltage is applied to both ends of the released switch to connect the power equipment to ground. The leakage current is measured, and the switch is closed after the measurement is completed. As a result of measuring the leakage current, if the predetermined reference site is exceeded, the electric equipment is stopped and the insulation deterioration of the plurality of distribution feeders is individually inspected.

[0007]

In the above-mentioned conventional technique, the GPT for detecting the ground fault is indispensable in the structure of the device, which causes an increase in the price of the device and an increase in the size of the device.

Although the conventional insulation deterioration diagnosing device can judge the insulation deterioration of the entire electric equipment, since the portion where the insulation deterioration has occurred cannot be identified, the electric equipment is stopped after detecting the insulation deterioration state. In the above, a method of separating each part and measuring the insulation resistance of each part is taken again, and there is a problem that the labor required for maintenance of the electric equipment is large.

Furthermore, when a ground fault occurs, a high voltage may be generated between the GPT neutral point and the ground, and the insulation deterioration diagnostic device may be destroyed. There is a problem that it is difficult to cope with the rapidly progressing insulation deterioration because the diagnosis must be carried out regularly for a short time.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an insulation deterioration diagnosing device which is inexpensive, highly reliable, and capable of easily maintaining electrical equipment.

[0011]

SUMMARY OF THE INVENTION An insulation deterioration diagnosing device of the present invention comprises a plurality of zero-phase current transformers for individually measuring zero-phase currents of a plurality of distribution feeders in electric equipment, and the plurality of zero-phase transformers. The zero-phase current signal output from the sink is taken in, the distribution feeder with insulation deterioration is specified based on these multiple zero-phase current signals, and the degree of insulation deterioration of the specified distribution feeder is diagnosed. And a processing device.

Further, in the insulation deterioration diagnosing device of the present invention, the processing device includes a plurality of amplifying means for individually amplifying each of the plurality of zero-phase current signals to a predetermined level, and output signals of the plurality of amplifying means. A plurality of bandpass filters for extracting the fundamental wave component of the zero-phase current, and the output signals of the plurality of bandpass filters, and of the distribution feeder in which insulation deterioration has occurred based on the output signals of the plurality of bandpass filters. And a display unit for displaying the data indicating the feeder having insulation deterioration and the degree of insulation deterioration of the feeder based on the output of the calculation unit. Characterize.

Further, in the insulation deterioration diagnosing device of the present invention, the amplifying means stores a level of a zero-phase current signal of the feeder in a state where insulation deterioration is not present, a current zero-phase current signal and the storage part. And a differential amplifier for amplifying the level difference of the zero-phase current signal at the time of non-insulation deterioration output from the.

Further, in the insulation deterioration diagnosing device of the present invention, the arithmetic means has a storage section for storing the level of the zero-phase current signal of the feeder in a state where insulation deterioration has not occurred, and the present zero-phase current of each feeder. It is characterized by having a function of calculating a difference between a signal and a zero-phase current signal output from the storage unit in a state in which insulation is not deteriorated.

Further, in the insulation deterioration diagnosing device of the present invention, the calculating means obtains the inner product of the zero-phase current vector of the distribution feeder and the zero-phase current vector of another distribution feeder, which is the reference in the electric equipment, and calculates the inner product. It is characterized in that the distribution feeder having the insulation deterioration is specified based on the code.

Further, the insulation deterioration diagnosing device of the present invention is characterized in that the Q of the band pass filter is 5 or more.

Further, the insulation deterioration diagnosing device of the present invention is characterized in that the zero-phase current transformer has a large number of turns so as to measure a zero-phase current of about 2 milliamperes flowing on the primary side.

[0018]

The insulation deterioration diagnosing device having the above structure has a zero-phase current transformer for measuring a minute zero-phase current of the feeder that distributes electricity from the bus bar to each load in order to identify the insulation deterioration portion. There is. This zero-phase current transformer has a large number of turns so that a minute zero-phase current of about 2 milliamperes can be measured.

Further, the output of the zero-phase current transformer is taken into the arithmetic unit via the amplifier and the bandpass filter, the inner product of the zero-phase current vectors is obtained, and the insulation deterioration portion is specified based on the sign. At that time, the magnitude of the zero-phase current in the state where the insulation is not deteriorated is stored for each feeder, and only the difference from the current measured value of the zero-phase current is used for the calculation.

As a result, the insulation deterioration can be diagnosed without using the GPT, and the insulation deterioration portion can be determined for each feeder.

Further, since it is less likely to be affected by noise and higher harmonics, stable insulation deterioration diagnosis can be performed.

Therefore, according to the present invention, it is possible to construct an insulation deterioration diagnosing device which is inexpensive, highly reliable, and easy to maintain.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of an insulation deterioration diagnosing device according to the present invention. The following equipment is considered as an example of the electric equipment 1 to be subjected to the insulation deterioration diagnosis of the insulation deterioration diagnosis device.

In FIG. 1, an electric equipment 1 includes a power receiving section 10 having one end connected to a commercial power source or a private power generator, a bus bar 11 connected to the other end of the power receiving section 10, and a bus bar 11.
And a plurality of feeders 12 that connect a plurality of loads 15 via a circuit breaker 13.

The insulation deterioration diagnosis device installed in the electric equipment 1 has a plurality of zero-phase current transformers 14 provided for each feeder 12 for measuring the zero-phase current of each feeder, and each feeder 12. The zero-phase current signal 16 output from the zero-phase current transformer 14 is taken in, the distribution feeder having insulation deterioration is specified based on the plurality of zero-phase current signals 16, and the specified distribution feeder is isolated. It has a processing device 2 that determines the degree of deterioration.

The processing device 2 uses a plurality of amplifiers 17 which have the zero-phase current signals 16 output from the plurality of zero-phase current transformers 14 as input signals, and output signals of the plurality of amplifiers 17 as input signals. The band pass filter 18, a calculation unit 19 that receives the output signals of the plurality of band pass filters 18 and performs a calculation process, a detection signal 30 output from the calculation unit 19 indicating a feeder with insulation deterioration, and a degree of the insulation deterioration state. The display unit 20 receives the detection signal 31 and displays the diagnosis result.

FIG. 2 shows an example of the change over time of the zero-phase current in each feeder 12 in the electric equipment 1 shown in FIG. When the insulation of the electric equipment deteriorates, the zero-phase current starts to increase with time as shown in FIG. When the zero-phase current reaches the predetermined value I1, the protective device causes the circuit breaker 13
I2 before the zero-phase current reaches the value I1 when it is known that the current is released and the power supply to the load 15 is stopped.
At this stage, if it is possible to inform the electric equipment maintainer of the occurrence of insulation deterioration in the electric equipment 1, it is possible to avoid a situation where the power supply is suddenly stopped. For that purpose, it is necessary to detect at the stage where the zero-phase current is smaller than the value I2. The value of the zero-phase current I1 when the breaker 13 is released by the protection device is generally about 200 milliamperes, and the zero-phase current is set to several tens of milliamperes in order for the maintenance person of the electric equipment to deal with it with a margin. It is necessary to repair the electric equipment when it becomes.

Therefore, as the insulation deterioration diagnosis device,
It is necessary to be able to detect a zero-phase current of a few milliamperes. Therefore, the zero-phase current transformer 14 of the insulation deterioration diagnosing device in the present embodiment has a higher detectable current than the conventional zero-phase current transformer, since the detectable current is about 100 milliamperes. The number of turns of the secondary winding is increased so that it can be detected up to. This makes it possible to measure a minute zero-phase current.

On the other hand, the zero-phase current signal 16 actually output from the zero-phase current transformer 14 has a small peak value and cannot be processed by the calculation unit 19 of the processing device 2 as it is. Amplify to a peak value (level).

However, the zero-phase current signal 16 has a waveform in which harmonics and noise are superimposed on the waveform of the fundamental frequency which is the original signal. The conventional insulation deterioration diagnosing device handles a region having a large fundamental frequency waveform component, which may cause no problem, but the insulation deterioration diagnosing device according to the present invention has to handle a region having a small fundamental frequency waveform component. The bandpass filter is important because it does not occur. As the performance required for the bandpass filter 18 in FIG. 1, about Q = 5 is required centering on the fundamental frequency in order to reduce all the harmonic components to 1% or less.

In this way, the zero-phase current signal 16 is amplified to a predetermined peak value by the amplifier 17, the fundamental frequency component is extracted by the bandpass filter 18, and then input to the arithmetic unit 19.

The computing unit 19 takes in the output signals of the plurality of bandpass filters 18, and identifies the distribution feeder having insulation deterioration and determines the degree of insulation deterioration based on the output signals of the plurality of bandpass filters 18. .

Here, the principle of specifying the feeder in which the insulation deterioration has occurred in the arithmetic unit 19 will be described with reference to FIGS. As shown in FIG. 3A, when insulation deterioration does not occur, the zero-phase current vector of each feeder is oriented in an arbitrary direction. The reason why the zero-phase current flows in each feeder in the state where the insulation deterioration does not occur is that the stray capacitances of the respective phases forming the feeder are not uniform. If insulation deterioration occurs in a particular feeder in this state, the zero-phase current vector that flows in that feeder becomes larger due to the ground current, and the zero-phase current vectors of other feeders become the zero-phase current vector of the feeder with insulation deterioration. The vector and the opposite direction are shown, and the aspect shown in FIG.

The principle that the zero-phase current vector of the feeder changes as shown in FIG. 3 due to insulation deterioration is explained as follows with reference to FIG. When the ground fault current 6a flows from the insulation deterioration part of the feeder to the ground, the return current 6b from the ground flows to the power supply side through the stray capacitance 8 of each phase. The relationship between the ground fault current 6a and the feedback current 6b at this time is as shown in the following equation.

[0035]

## EQU1 ## 6a = .SIGMA.6b (1) Therefore, the zero-phase current 7a of the feeder with insulation deterioration
Is given by

[0036]

## EQU00002 ## 7a = 6a-2.times.6b> 0 (2) A positive value, and the zero-phase current 7b of the feeder with no insulation deterioration is given by the following equation.

[0037]

[Equation 3] −2 × 6b <0 (3) Negative value. Therefore, the zero-phase current of the feeder in which insulation deterioration has occurred and the zero-phase current of the feeder in which insulation deterioration has not occurred have opposite directions in terms of vector.

The computing unit 19 carries out the following computation by utilizing the fact that the zero-phase current vector of the feeder changes as shown in FIG. 3 when the insulation deterioration occurs in this way.

First, the calculation is started when the absolute value of the zero-phase current of any of the feeders exceeds the reference value.

Next, the reference vector is selected. As a reference vector, it is theoretically possible to select the zero-phase current vector of any feeder, but in practice it is better to use the one with a large peak value as the reference, so that the absolute value of the zero-phase current is the maximum. It is better to use a zero-phase current vector

After the reference zero-phase current vector is selected, the inner product of the reference zero-phase current vector and the zero-phase current vectors of the other feeders is calculated. In this case, the feeder selected as the reference zero-phase current vector is
In the case of a feeder with insulation deterioration, the result of the inner product of the above-mentioned vectors all has a negative value. This is because the above-described state corresponds to the case where the zero-phase current vector 5e is selected as the reference zero-phase current vector in FIG. 3B, and the zero-phase current vectors of the other feeders face the opposite direction to the reference vector. Therefore, the above-mentioned inner product results are all negative values.

When the feeder selected as the reference zero-phase current vector is a feeder in which insulation deterioration does not occur, the result of the inner product of the zero-phase current vector described above is Only the inner product result of the generated zero-phase current vector of the feeder has a negative value, and the others have a positive value. This is because the above-described state corresponds to the case where the zero-phase current vector 5b other than the zero-phase current vector 5e in FIG. 3B is selected as the reference zero-phase current vector, for example. Therefore, since the angle formed by the zero-phase current vector of the feeder other than the zero-phase current vector of the feeder where the insulation deterioration occurs with the reference vector is within 90 degrees, the above-mentioned inner product result shows that the reference zero-phase current vector and the insulation deterioration occur. Only the inner product result of the zero-phase current vector of the feeder has a negative value, and the other products have a positive value.

Therefore, from the result of calculating the inner product of the reference zero-phase current vector and the zero-phase current vectors of the other feeders, it is possible to determine which feeder is the feeder with insulation deterioration.

Next, the degree of insulation deterioration is determined from the absolute value of the zero-phase current of the feeder in which the insulation deterioration specified by the above calculation result has occurred. The degree of insulation deterioration is determined by comparing the absolute value of the zero-phase current of the feeder with insulation deterioration with n reference current values.

Next, a signal 30 for specifying a feeder having insulation deterioration and a signal 31 indicating the degree of insulation deterioration of the feeder in n stages are sent from the arithmetic unit 19 to the display unit 20.
The display unit 20 displays a display showing the name or number of the feeder having insulation deterioration and the degree of insulation deterioration of the feeder by n.
The display shown in stages is made.

The maintenance staff of the electric equipment plans and executes the repair of the electric equipment according to the contents displayed on the display section 20.

Next, FIG. 5 shows the state of change of the zero-phase current when the zero-phase current in each feeder is corrected using the zero-phase current in the case where insulation deterioration does not occur.
The contents of FIGS. 5A and 5B are the same as those of FIGS.
It is the same as the content of (b). As already described with reference to FIG. 3, a zero-phase current is generated in the feeder even when insulation deterioration does not occur in the feeder. The zero-phase current generated in the state where the insulation deterioration does not occur may interfere with the arithmetic processing in the arithmetic unit 19 in FIG. That is, when the irregularities of the stray capacitances 8 of the respective phases are large, FIG.
In (b), the zero-phase current vector of two feeders in which insulation deterioration does not occur, for example, the angle formed by 5a and 5c may be 90 degrees or more. In this case, insulation deterioration due to the above-described calculation occurs. The feeder may not be accurately identified.

Therefore, the correction unit shown in FIG. 6 removes the zero-phase current generated at the time of non-insulation deterioration before processing by the calculation unit 19, and the zero-phase current vector at the time of insulation deterioration is shown in FIG.
The shape shown in (c) is used.

In FIG. 6, the correction unit is a storage unit 5 for storing the zero-phase current signal of the feeder when insulation deterioration has not occurred.
0, and a difference calculation unit 51 that calculates the difference between the zero-phase current signal of the feeder before correction and the zero-phase current signal of the feeder output from the storage unit 50 when insulation deterioration has not occurred.

In the above structure, the zero-phase current signal of the feeder in the state where insulation deterioration is not generated by the write command signal 9a is written in the storage unit 50, and then the zero-phase current signal 5f of the feeder before correction and the storage unit. The difference calculation unit 51 obtains the difference between the zero-phase current signal of the feeder and the zero-phase current signal of the feeder read out from the circuit 50, and outputs the corrected zero-phase current signal 5h.

By correcting the zero-phase current of each feeder in this way, the feeder having the insulation deterioration can be accurately specified in the arithmetic unit 19. The correction unit may be provided in the calculation unit 19, or each of the plurality of amplifiers 17 may include the correction unit.

[0052]

As described above, according to the present invention, the GPT
It is possible to diagnose the insulation deterioration of electrical equipment without using, and it is also possible to determine the insulation deterioration part for each feeder.

Furthermore, since it is less susceptible to noise and harmonics, it is possible to perform stable insulation deterioration diagnosis. Therefore, it is possible to construct an insulation deterioration diagnosing device that is inexpensive, highly reliable, and that facilitates maintenance of electrical equipment.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an insulation deterioration diagnosing device according to the present invention.

FIG. 2 is a characteristic diagram showing an example of a temporal change of zero-phase current of electric equipment.

FIG. 3 is an explanatory diagram showing a state in which the zero-phase current vector of each feeder in FIG. 1 changes depending on the presence or absence of insulation deterioration.

FIG. 4 is an explanatory diagram showing a principle that a zero-phase current is generated in each feeder in the electric equipment shown in FIG.

FIG. 5 is an explanatory diagram showing a change state of the zero-phase current when the electric equipment shown in FIG. 1 is corrected by the zero-phase current of the feeder at the time of non-insulated deterioration.

FIG. 6 is a circuit diagram showing a configuration of an embodiment of a correction unit for correcting the zero-phase current at the time of measuring each feeder by using the zero-phase current at the time of non-insulation deterioration.

[Explanation of symbols]

 1 Electrical Equipment 2 Processor 10 Power Receiver 11 Bus 12 Feeder 13 Circuit Breaker 14 Zero-Phase Current Transformer 15 Load 17 Amplifier 18 Bandpass Filter 19 Calculation Section 20 Display Section 50 Storage Section 51 Difference Calculation Section

Claims (7)

[Claims] 1. A plurality of zero-phase current transformers for individually measuring the zero-phase currents of a plurality of distribution feeders in an electric facility, and fetching a leaked zero-phase current signal output from the plurality of zero-phase current transformers, An insulation deterioration diagnosis, comprising: a processing device that specifies a distribution feeder having insulation deterioration based on the plurality of zero-phase current signals, and that determines a degree of insulation deterioration of the specified distribution feeder. apparatus. 2. The processing device comprises a plurality of amplifying means for individually amplifying each of the plurality of zero-phase current signals to a predetermined level, and a fundamental wave of a zero-phase current which is an output signal of each of the plurality of amplifying means. A plurality of band-pass filters for extracting components, and output signals of the plurality of band-pass filters are taken in. Based on the output signals of the plurality of band-pass filters, the distribution feeder having insulation deterioration is identified and the degree of insulation deterioration is identified. 2. A calculation means for judging and a display means for displaying data indicating a feeder having insulation deterioration based on a calculation output of the calculation means and a degree of insulation deterioration of the feeder.
The insulation deterioration diagnosis device according to. 3. The amplifying means stores a level of a zero-phase current signal of a feeder in a state where insulation is not deteriorated, a current zero-phase current signal, and a non-insulated deterioration time output from the storage unit. 3. The insulation deterioration diagnosing device according to claim 2, further comprising a differential amplifier that amplifies a level difference of the zero-phase current signal. 4. The calculation means has a storage unit for storing the level of the zero-phase current signal of the feeder in a state where insulation deterioration has not occurred, and the present zero-phase current signal of each feeder and the storage unit outputs the current zero-phase current signal. 3. The insulation deterioration diagnosis device according to claim 2, which has a function of calculating a difference from a zero-phase current signal in a state where insulation deterioration has not occurred. 5. The calculation means obtains an inner product of a zero-phase current vector of a distribution feeder and a zero-phase current vector of another distribution feeder, which is a reference in the electrical equipment, and insulation deterioration is caused based on the sign of the inner product. The insulation deterioration diagnostic device according to claim 3, wherein the generated distribution feeder is specified. 6. The insulation deterioration diagnosing device according to claim 2, wherein Q of the bandpass filter is 5 or more. 7. The zero-phase current transformer has a large number of turns so that a zero-phase current of about 2 milliamperes flowing on the primary side can be measured. Insulation deterioration diagnostic device.