JPH1114693A - Method and apparatus for measuring partial discharge of electric apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size by detecting a partial discharge current flowing through a ground line during operation of an electric apparatus, finding a maximum level of current corresponding to the charges of partial discharge during operation and then operating the charges of partial discharge according to a specified formula. SOLUTION: The housing 8 of an electric apparatus is grounded through an earth line 2 and the power supply line 10 for the electric apparatus is disconnected from an AC power supply line 10. A reference pulse of a predetermined correction charge is then generated by connecting a reference pulse generator 6 between the power supply 10 and the housing 8 and a maximum correction current Im0 corresponding to the correction charge q0 is determined by detecting a partial discharge current flowing through the earth line 2 on the occurrence of a partial discharge by means of a current sensor 3. Subsequently, power is supplied by connecting the power supply 10 with a power supply and a partial discharge current flowing through the earth line 2 is detected by means of the current sensor 3 during operation. Thereafter, a maximum current Im1 corresponding the partial discharge charge q1 is found during operation of the power supply and the partial discharge charge q1 is operated according to a formula; q1=(Im1/Tm0).q0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring partial discharge of electric equipment for diagnosing insulation deterioration for maintenance of electric equipment such as rotating machines and transformers in power plants, substations and various plants. Related to the device.

[0002]

2. Description of the Related Art Regarding the measurement of partial discharge of electric equipment, for example, the Institute of Electrical Engineers of Japan Standardization Committee JEC-04
01. Partial discharge is a discharge that only partially bridges the insulation between conductors.With regard to the magnitude of the partial discharge, the magnitude of the partial discharge that occurs in the electrical equipment that is the test object is expressed by the discharge charge. Represent. When a partial discharge occurs in an electric device, a small pulse-like current change occurs at the place where the partial discharge occurs, and the magnitude of the partial discharge is measured.

[0003] In a typical prior art, after stopping electrical equipment and breaking a cable serving as a power supply line, a partial discharge charge is measured using a partial discharge tester, and the degree of insulation deterioration is evaluated by a control value. . Further, in another prior art, after stopping the electric device and disconnecting the cable, a tan δ value is measured using a sharing bridge, and the degree of insulation deterioration is evaluated based on a control value.

[0004] In these prior arts, it is necessary to stop the electric equipment, and continuous operation cannot be performed. In addition, it is necessary to open a cable such as a power supply line, and after the test, it is necessary to make a connection. Further, the above-described tester is large and expensive, and requires a large amount of test work, and the test work requires specialized knowledge.

[0005] Other prior arts capable of measuring partial discharge during operation of electrical equipment are disclosed in, for example, Japanese Patent Application Laid-Open No. 4-359.
168. In this prior art, a current sensor is attached to a ground line of an electric device, a weak partial discharge current is detected, analog / digital converted, a noise signal is removed by various waveform analysis, and a partial discharge charge is obtained.

In this prior art, there is a problem that a test apparatus is complicated, expensive, heavy, and lacks in mobility. Further, in order to perform waveform analysis, specialized knowledge is required, and an analysis time is required for a long time, for example, about one hour.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to measure the partial discharge charge during the operation of electric equipment, and to reduce the size and weight of the test apparatus by simplifying its configuration. It is an object of the present invention to provide a method and an apparatus for measuring a partial discharge of an electric device, which can easily perform a test operation without requiring specialized knowledge.

[0008]

According to the present invention, (a) the housing of an electric device is grounded via a grounding line;
Disconnect the power line of electrical equipment from AC power,
(C) connecting a standard pulse generator between the power supply line and the housing of the electric device to generate a standard pulse of a predetermined calibration charge q0, and a portion flowing to the ground line when the standard pulse is generated; The discharge current is detected by a current sensor, and a calibration maximum value Im0 of the current corresponding to the calibration charge q0 is obtained. (D) A power supply line of the electric device is connected to a power source, and (e) power is supplied to the electric device. The current sensor detects the partial discharge current flowing in the ground line during the operation by supplying the partial discharge charge q1 to obtain the maximum value Im1 during the operation of the current corresponding to the partial discharge charge q1. A partial discharge measurement method for electrical equipment, wherein the discharge charge q1 is calculated by the following equation: q1 = (Im1 / Im0) · q0.

The basic idea of the present invention is that the discharge charge q1 representing the magnitude of the partial discharge generated in the electrical equipment corresponds to the maximum value Im1 of the partial discharge current flowing through the ground line of the electrical equipment for each number of discharges. Based on the inventor's new findings that

According to the present invention, in order to calibrate the partial discharge charge q1, the power supply line of the electric equipment is disconnected from the AC power supply and brought into a rest state, and the power supply line of the electric equipment and the power supply line and the electric insulator are separated. A standard pulse generator is connected between the housing and a housing which is electrically insulated to provide a standard pulse. As a result, a known charge q0 is injected between the power supply line and the housing. This charge q0
Fully covers the range of the magnitude of the discharge pulse to be measured. This charge q0 is, for example, 5,000 pC, 10,
000 pC or the like.

As described above, the electric devices include power plants, receiving substations, transformers in various plants, rotating machines, and the like. The housing is a conductor that is electrically insulated from the power supply line of those electric devices, and is generally grounded to the ground via a ground line. In a three-phase AC power supply, its neutral point is grounded, and in a single-phase AC power supply, one power supply line is grounded.

As described above, once the maximum value Im0 for calibration of the current flowing through the ground line is obtained by using the calibration charge q0 in a state where the electric device is stopped, power is supplied to the electric device during operation. A current flowing through the ground line is detected by a current sensor, a maximum value Im1 during the operation is obtained, and the measured maximum value Im1 is proportionally calculated with a calibration maximum value Im0 to obtain a partial discharge charge q1 of the electric device. be able to.

According to the experiment of the present inventor, the partial discharge charge q1 thus obtained is obtained by detecting the current flowing through the ground line with a current sensor, sampling the amplitude thereof, and measuring the amplitude. It was confirmed that the product had a high correlation with the partial discharge charge obtained by adding the products, that is, the area value calculation method, and it was confirmed that sufficient accuracy was obtained in practice.

In the present invention, the maximum value Im1 during operation is
The maximum value is selected from the maximum value Im1i for each partial discharge of the plurality of times n0.

According to the present invention, the maximum value Im1i (i = 1) of the current flowing through the ground line for each of the partial discharges n0 a plurality of times.
To n0), to select the largest one, thereby detecting the largest void or crack caused by voids and cracks of the electrical insulator interposed between the power supply line of the electric device and the housing. Can be.
For example, n0 = 10.

The electric current sensor and an electric circuit which is connected subsequently thereto and detects the maximum value Im1 have a wide band frequency characteristic, for example, 2 kHz to 100 MHz.
Hz. One partial discharge takes, for example, about 1 μs
c, and the current at the time of partial discharge flowing through the ground line is 1
This is a waveform having a period of / 10 to 1/100 μsec.

The present invention also provides a current sensor for detecting a current flowing in a ground line of an electric device, and a maximum for calibrating the output of the current sensor when a calibration charge q0 is injected into the electric device in response to the output of the current sensor. A first maximum value detecting means for detecting the value Im0;
For each time W1 shorter than μsec, the maximum value Im1i is detected over a predetermined number of times n0, and the maximum value Im1i is detected.
a second maximum value detecting means for selecting the largest one from among i; and an arithmetic means for calculating q1 = (Im1 / Im0) · q0 in response to outputs of the first and second maximum value detecting means. A partial discharge measuring device for electrical equipment, characterized in that:

Further, the present invention is characterized in that the first and second maximum value detecting means and the calculating means are realized by a portable personal computer.

According to the present invention, it is possible to provide a current sensor in connection with the ground line of the electric equipment, and to automatically measure the magnitude of the partial discharge.

[0020]

FIG. 1 shows a calibration charge q0 in a state in which the operation of an electric device 1 according to an embodiment of the present invention is stopped.
FIG. 9 is a view for explaining a procedure for obtaining a calibration maximum value Im0 of a current flowing through the ground line 2 corresponding to the calibration charge q0 when the electric charge is injected. The electric device 1 may be, for example, a rotating machine such as an induction motor or a synchronous motor, and FIG. 1 shows a simplified three-phase induction motor. The housing 8 of the electric device 1 to be diagnosed for insulation deterioration is grounded to the ground 9 via the ground line 2. A power supply line 10 as a primary input terminal of each phase of the electric device 1 is short-circuited and connected to each other.
1 (see FIG. 2 described below).

The power supply line 10 is electrically insulated from the housing 8 and thus the ground line 2 by a power supply insulator. A standard pulse generator 6 is connected between the connection point 7 of the power supply line 10 and the housing 8 and thus the ground line 2. The housing 8 is made of a conductor such as a metal. The standard pulse generator 6 generates a standard pulse having a predetermined calibration charge q0, thereby injecting a known charge q0 between the power supply line 10 and the housing 8.

The ground line 2 is provided with a current sensor 3 having a wide band frequency characteristic for detecting a current flowing through the ground line 2. The current detected by the current sensor 3 when the standard pulse is generated is equal to the ground line 2
Is a partial discharge current caused by voids or cracks existing in the electric insulator of the electric device 1 flowing through the electric device 1.

The partial discharge measuring device main body 4 is connected to the current sensor 3 via the flexible wire 12, and obtains a calibration maximum value Im0 of a current flowing through the ground line 2 corresponding to the calibration charge q0. The calibration charge q0 and the calibration maximum value Im0 are
It is stored in a memory built in the partial discharge measuring device main body 4. The partial discharge measuring device main body 4 includes an A / D converter and a peak hold amplifier. The A / D converter is
It has a function of converting an analog signal obtained by the current sensor 3 into a digital signal. In this case, the shorter the sampling time, the more accurately the peak value can be grasped. However, the sampling time of about 5 msec is sufficient. The peak hold amplifier selects the maximum value Im1i in FIG. 9, and may have a function of amplifying the input signal, and holds only the peak value. It can be realized by a personal computer or the like.

FIG. 2 shows the maximum value Im1 of the current flowing through the ground line 2 caused by the partial discharge in the electric insulator of the electric device 1 during the operation of the electric device 1, and determines the magnitude of the partial discharge of the electric device 1. FIG. 6 is a simplified diagram for describing a procedure for calculating. Power supply line 10 for electrical equipment 1
Is connected to a commercial AC power supply 11 and is operated while being supplied with electric power. In this state, the current of the partial discharge caused by voids or cracks in the electric insulator of the electric equipment 1 flowing through the ground line 2 is detected by the current sensor 3 and the partial discharge measurement device main body 4 corresponds to the partial discharge charge q1. The maximum value Im1 of the detected current is obtained, and the partial discharge charge q1 is calculated and obtained.

FIG. 3 is an electrical equivalent circuit diagram relating to a partial discharge generated inside the electric equipment 1. As shown in FIG. When a local defect G such as a void or a crack exists inside the electric insulator of the electric device 1, a partial discharge of the electric charge q occurs.
At this time, the voltage ΔV applied to the capacitance Cg of the defective portion G
Is represented by Equation 1.

[0026]

(Equation 1)

Here, ΔV is the voltage applied to the capacitance Cg of the defective portion G, Cb is the capacitance existing in series with the void existing in the electric insulator, and V is the voltage of the electric circuit of the present invention. It is.

The discharge charge Q generated at the capacitance Cg of the defect G is:

[0029]

(Equation 2)

Here, it is assumed that Cm≫Cb and Cm≫Cg.
Here, Cm indicates a capacitance other than the capacitances Cb and Cg described above.

The voltage ΔV applied to the capacitance Cb existing in series with the defective portion G and the capacitance Cg of the defective portion G has a large value when the void as the defective portion G is large. Therefore, it is understood that the discharge charge Q depends on the defect G in the electric insulator, and it is understood that the discharge charge Q is used as a measure for measuring the insulation deterioration of the electric insulator.

When an AC voltage V is applied to the equivalent circuit of FIG. 3, as V increases from zero to positive, the voltage Vg applied to the void also increases in proportion. Then, when a discharge voltage U determined by the size and shape of the void is reached, discharge occurs,
In a very short time (for example, about 0.1 μs or less), the voltage drops by ΔV, the voltage of the void becomes almost zero, and the discharge stops. Then, the next discharge occurs when the applied voltage further increases and the void voltage reaches the discharge voltage U again. Even if the applied voltage is significantly increased, since the discharge voltage U is constant, only the frequency of discharge increases, and Δ
Since there is no change in V and Cb, the discharge charge Q is a constant value.

FIG. 4 is an electrical equivalent circuit diagram for explaining the structure of the discharge charge Q described above. The discharge charge Q is represented by Cb × ΔV as described above, but the actual values of both Cb and ΔV cannot be known. Therefore, before applying the test voltage, a circuit composed of a known Co and voltage ΔV is connected in parallel between the power supply line 10 of the electric device 1 as a test object and the housing 8 as shown in FIG. The output of the circuit is q =
Expressing Co x ΔV means that the indicated value has been calibrated without knowing the value of Cm.

FIG. 5 is a flowchart for explaining a procedure for obtaining the maximum value Im0 for calibration of the current flowing through the ground line 2 when the calibration charge q0 is injected into the electric device 1. From step a1 to step a2, the standard pulse generator 6 is connected between the power supply line 10 and the ground line 2 as described above to generate a standard pulse of a predetermined calibration charge q0. In the next step a3, the current flowing through the ground line 2 is detected using the current sensor 3,
A calibration maximum value Im0 of the current corresponding to the calibration charge q0 is obtained.

FIG. 6 is a diagram showing a waveform of a partial discharge current detected by the current sensor 3 obtained when a standard pulse is generated by the standard pulse generator 6. In FIG. 6, the maximum value Im0 of the amplitude related to the reference level L1 of the partial discharge current waveform is detected and measured by the partial discharge measuring device main body 4. The procedure for obtaining the calibration maximum value Im0 corresponding to the calibration charge q0 is as described with reference to FIG.

Next, as described above with reference to FIG. 2, a procedure for obtaining the partial discharge charge q1 during operation is shown in FIG.
With reference to FIG. FIG. 7 is an electrical equivalent circuit diagram relating to partial discharge of the electric insulator during operation of the electric device 1. In FIG. 7, when a partial discharge occurs in the electrical insulator of the operating electric device 1, the partial discharge pulse current Ip is divided into a current Ip1 on the capacitance Cm side and a current Ip2 on the ground line 2. This split ratio depends on each capacitance Cm and the like.

FIG. 8 shows a waveform of the discharge pulse current Ip2 flowing through the ground line 2 during the operation of the electric equipment 1. In the partial discharge measuring device main body 4, the reference level L of the current Ip2 is
2 is detected. This maximum value Im1 is repeated a predetermined number of times n0, and a maximum value is obtained for each partial discharge.
i (i = 1 to n0).

FIG. 9 shows the maximum value Im1i of the current flowing through the ground line 2 due to partial discharge during the operation of the electric equipment 1.
6 is a flowchart for explaining the operation of the apparatus main body 4 for obtaining the partial discharge charge q1 by selecting the largest one from among them. Referring to FIG. 9, a procedure for detecting a partial discharge current flowing through ground line 2 during operation of electric device 1 and calculating partial discharge charge q1 will be described. The process proceeds from step b1 to step b2, in which the number n of times of measurement of the current flowing through the ground line 2 is initialized to zero, and the discharge current i detected by the current sensor 3 during operation in the next step b3.
Is detected, and in the next step b4, a predetermined time W1
To determine if has elapsed. The time W1 is selected as a time during which a pulse of a partial discharge current flowing through the ground line 2 continues when one partial discharge occurs in the electrical insulator of the electric device 1, for example, a value W1 of about 1 μsec or more,
For example, in this embodiment, W1 may be 5 μsec.

After the time W1 has elapsed, in the next step b5, the maximum value Im1i of the amplitude of the detected current I at the time W1 is calculated and obtained. In the next step b6, the number of partial discharge measurements n is set to 1
Only increment. Thus, in step b7,
The partial discharge current flowing through the ground line 2 is measured a total of n0 times, and the maximum value Im1i is stored in a memory obtained. In step b8, these maximum values Im
The maximum value Im1 of 1i is detected.

In step b9, calibration is performed by obtaining the partial discharge charge q1 of the electric device 1 by q1 = (Im1 / Im0) · q0 (3).

FIG. 10 shows waveforms when a partial discharge current flows through the ground line 2 due to the partial discharge of the electrical insulator occurring during the operation of the electric device 1. In steps b2 to b7 described above, the time W
The maximum values Im11 to Im1n0 of the amplitude for each discharge are obtained for each discharge. In step b8, these maximum values Im1i
The maximum value Im1 of (i = 1 to n0) is detected, and the maximum value Im1 is calibrated to obtain the partial discharge charge q1.

Here, in most cases, the noise component is weaker than the partial discharge current signal and does not cause any problem.
In rare cases, noise having an amplitude larger than the partial discharge current signal may flow. This can be solved by repeating the measurement several times.

In another embodiment of the present invention, instead of finding the maximum value Im1i over a plurality of n0 times, the maximum value Im1 of a single discharge may be found to calculate the partial discharge charge q1. .

FIG. 11 is a graph showing the experimental results of the present inventor. The horizontal axis in FIG. 11 is the area for each partial discharge obtained by summing the product of the sampling value of the amplitude and the time on one side, for example, the positive side, with respect to the reference level of the partial discharge current flowing through the ground line 2. 5 shows partial discharge charges according to an area value calculation method. The vertical axis of FIG. 11 indicates the partial discharge charge q1 obtained by calibrating the maximum value Im1 of the current flowing through the ground line 2 for each partial discharge according to the present invention described above.
Is shown.

According to the experiment of the present inventor, the phase of the partial discharge charge between the so-called area value calculation method shown on the horizontal axis of FIG. 11 and the so-called peak value calculation method of the present invention shown on the vertical axis of FIG. The relation number was 0.98, and it was confirmed that there was a very high correlation. As a result, according to the present invention, it has been found that, in practice, the partial discharge charge q1 can be measured with high accuracy without hindrance, and the state of insulation deterioration of the electric device 1 can be grasped. Further, according to such a method of the present invention, the calculation and measurement of the partial discharge charge q1 can be performed in a short time, and at the site where the electric device 1 is installed, it is possible to determine whether insulation deterioration is good or not. become able to.

FIG. 12 shows a waveform of a current flowing through the ground line 2 due to the partial discharge of the electric device 1 showing the result of the experiment performed by the present inventor. From this waveform, the time W due to one partial discharge
1 is less than about 1 μsec as described above. Therefore, it can be seen that the partial discharge occurs repeatedly at intervals of about 1 μsec or more.

[0047]

According to the first aspect of the present invention, the partial discharge current flowing through the ground line when the calibration electric charge q0 is injected into the electric equipment is detected and the calibration maximum value Im0 is detected.
Is obtained once, it is possible to constantly detect the discharge charge q0 representing the magnitude of the partial discharge generated in the electric device during the operation of the electric device and to monitor the degree of insulation deterioration of the electric device. it can. Moreover, according to the present invention,
What is necessary is just to detect the maximum values Im0 and Im1 of the output of the current sensor, thereby simplifying the configuration, making it possible to reduce the weight, exhibiting mobility, and enabling the operator to specialize. Without the need for technical knowledge,
Skill is not required, and the partial discharge charge q1 can be obtained in a very short time, so that operability is very good.

According to the second aspect of the present invention, the maximum value Im1i is selected from the maximum values Im1i of the partial discharges a plurality of times n0, and thereby, for example, voids and cracks generated in the electrical insulation of the electric equipment. The largest one can be reliably detected.

According to the third aspect of the present invention, it is possible to automatically measure the magnitude of the partial discharge of the electric equipment.

According to the fourth aspect of the present invention, the configuration can be downsized, and the monitoring of electric equipment can be easily performed using, for example, a portable personal computer called a commercially available notebook personal computer.

[Brief description of the drawings]

FIG. 1 shows a calibration maximum value Im0 of a current flowing through a ground line 2 corresponding to a calibration charge q0 when a calibration charge q0 is injected in a state where the operation of an electric device 1 according to an embodiment of the present invention is stopped. It is a figure for explaining a procedure.

FIG. 2 calculates the maximum value Im1 of the current flowing through the ground line 2 caused by the partial discharge in the electric insulator of the electric device 1 during the operation of the electric device 1, and calculates the magnitude of the partial discharge of the electric device 1. It is a simplified diagram for explaining a procedure.

FIG. 3 is an electrical equivalent circuit diagram relating to a partial discharge generated inside the electric device 1.

FIG. 4 is an electrical equivalent circuit diagram for explaining a configuration of the discharge charge Q described above.

FIG. 5 is a flowchart illustrating a procedure for obtaining a calibration maximum value Im0 of a current flowing through the ground line 2 when a calibration charge q0 is injected into the electric device 1.

FIG. 6 is a diagram showing a waveform of a partial discharge current detected by a current sensor 3 obtained when a standard pulse is generated by a standard pulse generator 6;

FIG. 7 is an electrical equivalent circuit diagram relating to partial discharge of an electrical insulator during operation of the electric device 1.

FIG. 8 is a diagram showing a waveform of a discharge pulse current Ip2 flowing to the ground line 2 during operation of the electric device 1.

FIG. 9 shows the apparatus main body 4 for selecting a maximum value of the maximum value Im1i of the current flowing through the ground line 2 due to the partial discharge during the operation of the electric device 1 and obtaining the partial discharge charge q1.
6 is a flowchart for explaining the operation according to FIG.

10 is a diagram showing a waveform when a partial discharge current flows through the ground line 2 due to partial discharge of the electrical insulator occurring during operation of the electric device 1. FIG.

FIG. 11 is a graph showing experimental results of the present inventor.

FIG. 12 is a diagram showing a waveform of a current flowing through the ground line 2 due to partial discharge of the electric device 1, showing an experimental result of the present inventor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric equipment 2 Grounding line 3 Current sensor 4 Partial discharge measuring device main body 6 Standard pulse generator 7 Connection point 8 Housing 9 Ground 10 Power supply line 11 Commercial AC power supply 12 Flexible wire

Claims (4)

[Claims] (1) grounding a housing of an electric device via a grounding line, and (b) connecting a power line of the electric device to:
(C) connecting a standard pulse generator between the power supply line and the housing of the electric device to generate a standard pulse of a predetermined calibration charge q0; A partial discharge current flowing through the ground line is detected by a current sensor, and a calibration charge q0
(D) connecting the power supply line of the electric equipment to the power supply, and (e) a part flowing to the ground line when the electric equipment is operated by supplying power thereto. The discharge current is detected by a current sensor to determine the maximum value Im1 of the current corresponding to the partial discharge charge q1 during operation. (F) The partial discharge charge q1 of the electric device is calculated by the following equation: q1 = (Im1 / Im0) · A partial discharge measurement method for electrical equipment, wherein the method is operated by using q0. 2. The method according to claim 1, wherein the maximum value Im1 during operation is selected from the maximum value Im1i for each partial discharge of a plurality of times n0. . 3. A current sensor for detecting a current flowing through a ground line of an electric device, and a calibration maximum value Im0 of an output of the current sensor when a calibration charge q0 is injected into the electric device in response to an output of the current sensor. A first maximum value detecting means for detecting, and a time W of less than about 1 μsec in response to an output of the current sensor.
The maximum value Im1i over a predetermined number of times n0 for each 1
And the second maximum value detection means for selecting the maximum value Im1 from the maximum values Im1i, and responding to the outputs of the first and second maximum value detection means, q1 = (Im1 / Im0) · q0 Calculating means for calculating the partial discharge of the electrical equipment. 4. The apparatus according to claim 3, wherein the first and second maximum value detecting means and the calculating means are realized by a portable personal computer.