WO2017016361A1

WO2017016361A1 - Online monitoring method for resistive leakage current of metal-oxide-varistor lightning arrester or surge protection device

Info

Publication number: WO2017016361A1
Application number: PCT/CN2016/087331
Authority: WO
Inventors: 王富元
Original assignee: 王富元
Priority date: 2015-07-29
Filing date: 2016-06-27
Publication date: 2017-02-02
Also published as: CN105137163A; CN105137163B

Abstract

An online monitoring method for a resistive leakage current of a metal-oxide-varistor lightning arrester or surge protection device (2). The method comprises: disposing a compensation capacitor and a current sensor (4); and providing, by using the compensation capacitor, to the current sensor (4) a compensation current to cancel a capacitive current component of a metal oxide varistor (1) flowing through the current sensor (4), the compensation current flowing in the reverse direction of the capacitive current component and having a magnitude error meeting a desired detection accuracy requirement. After the capacitive current component is cancelled by using the compensation current, a magnitude and changing trend of a total current flowing through the current sensor (4) can be used to determine a magnitude and changing trend of a resistive current component flowing through the metal oxide varistor (1) under action of a utility frequency voltage. An abnormal increase of the resistive current component is an important sign of degradation of the metal oxide varistor (1). By monitoring a magnitude and changing trend of a resistive current component, a magnitude and changing trend of a resistive leakage current of a metal-oxide-varistor lightning arrester or surge protection device (2) can be monitored.

Description

On-line monitoring method for resistive leakage current of metal oxide varistor type arrester or surge protector

Technical field

The invention belongs to the technical field of electronic monitoring, and particularly relates to an online monitoring method for leakage current of a metal oxide varistor type arrester or a metal oxide varistor type surge protector.

Background technique

At present, lightning arresters (MOA) consisting of metal oxide varistor (MOV, hereinafter referred to as MOV is a metal oxide varistor) are commonly used in the field of lightning protection of power lines and equipment. The equipment is protected; the surge protector (SPD) used in the field of lightning protection of electronic circuits and equipment is also composed of metal oxide varistor (known as MOV type SPD in the industry).

In practical applications, a lightning arrester (MOA) or a surge protector (SPD) is connected in parallel on the protected line. When the protected line is struck by lightning or surge voltage, the arrester or surge protector starts and the line voltage is applied. Clamping to provide overvoltage protection for the line and equipment connected to the line. However, under the influence of strong inrush current and other factors, MOV will age. The resistive leakage current of the aging MOV will increase, and the increase of the resistive leakage current will increase the temperature rise of the MOV, and the increase of the temperature rise will aggravate the aging of the MOV. This process will eventually lead to an explosion of the MOV or a thermal trip of the MOV with thermal trip protection. MOV explosions will not only protect the line and equipment, but also cause other accidents; MOV tripping will lose the protection of the line and equipment and cannot be discovered in time without real-time online monitoring measures. Once the MOV loses protection for the line and equipment, lightning strikes can cause large-scale failures in the line and equipment. In order to improve the reliability of MOV protection to prevent such failures and accidents, people have been looking for ways to detect MOVs that are degraded and are about to fail in advance. Through a large number of practice and industry recognition, the abnormal increase of leakage current resistive component (resistive leakage current) is an important indicator of MOV degradation, and based on the following principles, it is sought to monitor the MOV resistive leakage current online: arrester or surge protector The equivalent circuit of the MOV is shown in Figure 1. It is formed by the parallel connection of the plate capacitor C ₀ and the nonlinear resistor R ₀ . When the arrester or surge protector is connected to the protected power line, the power frequency is Under the action of the voltage, a full current I _a composed of the capacitive current component I _C0 and the resistive current component I _R0 flows through the metal oxide varistor, and under normal circumstances, the value of the total current I _a is small ( mA or microampere), and the resistive current component I _{R0 is} much smaller than the capacitive current component I _C0 . After the aging of the metal oxide varistor, the resistive current component I _R0 will increase abnormally by monitoring The magnitude and change trend of the resistive current component I _R0 are used to monitor the magnitude and change trend of the resistive leakage current of the metal oxide varistor type arrester or surge protector, thereby making the aging and failure of the arrester and surge protector prediction. At present, the following methods are commonly used for on-line monitoring of leakage currents of metal oxide varistor type arresters or metal oxide varistor type surge protectors (see Sichuan Electric Power Technology, 2005, Issue 3, pages 21-23). : 1. Monitor the full current method. This method directly connects the AC mA meter to the grounding end of the arrester or surge protector. Usually, it is short-circuited with a guillotine. When reading, the knives are opened and flow through the mA meter. Current can be considered as total leakage current. The main advantage of this method is that it is simple and suitable for large-scale monitoring and use in the field. It can detect the significant deterioration of the arrester or surge protector in time, but the shortcoming is that it is very insensitive to the early aging of the arrester or surge protector. 2, the third harmonic method, this method is based on the resistive component of the full current not only contains the fundamental wave, but also three, five and higher harmonics, its component is gradually reduced. The third harmonic is very sensitive to temperature changes. The change of resistive current in the early aging period is mainly caused by the rise of the third harmonic component of the resistive current. Therefore, by measuring the magnitude of the third harmonic resistive current, the total resistive current can be obtained. value. The defect of this method is that the bus voltage contains a certain proportion of harmonic voltage, and the resulting capacitive harmonic current will cause errors in the measurement results; the resistance current of the different types of arresters or surge protectors after aging is high harmonic The variation of the wave component is different. It is difficult to determine the uniformity of the arrest of the arrester or the surge protector. 3. Harmonic current compensation method, the principle of this method is to extract the capacitive current component of the system voltage compensation total leakage current to obtain the resistive current component. At present, the most widely used in China is the LCD-4 leakage current measuring instrument. Its working principle is: advance the phase of the voltage signal obtained from the secondary measurement of the voltage transformer by 90° to compensate the total leakage current of the arrester or surge protector. Capacitive part to get resistive current. However, the three-phase operation has the following problems: the three-phase arrester is installed in a straight line. Due to the phase-to-phase coupling capacitance and electromagnetic interference, the phase arresters are subjected to the phase voltage and the adjacent phase voltages. Affect the accuracy of the monitoring results; the AC volt-ampere characteristic curve of the non-linear branch of the zinc oxide valve piece (MOV) has hysteresis in different degrees in the case of voltage and current zero-crossing, which indicates that the grid voltage is a sinusoidal function. In the waveform, the peak value of the current waveform flowing through the MOV does not coincide with the peak value of the voltage waveform, and the current waveform exhibits a form of a harmonic function. The measured resistive current has a large error. When the grid voltage contains harmonic components, this method cannot be removed. Capacitive harmonic currents cause resistive harmonic current errors. 4, the fundamental wave method, this method is to use the mathematical harmonic analysis technology to separate the fundamental value of the resistive current from the total leakage current, and to judge the metal oxide varistor type arrester or surge protector Health status. When this method is used for online monitoring, the voltage transformer used as the sampling has the problem of poor angular difference and safety, and the influence of environmental factors on the site, so that the measured value of the same normal operation equipment may occur greatly under different environments. Variety.

In summary, the monitoring methods currently used and the instruments and equipment based on these methods are either complicated in structure, poor in safety, poor in anti-interference ability, or low in detection accuracy, poor in reliability of detection results, or complicated in circuit and signal processing. The method is complicated, and the on-site debugging and calibration are difficult. So far, there is no practical and effective method to solve the real-time online monitoring problem of MOV resistive leakage current.

Summary of the invention

The object of the present invention is to overcome the deficiencies of the prior art and provide a metal oxide varistor type arrester or surge The on-line monitoring method for the resistive leakage current of the protector is not only simple but also meets the required monitoring accuracy.

The basic principle of the on-line monitoring method for resistive leakage current of the metal oxide varistor type arrester or surge protector of the present invention is also based on: "In the arrester or surge protector, the equivalent circuit of the MOV is composed of the plate capacitor C ₀ and the non-linear resistor R ₀ are connected in parallel. When the arrester or surge protector is connected to the protected power frequency line, under the action of the power frequency voltage, there is a capacitive current component I _C0 and resistivity. The total current I _a composed of the current component I _R0 flows through the MOV. When the MOV appears aging, the resistive current component I _R0 flowing through the MOV will increase abnormally, by monitoring the magnitude and variation trend of the resistive current component I _R0 . To monitor the magnitude and trend of resistive leakage current of metal oxide varistor type arresters or surge protectors. Different from the prior art, the method for obtaining the MOV resistive current component I _R0 is different. The technical solution of the present invention does not consider how to extract the representative of the output signal representing the full current I _a flowing through the MOV from the output of the current sensor. The signal of the resistive current component I _R0 , but directly offsets the capacitive current component I _C0 of the MOV flowing through the current sensor by setting the compensation capacitor (the principle and connection method are shown in FIG. 2 and FIG. 3 ), that is, the compensation capacitor C ₁ Providing the current sensor with a compensation current I _C1 that is opposite to the capacitive current component of the MOV flowing through the current sensor and having the intensity error meeting the required detection accuracy to cancel the capacitive current component I _C0 flowing through the current sensor, such that The magnitude and variation trend of the total current I flowing through the current sensor can be used to determine the magnitude and variation trend of the resistive current component I _R0 flowing through the metal oxide varistor under the action of the power frequency voltage.

Based on Fig. 2, Fig. 3 and related electrical theory, it can be derived that the mode of the total current flowing through the current sensor (hereinafter referred to as "total current") I can be simplified as:

In equation (1), K _n = ω _n U _n , ω _n is the angular frequency of each waveform of the power supply, U _n is the voltage of each waveform of the power supply, and I _R0 is (including the fundamental wave and harmonics) Total resistive leakage current.

The output signal of the current sensor is:

I _output = K _CT × I ............(2)

In equation (2), K _CT is the transform coefficient of the current sensor.

In the method provided by the present invention, the compensation current I _C1 and the capacitive current component I _C0 come to the "same node" in the physical sense and cancel out in the same current sensor, so Any (fundamental and harmonic) signals are opposite in phase, and this inverse relationship does not require any circuit debugging and is independent of the harmonic content and phase of the grid. Therefore, it can be known from (1) and (2) that if C ₁ =C ₀ , the total current flowing through the current sensor I=I _R0 can be directly proportional to the MOV resistive leakage current from the output of the current sensor. I _R0 signal I _output = K _CT × I _R0 , and then the signal amplification and processing circuit to amplify and scale the I _output to obtain the exact value of the MOV resistive leakage current I _R0 ; if C ₁ ≠ C ₀ , The effect of harmonics on measurement accuracy depends on the difference between the compensation capacitor C ₁ and the plate capacitance C ₀ .

Based on the above principle, the technical solution for the on-line monitoring method of the resistive leakage current of the metal oxide varistor type arrester or the surge protector of the present invention is: setting the compensation capacitor C ₁ and a current sensor, and using the compensation capacitor C _The current sensor is provided with a compensation current I _C1 opposite to the capacitive current component I _C0 of the metal oxide varistor flowing through the current sensor, and the intensity error satisfies the required detection accuracy to cancel the capacitive current component I _C0 After the compensation current I _{C1 is used to} cancel the capacitive current component I _C0 , the magnitude and variation trend of the total current I flowing through the current sensor can be used to determine the magnitude of the resistive current component I _R0 flowing through the MOV under the action of the power frequency voltage. And a trend of change; the relative error of the capacity of the compensation capacitor C _{1 and} the capacity of the plate capacitor C ₀ is determined according to the required detection accuracy.

In the above method, the current sensor and the compensation capacitor C ₁ may be disposed inside the arrester or the surge protector, or may be disposed outside the arrester or the surge protector:

1, the current sensor and the compensation capacitor C ₁ is provided inside or connection arrester surge protector that is: a first lead connected to connected to one end of the compensation capacitor C _1, MOV first electrode, and the frequency of the line to be protected a first electrode of the surge arrester or surge protector is connected together, a third lead connected to the second electrode of the MOV passes through the current sensor, and a second lead connected to the other end of the compensation capacitor C _{1 is} opposite to the third lead The opposite direction passes through the current sensor, the third lead passes through the end of the current sensor, the end of the second lead passes through the current sensor, and the arrester or surge connected to the protected power line The second electrode of the protector is connected.

2. The current sensor and the compensation capacitor C _{1 are} disposed outside the arrester or the surge protector: one end of the compensation capacitor C ₁ passes through the first lead and the arrester or surge protector connected to the protected power line a connection electrode, a fourth lead connecting the second electrode of the arrester or the surge protector through a current sensor, a second lead connected to the other end of the compensating capacitor C ₁ with respect to the fourth wire in the opposite direction through the current The sensor, the fourth lead passes through the end of the current sensor, and the second lead passes through the end of the current sensor and is connected to the protected power line.

Series-parallel above method, when it is not selected from standard to meet the required matching capacitance _1, the compensation capacity of the capacitor C can be _{customized. 1} accuracy by compensation capacitor C C _0, C capacity press may be ₀ by a plurality of capacitors The methods are combined to meet the required detection accuracy.

The invention has the following beneficial effects:

1, since the method of the invention by providing a compensation capacitor C ₁ to provide a current sensor and the capacitive current component opposite to the direction of current flowing through the MOV sensor, the intensity of the compensation current I _C1 error satisfies the required detection accuracy required to offset the flowing The capacitive current component I _C0 of the MOV of the current sensor comes to the "same node" in the physical sense and is cancelled in the same current sensor, so the anti-interference ability is strong and the monitoring precision is high. The mechanism is: when MOV The capacitive current component I _C0 of the full current Ia and the compensation current I _C1 provided by the compensation capacitor C ₁ flow through the current sensor, and any (base and harmonic) signals contained between the two are opposite in phase. This inverse relationship does not require any circuit debugging and is independent of the harmonic content and phase of the grid. This lays the foundation for eliminating the influence of grid harmonics on the detection results. The distance between the capacitive current component I _C0 and the compensation current I _C1 transmission path and their common relative to the distance between the interference sources are negligibly small (when the current sensor and compensation capacitor C _{1 are} set in the arrester or surge protection) This is especially true for the internals of the device. Therefore, the interphase (or spatial) interference they receive can be considered to be the same; under the same matching conditions, the influence of interference on the detection results of the present invention is not only affected by the influence of the harmonics of the grid. Small and relatively deterministic, can be eliminated as an inherent error by initialization calibration, which lays the foundation for eliminating the influence of phase-to-phase (or spatial) interference on the detection results; the influence of harmonics on the monitoring accuracy mainly depends on the compensation capacitor C ₁ and The relative error of the plate capacitor C _0. In principle, if C ₁ =C ₀ , the influence of harmonics on the detection accuracy of resistive leakage current can be eliminated. However, it is neither realistic nor let C ₁ and C ₀ be equal. It is necessary, therefore, that the relative error of the capacity of the compensation capacitor C _{1 and} the capacity of the plate capacitance C ₀ is determined according to the required detection accuracy (see the embodiment).

2. Whether the current sensor and the compensation capacitor C _{1 are} set inside or outside the arrester or surge protector, the circuit structure is also very simple. When the current sensor and the compensation capacitor C _{1 are} set inside the arrester or the surge protector, It is convenient to form an integrated intelligent lightning arrester or intelligent surge protector module, so that the lightning arrester or the surge protector itself has real-time online monitoring function.

3. Since the capacitive current I _{C1 is used to} cancel the capacitive current component I _C0 , the magnitude and variation trend of the total current I flowing through the current sensor can be used to determine the resistive current component I _R0 flowing through the MOV under the action of the power frequency voltage. The size and variation trend does not require the subsequent processing techniques of complex capacitive components and resistive components for the output signal of the current sensor as in the prior art, so the signal processing method is simple, the system debugging and calibration are convenient, and the factory is pre-delivery. The calibration results are fully applicable to any complex application site.

DRAWINGS

Figure 1 is an equivalent circuit diagram of a metal oxide varistor;

2 is a schematic diagram showing a connection manner of a current sensor and a compensation capacitor disposed inside a lightning arrester or a surge protector in the online monitoring method according to the present invention;

3 is a schematic diagram showing a connection manner of a current sensor and a compensation capacitor disposed outside a lightning arrester or a surge protector in the online monitoring method according to the present invention;

4 is a schematic diagram of a detection principle and a connection diagram of an embodiment of the online monitoring method according to the present invention;

5 is a schematic diagram of a detection principle and a connection diagram of Comparative Example 1;

6 is a schematic diagram of the detection principle and connection of Comparative Example 2;

7 is a graph showing the total current I flowing through the current sensor as a function of time when the compensation capacitor is set and the relative error between the compensation capacitor and the plate capacitance is 0.7%;

8 is a graph showing a total current I flowing through the current sensor as a function of time when the compensation capacitor is set and the relative error between the compensation capacitor and the plate capacitance is 5.1%;

FIG. 9 is a graph showing the total current I flowing through the current sensor obtained with time when the compensation capacitor is not set and I _R0 =20 μA;

Fig. 10 is a graph showing the relationship of the total current I flowing through the current sensor with time when the compensation capacitance is not set and I _R0 = 0.3 μA.

In the figure, 1 - metal oxide varistor, 1-1 - the first electrode of the metal oxide varistor, 1-2 - the second electrode of the metal oxide varistor, 1-3 - the third lead, 2—arrester or surge protector, 2-1—the first electrode of the arrester or surge protector, 2-2—the second electrode of the arrester or surge protector, 2-3—fourth lead, 3-1 - First lead, 3-2 - Second lead, 4 - Current sensor.

Detailed ways

The on-line monitoring method of the resistive leakage current of the metal oxide varistor type arrester or the surge protector of the present invention and the corresponding detection effect thereof are further illustrated by two embodiments and two comparative examples with reference to the accompanying drawings. . All examples and comparative examples use the same test object, the same test conditions and the same signal processing and acquisition methods.

The object to be tested is a commercial zinc oxide varistor type surge protector (MOV type SPD). The relevant parameters given in the specification are: flow capacity 20KA, maximum continuous operating voltage U _c = 385V, plate capacitance C _{_{0 = 2370P, U 1mA = 668V}} , at 75% U _1mA (501V) DC voltage component of the resistive current I _R0 is a 1.6μA, reduction in the resistive current component and AC220V 311V peak voltage corresponding to the direct current I _R0 It is 0.3 μA.

The detection condition is: introducing a 5% third harmonic in a power frequency power supply with a rated voltage of 220V and a frequency of 50 Hz and uniformly and continuously changing the initial phase angle of the third harmonic with respect to the initial phase angle of the fundamental wave, using the power supply as the power source Detect the power supply to simulate the influence of harmonics on the detection result; set the variable resistor R _m , connect the variable resistor R _{m in} parallel with the object to be measured, and change the current I _Rm flowing through R _m by adjusting R _m to I _R = I _Rm + I _R0 to simulate the change of the resistive current component of the object to be detected; the same current sensor is used in the embodiment and the comparative example.

The signal processing and acquisition method uses a signal amplification and processing circuit composed of a peak rectification amplifying circuit and an A/D converter to convert the peak value of the output signal I _output of the current sensor into a digital signal, and then sends it to the computer for acquisition and calibration processing. The computer gives the curve of the measured result I (the total current flowing through the current sensor) as a function of time. The ordinate of the curve is I (in μA), the abscissa is time t, and the sampling time is at least greater than the initial harmonic. The time required to change the phase angle by 360 degrees with respect to the fundamental phase angle of the fundamental wave in order to fully reflect the effect of harmonic changes on the measurement results.

Example 1

The compensation capacitor C ₁ and a current sensor 4 are set, and the compensation capacitor C ₁ = 2353p is formed by parallel combination of two capacitors with measured capacitances of 2202p and 151p respectively. The relative error between the compensation capacitor C ₁ and the plate capacitor C ₀ is 0.7. %; adjusting the variable resistor R _m such that the resistive current component I _R (I _R =I _Rm +I _R0 ) of the detected object corresponding to the peak voltage of the fundamental frequency of the 220V power frequency power supply is equal to 20 μA; 4 and the compensation capacitor C _{1 is} disposed outside the surge protector, and its connection mode is as shown in FIG. 4, and one end of the compensation capacitor C ₁ passes through the first lead 3-1 and the first of the surge protectors connected to the detection power source. 2-1 electrode connected to the fourth lead electrode and the second surge protector 2-2 2-3 connected through the current sensor 4, the other end is connected to _a compensation capacitor C relative to the second lead 3-2 The fourth lead 2-3 passes through the current sensor 4 in the opposite direction, the fourth lead 2-3 passes through the end of the current sensor, and the second lead 3-2 passes through the end of the current sensor and is connected to the detection power source.

The measurement results of Embodiment 1 are shown in Fig. 7. The influence of the harmonic variation on the measurement result is not seen in Fig. 7, and the maximum relative fluctuation based on 20uA provided by the computer sample data is ±1%. The relative error of the compensation capacitor C ₁ and the plate capacitance C ₀ is 0.7%, and the influence on the measurement result is almost negligible. This fluctuation is mainly caused by circuit stability and random noise.

Example 2

The compensation capacitor C ₁ and a current sensor 4 are set, and the compensation capacitor C ₁ = 2249p is formed by parallel combination of two capacitors with measured capacitances of 2202p and 47p respectively. The relative error between the compensation capacitor C ₁ and the plate capacitor C ₀ is 5.1. %; adjusting the variable resistor R _m such that the resistive current component I _R (I _R =I _Rm +I _R0 ) of the detected object corresponding to the peak voltage of the fundamental frequency of the 220V power frequency power supply is equal to 20 μA; The sensor 4 and the compensation capacitor C _{1 are} disposed outside the surge protector, and the connection manner is as shown in FIG. 4 .

The measurement result of Embodiment 2 is shown in Fig. 8. As can be seen from Fig. 8, since the relative errors of C ₀ and C ₁ are large, the harmonic variation has an influence on the measurement result, and the 20 μA provided by the computer sampling data is The maximum relative fluctuation of the benchmark is ±8%. Although this result is far worse than that of Example 1, it is still superior to the best level that can be achieved by the prior art.

In the first embodiment, the second embodiment, when the relative error of the compensation capacitor C ₁ and the plate capacitor C ₀ is 0.5 to 6%, the resistive leakage current of the metal oxide varistor type arrester or the surge protector is online. The monitoring results are superior to the best levels that can be achieved with the prior art.

Comparative example 1

This comparison example does not set the compensation capacitor C ₁ , only one current sensor 4 is set; the variable resistor R _{m is} adjusted to make the resistive current component I _R (I _{R of the} detected object corresponding to the peak voltage of the fundamental frequency of the 220V power frequency power supply) =I _Rm +I _R0 ) is equal to 20 μA; the current sensor 4 is placed outside the surge protector, and its connection is as shown in FIG. 5.

The measurement results of Comparative Example 1 shown in Figure 9, can be seen from Figure 9, when there is no compensation capacitor C _1, the current flowing through the capacitive component of the total current I of the current sensor of the MOV I greater than analog resistive _C0 The current component I _R = 20 μA, which results in an average value of 208 μA, and the fluctuation of the measurement result caused by the continuous periodic change of the initial phase angle of 5% of the third harmonic with respect to the fundamental phase angle of the fundamental wave The range is up to 30μA, much larger than the resistive leakage current component of 20μA.

Comparative example 2

This comparison example does not set the compensation capacitor C ₁ , only one current sensor 4 is provided; the variable resistor R _m is turned off, so that the resistive current component I _{R of the} detected object is only the inherent resistive leakage current I _R0 , that is, I _R = I _R0 = 0.3 μA. The current sensor 4 is disposed outside the surge protector, and its connection manner is as shown in FIG. 6.

The measurement results of Comparative Example 2 are shown in Fig. 10. Comparing Fig. 10 and Fig. 9, it can be seen that there is almost no difference in the measurement results of I _R = 0.3 μA and I _R = 20 μA when the compensation capacitor C ₁ is not provided. The above measurement results show that the correct monitoring of the resistive current component I _R0 cannot be achieved without canceling the capacitive current component I _C0 .

Claims

On-line monitoring method for resistive leakage current of metal oxide varistor type arrester or surge protector, in the arrester or surge protector, the equivalent circuit of the metal oxide varistor is composed of the plate capacitor (C 0 ) and the non-linear resistance (R 0 ) are connected in parallel. When the arrester or surge protector is connected to the protected power frequency line, under the action of the power frequency voltage, there is a capacitive current component (I C0 ) And the total current (I a ) composed of the resistive current component (I R0 ) flows through the metal oxide varistor, and the metal oxide pressure is monitored by monitoring the magnitude and change trend of the resistive current component (I R0 ) The magnitude and trend of resistive leakage current of a varistor type arrester or surge protector are characterized by:

A compensation capacitor (C 1 ) and a current sensor (4) are provided, and the capacitive sensor (C 1 ) is used to supply the current sensor with a capacitive current component (I C0 ) of the metal oxide varistor flowing through the current sensor The compensation current (I C1 ) with the opposite direction and the intensity error satisfying the required detection accuracy is used to cancel the capacitive current component (I C0 ), and the compensation current (I C1 ) is used to cancel the capacitive current component (I C0 ). The magnitude and variation trend of the total current (I) of the overcurrent sensor can be used to determine the magnitude and variation trend of the resistive current component (I R0 ) flowing through the metal oxide varistor under the action of the power frequency voltage; The relative error between the capacity of the capacitor (C 1 ) and the capacity of the plate capacitance (C 0 ) is determined according to the required detection accuracy.
The resistive leakage current online monitoring method of the metal oxide varistor surge arrester or the surge protector as claimed in claim, wherein said current sensor (4) and a compensation capacitor (C 1) disposed waves arrester or Inside the surge protector, a first lead (3-1) connected to one end of the compensation capacitor (C 1 ), a first electrode (1-1) of the metal oxide varistor, and a protected power line are connected The first electrode (2-1) of the surge arrester or surge protector is connected together, and the third lead (1-3) connected to the second electrode (1-2) of the metal oxide varistor passes through the current sensor ( 4), and the compensation capacitor (C 1) connected to the other end of the second lead (3-2) with respect to said third lead (1-3) in the opposite direction through the current sensor (4), a third lead ( 1-3) The end of the current sensor and the second lead (3-2) passing through the current sensor are connected to the protected power frequency line of the arrester or the second electrode of the surge protector ( 2-2) Connection.
The resistive leakage current online monitoring method of the metal oxide varistor surge arrester or the surge protector as claimed in claim, wherein said current sensor (4) and a compensation capacitor (C 1) disposed waves arrester or Outside the surge protector, one end of the compensation capacitor (C 1 ) is connected to the first electrode (2-1) connected to the protected power line by the first lead (3-1), and the first electrode (2-1) of the surge protector, a second lead (3-2 arresters or surge protector second electrode (2-2) fourth lead (2-3) connected through a current sensor (4), and the compensation capacitor (C 1) connected to the other end Passing the current sensor (4) in the opposite direction with respect to the fourth lead (2-3), the fourth lead (2-3) passing through the end of the current sensor, the second lead (3-2) The ends of the overcurrent sensor are connected to the protected power line.
The method for online monitoring of resistive leakage current of a metal oxide varistor type arrester or surge protector according to any one of claims 1 to 3, wherein the compensation capacitor (C 1 ) is a custom capacitor or a plurality of A capacitor is combined in series and parallel mode.