JPH05159909A - Fault monitor for lightning arrestor - Google Patents

Abstract

PURPOSE:To see that the fault can be detected accurately and in hot-line condition even if the insulation of one nonlinear resistor element, which constitutes the laminate of a lightning arrestor fitted with a series gap breaks. CONSTITUTION:An impedance 21 to ground is connected to the output end of a voltage generator 23. A by-pass capacitor 20 larger in capacitance than the laminate 9 is connected to the impedance 21 to ground, this series circuit 24 is connected in parallel to both ends of the laminate 9. The output voltage from the voltage generator 23 is applied to both sides of the laminate 9 through the bypass capacitor 20, and the current flowing to the laminate 9 is detected with a current transformer 14. A comparator 25 receives the output signal of this current transformer 14, and outputs a fault signal 25S when the signal gets over the specified level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for monitoring a fault of a lightning arrester mounted on a transmission tower and installed from a transmission line through a series gap.

[0002]

2. Description of the Related Art FIG. 3 is a side view showing a structural example of a lightning arrester installed through a series gap. An insulator 2 is suspended from a power transmission tower (not shown) through a support metal fitting 1 (at a ground potential), and a power transmission line 3 is stretched at its tip. A pair of arcing horns 4 are provided at both ends of the insulator 2,
The discharge gap 5 is formed. Further, a lightning arrester 6 is installed on the support fitting 1, and another pair of arcing horns 7 are provided on the non-grounded side terminal of the lightning arrester 6 and the power transmission line 3 to form a series gap 8. The gap length between the discharge gap 5 and the series gap 8 is set so that when the overvoltage reaches the power transmission line 3, the series gap 8 discharges earlier.

The arcing horn 4 shown in FIG. 3 is for discharging the discharge gap 5 when an overvoltage such as a lightning surge enters the power transmission line 3 and absorbing the overvoltage. However, since the discharge gap 5 does not have the ability to block the follow current from the power transmission line 3, a ground fault continues and a power transmission failure occurs. To prevent this, a lightning arrester 6 is provided via a series gap 8. Overvoltage is discharge line 3
Occurs, the series gap 8 is discharged, and the discharge current flows through the lightning arrester 6. The lightning arrester 6 instantaneously discharges the discharge current (0.5 to 0.5
Since it is shut off for 1.0 cycle, the follow-up current due to a ground fault is suppressed. Recently, instead of arcing horn 4, lightning arrester 6
Are often installed with the arcing horn 7.

FIG. 4 is a sectional view showing the internal structure of the lightning arrester 6 of FIG. A laminated body 9 in which a plurality of disc-shaped nonlinear resistance elements 18 having zinc oxide as a main component are laminated is an insulating porcelain tube 10.
It is stored inside. This laminated body 9 is holding metal fittings 1 at both ends.
It is integrated with a fastening member (not shown) through 1A and 11B, and is further sandwiched between cover plates 13A and 13B of the insulating porcelain tube 10 through a compression spring 12. The support fitting 1 and the arcing horn 7 described in FIG. 3 are attached to the lid plates 13A and 13B, respectively. It is important for such a lightning arrester 6 to constantly monitor the failure of the built-in nonlinear resistance element 18, and a monitoring device for that purpose is attached to the lightning arrester 6.

FIG. 5 is a sectional view showing an example of the configuration of a conventional fault arrester for a lightning arrester, which is an example in which the device is attached to the support metal fitting 1 side. A current transformer 14 that orbits the compression spring 12 is attached to the cover plate 13A. An output lead wire 14A on the secondary side of the current transformer 14 is drawn out of the insulating porcelain tube 10 via an airtight terminal 15 and connected to the comparison section 16. The display unit 17 outputs the output signal 1 of the comparison unit 16.
It is configured to receive 6S.

In FIG. 5, a power supply lead (not shown) for conductively connecting the cover plate 13A and the press fitting 11A is arranged in the compression spring 12, and a current flowing from the laminated body 9 to the ground side cover plate 13A. Is detected by the current transformer 14 and outputs a signal 14S proportional to the current to the output lead wire 14
It is sent to the comparison unit 16 via A. The comparator 16 includes a threshold level setter 16A, and outputs the output signal 14S of the current transformer 14.
And the threshold level are compared, and when the output signal 14S exceeds the threshold level, the failure signal 16S is output. The display unit 17 is a device that displays that the lightning arrester has failed when it receives the failure signal 16S, and outputs, for example, an alarm or turns on an indicator lamp.

The non-linear resistance element 18 of the laminate 9 has a capacitive impedance during normal operation, and a current determined by its capacitance with respect to the ground voltage of the transmission line flows through the laminate 9. Non-linear resistance element 1 when overvoltage reaches
8 changes into a resistive impedance and absorbs the overvoltage. Should the non-linear resistance element 18 fail and dielectric breakdown occurs, its impedance becomes zero. As a result, the capacitance of the entire laminated body 9 becomes large, so that the current transformer 1
The value of the current flowing through 4 also increases. The comparison unit 16 outputs the failure signal 16S when the current flowing through the non-linear resistance element 18 exceeds the value of the current flowing under normal conditions.

[0008]

However, when the conventional device as described above is applied to a lightning arrester with a series gap, there is a problem that the accuracy of failure detection becomes very poor. That is, its capacitance is much smaller than that of the stack because the series gap is an air gap. As a result, the current flowing in the current transformer is substantially dependent on the capacitance of the series gap. Even if one of the nonlinear resistance elements that make up the laminated body fails, the current value increases by only about 0.5%, and the failure cannot be detected unless more than half of the nonlinear resistance elements that make up the laminated body fail. there were.

Current when one nonlinear resistance element fails
Next, we try to calculate the increment of the value. Figure 6 shows the series gap
It is an equivalent circuit diagram of the arrester including. Series gap electrostatic
Capacity is C₀, n nonlinear resistance elements 18 are connected in series.
The total capacitance of the laminated body 9 is C₁And This electrostatic
Capacity C₀, C₁From transmission line 3 to commercial angular frequency ω ₀The exchange of
Current voltage (ground voltage V₀) Is applied, then ground 1
Assuming that the current transformer 14 detects the current I flowing on the 9 side.
To do. In this case, the current I is I = ω₀・ V₀・ C₂ ──── (1) C₂= C₀・ C₁/ (C₀+ C₁) ──── (2) C₂Is the total capacitance including the series gap 8.
Is the quantity and the current I is C₂Proportional to. Also the non-linear resistance
If the capacitance of the element 18 alone is C, then there are n
So C₁= C / n --- (3)

Here, for example, assuming that C is 1,000 pF and n is 20, C ₁ is 50 pF from the equation (3). C ₀ is 5 pF
Then, by substituting these into Eq. (2), C ₂ = 5 × 50 / (5 + 50) = 4.545 (pF) ───── (4), and substituting the value of Eq. (4) into Eq. (1) The value at that time is the value of the current that flows when the nonlinear resistance element 18 is normal. Next, it is assumed that one non-linear resistance element 18 has a dielectric breakdown. In this case, since n in the equation (3) may be set to 19, C ₁ is 52.63 pF. Since C ₀ does not change, substituting these into Eq. (2), C ₂ = 5 × 52.63 / (5 + 52.63) = 4.5662 (pF) ──── (5) Eqs. (5) and (4) The ratio of C ₂ of 1. is 1.0047.
Therefore, even if one of the nonlinear resistance elements 18 fails, the current I increases by only about 0.5% compared to the normal case.
It is almost impossible to reduce the detection error of the measuring instrument to 1% or less. Therefore, in the conventional device, the failure cannot be detected unless dielectric breakdown of half or more of the nonlinear resistance elements 18 is performed. Moreover, since the voltage of the power transmission line 3 varies by several percent, it can be said that the device of FIG.

The device of FIG. 5 was originally intended for monitoring surge arrestor failures that do not go through a series gap. As described above, since the lightning arrester is arranged through the series gap, as shown in FIG.
The detection accuracy of this device has dropped extremely. The current situation is that there is no device that accurately detects a failure of a lightning arrester arranged via a series gap in a live state.

It is an object of the present invention to apply a voltage different from that of a transmission line to a lightning arrester with a series gap via a bypass capacitor, so that even if one non-linear resistance element is dielectrically broken down, the lightning arrester can be accurately operated. It is to be able to detect well.

[0013]

In order to achieve the above object, according to the present invention, a surge arrester which is composed of a laminated body of a plurality of nonlinear resistance elements and which is installed from a power transmission line through a series gap is provided. A device for monitoring, a voltage generator, a ground impedance connected in parallel to a voltage output terminal of the voltage generator, and one end of which is connected to a ground side terminal of the laminate, and a non-ground side of the ground impedance. A bypass capacitor having one end connected to a terminal of the stack and the other end connected to a terminal on the series gap side of the stack, and a current sensor for detecting and outputting a current flowing through the stack by applying a voltage from the voltage generator. And a comparison unit that outputs a failure signal when the level of the output signal of this current sensor exceeds a predetermined level, and a table that indicates that the arrester has received a failure and that receives the output signal of this comparison unit. And the capacitance of the bypass capacitor is larger than that of the laminated body, and in this configuration, the capacitance of the bypass capacitor is equal to that of the single non-linear resistance element forming the laminated body. In addition, the voltage generator generates either an AC voltage or a pulse voltage having a frequency different from the commercial frequency, and the comparison unit sets the level of the signal excluding the commercial frequency component of the output signal of the current sensor to a predetermined level. A fault signal shall be output when the level of is exceeded.

[0014]

Operation: The output terminal of the voltage generator is connected to the ground impedance, which is grounded at one end. A bypass capacitor whose capacitance is greater than that of the stack is connected in series to the ground impedance, and this series circuit is connected in parallel to both ends of the stack. The output voltage from the voltage generator is applied to both sides of the laminated body through the bypass capacitor, and the current flowing through the laminated body is detected by the current sensor. The comparator receives the output signal of the current sensor, and outputs a failure signal when the signal exceeds a predetermined level. This failure signal is received by the display unit and indicates that the lightning arrester is out of order. With this configuration, most of the output voltage of the voltage generator is applied to the laminated body. Therefore, at that time, the current flowing through the stacked body increases by about 1 / n of the normal case when one of the n nonlinear resistance elements undergoes dielectric breakdown. For example, when n is 20, a current increase of about 5% is recognized. Therefore, the failure of the arrester can be detected with sufficient accuracy.

In the above structure, the capacitance of the bypass capacitor is set equal to that of the single non-linear resistance element.
With this configuration, if the bypass capacitor should have a dielectric breakdown, the current flowing through the laminated body will increase by 1 / n of the normal case when the number of nonlinear resistance elements is n. To do. Therefore, since the non-linear resistance element is detected in the same manner as when one dielectric breakdown occurs, it is possible to detect the failure of the bypass capacitor.

Further, in the above structure, the voltage generator generates an AC voltage or a pulse voltage having a frequency different from the commercial frequency, and the comparison unit outputs the level of the signal excluding the commercial frequency component from the output signal of the current sensor. Outputs a failure signal when exceeds a predetermined level. With this configuration, even if an AC voltage component of the commercial frequency from the power transmission line is input to the current sensor through the series gap, the comparison unit does not detect the voltage component, so failure detection can be performed accurately in a live state of the power transmission line. It can be carried out.

[0017]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 is a circuit connection diagram showing the configuration of a lightning arrester failure monitoring apparatus according to an embodiment of the present invention. A laminated body 9 made up of n non-linear resistance elements 18 is connected to the power transmission line 3 via a series gap 8. The current i flowing through the laminated body 9 is detected by the current transformer 14, which is a current sensor, and the signal 14S is output. The comparator 25 compares the level of the signal of the signal 14S from which the commercial frequency component has been removed with the predetermined level set by the threshold level setting unit 25A, and fails when the level of the signal exceeds the predetermined level. The signal 25S is output.
Further, the display device 17 receives the failure signal 25S and displays that the lightning arrester is out of order. Further, FIG. 1 shows that the terminal 9A on the side of the series gap 8 and the terminal 9B on the side of the ground 19 of the laminated body 9 are connected in parallel with the bypass capacitor 20 and the ground impedance 21.
And a series circuit 24 of are connected. A voltage generator 23 for applying an AC voltage having a frequency different from the commercial frequency is connected to the ground impedance 21, and a varistor 22 is connected in parallel.

In FIG. 1, the voltage generator 23 is used to
AC power is applied to the series circuit 24 of the line capacitor 20 and the laminated body 9.
A pressure V is applied. At that time, it flows into this series circuit 24
The current transformer 14 detects and outputs the current i. Figure 2
6 is an equivalent circuit diagram of the series circuit 24. FIG. Bypass capacitor 20
The capacitance of C_C, N non-linear resistance elements 18 in series
The total capacitance of the connected laminated body 9 is C₁And This
AC voltage V of angular frequency ω is applied to the series circuit 24 of
When the current i flowing at that time is detected by the current transformer 14,
Suppose. In this case, the current i is i = ω · V · C₃ ──── (6) C₃= C_C・ C₁/ (C_C+ C₁) ──── (7) C₃Is the capacitance of the series circuit 24 and i is
C₃Proportional to. In addition, the static electricity of the nonlinear resistance element 18 alone
If the capacitance is C, then C is the same as in equation (3) above. ₁= C
/ N.

Here, for example, if C is 1,000 pF and n is 20, C ₁ will be 50 pF. C _C is 1,000 pF and C
Substituting a value greater than ₁ into equation (7) gives C ₃ = 1,000 × 50 / (1,000 + 50) = 47.619 (pF) ───── (8), and the value of equation (8) is changed to (6). This is the case where the current value when substituting into the equation is normal for the nonlinear resistance element 18. Next, it is assumed that one non-linear resistance element 18 has a dielectric breakdown. In this case, the value of n in equation (3) should be set to 19, so C ₁
Is 52.63 pF. Since C _C does not change, substituting these values into Eq. (7), C ₃ = 1,000 × 52.63 / (1,000 + 52.63) = 49.999 (pF) ──── (9) Eq. (9) and (9) The ratio of C _{3 to} the equation 8) is 1.050.
Therefore, if one of the nonlinear resistance elements 18 fails, the current i increases by 5% compared to the normal case. When the C _C is 500 pF, the nonlinear resistance element is 1
When an individual failure occurs, the current i increases by 4.8% compared to the normal case. Since the measuring instrument detects such a change in current,
For example, let C _C be 1,000 pF When the predetermined level exceeds 5% of the normal level, the comparator 25 outputs the failure signal 25S.
Will be output. Moreover, since the applied voltage does not fluctuate like the voltage of the power transmission line 3 in the conventional device, it is possible to reliably monitor the failure.

The device of FIG. 1 has improved failure detection accuracy as compared with the conventional device of FIG. 6 because the capacitance C _C of the bypass capacitor 20 is larger than that of the series gap 8. .. Since almost all the output voltage V of the voltage generator 23 is applied to the laminated body 9, even if one non-linear resistance element 18 is broken down, the current i changes greatly. Therefore, the larger the capacitance C _C of the bypass capacitor 20 with respect to the capacitance C ₁ of the laminated body 9, the greater the change in the current i. By increasing C _C by an order of magnitude with respect to C ₁ as in the above calculation example, the current i is increased by 1 / n with respect to the failure of one nonlinear resistance element 18.
When the value of n is as large as 50 to 100, the change in the current i cannot be detected. However, in the system where the transmission line is 66 to 77 kV, n is used at about 20, and in the transmission system below that voltage, the value of n is gradually reduced and used. Therefore, the application range of the present invention is very wide.

In FIG. 1, the ground impedance 21 is for preventing the terminal potential of the bypass capacitor 20 on the voltage generator 23 side from floating when the series gap is discharged by a lightning surge. The lightning surge voltage is divided by the bypass capacitor 20 and the ground impedance 21.
As a result, the overvoltage is prevented from entering the voltage generator 23. Varistor 22 has impedance to ground 21
Is connected in parallel to the voltage generator 23.
Is tightly protected.

The frequency of the voltage output from the voltage generator 23 is different from that of the transmission line voltage. The voltage frequency of both may be the same, but this device can be used even in a live state. Voltage of power line 3 and voltage generator 2
The output voltage of 3 can be separated. Since the comparison unit 25 removes the commercial frequency component and compares it with the level of the threshold level setting unit 25A, even if the current transformer 14 receives induction by the AC voltage from the power transmission line 3 to some extent, the accuracy of the failure detection is completely eliminated. It does not affect. However, the capacitance of the series gap 8 is several pF.
Generally, it is very small, so the transmission line 3 to the current transformer 14
The voltage induced component to is not so large. Voltage generator 2
It is sufficient that the voltages output from the power supply 3 have different frequencies in order to be separated from the voltage induced from the power transmission line 3. Therefore, the output voltage from the voltage generator 23 may be a pulsed voltage.

The laminate 9 and the current transformer 14 in FIG. 1 may have the same structure as the conventional device of FIG. The bypass capacitor 20 may be installed in parallel outside the insulator tube 10 of the lightning arrestor, and may be mounted separately on the transmission tower. In that case, the one in which an oil-filled capacitor or a ceramic capacitor is housed in another insulating porcelain tube is used. On the other hand, the bypass capacitor 20 may be arranged inside the insulating porcelain tube 10 of the lightning arrester and arranged in parallel with the laminated body 9. Bypass capacitor 2 inside the arrester
By storing 0, the device can be made more compact. By-pass capacitor 2 to be stored in the arrester
As 0, for example, a laminated body of ceramic capacitors or a cylindrical capacitor obtained by winding a plurality of metal foils in a cylindrical shape with an insulating film interposed therebetween is used.

As a fault arrester for a lightning arrester according to another embodiment of the present invention, a bypass capacitor 20 shown in FIG.
The electrostatic capacitance C _C of the non-linear resistance element 18 alone
Equal to. Assuming that the number of stacked layers n of the non-linear resistance element 18 is 20, C ₁ = C / 20. Therefore, when the capacitance C ₃ of the series circuit 24 is normal, C ₃ = C / 21 from the equation (7). ── It becomes (10). Here, when any of the one or bypass capacitor 20 of the non-linear resistance element 18 has a dielectric breakdown becomes _{C 3 = C / 20 ───── (} 11). The ratio of C ₃ between the equations (11) and (10) is 1.05. Therefore, not only the nonlinear resistance element 18 but also the bypass capacitor 20 can detect the failure even if the breakdown occurs.

[0025]

As described above, the present invention connects the ground impedance to the output terminal of the voltage generator. A bypass capacitor whose capacitance is greater than that of the stack is connected in series to the ground impedance, and this series circuit is connected in parallel to both ends of the stack. The output voltage from the voltage generator is applied to both sides of the laminated body through the bypass capacitor, and the current flowing through the laminated body is detected by the current sensor. The comparator receives the output signal of the current sensor, and outputs a failure signal when the signal exceeds a predetermined level. This failure signal is received by the display unit and indicates that the lightning arrester is out of order. With such a configuration, even if one non-linear resistance element forming the laminated body is dielectrically broken down, the failure of the arrester can be accurately detected.

In the above structure, the capacitance of the bypass capacitor is set equal to that of the single non-linear resistance element.
With this configuration, even if the bypass capacitor is dielectrically broken down, its failure can be detected as in the case of the non-linear resistance element, and the abnormality of the device itself can be monitored.

Further, in the above structure, the voltage generator generates an AC voltage or a pulse voltage having a frequency different from the commercial frequency, and the comparison unit determines the level of the signal excluding the commercial frequency component of the output signal of the current sensor. A fault signal is output when a predetermined level is exceeded. With this configuration, it is possible to accurately detect a failure of the lightning arrester even when the power transmission line is in a live state.

[Brief description of drawings]

FIG. 1 is a circuit connection diagram showing a configuration of a lightning arrester failure monitoring device according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of the series circuit of FIG.

FIG. 3 is a side view showing a configuration example of a lightning arrester installed via a series gap.

4 is a cross-sectional view showing the internal configuration of the lightning arrester of FIG.

FIG. 5 is a cross-sectional view showing a configuration of a conventional arrester failure monitoring device.

FIG. 6 is an equivalent circuit diagram of the arrester including a series gap.

[Explanation of symbols]

 3 Transmission line 8 Series gap 9 Laminated body 18 Non-linear resistance element 20 Bypass capacitor 21 Ground impedance 22 Varistor 23 Voltage generator 19 Grounding 14 Current transformer 25 Comparison section 25A Threshold level setter 17 Display section 24 Series circuit

Claims (3)

[Claims] 1. A device comprising a laminated body of a plurality of nonlinear resistance elements for monitoring a fault of a lightning arrester installed from a transmission line through a series gap, the voltage generator and the voltage of the voltage generator. A ground impedance in which one end is connected in parallel to the output end and one end is connected to the ground side terminal of the laminate,
A bypass capacitor having one end connected to the non-grounded side terminal of the ground impedance and the other end connected to a terminal on the series gap side of the laminated body, and a current flowing through the laminated body due to voltage application of the voltage generator. A current sensor that detects and outputs, a comparator that outputs a failure signal when the level of the output signal of this current sensor exceeds a predetermined level, and a surge arrester that receives the output signal of this comparator and has failed. And a display unit for displaying, wherein the electrostatic capacitance of the bypass capacitor is larger than that of the laminated body. 2. The fault arrester for a lightning arrester according to claim 1, wherein the capacitance of the bypass capacitor is equal to that of a single non-linear resistance element forming the laminated body. 3. The voltage generator according to claim 1 or 2, wherein the voltage generator generates either an AC voltage or a pulse voltage having a frequency different from the commercial frequency, and the comparison unit commercializes the output signal of the current sensor. A fault monitoring device for a lightning arrester, which outputs a fault signal when the level of a signal excluding frequency components exceeds a predetermined level.