JPH087250B2 - Insulation deterioration monitoring device for electrical equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting insulation deterioration of electric equipment, and more particularly to a device for monitoring insulation deterioration of electric equipment for specifying a defective insulation line or a defective insulation electric equipment of a power transmission path. Regarding

[Conventional technology]

In general, a local insulation failure may occur in a power cable or a power device connected thereto due to various factors.

The causes of such insulation failure include mechanical external force, chemical change of insulating material, so-called water tree, electrical tree, etc., but 80% of serious accidents are caused by such insulation deterioration. Therefore, various insulation inspection methods have been conventionally proposed.

Here, a water tree is a type of insulation deterioration, which occurs with water in an electric field and spreads like a tree branch. The electrical tree is also a type of insulation deterioration that occurs in a partially high electric field inside the cable insulation or at the boundary between the semiconductor layer and the insulation. The deterioration then spreads like a tree branch.

As an example of the insulation inspection method, there is a method in which the power transmission system is periodically put into a power failure state. First, in the method of inspecting by applying a DC voltage to the line, the first is the measurement of partial discharge, the second is the dielectric relaxation phenomenon due to residual voltage / discharge current / residual charge, and the third is the insulation performance due to potential decay / leakage current. And the like.

On the other hand, in the method of inspecting by applying an AC voltage to the line, the first is measurement of partial discharge, and the second is measurement of dielectric relaxation phenomenon due to dielectric loss tangent.

In addition to this, as a method of inspecting the power cable in a live state, there is a method of measuring an insulation resistance or a direct current component using a portable or fixed measuring device.

[Problems to be Solved by the Invention]

However, among the above-mentioned conventional detection methods, in the method in which the power transmission system is periodically put into a power failure state, it takes time because each line has to be measured sequentially, and the measurement is performed by one power failure. There are also restrictions on what you can do. Therefore, even if the insulation state deteriorates with time, there is a problem that the tendency cannot be known and preventive measures cannot be taken.

On the other hand, in the method of inspecting the insulation resistance of a power cable in a live state using a portable measuring instrument, it is necessary to insulate the neutral point of the system grounding instrument transformer from the ground in terms of direct current for measurement. Of course, there is a problem that it requires skill for measurement because it is difficult to secure the safety, not to mention that manpower is required for preparatory work and measurement, and the insulation state cannot be constantly monitored by this method.

In addition, the method of inspecting the DC component current of a power cable in a live state using a fixed measuring device requires an operation to insulate the ground point of the cable shield from the ground in terms of DC for measurement, and is applicable to constant monitoring. Can not.

In the method of inspecting with these live wires, the target of insulation deterioration detection is limited to the high-voltage cable, and local defects such as void discharge in the insulator cannot be detected.

The present invention has been made in view of the above matters, and it is a technical problem to provide an insulation deterioration monitoring device for electric equipment, which can constantly monitor the insulation state of a power device or a power cable in a live line state. And

[Means for solving the problem]

In order to solve the above technical problems, the present invention has the following configuration in a transmission system having one or more power transmission paths.

That is, when the insulation state of the power transmission path deteriorates, a first sensor (S) that detects a traveling wave generated due to a partial discharge that occurs at that part, and a generation phase of the signal wave are detected at the same time as the external sensor. A second sensor (SR) for detecting noise, a third sensor (SF or SG) for detecting a reference signal for determining the traveling direction of the traveling wave, the first sensor (S), the second sensor (SR) ) And the third
And a measuring unit (3) for processing signals from the sensors (SF, SG), the measuring unit (3) including signals from the first sensor (S) and the third sensor (SF, SG). By comparing the phases, the traveling wave generated when the insulation of the power cable (L) or electrical equipment is deteriorated is detected to determine whether the insulation is deteriorated, and this is an external noise based on the signal from the second sensor (SR). And whether it is insulation deterioration,
In the case of insulation deterioration, the deterioration phase of the electric equipment was constructed by detecting the deterioration phase.

Here, more specifically, the power cable (L)
Of each capacitor (CT
Alternatively, C) is provided, the first sensor (S) detects the power cable (L) that constitutes the power transmission path, and the second sensor (SR) includes the capacitors (CT, C) of the respective phases. ) And the ground are connected to each electric wire to be detected, and the third sensor (SF, SG) is preferably an electric wire connecting all the capacitors (CT, C) to the ground. .

As the first sensor (S), a detection winding is wound around an annular core, and a power cable (L) forming a power transmission path is penetrated through the annular core so that the power cable (L) is so-called. It can be a primary winding, and the second sensor (SR) also has a detection winding wound around an annular core, and each electric wire that connects the capacitor (CT, C) of each phase to the ground. Each electric wire can be passed through the annular core to form a so-called primary winding, and the third sensor (SF, SG) also has a detection winding wound around the annular core, and all the capacitors (CT). , C) can be passed through the annular core to form a so-called primary winding.

Further, in the measuring unit (3), the second sensor (S
If it is determined that this is external noise based on the signal from R), it is possible not to perform the insulation deterioration determination process based on the traveling wave, or cancel it even if the insulation deterioration determination is made. can do.

Further, the first sensor (S), the second sensor (SR) and the third sensor (SF, SG) have a substantially linear BH characteristic in which the magnetomotive force and the magnetic flux density have a substantially proportional relationship, and from the low frequency range. The detection winding is preferably wound around an annular core (K) whose magnetic permeability is substantially constant up to a high frequency range. This core (K)
Is preferably formed of an amorphous metal, particularly an amorphous metal containing cobalt as a main component. Of course, the present invention is not limited to this example, and a core made of a silicon steel plate having a high magnetic permeability linear hysteresis characteristic or a magnetic material such as permalloy or ferrite can be applied.

Further, the core (K) may be formed in an annular shape by combining cut cores divided into two. The first sensor (S) thus produced can be attached to the live cable.

Further, the first sensor (S) can be made to have a function of a zero-phase current transformer that detects a ground fault current of a commercial frequency.

Then, the first sensor (S), the second sensor (SR),
And the third sensor (SF, SG) is formed by winding a first winding (M1) and a second winding (M2) whose both ends are short-circuited,
The winding (M2) of can be used as the detection winding.

In addition, the first sensor (S), the second sensor (SR) and the third sensor
The sensor (SF, SG) does not have the first winding (M1)
It is also possible to connect the impedance Z to the winding (M2) of (1) to form a detection winding.

The capacitor (CT, C) can be made of dielectric ceramic, for example, in the shape of an insulator. Specifically, a plurality of capacitor elements made of the dielectric ceramic are connected in series and made of epoxy resin in the shape of an insulator. can do. If the capacitor (CT, C) is molded into an insulator shape and has mechanical and electrical strength, it can also serve as a support insulator for busbars and other electric wires.

As another form, the capacitor (CT, C) is housed in an insulating cylinder such as plastic, provided with a high-voltage side contactor, and an earth wire on the earth side to form a live bus. Can be connected.

The composition of the dielectric ceramics of the capacitor (CT, C) can be SrTiO ₃ , MgTiO ₃ , or BaTiO ₃ .

[Action]

When an insulation defect occurs in the power transmission path, a partial discharge occurs at that portion.

Then, a traveling wave is generated due to this discharge, and travels in both directions from the defective portion on the line. Therefore, by detecting the direction of this traveling wave, it is possible to identify the transmission path whose insulation performance has deteriorated.

Then, as a method of detecting the direction of the signal wave, the phase of the traveling direction of the traveling wave at the reference point provided on the common bus and the traveling direction of the traveling wave in each power transmission path extracted from the common bus are compared. It is then possible to characterize defective systems and equipment.

Further, by paying attention to the fact that the current characteristics in each phase are different between the case of external noise (common mode noise) and the case of insulation deterioration, the insulation deterioration determination can be performed more reliably.

That is, an example of the operation will be described with reference to FIGS. 1 and 2, first, a traveling wave current generated due to insulation deterioration at the point P passes through all the first sensors (S). In FIG. 1, the cables having the parallel relationship are provided with the first sensors in the same polarity direction, respectively, and the third sensor having the polarity between the capacitor connected to the common bus connected to each cable and the ground. And the traveling wave current passes through all the sensors. Then, the direction (phase) of the traveling wave current generated by the cable deterioration is detected based on the polarity of the third sensor, and the first sensor having a detection result different from this detection result based on the detection result of this third sensor. Identifies the cable of as a deteriorated cable.

That is, the traveling wave current passing through the third sensor (SF) provided on the ground line connecting the ground side of the capacitors (C, CT) provided on the first common bus (LF) to the ground has the insulation deterioration point P at the first level. Even if it is in the cable (L1) as shown in the figure, and also if there is an insulation deterioration point (not shown) in the cable (L2, L3 ...), it is shown by dots (.) In the third sensor (SF). Sensor polarity (+) from sensor polarity (-)
Since it passes toward the side, the third sensor has the same polarity regardless of the traveling wave current caused by the insulation deterioration of any of the cables (L1, L2, L3 ...).

On the other hand, in the case of the first sensor (S), the traveling wave current caused by the insulation deterioration at the point P of the cable (L1) shown in FIG. It passes from the (−) side, which is the polarity of the sensor shown by the dot (·), toward the (+) side. In this case, the cable (L
In the first sensor (S2, S3 ...) Of 2, L3, ..., The traveling wave current passes from the polarity (+) to (-) of the sensor. Therefore, the detection signal of the first sensor (S1) of the cable (L1) where the insulation deterioration point P exists and the first sensor (S2) of the cable (L2, L3, ...) Where the insulation deterioration point P does not exist.
2, S3, ...) The detection signals have opposite phases.

Therefore, based on the detection signal of the third sensor (SF), the sensor (S
Only 1) will detect a traveling wave of opposite polarity.

Similarly, the traveling wave current passing through the third sensor (SG) located between the ground (GND) side of the capacitor (C) provided on the second common bus (LG) has the insulation deterioration point P as shown in FIG. Even if it is in the cable (L1) as shown in Fig.2, or if there is an insulation deterioration point (not shown) in the cable (L4, L5), the polarity of the sensor indicated by the dot (・) in the third sensor (SG) Since it passes from a certain (+) side toward the sensor polarity (-) side, the third sensor (SG) has the same polarity regardless of the traveling wave current due to insulation deterioration of any cable (L1, L4, L5). Becomes On the other hand, in the case of the first sensor (S), the traveling wave current caused by the insulation deterioration at the point P of the cable (L1) shown in FIG. The first sensor (S4) passes through from the (-) side, which is the polarity of the sensor indicated by the dot (•), toward the (+) side. In this case, the first of the cables (L4, L5)
In the sensors (S5, S6), the traveling wave current passes from the sensor polarity (+) to (-). Therefore, the detection signal of the first sensor (S4) at the power transmission end of the cable (L1) having the insulation deterioration point P and the first sensor (S5, S6) of the cable (L4, L5) having no insulation deterioration point P The detection signals have opposite phases.

Therefore, based on the detection signal of the third sensor (SG), only the first sensor (S4) at the power transmission end of the cable (L1) in which the insulation deterioration has occurred detects the traveling wave of the reverse polarity. Becomes

Therefore, the insulation deterioration cable (L1) can be determined. An example of detection in this case is shown in FIG. In FIG. 6, J is the waveform of the first sensor (S), Q is the waveform of the third sensor (SF), and the incoming traveling wave has a negative polarity.

Further, as an example, as shown in FIG. 2, three second sensors SR having the electric wire {LF (R, S, T)} connecting the capacitor (CT) and the ground as the primary winding are arranged in parallel. By comparing the phases of the currents passing through each wire, it is possible to easily determine whether a signal above a certain level is a common mode noise or an insulation deterioration signal, and also detect the insulation deterioration phase. It will be easy.

Therefore, by measuring the signals detected by the first, second, and third sensors by the measuring unit 3, it is possible to reliably detect the defective insulation portion.

As for the action of each sensor, as shown in FIG. 3 (A), a low-frequency current and a high-frequency current are present in the cable (L), which is the signal line to be detected and is wound around the annular core K of each sensor. It is flowing, and as a result, a magnetomotive force is generated in the core K.

The first winding (M1) and the second winding (M2) are cables L
Since it acts as a secondary coil for the (primary coil), an electromotive force is generated in the first winding (M1) according to this magnetomotive force. However, since both ends are short-circuited, the annular core K
A current flows that cancels the change in magnetic flux inside. Here, the annular core (K) has a high magnetic permeability, the magnetic permeability is substantially constant from the low frequency region to the high frequency region, both the remanence and the coercive force are small, and the magnetomotive force and the magnetic flux density are approximately proportional. If it has a substantially linear BH characteristic with, the inductive reactance of the first winding (M1) is small for low frequencies and large for high frequencies.

Therefore, the low frequency components are almost canceled out and the second winding (M
High frequency components are obtained from 2).

Actually, as shown in FIG. 3 (B), the detected line (L) need only be inserted into the core (K).

As another configuration example, if the impedance (Z) is connected to the second winding (M2) and the frequency characteristic of the impedance (Z) is properly selected as shown in FIG. The winding (M1) can be omitted.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS.

In the figure, 1 is a substation, 2 is an electricity demand place, 3 is a measuring section, S (S1, S2, S3, S4, S5, S6, S21, S22, S23, S32, S33)
Is the first sensor, SR is the second sensor, SF and SG are the third sensor, M
1 is the first winding, M2 is the second winding, K is the core, C and CT are capacitors, P is the insulation deterioration point, and L (L1, L2, L3, L4, L5, L21, L
22, L23, L32, L33) is a cable, T1, T2, T3 is a transformer, M is an electric motor, B1, B2, B3, B4, B5, B6, B7, B21, B31, B32, B33 are circuit breakers. .

In FIG. 12, 240 is an input circuit, 241 is a trigger level setting device, 242 is a filter circuit, 245 is a pulse output circuit, 246 is a counter circuit, 247 is an insulation deterioration determination output circuit,
248 is a time setting circuit.

In FIG. 13, 140 and 150 are input circuits, 141 and 151 are trigger level setting devices, 143 and 153 are filter circuits, and 145 and 155.
Is a pulse output circuit, 146 and 156 are counter circuits, 147 and 157 are insulation deterioration determination output circuits, and 148 and 158 are timed settling circuits.

First, the applicant has confirmed that when insulation failure occurs in the power transmission path, partial discharge occurs in the portion, and a traveling wave is generated in the transmission path due to these discharges.

An apparatus for detecting a defective insulation portion in the power transmission path based on this traveling wave will be described below.

In FIG. 1, an AC power source A first supplies electric power to a substation 1, and in this substation 1, a transformer T1 and a circuit breaker B1 are connected to a transmission line.
To form a first common bus LF, and the first common bus LF is grounded (GND) via a capacitor C.

A ring-shaped third sensor SF is mounted so as to surround the line between the capacitor C and the ground portion, and an output signal from the third sensor SF becomes a signal at a reference point provided on the common bus. .

A cable L1 and a cable L for power transmission are respectively connected to the first common bus LF via a circuit breaker B2, a circuit breaker B3, a circuit breaker B4, and a circuit breaker B21.
2, cable L3, cable L21, L22, L23 are connected,
These cables have an annular first sensor S1, S2, S3, S21, S2
2, S23 is mounted so as to surround the cable.

The cable L1 is extended to the electricity demand place 2.

The output signals of the first sensors S1, S2, S3 and the output signal of the third sensor SF are input to the measuring unit 3 in the insulation deterioration state.

At the electricity demand place 2, the first sensor S4 is attached to the cable L1 and is connected to the second common bus LG via the circuit breaker B5.

The second common bus LG is grounded via a capacitor C (GN
D) has been. An annular third sensor SG is attached to the line between the capacitor C and the ground portion so as to surround the line, and an output signal from the third sensor SG is a signal at the reference point of the second common bus LG. Becomes

A cable L4 and a cable L5 for power transmission are connected to the second common bus LG via a circuit breaker B6 and a circuit breaker B7, and the first sensor S5, S6 having an annular shape surrounds these cables. It is installed in each.

The cable L4 is connected to the electric motor M, and the cable L5 is connected to the transformer T2.

The output signals of the first sensors S4, S5, S6 and the output signal of the third sensor SG are input to the insulation measuring unit 3 installed in the demand place 2.

The traveling wave current resulting from the partial discharge from the fault point P is detected by the configuration of the first sensor S1, the third sensor SF, and the measuring unit 3 at the substation 1, and the first sensor S4,
It is detected by the configuration of the third sensor SG and the measuring unit 3.

Therefore, it is possible to know that the fault point P exists in the cable L1 by detecting the traveling wave current resulting from the partial discharge from the fault point P in FIG.

Further, when the failure point P is in the electric motor M installed in the demand place 2, it is detected by the configuration of the first sensor (S5), the third sensor (SG), and the measuring unit 3.

Similarly, when the failure point P is in the transformer T2, the first sensor S6
And the third sensor SG and the measuring unit 3 are used for detection.

Therefore, it is possible to detect the insulation deterioration of not only the cable but also the electric device.

Next, the operation principle of the first sensor S and the operation principle of the circuit will be described.

As shown in FIG. 5, the first sensor S has a substantially constant magnetic permeability from a low frequency to a high frequency, has small remanence and coercive force as shown in FIG. 4, and has a linear BH characteristic. A coil is wound around a core K formed of a cobalt-based amorphous metal such that This coil has a first winding M1 wound short-circuited to the core K and a second winding M2 whose both ends are open, as shown in FIG.
It consists of The core K has a width of 10 mm, an inner diameter of 150 mm,
It is formed to have a height of 5 mm, and the first winding M1 has three turns and the second winding M2 has ten turns.

With such a configuration, it is possible to discriminate between the frequency of the power source, the low-frequency current that is a harmonic thereof, and the traveling-wave current that accompanies the partial discharge.

The first sensor S of the above-mentioned configuration example, which is manufactured by using the cobalt-based amorphous alloy for the core K of the first sensor S, is 2.5
Core K does not cause magnetic saturation even with amperes of commercial frequency current.

Next, FIG. 2 shows an example implemented in a line that transmits a three-phase alternating current, and the description will be made of identifying a line whose insulation state has deteriorated.

Here, the traveling velocity V of the traveling wave is V = [(permeability × dielectric constant) ^1/2 ] ^-1 .

Here, when partial discharge occurs in the insulator of the polyethylene cable, the transmission path of the traveling wave becomes the conductor of the cable and the shield of the cable, and the dielectric constant of the polyethylene insulator is about 4 times that of air, so the transmission path Since the propagation velocity at is about 1/2 of the speed of light, V is about 150 m / μs. Further, when a partial discharge is generated from the device, the transmission path of the traveling wave becomes the conductor of the cable and the ground, so that the propagation speed in this case is close to the speed of light.

In this way, the traveling wave passes through the core at high speed, so that a sharp pulse magnetomotive force is generated. In the core K of the sensor, a magnetomotive force is generated by the zero-phase current iE of the low-frequency current, which is the frequency of the power supply and its harmonics, and the traveling wave current ip associated with the partial discharge described above. The inductive reactance is small for low frequencies and large for pulses. Therefore, although the magnetic flux change due to the magnetomotive force of the low-frequency current iE can be almost completely canceled, the magnetic flux change due to the magnetomotive force of the pulse current due to the passage of the traveling wave current ip remains without being canceled.

Therefore, only the signal accompanying the passage of the traveling-wave current can be obtained from both terminals of the second winding M2. The voltage detection signal in this case is obtained by the effect of the short-circuit winding M1 of the first sensor S, for example, in the form of alternating damping vibration as shown in FIGS. 7, 8 and 9.

FIG. 7 shows an example in which the traveling wave current resulting from the partial discharge generated in the insulator of the cable is detected by the first sensor S, and in this case, harmonics are not included. FIG. 8 shows an example in which a traveling wave current caused by a partial discharge generated from an insulator of a winding of a motor is detected by a first sensor S provided on a cable,
In this case, the wave front of the detected waveform contains large harmonics.

As described above, when the partial discharge is generated from the device, the propagation path of the traveling wave is the conductor of the cable and the ground, so that the surge impedance is large and the propagation speed of the traveling wave is also large. Therefore, the wave front portion often contains harmonics.

Therefore, by observing the waveform detected by the first sensor S, it is possible to estimate whether the deteriorated portion is a cable or an electric device such as an electric motor.

Further, of the second sensor SR for insulation deterioration phase determination inserted in each phase of the capacitor CT installed on the bus LF in FIG. 2, the sensor having the largest traveling wave current (detection signal level when present) is the largest. It is possible to identify a certain phase as a deterioration phase. In addition, the third sensor placed on the common line of the capacitor CT
No matter which phase of SF is deteriorated or which part of the system is deteriorated, the traveling wave current passes in the same direction, which makes it possible to obtain a reference signal in the direction of the traveling wave. .

In a real system, a high frequency common mode noise current in may flow through the first sensor S and the second sensor SR provided in each phase as shown in FIG. The current in passes through the second sensor SR of each phase provided in each phase of the bus with the same phase, while the traveling wave current ip caused by partial discharge due to deterioration of the insulation state of the system is first isolated. It passes through the second sensor SR in the deterioration phase, passes through the third sensor (SF) with a part of the same polarity, and reaches the ground. Further, due to the effect of the wave impedance of the third sensor (SF) and the ground (GND), the insulation deteriorates through the capacitor C and the second sensor (SR) of the phase in which the insulation is not deteriorated, passing through in the opposite polarity. Not to the bus (LF). That is, the signal wave current ip caused by the partial discharge is distinguished by passing through the second sensor SR of each phase in different phases. Therefore, the influence of the noise current in can be prevented.

In the circuit shown in FIG. 2, an experimental result of detecting a traveling wave caused by partial discharge due to deterioration of the cable insulator will be described with reference to FIG. In the graph, J is the signal characteristic line of the first sensor S provided on the cable, and Q is the signal characteristic line of the third sensor (SF, SG) provided on the bus bar. If there is a defect in the cable, the traveling wave travels in both directions as shown by point P in Fig. 1, but as shown in Fig. 1, the first sensor (S1, S
Since the traveling wave currents pass in opposite directions with respect to the polarity of 4) and the polarity of the third sensor (SF, SG), the phases of J and Q are substantially opposite to each other. Note that FIG. 6 shows the case of a traveling wave current of negative polarity. This reveals the presence of a traveling wave, that is, a defect in the cable.

Next, the operation of the insulation measuring unit 3 shown in FIG. 2 will be described. 1st sensor S, 2nd sensor SR of each phase, 3rd sensor S
The signals from the F detection coils are input to the measuring unit 3 in an insulated state.

In the measurement unit 3, the detection signals of the first sensor S and the third sensor SF are input to the input circuit 40, and the signals exceeding the set value by the trigger level setter 41 are input to the bandpass filter circuits 42 and 43.
Only the frequency band is applied to the phase comparison circuit 44 to be detected through.

The phase comparison circuit 44 compares the phase shift between the signal from the first sensor (S) of the cable and the signal from the third sensor (SF) of the common bus, and when the phase shift is approximately 180 °, the first sensor For the progress from the cable provided with, the signal is input to the pulsed output circuit 45 by regarding ip as an insulation deterioration signal, while the detection signal from the second sensor SR of each phase is input circuit.
A signal that is input to 50 and exceeds the value set by the trigger level setter 51 is input to the common mode noise detection circuit 52, and the common mode noise detection circuit 52 determines the magnitude and phase of the signal from the second sensor SR of each phase. In the case of a signal based on the detected common mode noise current in, that is, the signals of the three second sensors (SR) have the same phase and the signal levels have substantially the same value, the pulse is output through the output lock circuit 57. The output of the digitized output circuit 45 is not output. Therefore, the insulation deterioration determination based on the traveling wave is not performed.

Further, among the signals of the three second sensors (SR), the signal level of one second sensor (SR) is higher than the signal levels of the other two second sensors (SR), and the phase is approximately 180 ° ( 1
In the case of 80 ° ± 10 °), preferably 180 °, the common mode noise detection circuit 52 determines that the signal is insulation deterioration due to partial discharge, and the insulation deterioration phase detection circuit 53 detects the insulation deterioration phase.

The output of the pulsed output circuit 45 is input to the counting circuit 46.

When the counting circuit 46 obtains a count value that exceeds the set value within the repeated settling time of the timed settling circuit 48, it gives a signal to the insulation deterioration determination output circuit 47, and displays the judgment result on the insulation deterioration determination output circuit 47 and externally. Output.

On the other hand, the output of the pulsed output circuit 45 and the output of the insulation deterioration phase detection circuit 53 are input to the AND gate 54, and the output of the AND gate 54 is input to the counting circuit 55.

If the count value of the counting circuit 55 exceeds the set value within the repeated set time of the time settling circuit 48, the counting circuit 55 gives a signal to the insulation deterioration phase determination output circuit 56, and the insulation deterioration phase determination output circuit 56 judges the result. Is displayed and output to the outside.

To summarize the above, the phase of the signal of the first sensor (S) and the phase of the signal of the third sensor (SF) are approximately 180 °, preferably 1
When the signal level of one second sensor (SR) of the three second sensors (SR) is 80 ° and the insulation level is deteriorated by the operation of the measuring unit 3, the insulation is separated from the power transmission system. Deteriorated phases can be determined.

In addition, when the phase of the signal of the first sensor (S) and the phase of the signal of the third sensor (SF) are substantially the same, or 3
When the signal levels of the two second sensors (SR) are the same and the phases are the same, it can be determined by the operation of the measurement unit 3 that the power transmission system is not insulation deterioration but noise.

Next, an example of the actual measurement waveform of FIG. 9 will be described.
It is possible to observe the pulse accompanying the partial discharge as it is, but since it occurs in an extremely short time, it may be difficult to capture it. Therefore, a pulse can be easily captured by inserting a resonance circuit in the pulse detection circuit. FIG. 9 shows a waveform when such a circuit is used, and J1 is a pulse accompanying partial discharge, and this pulse excites the resonance circuit and then exhibits an attenuation waveform J2 of a specific frequency.

The size and shape and the material of the core K are not limited to those in the above-mentioned embodiment, and can be changed appropriately according to the detection conditions.

Next, a tenth example of manufacturing a capacitor CT used in the present invention
Shown in Figures and 11. The capacitance of the capacitor in Fig. 10 is
The capacitor of 500pF and Fig. 11 has the electrostatic capacity of 1,000pF. Fig. 11 is manufactured so that it can also be used as a support insulator for a bus bar, so the installation space can be saved. In each case, a plurality of capacitor elements Fd composed of dielectric ceramics were connected in series and molded into an insulator shape having a fringe (Fd) with an epoxy resin.

Since the capacitor CT used in the present invention is permanently installed in an actual system in addition to high traveling wave passage performance and high partial discharge inception voltage for the original purpose, high withstand voltage characteristics, high electrical insulation performance, High electrical and mechanical reliability such as long life is required.

As a result of various trial manufactures and confirmations, dielectric ceramics are preferable as the capacitor element, and among them, those having a dielectric ceramic composition of SrTiO ₃ or MgTiO ₃ or BaTiO ₃ are suitable in terms of traveling wave passing performance and high withstand voltage characteristics. There was found. Therefore, it is preferable to use these dielectric ceramics in the present invention.

In addition, a series of multiple capacitor elements connected in series and molded into an insulator with epoxy resin showed a high partial discharge inception voltage, high withstand voltage, and high electrical insulation performance. It turned out to be suitable from the aspect.
Therefore, in the present invention, it is preferable to use a plurality of such capacitor elements connected in series and molded in an insulator shape with an epoxy resin.

Next, FIG. 12 to FIG. 15 show another application embodiment of the present invention.

FIG. 12 shows an application example of the insulation deterioration monitoring device when there is no noise in the system. In this case, since it is not necessary to install a capacitor on the common bus bar, the structure can be simple and inexpensive.

Fig. 13 shows an application example for detecting the occurrence of a ground fault in the system, in addition to the constant monitoring of insulation deterioration of the system, in which the first sensor S replaces the conventional zero-phase current transformer. Since there is no need to install a phase current transformer and a ground fault relay, the equipment cost is low and the installation space can be saved.

 FIG. 14 shows a portable type.

The first sensor S is made of a split core and is attachable to and detachable from the power cable L.

Also, three electric wires 3 each having a terminal 312 detachably connected to each phase of the busbar to which the power cable (L) is connected.
11 is provided, and the fuse F and the capacitor CT are connected to each of the electric wires 311. Then, each capacitor CT is housed in an insulating cylinder 310 made of plastic, and is connected to a high voltage bus bar at a terminal 312 via a fuse (F).

The ground side wire 311 of the capacitor CT is the handy case 300
It is connected to the ground GND through the second sensor SR housed in and through the third sensor SF.

The measurement unit 3 is housed in the handy case 300 as a housing, and includes a first sensor S, a second sensor SR, and a third sensor.
The output signal of SF is captured.

With this portable structure, the insulation deterioration monitoring device for electric equipment of the present invention can be mounted and removed in a live state, so that no power outage is required for mounting or removing the device.

Next, Fig. 15 shows the case where the capacitance between the core wire and the shield of a single-core cable or triplex cable is used as a capacitor (CT).

In this case, since it is not necessary to provide a ceramic capacitor on the bus bar, it is suitable for a high voltage circuit, especially for a power transmission system of 10 KV or more.

〔The invention's effect〕

According to the present invention, it is possible to constantly monitor the insulation state of electric equipment and electric equipment such as cables in a live line state.

In addition, insulation deterioration can be reliably detected without being affected by external noise, and its position can be easily specified.

Therefore, the insulation failure can be detected at a minor stage, and an accident due to the insulation failure can be prevented.

[Brief description of drawings]

1 to 13 show an embodiment of the present invention, FIG. 1 is a block diagram of the first embodiment, FIG. 2 is a circuit diagram in which a sensor portion and a measuring portion are combined, and FIG. ) To (C) are front views of the sensor, FIG. 4 is a BH characteristic diagram of the sensor, FIG. 5 is a frequency characteristic diagram thereof, FIG. 6 is a graph showing the detection result of the traveling wave, and FIG. FIG. 8 is a graph showing the detection result of the traveling wave in the case of deterioration, FIG. 8 is a graph showing the detection result of the traveling wave in the case of deterioration of the electric motor, FIG. 9 is a graph of the measurement result, and FIG. 10 (a). ~ (C) and Figs. 11 (a) to (c) are a plan view, a front view and a bottom view of the capacitor, and Fig. 12 is a combined circuit diagram of the sensor section and the measurement section showing the second embodiment, the 13th figure. FIG. 9 is a combination circuit diagram of the sensor unit and the measuring unit showing the third embodiment. FIG. 14 is a circuit diagram showing an example in which the device of the present invention is configured to be portable, and FIG. 15 is a circuit diagram showing an example in which a space between a core wire forming a live line and a shield is used as a capacitor. 1 ... Substation, 2 ... Electricity demand place, 3 ... Measuring unit, S
(S1, S2, S3, S4, S5, S6, S21, S22, S23, S32, S33) …… First
Sensor, SR …… Second sensor, SF, SG …… Third sensor, M1
...... First winding, M2 ...... Second winding, K ...... Core, C, CT
...... Capacitor, P ...... Insulation deterioration point, L (L1, L2, L3, L4,
L5, L21, L22, L23, L32, L33, LF) …… Cable, T1, T2, T3
…… Transformer, M …… Electric motor, B1, B2, B3, B4, B5, B6, B7, B2
1, B31, B32, B33 …… Breaker.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akio Sera 6-1-2 Waki, Waki-cho, Kuga-gun, Yamaguchi Prefecture Mitsui Petrochemical Industry Co., Ltd. (72) Inventor Fukusan Terunaga, Waku Kamachi Kimachi 6-1-2 Mitsui Petrochemical Co., Ltd. (56) Reference JP 63-177074 (JP, A) JP 63-233381 (JP, A) JP 62-240872 ( JP, A) JP 62-90580 (JP, A)

Claims (13)

[Claims] 1. A power transmission path in which a common bus (LF, LG) is connected to a plurality of power cables (L1 to L5) and an electric device (M) via the power cables (L4), and surrounds the power cables. First sensor (S) that detects the traveling wave current generated due to the partial discharge generated at the site when the insulation state of the power transmission path is deteriorated
And a capacitor (C) between each phase of the common bus (LF, LG) and ground.
T, C) and three second sensors (SR) are provided so as to surround the ground line on the ground side of the capacitor (CT, C).
The second sensor (SR) detects the phase in which the traveling wave current is generated and simultaneously generates an external noise, and a third sensor (SR) surrounds all the ground lines on the ground side of the capacitor (CT, C). A sensor (SF, SG) is provided, and the third sensor (SF, SG) is configured to detect a reference signal for determining the traveling direction of the traveling wave current. The first sensor (S), the second sensor A sensor (SR) and a measurement unit (3) that processes signals from the third sensor (SF, SG), and the first sensor (S), the second sensor (SR), and the third sensor (SF, SG) is arranged with the same direction of polarity with respect to the common bus (LF, LG), and the detection start points of the signals from the first sensor (S) and the third sensor (SF, SG) are substantially set. The phase shift measured by the measuring unit (3) in the matched state is about 180 °, and the three second Insulation deterioration is detected by detecting the traveling wave current generated when the insulation deterioration of the power cable (L) or electrical equipment is detected when the signal level of one second sensor (SR) is high. And three second
Of the sensors (SR), the second sensor (S
An insulation deterioration monitoring device for electrical equipment, characterized by detecting the deterioration phase of the insulation deterioration from the R) signal. 2. The first sensor (S), the second sensor (SR) and the third sensor (SF, SG) each have a detection winding wound around an annular core, and each of them has a detection winding. 2. The insulation deterioration monitoring device for electrical equipment according to claim 1, wherein the detection target is passed through the annular core to form a primary winding. 3. The measuring section (3) is a common mode when the signal levels are substantially the same and the phases are the same based on the signals from the three second sensors (SR). 2. The insulation deterioration monitoring device for electric equipment according to claim 1, wherein the insulation deterioration determination device determines that the noise is generated and does not perform the insulation deterioration determination process based on the traveling wave. 4. The first sensor (S) and the second sensor (S)
R), the third sensor (SF, SG) is connected to the first winding (M1) and the second
And the first winding (M1) has both ends short-circuited, the second winding (M2) is a detection winding, and the first sensor (S) The annular cores forming the second sensor (SR) and the third sensor (SF, SG) have a substantially linear BH characteristic in which the super magnetic force and the magnetic flux density have a substantially proportional relationship, and from the low frequency region to the high frequency region. 3. The magnetic permeability is substantially constant.
Insulation deterioration monitoring device for the electric equipment described. 5. The insulation deterioration monitoring device for electric equipment according to claim 1, wherein the first sensor (S) has a function of a zero-phase current transformer that detects a ground fault current of a commercial frequency. 6. The insulation deterioration monitoring device for electric equipment according to claim 4, wherein the core (K) is formed of an amorphous metal. 7. The insulation deterioration monitoring device for electric equipment according to claim 6, wherein the amorphous metal is an amorphous metal containing cobalt as a main component. 8. The device for monitoring insulation deterioration of electrical equipment according to claim 1, wherein the capacitor (CT, C) is formed of dielectric ceramics. 9. The composition of the dielectric ceramic is SrTiO ₃
9. The insulation deterioration monitoring device for electric equipment according to claim 8, wherein the insulation deterioration monitoring device is MgTiO ₃ or BaTiO ₃ . 10. The capacitor (CT, C) is shaped like an insulator, has mechanical and electrical strength, and has a structure that doubles as an insulator of the busbar (or electric wire). 8. An insulation deterioration monitoring device for electric equipment according to 8. 11. The electrical equipment according to claim 10, wherein the capacitor (CT, C) is formed by connecting a plurality of capacitor elements made of dielectric ceramics in series and molding them with an epoxy resin in an insulator shape. Insulation deterioration monitoring device. 12. An insulation deterioration monitoring device for electric equipment according to claim 1, wherein the capacitor (CT, C) uses an electrostatic capacitance between a core wire forming a bus bar and a shield covering the core wire. . 13. An annular core of the first sensor is detachably attached to a power cable (L) to be detected, and
An electric wire having a terminal that is detachably connected is provided on each phase of a bus bar to which the power cable (L) is connected, the capacitor is provided on each electric wire, and the second wire is provided on a ground side electric wire of each capacitor. The sensor (SR) and the third sensor (SF, SG) are provided, and the second sensor (SR), the third sensor (SF), and the measuring unit (3) are incorporated into the housing (300) for portable use. The insulation deterioration monitoring device for electrical equipment according to claim 1.