JPH07119782B2 - Insulation deterioration detector for electrical equipment and cables - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an insulation deterioration detecting device for an electric device and a cable for detecting corona discharge and partial discharge generated when insulation of the electric device and the cable is deteriorated. In particular, the detection of an insulation deterioration signal formed by using, for example, a cobalt-based amorphous core, which is manufactured to have a high magnetic permeability, a small residual magnetism and a coercive force, and a proportional relationship between the magnetomotive force and the magnetic flux density. The present invention relates to an electrical device having a section and an insulation deterioration detecting device for a cable.

[Conventional technology]

Conventionally, insulation resistance test, DC high voltage test, AC withstand voltage test and the like have been used as methods for detecting insulation deterioration of electric devices and cables.

The insulation resistance test measures the insulation resistance of an insulator such as a device with an insulation resistance meter to check the deterioration condition.

In the DC high voltage test or the AC withstand voltage test, a DC high voltage or an AC high voltage is applied to an insulator such as a device for a certain period of time, and the withstand voltage performance is confirmed at that time to judge whether the insulation state is good or bad.

In the insulation resistance test, the measuring instrument is small and lightweight and easy to operate, but the insulation resistance value itself may be affected by humidity, etc., so it is difficult to judge whether or not it can withstand use in actual use conditions. .

The DC high-voltage test or AC withstand voltage test guarantees that the device can withstand the operating voltage for the time being, but it is difficult to determine the degree of deterioration, and there is a risk of dielectric breakdown of the equipment due to the test.

In addition, the insulation resistance test, DC high voltage test, and AC withstand voltage test must be performed with the equipment disconnected from the power circuit.

[Problems to be Solved by the Invention]

The present invention is intended to solve the problems of the prior art, has a high magnetic permeability, has a substantially constant magnetic permeability from a low frequency to a high frequency range, and has a remanence and a coercive force. Insulation deterioration detection for electrical equipment and cables having a transformer having a cobalt-based amorphous core, both of which are small and having a linear BH curve, and a detection unit composed of only a circuit impedance element such as a capacitor It is a device that can detect insulation deterioration in the actual usage state of equipment, and can perform a deterioration state judgment test even in a stopped state disconnected from the circuit. It is an object of the present invention to provide an insulation deterioration detecting device.

[Means for Solving the Problems]

The electric device and the insulation deterioration detecting device for a cable according to the present invention have a principle configuration as shown in FIG.

Reference numerals 1 and 2 are first and second transformers, respectively, which have a high magnetic permeability, have a substantially constant magnetic permeability from a low frequency to a high frequency range, and have a small residual magnetism and a small coercive force. The BH curve comprises cores 1A and 2A having linear magnetic properties.

Reference numeral 3 denotes an impedance circuit which is composed of a capacitor, a resistor, a reactor, a semiconductor element, etc. either alone or in combination.

Reference numeral 4 denotes a main circuit for supplying a detected current including a signal of insulation deterioration.

Reference numerals 11 and 12 denote primary windings of the first transformer 1 having the same number of windings and winding start terminals 11-
a, 12-a and winding end terminals 11-b, 12-b, and winding start terminals 11-a, 12-a and winding end terminals 11-b, 12-, respectively.
It is wound so as to be differentially connected to the core 1A when a current is passed toward b.

Reference numeral 13 is a secondary winding of the first transformer 1.

Reference numeral 21 is a primary winding of the second transformer 2.

22 is a secondary winding of the second transformer 2.

11-a is a winding start terminal of the primary winding 11 of the first transformer 1, and 11-b is a winding end terminal of the same.

12-a is a winding start terminal of the primary winding 12 of the first transformer 1, and 12-b is a winding end terminal of the same.

21-a and 21-b are terminals of the primary winding 2 of the second transformer 2.

22-a and 22-b are terminals of the secondary winding 22 of the second transformer 2.

The terminal 11-b and the terminal 21-a, the terminal 12-b and the terminal 21-b are connected by external wiring, and the impedance circuit 3 is connected between the terminal 11-b and the terminal 12-a.

The terminals 11-a and 12-a are connected to the main circuit 4, and a detected current containing a signal of insulation deterioration is passed through the main circuit 4.

The signal output of the insulation deterioration is output from both terminals 13-a, 13-b of the secondary winding 13 of the first transformer 1 or both terminals 22-a, 22-b of the secondary winding 22 of the second transformer 2. Obtained from Either one or both of the signal outputs may be used depending on the application.

The structure of the present invention is as follows. That is, according to the present invention, the number of windings is the same for each core having a proportional relationship between the magnetomotive force and the magnetic flux density, and the winding start terminals (11-
a, 12-a) and winding end terminals (11-b, 12-b), and winding start terminals (11-a, 12-a) to winding end terminals (11-b, 12-b). Two primary windings (11), (12) and a secondary winding (13) are wound so as to be differentially connected to the core when a current is applied to the core. A first transformer (1) and a core having a proportional relationship between magnetomotive force and magnetic flux density, provided with a primary winding (21) and a secondary winding (22) for cutting high frequency current components. A second transformer (2) and an impedance circuit (3) are provided, and the terminal (11) at the end of winding of the primary winding (11) of the first transformer is provided.
-B) and the winding end terminal (12-b) of the primary winding (12), the terminal (21- of the primary winding (21) of the second transformer (2).
a) and (21-b) are connected, the winding end terminal (11-b) of the primary winding (11) of the first transformer (1) and the winding start terminal (12-a) of the primary winding (12). ) And an impedance circuit (3) are connected to the winding start terminal (11-a) of the primary winding (11) of the first transformer (1) and the primary winding (1).
When the winding start terminal (12-a) of 2) is connected to the housing of the electric device or the shield of the power cable and the ground,
Both terminals (13- of the secondary winding (13) of the first transformer (1)
a), (13-b) or both terminals (22-a), (22-b) of the secondary winding (22) of the second transformer (2) indicate deterioration of insulation of the electric device or power cable. It has a structure as an insulation deterioration detecting device for an electric device and a cable, which is characterized by obtaining a signal.

Alternatively, the core forming the first transformer (1) and the second transformer (2) is made of an amorphous alloy containing cobalt as a main component, and insulation of electrical equipment and cables is provided. It has a configuration as a deterioration detection device.

[Action]

The main circuit 4 was weighed with the fundamental wave of the charging current and the leakage current of the insulator and its harmonics, and the high frequency corona discharge current, the partial discharge current, and the kick-like pulse current indicating that the insulator was deteriorated. When a current is passed, the entire current of the main circuit flows through the primary winding 11 of the first transformer 1, but the impedance 3 of the primary winding 12 of the first transformer 1 flows from the entire current of the main circuit. An electric current flows by subtracting the electric current like a belt. This current flows in series through the primary winding 21 of the second transformer 2.

At this time, the magnetomotive force of the core 1A is a vector combination of the magnetomotive force due to the current of the primary winding 11 and the magnetomotive force due to the current of the primary winding 12, but the primary windings 11 and 12 are wound in the same direction, Since the directions of the current flowing through the primary winding 11 and the current flowing through the primary winding 12 are opposite to each other with respect to the winding start and the winding end, the magnetomotive force of the core 1A is caused by the current of the primary winding 11. It is the vector difference between the magnetic force and the magnetomotive force due to the current in the primary winding 12.
In the secondary winding 13 of the first transformer 1, a voltage is generated due to the change in magnetomotive force of the core 1A.

Further, the magnetomotive force of the core 2A is caused by the current obtained by subtracting the current flowing through the impedance circuit 3 from the total current of the main circuit in a vector manner, and the voltage caused by the change in the magnetomotive force is the secondary winding 22 of the second transformer 2. Occurs in.

Therefore, by properly selecting the magnetic circuit such as the size and shape of the core 1A and the core 2 and the number of windings of each transformer, the type of impedance in the impedance circuit 3, and the characteristic constants, the main circuit current can be reduced. The deteriorated signal component of the insulator composed of the superimposed high-frequency or pulse-shaped signal is output as a voltage signal discriminated from the secondary winding 13 of the first transformer 1 or the secondary winding 22 of the second truss 2. Obtainable.

〔Example〕

FIG. 2 shows the configuration of an embodiment of an electric equipment and cable insulation deterioration detecting device of the present invention, and shows the case of application in the use state of a high voltage power cable. 100
And 200 are cores made of a cobalt-based amorphous alloy that have a high magnetic permeability, a substantially constant magnetic permeability from the low frequency to the high frequency range, and a hysteresis characteristic such as flat. VATROVAC-6025F, which is a product of the same company, is used. Core 100
Both primary windings 101 and 102 penetrate in one direction in the same direction, and a secondary winding 103 for signal detection is provided,
The first transformer 104 is configured. The core 200 is provided with a primary winding 201 and a secondary winding 202 to form a second transformer 203. C is a capacitor element forming an impedance circuit. 300 is a magnetic shield housing for preventing noise signals from entering from the outside. A power cable 400 is a device under test, and has a structure in which a conductor 401 is covered with an insulator 402, a shield 403 is provided on the conductor 401, and a sheath insulator 404 is provided on the shield 403. In this case, the main circuit current i ₁ required for measurement is taken out from the shield 403. The test is performed while measuring the ground voltage from the cable head 405.

Now, the main circuit current i ₁ is the low-frequency current i _E that is the fundamental wave of the charging current and leakage current of the insulator and its harmonics, and the corona discharge current and partial discharge current that are deterioration signals of the insulator, and kick-like current. When the high frequency current i _P , which is a pulse current, is superimposed, the main circuit current i ₁ flows through the primary winding 101 of the first transformer 104. The primary winding 201 of the second transformer 203 has a large inductive relatance for a high frequency current and a small inductive reactance for a low frequency current, and the capacitor C has a capacitive reactance for a high frequency current. Since it is small and the capacitive reactance is large with respect to the low frequency current, the high frequency current i _P flows into the capacitor C, and the low frequency current i _E passes through the primary winding 201 of the second transformer 203 to the first transformer 104. It flows through the primary winding 102.

Therefore, the magnetomotive force of the core 100 components due to the low frequency current i _E will only element due to canceled out by the high-frequency current i _P, due from the secondary winding 103 of first transformer 104 to the high-frequency current i _P It is possible to obtain the detection signal voltage e _P that

Similarly, the detection signal voltage e _E resulting from the low frequency current i _E can be obtained from the secondary winding 202 of the second transformer 203.

FIG. 3 shows the detection signal voltage e _E caused by the main circuit current i ₁ , the low frequency current i _E, and the detection signal voltage e caused by the high frequency hand current i _P.
This figure shows the relationship of _P with time.

FIG. 4 shows an application example of the present invention to a constant monitoring device for detecting insulation deterioration of a high voltage cable constructed according to the basic principle of FIG. In FIG. 4, reference numeral 500 denotes an insulation deterioration detection unit according to the present invention, 501 and 502 terminals for obtaining a detection signal voltage e _P resulting from the high frequency current i _P in the embodiment shown in FIG.
503 and 504 are terminals for obtaining the detection signal voltage e _E resulting from the low frequency current i _E. In FIG. 4, the temporary windings 101 and 102 in FIG. 2 are replaced with the core wire of the coaxial cable 505 and the shield wire of the coaxial cable 505, respectively. Is an impedance and is for preventing magnetic saturation of the core when a low frequency current such as a charging current becomes large, and is connected to the tertiary winding 204 provided on the core 200. . Reference numeral 600 denotes a signal receiving device, which is a pulse wave input circuit 60.
1, a fundamental wave input circuit 602, amplifiers 603 and 604, a phase comparator 605, a pulse counter 606, a clock circuit 607, a time setting circuit 608, and an output circuit 609.

When the insulation performance of the insulator 402 is deteriorated by the power tree 400 due to a water tree phenomenon, an electrical tree phenomenon, or external damage, a corona discharge current, a partial discharge current, or a kick-like discharge current, that is, a kick-like discharge current The insulation deterioration signal current is superimposed on the charging current of the insulator 402 and flows to the ground through the shield 403. The insulation deterioration detection unit 500 discriminates between the signal component due to the insulation deterioration signal current and the signal component due to the charging current by the pulse wave input circuit 601 and the fundamental wave input circuit 602, and inputs them to the signal receiving device 600.

In the signal receiving device 600, the outputs of the pulse wave input circuit 601 and the fundamental wave input circuit 602 are amplified by amplifiers 603 and 604, respectively, and then added to a phase comparator 605 to isolate the charging current signal, which is the fundamental wave, from each phase. The presence or absence of a pulse wave of the deterioration signal current is detected and counted by the pulse counting circuit 606. The pulse counting circuit 606 is a clock circuit 607.
Of the reference clock generated by the time setting circuit 608 is counted, and the insulation deterioration signal pulse is counted within the set predetermined time, and when the count value exceeds the predetermined value, an output signal is generated to the output circuit 609. To do.

In the output circuit 609, an alarm indicating that the insulation deterioration signal has been detected is generated, and a disconnection signal to a circuit breaker (not shown) is generated in order to disconnect the power cable 400 from the power source due to deterioration when necessary. Also, an output is generated to a data processing device (not shown), which causes the data processing device to perform data analysis processing such as the frequency of occurrence of insulation deterioration pulses for each phase of the charging current, which is the fundamental wave, to determine the degree of deterioration. And determine the cause of deterioration.

In FIG. 4, a weak ground can be detected by changing the input to the input of the fundamental wave signal input circuit 602 so as to apply a zero-phase voltage from an instrument grounding transformer (not shown).

As described above, according to the apparatus shown in FIG. 4, it is possible to constantly monitor with high reliability the insulation deterioration of the high-voltage cable with a simple structure, and prevent an accident due to the insulation deterioration of the high-voltage cable. it can.

FIG. 5-1 shows a case where the apparatus of FIG. 4 is applied to a DC high voltage test or an AC withstand voltage test. Fig. 5-2 shows Fig. 5-
1 shows the same purpose as FIG. 1, but shows the case where the apparatus according to the present invention is installed on the high voltage side, and when there is a set leak of the test apparatus, its influence is eliminated. 50 in both figures
Reference numeral 0 is an insulation deterioration detecting unit shown in FIG. 4, 600 is a signal receiving device, 700 is a voltage applying device for withstanding voltage test, and 800 is an object to be tested. In this way, by using the device of the present invention in combination with the voltage applying device, it is possible to know the state of deterioration of the insulator, so if the application of high voltage is dangerous, perform an operation such as stopping the test. It becomes possible to prevent the dielectric breakdown of the DUT in advance.

In the configuration shown in FIG. 2, the cores 100 and 200 are the above-mentioned cobalt-based amorphous cores, which are VA of Bakuumshmerze Co.
When TROVAC-6025F is used, the insulation deterioration signal level is S, and the signal level of the sum of the insulator charging current and leakage current is N
In that case, an S / N ratio of about 120 dB can be easily obtained.

As described above, the insulation deterioration detecting device for electric equipment and cable having a large S / N ratio with a simple structure can be realized at low cost, small size and light weight.

The above cobalt-based amorphous alloy is cobalt (C
o), iron (Fe), silicon (Si), boron (B), molybdenum (Mo), nickel (Ni), and has the formula Co _a Fe _b Si _c B _d Mo _e Ni
_f where a to f indicate the atomic percentage of each component element, a = 50 to 90, b = 1 to 10, c = 5 to 20, d = 0 to 20, e = 0 to 20, f = 1 to 5 And the sum of a to f is 100.

It is represented by.

The cores 100 and 200 are toroidal cores formed by winding a ribbon made of this cobalt-based amorphous alloy a large number of times and molding it into a ring shape, for example. This cobalt-based amorphous alloy toroidal core can be molded into a ring shape and then heat-treated at a temperature of 150 to 450 ° C. for 5 to 180 minutes to obtain a desired transmittance. The heat treatment is preferably performed in a DC magnetic field or an AC magnetic field in order to make the performance uniform, and more stable performance can be obtained by further performing the heat treatment in a nitrogen atmosphere.

〔The invention's effect〕

As described above, according to the insulation deterioration detecting device for an electric device and a cable of the present invention, it is possible to detect with high sensitivity the degree of deterioration of the insulator of the electric device and the cable in a use condition, and to the continuous monitoring device. When applied, it is possible to prevent accidents due to insulation breakdown and the like, and it is possible to obtain an inexpensive, small-sized and lightweight electric device and a cable insulation deterioration detection device.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle configuration of an insulation deterioration detecting device for electric equipment and cables according to the present invention, and FIG. 2 is a view showing an embodiment of insulation deterioration detecting device for electric equipment and cables according to the present invention. The figure shows the main circuit current in the embodiment shown in FIG.
i _1, the detection signal voltage e _E due to the low frequency current i _E, the high-frequency current
FIG. 4 is a diagram showing the relationship of the time-dependent change of the detection signal voltage e _P caused by i _P , and FIG. 4 is an example of application of the present invention to a constant monitoring device for insulation deterioration detection of a high voltage cable constructed according to the basic principle of FIG. FIG. 5-1 is a diagram showing a case where it is applied to a DC high voltage test or an AC withstand voltage test, and FIG. 5-2 has the same purpose as FIG. It is a figure which shows the case where it installs in the side. 1,104 …… First transformer 2,203 …… Second transformer 3 …… Impedance circuit 4 …… Main circuit 1A, 2A, 100,200 …… Core 11,12,21,101,102,201 …… Primary winding 11-a, 12-a… … Winding start terminal 11-b, 12-b …… Winding start terminal 11-b, 12-b …… Winding end terminal 13,22, 103, 202 …… Secondary winding 13-a, 13-b, 21-a, 21 -B, 22-a, 22-b, 501 to 504 ... Terminal 204 ... Third winding 300 ... Magnetic shield housing 400 ... Power cable 401 ... Conductor 402 ... Insulator 403 ... Shield 404 ... … Sheath insulator 405 …… Cable head 500 …… Insulation deterioration detector 505 …… Coaxial cable 600 …… Signal receiver 601 …… Pulse wave input circuit 602 …… Basic wave input circuit 603,604 …… Amplifier 605 …… Phase comparison 606 …… Pulse counter 607 …… Clock circuit 608 …… Time setting circuit 609 …… Output circuit 700 …… Voltage withstanding voltage application device 800 …… DUT i ₁ …… Main circuit current i _E …… Low frequency current i _P …… High frequency current e _P , e _E …… Detection signal voltage C …… Capacitor

Claims (2)

[Claims] 1. A winding start terminal (11-a, 12-a) and a winding end terminal (11-b, 11-a, 12-a) having the same number of windings with respect to a core having a proportional relationship between magnetomotive force and magnetic flux density. 12-b), and when a current is passed from each winding start terminal (11-a, 12-a) toward the winding end terminal (11-b, 12-b), it is different from the core. A first transformer (1) having two primary windings (11) and (12) and a secondary winding (13) wound so as to be dynamically connected, and a magnetomotive force and a magnetic flux density. A second transformer (2) having a primary winding (21) and a secondary winding (22) for cutting a high-frequency current component with respect to a core having a proportional relationship, and an impedance circuit (3) And a terminal (11) at the end of winding of the primary winding (11) of the first transformer.
-B) and the winding end terminal (12-b) of the primary winding (12), the terminal (21- of the primary winding (21) of the second transformer (2).
a) and (21-b) are connected, the winding end terminal (11-b) of the primary winding (11) of the first transformer (1) and the winding start terminal (12-a) of the primary winding (12). ) And an impedance circuit (3) are connected to the winding start terminal (11-a) of the primary winding (11) of the first transformer (1) and the primary winding (1).
When the winding start terminal (12-a) of 2) is connected to the housing of the electric device or the shield of the power cable and the ground,
Both terminals (13- of the secondary winding (13) of the first transformer (1)
a), (13-b) or both terminals (22-a), (22-b) of the secondary winding (22) of the second transformer (2) indicate deterioration of insulation of the electric device or power cable. A device for detecting deterioration of electrical equipment and cables, which obtains a signal. 2. The core for forming the first transformer (1) and the second transformer (2) is made of an amorphous alloy containing cobalt as a main component. The insulation deterioration detecting device for an electric device and a cable according to item 1.