JPH0678444A - Detecting device for deterioration of insulation - Google Patents

Abstract

PURPOSE:To sensitively detect the current based on the deterioration of insulation of a cable or load flowing to the cable constituting a power system. CONSTITUTION:This detector is equipped with ZCTs 26 and 28 which detect the unbalance current and the earth current flowing in a main cable, and the earth line 38 of ZCT26 pierces it in forward direction, and the earth line 38 of ZCT28 pierces it in reverse direction, and the unbalance currents by the detection of ZCTs 26 and 28 are outputted in the reverse polarities with each other, and the earth currents are outputted in the same polarity, and when the detection currents of each ZCTs 26 and 28 are added with an adder, the unbalance currents are offset with each other, and only the earth current can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulation deterioration detecting device, and more particularly to an insulation deterioration detecting device suitable for detecting insulation deterioration of a distribution line which constitutes a power supply system and an electric device connected to the distribution line.

[0002]

2. Description of the Related Art In an ungrounded power system, a power transformer is connected to a busbar through a circuit breaker, and a cable is connected to this busbar through a circuit breaker for distribution. A configuration for connecting a load is adopted. In such a system, a ground fault relay device as described in JP-A-58-79428 is provided in order to protect the cable and the load from the ground fault. Further, in such a system, in order to detect the insulation deterioration of the load device at an early stage, a configuration in which a cable penetrating ZCT capable of detecting a minute ground fault current is arranged on the power source side of the cable is adopted. That is, when the load device is in the insulation deterioration state, a current corresponding to a ground fault current flows in the cable, and therefore this current is detected by ZCT to detect the insulation deterioration of the load device at an early stage.

[0003]

However, in the non-grounded power supply system, the capacitance of the cable to ground is relatively large,
An unbalanced current is constantly flowing due to the imbalance between these phases. That is, when supplying current to the load, an unbalanced current flows through the capacitance between the conductor of the cable and the sheath (coating) of the cable, and this unbalanced current flows through the ground wire. It is designed to flow. This unbalanced current is generated as a ground fault current on the secondary side of the ZCT. When the ground fault current due to the insulation deterioration of the load equipment is less than or equal to the unbalanced current, the level of the unbalanced current is In consideration of the phase difference, it is absorbed in the unbalanced current, and it is impossible to detect the minute current due to the insulation deterioration. That is, even if the cable is provided with the through-type ZCT, it is possible to reliably detect the state of insulation deterioration when the level of the leakage current accompanying the insulation deterioration is small as in the initial state of the insulation deterioration of the load device. Can not.

An object of the present invention is to provide an insulation deterioration detecting device capable of detecting with high sensitivity a current associated with insulation deterioration of a cable or a load constituting a power supply system.

[0005]

In order to achieve the above object, the present invention provides, as a first device, a first unbalanced current detecting means for detecting an unbalanced current flowing in a cable connecting a power source and a load. A second unbalanced current detecting means for detecting an unbalanced current flowing through the cable with a polarity different from that of the first unbalanced current detecting means, and a ground fault current superimposed on the detected current of the first unbalanced current detecting means. A first ground fault current detecting means,
The second ground fault current detecting means for detecting the ground fault current superposed on the detection current of the second unbalanced current detecting means with the same polarity as the detection current of the first ground fault current detecting means, and the first unbalanced current detecting means. Insulation deterioration detecting device provided with an addition unit that adds the detection current, the detection current of the first ground fault current detection unit, the detection current of the second unbalanced current detection unit, and the detection current of the second ground fault current detection unit, respectively. Is configured.

[0006] As a second device, a first unbalanced current detecting means for detecting an unbalanced current flowing through a cable connecting a power source and a load and a first unbalanced current detecting means for detecting an unbalanced current flowing through the cable. The second unbalanced current detecting means for detecting with different polarities, the first ground fault current detecting means for detecting the ground fault current superimposed on the detection current of the first unbalanced current detecting means, and the second unbalanced current detecting means Second ground fault current detection means for detecting the ground fault current superimposed on the detected current with the same polarity as the detection current of the first ground fault current detection means, and detection current of the second unbalanced current detection means and second ground fault current Limiter means for limiting the level of the current added to the detection current of the detection means to the level of the detection current of the second unbalanced current detection means, the output current of the limiter means, the detection current of the first unbalanced current detection means and the first 1 Detection of ground fault current detection means Flow and is obtained by constituting the in which insulation deterioration detection device and an adding means for adding respectively.

As a third device, a first unbalanced current detecting means for detecting an unbalanced current flowing through a cable connecting a power source and a load, and a first unbalanced current detecting means for detecting an unbalanced current flowing through the cable. The second unbalanced current detecting means for detecting with different polarities, the first ground fault current detecting means for detecting the ground fault current superimposed on the detection current of the first unbalanced current detecting means, and the second unbalanced current detecting means Second ground fault current detection means for detecting the ground fault current superimposed on the detected current with the same polarity as the detection current of the first ground fault current detection means, and the detection current of the first unbalanced current detection means and the first ground fault current. Limiter means for limiting the level of the current added to the detection current of the detection means to the level of the detection current of the first unbalanced current detection means, the output current of the limiter means, the detection current of the second unbalanced current detection means, and the first 2 Detection of ground fault current detection means Flow and is obtained by constituting the in which insulation deterioration detection device and an adding means for adding respectively.

As a fourth device, a pair of zero-phase current transformers each having a coil wound around a three-phase distribution line connecting a power source and a load and detecting a zero-phase current from the current flowing through the coil, And an adder for adding the output currents of the respective zero-phase current transformers, wherein the ground wire connected to the power supply side jacket of the three-phase distribution line is connected to the coils of the respective zero-phase current transformers along the three-phase distribution line. The ground wire inserted between the jacket of the phase distribution line and inserted in each zero-phase current transformer is grounded at its terminal, and the ground wire inserted in one zero-phase current transformer is the three-phase distribution line. The unbalanced current flowing through and the unbalanced current flowing through this ground wire are wired so that they flow in the same direction, and the ground wire inserted in the other zero-phase current transformer is The insulation is poorly wired so that the unbalanced currents flowing through the ground wire flow in opposite directions. It is obtained by constituting the detecting device.

As a fifth device, a pair of zero-phase current transformers each having a coil wound around a three-phase distribution line connecting a power source and a load and detecting a zero-phase current from a current flowing through the coil, A level limiter that limits the detected current of one zero-phase current transformer to the level of the unbalanced current or less, and an adder that adds the output current of the other zero-phase current transformer and the output current of the level limiter. The ground wire connected to the power-side jacket of the three-phase distribution line is inserted between the coil of each zero-phase current transformer and the jacket of the three-phase distribution line along the three-phase distribution line, The ground wire inserted in the current transformer is grounded at its terminal, and the ground wire inserted in one zero-phase current transformer has an unbalanced current flowing in the three-phase distribution line and an unbalanced current flowing in this ground wire. The ground wire inserted in the other zero-phase current transformer is wired so that it flows in the same direction. In which unbalanced current unbalanced current flowing through the distribution line through the ground wire constituted the insulation deterioration detection device is wired to flow in opposite directions.

[0010]

According to the above-mentioned means, when the load is in the insulation deteriorated state, the unbalanced current and the ground fault current accompanying the insulation deterioration flow in the cable. The unbalanced currents are respectively detected by the first and second unbalanced current detecting means, and the ground fault currents are the first and second unbalanced currents.
Each is detected by the ground fault current detection means. Then, the detection output of each detecting means is added by the adding means.
At this time, since the polarities of the detected currents of the first unbalanced current detecting means and the second unbalanced current detecting means are different from each other, the unbalanced currents cancel each other out. On the other hand, since the ground fault currents are both detected with the same polarity, only the current obtained by adding the local fault currents is output from the adding means. Therefore, the insulation deterioration of the load can be detected with high sensitivity from the output signal of the adding means.

When the cable is in a deteriorated insulation state, an unbalanced current and a ground fault current accompanying the deterioration of insulation flow in the cable. The unbalanced current is detected by the first and second unbalanced current detection means, and the ground fault current is detected by the first and second ground fault current detection means, respectively. One of the detection currents of the sum of the detection outputs of the first unbalanced current detection means and the first ground fault current detection means or the sum of the detection outputs of the second unbalanced current detection means and the second ground fault current detection means The sum is added by the adding means in a state where the sum is limited to a level equal to or lower than the unbalanced current. Since the unbalanced currents detected by the respective unbalanced current detection means have different polarities, only the ground fault current is output from the addition means. Therefore, it is possible to detect with high sensitivity that the cable is in a deteriorated state.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a power transformer 10 is a power receiving circuit breaker 1.
It is connected to the power source side bus bar 14 via 2. A grounding system voltage transformer 16 is connected to the power supply side bus bar 14 and a limiting resistor 18 for determining an effective grounding current of a non-grounding system.
Are connected. A main circuit cable 24 is connected to the power source side bus bar 14 via a power distribution breaker 20 and a power source terminal portion 22. Two ZCTs 26 and 28 are provided as grounding current transformers in the middle of the main circuit cable 24, and a load 30 composed of an induction motor or the like is connected to the end of the main circuit cable 24.

The ZCTs 26 and 28 are connected to the main circuit cable 24.
The ground side current can be detected from the zero-phase current flowing through the secondary side, and the secondary side has terminals C1 and C of the comparison / determination unit 32.
2, C3 and C4, respectively. Each ZCT2
Resistors 34 and 36 for converting a current on the secondary side into a voltage are connected to the secondary sides of the sensors 6 and 28. And ZCT2
6, the ground wire 38 connected to the power supply terminal portion 22 penetrates in the forward direction, and the ZCT 28 penetrates the ground wire 38 in the reverse direction. Therefore, ZCT26 and ZCT28
The detected values of the unbalanced currents output from the secondary side of the are detected with opposite polarities. That is, each phase 24A, 24B, 24C of the main circuit cable 24 and the sheath 4
Since there are ground capacitances C1, C2, C3 between the two, when a current flows through the main circuit cable 24, a current flows through the ground capacitances C1, C2, C3, the sheath 42, and the ground wire 38. Flowing. The vector of the current flowing through each phase is represented as shown in FIG. 2, and the vector composition is not completely zero, and the unbalanced current 44 flows through the sheath 42 and the ground wire 38. This unbalanced current is generated on the secondary side of the ZCT 26 as shown in FIG.
Is output as a waveform as shown in (A) of
A waveform as shown in FIG. 3B is output to the secondary side of 28. Therefore, each ZCT26 and Z
When the unbalanced currents of CT28 are added, the unbalanced currents cancel each other out, and the sum of the unbalanced currents becomes 0 as shown in FIG. On the other hand, when a current associated with a ground fault flows through the main circuit cable 24, a ground fault current of the same polarity flows through the secondary side of each ZCT 26, 28. That is, the ZCTs 26 and 28 and the resistors 34 and 36 constitute not only the unbalanced current detecting means but also the ground fault current detecting means.

The comparison / determination unit 32 is constructed by including amplifiers 46 and 48 and an adder 50, and the input sides of the amplifiers 46 and 48 are connected to the ZCTs 26 and 28. Amplifier 46
Is configured to amplify the signal output from the secondary side of the ZCT 26 and output the amplified signal to the adder 50.
The amplifier 48 amplifies the signal output from the secondary side of the ZCT 28 and outputs the amplified signal to the adder 50. The adder 50 adds the output signal of the amplifier 46 and the output signal of the amplifier 48, and outputs the added signal 50A.

In the above structure, when the load 30 suffers insulation deterioration and a ground fault current I1 flows through the main circuit cable 24 as a result of this insulation deterioration, as shown in FIG. Unbalanced current 26A, 2 of ZCT26 output
8A is superimposed. The combined signals 46A and 48A are output from the amplifiers 46 and 48, respectively. That is, the unbalanced current 26A of the ZCT 26 output is the ground fault current I1.
The combined value of these currents is
6A. On the other hand, the polarities of the unbalanced current 28A output from the ZCT 28 and the ground fault current I1 are opposite to each other, so that the signal obtained by combining these currents becomes the signal 48A. And signal 46
When A and the signal 48A are added by the adder 50, the adder 5
From 0, a signal 50A equal to twice the ground fault current I1 is output. That is, since the ZCTs 26 and 28 have the ground wires 38 penetrating in opposite directions, the polarities of the unbalanced currents are opposite to each other, and when the output signals of the ZCTs 26 and 28 are combined, the unbalanced currents cancel each other out. Only the leakage current I1 can be detected. Moreover, since a current equal to twice the ground fault current can be detected, the load 30
It is possible to detect with high sensitivity the current associated with the insulation deterioration of the.

Next, another embodiment of the present invention will be described with reference to FIGS. 6 and 7.
It will be described based on. In this embodiment, a limiter 52 as a level limiter for limiting the output signal of the amplifier 48 to the level of the unbalanced current or less is provided between the amplifier 48 and the adder 50.
Since the other configurations are the same as those of the above-described embodiment, the same components are designated by the same reference numerals and the description thereof will be omitted.

In the above structure, when the main circuit cable 24 is in the insulation deterioration state and the ground fault current I2 flows in the main circuit cable 24 due to the insulation deterioration, the ground fault current I2 becomes the unbalanced currents 26A and 28A. Amplifiers 4 superimposed on each other
Signals 46A and 4 associated with the generation of the ground fault current from 6 and 48
8A is output. The output signal 46A of the amplifier 46 is directly input to the adder 50, but the output signal 48A of the amplifier 48 is limited in level to the level of the unbalanced current by the limiter 52 and output as the signal 52A. That is, the signal 52A from which the component of the ground fault current I2 is removed from the unbalanced current is input to the adder 50. Then, in the adder 50, the signal 46A and the signal 52A
By adding and, the signal 50A including only the ground fault current I2 can be output from the adder 50. Therefore, according to the present embodiment, even if the main circuit cable 24 is in the insulation deterioration state, the insulation deterioration of the main circuit cable 24 can be detected with high sensitivity.

Further, in the above embodiment, the limiter 52
In the above description, the amplifier is provided between the amplifier 48 and the adder 50. Instead of inserting the limiter 52 between the amplifier 48 and the adder 50, the limiter 52 is inserted between the amplifier 46 and the adder 50. Also, as in the above embodiment, the main circuit cable 24
Insulation deterioration can be detected with high sensitivity.

When installing the ZCTs 26, 28, the comparison / determination unit 32, etc. in the above-described embodiment, as shown in FIG. 8, the Z is placed in the detection unit 56 in the closed switchboard 54.
The CTs 26 and 28 are housed, and the comparison / determination device 32 is installed on the back side of the front door 58. The detection unit 56 is housed in the load side main circuit cable processing chamber 60, and
6 to the main circuit cable 24. Earth wire 38
Is connected to the ground bus 62, and the secondary side of each ZCT 26, 28 is connected to the comparison / determination unit 32 via the shield wire 64.
By adopting such an arrangement and connection configuration, it is possible to rationally arrange the units and standardize the assembling work. Further, malfunction due to noise can be prevented. Metal walls 70 and 72 are provided between the power receiving circuit breaker chamber 66, the power supply lead-in cable chamber 68, and the load-side main circuit cable processing chamber 60.
The periphery of the power distribution breaker chamber 74 and the busbar chamber 76 are partitioned by metal walls 78, 80, 82. Further, the power supply lead-in cable 84 is connected to the disconnecting portion 88 via the conductor 86. Further, the disconnection section 90 is connected to the busbars 3R, 3S, 3T. The disconnection section 92 is connected to the bus bar 3T, and the disconnection section 94 is connected to the detection unit 56 via the conductor 96.

[0020]

As described above, according to the present invention,
The cable connecting the power supply and the load is provided with a pair of detection means for detecting both the unbalanced current and the ground fault current flowing through the cable,
The unbalanced currents have the opposite polarities and the ground fault currents have the same polarities, and only the currents associated with cable insulation deterioration and load insulation deterioration are detected by each detection means. Also, the insulation deterioration of the load can be detected with high sensitivity.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a vector diagram of a cable unbalanced current.

FIG. 3 is a waveform diagram for explaining a method of removing a cable unbalanced current.

FIG. 4 is a configuration diagram of a comparison / determination device.

FIG. 5 is a waveform diagram for explaining a method for detecting a load insulation deterioration state.

FIG. 6 is a configuration diagram showing another embodiment of a comparison / determination device.

FIG. 7 is a waveform diagram for explaining a method for detecting a cable insulation deterioration state.

FIG. 8 is a configuration diagram of a closed switchboard in which the device according to the present invention is installed.

[Explanation of symbols]

 10 power transformer 12 power receiving circuit breaker 14 power supply side bus bar 20 power distribution circuit breaker 22 power source terminal part 24 main circuit cable 26, 28 ZCT 30 load 32 comparison judgment device 34, 36 resistance 46, 48 amplifier 50 adder 52 limiter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hironobu Abe, 3-7-1, Ichibancho, Aoba-ku, Sendai-shi, Miyagi Prefecture Tohoku Electric Power Co., Inc. (72) Osamu Funayama, 5-chome, Miyagino-ku, Sendai-shi, Miyagi Prefecture 2-1 Tohoku Electric Power Co., Inc. Shin-Sendai Thermal Power Plant (72) Inventor Yoji Sasaki Ube Guard Kawara, Hachinohe City, Aomori Prefecture 1-1 Hyakunohe Thermal Power Plant (72) Tohoku Electric Power Co., Inc. Kazuo Takahashi Miyagi Miyagi Prefecture 1 Maejima, Daigasakihama, Shichigahama-cho, Tohoku Electric Power Company Sendai Thermal Power Plant (72) Inventor Hideo Ochiai 2-200 Momoyamacho, Niigata City, Niigata Prefecture Tohoku Electric Power Co., Inc. Niigata Thermal Power Station (72) Inventor Shoichi Goi Akita, Akita Prefecture 217-6 Shimokawabata, Kojima, Iijima-shi, Tohoku Electric Power Co., Inc. Akita Thermal Power Station (72) Inventor Shigemitsu Mori Miya, Sendai City Miyagi Prefecture Tohoku Electric Power Co., Inc. Shinsendai Thermal Power Plant (2-1) Minato 5-chome, Jono-ku (72) Inventor Akio Kitagawa 1-155, Isoyama, Kamezuka-hama, Seigo-cho, Kitakanbara-gun, Niigata Prefecture Tohoku Electric Power Co., Inc. Higashi-Niigata Thermal Power Plant (72) ) Inventor Yoshinori Ito 3-7-1, Ichibancho, Aoba-ku, Sendai-shi, Miyagi Tohoku Electric Power Co., Inc. (72) Inventor Akiyama 3-7-1, Ibancho, Aoba-ku, Sendai, Miyagi Tohoku Electric Power Co., Inc. In-house (72) Inventor Kazushi Ono 3-7-1, Ichibancho, Aoba-ku, Sendai City, Miyagi Prefecture Tohoku Electric Power Co., Inc.

Claims (5)

[Claims] 1. A first unbalanced current detecting means for detecting an unbalanced current flowing through a cable connecting a power source and a load, and an unbalanced current flowing through the cable with a polarity different from that of the first unbalanced current detecting means. The second unbalanced current detecting means, the first ground fault current detecting means for detecting the ground fault current superimposed on the detected current of the first unbalanced current detecting means, and the detected current of the second unbalanced current detecting means. Second ground fault current detection means for detecting the generated ground fault current with the same polarity as the detection current of the first ground fault current detection means, detection current of the first unbalanced current detection means and detection of the first ground fault current detection means An insulation deterioration detecting device comprising: an electric current; and an adding means for adding the detected current of the second unbalanced current detecting means and the detected current of the second ground fault current detecting means, respectively. 2. A first unbalanced current detecting means for detecting an unbalanced current flowing through a cable connecting a power supply and a load, and an unbalanced current flowing through the cable with a polarity different from that of the first unbalanced current detecting means. The second unbalanced current detecting means, the first ground fault current detecting means for detecting the ground fault current superimposed on the detected current of the first unbalanced current detecting means, and the detected current of the second unbalanced current detecting means. Second ground fault current detection means for detecting the generated ground fault current with the same polarity as the detection current of the first ground fault current detection means, detection current of the second unbalanced current detection means and detection of the second ground fault current detection means Limiter means for limiting the level of the added current to the current to the level of the detected current of the second unbalanced current detecting means, the output current of the limiter means, the detected current of the first unbalanced current detecting means and the first ground fault current Add the detection current of each detection means Insulation deterioration detecting device comprising: 3. A first unbalanced current detecting means for detecting an unbalanced current flowing through a cable connecting a power supply and a load, and an unbalanced current flowing through the cable with a polarity different from that of the first unbalanced current detecting means. The second unbalanced current detecting means, the first ground fault current detecting means for detecting the ground fault current superimposed on the detected current of the first unbalanced current detecting means, and the detected current of the second unbalanced current detecting means. Second ground fault current detection means for detecting the generated ground fault current with the same polarity as the detection current of the first ground fault current detection means, detection current of the first unbalanced current detection means and detection of the first ground fault current detection means Limiter means for limiting the level of the added current to the current to the level of the detected current of the first unbalanced current detecting means, the output current of the limiter means, the detected current of the second unbalanced current detecting means and the second ground fault current Add the detection current of each detection means Insulation deterioration detecting device comprising: 4. A pair of zero-phase current transformers, each having a coil wound around a three-phase distribution line connecting a power source and a load, for detecting a zero-phase current from a current flowing through the coil, and each zero-phase transformer. A ground line connected to the power supply side jacket of the three-phase distribution line along the three-phase distribution line and the coil of each zero-phase current transformer and the outside of the three-phase distribution line. The ground wire inserted between each zero-phase current transformer and the grounded part is grounded at its end, and the ground wire inserted in one zero-phase current transformer flows through the three-phase distribution line. The current and the unbalanced current flowing through this ground wire are wired so that they flow in the same direction, and the ground wire inserted into the other zero-phase current transformer flows through this ground wire with the unbalanced current flowing through the three-phase distribution line. An insulation deterioration detection device that is wired so that unbalanced currents flow in opposite directions. 5. A pair of zero-phase current transformers, each having a coil wound around a three-phase distribution line connecting a power source and a load, for detecting a zero-phase current from a current flowing through the coil, and one zero-phase current transformer. A level limiter for limiting the detected current of the current transformer to the level of the unbalanced current or less; and an adder for adding the output current of the other zero-phase current transformer and the output current of the level limiter, The ground wire connected to the power supply side jacket of the phase distribution line is inserted between the coil of each zero-phase current transformer and the jacket of the three-phase distribution line along the three-phase distribution line, The ground wire inserted is grounded at its terminal, and the ground wire inserted in one zero-phase current transformer has the unbalanced current flowing through the three-phase distribution line and the unbalanced current flowing through this ground wire flowing in the same direction. Ground wire inserted in the other zero-phase current transformer An insulation deterioration detection device that is wired so that the balanced current and the unbalanced current that flows through this ground wire flow in opposite directions.