JP2732000B2 - Insulation degradation detector - Google Patents

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 apparatus, and more particularly to an insulation deterioration detecting apparatus suitable for detecting insulation deterioration of a power distribution line constituting a power supply system and electric equipment connected to the power distribution line.

[0002]

2. Description of the Related Art In an ungrounded power system, a power transformer is connected to a bus via a circuit breaker, a cable is connected to the bus via a circuit breaker for distribution, and an induction motor or the like is connected to the cable. A configuration for connecting a load is employed. In such a system, a ground fault relay device as described in JP-A-58-79428 is provided to protect cables and loads from a ground fault. Further, in such a system, in order to detect insulation deterioration of a load device at an early stage, a configuration is employed in which a cable penetrating type ZCT capable of detecting a small ground fault current is arranged on the power supply side of the cable. That is, when the load device is in an insulation deterioration state, a current corresponding to a ground fault current flows through the cable. Therefore, this current is detected by ZCT, and the insulation deterioration of the load device is detected at an early stage.

[0003]

However, in an ungrounded power supply system, the capacitance of the cable to the ground is relatively large,
An unbalanced current due to the imbalance between the phases of this value is constantly flowing. That is, when a current is supplied to a load, an unbalanced current flows through a cable through a capacitance between a conductor of the cable and a sheath of the cable, and the unbalanced current flows through a ground wire. To flow. This unbalanced current is generated as a ground fault current on the secondary side of the ZCT. When the ground fault current accompanying the insulation deterioration of the load equipment is less than the unbalanced current, the unbalanced current It is absorbed in the unbalanced current due to the phase difference, and it is not possible to detect the minute current accompanying the insulation deterioration. That is, even if the cable is simply provided with a through-type ZCT, it is possible to reliably detect the state of insulation deterioration when the level of leakage current accompanying insulation deterioration is small, such as in the initial state of insulation deterioration of load equipment. Can not.

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

[0005]

In order to achieve the above object, the present invention provides, as a first device, first unbalanced current detecting means for detecting an unbalanced current flowing in a cable connecting a power supply 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,
A second ground fault current detecting means for detecting a ground fault current superimposed on the detected current of the second unbalanced current detecting means with the same polarity as the detected current of the first ground fault current detecting means; The detected current, the detected current of the first ground-fault current detecting means, the detected current of the second unbalanced current detecting means, and the detected current of the second ground-fault current detecting means are respectively added , and the first ground-fault current detecting means and the
(2 ) An insulation deterioration detecting device comprising an adding means for detecting only a ground fault current detected by a ground fault current detecting means .

As a second device, a first unbalanced current detecting means for detecting an unbalanced current flowing in a cable connecting a power supply and a load, and a first unbalanced current detecting means for detecting an unbalanced current flowing in the cable are provided. A second unbalanced current detecting means for detecting with a different polarity, a first ground fault current detecting means for detecting a ground fault current superimposed on the detected current of the first unbalanced current detecting means, and a second unbalanced current detecting means. A second ground fault current detecting means for detecting a ground fault current superimposed on the detected current with the same polarity as the detected current of the first ground fault current detecting means, a detected current of the second unbalanced current detecting means and a 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, output current of the limiter means, detection current of the first unbalanced current detection means, 1 Detection of ground fault current detection means The first ground fault current by adding flow, respectively
Ground fault current by the detection of the detection means and the second grounding current detection means
An insulation deterioration detecting device comprising an adding means for detecting only the insulation deterioration is constituted.

As a third device, a first unbalanced current detecting means for detecting an unbalanced current flowing in a cable connecting a power supply and a load, and a first unbalanced current detecting means for detecting an unbalanced current flowing in the cable are provided. A second unbalanced current detecting means for detecting with a different polarity, a first ground fault current detecting means for detecting a ground fault current superimposed on the detected current of the first unbalanced current detecting means, and a second unbalanced current detecting means. A second ground fault current detecting means for detecting a ground fault current superimposed on the detected current with the same polarity as the detected current of the first ground fault current detecting means, a detected current of the first unbalanced current detecting means and a 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, output current of the limiter means, detection current of the second unbalanced current detection means, 2 Detection of ground fault current detection means The first ground fault current by adding flow, respectively
Ground fault current detected by the detecting means and the second ground fault current detecting means
An insulation deterioration detecting device comprising an adding means for detecting only the insulation deterioration is constituted.

As a fourth device, a pair of zero-phase current transformers having a coil wound around a three-phase distribution line connecting a power supply and a load, and detecting a zero-phase current from a current flowing through the coil, An adder for adding the output current of each zero-phase current transformer, wherein a ground wire connected to the power supply side jacket of the three-phase distribution line is connected to the coil of each zero-phase current transformer along the three-phase distribution line. is inserted between the envelope of the phase distribution line, the zero-phase inserted ground wire to the current transformer in is grounded at the terminal, is inserted into one of the zero-phase current transformer in the earth wire is a three-phase distribution line The unbalanced current flowing through the three-phase distribution line is wired so that the unbalanced current flowing through the three-phase distribution line and the unbalanced current flowing through the ground line flow in the same direction. Insulation poorly wired so that 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 having a coil wound around a three-phase distribution line connecting a power supply and a load, and detecting a zero-phase current from a current flowing through the coil; A level limiter for limiting the detection current of one zero-phase 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. A ground wire connected to the power supply side jacket of the three-phase distribution line is inserted between the coil of each zero-phase current transformer and the three-phase distribution line sheath along the three-phase distribution line, and inserted ground wire into the flow vessel is grounded at the terminal, one of the inserted ground wire to the zero-phase current transformer in the unbalanced current flowing through the ground line and the unbalanced current flowing through the three-phase distribution line with each other The ground wire that is wired to flow in the same direction and inserted into the other zero-phase current transformer 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 a state of insulation deterioration, an unbalanced current and a ground fault current accompanying the insulation deterioration flow through the cable. The unbalanced current is detected by the first and second unbalanced current detecting means, respectively, and the ground fault current is detected by the first and second unbalanced currents.
Each is detected by the ground fault current detecting means. Then, the detection outputs of the respective detecting means are added by the adding means.
At this time, since the polarity of the detection current of the first unbalanced current detection unit and the polarity of the detection current of the second unbalanced current detection unit are different, the unbalanced currents cancel each other and become zero . On the other hand, since the ground fault currents are both detected with the same polarity, only the current obtained by adding the ground fault currents is output from the adding means. For this reason, the insulation deterioration of the load can be detected with high sensitivity from the output signal of the adding means.

[0011] When the insulation of the cable is deteriorated, an unbalanced current and a ground fault current accompanying the insulation deterioration flow through the cable. The unbalanced current is detected by the first and second unbalanced current detectors, and the ground fault current is detected by the first and second ground fault current detectors, respectively. The detection current of one 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 is obtained. The sum is added by the adding means in a state where the sum is limited to a level equal to or less than the unbalanced current. Since the unbalanced currents detected by the unbalanced current detection means have different polarities, only the ground fault current is output from the addition means. For this reason, it can be detected with high sensitivity that the cable is in the insulation deterioration state.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the power transformer 10 is a power receiving circuit breaker 1.
2 is connected to the power supply side bus 14. A grounding system transformer 16 is connected to the power supply side bus 14 and a limiting resistor 18 for determining an effective grounding current of an ungrounded system.
Is connected. A main circuit cable 24 is connected to the power supply side bus 14 via a power distribution circuit breaker 20 and a power supply terminal 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 an end of the main circuit cable 24.

The ZCTs 26 and 28 are connected to the main circuit cable 24.
And a ground fault current can be detected from a zero-phase current flowing through the terminals C1 and C2 of the comparison / determination unit 32.
2, C3, and C4. Each ZCT2
Resistors 34 and 36 for converting the current on the secondary side into a voltage are connected to the secondary sides of 6, 28. And ZCT2
6, a ground wire 38 connected to the power supply terminal portion 22 is penetrated in the forward direction, and the ground wire 38 is penetrated in the ZCT 28 in the reverse direction. Therefore, ZCT26 and ZCT28
The detection values of the unbalanced current output from the secondary side are detected with opposite polarities. That is, each phase 24A, 24B, 24C of the main circuit cable 24 and the sheath 4
2, there is a ground capacitance C1, C2, C3, so when a current flows through the main circuit cable 24, the current flows through the ground capacitance C1, C2, C3, the sheath 42, and the ground wire 38. Flows. The vector of the current flowing through each phase is represented as shown in FIG. 2, and the sum of the vectors is not completely zero, and an unbalanced current 44 flows through the sheath 42 and the ground wire 38. This unbalanced current appears on the secondary side of ZCT 26 as shown in FIG.
Is output as a waveform as shown in FIG.
On the secondary side 28, a waveform as shown in FIG. 3B is output. Therefore, each ZCT26 and Z
When the unbalanced currents of the CT 28 are added, the respective unbalanced currents are canceled 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 having the same polarity flows on the secondary side of each of the ZCTs 26 and 28. That is, the ZCTs 26 and 28 and the resistors 34 and 36 constitute unbalanced current detecting means and ground fault current detecting means.

The comparison / determination unit 32 includes amplifiers 46 and 48 and an adder 50. The input sides of the amplifiers 46 and 48 are connected to the ZCTs 26 and 28. Amplifier 46
Is the signal output from the secondary side of the ZCT 26 (the resistor 34
For example, a signal accompanying a voltage drop is voltage- amplified, and the amplified signal is output to the adder 50. The amplifier 48 outputs a signal (resistor 3) output from the secondary side of the ZCT 28.
6) is amplified , for example, and the amplified signal is output 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 configuration, when the insulation deterioration occurs in the load 30 and the ground fault current I1 flows through the main circuit cable 24 due to the insulation deterioration, as shown in FIG. Unbalanced current 26A, 2 of ZCT26 output
8A. Then, synthesized 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 equal to the ground fault current I.
Since it has the same polarity as 1, the composite value of these currents is the signal 46A. On the other hand, unbalanced current 28A of ZCT28 output
Since the polarity of the ground fault current I1 is opposite to the polarity of the ground fault current I1, a signal obtained by combining these currents is a signal 48A. And signal 4
When 6A and the signal 48A are added by the adder 50, the adder 50 outputs a signal 50A equal to twice the ground fault current I1. That is, the ZCTs 26 and 28 are
Are penetrated in opposite directions, so that ZCT 26,2
The polarity of the unbalanced current due to the detection of the 8 reverse and ing each other. This
For, when it is <br/> synthesized by the adder 50 the output signal of each ZCT26,28 unbalanced currents cancel each other, 0 and I
You. On the other hand, ground fault by detection of ZCT26,28
Since the currents have the same polarity, the ZCTs 26 and 28
When the adder 50 adds the ground fault current due to the detection of
Only the ground fault current I1 based on the detection at T26 and T28 can be detected. Moreover, since a current equal to twice the ground fault current can be detected, a current accompanying the insulation deterioration of the load 30 can be detected with high sensitivity.

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

In the above configuration, when the main circuit cable 24 enters the insulation deterioration state and a ground fault current I2 accompanying the insulation deterioration flows through the main circuit cable 24, the ground fault current I2 becomes unbalanced currents 26A and 28A. Superimposed on each other, amplifier 4
6, 48 from the signal 46A, 4
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 by the limiter 52 to the level of the unbalanced current or less, and is output as the signal 52A. That is, the signal 52A obtained by removing the component of the ground fault current I2 from the unbalanced current is input to the adder 50. The signal 46A and the signal 52A are added in the adder 50.
Is added, adder 50 can output signal 50A including only ground fault current I2. For this reason, according to this 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.

In the above embodiment, the limiter 52
Has been described between the amplifier 48 and the adder 50. However, 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, the main circuit cable 24 is
Can be detected with high sensitivity.

When installing the ZCTs 26 and 28, the comparator 32 and the like in the above embodiment, as shown in FIG.
The CTs 26 and 28 are housed, and the comparison / determination unit 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 the detection unit 5
6 to the main circuit cable 24. Further ground wire 38
Is connected to the ground bus 62, and the secondary side of each of the ZCTs 26 and 28 is connected to the comparison / determination unit 32 via the shield line 64.
By adopting such an arrangement and connection configuration, each unit can be arranged rationally and standardization of the assembling work becomes possible. Further, malfunction due to noise can be prevented. Note that metal walls 70 and 72 are provided between the power receiving circuit breaker room 66, the power supply cable room 68, and the load side main circuit cable processing room 60, respectively.
The surroundings of the power distribution circuit breaker room 74 and the bus bar room 76 are separated by metal walls 78, 80, and 82. A power lead-in cable 84 is connected to a disconnecting portion 88 via a conductor 86. The disconnecting section 90 is connected to the buses 3R, 3S, 3T. The disconnecting portion 92 is connected to the bus 3T, and the disconnecting portion 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 detecting means for detecting both the unbalanced current and the ground fault current flowing through the cable,
The unbalanced currents are detected by the detection means in opposite polarities and the ground fault currents are detected in the same polarity, and only the current accompanying the cable insulation deterioration and the load insulation deterioration is detected. In addition, it is possible to detect the insulation deterioration of the load with high sensitivity.

[Brief description of the 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 chart for explaining a method for removing a cable unbalanced current.

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

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

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

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Power supply transformer 12 Power receiving circuit breaker 14 Power supply side bus 20 Power distribution circuit breaker 22 Power supply terminal part 24 Main circuit cable 26,28 ZCT 30 Load 32 Comparing and judging device 34,36 Resistance 46,48 Amplifier 50 Adder 52 Limiter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironobu Abe 3-7-1, Ichibancho, Aoba-ku, Sendai, Miyagi Prefecture Tohoku Electric Power Co., Inc. (72) Inventor Osamu Funayama 5-chome, Miyagino-ku, Sendai, Miyagi Prefecture 2-1 Tohoku Electric Power Co., Inc. Shin-Sendai Thermal Power Station (72) Inventor Yoji Sasaki Hachinohe-shi, Aomori prefecture Shigasaki-machi, Shigahama-machi, Maejima 1 Tohoku Electric Power Co., Inc.Sendai Thermal Power Station 217-6 Shimokawabata, Kodo, Tohoku Electric Power Company Akita Thermal Power Station (72) Inventor Shigemitsu Mori Sendai, Miyagi 5-2-1, Minato, Miyagino-ku, Tohoku Electric Power Co., Inc.Shin-Sendai Thermal Power Station 72) Inventor Yoshinori Ito 3-7-1, Ichibancho, Aoba-ku, Sendai, Miyagi Tohoku Electric Power Co., Inc. (72) Inventor Akira Akiyama 3-7-1, Ichibancho, Aoba-ku, Sendai, Miyagi Tohoku Electric Power (72) Inventor Kazushi Ono 3-7-1, Ichibancho, Aoba-ku, Sendai, Miyagi Prefecture Tohoku Electric Power Co., Inc.

Claims (5)

(57) [Claims] 1. An unbalanced current detecting means for detecting an unbalanced current flowing in a cable connecting a power supply and a load, and an unbalanced current flowing in the cable is detected with a polarity different from that of the first unbalanced current detecting means. A second unbalanced current detecting means, a first ground fault current detecting means for detecting a ground fault current superimposed on the detected current of the first unbalanced current detecting means, and a superimposed current detected by the second unbalanced current detecting means. Second ground fault current detecting means for detecting the detected ground fault current with the same polarity as the detected current of the first ground fault current detecting means, detection current of the first unbalanced current detecting means and detection of the first ground fault current detecting means The current, the detected current of the second unbalanced current detecting means, and the detected current of the second ground fault current detecting means are respectively added to the first ground fault current detecting means and the second ground fault current detecting means.
An insulation deterioration detection device comprising: an addition unit that detects only a ground fault current based on the detection of a fault . 2. An 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 is detected with a polarity different from that of the first unbalanced current detecting means. A second unbalanced current detecting means, a first ground fault current detecting means for detecting a ground fault current superimposed on the detected current of the first unbalanced current detecting means, and a superimposed current detected by the second unbalanced current detecting means. Second ground fault current detection means for detecting the detected 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 current added to the current to the level of the detection current of the second unbalanced current detection means, output current of the limiter means, detection current of the first unbalanced current detection means, and first ground fault current Add the detection current of the detection means The first ground fault current detection means and the second ground fault current
An insulation deterioration detection device comprising: an addition unit that detects only a ground fault current detected by a short-circuit current detection unit. 3. An 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 is detected with a polarity different from that of the first unbalanced current detecting means. A second unbalanced current detecting means, a first ground fault current detecting means for detecting a ground fault current superimposed on the detected current of the first unbalanced current detecting means, and a superimposed current detected by the second unbalanced current detecting means. Second ground fault current detecting means for detecting the detected ground fault current with the same polarity as the detected current of the first ground fault current detecting means, detection current of the first unbalanced current detecting means and detection of the first ground fault current detecting means Limiter means for limiting the level of the current added to the current to the level of the detection current of the first unbalanced current detection means, output current of the limiter means, detection current of the second unbalanced current detection means, and second ground fault current Add the detection current of the detection means The first ground fault current detection means and the second ground fault current
An insulation deterioration detection device comprising: an addition unit that detects only a ground fault current detected by a short-circuit current detection unit. 4. A pair of zero-phase current transformers having a coil wound around a three-phase distribution line connecting a power supply and a load, and detecting a zero-phase current from a current flowing through the coil, An adder for adding the output current of the current transformer, wherein a ground wire connected to the power supply side jacket of the three-phase distribution line is connected to the coils of each zero-phase current transformer and the outside of the three-phase distribution line along the three-phase distribution line. is inserted between the human, the ground wire inserted into the ZCT in is grounded at the terminal, one of the inserted ground wire to the zero-phase current transformer in the unbalance through the three-phase distribution line The current and the unbalanced current flowing through this ground wire are wired so as to flow in the same direction as each other, and the ground wire inserted in the other zero-phase current transformer flows through this three-phase distribution line with the unbalanced current flowing through this ground wire. An insulation deterioration detection device wired so that unbalanced currents flow in opposite directions. 5. A pair of zero-phase current transformers having a coil wound around a three-phase distribution line connecting a power supply and a load, and detecting a zero-phase current from a current flowing through the coil, and one of the zero-phase current transformers A level limiter for limiting the current detected by the current transformer to a level equal to or less than the level of the unbalanced current; and an adder for adding the output current of the other zero-phase current transformer and the output current of the level limiter. is inserted between the ground lines connected to the power supply side outer phase distribution line is the outer coil and the three-phase distribution line of the ZCT along a three-phase distribution line, in each ZCT The inserted ground wire is grounded at its end, 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. And the ground wire inserted in the other zero-phase current transformer does not flow through the three-phase distribution line. An insulation deterioration detection device wired so that a balanced current and an unbalanced current flowing through the ground wire flow in opposite directions.