JP5224825B2 - Insulation monitoring device - Google Patents

Description

The present invention relates to an insulation monitoring device that monitors an insulation state of an electrical device such as a switch gear.

  Conventionally, in order to monitor the insulation state of a switchgear, it is known to connect a through-type current transformer to a ground bus and measure a pulse current due to partial discharge. This is to detect a weak high-frequency pulse current flowing through the ground bus when the circuit breaker housed in the switchgear is deteriorated in insulation (see, for example, Patent Document 1).

In addition, there is known a technique for comparing the magnitude or change of a detected pulse current with a reference characteristic obtained in advance to grasp the progress of insulation deterioration (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 9-5386 (page 3, FIG. 1) JP-A-2005-345216 (pages 3 to 4, FIG. 1)

  The above-described conventional insulation monitoring apparatus has the following problems. Since the pulse current due to the partial discharge is extremely weak, it is easily buried in noise superimposed from the external environment and difficult to detect. For example, in the case where a through-type current transformer is connected to the ground bus, noise such as electromagnetic waves from other electrical devices is superimposed on the main circuit section such as a circuit breaker, and this also flows to the ground bus, thereby detecting partial discharge. It has become difficult. For this reason, although a noise removal circuit or the like is provided to improve detection sensitivity, the partial discharge detection circuit becomes complicated, and it is difficult to easily detect partial discharge.

  In addition, in the comparison between the change with time and the reference characteristics that change with insulation deterioration, the magnitude of noise is random, and it is difficult to accurately determine the change with time of partial discharge. In particular, in the case of a characteristic having a bathtub curve in which the generated partial discharge once decreases and then increases, it is difficult to detect in the decreased period, and there is a possibility of overlooking the generation of the partial discharge. For this reason, it has been desired that the partial discharge can be detected with high sensitivity.

The present invention has been made to solve the above problems, and an object thereof is to provide an insulation monitoring apparatus capable of detecting with high sensitivity partial discharge generated from a switchgear.

To achieve the above object, the insulation monitoring device of the present invention is a switchgear insulation monitor configured by connecting a main circuit device in which a main circuit member is molded with an insulating material and a ground layer is provided on the outer peripheral surface thereof. The main circuit device has an upper connection conductor, a cut-off portion, a disconnection portion, a movable side connection portion, a busbar, and the ground layer is connected to the upper connection conductor, the cut-off portion, the disconnection portion in the main circuit device, It is characterized in that a partial discharge is detected by providing a detection electrode that is separated by an insulating band between each of the movable side connection portion and the bus bar and wound around a metal plate around each ground layer.

  According to the present invention, since the detection electrode for detecting the partial discharge is provided on the outer periphery of the main circuit device in which the ground layer is provided on the outer peripheral surface of the insulating layer, the partial discharge for monitoring the insulation is highly sensitive. Can be detected.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, an insulation monitoring apparatus according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a side view showing an attachment state of an insulation monitoring apparatus according to Embodiment 1 of the present invention.

  The insulation monitoring device is used for an electric device molded with an insulating material such as an epoxy resin. Hereinafter, a solid insulation switchgear will be described as an example.

  As shown in FIG. 1, a cable head 2 is provided on the back side in the box 1, and a power cable 4 penetrating through a through-type current transformer 3 is connected. The cable head 2 has a blocking portion 8 in which an insulating layer 7 is formed by molding a blocking vacuum valve 6 having a pair of contactable and disengageable contacts 5 disposed at the center of the box 1 with an insulating material. The upper connection conductor 9 is connected. The upper connecting conductor 9 is obtained by molding a central conductor with an insulating material.

  On the front side of the box body 1, a disconnecting portion 13 is provided in which an insulating layer 12 is formed by molding a disconnecting vacuum valve 11 having a pair of contactable and separable contacts 10 with an insulating material. The blocking portion 8 and the disconnecting portion 13 are arranged in parallel, and are connected by a movable side connecting portion 16 in which the lower connection conductor 14 is molded with an insulating material to form an insulating layer 15. Further, the disconnecting portion 13 is connected to a bus bar 17 in which a central conductor that is connected to an adjacent board is molded with an insulating material. The upper connecting conductor 9, the blocking portion 8, the disconnecting portion 13, the bus bar 17, and the movable side connecting portion 16 are connected to each other by an interface connecting portion 18 via a flexible insulator (not shown).

  The movable side connection portion 16 is fixed to a gantry 19 having a ground potential, and the movable sides of the vacuum valves 6 and 11 are connected to the operation mechanism 21 via an insulating operation rod 20 provided in the hollow portion. The gantry 19 is a switch gear grounding member, like the box 1 and the like. Further, a ground layer 22 coated with a conductive paint is provided on the outer peripheral surfaces of the upper connecting conductor 9, the blocking portion 8, the disconnecting portion 13, the bus bar 17, and the movable side connecting portion 16. For example, when silver paint is used as the conductive paint, a resistance value of the order of mΩ or less can be obtained.

  Here, the ground layer 22 is not provided in a region where the ground layer 22 is in contact with the gantry 19, and an insulating band 23 having a predetermined width is formed. An outer periphery of the ground layer 22, for example, an outer periphery of the upper connection conductor 9, is provided with a circular detection electrode 24 for detecting a partial discharge current that is wound around a metal plate such as a copper plate and brought into contact with the ground layer 22. It has been. The detection electrode 24 is connected to the detector 26 by a coaxial cable 25. The detector 26 includes a detection means having a high-frequency current transformer, a CR voltage dividing circuit suitable for high-frequency detection, and a circuit such as an amplifier and a filter for specifying a frequency band. A control unit 27 that controls the operation mechanism 21 and the like is provided on the front side.

As a result, the ground layer 22 provided in the main circuit device such as the upper connection conductor 9, the blocking portion 8, the disconnecting portion 13, the bus 17, and the movable side connecting portion 16 is grounded by the detector 26 via the detection electrode 24. Will be. For this reason, the ground capacitance of the main circuit device is several hundred pF, and the pulse current due to the partial discharge generated in the insulating layers 7, 12, and 15 can be detected with high sensitivity. That ensures that the capacitance of a predetermined size between the main circuit member and the detecting electrode 24, such as a vacuum valve 6, 11 is formed, it is possible to detect the partial discharge with high sensitivity.

  Since the insulating band 23 is provided, the detection electrode 24 and the detector 26 are detected from the ground layer 22 rather than the impedance from the ground layer 22 through the mount 19 to the ground electrode serving as the ground of the solid insulation switchgear body. The impedance that reaches the grounding electrode via is small, current attenuation due to partial discharge is suppressed, and the detection sensitivity of the partial discharge is improved by the detector 26. Note that if the detector 26 has a low resistance and the impedance from the detection electrode 24 to the ground electrode is reduced, the insulating band 23 can be omitted.

  Furthermore, since the main circuit member is covered with the insulating layers 7, 12, and 15 and the ground layer 22 is provided on the outer peripheral surface, the main circuit member is shielded by the ground layer 22, and the main circuit member The coupling of external noise to is suppressed. The external noise in a general substation has a discharge charge amount of several thousand pC. However, if it is detected via the ground layer 22, the detection sensitivity can be improved by 1 to 3 digits. For this reason, it is possible to detect a discharge charge amount that contributes to insulation deterioration. In addition, since it is possible to obtain the temporal change of the partial discharge that changes with insulation deterioration, it becomes possible to predict dielectric breakdown.

  The bus bar 17 and the ground layer 22 of the cable head 2 are provided with an insulating band (not shown) in order to cut off the current flowing through the ground layer such as the adjacent panel or the power cable 4. For this reason, the grounding layer 22 becomes independent in the box 1 and is difficult to receive noise intrusion from an adjacent board or the like.

  According to the insulation monitoring apparatus of the first embodiment, main circuit members such as the vacuum valves 6 and 11 are molded with an insulating material, and the ground layer 22 is provided on the outer periphery of the insulating layers 7, 12, and 15. Since the partial discharge is detected by bringing the detection electrode 24 into contact therewith, the impedance from the main circuit member to the detector 26 is small, hardly affected by external noise, and the partial discharge can be detected with high sensitivity.

  In the first embodiment, the insulating band 23 is provided between the ground layer 22 and the gantry 19. However, when the ground layer 22 has a higher resistance than silver paint such as carbon paint, the insulating band 23 is used. Even if the first electrode is not provided, the impedance reaching the ground electrode from the ground layer 22 via the detection electrode 24 is smaller than the impedance reaching the ground electrode from the ground layer 22 via the gantry 19, and the partial discharge. Detection sensitivity can be improved. A ground layer having such resistance is defined as a low resistance ground layer.

  Further, although the detection electrode 24 is provided on the outer periphery of the upper connecting conductor 9, the detection electrode 24 may be provided in other main circuit devices such as the blocking portion 8 and the disconnecting portion 13. In this case, if the detection electrode 24 is provided in the blocking portion 8 and the disconnecting portion 13, a vacuum failure of the vacuum valves 6 and 11 can be detected.

  Next, an insulation monitoring apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 2 is a side view showing an attachment state of the insulation monitoring apparatus according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in that a detector for detecting partial discharge is provided in each main circuit device. In FIG. 2, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 2, detection electrodes 24 are provided in the main circuit devices of the upper connecting conductor 9, the blocking portion 8, the disconnecting portion 13, the movable side connecting portion 16, and the busbar 17, and a detector 26 is connected by a coaxial cable 25. Connected to. Further, an insulating band 23 having a predetermined width is provided between the main circuit devices.

  Thereby, in the main circuit device in which insulation deterioration has occurred, the partial discharge is detected most greatly by the detector 26. Further, since the direction of the pulse current flowing through the detector 26 is opposite to the direction of the pulse current flowing through the detector 26 different from this, the main circuit device in which the partial discharge has occurred can be specified. Furthermore, as the dielectric degradation progresses, the pulse current increases at an accelerated rate with time as shown by the several order curve, leading to dielectric breakdown. For this reason, it is possible to prevent dielectric breakdown in advance by detecting an increase in a several order curve from a monotonous increase proportional to the passage of time, for example.

  According to the insulation monitoring apparatus of the second embodiment, in addition to the effects of the first embodiment, it is possible to identify the main circuit device in which insulation deterioration has progressed.

The side view which shows the attachment state of the insulation monitoring apparatus which concerns on Example 1 of this invention. The side view which shows the attachment state of the insulation monitoring apparatus which concerns on Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Box 2 Cable head 3 Through-type current transformer 4 Electric power cable 5, 10 Contact 6, 11 Vacuum valve 7, 12, 15 Insulating layer 8 Blocking part 9 Upper connection conductor 13 Disconnection part 14 Lower connection conductor 16 Movable side connection part 17 Busbar 18 Interface Connection 19 Base 20 Insulating Operation Rod 21 Operating Mechanism 22 Grounding Layer 23 Insulation Band 24 Electrode for Detection 25 Coaxial Cable 26 Detector 27 Control Unit

Claims (1)

An insulation monitoring device for a switch gear configured by molding a main circuit member with an insulating material and connecting a main circuit device provided with a ground layer on an outer peripheral surface thereof,
The main circuit device has an upper connecting conductor, a blocking portion, a disconnecting portion, a movable side connecting portion, a busbar,
The ground layer is separated by an insulating band between each of the upper connection conductor, the cutoff part, the disconnection part, the movable side connection part, and the bus bar in the main circuit device,
An insulation monitoring apparatus, wherein a partial discharge is detected by providing a detection electrode in which a metal plate is wound around and contacted with each ground layer.

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