JP6069051B2 - Power cable high resistance insulation failure location method and apparatus - Google Patents

Description

  The present invention relates to a method and an apparatus that can determine the position of an insulation failure location with high accuracy even if the insulation failure location in a power cable has a high resistance.

2. Description of the Related Art Conventionally, an insulation failure location locating device in a power cable has been developed for the purpose of locating an insulation failure location in a power cable having an insulation failure location (hereinafter referred to as “accident occurrence cable”).
As shown in FIG. 5, a conceptual diagram of the poor insulation location locating device is as follows. (Referred to as a “sound cable”) in parallel with one end of the conductor of the conductor, and a DC voltage source for positioning between the ground contact and the sliding contact that can change the apportioning position of the measuring side resistance. The other end of the conductor of the accident occurrence cable and the other end of the conductor of the sound cable are connected by a short-circuit wire, and the shielding layer of the accident occurrence cable is grounded.

  An equivalent circuit of the device for locating the position of the insulation failure point (Fp) is a bridge circuit shown in FIG. In this figure, E is the voltage of the DC voltage source for orientation, L is the length from one end to the other end of the accident occurrence cable and the sound cable, l is the length from one end of the accident occurrence cable to the location of poor insulation, and Ra is Rb is the resistance value closer to the sound cable than the sliding contact of the measurement side resistance, Rb is the resistance value closer to the cable where the accident occurred than the sliding contact of the measurement side resistance, and Rc is the conductor and short-circuit line from one end of the healthy cable to the location of poor insulation The resistance value, Rd is the resistance value of the conductor from one end of the cable where the accident occurred to the poor insulation location, Re is the resistance value of the poor insulation location (hereinafter referred to as “ground fault resistance”), and Rg is the internal resistance of the galvanometer meter. The value Ro is a symbol indicating the internal resistance value of the DC voltage source for orientation.

In this equivalent circuit, when the apportioning position of the measurement side resistance is changed by moving the sliding contact of the measurement side resistance and the current flowing through the galvanometer meter is adjusted to zero, Ra × Rd = Rb × Rc is established.
Here, when the resistance value per unit length of the conductor of the healthy cable and the cable having the accident occurrence is ρ, Rc = ρ × (2L−1) and Rd = ρ × l , so Ra × Rd = Rb × Substituting these relationships into Rc and rearranging results in l = L × 2 × Rb / (Ra + Rb).
L is a value that can be obtained by measuring the length from one end to the other end of the accident-occurring cable or the healthy cable, Rb is a value that can be obtained from the prorated position of the measured side resistance, and Ra + Rb is a constant value. The length from one end of the cable where the accident occurred to the insulation failure location is known, and the location of the insulation failure location (Fp) can be determined.

However, when the ground fault resistance (Re) is high, the voltage drop at the ground fault resistance (Re) increases in the bridge circuit of FIG. 6 and the conductor resistance of the power cable is low (0.02 to 0.08 Ω / km), the potential difference between both ends of the galvanometer meter (G) becomes very small, and it is impossible to determine the location of the insulation failure. For this reason, conventionally, when the ground fault resistance is high, the insulation failure location is reduced to a low resistance by firing by high voltage application.
In many cases, high-resistance insulation failures occur at the ends and connections of power cables. When firing by high-voltage power, the fired power cables may be damaged. For this reason, the power cable itself was replaced after standardization even though there was no defective insulation in the power cable itself.

Therefore, as described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-267002), in order to avoid firing due to high voltage application, the detection sensitivity of the conventional orientation device is greatly improved, and the orientation range is increased by 10 times. A new type of orientation device has been developed. According to this orientation apparatus, when the cross-sectional area of the cable conductor is 150 mm ² (diameter 13.8 mm), and the length of the power cable to be measured (hereinafter referred to as “cross length”) is 1000 m, the ground fault resistance is 200 MΩ. If it is to the extent, the position of the insulation failure location can be determined.
However, recently the cross-sectional area of the cable conductor with the capacity of transmission capacity is larger, 325 mm ² (diameter 20.3 mm), more so is used as a 725 mm ² (diameter 30.4 mm) Therefore, the ground fault resistance that can be determined is proportional to the resistance value per unit length of the cable conductor and the length of the cable conductor, and the length at the time of standardization in the field may be about 100 m. Even if the apparatus is used, the ground fault resistance that can be determined is 20 MΩ (200 MΩ × 0.1) when the cross-sectional area is 150 mm ² and the total length is 100 m, 9.2 MΩ (200 MΩ × when the cross-sectional area is 325 mm ² and the total length is 100 m. 150 ÷ 325 × 0.1), and when the cross-sectional area is 725 mm ² and the span length is 100 m, it is only 4.1 MΩ (200 MΩ × 150 ÷ 725 × 0.1).
And since the ground fault resistance is often about 200 MΩ, it is possible to increase the location ability from 100 times to 500 times that of a normal orientation device (10 times to 50 times that of a new orientation device). Is strongly demanded in the field.

JP 2006-267002 A

  It is an object of the present invention to be able to determine an insulation failure location without firing the power cable even if the span is short, and to be able to identify the insulation failure location without firing the power cable even if the cable size is large. And making the orientation error as small as possible.

In the power cable high resistance insulation failure location method according to the first aspect of the invention, the galvanometer meter and the measurement side resistance are arranged in parallel between one end of the shielding layer of the accident cable and one end of the shielding layer of the sound cable. Connecting, applying a DC voltage for orientation between a predetermined contact of the measurement side resistance including a variable resistance in part or a sliding contact capable of changing a prorated position of the measurement side resistance and the grounding point, the other end of the shielding layer of the other end and the healthy cable shielding layer of accident cable connected by short-circuit line, around the one end near to the connection point of the galvanometer meter and the measurement side resistance in the accident cable, A conductive first high-voltage guard insulated from the conductor and shielding layer of the accident occurrence cable is disposed, and the conductor of the accident occurrence cable is arranged around the other end side of the connection point of the short circuit line in the accident occurrence cable. as well as A conductive second high-voltage guard insulated from the shielding layer is disposed, the first high-voltage guard and the second high-voltage guard are electrically connected, and the orientation DC is connected to the first high-voltage guard and the second high-voltage guard. Apply a DC voltage of about the same voltage, and ground the conductor of the cable where the accident occurred to form a bridge circuit, change the resistance value of a part of the measurement side resistance, or change the prorated position of the measurement side resistance The current flowing through the galvanometer meter is adjusted to zero, and the position of the insulation failure location of the power cable is determined based on the partial resistance value of the measurement side resistance or the prorated position of the measurement side resistance. It is characterized by that.

The power cable high resistance insulation failure location determination method of the invention according to claim 2 is the power cable high resistance insulation failure location determination method according to claim 1, wherein the galvanometer meter and the measurement side resistance in the accident occurrence cable are connected. A conductive third high-voltage guard insulated from the conductor and shielding layer of the accident occurrence cable is disposed around the other end side vicinity of the point, and the vicinity of one end side of the connection point of the short-circuit line in the accident occurrence cable is arranged. A conductive fourth high-voltage guard insulated from the conductor and shielding layer of the accident cable is arranged around the periphery, and the vicinity of the other end side with respect to the connection point of the galvanometer meter and the measurement side resistance in the healthy cable A conductive fifth high-voltage guard insulated from the conductor and shielding layer of the healthy cable, and one end side with respect to the connection point of the short-circuit line in the healthy cable A conductive sixth high voltage guard insulated from the conductor and shielding layer of the sound cable is disposed around the side, and the first high voltage guard to the sixth high voltage guard are electrically connected, and the first A DC voltage of about the DC voltage for orientation is applied to one high voltage guard or the sixth high voltage guard .

A power cable high resistance insulation failure location determination method according to claim 3 is the power cable high resistance insulation failure location determination method according to claim 1 or 2, wherein the orientation DC voltage is connected to the power cable. The voltage is equal to or lower than the allowable DC voltage value of the switchgear, and is superimposed on the power cable between the galvanometer meter and one end of the shielding layer of the accident cable and one end of the shielding layer of the sound cable. A noise prevention circuit for preventing noise from being input to the galvanometer meter is connected .

A power cable high resistance insulation failure location device of the invention according to claim 4 includes a galvanometer meter and a measurement side connected in parallel between one end of the shielding layer of the accident cable and one end of the shielding layer of the sound cable. Resistance, a predetermined contact of a measurement side resistance including a variable resistance in part, or a sliding contact capable of changing a prorated position of the measurement side resistance, between the predetermined contact or the sliding contact and a ground point DC voltage source for orientation to apply DC voltage for orientation, short-circuit line connecting the other end of the shielding layer of the accident cable and the other end of the shielding layer of the sound cable, a galvanometer meter and measurement in the accident cable A conductive first high voltage guard disposed around one end side of the connection point of the side resistance and insulated from the conductor and shielding layer of the accident occurrence cable, and to the connection point of the short circuit line in the accident occurrence cable The conductive second high-voltage guard, the first high-voltage guard, and the second high-voltage guard are electrically connected to each other around the other end side so as to be insulated from the conductor and the shielding layer of the accident occurrence cable. A connection line, a DC voltage source for applying a DC voltage about the DC voltage for orientation to the first high voltage guard and the second high voltage guard, and a ground line for connecting the conductor of the accident occurrence cable and a grounding point. Features.

The power cable high resistance insulation failure location determination device according to claim 5 is the power cable high resistance insulation failure location determination device according to claim 4 , wherein the galvanometer meter and the measurement side resistance in the accident occurrence cable are connected. A conductive third high-voltage guard arranged around the other end side of the point and insulated from the conductor and shielding layer of the accident occurrence cable, near one end side of the connection point of the short-circuit line in the accident occurrence cable Around the other end side of the connection point of the conductive galvanometer meter and the measurement side resistance in the sound cable, the conductive fourth high-voltage guard arranged insulated from the conductor and the shielding layer of the accident cable In addition, the conductive fifth high-voltage guard arranged insulated from the conductor and shielding layer of the healthy cable, with respect to the connection point of the short-circuit line in the healthy cable A conductive sixth high-voltage guard, the first high-voltage guard, and the sixth high-voltage guard are electrically connected to each other in the vicinity of the end side so as to be insulated from the conductor and shielding layer of the sound cable. And a DC voltage source for applying a DC voltage about the orientation DC voltage to the wire and the first high voltage guard to the sixth high voltage guard .

A power cable high resistance insulation failure location determination device according to claim 6 is the power cable high resistance insulation failure location determination device according to claim 4 or 5 , wherein the galvanometer meter and the measurement side resistance are arranged. An electrically conductive seventh high-voltage guard, the first high-voltage guard, and the seventh high-voltage guard are electrically insulated from an insulating material such as an insulating rod that insulates and supports the substrate from the ground. And a direct-current voltage source for applying a direct-current voltage about the orientation direct-current voltage to the first high-voltage guard and the seventh high-voltage guard .

Power cable high resistance insulating defective portion locating system of the invention according to claim 7, in the power cable high resistance insulating defective portion locating system according to claim 4, wherein the galvanometer meter and the accident cable A noise intrusion prevention circuit that is connected between one end of the shielding layer and one end of the shielding layer of the sound cable and prevents noise superimposed on the power cable from being input to the galvanometer meter. Features.

According to the invention of claim 1 or 4, it is not necessary to perform the firing of a power cable, even for long route length has a occurred rated Another problem.
In addition, one end of the shielding layer of the accident occurrence cable to which the galvanometer meter and the measuring side resistance are connected, the conductor of the accident occurrence cable, the other end of the shielding layer of the accident occurrence cable to which the short-circuit wire is connected, and the accident occurrence cable Since the conductors are close to each other, it is possible to eliminate the influence of the creeping leakage current, so that it is possible to reduce an orientation error when locating the location of the insulation failure location.

According to the invention of claim 2, 5 or 6 , in addition to the effect of the invention of claim 1 or 4, it is possible to eliminate the influence of creeping leakage current that propagates on the outer surface of the sheath . There is an effect that an orientation error in locating the position can be further reduced.
And the effect by the invention which concerns on Claim 1, 2, 4, 5 or 6 is especially important when taking a long length.

According to the invention according to claim 3 or 7 , in addition to the effect of the invention according to claim 1, 2 or 4-6, when the cross-sectional area of the cable conductor is 325 mm ² , the resistance value of the cable conductor is 0.0579Ω. The resistance value of the shielding layer is 1.71 Ω / km, which is 29.5 times higher than that of / km, so that the ground fault resistance that can be determined is 29.5 times, that is, even when the span length is 100 m. When the cross-sectional area of the cable conductor is 725 mm ² , the resistance value of the cable conductor is 0.026 Ω / km, whereas the resistance value of the shielding layer is 1 (271.4 MΩ (9.2 MΩ × 29.5)). .26Ω / km, which is 48.5 times higher, the ground fault resistance that can be determined is 48.5 times, that is, 198.9 MΩ (4.1 MΩ × 48.5) even when the span is 100 m, It can satisfy the demands of the site.

According to the inventions according to claims 1 to 7 , since the position of the insulation failure location can be determined without firing by high voltage application even when the ground fault resistance is high, only the insulation failure location is replaced. Therefore, the cost required for recovery can be reduced.
In particular, if insulation failure has occurred at the terminal or connection part of the power cable as a result of the orientation, it can be recovered by replacing only the terminal part or connection part, and the cable body need not be replaced. Recovery time and cost required for recovery can be greatly reduced.
In addition, the device (measurement side resistance) that is operated when locating defective insulation locations is standardized using the same method as used so far, making it easy for workers to get used to and know-how accumulated through previous experience. There is also an advantage of being able to make use of it.

The conceptual diagram of the electric power cable high resistance insulation defect location apparatus of Example 1. FIG. Sectional drawing of an electric power cable. The conceptual diagram of the electric power cable high resistance insulation defect location apparatus of Example 2. FIG. The conceptual diagram of the power cable high resistance insulation defect location apparatus of a reference example. The conceptual diagram of the apparatus which pinpoints an insulation defect location. Equivalent circuit for equipment that locates defective insulation.

  Hereinafter, embodiments of the present invention will be described by way of examples.

[Example 1]
The conceptual diagram of the power cable high resistance insulation defect location apparatus of Example 1 is shown in FIG.
The cross-sectional view of the power cable to be standardized in Example 1 has a structure as shown in FIG. 2, and in order from the center, the conductor 4, the insulator 5 such as cross-linked polyethylene, the shielding layer 6 wound with copper tape, The sheath 7 is made of a water shielding tape layer or a vinyl coating layer.
In the first embodiment, the galvanometer meter 8 and the measurement side resistance 9 are connected in parallel between one end of the shielding layer 6 of the accident occurrence cable 1 and one end of the shielding layer 26 of the first sound cable 2, An orientation DC voltage source 11 is connected between the sliding contact 10 capable of changing the prorated position of the measurement side resistor 9 and the grounding point.
In addition, the other end of the shielding layer 6 and the other end of the shielding layer 26 are connected by a short-circuit wire 12, and the other end of the conductor 4 of the accident occurrence cable 1 is grounded to form a bridge circuit.

In the case of the connection state of Example 1, one end of the shielding layer 6 and one end of the conductor 4 to which the galvanometer meter 8 and the measurement side resistance 9 are connected, and the other end and conductor of the shielding layer 6 to which the short-circuit wire 12 is connected. Since the other end of 4 is close and the conductor 4 is grounded, a creeping leakage current may occur between them, which may cause an error in the orientation result. Further, the creeping surface that travels on the outer surface of the sheath 7 Leakage current may be generated and an error may be caused in the orientation result.
Therefore, in the first embodiment, the conductor 4 and the shielding layer 6 are disposed so as to be insulated in the vicinity of one end side from the point where the galvanometer meter 8 and the measurement side resistance 9 of the shielding layer 6 are connected. A conductive second high-voltage guard 14 and a second conductive second disposed around the other end of the shield layer 6 near the point where the short-circuit line 12 is connected and insulated from the conductor 4 and the shield layer 6. The conductor 4 and the shielding layer 6 are disposed around the sheath 7 in the vicinity of the other end side from the point where the high voltage guard 15, the galvanometer meter 8 of the shielding layer 6 and the measurement side resistance 9 are connected. The conductive third high voltage guard 16 and the conductor 4 and the shielding layer 6 are arranged around the sheath 7 near one end from the point where the shorting line 12 of the shielding layer 6 is connected. The fourth high voltage guard 17, the galvanometer meter 8 of the shielding layer 26 and the measurement side resistance 9 are connected. Also, around the sheath 27 near the other end side, the conductive fifth high voltage guard 18 disposed so as to be insulated from the shielding layer 6 and the point near the one end side from the point where the short-circuit line 12 of the shielding layer 26 is connected. Around the sheath 7, a conductive sixth high-voltage guard 19 disposed so as to be insulated from the shielding layer 26 and a substrate 28 on which the galvanometer meter 8 and the measurement side resistor 9 are disposed are insulated and supported from the ground. A conductive seventh high-voltage guard 30 disposed so as to be insulated from the substrate 28 and the ground is disposed around the insulating rod 29, and the first to seventh high-voltage guards 14 to 19 and 30 are interconnected. While being electrically connected, a voltage of about the DC voltage for orientation is applied to them.
More specifically, the first high pressure guard 14 and the third high pressure guard 16, the second high pressure guard 15 and the fourth high pressure guard 17, the third high pressure guard 16 and the fifth high pressure guard 18, the fourth high pressure guard 17 and the sixth high pressure guard 17. One end of the conductor 34 of the high voltage guard 19, the fifth high voltage guard 18 and the second sound cable 3, the fifth high voltage guard 14 and the sliding contact 10, the sixth high voltage guard 19 and the other end of the conductor 34, the seventh high voltage guard 30 And the sliding contact 10 are electrically connected to each other by an interconnection line, so that a voltage substantially equal to the DC voltage E for orientation is applied to the first to seventh high voltage guards 14 to 19 and 30.

When the position of the insulation failure location is determined by the power cable high resistance insulation failure location device of Example 1, the sliding contact 10 of the measurement side resistance 9 is operated and distributed as in the case of the location by the conventional device. The position is changed and the current flowing through the galvanometer meter 8 is adjusted to zero. The resistance value on the accident cable 1 side or the prorated position in the measurement side resistance 9 is read from the sliding contact 10 of the measurement side resistance 9 at that time.
The equivalent circuit of the first embodiment is not different from the equivalent circuit in the conventional apparatus except that Rc and Rd are different. Therefore, as described in the background section above, l = L × 2 × Rb / By calculating (Ra + Rb), it is possible to know l, that is, the length from one end of the fault occurrence cable 1 to the insulation failure location Fp, and the position of the insulation failure location Fp can be determined.

[Example 2]
The conceptual diagram of the power cable high resistance insulation defect location apparatus of Example 2 is shown in FIG.
Example 2 is the same as Example 1 shown in FIG. 1 except that the galvanometer 8 is not directly connected to one end of the shielding layer 6 and one end of the shielding layer 26 and an auxiliary device is added. The basic configuration is the same as that of the power cable high resistance insulation failure location determination device.
The difference from the first embodiment is that the noise intrusion prevention circuit 20 is connected in parallel with the measurement side resistance 9 between one end of the shielding layer 6 and one end of the shielding layer 26, and the galvanometer 8. Is connected to the noise intrusion prevention circuit 20, the position where the sliding contact 10 apportions the measurement side resistance 9 is detected, and the ratio calculating unit 21 and the apportioning ratio indicator 22 for calculating and displaying the apportioning ratio. And a battery 23 for supplying power to the noise intrusion prevention circuit 20 and the ratio calculation unit 21.
The specific difference between Example 1 and Example 2 is described in FIG. 1, FIG. 2, paragraphs 0019 to 0028, and paragraphs 0035 to 0037 of Patent Document 1 (Japanese Patent Laid-Open No. 2006-267002). Although not described in detail, the following measures are taken so that the position of the insulation failure location can be determined with high sensitivity.

(1) The voltage of the DC voltage source for orientation 11 is set to be equal to or lower than the allowable DC voltage value of the switchgear connected to the power cable, and a DC stabilized power source having a low internal resistance is adopted.
(2) The noise intrusion prevention circuit 20 is provided to prevent noise superimposed on the power cable from being input to the galvanometer meter 8.
(3) Improve the insulation performance of the noise intrusion prevention circuit 20, the galvanometer meter 8, the sliding contact 10, the ratio calculation unit 21, the proportional distribution indicator 22, the battery 23, etc., and the galvanometer meter 8 and the sliding The insulation performance of the operation part (operation switch, operation dial, operation knob, etc.) of the contact 10 is improved, and the leakage current is reduced while maintaining a predetermined insulation strength with the grounding point.

  Among these, the minimum configuration necessary for locating a poorly insulated portion with high sensitivity is that the voltage of the locating DC voltage source 11 is less than or equal to the allowable DC voltage value of the switchgear connected to the power cable, and noise intrusion. The prevention circuit 20 is provided to prevent noise superimposed on the power cable from being input to the galvanometer meter 8.

The operation for locating the insulation failure location by the power cable high resistance insulation failure location method and apparatus of the second embodiment is exactly the same as that of the first embodiment.
In the second embodiment, since the proportional distribution ratio indicator 22 displays the proportional ratio of the measured side resistance 9, that is, 2 × Rb / (Ra + Rb), only the calculation of L × proportional ratio results in l, that is, the cable where the accident occurred. The length from one end of 1 to the defective insulation point Fp is known, and the position of the defective insulation point Fp can be easily determined.

[Reference example]
In the first and second embodiments, the galvanometer meter 8 and the measurement side resistance 9 are connected in parallel between one end of the shielding layer 6 of the accident occurrence cable 1 and one end of the shielding layer 26 of the first sound cable 2. In addition, the other end of the shielding layer 6 and the other end of the shielding layer 26 are connected by a short-circuit wire 12, and the other end of the conductor 4 of the accident cable 1 is grounded to form a bridge circuit. In the conductor voltage application system, a power cable high resistance insulation failure location system that can eliminate the influence of creeping leakage current that is likely to occur can also be configured by providing a plurality of high voltage guards.

FIG. 4 is a conceptual diagram of a power cable high resistance insulation failure location apparatus according to a conductor voltage application method of a reference example.
This power cable high resistance insulation fault location device has a galvanometer meter 8 and a measurement side resistor 9 connected in parallel between one end of the conductor 4 of the accident cable 1 and one end of the conductor 24 of the sound cable 2. A predetermined contact of the measurement side resistance 9 including a variable resistance in part or a sliding contact 10 capable of changing a prorated position of the measurement side resistance 9, a predetermined contact or between the sliding contact 10 and the grounding point DC power source 11 for orientation that applies DC voltage E for orientation, short-circuit wire 12 that connects the other end of conductor 4 of accident occurrence cable 1 and the other end of conductor 24 of sound cable 2, and shielding layer of accident occurrence cable 1 6 and a grounding wire 33 for connecting the grounding point, the conductor 4 of the accident occurrence cable 1 and the shield around the other end side of the accident occurrence cable 1 with respect to the connection point of the galvanometer meter 8 and the measurement side resistance 9. Insulated from layer 6 The conductive first high-voltage guard 14 and the conductor 4 of the accident cable 1 and the shielding layer 6 are disposed around the vicinity of one end side of the connection point of the short-circuit line 12 in the accident cable 1. Around the insulating rod 29 that insulates and supports the substrate 28 on which the conductive second high-voltage guard 15, the galvanometer meter 8, and the measurement side resistor 9 are disposed, and is insulated from the ground, the substrate 28 and the ground are disposed. Conductive seventh high-voltage guard 30, insulation of conductor 24 and shielding layer 26 of sound cable 2 around the other end side with respect to the connection point of galvanometer meter 8 and measurement side resistance 9 in sound cable 2 The conductive eighth high-voltage guard 31 and the conductor 24 of the healthy cable 2 and the shielding layer 26 are insulated and arranged around the vicinity of one end side of the connection point of the short-circuit wire 12 in the healthy cable 2. The electrically conductive ninth high voltage guard 32 is disposed, and the first high voltage guard 14, the second high voltage guard 15, the seventh high voltage guard 30, the eighth high voltage guard 31, and the ninth high voltage guard 32 are electrically connected by an interconnection line. And a voltage of about the DC voltage for orientation is applied to them.
More specifically, the first high-pressure guard 14 and the eighth high-pressure guard 31, the second high-pressure guard 15 and the ninth high-pressure guard 32, the eighth high-pressure guard 31 and one end of the conductor 34 of the second healthy cable 3, the ninth By electrically connecting the high voltage guard 32 and the other end of the conductor 34, and the seventh high voltage guard 30 and the sliding contact 10 with respective interconnection lines, the first high voltage guard 14, the second high voltage guard 15, and the seventh high voltage guard. The guard 30, the eighth high-voltage guard 31, and the ninth high-voltage guard 32 are applied with substantially the same voltage as the orientation DC voltage E.

When the location of the insulation failure location is determined by the power cable high resistance insulation failure location device of the reference example, the sliding contact 10 of the measurement side resistance 9 is operated as in the case of the location according to Examples 1 and 2. The apportioning position is changed, and the current flowing through the galvanometer meter 8 is adjusted to zero. The resistance value on the accident cable 1 side or the prorated position in the measurement side resistance 9 is read from the sliding contact 10 of the measurement side resistance 9 at that time.
Then, as described in the background section above, by calculating l = L × 2 × Rb / (Ra + Rb), it is possible to know the length from l, that is, one end of the fault occurrence cable 1 to the insulation failure point Fp, The position of the insulation failure location Fp can be determined.

  According to the power cable high resistance insulation fault location device of the reference example, even though it is a conductor charging method, even if the ground fault resistance is high and the sheath resistance is low, without firing by high voltage charging, Since the location of the insulation failure location can be determined and only the insulation failure location needs to be replaced, the cost required for recovery can be reduced.

  Further, similarly to the second embodiment, the noise intrusion prevention circuit 20 is connected in parallel with the measurement side resistor 9 between one end of the shielding layer 6 and one end of the shielding layer 26, and the galvanometer 8. Is connected to the noise intrusion prevention circuit 20, detects the position where the sliding contact 10 apportions the measurement side resistance 9, calculates the apportioning ratio and displays the apportioning ratio indicator 22, and If the battery 23 for supplying power to the noise intrusion prevention circuit 20 and the ratio calculation unit 21 is provided, the position of the insulation failure location with higher resistance can be determined.

  In the reference example, the first high-pressure guard 14, the second high-pressure guard 15, the seventh high-pressure guard 30, the eighth high-pressure guard 31, and the ninth high-pressure guard 32 are installed. The second high pressure guard 15, the eighth high pressure guard 31, and the ninth high pressure guard 32 are particularly important in order to improve the positioning accuracy.

Examples 1 and 2 and modifications of the reference example are listed.
(1) In the first and second embodiments and the reference example, the sliding contact 10 capable of changing the prorated position of the measurement side resistor 9 is adopted, but the measurement side resistance is composed of the variable resistor Ra and the fixed resistor Rb in series. Or a fixed resistor Ra and a variable resistor Rb may be connected in series, and a contact for applying an orientation DC voltage may be provided between the variable resistor and the fixed resistor.
In that case, Ra or Rb changes, and Ra + Rb also changes at the same time. However, if Ra and Rb can be determined, 2 × Rb / (Ra + Rb) can be calculated, so that l can be obtained.
(2) In Embodiments 1 and 2, one end of the conductor 34 of the fifth high-voltage guard 18 and the second sound cable 3 and the other end of the sixth high-voltage guard 19 and the conductor 34 are electrically connected to each other by an interconnection line. Although connected, the one end of the conductor 24 of the fifth high-voltage guard 18 and the first sound cable 2 and the other end of the sixth high-voltage guard 19 and the conductor 24 may be electrically connected by an interconnection line, The fifth high voltage guard 18 and the sixth high voltage guard 19 may be directly connected by an interconnection line without using the conductor 34 or the conductor 24. However, this is disadvantageous because a separate high-voltage cable is required.
(3) In the first and second embodiments, the galvanometer meter 8 and the measurement side resistance 9 are placed between one end of the shielding layer 6 of the accident occurrence cable 1 and one end of the shielding layer 26 of the first sound cable 2. Although connected in parallel, the first sound cable 2 can be positioned as the conductor 24 instead of the shielding layer 26, although the detectable ground fault resistance is reduced.
(4) In Examples 1 and 2, the fifth high-voltage guard 14 and the sliding contact 10 are connected by an interconnection line, and in the reference example, the eighth high-voltage guard 31 and the sliding contact 10 are connected by an interconnection line. The standard DC voltage source 11 is diverted and the same voltage as the standard DC voltage E is applied. However, the standard DC voltage source 11 is not diverted and can be applied with a voltage equivalent to the standard DC voltage. The DC voltage source and any one of the high-voltage guards may be connected by an interconnection line.
(5) In the second embodiment, the ratio calculator 21 and the proportional ratio indicator 22 that calculate and display the proportional ratio are employed. However, an input unit that can input the length over the ratio calculator 21 is added, and L X2 x Rb / (Ra + Rb) is calculated and displayed position calculation unit and insulation fault location position indicator, you can prevent miscalculation at the time of work, and surely fault insulation location from one end of the cable 1 The length up to Fp can be determined.

DESCRIPTION OF SYMBOLS 1 Accident generation cable 2 1st sound cable 3 2nd sound cable 4, 24, 34 Conductor 5 Insulator 6, 26 Shielding layer 7, 27 Sheath 8 Galvanometer 9 Measurement side resistance 10 Sliding contact 11 For standardization DC voltage source 12 short-circuit line 13, 33 ground line 14 first high-voltage guard 15 second high-voltage guard 16 third high-voltage guard 17 fourth high-voltage guard 18 fifth high-voltage guard 19 sixth high-voltage guard 20 noise intrusion prevention circuit 21 ratio calculation unit 22 Proportion ratio indicator 23 Battery 28 Substrate 29 Insulating rod 30 Seventh high-pressure guard 31 Eighth high-pressure guard 32 Ninth high-pressure guard

Claims (7)

Connect the galvanometer meter and the measurement side resistance in parallel between one end of the shielding layer of the accident cable and one end of the shielding layer of the sound cable,
Apply a DC voltage for orientation between a predetermined contact of the measurement side resistance including a variable resistance or a sliding contact that can change the prorated position of the measurement side resistance and the grounding point,
The other end of the shielding layer of the other end and the healthy cable shielding layer of the accident cable connected by short-circuit line,
A conductive first high-voltage guard insulated from the conductor and shielding layer of the accident occurrence cable is disposed around the vicinity of one end side with respect to the connection point of the galvanometer meter and the measurement side resistance in the accident occurrence cable,
Around the vicinity of the other end side of the connection point of the short-circuit line in the accident occurrence cable, a conductive second high-voltage guard insulated from the conductor and the shielding layer of the accident occurrence cable is disposed,
Electrically connecting the first high pressure guard and the second high pressure guard;
While applying a direct current voltage about the orientation direct current voltage to the first high voltage guard and the second high voltage guard,
Grounding the conductor of the accident occurrence cable to form a bridge circuit,
By changing the resistance value of a part of the measurement side resistance or changing the prorated position of the measurement side resistance, the current flowing through the galvanometer meter is adjusted to zero, and a part of the measurement side resistance is adjusted. A power cable high resistance insulation failure location determination method characterized in that the location of an insulation failure location of a power cable is determined based on a resistance value or an apportioned position of the measurement side resistance.   Around the vicinity of the other end side of the connection point of the galvanometer meter and the measurement side resistance in the accident occurrence cable, a conductive third high voltage guard insulated from the conductor and the shielding layer of the accident occurrence cable is disposed,
  A conductive fourth high-voltage guard insulated from the conductor and the shielding layer of the accident occurrence cable is disposed around the vicinity of one end side of the connection point of the short-circuit line in the accident occurrence cable,
  Around the vicinity of the other end side of the connection point of the galvanometer meter and the measurement side resistance in the sound cable, a conductive fifth high voltage guard insulated from the conductor and the shielding layer of the sound cable is disposed,
  A conductive sixth high-voltage guard insulated from the conductor and shielding layer of the healthy cable is disposed around the vicinity of one end side of the connection point of the short-circuit line in the healthy cable,
  Electrically connecting the first high pressure guard to the sixth high pressure guard;
  A direct current voltage of about the orientation direct current voltage is applied to the first high voltage guard to the sixth high voltage guard.
  The power cable high resistance insulation failure location method according to claim 1. The orientation DC voltage is set to a voltage equal to or lower than an allowable DC voltage value of a switching device connected to the power cable,
Prevents noise superimposed on the power cable from being input to the galvanometer meter between the galvanometer meter and one end of the shielding layer of the accident cable and one end of the shielding layer of the sound cable. A power cable high resistance insulation failure location method according to claim 1 or 2 , wherein a noise prevention circuit is connected. A galvanometer meter and a side resistance connected in parallel between one end of the shield layer of the accident cable and one end of the shield layer of the sound cable;
A predetermined contact of a measuring side resistance including a variable resistance in part or a sliding contact capable of changing a prorated position of the measuring side resistance;
An orientation DC voltage source for applying an orientation DC voltage between the predetermined contact or the sliding contact and a ground point;
A short-circuit wire connecting the other end of the shielding layer of the accident cable and the other end of the shielding layer of the sound cable;
A conductive first high-voltage guard disposed around one end side of a connection point between the galvanometer meter and the measurement side resistance in the accident occurrence cable and insulated from a conductor and a shielding layer of the accident occurrence cable;
A conductive second high-voltage guard disposed around the other end side of the accident occurrence cable in the vicinity of the connection point of the short-circuit line and insulated from the conductor and the shielding layer of the accident occurrence cable;
An interconnection line for electrically connecting the first high voltage guard and the second high voltage guard;
And a DC voltage source for applying a DC voltage of about the DC voltage for orientation to the first high voltage guard and the second high voltage guard,
And a grounding wire for connecting a conductor of the accident cable and a grounding point.   A conductive third high-voltage guard disposed around the other end side of the connection point of the galvanometer meter and the measurement side resistance in the accident occurrence cable, insulated from the conductor and the shielding layer of the accident occurrence cable;
  A conductive fourth high-voltage guard disposed around the one end side near the connection point of the short-circuit line in the accident occurrence cable and insulated from the conductor and the shielding layer of the accident occurrence cable;
  A conductive fifth high-voltage guard disposed around the other end side of the connection point of the galvanometer meter and the measurement side resistance in the sound cable and insulated from the conductor and the shielding layer of the sound cable;
  A conductive sixth high-voltage guard disposed around the one end side of the connection point of the short-circuit line in the healthy cable and insulated from the conductor and the shielding layer of the healthy cable;
  An interconnection line for electrically connecting the first high-voltage guard to the sixth high-voltage guard;
  And a DC voltage source for applying a DC voltage of about the DC voltage for orientation to the first high voltage guard to the sixth high voltage guard.
  The power cable high resistance insulation defect location apparatus according to claim 4.   A conductive seventh high-voltage guard disposed on an insulator such as an insulating rod that insulates and supports the substrate on which the galvanometer meter and the measurement side resistance are disposed from the ground, and is insulated from the substrate;
  An interconnection line for electrically connecting the first high-voltage guard to the seventh high-voltage guard;
  And a DC voltage source for applying a DC voltage on the order of the DC voltage for orientation to the first high voltage guard to the seventh high voltage guard.
  The power cable high resistance insulation defect location device according to claim 4 or 5. The galvanometer meter is connected between one end of the shielding layer of the accident cable and one end of the shielding layer of the sound cable, and noise superimposed on the power cable is input to the galvanometer meter. A power cable high resistance insulation failure location system according to any one of claims 4 to 6, further comprising a noise intrusion prevention circuit for preventing.

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