KR20160030023A - Method and apparatus for diagnosing insulation degradation in transmission line - Google Patents

Abstract

The present invention relates to a method for diagnosing insulation degradation of a power cable through the whole section of a cross-bonded three-phase transmission line and an insulation diagnosing device thereof. The method comprises the following steps of: synchronizing time of a plurality of insulation degradation diagnosing devices with each other; simultaneously measuring sheath circulating currents in both ends of a power cable; obtaining a charging current from the power cable; obtaining a third high frequency current of the charging current; and analyzing the third high frequency current to determine whether insulation of the power cable is degraded.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for diagnosing an insulation deterioration of a three-phase transmission line and an insulation degradation in the three-

The present invention relates to a method of diagnosing an insulation deterioration of a three-phase transmission line and an insulation deterioration diagnosis apparatus thereof, and more particularly, to a method of diagnosing an insulation deterioration of a three-phase transmission line by detecting three harmonic currents of charging current for each section in a cross- And more particularly, to a method for diagnosing an insulation deterioration of a three-phase transmission line and an insulation deterioration diagnostic apparatus therefor.

Generally, a power cable is used to power a desired location through the ground, ground, or seabed using a power-supplying conductor. It is very important to insulate the conductor from such a power cable. For this purpose, the insulation layer for inserting the conductor may be made of XLPE (Cross-linked Polyethylene) or the like as a raw material.

Meanwhile, the power cable is connected by a joint box at intervals of several hundred meters or tens of km, and the end of the power cable is connected by a termination part.

The electric power cable is deteriorated with the passage of time and the sudden insulation breakdown in the ultra high voltage power cable used in the transmission line lowers the reliability of electric power supply and it is difficult to recover in a short time, do. Therefore, there is a need for a diagnostic technique that can evaluate the deterioration of insulation before the insulation breakdown occurs in the power cable of the transmission line.

In this connection, a method for evaluating the deterioration of an underground transmission line has been developed and U.S. Patent No. 6617859 discloses a method for comparing deterioration of insulation by comparing and analyzing current components measured at two points using an optical current sensor And a method for evaluating the same. U.S. Publication No. 6617859 discloses an optical current sensor that measures current at both ends of a cable and is applicable only to underground transmission lines that are both ends of a grounding system. In a small section of a system crossover grounding system There is a problem that evaluation of insulation deterioration is impossible.

US Registration No. 6617859, "Method for Diagnosing Insulation Degradation in Underground Cables"

The main object of the present invention is to provide a method and an apparatus for diagnosing insulation deterioration diagnosing insulation deterioration over a cross-bonded three-phase transmission line.

A method for diagnosing insulation deterioration of a three-phase transmission line according to an embodiment of the present invention includes diagnosing insulation deterioration of a three-phase transmission line in which metal cables of a power cable are cross- The method comprising: time synchronization of a plurality of insulation deterioration diagnosing devices capable of measuring a sheath circulating current flowing along a path formed by the metal sheath and the cross bonding; Simultaneously measuring the sheath circulation currents at both ends of the power cable on a path through which the sheath circulating current flows; Calculating a charge current in the power cable by synthesizing the sheath cyclic current measured at both ends of the power cable; Obtaining a third harmonic current of the charging current; And analyzing the third harmonic current to determine whether there is insulation deterioration in the power cable; .

In the present invention, the time synchronization step may include a step of synchronizing the plurality of insulation deterioration diagnosing devices, which are disposed apart from each other, with a measurement start time at which the measurement of the sheath circulation current starts and a measurement end time Can be made the same.

In the present invention, each of the plurality of insulation degradation diagnosis apparatuses includes a GPS unit, and the GPS unit can time-synchronize the plurality of insulation degradation diagnosis apparatuses using GPS signals.

In the present invention, simultaneously measuring the sheath circulation current may include connecting at least two of the insulation deterioration diagnosis devices to the connection cages disposed at both ends of the power cable on a path through which the sheath circulating current flows, It is possible to simultaneously measure the sheath circulating current flowing through each of the connection boxes.

In the present invention, the sheath circulation current measured by the plurality of insulation deterioration diagnostics apparatuses arranged apart from each other can be transmitted and received between the insulation deterioration diagnosis apparatuses.

In the present invention, a sensor portion is disposed on a cross-bonding line for cross-bonding the power cables constituting the three-phase transmission line, and the sheath circulating current can be measured by the sensor portion.

In the present invention, the sheath circulation current includes a sheath induction current and a charge current, and the sheath induction current is generated by a sheath induction voltage induced by a conductor current flowing in the conductor of the power cable, And the charge current may include a capacitive leakage current and a conductive leakage current flowing between the conductor and the metal sheath.

In the present invention, the charging current may be obtained by subtracting the sheath circulating current measured at one end of the power cable and the sheath circulating current measured at the other end of the power cable.

In the present invention, it is possible to determine that there is insulation deterioration when the third harmonic current is greater than a predetermined value.

The apparatus for diagnosing the deterioration of insulation of a three-phase transmission line according to an embodiment of the present invention includes an insulation deterioration diagnosis device for a three-phase transmission line in which metal cables of a power cable are cross- A GPS unit for performing time synchronization between the plurality of insulation deterioration diagnosis apparatuses spaced apart from each other; A sensor unit for measuring a sheath circulating current flowing along a cross-bonding line connected to one end of the power cable; A communication unit for transmitting and receiving the measured sheath circulating current value between the insulation degradation diagnosis apparatuses disposed apart from each other; And a controller for diagnosing insulation deterioration of the power cable by extracting a third harmonic current of the charging current by combining the measured sheath circulation current and the received sheath circulation current to derive a charging current of the power cable, .

In the present invention, each of the plurality of insulated deterioration diagnosis apparatuses disposed apart from each other has the same measurement start time at which the measurement of the sheath circulation current starts and the measurement end time at which the measurement of the sheath circulation current ends can do.

In the present invention, at least two of the above-mentioned insulation deterioration diagnosis devices are connected to each of the connection cages disposed at both ends of the power cable on the path through which the sheath circulating current flows, and the sheath circulating current flowing through each of the connection cages It can be measured at the same time.

In the present invention, the sheath circulation current includes a sheath induction current and a charge current, and the sheath induction current is generated by a sheath induction voltage induced by a conductor current flowing in the conductor of the power cable, And the charge current may include a capacitive leakage current and a conductive leakage current flowing between the conductor and the metal sheath.

In the present invention, the charging current may be obtained by subtracting the sheath circulating current measured at one end of the power cable and the sheath circulating current measured at the other end of the power cable.

In the present invention, the controller may perform the Fourier analysis on the charge current derived from the sheath circulation current measured at both ends of the power cable to extract the third harmonic current.

In the present invention, the controller may determine that there is insulation deterioration when the third harmonic current is greater than or equal to a predetermined value.

According to an embodiment of the present invention, it is possible to diagnose insulation deterioration of a power cable disposed in each section in a cross-bonded three-phase transmission line.

1 is a perspective view showing the internal construction of a power cable having an insulation layer composed of XLPE.
Fig. 2 is a perspective view schematically showing a connection box for connecting two cut power cables; Fig.
3 is a schematic view showing a cross-bonded three-phase transmission line.
4 is a schematic diagram showing the flow of sheath circulating current in a cross-bonded three-phase transmission line.
5 is a block diagram schematically showing an apparatus for diagnosing an insulation degradation according to an embodiment of the present invention.
FIG. 6 is a configuration diagram showing a state in which the insulation degradation diagnosis apparatus of FIG. 5 is connected to a cross-bonded three-phase transmission line.
7 is a flowchart schematically showing a method of diagnosing insulation deterioration of a three-phase transmission line according to an embodiment of the present invention.
FIGS. 8 to 16 are diagrams for explaining a process of determining the charge current after measuring the sheath circulating current.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are provided so that the disclosure can be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals designate like elements throughout the specification.

Hereinafter, a configuration of a power cable will be described first, and a configuration of a connection box will be described.

1 is a perspective view showing an internal configuration of a power cable 100 having an insulating layer composed of XLPE.

Referring to FIG. 1, the power cable 100 may include a conductor 10 along a central portion thereof. The conductor 10 serves as a passage through which electric current flows, and may be composed of, for example, copper or aluminum. The conductor (10) may be constituted by twining a plurality of element wires (11).

The surface of the conductor 10 is not smooth, the electric field may be uneven, and corona discharge tends to occur partially. In addition, when a gap is formed between the surface of the conductor 10 and the insulating layer 14 described later, the insulating performance may be deteriorated. In order to solve such a problem, the outer surface of the conductor 10 is covered with a semiconductive material such as semiconductive carbon paper, and the layer formed by the semiconductive material is defined as the inner semiconductive layer 12.

The inner semiconductive layer 12 uniformizes the charge distribution on the conductive surface to make the electric field uniform, thereby improving the dielectric strength of the insulating layer 14 described later. Furthermore, the formation of a gap between the conductor 10 and the insulating layer 14 is prevented to prevent corona discharge and ionization. The inner semiconductive layer 12 also prevents penetration of the insulating layer 14 into the conductor 10 when the power cable 100 is manufactured.

As a result, the inner semiconductive layer 12 prevents the electric field relaxation on the surface of the conductor 10 and the partial discharge caused by the void between the conductor 10 and the insulating layer 14. In addition, the inner semiconductive layer 12 maintains an ideal shape of a concentric cylindrical electrode in the cable so that the surface of the conductor 10 is smoothed to alleviate field concentration, and the conductor 10 and the insulating layer 14 are brought into close contact with each other Corona discharge that may occur on the surface of the conductor 10 can be prevented. Furthermore, it is possible to prevent electron injection and electron flow between the conductor 10 and the inner semiconductive layer 12 and between the inner semiconductive layer 12 and the insulating layer 14 to adsorb impurities.

An insulating layer 14 may be provided on the outer side of the inner semiconductive layer 12. The insulating layer 14 electrically insulates the conductor 10 from the outside. In general, the insulating layer 14 should have a high breakdown voltage, and the insulating performance must be stable for a long period of time. Furthermore, it should have low dielectric loss and resistance to heat such as heat resistance. Accordingly, the insulating layer 14 can be made of a polyolefin resin such as polyethylene and polypropylene, and can be preferably made of a polyethylene resin. The polyethylene resin may be a crosslinked resin, and may be produced by a silane or an organic peroxide such as, for example, dicumylperoxide (DCP) as a crosslinking agent.

On the other hand, if not only the inside but also the outside of the insulating layer 14 is not shielded, a part of the electric field is absorbed by the insulating layer 14, but most of the electric field is discharged to the outside. In this case, if the electric field becomes larger than a predetermined value, the insulating layer 14 and the outer surface of the power cable 100 may be damaged by an electric field. Therefore, a semiconductive layer is provided on the outer side of the insulating layer 14 and is defined as an outer semiconductive layer 16 to distinguish it from the inner semiconductive layer 12 described above. As a result, the outer semiconductive layer 16 serves to improve the dielectric strength of the insulating layer 14 by making the distribution of the lines of electric force between the inner semiconductive layer 12 and the inner semiconductive layer 12 equal. Further, the outer semiconductive layer 16 can smooth the surface of the insulating layer 14 in the cable, thereby alleviating the electric field concentration, and preventing the corona discharge.

A metallic sheath 18 may be provided on the outside of the outer semiconductive layer 16. The metallic sheath 18 may be provided for electrical shielding and return of short-circuit current. In the three-phase transmission line, the metal sheath 18 of the three-phase transmission line can be cross-bonded to reduce the sheath induced voltage. This will be described later.

A jacket (20) is provided on the outer side of the power cable (100). The sheath 20 is provided on the outer side of the cable 100 to protect the internal structure of the cable 100. Therefore, the outer cover 20 is excellent in chemical resistance and mechanical strength to withstand chemicals such as weatherability, chemical substances, and the like, which can withstand various environments such as light, weather, moisture and air in various climatic conditions. Generally, it is made of PVC (Polyvinyl Chloride) or PE (Polyethylene).

Generally, the fabrication of ultra-high voltage underground power cable does not produce the whole length of the power section, but produces cable with a certain length of 200 ~ 1000 m and installs it in underground power section. The installed power cable and the power cable are formed as a connection box, and are drawn out to the outside through an underground termination connection box and connected to the electric equipment and the like. Also, in the case of an ultra-high voltage submersible power cable as well as a power distribution cable, the entire length of the power section is not produced, the cable is produced in a predetermined length and installed in the power section, and the installed power cables can be connected by connection.

FIG. 2 is an exploded perspective view schematically showing the form in which the connector 40 is coupled to the cable 10. FIG.

Referring to FIG. 2, the connection box 40 surrounds two cables 100a and 100b exposed with the insulation layer 14, the inner semiconductive layer 13, the wire 11, and the like.

More specifically, the two cables 100a and 100b are covered by the corona shield 32 after the wires 11a and 11b, i.e., conductors are crimped and connected by welding or crimping sleeves, and are conductively connected. Here, it is electrically connected to the portion connected to the corona shield 32 and the conductor.

Further, the corona shield 32 may be formed so as to surround the compression sleeve 31 and the inner semiconductive layers 12a and 12b. That is, the corona shield 32 may be formed to extend in contact with the end faces of the insulating layers 14a and 14b of the two cables 100a and 100b while surrounding the compression sleeve 31 and the inner semiconductive layers 12a and 12b. have. The corona shield 32 may be formed so as not to have a step with the insulating layers 14a and 14b. The sleeve 41 of the junction box 40 may be formed to surround the insulating layers 14a and 14b and the corona shield 32. [

The sleeve 41 is mainly made of a silicon material, and liquid silicon rubber can be used. The sleeve 41 may include a body portion 41a, a first contact portion 41b, and a second contact portion 41c. The body portion 41a is made of an insulating material, and may be made of silicon, for example. The first contact portion 41b and the second contact portion 41c may include a semiconductive material such as carbon black. The first contact portion 41b may be formed so as to surround the boundary portion between the corona shield 32 and the insulating layers 14a and 14b while surrounding the entire outer surface of the corona shield 32. [ The first contact portion 41b is made of a semiconductive material and can prevent an electric field concentration phenomenon that may occur at the interface between the corona shield 32 and the insulating layer 14. The second contact portion 41c is disposed at both ends of the sleeve 41 and contacts the outer semiconductive layer (16 in Fig. 1) exposed from the cables 100a and 100b while contacting the outer surface of the sleeve 41 And may be formed to extend toward the side surface. The second contact portion 41c can also alleviate the electric field concentration phenomenon that may occur at the ends of the metal sheaths 18a and 18b like the first contact portion 41b.

A magnetic field is formed around the conductor 10 in the power cable 100 shown in FIG. 1, and a voltage is induced in the metal sheath 18 by the magnetic field. The induced voltage induced in the metal sheath 18 is excessively induced when the metal sheath 18 in the power cable 100 is cut and separated by a certain length when the power cable 100 is installed over a long distance, There is a problem that the method layer is destroyed by the transient voltage due to the opening / closing surge. Accordingly, the sheath induced voltage can be limited by separating the metal sheath 18 from the power cable 100 for every predetermined interval (500 to 1000 m) and applying a single-side grounding or cross-bonding method.

Fig. 3 is a schematic view showing a three-phase transmission line in which a metal sheath 18 capable of restraining a cis-induced voltage is cross-bonded.

3, the three-phase transmission line is composed of an A-phase transmission line, a B-phase transmission line and a C-phase transmission line, and each transmission line includes a plurality of transmission lines (N-1, n, n + 1), and each cod can be made up of three small sections (L1, L2, L3). Each of the small sections L1, L2, and L3 may be formed by the power cable shown in FIG.

The connection box shown in FIG. 2 is disposed between the large-sized and small-sized sections to connect the power cables. More specifically, a common connection box 40NJ is disposed between the spaced caulkings to connect the power cables, and an insulation connection box 40IJ is disposed between the small sections to connect the power cables.

The normal connection box 40NJ connects the conductor 10 of the power cable and also connects the metal sheath 18 to ground. For example, in the case of the ordinary connection box 40NJ, the conductors 10 of the power cables 100a1, 100b1 and 100c1 of the large crossing N and the power cables 100a3 and 100b3 of the crossing N- And the conductor 10 of each of the power cables 100a1, 100b1 and 100c1 of the large-diameter wire N are connected to one end 18a11, 18b11 and 18c11 of the metal sheath of the large- The other ends 18a31, 18b32 and 18c32 of the metal sheaths of the cables 100a3, 100b3 and 100c3 are electrically connected to each other and can be grounded by the ground line CB1.

The conductors 10 of the power cables 100a3, 100b3, and 100c3 of the large-diameter nines N are also connected to the common connection box 40NJ disposed between the large- The conductors 10 of the power cables 100a1, 100b1 and 100c1 of the large cross section N + 1 are connected to each other and the other ends 18a32 and 183b of the metal sheath of the power cables 100a3, 100b3 and 100c3 of the large cross- The ends 18a11, 18b12 and 18c11 of the metal sheaths of the power cables 100a1, 100b1 and 100c1 of the bus bars 18b32 and 18c32 and the bus bar N + 1 are electrically connected to each other and grounded by the ground line CB8 .

An insulated connection box 40IJ may be disposed between the small sections (L1 and L2, L2 and L3) in the interstice N. In the insulating connection box 40IJ, conductors (not shown) of the power cables 100a1, 100a2, 100a3 (100b1, 100b2, 100b3; 100c1, 100c2, 100c3) 10 are connected to each other, and the metal sheath is connected to the three-phase line by cross-bonding.

More specifically, the conductor 10 of the power cable 100a1 located in the first section L1 of the A-phase line A? And the conductor 10 of the power cable 100a2 located in the second section L2 Of the power cable 100b2 located in the second section L2 of the B-phase line B? And the metal sheath end 18a12 of the power cable 100a1 are connected to each other through the insulation sheathing box 40IJ, (18a21) may be electrically connected by the cross-bonding line CB2. The power cable 100c2 located in the second section L2 of the C-phase line B? And the metal sheath terminal 18a12 of the power cable 100b1 located in the first section L1 of the B- The metal sheath end 18c21 of the first metal layer 18 can be electrically connected by the cross-bonding line CB3. The power cable 100a2 located in the second section L2 of the A-phase line A? And the metal sheath terminal 18c12 of the power cable 100c1 located in the first section L1 of the C- The metal sheath ends 18a21 of the first metal layer 18 can be electrically connected to each other by the cross-bonding line CB4.

The power cable 100a2 located at the second section L2 of the A-phase line A? And the power cable at the third section L3 of the B-phase line B? 100c3 may be electrically connected by the cross-bonding line CB5. The power cable 100c3 located in the third section L3 of the C-phase line C? And the metal sheath terminal 18b22 of the power cable 100b2 located in the second section L2 of the B- And the metal sheath end 18c31 of the capacitor 18c may be electrically connected by the cross-bonding line CB6. The power cable 100a3 located in the third section L3 of the A-phase line A? And the metal sheath terminal 18c22 of the power cable 100c2 located in the second section L2 of the C- The metal sheath ends 18a31 of the first metal layer 18a may be electrically connected by the cross-bonding line CB7.

The metal sheaths (18a12 and 18b21, 18b12 and 18c21, 18c12 and 18a21; 18a22 and 18b31, 18b22 and 18c31, 18c22 and 18a31) are stretched at three intervals in the long-distance underground transmission line, 18b32, 18c32, 18a11, 18b11, 18c11, 18a32, 18b32, 18c32) are grounded, if the three-phase conductor currents are equilibrium and the three span lengths are all equilateral, the induced voltage at both ends of the metal sheath is zero So that the sheath induction current may not flow. However, since the above conditions are not possible in actual field, a certain amount of sheath induction current flows.

Along the metal sheath and the cross-bonding line, not only the sheath induction current but also the charge current can flow. More specifically, an insulating layer 14 is disposed between the conductor 10 and the metallic sheath 18 within the power cable 100 (FIG. 1), and the conductor 10, the insulating layer 14, The sheath 18 serves as a capacitor and a capacitive leakage current can flow between the conductor 10 and the metallic sheath 18. [ Further, due to the deterioration of the insulator 14, a conductive leakage current may flow between the conductor 10 and the metallic sheath 18. The charging leakage current and the conductive leakage current flowing between the conductor 10 and the metal sheath 18 can be regarded as a charging current.

The current flowing along the metal sheath and the cross-bonding line is the sheath induction current and the charge current, and the sheath induction current and the charge current are called the sheath circulation current.

The charging current increases as the deterioration of the insulator 14 increases. Therefore, the insulation deterioration of the power cable 100 can be diagnosed by measuring and evaluating the charging current of the power cable 100.

The insulation deterioration diagnosis apparatus according to an embodiment of the present invention can diagnose insulation deterioration of the power cable 100 by measuring the sheath circulation current and extracting the charging current therefrom. This will be described later.

4 is a schematic diagram showing the flow of sheath circulating current in a cross-bonded three-phase transmission line.

4, when a current (conductor current) flows through the conductors 10A, 10B and 10C on the three-phase transmission line Aφ, Bφ and Cφ, the conductor current flows along the metal sheath and the cross- The induced currents Isc1, Isc2, Isc3 can flow. More specifically, the metal sheath 18b1 is connected to the metal sheath 18b1 along the grounding line CB8, the metal sheath 18c3, the cross-bonding line CB6, the metal sheath 18b2, the cross-bonding line CB2, The metal sheath 18b2 and the metal sheath 18c2 and the metal sheath 18b1 and the grounding line CB1 flow through the ground line CB8, the metal sheath 18a3, the cross-bonding line CB7, the metal sheath 18c2, The sheath induction current Isc2 flows along the wire 18 and the ground wire CB8 and the metal sheath 18b3, the cross-bonding wire CB5, the metal sheath 18a2, the cross-bonding wire CB4, the metal sheath 18c1, The sheath induction current Isc1 can flow along the first switching element CB1.

The metal sheath 18a1 and the conductor 10A form a capacitor equivalent circuit so that the charge currents Ia1 and Ia12 flow through the metal sheath 18a1. That is to say, the charging current Ia1 flows along the grounding line CB1 from the one end 18a11 of the metal sheath 18a1 to the grounding line CB1 and flows toward the metal sheath 18b2 from the other end 18a12 of the metal sheath 18a1, Charge current Ia12 can flow along line CB2.

Similarly, in the metal sheath 18b2, the charge current Ib21 flows along the cross-bonding line CB2 toward the other end 18a12 of the metal sheath 18a1 and cross-bonded to the other end 18c31 of the metal sheath 18c3 The charge current Ic23 flows along the line CB6 and the charge current Ic32 flows along the crossing line CB6 toward the other end 18b23 of the metal sheath 18b2 in the metal sheath 18c3, The charging current Ic3 can flow along the grounding line CB8 in the grounding direction from the other end 18c32 of the sheath 18c3.

In the metal sheath 18b1, the charging current Ib1 flows from the one end 18b11 of the metal sheath 18b1 along the grounding line CB1 in the grounding direction and the metal sheath 18c2 at the other end 18b12 of the metal sheath 18b1, The charge current Ib12 may flow along the cross-bonding line CB3 toward the other end 18b12 of the metal sheath 18b1 in the metal sheath 18c2, The charge current Ic23 can flow along the cross bonding line CB7 toward one end 18a31 of the metal sheath 18a3 and the other end 18b32 of the metal sheath 18b3 can flow through the metal sheath 18a3, The charge current Ia32 flows along the cross bonding line CB7 and the charge current Ia3 flows along the ground line CB8 from the other end 18a32 of the metal sheath 18a3 toward the ground.

In the metallic sheath 18c1, the charging current Ic1 flows along the grounding line CB1 from the one end 18c11 of the metallic sheath 18c1 to the grounding direction and flows from the other end 18c12 of the metallic sheath 18c1 to the metallic sheath 18a2 The charge current Ic12 can flow along the cross bonding line CB4 toward the other end 18c12 of the metal sheath 18c1 in the metal sheath 18a2 along the cross bonding line CB4 The charging current Ia23 may flow along the cross bonding line CB5 toward the one end 18b31 of the metallic sheath 18b3 and the other end 18b22 of the metallic sheath 18b2 may flow through the metallic sheath 18b3, The charge current Ib32 flows along the cross-bonding line CB5 and the charge current Ib3 flows along the ground line CB8 from the other end 18b32 of the metal sheath 18b3 toward the ground.

As a result, it is possible to prevent the metal sheath 18b1 flowing along the path of the grounding line CB8, the metal sheath 18c3, the cross-bonding line CB6, the metal sheath 18b2, the cross-bonding line CB2, the metal sheath 18a1, The first sheath circulation current may include a sheath induction current Isc1 and charge currents Ia1, Ia12, Ib21, Ib23, Ic32, and Ic3. It is also possible to use a conductive material which flows along the path of the grounding line CB8, the metal sheath 18a3, the cross-bonding line CB7, the metal sheath 18c2, the cross- The second system circulation current may include a sheath induction current Isc2 and charge currents Ib1, Ib12, Ic21, Ic23, Ia32, Ia3. A third sheath 183 flowing along the path of the grounding line CB8, the metal sheath 18b3, the cross-bonding line CB5, the metal sheath 18a2, the cross-bonding line CB4, the metal sheath 18c1, The circulation current may include the sheath induction current Isc3 and the charging current Ic1, Ic12, Ia21, Ia23, Ib32, Ib3.

The apparatus for diagnosing insulation deterioration of a three-phase transmission line according to an embodiment of the present invention can diagnose insulation deterioration of the power cable 100 by measuring the first to third sheath circulating currents described above and extracting a charging current therefrom have. 5 is a block diagram schematically showing an apparatus for diagnosing an insulation degradation according to an embodiment of the present invention. FIG. 6 is a configuration diagram showing a state in which the insulation degradation diagnosis apparatus of FIG. 5 is connected to a cross-bonded three-phase transmission line.

5 and 6, an apparatus for diagnosing insulation deterioration of a three-phase transmission line according to an exemplary embodiment of the present invention includes a control unit 1100, a sensor unit 1200, a communication unit 1300, a GPS unit 1400, , And a storage unit (1500).

The sensor unit 1200 is connected to the cross-bonding line of the three-phase transmission line to measure the sheath circulation current. The sensor unit 1200 may be, for example, a CT sensor capable of measuring a current.

The sensor unit 1200 may be disposed on the path of the sheath circulating current to be measured. The sensor unit 1200 is connected to the metal sheath at both ends (end or intermediate connection (40 IJ in Fig. 6)) of the power cable (for example, 100b2 in Fig. 6) And the sheath circulation current can be measured at the same time. The charge current can be derived by combining the measured sheath circulating currents at both ends of the power cable at the same time, after measurement. This will be described later.

The sheath circulating current flowing through the cross bonding line is easier to measure than the current flowing through the power cable, and the charging current can be derived through the measured sheath circulating current. The insulated deterioration diagnosing apparatus according to an embodiment of the present invention includes a cross- It is possible to diagnose whether the power cable is deteriorated or not by extracting the third harmonic current of the charging current. The extraction of the third harmonic current from the charging current is possible through Fourier analysis. This will be described later.

6, in order to measure the first sheath circulating current, a path through which the first sheath circulating current flows (a ground line CB8, a metal sheath 18c3, a cross-bonding line CB6, 18b2, the cross-bonding line CB2, the metal sheath 18a1 and the ground line CB1) of the cross-bonding line CB2 and the cross-bonding line CB6, .

Each of the cross bonding lines CB2 and CB6 is connected to both ends of the power cable 100b2 and the power cable 100b2 is 500m to 1000m in length. Each of the sensor units 1200 is connected to the cross-bonding line CB2 and the cross-bonding line CB6 so that the waveform of the sheath circulation current can be measured at the same time.

When the sensor unit 1200 measures the waveform of the sheath circulation current at two points (for example, the points S2 and S3) where the sensor unit 1200 is spaced apart from each other, the measurement start time is recorded, and the measurement end time can also be recorded. When the sensor unit 1200 measures the waveform of the sheath circulation current at a predetermined time interval during a certain time between the measurement start time and the measurement end time, the measurement time can be recorded every time the waveform of the sheath circulation current is measured. The measurement start time, the measurement end time, the measurement time, and the waveform of the sheath circulation current may be stored in the storage unit 1500.

Since the plurality of deterioration diagnosis apparatuses 1000a and 1000b, which are spaced apart from each other before the sensor unit 1200 measures the waveform of the sheath circulation current, are time-synchronized, they are measured in the plurality of deterioration diagnosis apparatuses 1000a and 1000b The waveforms of the stored sheath circulation current all have the same measurement end time as the same measurement start time. This will be described later.

The control unit 1100 may include an operation unit 1110, an extraction unit 1120, and an analysis unit 1130.

The calculating unit 1110 may calculate the sheath circulating current measured at least two points and derive the charging current. That is, since the sheath circulating current measured at each point (both ends of the power cable) is composed of the induction current and the charging current, the charging current can be obtained by removing the induced current component from the measured sheath circulating current, The charge current flowing through the metallic sheath of the power cable can be obtained by subtracting the measured sheath circulating current at two points to remove the induced current component from the circulating current. Since the component of the induced current is the same at both ends of the power cable, the induced current is subtracted from the measured shear circulating current at both ends of the power cable, and only the charging current can be obtained.

For example, the sheath circulation current J2 measured at the point S2 in Fig. 6 includes the sheath induction current Isc1 and the charge currents Ia12, Ib21 and Ic32, and the sheath circulation current J3 Can be included as the sheath induction current Isc1 and the charge currents Ia12, Ib23, and Ic32. This can be expressed as follows.

[Equation 1]

J2 = Isc1 + Ia12 + Ib21 + Ic32

&Quot; (2) "

J3 = Isc1 + Ia12 + Ib23 + Ic32

The operation unit 1110 can subtract the sheath circulation current J2 measured at the point S2 and the sheath circulation current J3 measured at the point S3, and the result is as shown in the following equation (3).

&Quot; (3) "

J2-J3 = (Isc1 + Ia12 + Ib21 + Ic32) - (Isc1 + Ia12 + Ib23 + Ic32) = Ib21-Ib23

Since the charging current Ib23 is different in direction from the charging current Ib21 and the size thereof is the same, Ib21-Ib23 derived from the subtraction corresponds to the charging current value flowing through the metallic sheath 18b of the power cable 100b2. In this way, the calculating unit 1110 can obtain the charging current flowing through the metal sheath of the power cable disposed in each small section of the three-phase transmission line. That is, according to an embodiment of the present invention, the charge current can be obtained by measuring the sheath circulating current at two points as described above and calculating them.

The extraction unit 1120 can extract the third harmonic current for the charging current in the small interval derived by the calculation unit 1110. [ The extracting unit 1120 can extract the three harmonic currents of the charging current through Fourier analysis. In general, the harmonics have a small amplitude in proportion to the order of the harmonics. The lower the number of harmonics, the more the amplitude is turned on. The harmonics have the highest amplitude. 3 Harmonic current can be analyzed easily because it has the largest amplitude.

The analysis unit 1130 can analyze the insulation deterioration of the power cable by analyzing the three harmonic currents extracted by the extraction unit 1120. Since the third harmonic current extracted by the extraction unit 1120 is extracted from the charging current flowing through the metal sheath of the power cable 100b2, the insulation deterioration of the power cable 100b2 can be diagnosed by analyzing the third harmonic current. As the insulation deterioration of the power cable 100b2 progresses, the charging current flowing through the metal sheath of the power cable 100b2 increases and the amplitude of the third harmonic current of the charging current also increases. Therefore, the analyzer 1130 can determine that there is insulation deterioration when the amplitude of the third harmonic current is higher than a certain level.

The communication unit 1300 can perform a function of transmitting and receiving data to and from another insulation deterioration diagnosis apparatus disposed apart from the other. As described above, in order to measure the charging current flowing in the power cable (100b2 in Fig. 6) disposed in the small section, two pieces of the insulation deterioration diagnosis devices 1000a and 1000b are connected to both ends of the power cable 100b2, (CB2, CB5) and measure the sheath circulation current at these points. The communication unit 1300 can transmit and receive the sheath circulating current values measured by the two insulation degradation diagnostics apparatuses 1000a and 1000b to each other.

The sheath-circulating-current waveform measured at each point (both ends of the power cable) during a predetermined period of time has the same measurement start time and measurement end time through time synchronization. As described above, The charging current can be derived through subtraction of the sheath circulating current.

The GPS unit 1400 can perform time synchronization with other insulated deterioration diagnosis apparatuses disposed apart from each other. The sheath circulating current measured at the positions (S2 and S3 in Fig. 6) which are spaced apart from each other can be obtained by combining the waveforms of the sheath circulating currents measured by the calculating unit 1110, as described above. Since the sheath circulating current has a phase, the measured sheath circulating current should have the same phase. Time synchronization of the insulation deterioration diagnosis apparatuses spaced apart to measure the sheath circulating current having the same phase is required, and the GPS unit 1400 calculates the time between the insulation deterioration diagnosis apparatuses 1000a and 1000b Can be synchronized.

A reliable result can not be obtained in the synthesis of the sheath circulating current waveforms at the respective points when the plurality of the insulation deterioration diagnosis apparatuses 1000a and 1000b spaced apart from each other are not time synchronized. That is, since the sheath circulation current to be measured has a waveform of 60 Hz, in general, the sheath circulation current has a waveform of 60 Hz. Therefore, when the time is not synchronized, a measurement error of the sheath circulation current due to the difference in measurement time may occur. (Or smaller) than the difference in magnitude of the sheath circulation current due to the sheath current. Therefore, the accuracy in determining whether the cable is deteriorated can be greatly impaired.

Therefore, the GPS unit 1400 synchronizes the plurality of insulation deterioration diagnostics apparatuses 1000a and 1000b spaced apart from each other before measuring the waveform of the sheath circulation current so that the measurement error of the sheath circulation current due to the time discrepancy The reliability of the cable deterioration discrimination can be increased.

The GPS unit 1400 can synchronize the time between the insulation deterioration diagnosis apparatuses 1000a and 1000b which are relatively accurately spaced apart from each other by an error of about 10 ^-7 seconds or less. Since the error of 10 ^-7 seconds is a very short time interval compared to the frequency of 60 Hz, it can be seen that there is almost no current measurement error due to such a difference.

The storage unit 1500 may store the measured sheath circulation current value in the sensor unit 1200 and may store the sheath circulation current value transmitted through the communication unit 1300. The result stored in the storage unit 1500 may be stored in the storage unit 1500, And stores the extracted charge current values. In addition, a lookup table indicating the degree of deterioration of insulation according to the amplitude of the third harmonic current can be stored.

7 is a flowchart schematically showing a method of diagnosing insulation deterioration of a three-phase transmission line according to an embodiment of the present invention.

Referring to FIG. 7, first, at least two or more three-phase transmission lines are used to synchronize the insulation deterioration diagnosing apparatus (S101). The GPS unit 1400 can synchronize the time of the three-phase transmission line insulated deterioration diagnosis devices 1000a and 1000b, which are spaced apart from each other, using GPS signals.

Next, the sheath circulating current is measured at both ends of the power cable (S102). The sensor unit 1200 is connected to the cross-bonding line of the three-phase transmission line to measure the sheath circulation current. More specifically, the sensor unit 1200 may be disposed on a path of a sheath circulating current to be measured. Referring to FIG. 6 as an example, the first sheath circulating current A path connected to the flowing path (the grounding line CB8, the metal sheath 18c3, the cross-bonding line CB6, the metal sheath 18b2, the cross-bonding line CB2, the metal sheath 18a1, and the ground line CB1) May be disposed at the point S2 on the cross-bonding line CB2 and the point S3 on the cross-bonding line CB6, respectively.

Each of the cross bonding lines CB2 and CB6 is connected to both ends of the power cable 100b2 and the power cable 100b2 is 500m to 1000m in length. Each of these sensor units 1200 is connected to the cross-bonding line CB2 and the cross-bonding line CB6 to measure the sheath circulation current at the same time.

Next, the measured sheath circulating current values between the three-phase transmission line insulated deterioration diagnosis apparatuses 1000a and 1000b can be transmitted and received to each other (S103). Data can be transmitted and received between the three-phase transmission line insulated deterioration diagnosis apparatuses 1000a and 1000b which are disposed apart from each other by the communication unit 1300. [ As described above, in order to measure the charging current flowing in the power cable (100b2 in Fig. 6) disposed in the small section, two pieces of the insulation deterioration diagnosis devices 1000a and 1000b are connected to both ends of the power cable 100b2, (CB2, CB5) and measure the sheath circulation current at these points. The communication unit 1300 can transmit and receive the sheath circulating current values measured by the two insulation degradation diagnostics apparatuses 1000a and 1000b to each other.

Next, the charging current can be derived from the measured sheath circulating current and the transmitted sheath circulating current (S104). For example, the sheath circulation current measured at the point S2 in FIG. 6 and the sheath circulation current measured at the point S3 and transmitted through the communication unit 1300 can be calculated by the calculating unit 1110, and the charge current can be derived. That is, the sheath circulation current J2 measured at the point S2 includes the sheath induction current Isc1 and the charge currents Ia12, Ib21 and Ic32, and J2 = Isc1 + Ia12 + Ib21 + Ic32, The measured sheath circulating current J3 is included in the sheath induction current Isc1 and the charge currents Ia12, Ib23, and Ic32, so J3 = Isc1 + Ia12 + Ib23 + Ic32. The operation unit 1110 can subtract the sheath circulation current J2 measured at the point S2 and the sheath circulation current J3 measured at the point S3 so that J2-J3 = (Isc1 + Ia12 + Ib21 + Ic32 ) - (Isc1 + Ia12 + Ib23 + Ic32) = Ib21-Ib23.

Since the charging current Ib23 is different in direction from the charging current Ib21 and the size thereof is the same, Ib21-Ib23 derived from the subtraction corresponds to the charging current value flowing through the metallic sheath 18b of the power cable 100b2. In this way, the calculating unit 1110 can obtain the charging current flowing through the metal sheath of the power cable disposed in each small section of the three-phase transmission line. Charge currents are difficult to measure directly because they contain inductive components. However, according to one embodiment of the present invention, the charge current can be obtained by measuring the sheath circulating current at two points as described above and calculating them.

Next, the third harmonic current component can be extracted from the derived charge current (S105). The extraction unit 1120 can extract the third harmonic current for the charging current in the small interval derived by the calculation unit 1110. [ The extraction unit 1120 can extract the three harmonic currents of the charging current through the Fourier analysis. 3 Harmonic current can be analyzed easily because it has the largest amplitude.

Next, the insulation deterioration of the power cable can be diagnosed by analyzing the third harmonic current component (S106). The third harmonic current extracted by the extracting unit 1120 is analyzed by the analyzing unit 1130 and the analyzing unit 1130 can diagnose the deterioration of the power cable through the analyzing unit 1130. That is, since the third harmonic current extracted by the extraction unit 1120 is extracted from the charge current flowing through the metal sheath of the power cable 100b2, the third harmonic current can be analyzed to diagnose the insulation deterioration of the power cable 100b2 have. As the insulation deterioration of the power cable 100b2 progresses, the charging current flowing through the metal sheath of the power cable 100b2 increases and the amplitude of the third harmonic current of the charging current also increases. Therefore, the analyzer 1130 can determine that there is insulation deterioration when the amplitude of the third harmonic current is higher than a certain level.

FIGS. 8 to 16 are diagrams for explaining a process of determining the charge current after measuring the sheath circulating current.

8 is a diagram for explaining a process of calculating a charge current flowing through the metallic sheath 18a1 after measuring the sheath circulation current at the points S1 and S2.

Referring to FIG. 8, one insulated deterioration diagnosis device for three-phase transmission line is connected to the point S1 to measure the sheath circulation current, and another insulated deterioration diagnosis device for three-phase transmission line is connected to point S2, Measure the circulating current.

The point S1 is a point on the ground line CB1 connected to one end 18a11 of the metal sheath 18a1 and the point S2 is a point on the crossing line CB2 connected to the other end 18a12 of the metal sheath 18a1. Lt; / RTI > At the point S1, the sheath induction current Isc1 flows from the one end 18a11 of the metal sheath 18a1 to the charging current Ia1 flowing along the grounding line CB1 in the grounding direction and the other end 18a12 of the metal sheath 18a1, The charge current Ic32 flowing along the cross-bonding line CB6 flows toward the charge current Ib21 flowing along the bonding line CB2 and the other end 18b12 of the metallic sheath 18b1. That is, the sheath circulating current J1 measured at the point S1 is given by the following equation (4).

&Quot; (4) "

J1 = Isc1 + Ia1 + Ib21 + Ic32

A charging current Ia12 flowing along the cross bonding line CB2 toward the metallic sheath 18b2 at the other end 18a12 of the metallic sheath 18a1 at the point S2, The charge current Ib21 flowing along the cross-bonding line CB2 toward the other end 18a12 of the metal sheath 18a1 in the metal sheath 18b21 and the cross-bonding line CB6 toward the other end 18b22 of the metal sheath 18b2 And the charging current Ic32 flowing along therewith flows. That is, the sheath circulation current J2 measured at the point S2 is expressed by the following equation (5).

&Quot; (5) "

J2 = Isc1 + Ia12 + Ib21 + Ic32

The operation unit 1110 can subtract the sheath circulation current J1 measured at the point S1 and the sheath circulation current J2 measured at the point S2, and the result is shown in Equation (6).

&Quot; (6) "

J1-J2 = (Isc1 + Ia1 + Ib21 + Ic32) - (Isc1 + Ia12 + Ib21 + Ic32) = Ia1-Ia12

Since the charge current Ia12 is different in direction from the charge current Ia1 and the magnitude thereof is the same, Ia1-Ia12 derived from the subtraction result is the metal sheath of the power cable located in the first section L1 of the A- Corresponds to the charging current value flowing in the charging circuit 18a1. The extraction unit 1120 extracts the third harmonic current from the charge current derived by the calculation unit 1110 and the analysis unit 1130 analyzes the third harmonic current to determine the insulation deterioration of the power cable Can be diagnosed.

FIG. 9 is a diagram for explaining a process of calculating a charge current flowing through the metal sheath 18b2 after measuring the sheath circulation current at the points S2 and S3.

9, one insulated deterioration diagnosis device for three-phase transmission line is connected to the point S2 to measure the sheath circulation current, and another insulated deterioration diagnosis device for the three-phase transmission line is connected to the point S3, Measure the circulating current.

Point S2 is a point on the cross-bonding line CB2 connected to one end 18b21 of the metal sheath 18b2 and S3 point is a point on the cross-bonding line CB6 connected to the other end 18b22 of the metal sheath 18b2 May be a single point.

The charging current Ia12 flowing along the cross-bonding line CB1 toward the metallic sheath 18b2 at the other end 18a12 of the metallic sheath 18a1 at the point S2, A charge current Ic32 flowing along the cross-bonding line CB6 flows toward the other end 18b22 of the metal sheath 18b2 and the charge current Ib21 flowing along the cross-bonding line CB2 toward the capacitor 18a12. That is, the sheath circulation current J2 measured at the point S2 is given by the following equation (7).

&Quot; (7) "

J2 = Isc1 + Ia12 + Ib21 + Ic32

A charging current Ia12 flowing along the cross bonding line CB2 toward the metallic sheath 18b2 at the other end 18a12 of the metallic sheath 18a1 at the point S3, A charge current Ic32 flowing along the cross-bonding line CB6 flows toward the other end 18b22 of the metal sheath 18b2 and the charge current Ib23 flowing along the cross-bonding line CB6 toward the capacitor 18c31. That is, the sheath circulation current J3 measured at the point S3 is expressed by the following equation (8).

&Quot; (8) "

J3 = Isc1 + Ia12 + Ib23 + Ic32

The operation unit 1110 can subtract the sheath circulation current J2 measured at the point S2 and the sheath circulation current J3 measured at the point S3, and the result is as shown in the following equation (9).

&Quot; (9) "

J2-J3 = (Isc1 + Ia12 + Ib21 + Ic32) - (Isc1 + Ia12 + Ib23 + Ic32) = Ib21-Ib23

Since the charging current Ib21 is different in direction from the charging current Ib23 and the size thereof is the same, Ib21-Ib23 derived from the subtraction result is the metal sheath of the power cable located in the second section L2 of the B-phase transmission line Corresponds to the charging current value flowing through the second switching transistor 18b2. The extraction unit 1120 extracts the third harmonic current from the charge current derived by the calculation unit 1110 and the analysis unit 1130 analyzes the third harmonic current to determine the insulation deterioration of the power cable Can be diagnosed.

FIG. 10 is a diagram illustrating a process of calculating a charge current flowing through the metal sheath 18c3 after measuring the sheath circulation current at points S3 and S4.

10, one insulated deterioration diagnosis device for three-phase transmission line is connected to the point S3 to measure the sheath circulation current, and another insulated deterioration diagnosis device for the three-phase transmission line is connected to the point S4, Measure the circulating current.

The point S3 is a point on the cross-bonding line CB6 connected to the one end 18c31 of the metal sheath 18c3 and the point S4 is a point on the ground line CB8 connected to the other end 18c32 of the metal sheath 18c3. Lt; / RTI >

A charging current Ia12 flowing along the cross bonding line CB2 toward the metallic sheath 18b2 at the other end 18a12 of the metallic sheath 18a1 at the point S3, A charge current Ic32 flowing along the cross-bonding line CB6 flows toward the other end 18b22 of the metal sheath 18b2 and the charge current Ib23 flowing along the cross-bonding line CB6 toward the capacitor 18c31. That is, the sheath circulation current J3 measured at the point S3 is expressed by the following equation (10).

&Quot; (10) "

J3 = Isc1 + Ia12 + Ib23 + Ic32

A charging current Ia12 flowing along the cross-bonding line CB2 toward the metallic sheath 18b2 at the other end 18a12 of the metallic sheath 18a1 at the point S4, A charge current Ic3 flowing along the crossing line CB6 flows toward the capacitor 18c31 and a charge current Ic3 flowing along the ground line CB8 flows from the other end 18c32 of the metal sheath 18c3. That is, the sheath circulating current J4 measured at the point S4 is given by the following equation (11).

&Quot; (11) "

J4 = Isc1 + Ia12 + Ib23 + Ic3

The operation unit 1110 can subtract the sheath circulation current J3 measured at the point S3 and the sheath circulation current J4 measured at the point S4, and the result is shown in the following equation (12).

&Quot; (12) "

J3-J4 = (Isc1 + Ia12 + Ib23 + Ic32) - (Isc1 + Ia12 + Ib23 + Ic3) = Ic32-Ic3

Since the charge current Ic32 is different in direction from the charge current Ic3 and the magnitude thereof is the same, Ic32-Ic3 derived from the subtraction result is the metal sheath of the power cable located in the third section L3 of the C-phase transmission line Corresponds to the charge current value flowing in the second capacitor 18c3. As described above, the charging current derived by the calculating unit 1110 is obtained by extracting the third harmonic current from the extracting unit 1120 and analyzing the third harmonic current by the analyzing unit 1130 to diagnose the insulation deterioration of the power cable .

11 is a diagram for explaining a process of calculating a charge current flowing through the metal sheath 18b1 after measuring the sheath circulation current at the points S5 and S6.

11, one insulated deterioration diagnosis device for the three-phase transmission line is connected to the point S5 to measure the sheath circulation current, and another insulated deterioration diagnosis device for the three-phase transmission line is connected to the point S6, Measure the circulating current.

Point S5 is a point on the ground line CB1 connected to one end 18b11 of the metal sheath 18b1 and point S6 is a point on the crossing line CB3 connected to the other end 18b12 of the metal sheath 18b1 Lt; / RTI >

At the point S5, the sheath induction current Isc2 flows from the one end 18b11 of the metallic sheath 18b1 to the charging current Ib1 flowing along the grounding line CB1 in the grounding direction and the other end 18b12 of the metallic sheath 18b1, The charge current Ia32 flowing along the cross-bonding line CB7 flows toward the charge current Ic21 flowing along the bonding line CB3 and the other end 18c22 of the metal sheath 18c2. That is, the sheath circulation current J5 measured at the point S5 is expressed by the following equation (13).

&Quot; (13) "

J5 = Isc2 + Ib1 + Ic21 + Ia32

The charge current Ib12 flowing along the cross-bonding line CB3 toward the metal sheath 18c2 at the other end 18b12 of the metal sheath 18b1 at the point S6, the charge current Ib12 flowing along the cross- The charge current Ia32 flowing along the cross-bonding line CB7 flows toward the other end 18c22 of the metal sheath 18c2 toward the charge current Ic21 flowing along the cross-bonding line CB3 toward the capacitor 18b12. That is, the sheath circulating current J6 measured at the point S6 is given by the following equation (14).

&Quot; (14) "

J6 = Isc2 + Ib12 + Ic21 + Ia32

The operation unit 1110 can subtract the sheath circulation current J5 measured at the point S5 and the sheath circulation current J6 measured at the point S6.

&Quot; (15) "

J5-J6 = (Isc2 + Ib1 + Ic21 + Ia32) - (Isc2 + Ib12 + Ic21 + Ia32) = Ib1-Ib12

Since the charging current Ib12 is different in direction from the charging current Ib1 and the magnitude thereof is the same, Ib1-Ib12 derived from the subtraction result is the metal sheath of the power cable located in the first section L1 of the B-phase transmission line Corresponds to the charging current value flowing through the first switch 18b1. The extraction unit 1120 extracts the third harmonic current from the charge current derived by the calculation unit 1110 and the analysis unit 1130 analyzes the third harmonic current to determine the insulation deterioration of the power cable Can be diagnosed.

12 is a diagram for explaining a process of calculating a charge current flowing through the metal sheath 18c2 after measuring the sheath circulation current at S6 and S7.

12, one insulated deterioration diagnosis device for three-phase transmission line is connected to the point S6 to measure the sheath circulation current, and another insulated deterioration diagnosis device for the three-phase transmission line is connected to the point S7, Measure the circulating current.

The point S6 is a point on the cross-bonding line CB3 connected to the one end 18c21 of the metal sheath 18c2 and the point S7 is a point on the cross-bonding line CB6 connected to the other end 18c22 of the metal sheath 18c2. May be a single point.

The charge current Ib12 flowing along the cross-bonding line CB3 toward the metal sheath 18c2 at the other end 18b12 of the metal sheath 18b1 at the point S6, the charge current Ib12 flowing along the cross- The charge current Ia32 flowing along the cross-bonding line CB7 flows toward the other end 18c22 of the metal sheath 18c2 toward the charge current Ic21 flowing along the cross-bonding line CB3 toward the capacitor 18b12. That is, the sheath circulating current J6 measured at the point S6 is expressed by the following equation (16).

&Quot; (16) "

J6 = Isc2 + Ib12 + Ic21 + Ia32

The charging current Ib12 flowing along the cross-bonding line CB3 toward the metallic sheath 18c2 at the other end 18b12 of the metallic sheath 18b1 at the point S7, the charging current Ib12 flowing through the cross- A charge current Ia32 flowing along the cross-bonding line CB7 flows toward the other end 18c22 of the metal sheath 18c2 toward the charge current Ic23 flowing along the cross-bonding line CB7 toward the capacitor 18a31. That is, the sheath circulating current J7 measured at the point S7 is expressed by the following equation (17).

&Quot; (17) "

J7 = Isc2 + Ib12 + Ic23 + Ia32

The operation unit 1110 can subtract the sheath circulation current J6 measured at the point S6 and the sheath circulation current J7 measured at the point S7, and the result is as shown in the following equation (18).

&Quot; (18) "

J2-J3 = (Isc2 + Ib12 + Ic21 + Ia32) - (Isc2 + Ib12 + Ic23 + Ia32) = Ic21-Ic23

Since the charge current Ic21 is different in direction from the charge current Ic23 and the magnitude thereof is the same, Ic21-Ic23 derived from the subtraction result is the metal sheath of the power cable located in the second section L2 of the C-phase transmission line Corresponds to the charge current value flowing in the first capacitor 18c2. The extraction unit 1120 extracts the third harmonic current from the charge current derived by the calculation unit 1110 and the analysis unit 1130 analyzes the third harmonic current to determine the insulation deterioration of the power cable Can be diagnosed.

FIG. 13 is a diagram for explaining the process of calculating the charge current flowing through the metal sheath 18a3 after measuring the sheath circulation current at the points S7 and S8.

13, one insulated deterioration diagnosis device for three-phase transmission line is connected to the point S7 to measure the sheath circulation current, and another insulated deterioration diagnosis device for the three-phase transmission line is connected to the point S8, Measure the circulating current.

The point S7 is a point on the cross-bonding line CB7 connected to one end 18a31 of the metal sheath 18a3 and the point S8 is a point on the ground line CB8 connected to the other end 18a32 of the metal sheath 18a3. Lt; / RTI >

The charging current Ib12 flowing along the cross-bonding line CB3 toward the metallic sheath 18c2 at the other end 18b12 of the metallic sheath 18b1 at the point S7, the charging current Ib12 flowing through the cross- A charge current Ia32 flowing along the cross-bonding line CB7 flows toward the other end 18c22 of the metal sheath 18c2 toward the charge current Ic23 flowing along the cross-bonding line CB7 toward the capacitor 18a31. That is, the sheath circulating current J7 measured at the point S7 is expressed by the following equation (17).

&Quot; (17) "

J7 = Isc2 + Ib12 + Ic23 + Ia32

The charge current Ib12 flowing along the cross-bonding line CB3 toward the metal sheath 18c2 at the other end 18b12 of the metal sheath 18b1 at the point S8, the charging current Ib12 flowing through the cross- A charge current Ic23 flowing along the cross-bonding line CB7 and a charge current Ia3 flowing along the ground line CB8 from the other end 18a32 of the metal sheath 18a3 toward the capacitor 18a31. That is, the sheath circulating current J8 measured at the point S8 is given by the following equation (18).

&Quot; (18) "

J8 = Isc2 + Ib12 + Ic23 + Ia3

The operation unit 1110 can subtract the sheath circulation current J7 measured at the point S7 and the sheath circulation current J8 measured at the point S8.

&Quot; (19) "

J7-J8 = (Isc2 + Ib12 + Ic23 + Ia32) - (Isc2 + Ib12 + Ic23 + Ia3) = Ia32-Ia3

Since the charging current Ia32 is different in direction from the charging current Ia3 and the magnitude of the charging current Ia3 is the same, Ia32-Ia3 derived from the subtraction result is the metal sheath of the power cable located in the third section L3 of the A- Corresponds to the charging current value flowing in the charging circuit 18a3. As described above, the charging current derived by the calculating unit 1110 is obtained by extracting the third harmonic current from the extracting unit 1120 and analyzing the third harmonic current by the analyzing unit 1130 to diagnose the insulation deterioration of the power cable .

FIG. 14 is a diagram for explaining the process of calculating the charge current flowing through the metal sheath 18c1 after measuring the sheath circulation current at S9 and S10.

14, one insulated deterioration diagnosis apparatus for three-phase transmission line is connected to the point S9 to measure the sheath circulation current, and another insulated deterioration diagnosis apparatus for three-phase transmission line is connected to the point S10, Measure the circulating current.

The point S9 is a point on the ground line CB1 connected to the one end 1c11 of the metal sheath 18c1 and the point S9 is a point on the crossing line CB3 connected to the other end 18c12 of the metal sheath 18c1. Lt; / RTI >

A charge current Ic1 flowing along the grounding line CB1 in the grounding direction from one end 18c11 of the metal sheath 18c1 toward the other end 18c12 of the metal sheath 18c1 at the point S9, A charge current Ib32 flowing along the cross-bonding line CB5 flows toward the charge current Ia21 flowing along the bonding line CB3 and the other end 18b22 of the metal sheath 18b2. That is, the sheath circulation current J8 measured at the point S9 is expressed by the following equation (20).

&Quot; (20) "

J8 = Isc3 + Ic1 + Ia21 + Ib32

The charge current Ic12 flowing along the cross-bonding line CB3 toward the metal sheath 18a2 at the other end 18c12 of the metal sheath 18c1 at the point S10, the charge current Ic12 flowing through the cross- The charge current Ib32 flowing along the cross-bonding line CB5 flows toward the other end 18a22 of the metal sheath 18a2 and the charge current Ia21 flowing along the cross-bonding line CB3 toward the capacitor 18c12. That is, the sheath circulation current J9 measured at the point S9 is expressed by the following equation (21).

&Quot; (21) "

J9 = Isc3 + Ic12 + Ia21 + Ib32

The operation unit 1110 can subtract the sheath circulation current J8 measured at the point S9 and the sheath circulation current J9 measured at the point S10, and the result is as shown in the following equation (22).

&Quot; (22) "

J8-J9 = (Isc3 + Ic1 + Ia21 + Ib32) - (Isc3 + Ic12 + Ia21 + Ib32) = Ic1-Ic12

Since the charge current Ic12 is different in direction from the charge current Ic1 and the size thereof is the same, Ic1-Ic12 derived from the subtraction result is a metal sheath of the power cable located in the first section L1 of the C-phase transmission line Corresponds to the charge current value flowing in the first capacitor 18c1. The extraction unit 1120 extracts the third harmonic current from the charge current derived by the calculation unit 1110 and the analysis unit 1130 analyzes the third harmonic current to determine the insulation deterioration of the power cable Can be diagnosed.

FIG. 15 is a diagram for explaining a process of calculating the charge current flowing through the metal sheath 18a2 after measuring the sheath circulation current at the points S10 and S11.

15, one insulated deterioration diagnosis device for three-phase transmission line is connected to the point S10 to measure the sheath circulation current, and another insulated deterioration diagnosis device for the three-phase transmission line is connected to the point S11, Measure the circulating current.

The point S10 is a point on the cross-bonding line CB3 connected to one end 18a21 of the metal sheath 18a2 and the point S11 is a point on the cross-bonding line CB5 connected to the other end 18a22 of the metal sheath 18a2. May be a single point.

The charge current Ic12 flowing along the cross-bonding line CB3 toward the metal sheath 18a2 at the other end 18c12 of the metal sheath 18c1 at the point S10, the charge current Ic12 flowing through the cross- The charge current Ib32 flowing along the cross-bonding line CB5 flows toward the other end 18a22 of the metal sheath 18a2 and the charge current Ia21 flowing along the cross-bonding line CB3 toward the capacitor 18c12. That is, the sheath circulation current J9 measured at the point S10 is expressed by the following equation (23).

&Quot; (23) "

J9 = Isc3 + Ic12 + Ia21 + Ib32

The charge current Ic12 flowing along the cross-bonding line CB3 toward the metal sheath 18a2 at the other end 18c12 of the metal sheath 18c1 at the point S11, the charge current Ic12 flowing through the cross- A charge current Ib32 flowing along the cross bonding line CB5 flows toward the other end 18a22 of the metal sheath 18a2 and the charge current Ia23 flowing along the cross-bonding line CB5 toward the capacitor 18b31. That is, the sheath circulation current J10 measured at the point S11 is expressed by the following equation (24).

&Quot; (24) "

J10 = Isc3 + Ic12 + Ia23 + Ib32

The operation unit 1110 can subtract the sheath circulation current J9 measured at the point S10 and the sheath circulation current J10 measured at the point S11, and the result is as shown in the following equation (25).

&Quot; (25) "

J9-J10 = (Isc3 + Ic12 + Ia21 + Ib32) - (Isc3 + Ic12 + Ia23 + Ib32) = Ia21-Ia23

Since the charging current Ia21 is different in direction from the charging current Ia23, Ia21-Ia23 derived from the subtraction result is the metal sheath of the power cable located in the second section L2 of the A-phase transmission line A? Corresponds to the charging current value flowing in the first capacitor 18a2. The extraction unit 1120 extracts the third harmonic current from the charge current derived by the calculation unit 1110 and the analysis unit 1130 analyzes the third harmonic current to determine the insulation deterioration of the power cable Can be diagnosed.

FIG. 16 is a diagram for explaining the process of calculating the charge current flowing through the metal sheath 18b3 after measuring the sheath circulation current at the points S11 and S12.

Referring to FIG. 16, one insulated deterioration diagnosis device for three-phase transmission line is connected to the point S11 to measure the sheath circulation current, and another insulated deterioration diagnosis device for the three-phase transmission line is connected to the point S12, Measure the circulating current.

The point S11 is a point on the cross-bonding line CB5 connected to the one end 18b31 of the metal sheath 18b3 and the point S12 is a point on the ground line CB8 connected to the other end 18b32 of the metal sheath 18b3. Lt; / RTI >

The charge current Ic12 flowing along the cross-bonding line CB3 toward the metal sheath 18a2 at the other end 18c12 of the metal sheath 18c1 at the point S11, the charge current Ic12 flowing through the cross- A charge current Ib32 flowing along the cross bonding line CB5 flows toward the other end 18a22 of the metal sheath 18a2 and the charge current Ia23 flowing along the cross-bonding line CB5 toward the capacitor 18b31. That is, the sheath circulation current J10 measured at the point S11 is expressed by the following equation (26).

&Quot; (26) "

J10 = Isc3 + Ic12 + Ia23 + Ib32

The charging current Ic12 flowing along the cross-bonding line CB3 toward the metallic sheath 18a2 at the other end 18c12 of the metallic sheath 18c1 at the point S12, The charge current Ib3 flowing along the cross-bonding line CB5 and the charge current Ib3 flowing along the ground line CB8 at the other end 18b32 of the metal sheath 18b3 flow toward the capacitor 18b31. That is, the sheath circulating current J11 measured at the point S12 is expressed by the following equation (27).

&Quot; (27) "

J11 = Isc3 + Ic12 + Ia23 + Ib3

The operation unit 1110 can subtract the sheath circulation current J10 measured at the point S11 and the sheath circulation current J11 measured at the point S12, and the result is as shown in the following equation (28).

&Quot; (28) "

J10-J11 = (Isc3 + Ic12 + Ia23 + Ib32) - (Isc3 + Ic12 + Ia23 + Ib3) = Ib32-Ib3

Since the charge current Ib32 is different in direction from the charge current Ib3 and the magnitude thereof is the same, Ib32-Ib3 derived from the subtraction result is the metal sheath of the power cable located in the third section L3 of the B-phase transmission line Corresponds to the charge current value flowing in the second transistor 18b3. As described above, the charging current derived by the calculating unit 1110 is obtained by extracting the third harmonic current from the extracting unit 1120 and analyzing the third harmonic current by the analyzing unit 1130 to diagnose the insulation deterioration of the power cable .

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments.

The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

1000: Diagnosis device for insulation with three-phase transmission line
1100:
1120:
1130:
1400: GPS unit
1500:
1600:

Claims (16)

A method for diagnosing insulation deterioration of a three-phase transmission line in which divided power cables are connected by a connection box and metal sheaths of the power cables are cross-bonded, the method comprising:
Performing time synchronization of a plurality of insulation degradation diagnostic apparatuses capable of measuring a sheath circulating current flowing along a path formed by the metal sheath and the cross bonding;
Simultaneously measuring the sheath circulation currents at both ends of the power cable on a path through which the sheath circulating current flows;
Calculating a charge current in the power cable by synthesizing the sheath cyclic current measured at both ends of the power cable;
Obtaining a third harmonic current of the charging current; And
Analyzing the third harmonic current to determine whether there is insulation deterioration in the power cable; Wherein the insulation deterioration diagnosis method comprises the steps of: The method according to claim 1,
Wherein the time synchronization step comprises:
Characterized in that each of the plurality of insulation deterioration diagnosis apparatuses arranged so as to be spaced apart from each other has the same measurement start time at which the measurement of the sheath circulation current starts and the measurement end time at which the measurement of the sheath circulation current ends, A method for diagnosing insulation degradation in a semiconductor device. The method according to claim 1,
Each of the plurality of insulation degradation diagnostic apparatuses includes a GPS unit,
Wherein the GPS unit time-synchronizes the plurality of insulation deterioration diagnostics devices using a GPS signal. The method according to claim 1,
The step of simultaneously measuring the sheath circulating current includes:
At least two of said insulation deterioration diagnosing devices are connected to each of said connection cages disposed at both ends of said power cable on a path through which said sheath circulating current flows to simultaneously measure said sheath circulating current flowing through said connection cage Insulated deterioration diagnosis method for a three-phase transmission line. The method according to claim 1,
Wherein the sheath circulation current measured by the plurality of insulation deterioration diagnosing devices arranged apart from each other is transmitted and received between the insulation deterioration diagnosing devices. The method according to claim 1,
Wherein a sensor section is disposed on a cross-bonding line for cross-bonding the power cables constituting the three-phase transmission line, and the sheath circulation current is measured by the sensor section. The method according to claim 1,
Wherein the sheath circulation current includes a sheath induction current and a charge current,
The sheath induction current is a current flowing along the metal sheath and the cross-bonding line by a sheath induction voltage induced by a conductor current flowing in the conductor of the power cable,
Wherein the charging current includes a capacitive leakage current and a conductive leakage current flowing between the conductor and the metal sheath. 8. The method of claim 7,
Wherein the charging current is obtained by subtracting the sheath circulating current measured at one end of the power cable and the sheath circulating current measured at the other end of the power cable. The method according to claim 1,
And determining that there is insulation deterioration when the third harmonic current is greater than or equal to a predetermined value. An insulation deterioration diagnosis apparatus for a three-phase transmission line in which divided power cables are connected by a connection box and metal sheaths of the power cables are cross-bonded,
A GPS unit for performing time synchronization between the plurality of insulation deterioration diagnostics devices spaced apart from each other;
A sensor unit for measuring a sheath circulating current flowing along a cross-bonding line connected to one end of the power cable;
A communication unit for transmitting and receiving the measured sheath circulating current value between the insulation degradation diagnosis apparatuses disposed apart from each other; And
A controller for combining the measured sheath circulation current and the received sheath circulation current to derive a charging current of the power cable and diagnosing insulation deterioration of the power cable by extracting a third harmonic current of the charging current; Wherein the insulation deterioration diagnosis device comprises: 11. The method of claim 10,
Wherein the GPS unit makes the measurement start time at which each of the plurality of insulation deterioration diagnosis apparatuses arranged to be apart from each other start to measure the sheath circulation current and the measurement end time at which measurement of the sheath circulation current ends, Insulation degradation diagnosis device for three - phase transmission line. 11. The method of claim 10,
At least two of said insulation deterioration diagnosis devices are connected to each of said connection cages disposed at both ends of said power cable on a path through which said sheath circulating current flows to simultaneously measure said sheath circulating current flowing through said connection cage Insulated deterioration diagnosis device for a three-phase transmission line. 11. The method of claim 10,
Wherein the sheath circulation current includes a sheath induction current and a charge current,
The sheath induction current is a current flowing along the metal sheath and the cross-bonding line by a sheath induction voltage induced by a conductor current flowing in the conductor of the power cable,
Wherein the charging current includes a capacitive leakage current and a conductive leakage current flowing between the conductor and the metal sheath. 14. The method of claim 13,
Wherein the charging current is obtained by subtracting the sheath circulating current measured at one end of the power cable and the sheath circulating current measured at the other end of the power cable. 11. The method of claim 10,
Wherein the controller extracts the third harmonic current by Fourier analysis of the charge current derived from the sheath circulation current measured at both ends of the power cable. 11. The method of claim 10,
Wherein the controller determines that there is insulation deterioration when the third harmonic current is equal to or greater than a predetermined value.

Images