KR20160074987A - Live line cable insulation monitoring apparatus - Google Patents

Abstract

The present invention relates to a live wire cable insulation monitoring apparatus monitoring an insulation status of a live wire cable by detecting a leakage current which flows between an earth ground and a sheath ground line which is connected to the live wire cable, by, in an overlapped manner, applying a direct current signal voltage to a power bus bar of a commercial alternate current voltage in a live wire state. The apparatus comprises: a sheath current detection unit detecting a sheath current which flows between the earth ground and the sheath ground line.

Description

{LIVE LINE CABLE INSULATION MONITORING APPARATUS}

The present invention relates to an apparatus for monitoring an insulation state of a live cable by superimposing a DC signal voltage on a commercial AC voltage system bus line in a live state, that is, in a live state, And more particularly to a live cable insulation sensing device for monitoring the status of a live cable.

In the case of high-voltage or higher-power cables, not only insulation failure breakdown but also heat generation due to contact with the metal structure of the sheath ground wire at the portion of the straight connecting part corresponding to the failure of the sheath layer, A circulation current flows and a cable accident occurs due to heat generation and disconnection of the copper tape and deterioration due to penetration of moisture in the skin damaged portion.

Fig. 1 is a schematic view of a live cable insulation monitoring apparatus 4 for explaining the present invention and a conventional live cable insulation monitoring apparatus 4. As shown in Fig.

N cables (11, 12, 13) to be insulated and monitored through the transformer (2) and the system bus (1, BUS) . 1, the neutral point of the secondary winding Y of the transformer 2 is connected to the earth ground 7 via a disconnecting switch 5 and a neutral grounding reactor 6 (NGR) Grounded grounding system of the general resistance grounding type is shown in the figure but the direct grounding system in which the resistance value of the neutral point grounding resistor 6 is zero or the secondary side of the transformer 2 is in the same state as the delta wiring It is of course also applicable to non-grounded systems.

The live cable (11, 12, 13) to be monitored and monitored is in a live state.

A signal voltage applying device 3 for applying a DC signal voltage to the system bus line 1 is provided between the neutral point grounding resistor 6 and the grounding ground 7.

The signal voltage applying device 3 is not shown in FIG. 1, but is generally configured to be controlled by the live cable insulation monitoring device 4. FIG. The sheath ground lines 17, 18 and 19 of the live cables 11, 12 and 13 to be monitored are connected to the active cable insulation monitoring device 4.

In the conventional technology, only the insulation state of the live cable being measured is monitored, and there is a problem that the failure state due to the heat generation phenomenon of the live cable sheath or the circulation current can not be monitored.

Korean Patent Publication No. 10-2004-0087077 (published on October 13, 2004)

The present invention relates to a live cable insulation monitoring apparatus having a function of measuring a sheath ground current in a live state of a power cable having a high-voltage or higher voltage. The live cable insulation monitoring apparatus not only monitors the insulation state of the live cable, The object of the present invention is to detect beforehand the circulation current due to the heating phenomenon due to contact with the metal structure of the sheath ground wire of the cable or the sheath damage.

The solution to the problem of the present invention is not limited to those mentioned above, and other solutions not mentioned can be clearly understood by those skilled in the art from the following description.

A live cable insulation monitoring apparatus according to the present invention has the following problem solving means for solving the above problem.

The live cable insulation monitoring apparatus according to the present invention detects the leakage current flowing between the sheath ground line and the earth ground connected to the live cable by superimposing the DC signal voltage on the system bus of the commercial AC voltage in the live state, Monitor.

The live cable insulation monitoring apparatus according to the present invention may further include a sheath current detector for detecting a sheath current flowing between the sheath ground line and the earth ground.

A live cable insulation monitoring apparatus of the present invention includes a low-pass filter for passing the direct current leakage current, a cable electromagnetic contactor connected to the sheath ground line to be connected to at least one of the low-pass filter and the earth ground, A sheath electromagnetic contactor connected to the current detecting unit to be energized or turned off, and an arithmetic control unit to which the low frequency filter and the sheath current detecting unit are connected.

In the live cable insulation monitoring apparatus of the present invention, the electromagnetic contactor energizes the sheath ground wire to the low-pass filter, the electromagnetic contactor disconnects the sheath ground wire to the earth ground, and the sheath electromagnetic contactor connects the electromagnetic contactor to the sheath current detection section The arithmetic and control unit can measure the sheath current detected by the sheath current detecting unit in the energized state to determine whether the sheath current is leaked or not.

The live cable insulation monitoring apparatus of the present invention may further include a first analog digital conversion unit for connecting the operation control unit and the low pass filter, and a second analog digital conversion unit for connecting the current control unit and the sheath current detection unit.

The operation control unit includes a digital input unit connected to the first analog-to-digital conversion unit and the second analog-to-digital conversion unit, a digital output unit for controlling the cable electromagnetic contactor, the sheath contactor, and the operation unit for controlling the digital input unit and the digital output unit. As shown in FIG.

The live cable insulation monitoring apparatus according to the present invention having the above-described configuration has the following effects.

First, it provides an advantage of measuring the sheath ground current in the live state of the live cable by the live cable insulation monitoring apparatus of the present invention.

Second, it is possible to detect the circulation current due to the skin damage in advance by sensing the sheath current in advance by the live cable insulation monitoring apparatus of the present invention. Thus, it is possible to prevent an accident of a cable caused by a circulating current or the like in advance.

The effects of the present invention are not limited to those mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a connection diagram of a live cable insulation monitoring apparatus for explaining the present invention and a conventional art.
2 is a schematic illustration of a cable for understanding and explaining the present invention.
3 is a diagram showing the entire connection structure of the live cable insulation monitoring apparatus of the present invention.
4 is a flow chart for explaining the operation of the live cable insulation monitoring apparatus of the present invention.

The live cable insulation monitoring apparatus according to the present invention may have various modifications and various embodiments, and specific embodiments will be illustrated in the drawings and described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Hereinafter, a live cable insulation monitoring apparatus 4 according to the present invention will be described in detail with reference to the drawings.

1 is a connection configuration diagram of a live cable insulation monitoring apparatus 4 for explaining the present invention and a conventional art. Fig. 1 is a schematic view of a live cable insulation monitoring apparatus 4 for explaining the present invention and a conventional live cable insulation monitoring apparatus 4. As shown in Fig.

N cables (11, 12, 13) to be insulated and monitored through the transformer (2) and the system bus (1, BUS) are electrically connected to each other through circuit breakers (14, 15, 16, VCB) . 1, the neutral point of the secondary winding Y of the transformer 2 is connected to a disconnecting switch 5 and a neutral grounding reactor 6 (NGR) The earth grounding system of the general resistance grounding type is shown in the figure. However, in the case of the direct earth system in which the resistance value of the neutral point grounding resistor 6 is zero or the secondary side of the transformer 2 is non- It is of course also applicable to the grounding system.

The live cable (11, 12, 13) to be monitored and monitored is in a live state.

A signal voltage applying device 3 for applying a DC signal voltage to the system bus line 1 is provided between the neutral point grounding resistor 6 and the grounding ground 7.

The signal voltage applying device 3 is not shown in FIG. 1, but is generally configured to be controlled by the live cable insulation monitoring device 4. FIG. Sheath ground lines 17, 18, 19 of the live cable 11, 12, 13 to be monitored are connected to the live cable insulation monitoring device 4.

2 is a schematic illustration of a cable for understanding and explaining the present invention.

2 is a view for explaining the live cable in detail. In general, in the high voltage cable, the insulating layer 52 is located between the conductor 51 and the copper shield 53, And the insulating layer local electromotive force 56 generated in the insulator 52 during the deterioration of the insulation are formed.

A mode layer 54 is formed on the outer surface of the copper shield 53. A conventional layered local electromotive force 58 is generated in the anticorrosive layer 54 that occurs in the anticorrosive layer 54 of the anticurrent layer insulation resistor 57 and the anticorrosive layer 54.

Insulating layer local electromotive force (56) The polarity of the system layer local electromotive force (58) depends on the deterioration state of the live cable.

FIG. 3 is a diagram showing the entire connection structure of the live cable insulation monitoring apparatus 4 of the present invention.

The live cable insulation monitoring apparatus 4 of the present invention is a state in which the sheath ground lines 17, 18 and 19 of the live cables 11, 12 and 14 being monitored are connected to the live cable insulation monitoring apparatus 4 of the present invention 18, and 19 are connected to the earth ground for a predetermined period of time before the leakage current for monitoring the insulation state in the sheath ground lines 17, 18, and 19 is measured, and a shear ground current It is possible to prevent an accident of the cable caused by the heat generation phenomenon and the circulation current.

The live cable insulation monitoring device 4 includes cable electromagnetic contactors 21, 22 and 23, an arithmetic control unit 30, a low pass filter (LPF), a first analog to digital conversion unit 26, a second analog-to-digital conversion unit 28, a sheath contactor 24 and a sheath current detection unit 27. The second analog-to-

The cable electromagnetic contactors 21, 22 and 23 are provided such that the sheath ground lines 17, 18 and 19 of the live cables 11, 12 and 13 are energized or de-energized with the low-pass filter 25 or the earth ground 8, respectively. For example, the first cable electromagnetic contactor 21 is configured such that the a-contact F1a and the first live cable 11, which allow the first live cable 11 to be energized or de-energized with the low-pass filter 25, And a b-contact F1b to be energized or de-energized. Any nth n-th cable electromagnetic contactor 23 includes Fna and Fnb contacts.

The low-pass filter 25 passes a direct current leakage current flowing through the sheath ground lines 17, 18 and 19 of the live cables 11, 12 and 13.

The low-pass filter 25 is connected to the a-contacts F1a to Fna of the first to n-th cable electromagnetic contactors 21 to 23.

The sheath current detection unit 27 detects a sheath current flowing between the first sheath ground line 17 and the earth ground 8.

The sheath current detector 27 may be a current transformer (CT).

The sheath electromagnetic contactor 24 can energize or shut off the first cable electromagnetic contactor 21 and the sheath current detector 27.

A low-pass filter (25) and a sheath current detection unit (27) are connected to the operation control unit (30).

The first analog-to-digital converter 26 connects the operation control unit 30 and the low-pass filter 25.

The second analog digital switching unit 28 connects the arithmetic control unit 30 and the sheath current detection unit 27.

The first and second analog digital switching sections 26 and 28 convert an analog signal of the leakage current into a digital signal.

The operation control unit 30 includes a digital input unit 32 and DI connected to the first analog-to-digital converter 26 and the second analog-to-digital converter 28, a first cable electromagnetic contactor 21, A calculator 31 for controlling the digital input 32 and the digital output 33, a storage unit for storing various data including leakage current data, 35 and a display unit 34 for displaying various data.

The digital output unit 33 controls whether or not the a contact and the b contact of the first cable electromagnetic contactor 21 are energized or de-energized. Further, the signal voltage applying device 3 controls the DC signal voltage to be applied to the system bus line 1

The live cable insulation monitoring apparatus 4 measures the sheath current detected by the sheath current detection section 27 by the arithmetic and control section 30 and judges whether current leaks to the outside of the system layer 54 of the live cable. At this time, the electromagnetic contactor 21 energizes the first sheath ground wire 17 to the low-pass filter 25, and the electromagnetic contactor 21 cuts the first sheath ground wire 17 to the earth ground 8, The sheath electromagnetic contactor 24 energizes the electromagnetic contactor 21 to the sheath current detector 27.

4 is a flowchart for explaining the operation of the live cable insulation monitoring apparatus 4 according to the present invention.

FIG. 2 shows an operation procedure of the live cable insulation monitoring apparatus 4 according to an embodiment of the present invention. Hereinafter, an operational procedure of the live cable insulation monitoring apparatus 4 will be described with reference to FIG. 3 and FIG.

Fig. 4 shows judging the sheath current and insulation of n live cables 11, 12, 13. It is also shown that the sheath current and the insulation are judged in order from the first live cable 11 to the nth cable 13. However, the measurement order of the live cable can be changed, and it is also possible to measure any one live cable.

In step 210, the arithmetic and control unit 30 sets the total number of turns to A, and selects the cable to be measured as the first live cable 11. To this end, the arithmetic unit 31 substitutes 1 as an initial value into the variable n and stores it in the storage unit 35. [

In step 220, the arithmetic control unit 30 sets the sheath current reference value. This may be a value preset by the user of the active cable insulation monitoring device 4. And an arbitrary variable B is set for the sheath current reference value.

In step 230, the digital output unit 33 energizes the a-contact Fna of the n-th electromagnetic contactor and cuts off the b-contact Fnb. In the initial state, since n = 1, the a-contact F1a of the first electromagnetic contactor is energized and the b-contact F1b is turned off.

The first sheath ground line 17 connected to the first live cable 11 is connected to the earth ground 8 through a low-pass filter 25. The electric current flowing through the same shield of the first live cable 11 is detected by the insulation layer local electromotive force 56 appearing at the time of deterioration of the insulation layer 52 and the mode layer local electromotive force 58 appearing at the deterioration of the anti- The leakage current starts to flow to the ground through the a contact (F1a) of the first electromagnetic contactor and the low-pass filter (25).

In step 240, the digital output section 33 energizes the sheath magnetic contactor 24. At this time, the first live cable 11 is connected to the sheath current detector 27 through the first sheath ground wire 17, the a contact a1 of the first electromagnetic contactor, and the sheath electromagnetic contactor 24. The sheath current detection unit 27 is connected to the earth ground 8.

In step 250, the sheath current detection unit 27 measures the direct current leakage current, that is, the sheath current, of the commercial traveling part flowing to the earth ground 8 through the first sheath ground line 17. For example, a sheath current of a commercial frequency component flowing in the first sheath ground line 17 appears in the secondary winding of the video current transformer CT. The second analog-to-digital converter (28, ADC2) converts the analog signal of the sheath current appearing in the secondary winding of the image transformer (CT) into a digital signal. The digital signal is stored in the storage unit 35 by the arithmetic unit 31. [

In step 260, the digital output section 33 cuts off the sheath magnetic contactor 24.

In operation 270, the operation unit 31 compares the sheath current reference value B with the sheath current value measured in operation 250, and determines whether the measured sheath current is smaller than the sheath current reference value.

Step 280 is a step executed when the measured sheath current value is smaller than the sheath current reference value. In step 280, the leakage current that flows through the first sheath ground line 17 of the first live cable 11 connected to the low-pass filter 25 passes through the low-pass filter 25 is supplied to the first analog-digital converter 26 The analog leakage current signal is converted into a digital leakage current signal. The digital leakage current signal converted by the first analog-to-digital converter 26 is input to the digital input unit 32 and stored in the storage unit 35 by the computing unit 31. [ At this time, the leakage current value before the signal voltage is applied is stored in the storage unit 35. [

The operation section 31 controls the digital output section 33 and the digital output section 33 controls the signal voltage application device 3 so that the signal voltage application device 3 can control the signal voltage to the system bus line 1 . At this time, the leakage current value after the application of the signal voltage is input to the digital input section 32, and the leakage current value after application of the signal voltage to the storage section 35 is stored.

In step 290, the a contact (F1a) of the first cable electromagnetic contactor (21) is disconnected and the b contact (F1b) is energized.

In step 300, the arithmetic and control unit 30 compares the leakage current value before application of the signal voltage stored in the storage unit 35 with the leakage current value after application of the signal voltage to determine the insulation state. Further, the display unit 34 indicates whether or not it is insulated.

In step 310, the display unit 34 displays the measured sheath current.

In step 270, if the measured sheath current is greater than or equal to the sheath current reference value, step 330 is performed.

In step 330, the digital output section 33 disconnects the a contact of the first electromagnetic contactor. Step 330 is followed by step 310.

In step 320, the operation control unit 30 determines whether the last live cable has been measured. The arithmetic and control unit 30 determines whether the value of the variable n is equal to or greater than the value A, which is the number of cables to be settled. If n < A, the flow advances to step 340.

In step 340, the operation unit 31 calculates n + 1 and stores the value of the new n variable. Then, step 230 is executed again. At this time, the sheath current measurement of the second live cable 12 proceeds from step 230.

That is, steps 230 to 320 are repeated to measure the insulation between the first live cable 11 and the nth live cable 13 and the sheath current.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be appreciated that other embodiments may be easily suggested by adding, modifying, deleting, adding, or the like.

The scope of the present invention is defined by the claims, the parentheses used in the claims are not used for optional limitation but are used for the definite components and the description in parentheses is also interpreted as an essential component .

1 system bus (BUS) 2 transformer
3 Voltage application devices 4 Live cables Surveillance cameras
5 Disconnecting Switch (DS)
6 Neutral Grounding Reactor (NGR)
7 Earth ground 8 Earth ground
11, 12, 13 live cable
14, 15, 16 VCB (Vacuum Circuit Breaker)
17, 18, 19 Sheath ground wire 21 1st cable Magnetic contactor (F1)
22 2nd Cable Magnetic Contactor 23 3rd Cable Magnetic Contactor
24 Sheath Magnetic Contactor (TS) 25 Low Pass Filter (LPF)
27 Sheath current detector, Current transformer (CT)
26 A first analog-to-digital conversion (ADC)
28 second analog digital conversion section
30 Operation Control Unit 31 Operation Unit (CPU)
32 Digital Input (DI) 33 Digital Output (DO)
34 display section 35 storage section
51 conductor 52 insulating layer
53 Copper Shield 54 Type Floor
55 Insulation layer Insulation resistance 56 Insulation layer Local EMF
57 Method layer Insulation resistance 58 Method layer Local EMF

Claims (5)

A live cable insulation monitoring apparatus for monitoring an insulation state of a live cable by detecting a direct current leakage current flowing between a sheath ground line and a ground earth connected to a live cable by superimposing a DC signal voltage on a system bus line of a commercial AC voltage in a live state,
And a sheath current detector for detecting a sheath current flowing between the sheath ground line and the earth ground.
The method according to claim 1,
The live cable insulation monitoring device includes:
A low-pass filter for passing the DC leakage current;
A cable electromagnetic contactor connected to the sheath ground line to be energized or de-energized with at least one of the low-pass filter and the earth ground;
A sheath contactor connected to the cable electromagnetic contactor and the sheath current detector to be energized or de-energized; And
And a calculation controller connected to the low-pass filter and the sheath current detector.
3. The method of claim 2,
The live cable insulation monitoring device includes:
Wherein the electromagnetic contactor energizes the sheath ground wire to the low-pass filter, the electromagnetic contactor disconnects the sheath ground wire to the ground ground, and the sheath electromagnetic contactor applies the electromagnetic contactor to the sheath current detector, Wherein the sheath current detecting unit measures the sheath current detected by the sheath current detecting unit to determine whether or not the sheath current is leaked.
The method of claim 3,
The live cable insulation monitoring device includes:
A first analog-to-digital converter for connecting the operation control unit and the low pass filter; And
And a second analog digital switching unit for connecting the current control unit and the sheath current detection unit to each other.
5. The method of claim 4,
The arithmetic control unit,
A digital input unit connected to the first analog-to-digital converter and the second analog-to-digital converter;
A digital output unit for controlling the cable electromagnetic contactor and the sheath contactor; And
And an operation unit for controlling the digital input unit and the digital output unit.

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