KR20080017801A - A distinguishable device of fault locating for distribution line - Google Patents

Abstract

A fault site distinguishing device of a distribution line is provided to consume harmonics flowing in a center line by utilizing the rectified power as power for a lamp and to protect various relays connected to a neutral line by increasing resistance of the neutral line. In a fault site distinguishing device of a distribution line, zero current transformers(Z-CT,10) are installed on a neutral line connecting a three-phase AC(Alternating Current) power source and a load of a three-phase and four-line type power system, at regular intervals in order to detect harmonics and zero current flowing in the neutral line. A rectifying unit(20) rectifies harmonic components of the neutral line detected by the zero current transformers, into DC(Direct Current) current. A charging unit(40) charges a battery(50) with the DC current rectified in the rectifying unit. A fault current sensing unit(25) judges the polarity of secondary voltage of the zero current transformers of the neutral line by detecting a wavelength of the zero current flowing in the neutral line of the distribution line, and changes the flow direction of the zero current into the direction of (+,-) or (0,1). A pair of lamps displays the flow direction of the image fault current discriminated in the fault current sensing unit, as colors corresponding to the direction of (+,-) or (0,1) by power of the battery charged in the charging unit.

Description

A distinguishable device of Fault Locating for distribution line

1 is a conceptual diagram of a failure point on-site identification device of a distribution line according to the present invention.

2 is a conceptual diagram showing an equivalent circuit of a failure point spot identification device of a distribution line according to the present invention.

3 is a conceptual diagram showing an accident point of a failure point on-site identification device of a distribution line according to the present invention.

The present invention relates to an apparatus for visually detecting a point of failure of a distribution line.

As is well known, a distribution line that supplies power from a substation to a customer is composed of complex trunks and branch lines, because unlike a transmission line, power is required to supply a large number of customers each. Therefore, if a ground fault (when the wire is broken and grounded) or a short circuit (when other wires are stuck) occurs on the distribution line and a fault current occurs, find the location of the fault point where the accident occurred. It takes a lot of effort.

Conventionally, when a fault current occurs in a distribution line, a substation breaker operates to find a fault point where a fault current has occurred, and the operator and the substation manager in the field mainly exchange information about the accident point using communication means. Finding faults has been a common practice.

However, in the case of the above method, a lot of time and manpower is consumed, and as the recovery time is long, the power failure time is prolonged, which causes a lot of inconveniences for power consumers. Accordingly, there has been a demand for a method of improving the reliability of the power supply and the quality of service for the customer by shortening the power failure time by quickly identifying and restoring the location of the failure point in the event of an accident of the wiring line.

The power distribution method of our country is a three-phase four-wire multi-ground system, in case of a ground fault, the ground current flowing through the neutral wire may be greater than the short circuit current. In a typical substation system, a line automatic switchgear is installed at a branch point or a customer entrance with a load capacity of 4000 [kVA] or less.

In case of a ground fault, the automatic line breaker cooperates with a circuit breaker of a substation and a recloser (RECLOSER), a line open / close control device installed on a distribution line, to prevent the expansion of the fault section by quickly and accurately blocking or opening only the fault section. Minimize that damage.

As described above, when an error occurs in a distribution line and a fault current is sensed, a device for separating and blocking a fault point at which the fault current has occurred includes a breaker, a switch, a recloser. Hereinafter, the function will be outlined.

The circuit breaker (CB) may open or close the line when a very large fault current is detected from the distribution line. In addition, if necessary, the line can be opened and closed even in the normal current flow.

Unlike breakers, a load break switch (LBS) means a device that can open and close a line only when no current flows or a normal current flows, and cannot open or close a line when a fault current occurs. The switch may be provided with a kind of control unit called a Feeder Remote Terminal Unit (FRTU) for controlling its operation. In other words, FRTU is connected to the mechanical unit of the switchgear is a device for controlling the opening and closing of the line of the switchgear. However, FRTU does not control the mechanism by judging the opening and closing of the line through the switch, and can control the mechanism by receiving a command from the host (main control device) through the communication function.

Recloser is a special type of breaker that recloses the track. If a fault current is detected from the power distribution line and continues for a certain range, the recloser opens the line and closes the line again after a predetermined time. If the fault current is still detected after the line is closed, the recloser repeats the above line reclose process for a predetermined number of times, and if the fault current continues after that, the line is completely opened and no further reclose operation is performed. .

However, when a line breakdown occurs in a distribution line, the switch is turned off at the discretion of the distribution management system 400 or the person in charge of the operation room, or according to the automatic separation program of the distribution line failure section. It will work to put the switch in.

Currently, the automatic disconnection section of the distribution line is programmed, but it cannot be activated. There are many variables depending on the magnitude of the fault current, the place of the accident, the cause of the accident, and the local characteristics.

Therefore, it is inevitable that the fault section judgment time of the person in charge of the distribution distribution management system or distribution operation room is inevitable.

Lack of education and accidents by simulation do not happen all the time, so humans sometimes delay the separation time of failure section by human error.

This is a limitation of the conventional method of detecting only the magnitude of the fault current to date.

The present invention has been proposed to solve the above problems,

First, the object of the present invention is to utilize the electric current flowing in the middle line as a power source for roadside lighting.

Secondly, when a fault current is generated by using the harmonics flowing in the neutral line, the flow direction of the fault current is made to light on the LED lamp for a predetermined time, so that an accident occurrence point can be easily recognized in the field.

In order to achieve the above object, an apparatus for identifying a failure point of a distribution line according to the present invention is installed on a neutral line at a predetermined interval on a neutral line connecting a three-phase AC power supply and a load of a three-phase four-wire power system. An image current transformer (Z-CT) for detecting flowing harmonics and image fault currents; A rectifier for rectifying a harmonic component flowing through the neutral line detected by the image current transformer to a DC voltage; A charging unit configured to charge the battery using the DC current rectified by the rectifying unit; By detecting the wavelength of the image fault current flowing through the neutral line n of the distribution line and discriminating the polarity of the secondary voltage of the image transformer Z-CT of the neutral line, the direction of the determined image fault current flows is (+, -) Or fault current detection unit for converting to (0, 1); And a direction in which the image fault current determined by the fault current detector by the power of the battery charged by the charging unit flows in a color corresponding to (+,-) or (0, 1), respectively. It is characterized by including a pair of lamps.

Hereinafter, a detailed configuration of the present invention will be described with reference to the accompanying drawings.

The lighting lamp using the neutral current according to the present invention is basically an image transformer 10, a rectifier 20, a fault current detector 25, an overvoltage detector 30, a charger 40, a battery 50, a lamp ( 60).

The image current transformer 10 is installed on a neutral line 100 to detect a current flowing on the neutral line. The image current transformer 10 generally includes a cylindrical iron core or a permanent magnet in which a circular hole is formed. It is a kind of transformer that transforms the secondary coil for current detection and penetrates the power line with its circular hole to convert current flowing through the power line into small current on the secondary side by magnetic conversion.

Therefore, when the image current transformer 10 senses and detects a harmonic current flowing through the neutral line 100, the rectifier 20 is provided to rectify the DC current.

The rectifier 20 is provided with a rectifier circuit for converting harmonic current flowing from the image transformer 10 into a direct current through half-wave or full-wave rectification, and the rectifier is preferably for preventing overcharging of the charging unit. First and second zener diodes (not shown) and a bridge circuit (not shown) for rectifying an alternating current into a direct current.

Since the configuration of the rectifier 20 as described above is a known technique, detailed description thereof will be omitted.

The fault current detecting unit 25 detects the wavelength of the image fault current flowing through the neutral line n of the distribution line and discriminates the polarity of the secondary voltage of the image transformer Z-CT of the neutral line, thereby determining the image fault. It converts the direction of current flow into (+,-) or (0, 1).

In this case, the voltage output from the rectifying view 20 is stabilized and output, and when the output voltage rises above a predetermined value, an overvoltage detection unit 30 for outputting an overvoltage prevention signal corresponding thereto is provided.

The overvoltage detector 30 includes resistors R1, R2, and R5 having one terminal connected to an output terminal of the rectifier, a photodiode PD having an anode terminal connected to the other terminal of the resistor R1, and a cathode terminal. Zener diode (ZD1) connected to the cathode terminal of the photodiode (PD) and the anode terminal is grounded, one terminal is connected to the resistor (R3), the anode terminal is connected to the gate terminal of the thyristor (CR1) and the other terminal Is a grounded resistor (R4), a cathode terminal is connected to the other terminal of the resistor (R5) Zener diode (ZD2), one terminal is connected to the anode terminal of the zener diode (ZD2), the other terminal is grounded capacitor By using a known technique consisting of (C2) it is detected that the voltage of the rectifier is excessively increased.

The overvoltage detecting unit 30 separately includes a switching unit (not shown) for blocking and forming a transmission path of the voltage applied from the rectifying unit 20 to the charging unit 40 according to the overvoltage prevention signal output from the overvoltage detecting unit. Can be configured.

The charging unit 40 serves to charge the battery 50 by transforming the power supplied from the rectifying unit.

The battery 50 is preferably made of a rechargeable battery that can be recharged after use.

The secondary battery is charged from the charging unit and serves to supply power to the lamp.

The secondary battery may preferably be any one of a nickel-metal hydride (NI-MH) battery, a nickel cadmium cell, a lithium-ion battery, and a plate battery. The secondary battery may be a built-in battery or a battery that can be inserted and removed by a user.

The battery 50 may be implemented as a high pressure capacitor instead of a secondary battery. In the case of the secondary battery, the internal battery is gradually oxidized by electrolysis, and an oxide film is formed when charging and discharging continue to some extent. To overcome the shortcomings of the end of life, not only instantaneous charging is possible due to the characteristics of the capacitor, there is a semi-permanent advantage of life due to charging and discharging.

When the battery 50 is charged by the charging unit 40 as described above, the lamp is driven through the charged power.

The lamp 60 here preferably consists of red (LED lamp A) and green (LED lamp B).

When the fault current occurs, the lamp 60 makes the LED lamp light for a predetermined time by using a timer provided separately for the flow direction of the fault current so as to easily recognize an accident occurrence point in the field.

That is, the fault current detecting unit 25 determines the polarity of the secondary voltage of the image current transformer Z-CT of the neutral line by detecting the wavelength of the image fault current flowing through the neutral line n of the distribution line. It plays a role to convert the direction of video fault current to (+,-) or (0, 1).

Accordingly, if the polarity of the fault current is + according to the direction in which the video fault current determined by the fault current detection unit 25 flows, the LED lamp A is turned on, and if the polarity of the fault current is-LED lamp B If the LED lamp color corresponding to the power supply is red from the circuit failure point, the other LED lamp color of the fault line is green, and the site maintenance worker changes the color of the LED lamp from the power supply, that is, red. If you follow the track to the end of the ramp, you will be able to identify and dispatch the accident.

Hereinafter, the operation of the site identification device for the failure point of the distribution line according to the present invention.

If a ground fault, lightning strike, interline, disconnection, or line load imbalance occurs, current flows through the common neutral line (N).

In the present invention, the position of the current flowing through the neutral line N, that is, the direction of the current flowing to the power supply side and the direction of the current flow to the load side, are used differently from the position where the accident occurs.

Referring to the equivalent circuit shown in Figure 2 as follows.

When the secondary voltage of the image transformer (Z-CT) installed on the neutral line (N) is measured, if the output voltage of the image transformer (Z-CT) on the power supply side is + V from the point of occurrence of a line accident, the image transformer (Z-) on the load side CT) output voltage is -V.

Therefore, when the fault current detecting unit 25 determines the polarity of the secondary voltage of the image current transformer Z-CT and finds a point where the polarity is changed, this part may be regarded as the occurrence position of the line accident.

As shown in FIG. 3, when all of the secondary voltage polarities of the image current transformer ZCT sensed by the fault current detection unit 25 are expressed, the line accident point can be easily found. ) It is easier to find the voltage data and the negative voltage data in different lamp colors, ie red or green.

It is also effective to use a half cycle (1 / 2HZ) output at which a fault current begins to occur.

Since it is common ground, the current of neutral wire (N) is detected in other lines, but even if it is weak current and the polarity (+/-) is partially changed, the polarity is changed all over the line by clearly distinguishing the power side and load side as in the accident point. What you do does not appear.

Since only positive (+/-) voltage polarity is important for locating the line accident in the present invention, it is advantageous that the image current transformer (Z-CT) is designed to be saturated with iron core core so that secondary voltage is not output excessively. Do.

5 is a diagram illustrating an example of voltage polarity of the image current transformer Z-CT installed in the neutral line N. Referring to FIG.

As described above, in case of ground fault or interline contact, the incident point can be detected by tracking the inflow direction of the neutral current of the line operated by OCR (Over Current Relay) installed in the substation. Since the fault current detection unit 25 of a nearby substation (S / S; Sub Station) operates from one to several, the lightning point can be detected by tracking the inflow direction of the neutral current for each line.

In this case, the positive polarity indicates a forward direction in which the fault current to the fault current detection unit 25 flows (lamp color green), and the negative polarity indicates a fault along the common ground line (N). It is the direction in which the current is distributed (lamp color red). In other words, if the polarity of the image transformer (Z-CT) closest to the substation starts with (+), the green lamp is traced along the line and the next image transformer (Z-CT) is located at the branch point. If the polarity has two green lamps and two red lamps, the point of accident is the point where the green lamp keeps tracking and turns from green lamp to red lamp.

In other words, if you follow the track to the end of the red lamp, you can check the accident location and dispatch.

According to the present invention by the above configuration,

First, the present invention is installed on the neutral wire (neutral) to detect the current flowing in the neutral wire using an image rectifier, rectifying it by using a rectifier, and charge the rectified power to flow to the neutral wire by utilizing as a power source of the lamp By consuming harmonics and increasing the resistance of the neutral wire itself, it is possible to protect various relays connected to the neutral wire, which has the effect of utilizing this as a power source for a street lamp.

Second, when the fault current is generated using the harmonics flowing through the neutral line, the flow direction of the fault current is turned on the LED lamp for a predetermined time, thereby making it easy to recognize an accident occurrence point in the field.

Claims (2)

An image current transformer (Z-CT) installed at a predetermined interval on a neutral line connecting a three-phase AC power source and a load of a three-phase four-wire power system to detect harmonics and image fault currents flowing on the neutral line; A rectifier for rectifying a harmonic component flowing through the neutral line detected by the image current transformer to a DC voltage; A charging unit configured to charge the battery using the DC current rectified by the rectifying unit; By detecting the wavelength of the image fault current flowing through the neutral line n of the distribution line and discriminating the polarity of the secondary voltage of the image transformer Z-CT of the neutral line, the direction of the determined image fault current flows is (+, -) Or fault current detection unit for converting to (0, 1); And A pair of indicators indicating the direction in which the video fault current determined by the fault current detector by the power of the battery charged in the charging unit is distinguishable by a color corresponding to (+,-) or (0, 1), respectively. Point of failure identification site of the distribution line, characterized in that it comprises a lamp. The method of claim 1, Device for identifying the failure point of the distribution line characterized in that it further comprises an overvoltage detector for stabilizing and outputting the voltage output from the rectifier, and outputs an overvoltage protection signal corresponding to the output voltage rises above a predetermined value.

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