KR100996779B1 - Underground low voltage power distributor and control method thereof - Google Patents

Abstract

The present invention is to provide an underground low voltage distribution box capable of locally blocking only a branch circuit having a ground fault when a ground fault occurs in a branch circuit in an underground low voltage distribution, and is connected to a power supply side according to the present invention, and has a communication unit and a diagnostic control unit. A main breaker comprising a breaker; A circuit breaker electrically connected to the main circuit breaker and including a plurality of wiring breakers; A branch bus bar electrically connected between the main circuit breaker and the power distribution circuit breaker, the branch bus bar being provided for each of R phases, S phases, T phases, and N phases that are grounded; An output unit for supplying power to the load side from each of the circuit breakers, the branch output busbar being provided for each of three phases of R phase, S phase, T phase and N phase grounded; An underground low voltage distribution box installed in the N phase branch output bus bar among the branch output bus bars and including a current transformer for detecting an N phase current and transmitting the current to the main circuit breaker in order to detect a ground fault at the branch output to the load side. This is disclosed.

Underground Distribution Box, Air Circuit Breaker, Overcurrent Relay, N-Phase, Current Transformer

Description

Control method of underground low pressure distribution box and underground low pressure distribution box {UNDERGROUND LOW VOLTAGE POWER DISTRIBUTOR AND CONTROL METHOD THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an underground low voltage distribution box, and more particularly, to a method for controlling an underground low voltage distribution box and an underground low voltage distribution box capable of localizing a power failure by blocking only a branch circuit when a ground fault occurs in a branch circuit.

Underground low voltage distribution boxes are electrical equipment used for the division, branching, and protection of low voltage distribution lines supplied from the transformer side transformer output of the distribution transformer.

As the underground low-pressure distribution box, as an example of the prior art, Korean Utility Model Registration No. 20-0259419 (application date: October 5, 2001; application number: 20-2001-0030384) may be referred to.

However, the underground low-pressure distribution box (hereinafter, abbreviated as distribution box) according to the prior art as proposed by the registration utility model has the following problems.

First, since the distribution box according to the prior art has a configuration in which the secondary side transformer output of the distribution transformer is directly connected to the circuit breaker for branch circuits, an intermediate protection that can first respond to an electrical accident occurring at the distribution transformer side first. Since there is no means, the effects of electrical accidents occurring on the transformer side of the distribution are directly spread to the circuit breaker for branch circuits.

Secondly, the distribution box according to the prior art has a grounding configuration using one common ground terminal for a plurality of branch circuit breakers and there is no means for detecting a ground fault. Therefore, in case of a ground fault, a branch circuit in which a ground fault occurs It is impossible to find out, it is impossible to localize the power outage by blocking only the branch circuit, and there is a problem that it is impossible to block (protection) against ground fault at all.

Third, the distribution box according to the prior art has a problem in that measurement, diagnosis, communication is impossible because there is no means for performing a function of measuring, diagnosing, and communicating a power line between the distribution transformer and the distribution box.

Accordingly, the present invention is to solve the problems of the prior art, the first object of the present invention is to first protect the branch circuit wiring breaker and branch circuit by first responding to the electrical accident occurring on the distribution transformer side. It is to provide a underground low pressure distribution box with the means to do so.

It is a second object of the present invention to provide an underground low voltage distribution box capable of localizing a power failure by finding a branch circuit in which a ground fault occurs and blocking only the branch circuit.

It is a third object of the present invention to provide an underground low voltage distribution box capable of performing functions such as measurement, diagnosis, and communication for a power line between a distribution transformer and a distribution box.

It is a fourth object of the present invention to provide a control method of an underground low voltage distribution box capable of localizing a power failure by finding a branch circuit in which a ground fault occurs and blocking only the branch circuit.

A fifth object of the present invention is to provide a control method of a underground low voltage distribution box that can protect a branch circuit wiring breaker and a branch circuit by breaking a circuit when an abnormal diagnosis and an abnormality occur with respect to a power line between a distribution transformer and a distribution box. will be.

The first object to the third object of the present invention, in the underground low pressure distribution,

A main circuit breaker connected to the power supply side and including one air circuit breaker having a communication section and a diagnostic control section;

A circuit breaker electrically connected to the main circuit breaker and including a plurality of branch circuit wiring breakers;

A branch bus bar electrically connected between the main circuit breaker and the power distribution circuit breaker, the branch bus bar being provided for each of R phases, S phases, T phases, and N phases that are grounded;

An output unit for supplying power to the load side from each of the branch circuit wiring breakers, the branch output bus bar being provided for each of R phase, S phase, T phase, and N phase grounded; And

Underground low pressure according to the present invention, characterized in that the branch output bus bar is installed in the N-phase branch output bus bar, a current transformer for detecting the N-phase current to transmit to the air circuit breaker to detect a ground fault in the branch circuit. By providing a distribution box.

The fourth object of the present invention, in the method of controlling the underground low pressure distribution box,

Installing an N-phase current transformer for detecting neutral phase current individually for each circuit breaker for branch circuits;

Determining whether the ground fault is detected by comparing the neutral phase current detected by the N-phase current transformer with a value of a predetermined reference current; And

When the ground fault is determined in the step of determining whether the ground fault, it can be achieved by providing a control method of the underground low-voltage distribution box according to the invention, comprising the step of tripping the circuit breaker for the branch.

The fifth object of the present invention is to provide a three-phase current transformer for detecting the phase current corresponding to each phase on the three-phase power supply side;

Determining occurrence of abnormal current in a circuit by comparing the three-phase current detected by the three-phase current transformer with a value of a predetermined reference current; And

It can be achieved by providing a method for controlling the underground low voltage distribution box according to the invention, characterized in that it further comprises the step of controlling to cut off the circuit when determining the occurrence of abnormal current on the circuit.

An underground low voltage distribution box according to the present invention includes: a main circuit breaker connected to a power supply side and including one air circuit breaker having a communication unit and a diagnostic control unit; A circuit breaker electrically connected to the main circuit breaker and including a plurality of branch circuit wiring breakers; A branch bus bar electrically connected between the main circuit breaker and the power distribution circuit breaker, the branch bus bar being provided for each of R phases, S phases, T phases, and N phases that are grounded; An output unit for supplying power to the load side from each of the branch circuit wiring breakers, the branch output bus bar being provided for each of R phase, S phase, T phase, and N phase grounded; And a current transformer installed in an N-phase branch output busbar among the branch output busbars and configured to detect an N-phase current and transmit the N-phase current to the air circuit breaker to detect a ground fault in the branch circuit. It can detect the ground fault and determine the ground fault.The main circuit breaker can protect the branch circuit wiring breaker and branch circuit primarily when an accident current occurs on the power supply side, that is, the distribution transformer side. It is effective to obtain a low voltage distribution box possible.

Underground low pressure distribution box according to the invention, the diagnostic control unit of the air circuit breaker,

Since it includes a microcomputer to determine whether the ground fault by comparing the N-phase current provided by the current transformer with a predetermined reference current value, it is possible to determine in which branch circuit a ground fault has occurred.

The underground low voltage distribution box according to the present invention includes a microcomputer which outputs a trip signal to a circuit breaker corresponding to the ground circuit breaker when the diagnostic control unit of the air circuit breaker determines that a ground fault occurs. By outputting a trip signal only during the trip, it is possible to obtain an effect that a power failure due to a ground fault can be localized.

The underground low voltage distribution box according to the present invention further includes a three-phase current detection current transformer for detecting phase currents of R phase, S phase, and T phase, and the diagnostic control unit of the air circuit breaker detects the current transformer for three phase current detection. It is composed of a microcomputer that determines whether to output a trip signal to the tripping mechanism of the air circuit breaker by comparing the three-phase current to a predetermined reference current value, so that the phase currents of the R phase, the S phase, and the T phase are abnormal. When the trip occurrence is determined, the air circuit breaker is tripped, and when the fault current occurs on the secondary side of the power distribution transformer, the fault current is primarily cut off, thereby protecting the branch circuit wiring breaker and the branch circuit.

The control method of the underground low voltage distribution box according to the present invention comprises the steps of providing an N-phase current transformer for detecting the neutral phase current for each circuit breaker for branch circuit, and the predetermined neutral phase current detected by the N-phase current transformer Determining whether there is a ground fault by comparing the value of the reference current and tripping the circuit breaker for the branch when a ground fault is determined in the determining of the ground fault, the branch circuit when the ground fault occurs By outputting a trip signal only to the circuit breaker for the circuit, the trip signal can be localized.

The control method of the underground low voltage distribution box according to the present invention comprises the steps of: installing a three-phase current transformer for detecting the phase current for each phase on the three-phase power supply side, and the value of the reference current predetermined by the three-phase current detected by the three-phase current transformer; Determining the occurrence of abnormal current on the circuit and controlling to cut off the circuit when determining the occurrence of abnormal current on the circuit, and by determining whether or not the current of each phase of the R phase, S phase, T phase abnormal When the current is determined, the circuit is cut off, and when the fault current occurs on the secondary side of the power distribution transformer, the fault current is first cut off, thereby protecting the branch circuit breaker and the branch circuit.

In the control method of the underground low voltage distribution box according to the present invention, the step of determining whether the ground fault and the tripping the circuit breaker for the branch is performed by the over-current relay of the air circuit breaker, so when the ground fault occurs for the branch circuit By outputting a trip signal only to the circuit breaker, the trip can be easily achieved by using an overcurrent relay, which is a control unit of the air circuit breaker, in which a power failure due to a ground fault can be localized.

In the control method of the underground low voltage distribution box according to the present invention, the step of determining the occurrence of abnormal current on the circuit and the step of controlling to cut off the circuit is performed by the overcurrent relay of the air circuit breaker, so that a commercially available air circuit breaker By using the overcurrent relay, which is a control unit of the air circuit breaker, which is available in the market using the overcurrent relay, which is a control part of the controller, it is possible to easily cut off the fault current on the power supply side and to protect the branch circuit side. You can get it.

The object of the present invention and the constitution and effects of the present invention to achieve the same will be more clearly understood by the following detailed description of the preferred embodiment of the present invention with reference to the accompanying drawings.

First, the configuration of the underground low pressure distribution box according to a preferred embodiment of the present invention will be described with reference to FIGS. 1 and 2.

1 is a front view showing the configuration of a underground low pressure distribution box according to a preferred embodiment of the present invention, Figure 2 is a rear view showing the configuration of a underground low pressure distribution box according to a preferred embodiment of the present invention.

1 to 2, the underground low-pressure distribution box 100 according to the present invention is a vertical support (100a, 100a ') and vertical supports (100a, 100a') are provided upright on both sides. It includes an enclosure having horizontal supports (100b, 100b ') provided across the upper and lower sides, respectively. The enclosure includes an intermediate horizontal support (100c) for supporting a main circuit breaker (10) to be described later from the top, the main breaker (10) is installed on the intermediate horizontal support (100c). In FIG. 1 and FIG. 2, reference numeral 100d indicates an upper middle vertical support that vertically partitions an installation space of the main breaker 10. The front and rear of the underground low voltage distribution box 100 are divided based on the insulating plate 100e, and the front of the insulating plate 100e becomes the front of the underground low voltage distribution box 100 and the rear of the insulating plate 100e is the underground low voltage distribution box 100. ) Becomes the rear. On the front surface of the insulating plate 100e, a plurality of circuit breakers 20a, 20b, 20c, and 20d for branch circuits described later are fixedly installed. Four front and rear through holes 100e-1 are provided in the upper part of the insulating plate 100e to allow the branch busbars to be described later to pass back and forth in the number corresponding to the circuit breakers 20a, 20b, 20c, and 20d described below. do.

1 to 2, the underground low voltage distribution box 100 according to the present invention includes one main circuit breaker 10 and a plurality of branch circuit breakers 20a, 20b, 20c, and 20d. Including a feeder circuit breaker, branch busbars 30a, 30b, 30c, 30d, 40a, 40b, 40c, branch output busbars 50a, 50b, 50c, 50d and an N-phase current transformer ( CTa, CTb, CTc, CTd).

The main circuit breaker 10 can be connected to the power supply side, i.e., to the secondary output side of the above-mentioned distribution transformer, and has a communication unit (see symbol 3f in FIG. 5) and a diagnostic control unit (see symbol 3e in FIG. 5). It can be composed of a air circuit breaker.

A plurality of branch circuit breakers 20a, 20b, 20c, and 20d are electrically connected to the main circuit breaker 10 through branch busbars described later. The number of branch circuit wiring breakers 20a, 20b, 20c, and 20d is determined depending on the number of branch circuits.

The branch busbars 30a, 30b, 30c, 30d, 40a, 40b, and 40c electrically connect the main circuit breaker 10 and the distribution circuit breaker, that is, the circuit breakers 20a, 20b, 20c, and 20d for branch circuits. And R phase, S phase, T phase, or three phases or R phase, S phase, T phase, and N phases, and each is composed of an electrical conductor such as, for example, a bar-shaped copper material. Branch busbars 30a, 30b, 30c, 30d, 40a, 40b, 40c are R, S, and T phases connected to extend from the main breaker 10 in the vertical direction at the rear of the underground low pressure distribution box 100, respectively. And extending through the front and rear through holes 100e-1 of the insulating plate 100e-1 from the front of the underground low-pressure distribution box 100 and the N-phase first branch busbars 30a, 30b, 30c, and 30d. And second branch bus bars 40a, 40b, 40c connected to the circuit breakers 20a, 20b, 20c, and 20d for branch circuits. Again, the first branch busbars 30a, 30b, 30c, and 30d are the first R-phase branch busbars 30a, the first S-phase branch busbars 30b, and the first T-phase branch busbars 30c. And a first N-phase branch busbar 30d. The second branch busbars 40a, 40b, and 40c each include a second R-phase branch busbar 40a, a second S-phase branch busbar 40b, and a second T-phase branch busbar 40c. .

The branch output busbars 50a, 50b, 50c, and 50d are output sections for supplying power to the load side from the respective circuit breakers 20a, 20b, 20c, and 20d for the load circuits. It is provided for each of the three phases of the phase and the N phase to be grounded. Accordingly, reference numeral 50a indicates an R-phase branch output busbar, symbol 50b indicates an S-phase branch output busbar, symbol 50c indicates a T-phase branch output busbar, and 50d indicates an N-phase branch output busbar. Power can be drawn out from the branch output busbars 50a, 50b, 50c, and 50d to the respective branch circuits.

As can be seen in Figure 2, the underground low-pressure distribution box 100 according to the present invention is the branch busbar (30a, 30b, 30c, 30d, 40a, 40b, 40c) and the N-phase branch output busbar (50d) It includes a common horizontal connection (COM 1, COM 2, COM 3, COM 4) provided for the common connection, these common horizontal connection (COM 1, COM 2, COM 3, COM 4) is insulated plate (100e) The rear of the fixed spaced apart from each other at a predetermined interval downward from the top. In more detail, the other end of the first R-phase branch busbar 30a, one end of which is connected to the main circuit breaker 10, is connected to the R-phase common horizontal connection COM 1 located at the uppermost level, and a circuit breaker for branch circuits ( The other ends of the four second R-phase branch busbars 40a having one end connected to 20a, 20b, 20c, and 20d are respectively connected. The other end of the first S-phase branch busbar 30b having one end connected to the main circuit breaker 10 is provided at the S-phase common horizontal connection COM 2 located next to the R-phase common horizontal connection COM 1. The other ends of the four second S-phase branch busbars 40b having one end connected to the circuit breakers 20a, 20b, 20c, and 20d for branch circuits are connected to each other. The other end of the first T-phase branch busbar 30c having one end connected to the main circuit breaker 10 is provided at the T-phase common horizontal connecting block COM 3 positioned next to the S-phase common horizontal connecting bar COM 2. The other ends of the four second T-phase branch busbars 40c having one end connected to the circuit breakers 20a, 20b, 20c, and 20d for branch circuits are connected to each other. The other end of the first N-phase branch busbar 30d having one end connected to the main circuit breaker 10 is connected to the N-phase common horizontal connection COM 4 located at the lowermost part, and the circuit breaker 20a for branch circuits 20a, Four second N-phase branch output busbars 50d provided in the number corresponding to 20b, 20c, and 20d and having one end installed side by side with the branch output busbars 50a, 50b, and 50c on the front surface of the insulating plate 100e. The other end of) is connected, respectively.

N-phase current transformers CTa, CTb, CTc, and CTd are installed in the N-phase branch output busbars 50d of the branch output busbars 50a, 50b, 50c, and 50d to detect ground faults in the branch circuit. The phase current is detected and transmitted to the main circuit breaker 10, more specifically, to the diagnostic control unit (see symbol 3e in FIG. 5) of the air circuit breaker.

Meanwhile, in FIGS. 1 and 2, the electric current flowing from the output of the secondary side of the power distribution transformer (not shown) to the underground low voltage distribution box 100 of the present invention and flowing into the branch circuit in the underground low voltage distribution box 100 is shown. Briefly describe the flow behavior.

The three-phase current and the N-phase current introduced into the underground low voltage distribution box 100 of the present invention from the secondary side output of the distribution transformer, not shown, first, the first branch busbars 30a, 30b, 30c, 30d, and the three-phase current flows through the common horizontal connection blocks COM 1, COM 2, and COM 3 and the second branch busbars 40a, 40b, and 40c for the circuit breakers 20a and 20b for branch circuits. Out through the branch output busbars 50a, 50b and 50c via 20c and 20d, it flows out to the load side branch circuit. The N-phase current flowing through the first N-phase branch busbar 30d flows out to the ground via the N-phase common horizontal connecting rod COM 4. At this time, since the second N-phase branch output busbars 50d for four branch circuits installed in parallel with the respective branch output busbars 50a, 50b, and 50c are also connected to the N-phase common horizontal connection table COM 4, When there is an N-phase current flowing through the second N-phase branch output bus bar 50d, the N-phase current flows out to the ground via the N-phase common horizontal connecting rod COM 4.

On the other hand, referring to Figure 3 which is a schematic circuit diagram showing the electrical circuit configuration of the underground low voltage distribution box according to an embodiment of the present invention.

As shown in FIG. 3, the underground low voltage distribution box 100 according to the present invention includes a single main circuit breaker 10 connected in series to a power supply side and a plurality of branch circuits connected in parallel to each other at an output of the main circuit breaker 10. And circuit breakers 20a, 20b, 20c, and 20d. Therefore, the current flowing into the main circuit breaker 10 from the power supply side is divided into 1/4 through the circuit breakers 20a, 20b, 20c, and 20d for wiring and flows to the load side of each branch circuit.

Meanwhile, the main circuit breaker 10 included in the underground low pressure distribution box 100 according to the present invention will be described with reference to FIG. 4.

As the main circuit breaker 10 as shown in FIG. 4, the air circuit breaker is classified as a pull-out air circuit breaker, and the air circuit breaker main body 1 and the air circuit breaker main body 1 can be pulled in and pulled out and are not shown outside The power supply terminal and the load terminal are configured to include a cradle (2) provided in the rear. On the top of the air circuit breaker main body 1 and the cradle 2, main body side control terminals 1a and cradle side control terminals 2a are respectively provided as control terminals for transmission and signal transmission and reception in the air circuit breaker main body 1; Prepared. As the transmission apparatus in the air circuit breaker main body 1, a trip coil part, an electric actuator, an electric motor, etc. can be included. As an external transmission / reception signal, a remote opening / closing control signal capable of controlling the opening and closing of the air circuit breaker at a remote location, an opening / closing position information signal of the opening / closing mechanism in the current air circuit breaker main body 1, and a diagnostic control unit installed on the front of the air circuit breaker main body 1 The control power supplied to the corresponding over current relay may be included. The main body side control terminal 1a and the cradle side control terminal 2a are automatically connected or disconnected according to the inlet position inside the cradle 2 of the air circuit breaker main body 1 or the outlet position drawn out from the cradle 2. . On the front of the air circuit breaker main body 1, an over current relay 3 corresponding to the diagnostic control unit of the air circuit breaker is provided.

Meanwhile, the overcurrent relay according to the present invention will be described with reference to FIG. 5, which is a functional block diagram showing a circuit functional unit configuration of an overcurrent relay having a communication unit and a diagnostic control unit.

5 is a three-phase power line (R, S, T) and one ground line connected to the power supply side, that is, the secondary output side of the transformer, and to the air circuit breaker of the underground low voltage distribution box according to the present invention, in addition to the overcurrent relay according to the present invention. (N) is shown. In FIG. 5, the code CT1-CT3 indicates the power supply side, that is, the power supply side three-phase current transformer for detecting the current of the three-phase secondary output side of the distribution transformer, and the code CTa-CTd described above with reference to FIG. N-phase current transformer. Here, the three-phase current transformer on the power supply side may be embedded in the air circuit breaker, that is, in the air circuit breaker main body 1 of FIG. 4, or may be installed outside the air circuit breaker, that is, on the secondary output side line of the power distribution transformer. In Fig. 5, the breaker 1b is triggered by a trip mechanism and a trip mechanism that trigger the opening and closing mechanism to the trip position by using the electromagnetic force of the trip coil as is well known. A device including a well-known opening and closing mechanism for driving the movable contactor to a tripping position that separates the movable contactor from the fixed contactor by using elastic energy stored in a tripping spring (not shown), wherein the tripcoil is provided from a diagnostic control unit 3e to be described later. The magnetization is magnetized by the trip signal to trigger the opening and closing mechanism to the trip position. In Fig. 5, reference numerals 20a to 20d denote circuit breakers for branch circuits as described above with reference to Fig. 1.

In Fig. 5, the overcurrent relay 3 according to the present invention includes a filter section 3a, an amplifier section 3b, a multiplexer section 3c, an A / D converter section 3d, and a diagnosis. It is comprised including the control part 3e and the communication part 3f. Here, the filter unit 3a is included in an electrical signal (voltage signal) that is proportional to the amount of current flowing through the three-phase power lines R, S, and T provided from the three-phase current transformers CT1-CT3 on the power supply side. As a filter circuit portion for removing a harmonic signal (noise signal) which may cause an error, it may be constituted by, for example, a low pass filter.

The amplifier 3b includes an electrical signal passing through the filter unit 3a in proportion to the amount of current flowing through the three-phase power lines R, S, and T provided from the three-phase current transformers CT1-CT3, and an N-phase current transformer ( N-phase (neutral phase) provided from CTa-CTd, i.e., an amplifying circuit section for amplifying and outputting an electric signal passing through the filter section 3a in proportion to the amount of current flowing through the ground line. Four are provided corresponding to three phases and N phases.

The multiplexer section 3c is a multiplexer circuit section that selectively provides the three-phase power supply side current amount signal from the amplifier section 3b and the current amount signal flowing through the N phase, that is, the ground line, to the A / D converter section 3d at the rear stage.

The A / D converter section 3d is an A / D conversion circuit section for converting an analog signal from the multiplexer section 3c into a digital signal that can be recognized by the diagnostic control section 3e constituted by a microcomputer (microprocessor) at a later stage. It can be configured as.

The diagnostic control unit 3e passes through the filter unit 3a, the amplifier unit 3b, the multiplexer unit 3c, and the A / D converter unit 3d from the N-phase current transformers CTa-CTd as digital signals. The ground current is determined by comparing the provided N-phase current with a predetermined first reference current value I _REF1 . For example, when the N phase current is greater than the first predetermined reference current value I _REF1 , the diagnostic control unit 3e determines that a ground fault occurs in the branch circuit, and the N phase current has a predetermined first reference current value I _REF1 . If it is less than or equal to, it is decided as the normal current energized state without ground fault.

When the diagnosis control unit 3e determines the occurrence of a ground fault, the diagnostic control unit 3e issues a trip signal to a corresponding circuit breaker (that is, at least one of 20a, 20b, 20c, and 20d), and for branch circuit wiring in response to the trip signal. The breaker (that is, at least one of 20a, 20b, 20c, 20d), in particular the tripping and switching mechanism of the wiring breaker, operates in the trip (blocking) position to cut off the branch circuit. In addition, the diagnostic control unit 3e compares the three-phase current detected by the three-phase current transformer CT1-CT3 for detecting the three-phase current with the second predetermined reference current value I _REF2 , for example, in the three-phase current. When at least one current value is greater than a predetermined second reference current value I _REF2 , a trip signal is output to the breaking device 1b, i.e., the tripping mechanism of the air circuit breaker, and all three phase current values are predetermined. 2 If less than or equal to the reference current value I _REF2 , the trip signal is not output.

The communication unit 3f may be provided to exchange status information and transmit / receive data with, for example, a power supply-side distribution transformer side or other external supervisory control panel (not shown). Specifically, the communication unit 3f may be, for example, RS-232C, Dedicated line serial communication module such as RS-485, power line communication module (POWER LINE COMMUNICATION MODULE), wireless communication module (Radio Frequency Module), optical communication module and the like can be selectively configured.

5 and 6, a ground fault detection and processing operation process performed by the diagnostic control unit of the overcurrent relay of FIG. 5 and the configuration of a control method of a ground fault detection and processing process of a underground low voltage distribution box according to an exemplary embodiment of the present invention. Explain.

As illustrated in FIG. 6, the control method of the underground low voltage distribution box according to the present invention includes installing N-phase current transformers CTa, CTb, CTc, and CTd for detecting neutral phase current for each circuit breaker for branch circuits. Step, i.e., installing N-phase current transformers CTa, CTb, CTc, and CTd corresponding to the circuit breakers 20a, 20b, 20c, and 20d for branch circuits to detect the N-phase current (ST1); The neutral phase current (N phase current) detected by the N phase current transformers CTa, CTb, CTc, and CTd, respectively, is compared with a value of a predetermined reference current, that is, the first reference current value I _REF1 . Steps ST2 and ST3; And a step ST4 of tripping the circuit breaker for branching when the ground fault is determined in the step ST3. Determining whether or not the ground fault (ST2, ST3) and tripping the corresponding circuit breaker for the branch (ST4) may be performed by the over-current relay (see reference numeral 3 of Figs. 4 to 5) of the air circuit breaker.

Ground detection and processing operations of the underground low pressure distribution box according to the present invention will be described with reference to FIGS.

In the underground low voltage distribution box according to the present invention, the ground fault detection is provided in parallel with the branch output busbars 50a-50c of the circuit breakers 20a, 20b, 20c, and 20d for branch circuits corresponding to each branch circuit. It is detected by the N-phase current transformers CTa, CTb, CTc, and CTd provided to surround the output busbar 30d. The detection signal representing the amount of N-phase current for each branch circuit detected by the N-phase current transformers CTa, CTb, CTc, and CTd is the main circuit breaker 10 in FIG. 1, more specifically, the overcurrent in the air circuit breaker of FIG. The diagnostic control unit 3e in the overcurrent relay 3, which is transmitted to the relay 3 and constitutes a microcomputer, compares the predetermined reference current value, that is, the first reference current value I _REF1 with the amount of N-phase current delivered. To determine whether a ground fault has occurred, that is, for example, when the N phase current is larger than the first predetermined reference current value I _REF1 , the ground fault occurs on the branch circuit, and the N phase current determines the first reference current value ( If it is less than or equal to I _REF1 ), it is decided as a steady current energized state without ground fault. When the ground fault is determined, the diagnostic control unit 3e outputs a trip signal to the branch circuit wiring breakers 20a, 20b, 20c, and 20d of the branch circuit, and the branch circuit wiring breakers 20a, 20b, 20c, 20d) is tripped (blocked). At this time, since the trip signal is not output to the circuit breaker for branch circuits other than the corresponding one, normal power supply is continued to the branch circuit, and the power failure is localized to the branch circuit having the ground fault.

According to a preferred embodiment of the present invention, the three-phase current detection and abnormal diagnosis and the control method of the control process in the underground low-voltage distribution, showing the configuration of the control method of the power-side three-phase current performed by the diagnostic control unit of the overcurrent relay of FIG. A flow chart showing an operation process will be described with reference to FIG. 7.

The control method of the underground low voltage distribution box according to the present invention comprises the steps of installing a three-phase current transformer for detecting the phase current corresponding phase of the three-phase power supply side, that is, a power-side three-phase current transformer for detecting the power supply phase current of R phase, S phase, T phase Installing (CT1-CT3) to detect the power supply side three-phase currents I _R , I _S , I _T (ST11); The three-phase currents I _R , I _S , and I _T detected by the three-phase current transformers CT1-CT3 at the power supply side are compared with a predetermined reference current value, that is, the second reference current value I _REF2 . Determining occurrence (ST12, ST13); And controlling to cut off the circuit when determining abnormal current generation on the circuit, that is, outputting a trip signal to the breaking device 1b (trip mechanism) of the air circuit breaker (ST14). Determining the occurrence of abnormal current on the circuit (ST12, ST13) and controlling to block the circuit (ST14) may be performed by the overcurrent relay of the air circuit breaker (see reference numeral 3 of Figs. 4 to 5).

On the other hand, the abnormal operation of the three-phase current of the power supply side of the underground low voltage distribution box according to the present invention and the processing operation at the time of abnormal detection will be described with reference to Figs.

In the underground low voltage distribution box according to the present invention, the abnormal detection of the power supply three-phase current is installed on the power supply side three-phase current transformer corresponding to each power supply three-phase line (R, S, T) as shown in FIG. It is detected by (CT1-CT3). The detection signal indicative of the amount of each phase current detected by the power-side three-phase current transformers CT1-CT3 is transmitted to the main circuit breaker 10 in FIG. 1, more specifically, the overcurrent relay 3 in the air circuit breaker of FIG. The diagnostic control unit 3e in the overcurrent relay 3 composed of a microcomputer compares the predetermined reference current value, that is, the second reference current value I _REF2 with the transferred three-phase current amount, respectively, to determine whether an abnormal current is generated. In other words, for example, when at least one of the three phase currents is larger than the predetermined second reference current value I _REF2 , the occurrence of abnormal current on the power supply side circuit is determined and all three phase currents are determined as the predetermined second reference current value I. _{If it} is less than or equal to _REF2 ), it is decided as the steady current energized state where there is no error in the three-phase current of the power supply. When the occurrence of the abnormal current is determined, the diagnostic control unit 3e outputs a trip signal to the trip mechanism of the breaker 1b to trip (block) the main breaker 10. Therefore, power supply to all branch circuits is stopped at this time.

1 is a front view showing the configuration of a underground low pressure distribution box according to a preferred embodiment of the present invention,

Figure 2 is a rear view showing the configuration of the underground low pressure distribution box according to an embodiment of the present invention,

3 is a schematic circuit diagram showing the electrical circuit configuration of the underground low voltage distribution box according to an embodiment of the present invention,

4 is a perspective view showing a characteristic external configuration of an example of a circuit breaker as a component that is constituted in a underground low pressure distribution box according to a preferred embodiment of the present invention.

FIG. 5 is a functional block diagram showing a circuit functional unit configuration of an overcurrent relay having a communication unit and a diagnostic control unit in an air circuit breaker as a component that is constituted in an underground low voltage distribution box according to a preferred embodiment of the present invention.

FIG. 6 is a flowchart illustrating a ground fault detection and processing operation performed by the diagnostic control unit of the overcurrent relay of FIG. 5 while showing the configuration of a ground fault detection and processing process of an underground low voltage distribution box according to an exemplary embodiment of the present invention.

7 is a diagram illustrating the configuration of a method for detecting a three-phase current, an abnormal diagnosis, and a process in a low voltage underground distribution according to a preferred embodiment of the present invention, and at the same time, a three-phase current at the power supply side performed by the diagnostic control unit of the overcurrent relay of FIG. 5. This is a flowchart showing the detection and processing process.

* Explanation of symbols on the main parts of the drawings

1: Air circuit breaker main body 1a: Main body side control terminal

1b: Block 2: Cradle

2a: cradle side control terminal 3: overcurrent relay

3a: filter part 3b: amplification part

3c: multiplexer section

3d: A / D converter section 3e: Diagnostic control section

3f: communication unit 10: main circuit breaker

20a, 20b, 20c, 20d: circuit breaker for branch circuit

30a: First R-phase branch busbar 30b: First S-phase branch busbar

30c: First N-phase branch busbar 30d: First N-phase branch busbar

40a: 2nd R phase branch busbar 40b: 2nd S phase branch busbar

40c: 2nd T phase branch busbar 50a: R phase branch output busbar

50b: S-phase branch output busbar 50c: T-phase branch output busbar

50d: N-phase branch output busbar

CTa, CTb, CTc, CTd: N-Phase Current Transformers

CT1-CT3: three-phase current transformer on the power side

COM1: R phase common horizontal connection

COM2: S-phase common horizontal connection

COM3: T-phase common horizontal connection

COM4: N-phase common horizontal connection

100: underground low voltage distribution box 100a, 100a ': vertical support

100b, 100b ': horizontal support 100c: intermediate horizontal support

100d: Upper middle vertical support 100e: Insulation plate

100e-1: before and after through

Claims (8)

In underground low pressure distribution, A main circuit breaker connected to the power supply side and including one air circuit breaker having a communication section and a diagnostic control section; A circuit breaker electrically connected to the main circuit breaker and including a plurality of branch circuit wiring breakers; A branch bus bar electrically connected between the main circuit breaker and the power distribution circuit breaker, the branch bus bar being provided for each of R phases, S phases, T phases, and N phases that are grounded; An output unit for supplying power to the load side from each of the branch circuit wiring breakers, the branch output bus bar being provided for each of R phase, S phase, T phase, and N phase grounded; And Among the branch output busbars, it is provided in the N-phase branch output busbars, and includes a current transformer which detects the N-phase current and transmits the current to the main circuit breaker to detect a ground fault in the branch circuit. The diagnostic control unit of the air circuit breaker, And a microcomputer for determining whether the ground fault is compared by comparing the N-phase current provided by the current transformer with a predetermined reference current value. delete The method of claim 1, The diagnostic control unit of the air circuit breaker, An underground low voltage distribution box comprising a microcomputer that outputs a trip signal to a corresponding circuit breaker when a ground fault is determined. The method of claim 1 It further includes a three-phase current detection current transformer for detecting the phase current of the R phase, S phase, T phase, The diagnostic control unit of the air circuit breaker, Underground low pressure, characterized in that for comparing the three-phase current detected by the three-phase current detection current transformer with a predetermined reference current value to determine whether or not to output a trip signal to the tripping mechanism of the circuit breaker Distribution box. In the control method of underground low pressure distribution box, Installing an N-phase current transformer for detecting neutral phase current individually for each circuit breaker for branch circuits; Determining whether the ground fault is detected by comparing the neutral phase current detected by the N-phase current transformer with a value of a predetermined reference current; And When the ground fault is determined in the step of determining whether the ground fault, comprising the step of tripping the circuit breaker for the branch, And determining the ground fault and tripping the branch circuit breaker are performed by an overcurrent relay of the air circuit breaker. The method of claim 5, Installing a three-phase current transformer for detecting a corresponding phase current for each phase of the three-phase power supply side; Determining occurrence of abnormal current in a circuit by comparing the three-phase current detected by the three-phase current transformer with a value of a predetermined reference current; and The control method of the underground low voltage distribution box, characterized in that it further comprises the step of controlling to cut off the circuit when determining the occurrence of abnormal current on the circuit. delete The method of claim 6, And determining the occurrence of abnormal current on the circuit and controlling the circuit to be cut off are performed by an overcurrent relay of the air circuit breaker.

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