JP3112706B2 - Ground fault detection device for distribution system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault detecting device,
More particularly, the present invention relates to a ground fault detection device for a distribution system.

[0002]

2. Description of the Related Art FIG. 4 shows a supporting structure of a distribution line.
1 is a telephone pole, which is made of concrete, although it is made of wood. 2 is an arm (arm), 3 is an arm tie, 4,
5 and 6 are insulators, and 7 is a metal band. Reference numeral 8 denotes a metal conductor, of which there are various types. Here, a cap type metal cap is shown. 9 is an imaginary ground wire, 10, 1
Reference numerals 1 and 12 denote three-phase high-voltage distribution lines.
6 and is insulated and supported by the arm 2. 13,14,15
Is an insulator, and 16, 17, and 18 are low-voltage lighting lines of a single-phase three-wire system. Of these, 16 is grounded and serves as a common ground wire. 19 is a transformer arm, 20 is an insulator, 2
Reference numeral 1 denotes a single-phase transformer.
, The center tap of the secondary winding 23 is connected to the low-voltage wire 16, and the other windings are connected to the low-voltage wire 1.
7, 18 are connected. Reference numeral 24 denotes the case of the single-phase transformer 21. 25a to 25e are ground lines 25. The ground impedance of the ground 26 is usually on the order of tens of ohms.

One of the improvements in power supply reliability is to shorten the power outage time. For that purpose, it is important to find the place where the accident occurred and the equipment early. Therefore, a current transformer (CT) is installed for each device for the purpose of detecting a ground fault that requires a long time to investigate the fault because it is difficult to find the fault. A system that does this is conceivable. However, when installing a current transformer for detection on these monitored equipment, transformers, switches, arresters, underground cables, etc. can be easily attached structurally, but for insulators, the structure and the number of members It is necessary to take measures such as minimizing the number of current transformers in consideration of economic efficiency rather than many things.

[0004]

Since the insulator is directly attached to the arm and the insulator is more reliable than other devices, it is not necessary to detect a ground fault accident for each phase, and the three phases are collectively used. Is enough. However, even if a current transformer is attached to an arm or an arm tie, a ground fault current of an accident that occurred in another pillar flows through an overhead ground wire (GW) and flows from the cap to the arm, so that a malfunction easily occurs.

[0005] In order to prevent this, means as shown in Figs. 5 to 7 can be considered. That is, as shown in FIG. 5, a current transformer 28 as a current detector is installed on the cap 8,
A ground wire 25 is passed through the current transformer 28 from the insulators 4, 5, 6 through the arm 2 and the arm tie 3 to a ground 26. 27 is a ground resistance of the ground line 25.

FIGS. 6 and 7 are equivalent circuits of FIG.
When the ground fault current I ₁ spills from another pillar, it is canceled on the primary side of the current transformer 28 as shown in FIG. Further, when the insulator ground fault of its own pillar can detect the ground fault current I _L of the insulator as shown in FIG. However, the value R _P is small in which case the leakage current I ₃ large _{(I 1 -I 2) = I} 3 next to the leak component resistor 29 of electric pole 1 as shown in FIG. 8, from this I ₃ is the threshold Becomes large and malfunctions.
The reason for this is presumed that the lowering of the impedance of the concrete column (con column) is due to the penetration bolt that fixes the arm or arm tie to the con column coming into contact with the rebar inside the con column, As a result of actual measurement, it was found that 20 to 30% or more of the pillars (substantially equivalent to the ground resistance of the ground wire) were present.

As a means for canceling the leakage of the concrete column, a method shown in FIGS. 9 and 10 can be considered. FIG. 10 is an equivalent circuit of FIG. That is, the current transformer 28b is installed on the cap 8, and the current transformer 28c is installed on the connecting pole 1, and the secondary sides of these two current transformers are differentially connected. Therefore, in this method, the leakage current of the column 1 can be canceled. However, the current transformer 28c provided on the lower side of the connecting column 1 needs to have a penetration diameter equal to or larger than the diameter of the connecting column (400 mm). Therefore, it is not practical in view of cost and reliability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a high-voltage circuit ground fault caused by a decrease in insulation of a high-voltage device attached to an insulator or a metal arm as an insulating support of a distribution line. It is an object of the present invention to provide a ground fault detector capable of specifying a fault at a high performance without being affected by a load current of a low voltage circuit or a ground fault current of another pillar.

[0009]

In order to achieve the above object, a ground fault detection apparatus according to the present invention insulates and supports a distribution line on a concrete column via a support fixed to the column. supporting the ground wire by a metal conductor which is attached to the concrete column, before the ground wire
In a power distribution system grounded to the ground by a ground wire via the metal conductor, an imaginary
A first current detector for detecting a current flowing to the ground line, the current
When flowing from the support to the overhead ground wire via the metal conductor, this current and the current flowing through the ground wire become a harmonic, and the current flows from the overhead ground wire via the metal conductor to the ground wire.
When flowing to concrete columns and ground lines
A second current detector disposed so that the current flowing through the power line and the current flowing through the ground line become differential, and comparing the detection signals of the first and second current detectors with the distribution line. Is detected. In addition, the ground fault detection device of the present invention insulates and supports the high-voltage distribution line and the low-voltage distribution line on the concrete column via supports respectively fixed to the concrete column, and also mounts the metal mounted on the concrete column. supporting the ground wire by a conductor, the overhead ground
Ground the wire to ground via the ground conductor via the metal conductor
At the same time, connect the common ground wire of the low-voltage distribution line to the ground with a ground wire.
In the distribution system to the earth, a first current detector for detecting a current flowing through the metal conductor, the gold from the ground wire
A second current detector for detecting a current flowing through a connection between the common ground wire and the ground wire via the metal conductor, and comparing the electric signals of the first and second current detectors with the distribution line. Is detected.

[0010] The ground fault detection device for a power distribution system according to the present invention further comprises insulatingly supporting the high-voltage distribution line and the low-voltage distribution line on the concrete column via support members fixed to the concrete column, respectively. supporting the ground wire by a metal conductor which is attached to the the ground wire
Ground to the ground via a metal conductor and ground wire, and
In the distribution system for grounding the joint ground wire distribution lines to the ground line ground, a first current detector for detecting a current flowing through the metal conductor, and co bare wire through the metal conductor from the ground wire grounded A second current detector for detecting a current flowing through a connection portion with a line, and comparing an electric signal of the first and second current detectors to detect a ground fault of the distribution line. I do.

Further, the ground fault detection device for a power distribution system according to the present invention detects a ground fault in a distribution line by comparing changes in electric signals of the first and second current detectors and detects a ground fault in the power distribution system. This is to detect a ground fault.

[0012]

The detection signal S4 of the first current detector for detecting only the current flowing between the support and the overhead ground line, and the current flowing between the support and the overhead ground line and the ground from the support via the ground line are connected to the ground side. Is compared with a detection signal S5 of a second current detector for detecting both currents flowing through the second column.

When the detection signal S5 exceeds the threshold value and S5 <
When S4, there is no accident on the own pillar, it is judged that there is an accident on the other pillar. When the signal S5 exceeds the threshold value and S5 ≧ S4, it is judged that the accident on the insulator of the own pillar has occurred. If it does not exceed it, it is judged that there is no accident of its own pillar.

Further, the detection signals S4 and S5 are calculated by the equation (1). S5 / S4 ≧ K (1) When the calculation result S5 / S4 is equal to or more than the detection sensitivity constant K, it is determined that the insulator of the own pole is an accident.

The detection signal S4 of the current flowing between the support and the overhead ground wire is compared with the detection signal S5 of the current flowing from the support to the ground via the ground wire (S4-S5). Judge as a pillar accident. When (S4-S5) exceeds the threshold value and (S4-S5) <S4, it is determined that there is no accident on the own pillar and another pillar accident, and (S4-S5) exceeds the threshold value and (S4-S5). When ≧ S4, it is determined that the insulator of the own pillar has an accident, and when the signal (S4-S5) does not exceed the threshold value, it is determined that there is no accident of the own pillar. Further, the change of the detection signal S4 is represented by △ S4, and the change of the detection signal S5 is represented by △ S5.
When 演算 S4> △ S5, it is determined that another pillar has a ground fault.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIGS. 1 and 2 show an apparatus for detecting a ground fault in a power distribution system according to an embodiment of the present invention. A current transformer 28a as a first current detector and a second current detector are provided on a metal cap 8. A current transformer 28b is installed, and the output of the current transformer 28b is compared by an arithmetic processing unit 30 to judge whether the current comes from another pillar or the accident of the own pillar.

As shown in FIG. 2, a sneak current I ₁ due to a ground fault at another pillar flows into the cap 8 through an overhead ground wire 9. The sneak current I ₁ flowing into the cap 8 is shunted to the column 1 and the ground line 25 as I ₂ and I ₃ , respectively, and flows into the ground 26 through the resistors 27 and 29.

The current transformer 28a detects the sneak current I ₁ and inputs the detection output signal S1 to the arithmetic processing unit 30. Further, current transformer 28b is sneak current I ₁ and the ground line 2
5 is differentially detected as I ₃ = I ₁ −I _2, and a detection output signal S 2 is input to the arithmetic processing unit 30. As described above, since there can be no be a R _E "R _P is leak component equivalent resistance R _P of the ground resistance of the normal of the ground line 25 R _E and concrete columns 1, S2 <becomes S1, the arithmetic processing unit 30
Determines that S2 <S1, and determines the ground fault signal S at another pillar.
3 is output.

[0020] In the case of ground fault of the insulator in its own column, as shown in FIG. 1, the ground fault current I _L from the insulator 4 (5,6)
Is the current I ₅ flowing into the overhead ground wire 9 through the cap 8,
The current I ₆ flows into the ground 26 through the connecting post 1 and the current I ₇ flows into the ground 26 through the ground wire 25. Therefore, current transformer 28a inputs the detection output signal S4 to detect a current I ₅ to the processing unit 30.
Current transformer 28b current I ₅ and the current _{I 7 = I L - (I} 5 + I 6)
And a detection output signal S5 is input to the arithmetic processing unit 30.

However, normally, S5 ≧ S4,
When R _E and R _P are large and the sneak current I ₅ to the other pillar is large, S5 ≒ S4. Therefore, when the signal S5 exceeds the absolute value level and S5 <S4 , the arithmetic processing unit 30
Judge that there is no accident on the own pillar and accident on the other pillar. Also,
When the signal S5 exceeds the absolute value level and S5 ≧ S4, the arithmetic processing unit 30 determines that the insulator accident has occurred on the pillar. Further, when the signal S5 does not exceed the absolute value level, the arithmetic processing unit 30 determines that there is no accident of its own pillar.

The arithmetic processing section 30 sends out the arithmetic processing signal S3 or S6 as a signal of the slave station. When a ground fault current detected by a current transformer installed in each device of the distribution system exceeds a threshold, it is held in a storage device of the slave station. The master station calls each slave station, and upon detecting the accident information, transmits the accident information to the branch office and the sales office via the power distribution teleconverter.

According to the above-described embodiment, the second current detection for detecting both the detection signal of the first current detector for detecting the current flowing through the metal cap and the current flowing to both the metal cap and the ground line. By detecting the ground fault by comparing with the detection signal of the detector, it is possible to prevent the detection malfunction due to the leakage of the concrete column, and the two current transformers used have a penetration diameter to pass through the cap part. The overhead ground wire can be removed from the top of the cap and laid sideways, so that it can be inserted from the top of the cap, eliminating the need for a split iron core and reducing costs. Thus, a highly reliable detection device can be obtained.

FIG. 3 shows a ground fault detecting apparatus according to another embodiment of the present invention. The ground fault detecting apparatus according to the present embodiment is configured to supply a current I ₁ flowing to a ground wire 25 a connected to the overhead ground wire 9.
Is detected by the first current detector 28a, and the insulator 4
Ground wire 25 connecting (5, 6) and low-voltage common ground wire 16
The second current detector 28b detects the current flowing through the second current detector b.

According to the ground fault detecting device shown in FIG. 3, the insulator 4 supporting the overhead ground wire 9 and the high voltage distribution lines 10 (11, 12) is provided.
The current I ₁ flowing through the ground line 25a between (5, 6) is detected by the first current detector 28a, and the detection signal S ₁ is input to the arithmetic processing unit 30. Further, a current I ₃ flowing through the ground line 25b between the insulator 4 (5, 6) and the common ground line 16 is detected by the second current detector 28b, and a detection signal S ₂
Is input to the arithmetic processing unit 30. Here, the current I ₃ is a difference I ₃ between the currents I ₁ and I ₂ = (I ₁ −I ₂ ), and the arithmetic processing unit 30 detects a ground fault accident based on the current relationship.

[0026]

As described above, according to the present invention, a first current detector for detecting a current flowing between a support supporting a distribution line and an overhead ground wire, and a current flowing between the support and the ground are provided. And a second current detector for detecting the ground fault is detected by effectively comparing and calculating the detection signals of the first and second current detectors. the high-voltage circuit ground fault point caused by reduced insulation, such as insulators and high pressure equipment to be attached to the metal arm is, without being influenced by the ground fault current in the load current or other pillars of low-voltage circuit, high performance ground It is possible to obtain a ground fault detection device that can specify a fault.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an apparatus for detecting a ground fault in a distribution system according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating a ground fault detection apparatus for a distribution system according to an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram showing a ground fault detection device for a distribution system according to another embodiment of the present invention.

FIG. 4 is an explanatory view showing a connection example of a utility pole as a support.

FIG. 5 is an explanatory diagram showing a conventional ground fault detection device for a power distribution system.

FIG. 6 is an equivalent circuit diagram of the ground fault detection device of FIG. 4;

FIG. 7 is an equivalent circuit diagram of the ground fault detection device of FIG. 4;

FIG. 8 is an equivalent circuit diagram of the ground fault detection device of FIG. 4;

FIG. 9 is a configuration diagram of a conventional ground fault detection device for a power distribution system.

FIG. 10 is an equivalent circuit diagram of the ground fault detection device for the distribution system of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Concrete pillar 4,5,6 ... Insulator 8 ... Metal cap 9 ... Aerial ground wire 16 ... Low voltage joint ground wire 25,25a, 25b, 25e ... Ground wire 26 ... Ground 27 ... Ground resistance 28a ... First current detection Current transformer 28b current transformer as second current detector 29 ground resistance of concrete column 30 arithmetic processing unit

──────────────────────────────────────────────────続 き Continuing from the front page (72) Hiroshi Haga 1-1-1 Kokubuncho, Hitachi City, Ibaraki Prefecture Inside Kokubu Plant, Hitachi, Ltd. (72) Yasuo Kataoka 2-1-1, Osaki 2-chome, Shinagawa-ku, Tokyo No. Inside the Meidensha Co., Ltd. (72) Tadashi Miyano, 2-1-1-17 Osaki, Shinagawa-ku, Tokyo, Japan Inside the Meidensha Co., Ltd. (72) Inventor Yasuyuki Migami 2-1-1, Osaki, Shinagawa-ku, Tokyo, Japan Inside the Meidensha Co., Ltd. (56) References JP-A-4-74971 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 31/08 G01R 31/02 H02H 3/16

Claims (3)

(57) [Claims] 1. A distribution line is insulated and supported on a concrete column via a support fixed to the concrete column.
An overhead ground wire is supported by a metal conductor attached to the concrete pillar, and the overhead ground wire is supported through the metal conductor.
In a power distribution system that is grounded to the ground by a ground wire, the power flows from the support to the overhead ground wire via the metal conductor.
A first current detector for detecting a current, and when the current flows from the support through the metal conductor to the overhead ground wire, the current and the current flowing through the ground wire become a summation, and the current flows through the overhead ground wire. Through the metal conductor
When flowing to the concrete column and the ground line, the metal
A second current detector disposed so that a current flowing through the conductor and a current flowing through the ground line become differential; and comparing the detection signals of the first and second current detectors, A ground fault detection device for a distribution system, which detects a ground fault of an electric wire. 2. A high-voltage distribution line and a low-voltage distribution line are respectively insulated and supported on a concrete column via a support fixed to the concrete column, and an overhead ground wire is supported by a metal conductor attached to the concrete column. And this fictional
Ground the ground wire to the ground via the ground conductor through the metal conductor
And the common ground wire of the low-voltage distribution line
A first current detector for detecting a current flowing through the metal conductor in a distribution system to be grounded, and a current flowing from the overhead ground wire to a connection between the common ground wire and a ground wire via the metal conductor ; A ground fault detecting device for a distribution system, comprising: a second current detector, and detecting a ground fault of the distribution line by comparing electric signals of the first and second current detectors. 3. The method according to claim 1, wherein
And a second current detector of the power distribution system ground fault of ground fault detection device and detects a ground fault of the comparison to the distribution line for variation of the electrical signal.