JP2001095149A - Method and device for discriminating ground section for private substation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of discriminating ground section for a private power substation, capable of discriminating which of off-premise or on-premise cable lead-in side or power substation side has ground failure with a simple structure and high precision without using a zero-phase voltage detector. SOLUTION: This method includes clamping of a grounding conductor 5 and lead-in cable 3 together using a zero-phase current transformer ZCT1, clamping of the grounding conductor 5 using a zero-phase current transformer ZCTc, and discriminating which of a power distribution line, the lead-in cable 3 or a private power substation 2 has a ground section, based on a phase difference between detected currents i1, ic of currents I1, Ic passing through the current transformer and current values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining a ground fault section in a private substation, and more particularly to a method for determining a ground fault section using a zero-phase current transformer in a service cable.

[0002]

2. Description of the Related Art Generally, a high-voltage ground fault relay is provided between a transmission line of a power company outside a premises and a private substation on the premises.

This high-voltage ground fault relay operates (detects a ground fault).
Then, in order to investigate the cause of the operation, a device that observes the input waveform when the ground fault relay operates, or performs highly sensitive ground fault detection, and stores the date and time when the ground fault was detected and the detection level in the memory Equipment was provided.

In the above-described apparatus for observing an input waveform, it is common to determine the location of a ground fault outside or on the premises based on the phase difference between the zero-phase voltage detected using a zero-phase voltage detector and the ground fault current. It is.

On the other hand, in the apparatus for recognizing a ground fault point of a distribution line disclosed in Japanese Patent Publication No. Hei 7-71374, a feeder breaker is provided for each feeder at a substation where distribution systems (feeders) having a regional spread are collected. Then, the feeder breaker is manually or automatically shut off by sequence control. At this time, the section switches DM1, DM2, which are provided in each section of the feeder,
It is disclosed that a time is measured until a voltage is cut off while sequentially applying a voltage to DM3, and a ground fault section is recognized from this time.

In Japanese Patent Publication No. 7-71374, a current flowing through a switch in a section is detected by using a zero-phase current transformer in order to detect a portion of the section in which the ground fault point is located. Then, the slave station obtains the ground fault current detection value and the phase at the time of the ground fault from this current, and transmits them to the master station.

[0007] The master station determines whether the ground fault current detection value in the transmitted section is larger than the threshold value, further determines whether the phases of the ground fault current in the preceding and following sections (phase at the time of ground fault) differ by 180 degrees, or The difference between the ground fault current before and after is greater than or equal to the threshold value, it is larger than the previous data, and it is checked in the next section comparison whether it is smaller. Had determined that a ground fault had occurred.

[0008]

However, since the device for investigating the cause of the high voltage ground fault relay is non-directional, it is difficult to determine whether a ground fault has occurred outside or inside the premises. there were.

For example, in a certain area, the number of operating high-voltage ground fault relays is about 1,000 per year, but about half of them cannot determine in which section a ground fault has occurred.

There is also a method of determining a ground fault section. However, since a zero-phase voltage detector is used, a grounding transformer or the like is required, which complicates the circuit and requires wiring work. was there.

On the other hand, the method disclosed in Japanese Patent Publication No. Hei 7-71374 is to detect a ground fault section of an off-premise distribution line. Is not determined.

In order to recognize a ground fault point, a switch is provided in each section, and when a ground fault is detected in this switch, a ground fault is detected by using a ground fault current, a phase difference, and a threshold value of the preceding and following sections. Because the system is large-scale because it recognizes points, it is not suitable for discriminating any ground fault on either the off-site or on-site entrance side or the substation facility side when using private substation equipment. There were challenges.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems. In a private substation, a simple construction without using a zero-phase voltage detector and a high accuracy on the outside or inside of the substation and on the substation side. It is an object of the present invention to obtain a ground fault section determination method for a private substation that can determine any of the ground faults.

[0014]

According to the present invention, a ground fault section in a private substation is provided with a predetermined substation connected to a high-voltage distribution line and a load supplied with a voltage lower than the high voltage. It has a drop-in cable that connects the private substation and draws the power from the distribution line to the private substation, and this drop-in cable is provided with a shielding copper tape on each of a plurality of core wires. Connected to each other and to the ground through a ground wire.

[0015] A first zero-phase current transformer having a polarity consisting of a primary side and a secondary side which clamps and passes the ground line and the incoming cable together, and a primary side and a primary side which clamp and pass the ground line. A second zero-phase current transformer having a secondary side polarity, a first detection current from the first zero-phase current transformer, and a second detection current from the second zero-phase current transformer To determine whether or not a ground fault has occurred in any section of the distribution line side, drop-in cable, or private substation based on the presence or absence of the detected current and the magnitude and phase difference of both currents. The gist of the present invention is to include a section discriminating device.

For this reason, when a ground fault occurs in the private substation, the second current flowing from the ground to the drop-in cable through the ground wire flows in the reverse direction through the ground wire and the shielded copper tape. This second current is canceled by the first zero-phase current transformer.

Then, only the first detection current flowing from the ground to the service cable via the distribution line is detected by the first zero-phase current transformer.

Further, a second zero-phase current transformer provided on the ground line flows from the ground and detects a second current. That is, the second current flowing from the secondary winding to the primary winding is detected.

For this reason, the first and second detected currents from the first zero-phase current transformer and the second zero-phase current transformer are input to the ground fault section discriminating device in opposite phases.

When a ground fault occurs in the drop-in cable, a second current flowing from the shielded copper tape of the drop-in cable to the ground via the ground wire causes the ground wire and the shielded copper tape to flow in opposite directions. As the current flows, the second current is canceled by the first zero-phase current transformer.

Then, only the first detected current flowing from the ground to the service cable via the private substation equipment is the first detected current.
Is detected by the zero-phase current transformer. At this time, the first current flows from the secondary side to the primary side of the first zero-phase current transformer.

A second zero-phase current transformer provided on the ground line detects a second current flowing from the ground line to the ground. That is, the second current flowing from the primary winding to the secondary winding is detected.

For this reason, the first and second detected currents from the first zero-phase current transformer and the second zero-phase current transformer are input to the ground fault section discriminating device in opposite phases.

Further, when a ground fault occurs on the distribution line side, the second current flowing from the ground to the drop-in cable via the grounding wire flows in the reverse direction between the grounding wire and the shielding copper tape, so that the first current flows. This second current is canceled by the zero-phase current transformer.

Then, only the first detection current flowing from the ground to the service cable via the private substation equipment is the first detection current.
Is detected by the zero-phase current transformer. That is, the first zero-phase current transformer detects the first current flowing from the secondary side to the primary side.

The second zero-phase current transformer provided on the ground line flows from the ground and detects a second current. That is, the second current flowing from the secondary winding to the primary winding is detected.

For this reason, the first and second detection currents from the first zero-phase current transformer and the second zero-phase current transformer are in phase and input to the ground fault section discriminating device.

Further, the ground fault section discriminating apparatus of the present invention connects a predetermined substation facility connected to a high-voltage distribution line and a private substation facility that supplies power to a load at a voltage lower than the high voltage. It has a lead-in cable that draws power from a distribution line to a private substation, and the lead-in cable is provided with a shielding copper tape on each of a plurality of core wires, these shielding copper tapes are connected to each other, and a grounding wire is provided. And a first zero-phase current transformer having a polarity consisting of a primary side and a secondary side, which clamps and passes a ground wire and a lead-in cable together, and the ground wire is clamped. This is a ground fault section discriminating device connected to a second zero-phase current transformer having a polarity consisting of a primary side and a secondary side to be passed.

This ground fault section discriminating apparatus includes a first detection current from a first zero-phase current transformer and a second detection current from a second zero-phase current transformer.
The detected current is input and the presence or absence of the detected current, from the magnitude and phase difference of both currents, determine whether a ground fault has occurred in any section of the distribution line side, drop cable or private substation equipment The point is to inform.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of a ground fault section discriminating method in a private substation according to the present embodiment. This system uses a drop cable 3 for drawing three-phase power from the power supply side 1 of the drop cable to the private substation 2 side.
The ground wire 5 is grounded to the shield wires 4a, 4b, and 4c (shielding copper tape).

The drop cable 3 and the ground wire 5
And the zero-phase current transformer ZCT₁Together with
Zero-phase current transformer ZCT_cAnd the current I flowing through the ground line 5_cDetect
And this zero-phase current transformer ZCT₁Current i from₁And zero phase
Current transformer ZCT_cDetection current i _cAnd the ground fault section discriminating device 6
Input to the ground fault fault and the cable power supply side 1
Either the section of cable 3 or the private substation 2 side
Separate.

Further, on the power supply side 1 of the above-mentioned lead-in cable, the power receiving equipment 9 is provided on the lead-in column. The power receiving equipment 9 includes a high-voltage AC load switch (or high-voltage AC circuit breaker) that connects the three-phase distribution line 8 of the electric power company and the service cable 3, a non-directional ground fault relay GRy, and the like. It is connected to the distribution line 8 and the incoming cable 3.

The drop cable 3 is, for example, a high-pressure C
A V cable or the like is used, and the three core wires are each covered with an insulator, and the outer periphery is covered with a shielding conductive shielding material such as a copper tape to form shield wires 4a, 4b, and 4c. are doing. As described above, these shield wires are provided with the ground wires 5 connected to the shielded copper tapes of the shield wires 4a, 4b, 4c.

In general, the ratio of the ground capacitance of the incoming cable 3 to the ground capacitance (not shown) of the private substation 2 is in the range of 10: 1 to 1:10.

The zero-phase current transformers ZCT ₁ and ZCT _c are:
The split type is used so that it can be easily installed on the existing drop-in cable 3 or the grounding wire 5. In this case, a plurality of iron cores are stacked and superimposed, and the split joint is of a fitting type. Good. Also, as described later, ZCT ₁ , ZCT
_{Regarding c, it} is necessary to pay attention to the polarity, that is, the mounting direction in the present invention.

It is common among those skilled in the art to indicate the direction of a zero-phase current transformer by indicating the power supply side by K and the load side by L (see JIS C 1731 Instrument Transformer).
In the following description, in order to describe the direction (polarity) of each of ZCT ₁ and ZCT _c , the above-described power supply side is set as a primary side, described as a primary side K, and the load side is set as a secondary side. , The secondary side L.

The operation of the ground fault location judging system configured as described above will be described below with reference to FIGS. 2, 3 and 4.

FIG. 2 shows a zero-phase current transformer ZC when a ground fault occurs in the substation facility.
T _1, is an explanatory diagram for explaining the route of current flowing the ZCT _c. In FIG. 2, I _gc is a current flowing current back to the earth絡点via the earth capacity C _c of drop cables 3, I _g1 is via the earth capacitance C ₁ of the distribution line 8, I
_g is a current obtained by summing the current _Igc and the current _Ig1 .

For example, as shown in FIG. 2, when the ground fault occurs at a point of the bus of the private substation equipment 2, current I _g flowing from a point of the bus of the substation equipment 2 to the ground.

Further, as the the current _{I g} to flow into the ground, the current _{I g1} is grounded, the capacitance to ground _{C 1} of distribution lines 8, distribution line 8, the power receiving equipment 9, drop cables 3, private substation facilities It flows on the route of the ground fault point a.

Further, the current I_gFlows into the ground
Accordingly, the current I_gcIs ground, ground wire 5, shield wire 4
(4a, 4b, 4c), ground capacitance of the incoming cable 3
Quantity C _c, Drop cable 3, ground fault point of private substation 2
Flows in the route of a.

[0042] That is, in the zero-phase current transformer ZCT _1, a ground line 5, _{I gc} flowing shielded wire 4 passes through the core in opposite directions. Primary side K of zero-phase current transformer Zct ₁
A current I _gc toward the secondary side L from, since the current I _gc towards the primary K from the secondary side L passes simultaneously, so that both currents are canceled.

Therefore, the ZCT ₁ detects the sum of the current _Ig1 passing through the drop cable 3 from the power supply side 1 of the drop cable and the current _Igc passing through the drop cable via the ground capacitance of the drop cable 3.

That is, when a ground fault occurs on the private substation equipment 2 side, the zero-phase current transformer ZCT ₁ flows from the power supply side 1 of the service cable and the earth capacitance of the service cable, and is connected to the primary side K from the primary side K. Ground fault current I going to the next side L
_g (I _g ; I _gc + I _g1 ) is detected as a current I ₁ ,
And zero-phase current transformer ZCT _c provided on the ground line 5 detects the ground fault current I _gc directed flows from the ground side from the secondary side L to the primary K as a current I _c.

[0045] That is, when the ground fault occurs in the substation equipment side, the phase difference between the current _{I gc} and the current _{I g} is the phase is detected differently 180 ° (current _{I 1} and the current _{I c} 180
°).

The ground capacitance C of the drop cable 3
_c and the capacitance C ₁ of the distribution line 8
Since extremely larger the capacitance _{C 1,} the relationship of _{I 1} and _{I c} becomes _I 1 »I _c.

<When a ground fault occurs in the drop-in cable> As shown in FIG.
When a ground fault occurs at point, current _{I g} is shielded wire 4 from point b of drop cables 3 (4a, 4b, 4c) , a ground line 5, flows through a ground route.

[0048] That is, in the zero-phase current transformer ZCT _1, as shown in FIG. 3, the ground line 5, a current I _g flowing through the shielded wire 4 is passed through the core in opposite directions. Current I flowing from primary side K to secondary side L of zero-phase current transformer Zct ₁
Since the _g, and a current I _g toward the primary K from the secondary side L passes simultaneously, so that both currents are canceled.

[0049] This also, current _{I g1} is grounded, the capacitance to ground C1 of distribution lines 8, distribution line 8, the power receiving equipment 9, flows at the root of the land絡点b of drop cables 3.

Further, the current _Ig2 flows through the route of earth, the ground capacitance C _{2 of} the private substation ₂ , the bus of the private substation, and the point b of the drop cable 3.

[0051] That is, when the ground fault occurs in drop cables within 3, zero-phase current transformer ZCT ₁ is ground, flows from private substation equipment 2 side, the current I _g2 toward the primary K from the secondary side L Detected as current I ₁ and connected to ground line 5
Zero-phase current transformer ZCT _c provided in the flow into the ground through the ground wire 5 from the shielded wire 4, for detecting a current I _g flowing from the primary side K on the secondary side L as a current I _c.

[0052] That is, when the ground fault occurs in drop cables within 3, the phase difference of the ground fault current I _g and the current I _g2 is a phase is detected differently 180 ° (current I ₁ and the current I _c is 180 °).

The ground capacitance C of the private substation 2
₂ and the capacitance C ₁ of the distribution line 8
Since extremely larger the capacitance _{C 1,} the relationship of _{I 1} and _{I c} is the _I c »I _1.

[0054] <When ground fault occurs in the power supply side of the drop cables> 4, when the ground fault occurs at point c of the power supply side 1 of the drop cables, current I _g flowing to ground.

As a result, the current _Ig2 is grounded, the ground capacitance C _{2 of} the private substation ₂ , the bus of the private substation, the drop cable 3, the high-voltage AC load switch (or high-voltage AC circuit breaker) 9, the ground fault. It flows along the route at point C.

Meanwhile, current _{I gc} is ground, the ground line 5, the shield wire 4, the capacitance _{C c,} drop cables 3 of drop cables 3, high voltage AC load switch 9, flows at the root of the land絡点C.

[0057] That is, in the zero-phase current transformer ZCT _1, as shown in FIG. 4, the ground line 5, a current I _gc through the shielded wire 4 is passed through the core in opposite directions. Current I flowing from primary side K to secondary side L of zero-phase current transformer Zct _1
gc and the current _Igg from the secondary side L toward the primary side K pass at the same time, so that both currents are cancelled.

Therefore, only the current _Ig2 passing from the power supply side 1 of the drop cable to the private substation 2 is detected.

That is, when a ground fault occurs on the power supply side 1 of the drop cable, the zero-phase current transformer ZCT ₁ is connected to the ground,
It flows from private substation equipment 2 side detects a current I _g2 toward the primary K from the secondary side L as a current I1, and the zero-phase current transformer ZCT _c provided on the ground line 5, the ground,
It flows from the ground line 5 on the shielded wire 4, for detecting a current I _gc towards the primary K from the secondary side L as a current I _c.

[0060] That is, when the ground fault occurs in the power supply side 1 of the drop cables, the phase difference between the current I _g2 and the current I _gc is the phase is detected in-phase (current I ₁ and the current I _c is 0 ° ).

That is, the relationship between the current and the phase when a ground fault occurs in the power supply side 1, the drop cable 3, and the private substation 2 of the drop cable is as shown in Table 1.

It should be noted that, based on the ratio of the ground capacitance of the common drop cable 3 to the ground capacitance of the private substation 2, both the detected currents of ZCT ₁ and ZCT _c reach detectable levels, respectively. The phase of the currents I ₁ and I _c can be determined in most cases.

[0063]

[Table 1] In Table 1, only the I1 current flowing through the zero-phase current transformer ZCT _1, simply I the current through the zero-phase current transformer ZCT _c
It is shown as _c .

As shown in Table 1, the incoming cable 3
Current I1 flowing in the zero-phase current transformer ZCT ₁ provided in the
_If the phase relationship and the magnitude of the current Ic flowing through _c can be determined, it can be determined whether the ground fault location is in the private substation, in the service cable, or on the power side of the service cable.

The outline of this determination method will be described with reference to FIG. As shown in FIG. 5, the zero-phase current transformer ZCT ₁ and ZCT ZCT _C, ZCT 1, current flows through the ZCT _C I1, detects the current _{I c} (d1, d2), the detected current i ₁ , _ic is settled to a predetermined voltage (d3, d4).

Next, the detection current decision to determine whether the detected one of both or detection current i ₁ or detected current i _c of the detection current i ₁ and the detected current i _c (d5).

[0067] This detection current decision, upon detecting _{i 1} and _{i c} Both (d6), comparing the phase difference between both the detected current (d7).

Next, this phase difference is about 0 ° (in-phase).
Alternatively, it is determined whether or not the phase difference is about 180 ° (d8, d
9).

When the phase difference is about 0 ° (in-phase),
It is determined that the power supply side 1 of the drop cable is a ground fault (d1
0). The result is notified using an LED (light emitting diode).

[0070] Further, when the phase difference of about 180 °, compares the magnitude of the detection current _{i 1} and the detected current _{i c} (d11),
When the detected current _{i 1} is greater than the detection current _{i c} is (d1
2), it is determined that there is a ground fault in the private substation 2 (d1)
4). The result is notified using an LED.

[0071] Further, it is determined by the phase difference 180 °, when the detection current _{i c} is greater than the detection current _{i 1} (d13), and ground fault drop cables in the 3 (d18). LE result
Use D to inform. Further, when detecting only the detection current _{i 1} (d17), it is determined that a ground fault of the private substation equipment 2 (d14), when it detects only the detection current _{i c} (d1
6) is determined as a ground fault in the drop cable 3 (d1)
8).

Next, a specific configuration of a ground fault section discriminating apparatus using this discriminating method will be described below with reference to FIGS.

As shown in FIG. 6, the ground fault section determination device 6
The detection current i ₁ from the zero-phase current transformer ZCT ₁ which clamps the main body of the drop cable 3 and the ground line 5, and the ground line 5
And a detection current _ic from the zero-phase current transformer ZCT _C which clamps the current, and converts it into a predetermined voltage waveform with analog electric components and generates a signal for obtaining a phase difference. a part 8, to determine the detection current i _c, the presence of i ₁ from the settling circuit unit 8, and the determination result, based on the magnitude of the phase difference and the detected current, between the land絡区for calculating discriminating between ground絡区A determination operation unit 9 (also referred to as a CPU unit);

[0074] The land絡区inter determination computing unit 9, when the detected current i _c of the detection current i ₁ and the zero-phase current transformer ZCT _C by ZCT ZCT ₁ from settling circuit 8 inputs ,
Rotary switch S that determines the sensitivity of the detection current detection
W1 and SW2 are connected.

For example, depending on the setting of these rotary switches, 50 [mA], 100 [mA], 200 [m
A]...

Further, the ground fault section determining / calculating section 9 has a rotary switch SW3 for ignoring a ground fault for a predetermined second or less.
Is connected. By operation of the rotary switch SW3, 0.4 [s], 0.3 [s], 0.2 [s]
… The following ground faults can be ignored.

The ground fault section determining / calculating section 9 has an LED for notifying a ground fault on the power supply side 1 of the lead-in cable.
10 a (hereinafter referred to as an LED for informing the ground fault in the drop-in cable) and an LED 10 b (hereinafter, an LED for reporting a ground fault in the drop-in cable).
) And an LED 10c for notifying a ground fault in the private substation 2 (hereinafter referred to as a ground fault notification LE in the private substation).
D).

The configuration of the settling circuit section 8 and the ground fault section discriminating operation section 9 is configured as shown in FIG.

As shown in FIG. 7, the settling circuit section 8 includes current-voltage conversion circuits 12a and 12b, band-pass filters 13a and 13b, and ground fault detection circuits 14a and 14b.

The current-voltage conversion circuit 12a includes a zero-phase current transformer ZC that clamps the incoming cable 3 (main body, ground wire).
The detection current _{i 1} of T ₁ to voltage amplification.

[0081] The current - voltage conversion circuit 12a, the current _{I 1} flowing from the primary side K of the zero-phase current transformer ZCT ₁ on the secondary side L
And are detectable current I1 towards the primary K from the secondary side L of the zero-phase current transformer ZCT _1.

[0082] The current - voltage conversion circuit 12a, for example, when the zero-phase current transformer ZCT ₁ detects the detection current _{i 1} of 50 [mA], is converted to about 0.1 [V].

The band-pass filter 13a includes a differentiating circuit, an integrating circuit, and an amplifier (not shown).

[0084] Current - detection current signal i ₁ from the voltage converter circuit 12a, for example, 50 [Hz] or around the frequency of 60 [Hz], those within the frequency band of a constant width set arbitrarily on the upper and lower Is passing through.

[0085] ground fault detection circuit 14a, a current - type the detected current signal i ₁ from the voltage conversion circuit 12a, the signal (direction negative or positive) is sent by amplifying the difference between the ground level.

On the other hand, the zero-phase current transformer Z provided on the ground line 5
As shown in FIG. 7, a current-voltage conversion circuit 12b, a band-pass filter 13b, and a ground fault detection circuit 14b are connected in series to CT _c in the same order as described above.

The band pass filters 13a, 13b
, And outputs of the ground fault detection circuits 14a and 14b, and a voltage level conversion circuit 15 for converting each of the outputs to a predetermined voltage level is provided.

[0088] detection current _i 1 1 a detection current signal _{i 1} level converted signal of the band-pass filter 13a in this voltage level conversion circuit 15, a band-pass filter 13b
The signal obtained by level-converting the detection current signal _ic of FIG.
_{Called c} c.

Further, as shown in FIG. 7, the ground fault section discriminating operation section 9 includes a detected current discriminating circuit 18 and an MPU 19 (microcomputer).

In this embodiment, the detection currents i ₁ , i
_{Although c} is converted into a voltage, the detection currents i ₁ , i _c ,
i ₁ it will be described as a 1, _{i c c.}

The detection current determination circuit 18 is provided with a rotary switch.
Switches SW1, SW2 and SW3, and settling circuit 8
Detection current i₁Are the rotary switches SW1, S
When the setting conditions of W2 and SW3 are satisfied, MPU1
9 to output an output signal. For example, setting of SW1 and SW2
When the constant is set to 50 [mA], the detection current i ₁,
i_cIs at a voltage level equivalent to 50 [mA].
When the detected current i₁, I_cOutput to notify that
Send a force signal.

This output signal is sent when the time set by the rotary switch SW3 has been exceeded. For example, setting a time 0.3 [s], when SW1, SW2 setting is 50 [mA], the detection current _{i 1} is 50
Beyond a voltage corresponding to [mA], and when it continued 0.3 [s] or more, and sends an output signal indicating the detection of the detection current i _1.

When the MPU 19 is notified of the detection of the detection currents i ₁ and _ic or the detection of either of the detection currents i ₁ or _ic , the MPU 19 performs the processing described below, and
0b and 10c are turned on.

FIGS. 8 and 9 are flowcharts for explaining the operation of the MPU 19. The MPU 19 reads the port to which the output signal of the detection current determination circuit 18 is written (S
801).

Then, the type of the detected current is determined from the type of the output signal (flag) written to this port (S
803). For example, it is determined whether it is detection of both the detection currents i ₁ and _ic or detection of the detection currents i _{1 and ic} .

[0096] In step S803, when it is determined that the detection of _{i 1} and _{i c} sets the detection flag fi1, fic of the discrimination register (not shown) _{i 1} and _{i c} (S
805). Then, the detection current i _{1 1} of the detection current i ₁ of the band-pass filter 13a and the level conversion from the voltage level conversion circuit 15, the detection current i _{c c} which converts the level of the detection current i _c of the band-pass filter 13b to the voltage conversion, obtains the phase difference as a phase difference between the detection current _{i 1} and the detected current _{i c} (S807). Next, the phase difference is determined (S809).

If it is determined in step S809 that the phase difference is 180 °, the flag f180 indicating the phase difference of 180 ° is used.
Is set in the determination register Hi (S811).

That is, as described with reference to FIG. 2, the zero-phase current transformer ZCT ₁ flows from the power supply side of the service cable and the grounding capacitance of the service cable, and a ground fault from the primary side K to the secondary side L. current _{I g (I g; I gc} +
Detecting the I _g1) as a current I _1, and zero-phase current transformer ZCT _c provided on the ground line 5, a current ground fault current I _gc directed flows from the ground side from the secondary side L on the primary side K I
That is, it is detected as _c .

Alternatively, as described in FIG.
When a ground fault occurs in the drop cable 3, the zero-phase current transformer ZCT ₁ flows from the ground, the private substation 2, and the current Ig 2 flowing from the secondary side L to the primary side K is _converted to the current I.
Detected as _1, and the zero-phase current transformer ZCT _c provided on the ground line 5, flows to ground through the ground line 5 from the shield wire 4, the current I _g toward the secondary side L from the primary side K
_Is detected as the current Ic.

That is, this is either a ground fault in the private substation 2 or the service cable 3.

Next, the MPU 19 obtains the values of the detection currents I ₁ and I _C from the voltage level conversion circuit 15 (S81).
3) comparing the magnitude of _{I 1} and _{I C} (S815).

In step S815, the detected current I ₁
There when it is determined that a larger detection current I _C, sets a flag fk indicating that towards the detected current I ₁ is large value determination register Hi (S817).

That is, the phase difference between the current I ₁ flowing through the zero-phase current transformer ZCT ₁ provided on the drop cable 3 and the current I _C flowing through the zero-phase current transformer ZCT _C provided on the ground line 5 is 1
In 80 °, and thus set the current I ₁ is large.

[0104] Further, in step S815, when it is determined that the direction of current _{I C} flowing through the zero-phase current transformer ZCT _C greater, sets a flag fm indicating that the direction of current _{I C} large discrimination register Hi (S819).

Further, in step S809, i _c
And when the phase difference of i ₁ is determined as "0 °", both the current to set the flag f0 indicating a phase (S8
21). That is, as described in FIG. 4, the zero-phase current transformer ZCT ₁ is ground, flows from private substation equipment 2 side detects a current I _g2 toward the primary K from the secondary side L as a current I ₁ and zero-phase current transformer ZCT _c provided on the ground line 5, the ground, flows from the ground line 5 on the shielded wire 4, a current I _gc towards the primary K from the secondary side L
_Is detected as the current Ic.

[0106] Further, in step S803, when the type of the detected current is determined to either _{i 1} or _{i c,} the current determines whether _{i c} (S823).

[0107] In step S823, when it is determined that _{i c} sets a flag fic indicating the detection of the detection current _{i c} to determine register Hi (S825).

[0108] Further, in step S823, when it is determined that it is not a _{i c} sets the flag fi1 indicating that the detection of only the detection current _{i 1} to the discrimination register Hi (S827).

Then, as shown in FIG. 9, the MPU 19 reads each flag of the discrimination register Hi (S90).
1), the state of the determination register Hi is determined (S90)
3).

In step S903, when the flags fi1, fic, and f0 are set in the discrimination register Hi, it is determined that the incoming cable is on the power supply side 1 (S90).
5) LED 10a for ground fault notification on the power supply side of the incoming cable
Is turned on (S907).

In step S903, the flags fi1, fic, f180, and fk are stored in the discrimination register Hi.
Is set, or when only fi1 is set, it is determined that there is a ground fault in the private substation 2 (S90).
9), the ground fault notification LED 10b in the substation equipment is turned on (S911).

Further, in step S903, the flags fi1, fic, f180, f
When the set of m or only the fic is set, it is determined that the ground fault is in the drop cable 3 (S913), and the ground fault notification LED 10 in the drop cable is determined.
c is turned on (S915).

Then, it is determined whether or not the processing is completed (S91).
7) If not, the process returns to step S801 to determine and notify which section the ground fault has occurred as described above.

That is, as shown in FIG. 10, the program configuration of the MPU 19 is such that the detection current i ₁ from the zero-phase current transformer ZCT ₁ (the main body and the ground wire are clamped together) provided on the drop cable 3, and detecting current decision unit 20 detects the current i _c from the zero-phase current transformer ZCT _C provided is to determine whether the detected or one of the detection time to the line 5, i ₁ and i _c is detected At this time, a phase difference determining means 21 for determining and determining a phase difference between both currents, i ₁
And _ic are detected, a current value comparing means 22 for obtaining and comparing the magnitudes of both currents, and a detected current discriminating means 2
Determination result setting means 23 for setting the results of 0, the phase difference determination means 21 and the current value comparison means 22 in the determination register Hi
And whether or not the ground fault section is the power supply side 1 of the lead-in cable, the lead-in cable 3 or the private substation 2 based on the setting contents of the determination register Hi, and the ground fault section in which the LED is turned on based on the determination result. The determination means 24 is provided.

[0115]

As described above, according to the present invention, the polarities of the first zero-phase current transformer and the second zero-phase current transformer are reversed by utilizing the polarity of each zero-phase current transformer. By clamping and passing the incoming cable and ground wire together with a first zero-phase current transformer and clamping only the ground wire with a second zero-phase current transformer, Since the ground fault section (the section where the ground fault has occurred) is determined based on the phase difference of the current detected by the current transformer and the current value, the zero-phase current transformer alone can be used without using the zero-phase voltage detector. The effect of being able to notify whether a ground fault has occurred in any one of the distribution line side, the service cable, and the private substation is obtained.

Further, the first outgoing cable on the side of the high voltage distribution line near the processing location of the trifurcated branch pipe to be performed at the time of the power distribution work.
Since the zero-phase current transformer is provided, the ground wire drawn from the vicinity of the three-branch branch pipe can be easily clamped together with the drop-in cable. Therefore, it is provided in the incoming cable, the terminal processing of the incoming cable, and the like.
The above-mentioned each zero-phase current transformer can be easily attached to the existing line such as the ground wire connected to the shielding copper tape by using the split type, and each zero-phase current transformer can be connected to the ground fault section. A ground fault at a private substation, which does not have a large-scale ground fault discriminator just by connecting to the discriminator, occurs in any section of the distribution line side, service cable, or private substation. It is possible to easily inform the worker whether the operation is performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a ground fault section determination method in a private substation according to the present embodiment.

FIG. 2 is an explanatory diagram illustrating the flow of current when a ground fault occurs in a private substation.

FIG. 3 is an explanatory diagram illustrating a current flow at the time of a ground fault in a drop cable.

FIG. 4 is an explanatory diagram illustrating a flow of a current at the time of a ground fault at a drop cable power supply side.

FIG. 5 is an explanatory diagram illustrating determination of a ground fault section according to the present embodiment.

FIG. 6 is a schematic configuration diagram of a ground fault section determination device of the present embodiment.

FIG. 7 is a detailed configuration diagram of a ground fault section determination device.

FIG. 8 is a flowchart illustrating the operation of the MPU of the ground fault section determination device.

FIG. 9 is a flowchart illustrating the operation of the MPU of the ground fault section determination device.

FIG. 10 is a configuration diagram illustrating processing of an MPU of the ground fault section determination device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Power supply side of drop cable 2 Private substation equipment 3 Drop cable 4a, 4b, 4c Shield wire (shielding copper tape) 5 Ground wire ZCT ₁ Zero-phase current transformer ZCT _C Zero-phase current transformer 6 Ground fault section discriminating device

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] October 5, 1999 (1999.10.
5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0002

[Correction method] Change

[Correction contents]

[0002]

In general, high pressure areas絡継collector is provided between the distribution line and the premises of private substation equipment power company off-premises.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004] In an apparatus for discriminating a ground fault between an off-premise and a premise, it is necessary to discriminate an off-premise or on-premise ground fault location based on a phase difference between a zero-sequence voltage detected using a zero-sequence voltage detector and a ground fault current. General.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction contents]

[0008]

However, since the device for investigating the operation cause of the high voltage ground fault relay is non-directional, it is not easy to determine whether a ground fault has occurred outside or inside the premises. was there.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

[0014]

According to the present invention, a ground fault section in a private substation is provided with a predetermined substation connected to a high-voltage distribution line and a load supplied with a voltage lower than the high voltage. It has a drop-in cable that connects the private substation and draws the power from the distribution line to the private substation, and this drop-in cable is provided with a shielding copper tape on each of a plurality of core wires. They are connected to each other and to ground via a ground wire.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

[0034] Generally, the earth capacitance of the pull cable 3, the ratio of the earth capacitance of the private substation equipment 2 (not shown) is in the range of 10 to 1 to 1 to 10.

[Procedure amendment 7]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

[Procedure amendment 8]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

[Correction method] Change

[Correction contents]

FIG. 4

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hirokazu Asai F-term (reference) 5D058 EE04 EE06 EF03 EG15 EH01 EH03 5G066 AA20 in 5-4-1 Hiroo, Shibuya-ku, Tokyo, Japan

Claims (8)

[Claims] 1. A system according to claim 1, wherein a predetermined substation connected to a high-voltage distribution line is connected to a private substation that supplies power to a load at a voltage lower than the high voltage, and power from the distribution line is connected to the private substation. It has a lead-in cable to be led into a substation facility, wherein the lead-in cable is provided with a shielded copper tape on each of a plurality of core wires, these shielded copper tapes are connected to each other, and are connected to ground by a ground wire. A first having a polarity consisting of a primary side and a secondary side that clamps and passes the ground wire and the drop cable together.
A second zero-phase current transformer having a polarity consisting of a primary side and a secondary side, which clamps and passes the ground line, and a second zero-phase current transformer from the first zero-phase current transformer. 1 and the second detection current
And the second detection current from the zero-phase current transformer, and the presence or absence of the detection current, the magnitude of the two currents and the phase difference from the distribution line side, the drop cable or any of the private substation equipment A ground fault section discriminating apparatus for discriminating whether a ground fault has occurred in a section and notifying the section of the fault. 2. The first zero-phase current transformer and the second zero-phase current transformer are clamped to have opposite polarities when viewed from the ground side of a ground wire. Item 4. A ground fault section discriminating method in a private substation according to Item 1. 3. The first zero-phase current transformer clamps a lead-in cable on the distribution line side from a three-branch branch pipe that processes the cable terminal when the lead-in cable is led into the private substation. The ground fault section discrimination method in a private substation according to claim 1, wherein a ground wire is drawn from the cable terminal. 4. The ground fault section in a private substation according to claim 1, wherein the first zero-phase current transformer is clamped such that a primary side is the distribution line side. Judgment method. 5. A substation facility connected to a high-voltage distribution line and a private substation that supplies power to a load at a voltage lower than the high voltage by connecting power from the distribution line to the private substation. It has a drop-in cable to be led into the substation equipment, and this drop-in cable is provided with a shielded copper tape on each of a plurality of core wires, these shielded copper tapes are connected to each other, and are connected to the ground by a ground wire. And
A first having a polarity comprising a primary side and a secondary side for clamping and passing the ground wire and the drop cable together;
A zero-phase current transformer, and a ground fault section discriminating device connected to a second zero-phase current transformer having a polarity consisting of a primary side and a secondary side, which clamps and passes the ground wire, The ground fault section determination device may further include a first detection current from the first zero-phase current transformer and the second detection current.
And the second detection current from the zero-phase current transformer, and the presence or absence of the detection current, the magnitude of the two currents and the phase difference from the distribution line side, the drop cable or any of the private substation equipment A ground fault section discriminating device for discriminating and notifying whether a ground fault has occurred in a section. 6. The ground fault section determination device reads a first detection current detected by the first zero-phase current transformer and a second detection current detected by a second zero-phase current transformer. Means for determining whether the phases of both detected currents are in-phase or out-of-phase; and, if the phases are out of phase, when the first detected current exceeds the second detected current, Means for determining that a ground fault has occurred, and when the second detected current exceeds the first detected current, means for determining that a ground fault has occurred in the drop-in cable. A ground fault section discriminating apparatus, comprising: means for discriminating the distribution line side. 7. A means for discriminating a ground fault in the private substation when only the first detected current is detected, and the lead-in cable when only the second detected current is detected. The earth fault section judging device according to claim 6, further comprising means for judging a ground fault fault. 8. The first and second detection currents flowing from the primary side to the secondary side of the first and second zero-phase current transformers or from the respective secondary sides to the primary side. When the flowing first and second detection currents are detected, these first and second detection currents are detected.
A settling circuit unit that amplifies a second detected current to amplify a difference with respect to a ground potential and sends the amplified current, and detection of the first and second detected current values from the settling circuit unit, or one of the two. Is detected, and in the case of both detections, the phase, in-phase or out-of-phase is discriminated, and the result of this determination and the result of comparison between the two detected currents are set. 8. A ground fault section discriminating operation unit for discriminating whether a ground fault has occurred in any section of the track side, the drop cable, or the private substation equipment, and notifying the user of the fault.
The described ground fault section discriminating apparatus.