JP2001352663A - Method and apparatus for detecting electrical leak in low-voltage ground electrical circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of the conventional apparatuses that it is required to prevent the unessential operation of a relay in another transformer room when a ground fault accident is generated on the secondary side of a transformer in the other transformer room, when secondary-side grounds of transformers installed in a plurality of transformer rooms in a high-rise building or the like are formed to be of a common ground system. SOLUTION: A voltage Vo applied across the neutral point of an electric circuit in the ground fault accident and a ground is found, and a voltage Ve across a ground phase and the ground is found. A charging-phase current Io at this time is divided into a charging current Ico at the advance component of 90 deg. of the voltage Vo across the neutral point and the ground and a resistance component current Igr whose phase portion is identical to that of a voltage Vuo across a charging phase signal in the ground fault accident and the ground. When the current Igr becomes a set value or larger, a protective operation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an earth leakage detection and protection technique for a single-line ground circuit in a low-voltage ground circuit, and more particularly, to a technique in which a secondary ground of transformers in a plurality of substation rooms is set to a common ground.
The present invention relates to an earth leakage detection protection method and apparatus that prevents unnecessary operations in the event of a ground fault in another substation room.

[0002]

2. Description of the Related Art In recent years, a large number of substations (substations) (for example, on each floor) such as high-rise buildings are provided, and the secondary grounding of transformers in each substation is grounded by a common ground line. In many cases, a common grounding system is used. At that time, when a ground fault occurs on the secondary side of the transformer in another substation room, there are many cases where the leakage detector in another sound substation room operates unnecessarily.

The cause is that an accident current flows through the grounding resistance of the class B grounding of the common ground, a voltage is generated by the grounding resistance of the class B grounding, and the amount of the generated voltage increases the charging current, thereby causing a leakage relay. Unnecessary operation exceeding the set value of.

[0004] This phenomenon will be described in detail with reference to FIGS. FIG. 13 is a schematic diagram showing a case where a plurality of substations are installed in a high-rise building, and a secondary line of a transformer installed in each substation is grounded by a common grounding line.
A plurality of substations from A substation to D substation are provided in 0,
One line of the secondary side of the transformer in each substation is grounded to the class B by the common ground line 101. E _B shows this B species ground.

[0005] Fig. 14 shows that the secondary side of the transformer in the substation C in Fig. 13 is △ connected, the secondary side of the transformer in the substation A is distributed by single-phase three-wire, and the △ -connected v-phase and single-phase are connected. This is an example of a case where the neutral point of the three lines is grounded to the class B by the common grounding line 101.
When an over-ground fault occurs at point F, the earth leakage relay in the substation C may operate unnecessarily.

[0006] This is because, when the over-earth fault in path w of distribution lines A transformer chamber occurs, ground current Ig is ground絡点F B species ground as indicated by the dotted line from E _B - common grounding line 101 −
Flow through neutral point N-circuit w.

If this ground fault current Ig is large (over ground fault),
High voltage is generated by the ground resistance R _B of the B type grounding E _B.
For example, when the ground resistance is 10Ω and the ground fault current is 10A, 1
00V is generated. This voltage raises the voltage at the grounding point of the C substation, and the amount of the voltage rise causes the capacitance to ground C to rise.
The current flowing through w and Cu increases, and the ground capacitance (v phase) to ground Cv that did not flow in the absence of an accident.
Also, the zero-phase current transformer ZCT detects these, and if the current exceeds the set value of the earth leakage relay installed in the C substation, the earth leakage relay operates and the circuit breaker is cut off. This operation is an unnecessary operation because the operation in the C substation is normal.

[0008] Such unnecessary operation can be performed even when a plurality of transformers are installed in the same substation and a ground fault occurs on the secondary side of another transformer if the common grounding system is used. It can happen.

Conventionally, there is no known means for preventing unnecessary operation corresponding to such a phenomenon.

[0010]

The inventor of the present application has tried various measures to prevent the unnecessary operation as described above.

[0011] In the case of the neutral grounding circuit of the Y connection, unnecessary operation may occur if the charging current increases.
In the case of a connection, it is relatively easy to determine whether or not a load-side fault has occurred by comparing the phase of the voltage Ve between the neutral point and the ground with the zero-phase current Io flowing at the time of the fault.

In other words, in the case of a ground fault in another electric circuit, the zero-phase current Io of the own circuit (or on the load side) is a charging current, so that the voltage Ve between the neutral point and the ground at the time of the fault is different. Advance 90 °
In the case of a load-side accident, Ve and Io are almost 180 ° out of phase.

Therefore, by detecting the voltage between the neutral point and the ground and comparing the phase of this voltage with the current flowing through the zero-phase current transformer, unnecessary operation can be prevented. .

However, there is no neutral point in the △ connection and the single-phase single-wire ground circuit as in the Y connection, and the ground points are u, v, w.
Phase and the voltage between the ground point and the ground and the zero-phase current are compared when the other electric circuit is over-grounded.
The phase does not become 0 °, but changes and becomes undefined depending on the phase in which an accident occurred in another electric circuit.

It is also conceivable to create a neutral point by any method and compare the phase between the neutral point and the voltage between the ground and the zero-phase current. And the fault current may have the same phase, and it was found that it was not possible to discriminate only by phase comparison.

FIG. 15 and FIG. 16 are explanatory diagrams in the case where the phase difference between the created neutral point and the ground voltage Vo and the zero-phase current Io is compared, and FIG. 15 shows two transformers of three-phase three-wire △ connection. FIG. 16 shows a case in which each of the grounding phases of an electric circuit A in which one of the △ connections is grounded to a single line of the v phase and an electric circuit B in which the other is grounded to a single line of the w phase are grounded with a common grounding line 101.
Shows a vector diagram of the phase comparison.

Now, if an over-ground fault occurs at the F-point of the v-phase of the electric circuit B, as shown in FIG.
The ground potential A moves to the point g when there is no accident. In the sound side electric circuit A, the charging current Ioa, which is 90 degrees ahead of the voltage Voa between the neutral point and the ground, flows. This charge current Ioa is larger than the zero-phase current Io in a normal state.

At this time, the fault current Ig (including Iob) flows in the direction of w → u in the fault side electric circuit B, and the fault current Ig near the 90 ° leading phase of Vob flows. Therefore, it cannot be determined by comparing the phase of the voltage Vo between the neutral point and the ground.

FIGS. 17 and 18 show a circuit A in which the v-phase of the three-phase three-wire 三 connection is grounded by one line and a circuit B in which the other three-phase three-wire △ connection is grounded by the u-phase. When an over-ground fault occurs in the w-phase, the ground potential moves to the point g, and in the circuit A, the charging current Ioa, which leads Voa by 90 °, flows, and this current appears at a phase close to that of Ve by 180 °. And it is larger than Io in a healthy state.

At this time, the fault current Ig (including Iob) in the direction u → w flows on the fault side electric circuit B, and
° Ig close to the phase flows. Therefore, it cannot be determined by comparing the phase with Ve.

When the signal of the zero-phase current transformer inserted into the ground line is used as a reference, the phase of the current flowing through this zero-phase current transformer is the same as that of Ve, but is determined to be the same signal. Becomes impossible.

Further, the voltage between the neutral point of the electric circuit and the ground is Vo
And a current Io in the same phase as the voltage Vo is calculated to obtain a resistance component current Igr.
We tried to operate the earth leakage relay for gr, but there is no problem when it is not an over-ground fault, but at the time of over-ground fault, the voltage Ve is generated between the ground phase and the ground by the class B ground resistance. Will not be accurate.

That is, since the value of the true resistance component current Igr is a current component due to the insulation resistance generated between the grounded phase and the ground, it becomes a current having the same phase as the voltage between the grounded phase and the ground. In the event of an over-ground fault, even if the in-phase component between the neutral point and the voltage Vo between the ground and the ground is obtained, it is not the value of the true resistance component current Igr, but smaller than the actual Igr, and may not be detected. .

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to provide a leakage detection and protection device which does not require unnecessary operation even when a common ground is used for a △ connection and a single-phase single-wire ground circuit.

[0025]

According to the present invention, a ground fault current at the time of an over ground fault is a current flowing as an insulation resistance due to a voltage generated between the ground fault phase and the ground at the time of an over ground fault. It was done with attention.

That is, in the method of detecting leakage of a single-wire ground circuit on a low-voltage piezoelectric circuit, the voltage between the neutral point and the ground and the voltage between the ground phase and the ground at the time of the ground fault are determined, and the zero-phase current at that time is calculated as 90 ° of the voltage Vo between the neutral point and the ground
The voltage is divided into a resistance component current of the same phase as the voltage between the charge phase of the lead component and the charging phase and the ground changed at the time of the ground fault, and a predetermined protection operation is performed when the resistance component current exceeds a preset level. It is something to do.

The voltage between the neutral point and the ground is determined from the voltage between the charging phase and the ground, and the voltage between the ground phase and the ground which are changed at the time of the ground fault. The half point of the line voltage Vu is defined as the neutral point N of the electrical circuit, and the point of 1 / √3 is defined as the neutral point N of the intermediate phase of each charging phase in the 線 connection single line ground circuit. It can be obtained from the voltage.

In addition, as a device, there is provided a leakage detection and protection device for a single-wire grounding circuit on a low-voltage circuit, a charging-phase-to-ground voltage detecting means for detecting a voltage between a charging phase and a ground of a single-phase single-grounding circuit, Ground phase-to-ground voltage detecting means for detecting the voltage generated at the grounding resistance of the ground, zero-phase current detecting means for detecting the zero-phase current, and inputting a detection signal from each of these detecting means to cause a fault in the own circuit. It is configured to have an earth leakage relay for judging whether or not it is.

In the above-mentioned earth leakage relay, the voltage detected by the charging phase-to-ground detecting means at the time of a ground fault is Vuo, the voltage detected by the grounding phase-to-ground voltage detecting means is Ve, and the zero-phase current The line voltage Vu is obtained from Vuo and Ve with the zero-phase current detected by the detection means as Io, and a half of the line voltage Vu is set as the neutral point N of the electric circuit at the time of the ground fault.
The neutral point N and the ground-to-ground voltage are set to Vo, and the zero-phase current Io is advanced by 90 ° with respect to Vo, and the charged charge current Ico of the phase and Vu
It is desirable to divide the current into a resistance component current Igr having the same phase as that of o and to operate when the resistance component current Igr exceeds a preset detection level.

In the case of a three-phase three-wire △ connection or a single-phase single-circuit grounding circuit, a neutral point-to-ground voltage detecting means for detecting a voltage between the neutral point and the ground, and a class B grounding resistance Ground phase-to-ground voltage detecting means for detecting the voltage generated at
The configuration includes a zero-phase current detecting means for detecting a zero-sequence current, and an earth leakage relay for inputting detection signals of each of these detecting means and determining from each detection signal whether or not an accident has occurred in its own circuit.

The above-mentioned earth leakage relay uses the voltage detected by the neutral point-to-ground voltage detecting means at the time of a ground fault to Vo,
The voltage detected by the ground phase-to-ground voltage detecting means is Ve, the current detected by the zero-phase current detecting means is Io, the voltage between the neutral point and ground when Ve is zero is Vn, and the zero-phase current is detected. Where In is the charging current flowing to the ground capacitance with the current detected by the means, I at the time when the ground fault does not occur
n is obtained and stored, Vn is calculated from Vo and Ve when a ground fault occurs, and the charging current Ico during a ground fault is calculated from the ratio of Vo and Vn, and this is calculated from the zero-phase current Io. I
co is subtracted to obtain a resistance component current Igr.
It is desirable to operate when gr exceeds a preset level.

As another means, a neutral point-to-ground voltage detecting means for detecting a voltage between the neutral point and the ground, and a voltage between each phase of the charging phase and the ground are provided. Phase-to-ground voltage detecting means for detecting the zero-phase current, zero-phase current detecting means for detecting the zero-phase current, and inputting the detection signals of these detecting means to determine from each signal whether or not the circuit is faulty. It is configured to have an earth leakage relay.

In this case, the earth leakage relay is such that the voltage detected by the neutral point-to-ground voltage detecting means at the time of a ground fault is Vo, and the voltages detected by the respective charging phase-ground voltage detecting means are Vuo, V
wo, the zero-phase current Io detected by the zero-phase current detection means at that time, and this zero-phase current Io is taken as a 90 ° leading phase with respect to Vo, and the charging current Ico of the zero-phase current Io is taken as Vu.
It is desirable that the resistance component current Igr be obtained by dividing into fault currents flowing as common-mode components of o and Vwo, and to operate when the resistance component current Igr exceeds a preset level.

[0034]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which a line v on the secondary side of the single-phase transformer Tr is grounded. In the first embodiment, a charging phase-ground voltage detecting means 10 for extracting a voltage Vu between the charging phase u and the ground, a ground phase v
And a ground phase-to-ground voltage detecting means 20 for extracting a voltage Ve between the ground and the ground, a zero-phase current detecting means 30 for detecting a zero-phase current Io of the electric circuit, and a detection signal detected by each of these detecting means. It is configured by an earth leakage relay 40 that performs processing and calculates a ground fault current flowing with insulation deterioration to perform a protection operation.

The charging phase-to-ground voltage detecting means 10 includes capacitors 10C ₁ , 10C between the charging phase u and the ground (ground) E.
The voltage between the charging phase u and the earth by Kontensa partial pressure by connecting the C ₂ (hereinafter, referred to as the charging phase-ground voltage) is taken out of Vu. This charge phase / ground voltage Vu (V
The detection of the change in uo) is not limited to the capacitor voltage division, and a transformer or a resistor may be used.

Similarly, the ground phase-to-ground voltage detecting means 20 extracts a voltage Ve between the ground phase v and the ground E (hereinafter, referred to as a ground phase-to-ground voltage) by dividing the voltage with the capacitors 20C ₁ and 20C ₂ .

The zero-phase current detecting means 30 extracts a zero-phase current Io using a zero-phase current transformer. The detection signal detected by each of these detecting means is taken into the earth leakage relay 40 and is calculated (calculated) by the calculating means 42 to calculate the resistance component current Igr of the ground fault current.

The earth leakage relay 40 has terminals Z1 and Z2 for receiving a zero-phase current, a terminal Le for receiving a ground phase / ground voltage Ve, and a terminal L for receiving a charging phase / ground voltage Vu.
u and a ground terminal E.

FIG. 2 is a conceptual diagram of the earth leakage relay 40.
1 and Z2, the zero-phase current Io is amplified by the amplifier 31 and input to the A / D converter 41. Similarly, terminals Le and E
Phase-to-ground voltage Ve input from the terminal, and charging phase-to-ground voltage Vu input from terminals Lu and E.
uo) with the respective amplifiers 21 and 31,
This is input to the A / D converter 41. A / D converter 4
Each of the detection signals input to 1 is A / D converted here and input to the calculating means 42.

In the arithmetic means 42, the A / D converted I
The respective signals of o, Ve, and Vu are detected through a digital filter 42a to detect their absolute values and phases, and are processed by an arithmetic processing unit 42b.
Is input to The arithmetic processing unit 42b performs the vector arithmetic processing shown in FIG. 3 according to the flowchart shown in FIG. 4 to obtain the resistance component current Igr.

The earth leakage relay 40 has an operation sensitivity / time limit setting unit 43 and an operation output relay 44.

[0043] The charging phase u and the ground voltage of the ground fault there is no state and Vu, ground resistance R _B of Class B ground E _B by over-ground fault
In this case, the voltage generated by the current flowing to the power supply rises with respect to the ground potential. At this time, the voltage between the charging phase and the ground changed by the rise of Ve is Vuo, and the zero-phase current detected by the zero-phase current transformer is Io. when, if over-ground fault occurs at point F of Figure 1, the ground fault current flows to the ground resistance R _B of the B type grounding E _B, by this current, the potential of the ground point is elevated Vuo. At this time, the charging current Ico also flows to the ground capacitance Cv of the ground phase v. This charging current Ico is, as shown in FIG. 3, a vector of a current Iuco having a leading 90 ° phase of the charging phase-to-ground voltage Vuo and a current Ieco flowing at a leading 90 ° phase of the grounding phase u and the ground voltage Ve. It becomes a composition.

On the other hand, the resistance component current Igr flowing due to insulation deterioration is a current flowing due to insulation deterioration with respect to the charging phase u and the ground E, and therefore has the same phase as the changed charging phase / ground voltage Vuo. Therefore, the current obtained by subtracting the charging current Ico from the zero-phase current Io detected by the zero-phase current detection means 30 becomes the resistance component current Igr. That is, since the charging current Ico is in a phase leading by 90 ° with respect to the neutral point N and the ground-to-ground voltage Vo, the zero-phase current Io is changed to a phase component of the charging current Ico and a current having the same phase component as the charging phase voltage Vuo. By dividing, the resistance component current Igr is obtained.

When the resistance component current Igr exceeds the set level set by the operation sensitivity / time limit setting unit 43, the operation output relay 44 is operated after the set time to shut off the circuit breaker or to issue an alarm. The necessary protection operation is performed by means of (1).

FIG. 4 is a flowchart for performing the above-described vector calculation of FIG. 3 in the arithmetic processing unit 42b. First, in steps S1 and S2, the neutral point N of the electric circuit is first obtained. This neutral point N is determined by the voltage Vu between the charged phase and the ground changed during the ground fault.
o and the ground phase / ground voltage Ve (the voltage generated in the class B ground resistance) to the line voltage Vu (the charging phase when there is no ground fault)
(Equal to the ground-to-ground voltage) (step S1), and a half point of this line voltage Vu is set as the neutral point N of the electric circuit, and the voltage Vn between this neutral point N and the ground phase v (Ve is zero) When the voltage)
Is obtained (step S2). Next, the neutral point N and the ground phase V
A neutral point / ground voltage Vo is obtained from the ground voltage Vn and the ground phase / ground voltage Ve (step S3). Next, the leading 90 ° phase of the neutral point / ground voltage Vo is determined (step S4). Next, in step S5, the zero-phase current Io is set to a current Ico having the same phase component as the advance 90 ° of the neutral point / ground voltage Vo.
And a resistance component current Igr having the same component as the charging phase / ground voltage Vuo.

Then, the resistance component current Igr is compared with a preset operation sensitivity setting level (detection level) (step S6), and if it exceeds the preset level, it is determined whether or not a preset time period has passed. Then, when it exceeds (step S7), the operation output relay 44 is turned on (step S8), and a necessary protection operation is performed.

If the set level is not reached in step S6, the timer is preset in step S9. These operations are repeated for a predetermined time and monitored.

The above is the case where the neutral point-to-ground voltage Vo is obtained by calculation, but this can also be obtained by measurement.

That is, as shown in FIG. 5, a neutral point-to-ground voltage detecting means 50 (hereinafter abbreviated as Vo detecting means) is provided in place of the charging phase-to-ground voltage detecting means 10. The Vo detecting means 50 forms a neutral point N by connecting a charging phase u and a grounding phase v via capacitors 50C ₁ and 50C ₂ provided respectively, and forms the neutral point N, and the neutral point N and the earth (ground) E. the dividing capacitors 50C ₃ arranged between, take out the voltage Vo-neutral-ground from both ends of the capacitor 50C _3. Then, using the extracted (measured) neutral point / ground voltage Vo, the arithmetic processing shown in the flowchart of FIG. 6 is performed.

In this case, since the neutral point-to-ground voltage Vo has already been obtained by measurement, step 3 shown in FIG.
The calculation up to changes. That is, the neutral point / ground voltage Vo, the ground phase / ground voltage Ve,
The neutral-to-ground voltage when the ground-to-ground voltage Ve is zero is Vn,
Assuming that the charged phase and the ground voltage Vu (line voltage) when there is no accident, Vn is obtained from Vo and Ve in step S1 (see FIG. 3), and Vn is obtained by doubling Vn (step S1).
2) The voltage Vuo between the charging phase and the ground at the time of the ground fault is determined from Vu and Ve. (Step S3). Step S
4 and thereafter are the same as those in step S4 in FIG.

The above description has been given of the case of an over-ground fault. However, even at the time of a micro-ground fault, only the ground-phase / ground voltage Ve is reduced, and Vo = Vn, and the above-mentioned calculation is established.

As described above, since the current flowing due to the deterioration of the insulation resistance can be used as the set value of the operation sensitivity, it is possible to set the sensitivity to a high level, and in the circuit without the deterioration (accident) of the insulation resistance, Since there is no current, there is no unnecessary operation.

FIG. 7 is an explanatory view of the second embodiment of the present invention, in which a three-phase three-wire single-wire ground is used. It comprises a ground phase-to-ground voltage detecting means 20, a neutral point-to-ground voltage detector 60, a zero-phase current detecting means 30, and an earth leakage relay 40.
Parts having the same functions as those in FIGS. 1 and 5 are denoted by the same reference numerals, and detailed description is omitted.

The neutral point-to-ground voltage detecting means 60 connects one electrode of capacitors Cu, Cv and Cw to each of the three phases u, v and w and connects the other electrode in common. A neutral point N is formed, a capacitor Co is inserted between the neutral point N and the earth (ground) E, and a neutral-point / ground voltage Vo in three phases is extracted from both ends of the capacitor Co. The detection signal detected by each of these detecting means is input to the earth leakage relay 40. That is, the zero-phase current Io detected by the zero-phase detecting means 30 is supplied to the Z ₁ and Z ₂ terminals of the earth leakage relay 40, the neutral point / ground voltage Vo is supplied to the terminal NE, and the ground phase / ground voltage is outputted. V
e is input to the terminals Le-E, respectively, and is subjected to arithmetic processing by the arithmetic processing unit 42b of the arithmetic means 42 of the earth leakage relay 40 as in FIG. FIG. 8 shows a vector diagram to be calculated, and FIG. 9 shows a flowchart of the calculation process.

Now, similarly to the above, the ground phase / ground voltage V
e, the neutral point and ground voltage Vn when this voltage Ve is zero,
Assuming that the neutral point / ground voltage is Vo and the zero-phase current is Io,
In the single-line grounding circuit, the charging current Ico as shown in FIG. 8 flows through the load-side capacitance to the ground even when the grounding accident does not occur. This charging current Ico is Vo
It is possible to determine that no accident has occurred. At that time, if the ground-phase / ground voltage Ve is zero, Vo = Vn. If Ve is present, Vo = Vn. Vn is obtained (step S1). Next, in step S2, the ratio Vo / Vn between Vo and Vn is determined.

In step S3, it is determined whether or not Io is advanced by 90 °. If it is advanced by 90 °, Io ÷ (Vo / Vn) is obtained, and charging current In when Ve is zero (when there is no accident) is obtained.
Is obtained and stored (steps S4 and S5).

Next, at step S6, Ico is subtracted from Io at the time of the ground fault to obtain a resistance component current Igr. This resistance component current Igr is zero in a circuit without an accident.

The calculated resistance component current Igr is compared with the set level in step S7, as in FIG. 4, and when it exceeds the set level, the operation output relay is operated after the set time limit (step S8) (step S9). .

If Igr is smaller than the set level, the timer is reset (step 11), the process is terminated, and the process is repeated.

Next, if Io is not 90 ° ahead of Vo in step S3, a ground fault has occurred. In step S10, when Vo and Ve change, Vn is changed from Vo and Ve at that time. And Vo at the time of over ground fault
The ratio of / Vn is multiplied by the stored In to obtain the charging current Ico at the time of the ground fault, and the process proceeds to step S6.

Even if the ground phase / ground voltage Ve is generated due to the influence of the charging current of the other electric circuit by the common grounding method, the zero-phase current Io is maintained at the neutral point, unless there is an accident on the load side of the own circuit. Since the voltage appears 90 ° ahead of the ground voltage Vo, the above calculation is valid.

FIG. 7 shows the case of three-phase three-wire single-wire grounding. However, the same processing can also be realized with the single-phase single-wire grounding circuit of FIG. In this embodiment, similarly to the first embodiment, the current flowing due to the deterioration of the insulation resistance can be used as the set value of the operation sensitivity, and the sensitivity can be set high.

FIG. 10 is an explanatory view of the third embodiment of the present invention, which is basically the same as the method of the first embodiment, except that in the case of three-phase three-wire single-line grounding, the charging phase There is a U-phase and a V-phase, and it is not possible to determine which phase has a ground fault, or as described in the related art, whether it is on the load side or a ground fault on another electric circuit.

Therefore, the neutral point-to-ground voltage detecting means 60 for the three phases as shown in FIG. 7 and the charging phase-to-ground voltage detecting means 10u, 10w and A zero-phase voltage detecting means 30 is provided, and a detection signal of each of these detecting means is input to the earth leakage relay 40 to perform a vector calculation process to obtain a resistance component current Igr.

The voltage between the neutral point and the ground at the time of
o, the voltage between each charging phase and ground is Vuo and Vwo,
At this time, assuming that the zero-phase current detected by the zero-phase current transformer is Io, the charging current Ico passes through the load-side ground capacitance on the load-side ground line even in a state where the grounding accident does not occur as described above. Flowing. This charging current Ico advances by 90 ° with respect to Vo, and as described above, it can be determined that an accident has occurred.

FIG. 11 shows a flowchart of the calculation processing according to the third embodiment. In FIG. 5, a leading 90 ° phase of Vo is obtained in step S1, and then Vo / V
n is obtained (step S2). Io is V in step S3
It is determined whether or not o is advanced by 90 °. If the vehicle is advanced by 90 °, there is no accident. Therefore, the charging current In when there is no accident is obtained by In = Io ÷ (Vo / Vn). It is stored in step S5. Next, at step S6, Io
Is subtracted from Ico to obtain Igr and compare it with the set detection level. The following processing is performed in the same manner as in FIG.

If Io is not 90 ° ahead of Vo in step S3, it is determined in step S5 whether or not the charging current In when there is no accident is stored beforehand. Similarly, the charging current Ico is set to Ico = I
It is determined by n × (Vo / Vn) (step S12). Steps S6 to S10 are the same as those in FIG. When In is not stored in step S11,
The processing is performed in steps S13 to S15. That is, when there is a ground fault, the fault current is Vuo or Vwo of the fault phase.
And the charging current component Ico of the zero-phase current Io is Vo
, The phase is advanced by 90 °, and divided into in-phase components of Vuo and Vwo to obtain Igr.

In step S13, the vector operation shown in FIG. 12A is performed to obtain Vgr Igr. That is, Io is V
The phase is divided into an in-phase component (Ico) of 90 ° and an in-phase component (Igr) of Vuo.

Next, in step S14, the vector operation shown in FIG. 12B is performed to obtain Igr of Vwo. That is, Io
Is divided into an in-phase component (Ico) with the lead 90 ° of Vo and an in-phase component (Igr) with Vuo.

In the next step S15, the average of the absolute values of the respective Igrs is obtained, and the average is compared with the set level of the Igr (step S7). If the average is larger than the set level, the operation relay is turned on after the set time limit. .

In the above case, at the time of an over-ground fault, a current much larger than the operation setting sensitivity flows. Therefore, the operation may be performed with the larger value of Igr without taking the average value of each phase.

In a normal insulation deterioration accident that does not lead to an overground fault,
Ground phase / ground voltage is V due to the influence of charging current of other circuits.
e, Ig of each phase of Vuo, Vwo
When the value of r is different and the charge current Ico is unknown, it cannot be determined which phase has insulation deterioration. Therefore, the following is considered. When the charging current In in the no-accident state is obtained by the detection method of the second embodiment, Igr having a value equal to or close to the current obtained by subtracting Ico from Io is used. When a load with poor insulation is applied, and In is not determined by the above detection method, or when neither can be determined, the average value of each Igr is obtained and used as the Igr value. The error of the Igr obtained by the average value is not so large as the difference and is within a range that does not cause a problem in practical use within the allowable range of the earth leakage relay.

When Ve is small, Vo ≒ Vn, and each Igr becomes equal, and the error becomes small.

[0075]

As described above, according to the present invention, the resistance component current at the time of a ground fault is calculated and obtained, and it is determined whether or not a ground fault has occurred in the own circuit based on the resistance component current. It works. (1) It is possible to supply an earth leakage relay without unnecessary operation even with a common grounding of the connection and single-phase single-wire grounding circuit. (2) There is a problem that the leakage current does not increase unless the resistance becomes low due to the influence of the charging current in an electric circuit having a large capacitance to the ground. Can be set. (3) There is no need to superimpose another detection signal, there is no effect on the electric circuit, and there is no need for a superposition signal generator.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is a conceptual diagram of the present invention.

FIG. 3 is a vector diagram according to the first embodiment of the present invention.

FIG. 4 is a flowchart of the calculation means of FIG. 2;

FIG. 5 is an explanatory view of a second embodiment of the present invention.

FIG. 6 is a flowchart according to a second embodiment;

FIG. 7 is an explanatory view of a third embodiment of the present invention.

FIG. 8 is a vector diagram according to the third embodiment.

FIG. 9 is a flowchart of a third embodiment.

FIG. 10 is an explanatory diagram of a fourth embodiment of the present invention.

FIG. 11 is a flowchart of the fourth embodiment.

FIG. 12 is a vector diagram of the fourth embodiment.

FIG. 13 is an explanatory diagram of a common grounding method in a high-rise building.

FIG. 14 is an explanatory diagram of a common grounding system.

FIG. 15 is an explanatory diagram of a common grounding method in a three-phase three-wire △ connection.

FIG. 16 is an explanatory diagram of the vector in FIG. 15;

FIG. 17 is an explanatory diagram of another example of the common grounding method when three-phase three-wire connection is performed.

18 is an explanatory diagram of the vector in FIG. 17;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Charge phase-ground voltage detection means 20 ... Ground phase-ground voltage detection means 30 ... Zero-phase current detection means 40 ... Earth leakage relay 41 ... A / D conversion part 42 ... Calculation means 43 ... Operation sensitivity and time limit setting part 44: operation output relay 50, 60: neutral point / ground voltage detecting means

Claims (8)

[Claims] In a method for detecting a short-circuit of a single-wire ground circuit on a low-voltage circuit, a voltage between a neutral point and a ground and a voltage between a ground phase and a ground at the time of a ground fault are obtained, and a zero-phase current at that time is determined. The voltage between the neutral point and the ground is divided into a charging current of a 90 ° lead component and a resistance component current of the same phase as the voltage between the charging phase and the ground changed during the ground fault, and the resistance component current is set in advance. A predetermined protection operation when the set level is exceeded. 2. The voltage between the neutral point and the ground is determined from the voltage between the charging phase and the ground, and the voltage between the charging phase and the ground changed at the time of the ground fault, and the neutral voltage is calculated from the line voltage. Find point N,
2. The method according to claim 1, wherein the voltage is obtained from the voltage between the neutral point N and the ground. 3. A leakage detecting and protecting device for a single-wire grounding circuit in a low-voltage circuit, comprising: a charging phase-ground voltage detecting means for detecting a voltage between a charging phase of a single-phase single-grounding circuit and ground;
Ground phase-to-ground voltage detecting means for detecting the voltage generated at the ground resistance of the seed ground, zero-phase current detecting means for detecting the zero-phase current, and inputting the detection signals of these detecting means to the own circuit. An earth leakage detection protection device comprising an earth leakage relay for judging whether or not an accident has occurred. 4. The earth leakage relay comprises a voltage Vuo detected by the charging phase-to-ground detecting means at the time of a ground fault, a voltage Ve detected by the grounding phase-to-ground voltage detecting means, and a zero-phase current detecting means at that time. Let Vuo and V
e, a line voltage Vu is obtained, a half point of the line voltage Vu is defined as a neutral point N of an electric circuit at the time of a ground fault, and the neutral point N and the ground-to-ground voltage are defined as Vo. Io is 90 to Vo
15. The method according to claim 14, wherein the charge is divided into a charge component Ico having an advanced phase and a resistance component current Igr having the same phase component as Vuo, and is operated when the resistance component current Igr exceeds a preset detection level. 3. The leakage detection and protection device according to 3. 5. A leakage detecting and protecting device for a single-wire ground circuit on a low-voltage circuit, wherein a neutral point for detecting a voltage between a neutral point and the ground is detected by a three-phase three-wire △ connection or a single-phase circuit on a single-wire ground circuit. Ground-to-ground voltage detecting means, ground phase-to-ground voltage detecting means for detecting a voltage generated at the grounding resistance of class B grounding, zero-phase current detecting means for detecting zero-phase current, and detecting signals of these detecting means. An earth leakage detection and protection device comprising: an earth leakage relay that inputs and detects from each detection signal whether or not the circuit is an accident. 6. The earth leakage relay detects a voltage detected by the neutral point-to-ground voltage detecting means at the time of a ground fault, Vo, a voltage detected by the grounding phase-ground voltage detecting means to Ve, and then detects a zero-phase current. When the current detected by the means is Io, the voltage between the neutral point and the ground when Ve is zero is Vn, and the charging current flowing through the ground capacitance with the current detected by the zero-phase current detecting means is In. The In at the time when the ground fault does not occur is obtained and stored, and Vo and V at the time when the ground fault occurs are obtained.
e, Vn is calculated from the ratio of Vo and Vn, and the charging current Ico at the time of ground fault is obtained. This Ico is subtracted from the zero-phase current Io to obtain the resistance component current Igr, and the current Igr is set to a preset level. 6. The leakage detection protection device according to claim 5, wherein the leakage detection protection device operates when it exceeds. 7. A neutral point-to-ground voltage detecting means for detecting a voltage between a neutral point and the ground of a three-phase three-wire single-line grounding circuit, and a charging phase. Charging phase-to-ground voltage detecting means for detecting the voltage between each phase and the ground, zero-phase current detecting means for detecting the zero-phase current, and a detection signal of each of these detecting means is inputted, and the respective circuits receive An earth leakage detection and protection device comprising: an earth leakage relay that determines whether or not an accident has occurred. 8. The earth leakage relay has a voltage Vo detected by the neutral point-to-ground voltage detecting means and a voltage Vuo, Vwo detected by each charging phase-to-ground voltage detecting means at the time of a ground fault. The zero-phase current Io detected by the zero-phase current detection means is defined as the zero-phase current Io.
o is taken as 90 ° ahead of Vo, and Vuo, V
8. The method according to claim 7, wherein the resistance component current Igr is determined by dividing the fault current flowing as each in-phase component of wo into a fault current, and the resistance component current Igr is operated when the resistance component current Igr exceeds a preset level. Leakage detection protection device.