JP3324387B2 - Ground fault detecting circuit and circuit breaker provided with ground fault detecting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault detecting circuit for detecting a ground fault in an ungrounded AC line and a circuit breaker provided with the ground fault detecting circuit.

[0002]

2. Description of the Related Art FIG. 13 is a circuit diagram showing an example of a conventional ground fault phase detection circuit disclosed in Japanese Patent Publication No. 6-19407. In FIG. 13, reference numerals 1a, 1b, and 1c denote three-phase balanced power supplies of a, b, and c phases whose voltages are ea, eb, and ec, each of which is shifted by 120 °. 2a, 2b, 2c
Are distribution lines of each phase connected to the power supplies 1a, 1b, 1c, respectively, and 3a, 3b, 3c are distribution lines 2a, 2b, 2
The ground capacity of c. Reference numeral 4 denotes a ground fault resistance generated in the distribution line 2a. It is assumed that the distribution line 2a is grounded by the resistance 4 having the resistance value Rg.

[0003] 5a, 5b, 5c are voltage dividers, and depending on the capacity, the voltage Vaa, Vbb, of the distribution lines 2a, 2b, 2c.
Vcc is divided. 6a, 6b and 6c are operational amplifiers, which are output voltages v of the voltage dividers 5a, 5b and 5c.
It calculates and outputs voltages v1, v2, and v3 described later based on a, vb, and vc. Reference numeral 7 denotes a ground resistance having a resistance value RN, which grounds the neutral point P of the power supplies 1a, 1b, and 1c.

When the ground fault is detected, the ground fault phase detection circuit issues an alarm command to an alarm device (not shown) to start inspection and restoration.

FIG. 14 is a vector diagram relating to the ground fault phase detection circuit of FIG. For example, when a ground fault of the resistance 4 occurs in the distribution line 2a, the current from the power supply 1a flows from the distribution line 2a to the ground through the resistance 4 having the resistance value Rg, and from the ground to the ground resistance 7 having the resistance value RN. , 1b, 1c generate a ground voltage vn at the neutral point P. At this time, the distribution line 2a
Is the voltage across the resistor 4 and is Vaa. The voltage dividers 5a, 5b, 5c are Vaa, Vbb, Vc
Output the divided voltages va, vb, vc of c. The ground fault phase is determined based on the divided voltages va, vb, and vc. The operation principle will be described using the voltage Vaa of the distribution line and the like.

FIG. 14 shows a voltage ea, v with the ground point being R.
It shows the relationship between n and Vaa. ea is the vector sum of vn and Vaa, and the ground point R is on the circle diagram 8 whose diameter is the voltage ea based on the neutral point P. The ground point R is determined by the resistance value Rg of the ground fault resistor 4 and the ground capacitances 3a and 3a.
b and 3c move on the circle diagram 8. Ground fault resistance 4
Is present only on the distribution line 2a, since the vector of the ground voltage vn is only on the circle diagram having the diameter of ea, it can be seen that there is a one-line ground fault.

Next, based on the voltages va, vb, vc, the operation is performed by the operational amplifiers 6a, 6b, 6c according to the following equation. v1 = va + vb / 2, v2 = vb + vc / 2, v3 = v
c + va / 2 FIG. 14 shows vectors of the output voltages v1, v2, and v3. However, in FIG. 14, to simplify the drawing, v
1, v2, and v3 are distribution line voltages Vaa, Vbb, and Vcc.
Are shown without partial pressure. When a ground fault occurs, the ground voltage of the distribution line 2a, which is the voltage Vaa across the resistor 4 having the resistance value Rg, becomes smaller than the ground voltages of the other distribution lines. Therefore, the voltage va corresponding to the voltage becomes the minimum value, the voltage v1 becomes the minimum value, and the relation of | v1 | <| v2 | or | v1 | <| v3 | is established.
The phase a is determined to be the accident phase.

[0008]

Since the conventional ground fault detection circuit is constructed as described above, for example,
When there is a ground fault 4 and a second ground fault occurs, the first
In some cases, the magnitude relationship between the voltage vectors v1 and v2 due to the second ground fault changes depending on the resistance value of each ground fault, and it may be difficult to determine whether the second ground fault is a two-line ground fault.

Originally, in an ungrounded three-phase AC line, an electric shock is not caused only by a ground fault of one line, but there is a further problem that a ground fault through a human body on the second line may cause an electric shock. Was. Therefore, in the case of a one-line ground fault in the AC line, it is necessary to continue the power supply to the AC line only by issuing an alarm and to cut off the power supply to the AC line only after a two-line ground fault occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a first ground fault occurs on a first line of a three-phase AC line, and a second ground fault occurs on a three-phase AC line. It is an object of the present invention to obtain a ground fault detection circuit which can easily determine whether or not this is a two-line ground fault. It is another object of the present invention to provide a ground fault detection circuit that can determine which branch line in a multi-branched three-phase AC line has a ground fault. Further, in an ungrounded three-phase four-wire AC line or a single-phase three-wire AC line, a ground fault detection circuit capable of determining a two-wire ground fault even when the first ground fault occurs in a neutral wire is provided. Aim. Another object of the present invention is to provide a ground fault detection circuit capable of canceling the determination of a ground fault when a ground fault occurs momentarily and is recovered immediately thereafter.

[0011]

A ground fault detecting circuit according to a first aspect of the present invention specifies a ground fault phase based on a zero-sequence voltage vector of an ungrounded AC circuit and outputs a ground fault phase discrimination signal. and the earth絡相discriminating circuit which is identified based on the earth絡相discrimination signal
Grounded phase with predetermined ground impedance
Ground circuit and the AC circuit
The zero-phase current sensor provided on the load side and this zero-phase current sensor
The power supply frequency component signal level of the zero-phase current detected by the
And a power signal level determination circuit for detecting the presence or absence of two-wire grounding .

In a ground fault detecting circuit according to a second aspect of the present invention, in the first aspect of the present invention, the AC power path has a branch line, and the injection frequency signal different from the power supply frequency.
And the injection frequency signal is passed
Grounded injection impedance to block AC circuit frequency
And dance, the signal level of the injection frequency component signal of the zero-phase current output from the zero-phase current sensor provided for each branch line is that there is a ground fault in the branch line when it branched grounding judgment signal level higher And an injection signal level determination circuit for determination.

According to a third aspect of the present invention, in the ground fault detecting circuit according to the second aspect of the present invention, the signal level of the injection frequency component signal is equal to or higher than a second ground fault determining signal level which is larger than the branch ground fault determining signal level. And a second AND circuit for determining whether there is a second ground fault, and an AND circuit for performing an AND operation on an output of the injection signal level increase determination circuit and an output of the power supply signal level determination circuit. It is provided.

According to a fourth aspect of the present invention, there is provided a ground fault detection circuit based on a zero-phase voltage vector of each phase of an ungrounded three-phase four-wire or single-phase three-wire AC circuit having a neutral line. and the earth絡相discrimination circuit for outputting the identified locations絡相discrimination signal, earth絡相based on the determination signal identified the land絡相a predetermined ground Inpi
A grounding circuit that connects to the ground by dancing
A zero-phase current sensor provided on the load side of the dancing, and the injection signal source for injecting a different injection frequency signal and its power supply frequency three-wire AC circuit 3-phase 4-wire or single-phase, injection frequency signal
Signal is grounded to pass and block AC circuit frequency
Detect injection frequency current through injection impedance
Input signal current sensor and the injection signal current sensor.
When the injection frequency component signal level is equal to or higher than the predetermined injection frequency ground fault determination signal level, it is determined that there is a ground fault in the three-phase four-wire or single-phase three-wire AC circuit, and an injection frequency ground fault determination signal is output. a signal level determination circuit, it is determined that grounded neutral when the earth絡相discrimination signal without and there injection frequency ground fault determination signal, three-phase 4-wire or single-phase three-wire AC detected by the zero-phase current sensor A power supply signal level determination circuit for determining two-wire ground when the power supply frequency component signal level of the zero-phase current of the electric circuit is equal to or higher than a predetermined level .

According to a fifth aspect of the present invention, in the ground fault detecting circuit according to the fourth aspect, the signal level of the injection frequency component signal is higher than the level of the injection frequency ground fault determination signal. An injection signal level increase determination circuit for determining that there is a second ground fault when the above is present; and an AND circuit for performing an AND operation between an output of the injection signal level increase determination circuit and an output of the power supply signal level determination circuit. Is provided.

According to a sixth aspect of the present invention, there is provided a ground fault detecting circuit according to any one of the first to fifth aspects, further comprising a ground control circuit for intermittently disconnecting the ground by the ground circuit. .

According to a seventh aspect of the present invention, there is provided a circuit breaker including the ground fault detecting circuit, comprising the ground fault detecting circuit according to any one of the first to sixth aspects of the present invention. The main opening / closing contact is opened when the circuit determines that there is a two-wire ground fault.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 of the Invention 1 to 3 show a first embodiment of the present invention. FIG. 1 is a configuration diagram of a ground fault detection circuit. FIG. 2 is an equivalent circuit diagram when a ground fault occurs. FIG. 3 is a vector diagram of the zero-sequence voltage. In FIG. 1, reference numeral 20 denotes an AC power supply, which is composed of a three-phase transformer for distribution of a commercial power supply, and each of Va, Vb, and Vc has a phase of 120.
For example, an AC power supply having a voltage of 230 V and a frequency of 60 Hz which is shifted by degrees. Reference numeral 21 denotes a three-phase AC line which is an AC line.
211, 212, and 213 are distribution lines of each phase of the three-phase AC line 21.

Reference numeral 22 denotes a ground fault phase discriminating circuit, which converts the voltage of each distribution line of the three-phase AC line 21 into capacitors 23, 24 and 25 having a large impedance and a capacitor 26 (for example, a reactance corresponding to each capacitor is about 100 KΩ). ) And a zero-phase voltage vector monitoring circuit 27, and the zero-phase voltage vector vp given by the voltage across the capacitor 26 by the zero-phase voltage vector monitoring circuit 27.
To determine the ground fault phase based on the vector diagram shown in FIG. 3, and outputs a ground signal b for instructing the ground circuit 28 to be described later to ground the ground fault phase.

That is, assuming that a ground fault of the resistor 51 having the resistance value Rg1 occurs in the distribution line 211 of the three-phase AC line 21,
When the relationship between the zero-phase voltage vp appearing at both ends of the capacitor 26 and the voltages Va, Vb, and Vc of the three-phase AC power supply is drawn, as shown in FIG. You can see that there is. The zero-sequence voltage vector monitoring circuit 27 determines a ground fault phase by judging which end of the vector of the zero-sequence voltage vp is on a circle diagram having diameters of Va, Vb, and Vc.

Reference numeral c denotes an alarm signal for instructing a built-in alarm (not shown) to emit a warning sound when the zero-phase voltage vector monitoring circuit 27 determines a ground fault. This informs the occurrence of a ground fault and encourages recovery from the accident.

Reference numeral 28 denotes a ground circuit, which switches the ground fault phase based on the ground signal b to the switches 30 and 3 of the switching circuit 29.
Capacitors 33, 3 which are ground impedances by 1 and 32
It is to be grounded via 4 or 35. The capacitance 33 has a capacitance value of, for example, 5 μF (reactance 530Ω).

Numeral 40 denotes a zero-phase current sensor which is provided on the load side with respect to the capacitance 33, 34 or 35 which is a ground impedance, and detects a zero-phase current of the three-phase AC line 21. Reference numeral 41 denotes a power supply signal level determination circuit for determining a two-wire ground fault based on the signal level of the power supply frequency component signal of the output signal d of the zero-phase current sensor 40. 37, 3
Reference numerals 8 and 39 denote ground capacities of the three-phase AC lines having capacitance values Cg1 to Cg3, respectively.

The ground fault phase determining circuit 22 and the power signal level determining circuit 41 are the ground fault detecting circuit in the present invention. The power signal level determination circuit 41, the ground circuit 28, and the zero-phase current sensor 40 are built in the circuit breaker 42. However, these may be provided separately from the circuit breaker 42.

Next, the operation of the ground fault detection circuit will be described. FIG.
Is an equivalent circuit when a ground fault occurs in the circuit of FIG.
When the first ground fault of the resistor 51 having the resistance value Rg1 occurs in the distribution line 211, the ground fault phase discrimination circuit 22 outputs a ground fault phase discrimination signal b indicating the discrimination of the ground fault phase 211, based on this signal. The ground phase 211 is grounded by the ground circuit 28 via the capacitor 33 having a predetermined ground impedance.

Here, the distribution line 211, which is a ground fault phase, has a capacity of 3
Grounding via 3 is because the impedance of the capacitors 23 to 26 of the voltage divider 22 shown in FIG. 1 is set large, so that the current flowing through the zero-phase current sensor 40 due to the second ground resistor 53 is small. The current flowing through the voltage divider 22 shown in FIG. 1 may decrease when the resistance 53 of the first ground fault is added to the resistance 53 of the second ground fault, and the resistance value Rg1 of the resistance 51 may be reduced. This is because it is difficult to make a distinction from the case of the increase, and it is difficult for the power supply signal level determination circuit 41 to determine a two-line ground fault. Therefore, the grounding phase is grounded via the capacitance 33 (for example, reactance 530Ω), and the current caused by the second grounding resistance 53 is reliably passed through the zero-phase current sensor 40, thereby enabling the determination of the two-wire grounding. Things.

When the second ground fault resistor 53 is generated, the current from Va of the power supply 20 passes through the distribution line 211 and has a capacity of 3
3. ground, second ground fault resistance 53, zero-phase current sensor 4
0, the distribution line 213, and Vc of the power supply 20, and the signal d is output to the zero-phase current sensor 40. The power supply frequency signal level of the signal d is determined by the power supply frequency signal level determination circuit 41.
Determined by If the signal level of the power supply frequency component signal of the signal d is a predetermined value, for example, if the signal level is a resistance of 30 kΩ or less, the line voltage between the distribution lines is 400 V and the current is 13 mA or more. If there is, the power supply signal level determination circuit 41 determines that there is a two-line ground fault. 2
When a line-to-ground fault is determined, a signal e for commanding the opening of the circuit breaker 42 is transmitted.

In the first embodiment of the present invention, the case where the AC line is a three-phase AC line has been described. However, this is a single-phase three-line AC line having a neutral line or a three-phase four-line AC line. Alternatively, when a first ground fault is detected in a distribution line other than the neutral line of these AC lines, the ground fault phase is grounded and the power signal level determination circuit 41 determines a two-wire ground fault. be able to. When a plurality of branch three-phase AC lines (not shown) are provided on the three-phase AC line 21,
By providing a zero-phase current sensor, a power signal level determination circuit, and a circuit breaker for a three-phase AC line for each branch three-phase AC line, it is possible to determine which branch three-phase AC line has a two-wire ground fault. , Only the branch three-phase AC line can be cut off.

Embodiment 2 of the Invention FIG. 4 is a configuration diagram of a ground fault detection circuit according to Embodiment 2 of the present invention. 21d is a three-phase AC line having branched three-phase AC lines 21da and 21db. Reference numeral 62 denotes an injection signal power supply, for example, a voltage of 10
V, an AC signal having an injection frequency of 100 Hz is applied to a three-phase AC line 2
1d. Reference numeral 61 denotes an injection impedance, which is a filter that passes an AC signal having an injection frequency of, for example, 100 Hz and blocks a signal having a commercial power frequency of 60 Hz.

Numerals 63 and 65 denote injection signal level judgment circuits, which are signals of injection frequency component signals which are equal to or higher than the branch ground fault judgment signal level which is the signal level of the ground fault occurrence of the injection frequency component signals of the zero-phase current sensors 40 and 44. The presence or absence of a ground fault is determined based on the level. i and j are alarm outputs of the occurrence of ground fault from the injection signal level determination circuits 63 and 65, respectively.

The injection signal level determination circuits 63 and 65 are the ground fault detection circuit of the present invention. Injection signal level determination circuit 6
3, 65, the power signal level determination circuits 64 and 66, and the zero-phase current sensor 40 are built in the circuit breaker 42 or 46. However, these may be provided separately from the circuit breakers 42 or 46.

Next, the operation of this circuit will be described. When a ground fault 51 having a resistance value Rg1 occurs in the distribution line 211da of FIG. 4 in the branched three-phase AC line 21da branched from the three-phase AC line 21d, the current due to the injection signal injected by the injection signal power supply 62 is generated. Flows through the ground fault resistor 51,
This is detected by the zero-phase current sensor 40. At this time, the current of the power supply frequency component signal is blocked by the injection impedance 61 and does not flow. The injection signal level determination circuit 63 determines the signal level of the injection frequency component signal of the zero-phase current sensor 40, and determines that there is a ground fault if the signal level is equal to or higher than a branch ground fault determination signal level which is a predetermined signal level of occurrence of a ground fault. Output i
Put out. On the other hand, if there is no ground fault in the other branch three-phase AC line 21db, the zero-phase current sensor 44 cannot obtain the signal level of the injection frequency component signal equal to or higher than the branch ground fault determination signal level, and does not output the alarm output j. . In this way, the branch three-phase AC line in which the ground fault has occurred can be specified.

Embodiment 3 of the Invention FIG. 5 is a configuration diagram of a ground fault detection circuit according to Embodiment 3 of the present invention. Even if a surge occurs in the AC line 21d having the branch line of FIG. 4, a two-line ground fault can be determined without making an erroneous determination, and one of the branch lines 21da of the AC line 21d having the branch line can be determined. It shows a part. As shown in FIG. 5, the capacitances 37, 38, and 39 that are the ground capacitances shown in FIG. 4 are the capacitances 37a, 38a, and 39a that are the ground capacitances on the three-phase AC power supply 20 side from the zero-phase current sensor 40 and the zero-phase current. Capacities 37b and 38, which are ground capacities on the load side of the sensor 40
b, 39b. These ground capacitance values are approximately 1 μF per 1 km of the line 21 or 21 da. 40, 42, 63 to 64, 211 da
213da are the same as those shown in FIG.

Numeral 63a denotes an injection signal level increase judgment circuit which is connected to the output d of the zero-phase current sensor 40 and which determines the signal level of the zero-phase current injection frequency component signal of the zero-phase current sensor 40 by a branch ground fault judgment signal. When the signal level is equal to or higher than the second ground fault determination signal level higher than the
And outputs a logical output k1. Reference numeral 71 denotes an AND circuit, which is a logical output k1 of the injection signal level increase determination circuit 63a and the power supply signal level determination circuit 6
When there is a logical output s of 4, a logical output which is a control signal r for instructing the opening of the circuit breaker 42 is output.

In FIG. 5, the injection signal level determination circuit 63
And the case where the injection signal level increase determination circuit 63a is provided separately, it is also possible to share the same device.

The injection signal level increase determination circuit 63a, the power supply signal level determination circuit 64, and the AND circuit 71 are the ground fault detection circuit in the present invention. Injection signal level increase determination circuit 63a, power supply signal level determination circuit 64, AND circuit 7
1. The zero-phase current sensor 40 is built in the circuit breaker 42. However, these may be provided separately from the circuit breaker 42.

Next, the operation of this circuit will be described. 4 and 5, it is assumed that a surge occurs between the distribution lines 211d and 212d due to, for example, switching of an L load. The surge current J1 flowing through the distribution line 211d flows through the zero-phase current sensor 40 and the ground capacitance 37b, flows through the capacitance 38b via the ground, and flows through the surge current J2 flowing through the zero-phase current sensor 40 and the capacitance 38a via the ground. It shunts to flowing surge current J3. Therefore, the zero-phase current sensor 40 detects J1-J2 based on the unbalanced surge current between the distribution lines 211d and 212d.

In many cases, the surge is synchronized with the power supply frequency and may be detected as a power supply frequency component. Therefore, although the determination is made by the power supply signal level determination circuit 64, the determination is not made by the injection signal level increase determination circuit 63a. First
Since the zero-phase current sensor 40 already has an injection frequency component signal having a signal level equal to or higher than the branch ground fault determination signal level due to the occurrence of the ground fault, the injection signal level increase determination circuit 63
In a, when the signal level of the injection frequency component signal of the zero-phase current of the zero-phase current sensor 40 is equal to or higher than a second ground fault determination signal level which is larger than the branch ground fault determination signal level, it is determined that there is a second ground fault. I do.

For example, if the resistance of the ground fault resistor to be detected is 3
If the injection frequency is set to 0 kΩ or less, the injection frequency is set to 100 Hz, and the voltage of the injection signal power supply 62 is set to 10 V.
An injection frequency component signal having a branch ground fault determination signal level of 3 mA is obtained. Therefore, the value of the branch ground fault determination signal level of the injection frequency component signal can be set to the current of 0.33 mA. When a second ground fault with a resistance of 30 kΩ occurs, there is a further 0.33 mA increase in current. Therefore, the second ground fault can be determined by setting the second ground fault determination signal level to 0.5 mA.

In the power supply signal level determination circuit 64, as shown in the first embodiment of the present invention, the first ground-fault phase is set to a value of 5 μF, for example, at a power supply frequency of 60 Hz.
When grounded through a ground impedance of a reactance of 30Ω, when a second ground fault occurs in a phase different from the ground fault phase, if the resistance value of this ground fault is 30 kΩ, the line voltage is 400 V and the current of 13 mA Is obtained. If this is set as a predetermined level, if there is a signal level of the power supply frequency component signal which is equal to or higher than the predetermined level, the second ground fault is set to 2
It can be determined that there is a line ground fault.

Therefore, the injection signal level increase judgment circuit 63a
The logical output k1 of the power supply signal level determination circuit 64 and the logical output s of the power supply signal level determination circuit 64 are input to a logical product circuit 71 to obtain a logical product, so that the injection signal level increase determination circuit 63a determines that there is a second ground fault. The signal level determination circuit 64
If it is determined that there is a line ground fault, an erroneous two-wire ground fault determination due to a surge current can be prevented. When the AND circuit 71 determines that there is a two-line ground fault, a control signal r for instructing the circuit breaker 42 to open is transmitted.

Embodiment 4 of the Invention FIG. 6 is a configuration diagram of a ground fault detection circuit according to Embodiment 4 of the present invention. In the figure,
Reference numeral 48 denotes a single-phase three-wire AC power supply, which is a non-grounded single-phase three-wire AC transformer having a neutral wire for distribution of commercial power. 81 is a single-phase three-wire AC line, 811, 812, 81
Reference numeral 3 denotes a distribution line of a single-phase three-wire AC line 81, of which distribution lines 811 and 813 are voltage lines and distribution line 812 is a neutral line (hereinafter, distribution line 812, which is a neutral line, is simply referred to as neutral line 812). Shown).

Reference numeral 62 denotes an injection signal power supply for injecting an injection frequency component signal into an ungrounded three-phase four-wire or single-phase three-wire AC line having a neutral line. Reference numeral 67 denotes an injection signal for detecting the current of the injection frequency component signal. A current sensor 68 is an injection signal level determination circuit which determines the signal level of the injection frequency component signal of the current detected by the injection signal current sensor 67. When the signal level is equal to or higher than a predetermined injection frequency ground fault determination signal level, the signal is neutral. It determines that there is a ground fault in an ungrounded three-phase four-wire or single-phase three-wire AC line having a line, and outputs an injection frequency ground fault determination signal k. 52 is a neutral wire 8 of a single-phase three-wire AC transformer 48
12 is the ground fault resistance of the resistance value Rg2.

Reference numeral 40 denotes a zero-phase current sensor. b is a ground fault phase discrimination signal which is output to a grounding circuit 70 described later when the ground fault phase discrimination circuit 22 discriminates the ground fault phase. k is an injection frequency ground fault determination signal and is output to a grounding circuit 70 described later when the injection signal level determination circuit 68 determines a ground fault.

Reference numeral 69 denotes a neutral ground fault determination circuit which receives the ground fault phase determination signal b and the injection frequency ground fault determination signal k as input and has no ground fault phase determination signal b and the injection frequency ground fault determination signal k If there is, a neutral ground fault is determined. Reference numeral 70 denotes a grounding circuit having a built-in neutral ground fault determining circuit 69. When the neutral ground fault detecting circuit 69 determines that the ground fault of the neutral wire 812 occurs, the neutral wire 812 is grounded by the ground impedance 32. It is to be grounded. Other configurations are the same as those in FIG.

The ground fault phase determining circuit 22, the injection signal level determining circuit 68 and the power signal level determining circuit 64 are the ground fault detecting circuit according to the fourth embodiment of the present invention. Injection signal level determination circuit 68, power supply signal level determination circuit 64, ground fault phase determination circuit 22, ground circuit 28, zero-phase current sensor 40,
The injection signal current sensor 67 is built in the circuit breaker 42. However, these may be provided separately from the circuit breaker 42.

Next, the operation will be described. In FIG. 6, when a ground fault resistor 52, which is a first ground fault, is generated in the neutral line 812, the injection signal power supply 62 outputs, for example, an injection frequency of 10%.
Since the current due to the 0 Hz injection frequency signal flows through the neutral line 812, the ground fault resistor 52, and the ground, the signal level of the injection frequency component signal of the current of the injection signal current sensor 67 is determined by the injection signal level determination circuit 68. When the signal level of the injection frequency component signal is equal to or higher than the injection frequency ground fault determination signal level which is the ground fault occurrence signal level, it is determined that there is a ground fault. Set the resistance value Rg2 of the resistor 52 of the ground fault to be detected to 30 k
If the voltage of the injection signal power supply 62 is 10 V or less, the value of the predetermined injection frequency ground fault determination signal level is 0.33 of the current.
mA.

When the injection signal level determination circuit 68 determines that there is a ground fault, the injection frequency ground fault determination signal k is supplied to the ground circuit 7.
Output to 0. In the case of a neutral ground fault, when the injection frequency ground fault determination signal k is issued, the ground fault phase determination circuit 22 does not determine the ground fault due to the zero-phase voltage vp and does not output the ground fault phase determination signal b. In the neutral line ground fault determination circuit 69 built in the grounding circuit 70, when there is no ground fault phase determination signal b and there is an injection frequency ground fault determination signal k, the neutral line 812
And the switch 31 of the switching circuit 29 is closed in the ground circuit 70, and the neutral line 81 of the single-phase three-wire AC line is
2 is grounded.

In this way, the first ground fault resistance 52
Is generated in the neutral line 812, and the resistance 51
Is generated in the distribution line 811 other than the neutral line 812, for example, the ground fault current is supplied from the AC power supply 48 to the distribution line 811, the zero-phase current sensor 40, the ground fault resistance 51, the ground, the capacity 34,
Flow through the circuit via the neutral line 812, and the zero-phase current sensor 4
0 detects a zero-phase current and outputs a signal d. The power signal level determination circuit 64 determines that there is a two-wire ground fault when the signal level of the power frequency component signal of the signal d is equal to or higher than a predetermined value. The predetermined value can be set to, for example, 13 mA in the same manner as described in the first embodiment of the invention. When it is determined that there is a two-line ground fault, the circuit breaker 4
A signal s for instructing the opening of No. 2 is transmitted. As described above, even when the ground fault resistance 52 occurs in the neutral line 812, a two-wire ground fault can be determined.

The single-phase three-wire AC power supply 48 shown in FIG. 6 may be a three-phase four-wire AC power supply having a neutral wire, and a two-wire ground fault when a ground fault resistance occurs in the neutral wire. Is also single phase 3
This can be performed in the same manner as in the case of the line AC power supply 48.

In the fourth embodiment, the neutral ground fault detection circuit 69 is incorporated in the grounding circuit 70.
This may be provided independently, or may be provided integrally with the zero-phase voltage vector monitoring circuit 27.

Embodiment 5 of the Invention FIG. 7 is a configuration diagram of a ground fault detection circuit according to Embodiment 5 of the present invention. Even if a surge occurs in an ungrounded three-phase four-wire or single-phase three-wire AC line having a neutral line in FIG. 6, a two-wire ground fault can be determined without making an erroneous determination. Similarly to those shown in FIG. 5, the capacitances 37, 38, and 39, which are ground capacitances, have a ground capacitance of about 1 μF per 1 km of the line 81.

An injection signal level increase determination circuit 63b is connected to the output d2 of the injection signal current sensor 67.
When the signal level of the injection frequency component signal is equal to or higher than a third ground fault determination signal level larger than the injection frequency ground fault determination signal level, it is determined that there is a second ground fault, and a logical output k2 is output. . A logical product circuit 71b outputs a logical output t when there is a logical output k2 of the injection signal level increase determining circuit 63b and a logical output s of the power signal level determining circuit 64. In FIG. 7, the injection signal level determination circuit 68 and the injection signal level increase determination circuit 63
Although the case where a is provided separately is shown, it is also possible to share a single device.

The injection signal level increase judging circuit 63b, the power signal level judging circuit 64, and the AND circuit 71b are the ground fault detecting circuit in the present invention. The injection signal level increase determination circuit 63b, the power supply signal level determination circuit 64, the AND circuit 71b, the ground fault phase determination circuit 22, the grounding circuit 70, the zero-phase current sensor 40, and the injection signal current sensor 67 include a circuit breaker 42.
It is built in. However, these may be provided separately from the circuit breaker 42.

Next, the operation of this circuit will be described. In FIG. 7, when a surge occurs in an ungrounded three-phase four-wire or single-phase three-wire AC line having a neutral line, the power signal level determination circuit 64 detects the surge as a power frequency component signal. This is the same reason as described in the third embodiment. However, since the power supply frequency component signal is set not to flow in the injection signal level increase determination circuit 63a, the power supply frequency component signal is not detected.

When the first ground fault occurs, since the injection signal current sensor 67 has an injection frequency component signal having a signal level higher than the injection frequency ground fault determination signal level, the injection signal level increase determination circuit 63b outputs the injection frequency component signal. When the signal level is equal to or higher than a third ground fault occurrence signal level larger than the injection frequency ground fault determination signal level, it is determined that a second ground fault is present.

The injection frequency ground fault determination signal level in the fifth embodiment of the invention can be set in the same manner as the branch ground fault determination signal level in the third embodiment of the invention, and is substantially the same. The third ground fault determination signal level of the fifth embodiment of the present invention is different from the second ground fault determination signal level of the third embodiment of the present invention in that a current 31.4 mA flowing through the ground impedance 31 is added. It is necessary to consider the increase. Here, the ground impedance is a capacitance of 5 μF, the frequency of the injection frequency signal is 100 Hz, and the voltage is 1
0 V was applied. Further, if the current flowing through the ground impedance is detected by another current sensor and the difference from the injection signal current sensor 67 is obtained, the same setting as in the third embodiment of the present invention can be made.

Therefore, the injection signal level increase determination circuit 63b
The logical output k2 and the logical output s of the power supply signal level determination circuit 64 are input to a logical product circuit 71b to obtain a logical product, so that the injection signal level increase determination circuit 63a determines that there is a ground fault. The determination circuit 64 determines that there is a two-wire ground fault, and can make a two-wire ground fault determination without making an erroneous determination due to a surge current. When the AND circuit 71b determines that there is a two-line ground fault, a control signal t for instructing the circuit breaker 42 to open is transmitted.

Embodiment 6 of the Invention FIG. 8 is a configuration diagram showing a main part of a ground fault detection circuit according to Embodiment 5 of the present invention. 7
Reference numeral 2 denotes a ground control circuit which intermittently outputs a ground fault phase discrimination signal b or an injection frequency ground fault discrimination signal k (hereinafter, described as a ground fault phase discrimination signal b in the sixth embodiment of the present invention) every second. The grounding of the ground fault phase is reset by disconnection. In FIG. 8, 211 to 213, 27 and 28, and capacitors 23, 24, 25 and 26 are the same as those in FIG.

Next, the operation of the ground control circuit 72 will be described. In FIG. 1, after the ground fault phase discrimination circuit 22 determines the ground fault phase 211 caused by the first ground fault 51 shown in FIG. 2, the ground control circuit 72 outputs the ground fault phase generated from the zero-phase voltage vector monitoring circuit 27. The determination signal b is interrupted at a time interval of, for example, one second or several minutes, the grounding of the distribution line first determined to be the ground fault phase is temporarily removed, and the determination of the ground fault phase is repeated again for instantaneous. If a ground fault occurs and the ground fault recovers shortly thereafter, the first determination can be canceled.

For example, as shown in FIGS. 1 and 2, the ground fault phase determining circuit 22 first determines the ground fault 51 on the distribution line 211, and switches the switch 30 of the ground circuit 28 based on the ground fault phase determining signal b. When the distribution line 211 is grounded via the capacitor 33 by turning on, the switch 30 is intermittently turned off by the grounding control circuit 72 in FIG. 8 and the zero-phase voltage vector is monitored again, and the ground fault 51 is recovered. When the determination is made, the first determination can be canceled by keeping the switch 30 OFF.

Embodiment 7 of the Invention Embodiment 1 of the invention
5-19 instead of the ground fault phase determination circuit 22
The use of the ground fault phase discriminating circuit described in Japanese Patent Application Publication No. 407 can reduce the influence of the detection time and noise and improve the sensitivity of detecting the ground fault phase even when both the ground capacitance and the ground fault resistance are large. . Hereinafter, one embodiment of the ground fault phase detection circuit will be described with reference to FIG.

Reference numeral 109 denotes distribution lines 102a, 102b, 10
2c, windings 109a, distribution lines 102a, 10
A winding 109 that generates reference voltages ua, ub, uc delayed from the voltages ea, eb, ec of 2b, 102c by an angle α.
b and the reference voltages ua ′, ub ′, uc ′ which are orthogonal to the reference voltages ua, ub, uc, that is, are 90 ° more advanced than these.
And a transformer 110 also having a phase shifter function. The transformer 110 has distribution lines 102a, 102b, 102
c, which is a capacitive transformer that detects the zero-sequence voltage vo and functions as a voltage divider and a zero-sequence voltage vo detector.

Reference numerals 111a, 111b, and 111c denote multipliers for multiplying the zero-phase voltage vo and reference voltages ua, ub, and uc, and reference numeral 112 denotes a differentiator for the zero-phase voltage vo to obtain a differential voltage. , And 114a, 114b, and 114c are multipliers for multiplying the differential voltage vo 'by the reference voltages ua', ub ', and uc'.

115a, 115b and 115c are multipliers 1
Voltages wa1, wb1, w of 11a, 111b, 111c
c1 and the voltage wa of the multipliers 114a, 114b, 114c
Adder for adding 2, wb2, wc2, 116a, 1
16b and 116c are adders 115a, 115b and 115
c, the voltages wa, wb, wc are integrated, and the voltages Wa, Wb,
Integrators 117a, 117b and 117c for obtaining Wc are comparators for comparing the voltages Wa, Wb and Wc with the threshold value -Wth.

Reference numeral 118 denotes adders 115a, 115b and 11
A selector 119 selects the minimum value, that is, the one in the accident occurrence phase, from the voltages wa, wb, wc of 5c.
8, the voltage wa, wb, or wc and the threshold value -V
comparators 120a, 120b, 120 for comparing with th.
c is an AND gate for ANDing the outputs of the comparators 117a, 117b and 117c and the output of the comparator 119, and outputs signals Fa, Fb and Fc indicating the detection of a ground fault.

Next, the operation will be described. Power supply 101
The voltages ea, eb, ec of a, 101b, 101c are represented by the following equation (1).

[0068]

(Equation 1)

Reference voltage ua, ub, u of transformer 109
c, ua ', ub', uc 'are obtained from the following equation (2) and (3) from the equation (1).

[0070]

(Equation 2)

Reference voltages ua, ub, uc, ua ', u
Since b 'and uc' are related to the line voltage, the ground fault such as the fault point 104 does not change. However, due to such a ground fault, the potential at the neutral point 0 changes, and a zero-phase voltage vo is generated.

The zero-phase voltage vo is equal to the ground capacitance 3a, 3b,
3c, a capacitance Co, a ground fault resistance Rg, and a resistance value R of the resistor 107.
N and the following equations (4), (5), and (6). vo (t) = − vosin (ωt−θ) (4) where

[0073]

(Equation 3)

FIG. 10 is a vector diagram showing a vector relationship among the voltages ea, eb, ec, the reference voltages ua, ub, uc, ua ', ub', uc 'and the zero-phase voltage vo. As shown, the zero-phase voltage vo is determined by the value of the ground fault resistance Rg.
Comes anywhere on the circle diagram 8.

The voltages wa1, wb1, wc1 of the multipliers 111a, 111b, 111c are expressed by the following equation (7).

[0076]

(Equation 4)

The first term of the equation (7) is a DC component,
And E, and the second term is an AC component of 2ω.

When the zero-phase voltage vo is differentiated by the differentiator 112, a differential voltage vo 'as shown in the following equation is generated from the equation (4). vo ′ (t) = − vocos (ωt−θ) (8) Therefore, the voltage w of the multipliers 114a, 114b, 114c
a2, wb2, wc2 are represented by the following equation (9).

[0079]

(Equation 5)

Since the second term on the right side of equation (9) has the opposite sign to the second term on the right side of equation (7), adders 15a, 15b, and 15c are used.
Deletes the AC component by adding the two. That is

[0081]

(Equation 6)

The selector 118 selects the minimum one from the DC signals wa1, wa2, wa3 related to the ground fault obtained in (10).
The accident phase is discriminated by selecting by.

The voltages wa, wb, wc are determined by the integrators 116a,
Integrated by 116b and 116c, the following equation (11) is obtained.

[0084]

(Equation 7)

The voltages Wa, Wb, W represented by the equations (11)
Since c is related to the zero-phase voltage vo, it is zero when there is no ground fault and the voltages ea, eb, and ec of each phase are balanced.

However, when a zero-phase voltage vo is generated due to a ground fault, the voltages Wa, Wb, and Wc increase with time.
In this case, the voltage Wa indicates a negative value, and the voltages Wb and Wc indicate a positive value. Thereby, even when both the ground fault resistance and the capacitance of the distribution line are large and the potential difference of the distribution line is small, it is possible to determine the ground fault phase.

FIG. 11 shows waveforms of voltages Wa, Wb, and Wc when a ground fault occurs at time tg. Thus, only the voltage Wa of the fault phase increases in the negative direction, and the other voltages Wb and Wc increase in the positive direction. Since the voltage Wa intersects the threshold value -Wth at the time td, this is detected by the comparator 117a, and its output becomes 1. Thus, the comparator 11
Since the comparison with the threshold value -Wth is performed using 7a, 117b, and 117c, it is possible to determine a ground fault large enough to cause a ground fault current of a predetermined value or more to flow within a predetermined time.

The voltage wa output from the comparator 115a is
The data is input to the comparator 119 via the selector 118, and the threshold value −
Vth, and as shown in FIG. 12, immediately crosses the threshold value -Vth at time tg. Thus, it is possible to determine the ground fault of the ground fault current equal to or more than the predetermined value.
Accordingly, the output of the comparator 119 becomes 1, the AND gate 120a is opened, and the signal Fa indicating the a-phase, that is, the ground fault of the distribution line 102a is output. From this, the ground fault can be determined without a large time delay after the occurrence of the ground fault. Distribution line 10
In the case of the ground fault of 2b or 102c, the determination of the ground fault can be performed in the same manner as in the case of the a phase.

[0089]

According to the first aspect of the present invention, the ground fault phase obtained by the ground fault phase determination circuit is grounded, and a two-wire ground fault is generated based on the signal level of the power supply frequency component signal of the zero-phase current. Since the determination is made, when a first ground fault occurs on the first line of the AC line and a second ground fault occurs on the AC line, it is easily determined whether or not this is a two-line ground fault. And a ground fault detection circuit that can perform the operation.

According to the second aspect of the present invention, the injection frequency signal is injected into the three-phase AC line, and based on the injection frequency component signal of the zero-phase current of the zero-phase current sensor provided for each branch line. In order to determine the ground fault, an injection signal level determination circuit is provided.
It is possible to determine which branch line the ground fault has occurred.

According to the third aspect of the invention, the output of the injection signal level increase determination circuit and the output of the power supply signal level determination circuit are input to an AND circuit, and the output is used to determine a two-wire ground fault. Therefore, a ground fault detection circuit that does not make an erroneous determination even when there is a surge current flowing through the ground capacitance can be obtained.

According to the fourth aspect of the present invention, in an ungrounded three-phase four-wire or single-phase three-wire AC line having a neutral line,
If there is no ground-fault phase determination signal and there is an injection frequency ground-fault determination signal, it is determined that a neutral ground fault has occurred, the neutral wire is grounded, and a two-wire ground based on the signal level of the zero-phase current power supply frequency component signal Since a ground fault is determined, a two-wire ground fault can be determined even when the first ground fault occurs in the neutral wire.

According to the fifth aspect of the present invention, the output of the injection signal level increase determination circuit and the output of the power supply signal level determination circuit are input to an AND circuit, and the output is used to determine a two-wire ground fault. Therefore, a ground fault detection circuit that does not make an erroneous determination even when there is a surge current flowing through the ground capacitance can be obtained.

According to the sixth aspect of the present invention, after the ground fault phase is determined, grounding by the ground circuit is intermittently removed and the ground fault phase is determined again, so that a ground fault occurs instantaneously. If the ground fault is recovered immediately thereafter, the determination of the ground fault can be canceled.

According to the seventh aspect of the present invention, since the ground fault detecting circuit according to any one of the first to sixth aspects is provided, the main open / close contact is opened by judging a two-wire ground fault. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a ground fault detection circuit according to a first embodiment of the present invention;

FIG. 2 is an equivalent circuit diagram when a ground fault occurs according to the first embodiment of the present invention.

FIG. 3 is a vector diagram of a zero-sequence voltage according to the first embodiment of the present invention;

FIG. 4 is a configuration diagram of a ground fault detection circuit according to a second embodiment of the present invention;

FIG. 5 is a configuration diagram of a ground fault detection circuit according to a third embodiment of the present invention.

FIG. 6 is a configuration diagram of a ground fault detection circuit according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram of a ground fault detection circuit according to a fifth embodiment of the present invention.

FIG. 8 is a configuration diagram of a ground control circuit of a ground fault detection circuit according to a sixth embodiment of the present invention.

FIG. 9 is a circuit diagram of a ground fault detection circuit according to a seventh embodiment of the present invention.

FIG. 10 is a vector diagram related to the ground fault phase detection circuit of FIG. 9;

11 is an operation waveform diagram of the ground fault phase detection circuit of FIG. 9;

FIG. 12 is an operation waveform diagram of the ground fault phase detection circuit of FIG. 9;

FIG. 13 is a circuit diagram of a conventional ground fault phase detection circuit.

FIG. 14 is a vector diagram relating to a conventional ground fault phase detection circuit.

[Explanation of symbols]

Reference Signs List 20 three-phase AC power supply, 21, 21d three-phase AC line 21da, 21db branch three-phase AC line 211, 212, 213, distribution line 211d, 212d, 213d, distribution line 211da, 212da, 213da distribution line 22 ground fault phase determination circuit 27 Zero-phase voltage vector monitoring circuit, 28, 70 Grounding circuit, 29
Switching circuit, 33 to 35 Ground impedance 40, 44 Zero-phase current sensor 67 Injection signal current sensor 41, 64, 66 Power supply signal level determination circuit, 42, 4
6 circuit breaker, 48 single-phase three-wire AC power supply 62 injection signal power supply, 63, 65, 68 injection signal level determination circuit, 63a, 63b injection signal level increase determination circuit, 71, 71b logical product circuit, 72 ground control circuit, 81 Single-phase three-wire AC line 812 Neutral wire 811, 813 Voltage wire

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 3/34-3/347 H02H 3/16 G01R 31/02

Claims (7)

(57) [Claims] 1. A and earth絡相discrimination circuit for outputting the identified locations絡相discrimination signal based land絡相zero phase voltage vector AC circuit ungrounded systems, the specific is based on the ground絡相discrimination signal
Grounded phase with a predetermined ground impedance.
Connected to the ground circuit, and
A zero-phase current sensor provided on the load side of the road
Level sensor signal level of the zero-phase current detected by the current sensor
And a power supply signal level determination circuit for determining the presence or absence of the two-wire ground by determining a ground level. 2. An AC circuit having a branch line, wherein an AC signal having an injection frequency signal different from a power frequency of the AC circuit is provided.
And the injection frequency signal is passed.
Grounded injection
And when the signal level of the injection frequency component signal of the zero-phase current output from the zero-phase current sensor provided for each of the branch lines is equal to or higher than the branch ground fault determination signal level.
Ground fault detection circuit according to claim 1, characterized in that a and determining injection signal level determination circuit there ground fault in the branch line. 3. An injection signal level increase determination circuit for determining that there is a second ground fault when the signal level of the injection frequency component signal is equal to or higher than a second ground fault determination signal level larger than the branch ground fault determination signal level. 3. The ground fault detection circuit according to claim 2, further comprising: an AND circuit for calculating an AND of an output of the injection signal level increase determination circuit and an output of the power supply signal level determination circuit. 4. A ground fault that specifies a ground fault phase based on a zero-phase voltage vector of each phase of an ungrounded three-phase four-wire or single-phase three-wire AC circuit having a neutral wire and outputs a ground fault phase discrimination signal. phase determination circuit and said specified ground絡相 based on the ground絡相discrimination signal
To ground with a predetermined ground impedance
Circuit and the load side of the AC circuit from the ground impedance
Zero-phase current sensor provided on the injection frequency signals different from the power supply frequency to the 3-phase 4-wire or single-phase three-wire AC circuit
And the injection frequency signal is passed.
Grounded injection
Impedance and the injection frequency through this injection impedance
Injection signal current sensor that detects several currents and this injection signal
When the level of the injection frequency component signal detected by the current sensor is equal to or higher than the predetermined injection frequency ground fault determination signal level,
An injection signal level determination circuit for determining that there is a ground fault in the four-phase or single-phase three-wire AC circuit and outputting an injection frequency ground fault determination signal; and the absence of the ground fault phase determination signal and the injection frequency ground fault determination signal it is determined that grounded neutral when there, the zero-phase
The power frequency component signal level of the zero-phase current of the three-phase four-wire or single-phase three-wire AC circuit detected by the current sensor is a predetermined level
A ground fault detection circuit comprising: a power signal level determination circuit that determines that two wires are grounded in the above case . 5. An injection signal level increase determination for determining that there is a second ground fault when the signal level of the injection frequency determination signal is equal to or higher than a third ground fault determination signal level larger than the injection frequency ground fault determination signal level. 5. A circuit according to claim 4, further comprising a logical product circuit for obtaining a logical product of an output of said injection signal level increase determination circuit and a power supply signal level determination circuit.
Ground fault detection circuit as described. 6. The ground fault detection circuit according to claim 1, further comprising a ground control circuit for intermittently disconnecting the ground by the ground circuit. 7. A circuit breaker, comprising: a ground fault detection circuit according to claim 1; and a main circuit breaker that opens a main switching contact based on a determination that a two-wire ground fault is present by the ground fault detection circuit. .