JP3376644B2 - Ground fault detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault detecting device for detecting a ground fault current flowing in an AC electric circuit.

[0002]

2. Description of the Related Art In this type of ground fault detecting device, there is provided a comparing means for comparing one of the positive side waveform and the negative side waveform with a predetermined value, and the output of the zero-phase current transformer. When the value exceeds a predetermined value, the comparison means compares the values to discriminate the time by the discrimination means to operate the switching element. The output of the zero-phase current transformer is judged to be a ground fault current when the positive-side waveform or the negative-side waveform, which is the output of the zero-phase current transformer, is output twice in order to prevent malfunction due to lightning. Then, the switching element is activated.

[0003]

However, in the above-mentioned ground fault detecting device, the comparing means compares one of the positive-side waveform and the negative-side waveform with the predetermined value and determines the predetermined value. When the positive side waveform or the negative side waveform that exceeds is output twice, it is determined that it is a ground fault current, and the switching element is operated. Therefore, it takes time to determine the ground fault current accurately. There was a problem.

It is also conceivable that both the positive side and the negative side are detected, but in this case, many processing means (the number of parts) may be required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a ground fault detection device capable of operating a switching element in a short time while reducing the processing means (the number of parts). To provide.

[0006]

In order to solve such a problem, the ground fault detecting device according to claim 1 is installed in an AC electric circuit.
A zero-phase current transformer that detects the ground-fault current, a positive-side comparison unit that outputs when the output signal of the zero-phase current transformer exceeds a predetermined value set on the positive side, and the zero-phase current transformer. A negative side comparing means for outputting when the output signal of the sink becomes less than or equal to a predetermined value set on the negative side, and a logical means for logically adding and outputting the outputs of the positive side and negative side comparing means, In the ground fault detection device, the output of the logic means is time-discriminately discriminated to output a signal to activate the switching element.
The stage has a first stage that is constantly charged only at the output of the logic means.
The voltage of the first capacitor is discharged while discharging the capacitor.
Waveform shaper that outputs a signal when is less than a specified value
And the waveform is always discharged only at the output of this waveform shaping means.
The second capacitor is charged and the second capacitor is charged.
Switching element when the voltage of the output voltage exceeds a specified value
To the integration means for outputting the signal to
It

A ground fault detecting device according to a second aspect is the first aspect.
Third third capacitor performs charge and discharge of the capacitor is provided Tokinobe means for outputting as an output of the logic means to the discriminating means when it is above a predetermined value in response to an output of the logic means those described It is as a configuration.

A ground fault detecting device according to a third aspect is the second aspect.
The time delaying means for outputting the one-shot signal when the third capacitor has reached a predetermined value or more, and the waveform shaping means discharges the first capacitor to a substantially zero voltage when the time delaying means outputs. There is.

A ground fault detecting device according to a fourth aspect of the present invention is the third aspect.
The waveform shaping means is configured such that the charging time from the substantially zero voltage of the first capacitor to the predetermined value is set to be a half cycle or more and one cycle or less with respect to the power supply frequency of the AC electric circuit.

A ground fault detecting device according to a fifth aspect of the present invention is the first aspect.
Further, it is configured such that one of the predetermined values of the positive side and negative side comparing means of any one of claims 4 to 4 is set larger than the other.

A ground fault detecting device according to a sixth aspect is the fifth aspect.
The switching element is connected to the switching element via an electromagnet device capable of opening the contacts interposed in the alternating current path and the full-wave rectifying means.

[0012]

According to the structure of the first aspect, when the output of the zero-phase current transformer is output from the positive side waveform, the positive side determining means starts to make a determination, and the output is output from the negative side waveform. In this case, since the negative side discriminating means starts the discrimination, the discrimination can be started from the side where the positive or negative waveform is outputted. In addition, the specified value of the first capacitor
By changing the charging time to achieve
Positive side comparison means and negative side ratio for operating the ching element
The number of outputs of the comparison means can be changed.

According to the structure of claim 2, in addition to the operation of claim 1, the output of the zero-phase current transformer is compared with a predetermined value by the comparing means, and the output of the zero-phase current transformer is equal to or more than the predetermined value. The third capacitor is charged only for the time
When the third capacitor exceeds the charging capacity and the output of the zero-phase current transformer becomes less than the predetermined value, discharging starts.

According to the structure of claim 3 , in addition to the effect of claim 2 , charging can be started immediately from the state in which the first capacitor is discharged.

According to the structure of claim 4 , in addition to the function of claim 3 , the circuit operates when a waveform having the same cycle with respect to the power supply frequency is input, and a waveform having a different cycle with respect to the power supply frequency is generated. It does not work if entered.

According to the configuration of claim 5 , claim 1
In addition to the operation of any one of claims 4 to 4, the ground fault detection level can be set by adjusting one of the positive side detecting means and the negative side detecting means.

According to the structure of claim 6 , in addition to the operation of claim 5 , even if the detection is started from either the positive side or the negative side, if the switching element is driven, power is supplied to the electromagnet device. It

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 is a block diagram showing the configuration of a ground fault detector according to a first embodiment of the present invention, FIG. 2 is a waveform diagram for explaining an operation when a ground fault current is detected from a positive side waveform by a zero-phase current transformer, and FIG. FIG. 4 is an operation explanatory diagram when the ground fault current is detected from the negative side waveform by the zero-phase current transformer, and FIG. 4 is an operation explanatory diagram when the induced lightning is detected.

That is, the ground fault detecting device operates the switching element 2 in response to the output of the zero-phase current transformer 1 for detecting the ground fault current interposed in the AC electric path, and the contact interposed in the electric path. Is for energizing the electromagnet device 3 for forcibly opening the contacts, and is composed of the following members.

Reference numeral 4 is a positive side comparing means for outputting when the output signal of the zero-phase current transformer 1 exceeds a predetermined value (V1) set on the positive side, and 5 is an output signal of the zero-phase current transformer 1. Is a negative side comparison means that outputs when the value becomes equal to or less than the predetermined value (V2) set on the negative side,
6 is a logic means for logically adding the outputs of the positive side comparing means 4 and the negative side comparing means 5 and outputting, and 7 is for charging and discharging the third capacitor C1 in response to the output of the logic means 6 .
The time delay means 7 which outputs when the capacitor C1 of 3 becomes a predetermined value (V3) or more, and the time delay means 7 which is the output of the logic means 6
Of the switching element by time-discriminating the output of
It is a discrimination means for activating 2.

Numeral 9 is a part of the discrimination means 8, which discharges the first capacitor C2 which is always charged only when the logic means 6 outputs and also discharges the first capacitor C2.
Waveform shaping means for voltage and outputs a signal when it is less than a predetermined value (V4), 10 is also a part of what discrimination means 8, the second being always discharged only when the output of the waveform shaping means 9 Switching element when the capacitor C3 is charged and the voltage of the second capacitor C3 exceeds a specified value (V5)
Integrating means for outputting a signal to 2, and 11 are full-wave rectifying means for rapidly energizing the electromagnet device 3 by the output of the discriminating means 8.

The operation of the ground fault detecting device configured as described above will be described with reference to FIGS. 2 and 3 show the case where the ground fault current is detected by the zero-phase current transformer 1 from the positive side waveform and the negative side waveform. When the ground fault current is detected (a) by the zero-phase current transformer 1, when the positive side comparison means 4 and the negative side comparison means 5 exceed the predetermined value (V1) set on the positive side and the negative side. When the voltage becomes lower than the predetermined value (V2) set in, the output signals having the waveforms shown in (b) and (c) are output. This output signal is as shown in (d) by time extending means 7 are ORed by the logical unit 6, the when with charging the third capacitor C1 waveform level of (b) and (c) becomes 0 The capacitor C1 of 3 is discharged. At this time, the voltage is output when the voltage of the third capacitor C1 exceeds a predetermined value (V3).

The output signal of the time delay means 7 causes the waveform shaping means 9 which is a part of the discrimination means 8 to output the first capacitor C2, which is always charged, to the output of the time delay means 7, as shown in (e). although the discharges only time a signal is output, the when the output signal of Tokinobe means 7 no longer outputs
The capacitor C2 of 1 starts charging again. Then, as shown by the broken line (f) by the integration means 10, the waveform shaping means 9
Is output (when the charging voltage of the first capacitor C2 is V4 or less), the second capacitor C3, which is constantly discharged, is charged, and the voltage of the second capacitor C3 is at a predetermined value (V5).
When the above is reached, the signal to the switching element 2 is output. In the case of the present embodiment, the switching element 2 is output.
Because force open the contacts 4 of the electrical path by an electromagnet device 3 when the output signals to, as indicated by a solid line in (f), the
The second capacitor C3 is not charged until the charging voltage of the first capacitor C2 reaches V4.

When the voltage of the second capacitor C3 exceeds a predetermined value (V5), a signal to the switching element 2 is output as shown in (g). The output time of this output signal is the amount of time during which the second capacitor C3 exceeds the predetermined value (V5). This output signal turns on the gate of the thyristor, which is the switching element 2, to operate the switching element 2, thereby rectifying means 11
Current flows in the direction of D1 or D2 → switching element 2 → D3 or D4 to drive the electromagnet device 3 and forcibly open the contact to interrupt the AC circuit. In addition, as shown in FIGS. 2 and 3, the case where the ground fault current is detected by the zero-phase current transformer 1 from the positive side waveform and the case where it is detected from the negative side waveform are as follows.
Only the waveform diagrams of (a) to (C) are different. Further, in the figure, 13 is an operation sensitivity setting means for setting one of the predetermined values (V1 and V2) of the positive side comparing means 4 and the negative side comparing means 5 to be larger than the other (operating sensitivity of the leakage current). is there.

Next, the operation when the ground fault current is detected in the electric line by the induced lightning will be described with reference to FIG. That is, when the ground fault current is detected (a) by the induced lightning, it is set when the positive side comparison means 4 and the negative side comparison means 5 exceed the predetermined value (V1) set on the positive side and the negative side. When the predetermined value (V2) or less is reached, output signals having waveforms as shown in (b) and (c) are output. This output signal is logically ORed by the logic means 6 and the time delay means 7 charges the third capacitor C1 as shown in (d).
When the waveform levels in (b) and (c) become 0, the third capacitor C1 is discharged. At this time, the voltage is output when the voltage of the third capacitor C1 becomes equal to or higher than the predetermined value (V3).

The output signal of the time delay means 7 causes the waveform shaping means 9 which is a part of the discrimination means 8 to output the first capacitor C2 which is always charged to the output of the time delay means 7 as shown in (e). although the discharges only time a signal is output, the when the output signal of Tokinobe means 7 no longer outputs
The capacitor C2 of 1 starts charging again. Then, as shown in (f), the integrating means 10 charges the second capacitor C3 which is constantly discharged only when the waveform shaping means 9 is outputting (when the charging voltage of the first capacitor C2 is V4 or less). At the same time, when the voltage of the second capacitor C3 becomes a predetermined value (V5) or more, the signal to the switching element 2 is output. However, since the voltage of the second capacitor C3 does not become the predetermined value (V5) or more, , No output signal is output to the switch element 2 as shown in (g). This makes it possible to prevent malfunction due to guided lightning.

Next, a second embodiment of the present invention will be described with reference to FIGS.
It will be described based on. This is one in which one-shot means is provided between the time delaying means and the discriminating means of the first embodiment, and the description will be centered below. FIG. 5 is a block diagram showing the configuration of a ground fault detector according to a second embodiment of the present invention, FIG. 6 is a waveform diagram for explaining the operation when the ground fault current is detected from the positive side waveform by the zero-phase current transformer, and FIG. 8 is an operation explanatory diagram when the ground fault current is detected from the negative side waveform by the zero-phase current transformer, FIG.
[Fig. 3] is an operation explanatory diagram when an induced lightning is detected.

That is, by providing the one-shot means 12 between the time delay means 7 and the discrimination means 8, as shown in (f) of FIGS. 6 to 8, a voltage higher than the charging voltage of the third capacitor C1 is applied. It is not necessary to discharge the first capacitor C2 until the output time. That is, only the time (t1) when the output signal (e) of the one-shot means 12 is output
Since it suffices to discharge the first capacitor C2, until the charging voltage of the second capacitor C3 becomes a predetermined value (V5) or more when the ground fault current is detected by the induced lightning as shown in FIG. The charging time (t2) can be set short. This makes it possible to easily prevent a malfunction due to lightning or the like. Also this
Since the charging time from the substantially zero voltage of the first capacitor C2 to the predetermined value (V4) is more than a half cycle and less than one cycle with respect to the power frequency of the AC circuit, it is the same as the power frequency It operates when a waveform with a period is input, and does not operate when a waveform with a different period is input with respect to the power supply frequency. Therefore, more accurate ground fault detection can be performed.

In the first and second embodiments, the magnitudes of the predetermined values (V1, V2) of the positive side comparing means and the negative side comparing means may be set appropriately according to the detection level of each local current. Good. Further, the predetermined value (V3) of the time delay means may be set to a value that does not malfunction due to noise for a short time. Furthermore, the predetermined value (V4) of the first capacitor C2 and the predetermined value (V5) of the second capacitor C3 may be set to values that do not malfunction due to induced lightning.

[0030]

According to the ground fault detection device of the first aspect,
When the output of the zero-phase current transformer is output from the positive side waveform, the positive side determination means starts determination, and when the output is output from the negative side waveform, the negative side determination means starts determination. Therefore, regardless of whether the positive or negative waveform is output, the determination can be started from the output side, so that it is possible to operate the switching element in a short time while reducing the processing means (the number of parts). Especially for the predetermined value of the first capacitor
By changing the charging time to achieve
Positive side comparison means and negative side ratio for operating the ching element
Since the number of outputs of the comparison means can be changed, lightning surges, etc.
This has the effect of making it easier to prevent malfunctions
To do.

According to the ground fault detecting device of the second aspect, the output of the zero-phase current transformer is compared with the predetermined value by the comparing means, and the time for which the output of the zero-phase current transformer becomes the predetermined value or more. only charges the third capacitor, beyond the third capacitor charge capacity by the charging, and the output of the zero-phase current transformer begins to discharge to be less than a predetermined value, to the effect of claim 1, wherein In addition, noise can be removed for a short period of time to easily prevent malfunction.

According to the ground fault sensing device according to claim 3, the
Since charging can be started immediately from the state in which the first capacitor is discharged, in addition to the effect of claim 2 , a long-wave negative side waveform such as lightning is output to prevent malfunction . The charging time of the second capacitor can be set to be short, so that malfunction due to lightning or the like can be easily prevented.

According to the ground fault detecting device of the fourth aspect, the present invention operates when a waveform having the same cycle as the power supply frequency is input, and operates when a waveform having a different cycle as the power supply frequency is input. Does not operate. Therefore, in addition to the effect described in claim 3 , it can be operated only when a ground fault current of the same cycle flows with respect to the power supply frequency, and more accurate ground fault detection can be performed.

According to the ground fault sensing device according to claim 5, it is possible to set the ground fault detection level by adjusting the someone one side of the positive detection means and the negative side detection unit, according to claim 1 In addition to the effect described in any one of claims 4 to 4, there is an effect that the ground fault detection level can be set with a simple configuration.

[0035] According to the ground fault sensing device according to claim 6, since the positive and negative switching elements even if the detection is started from any of the power is supplied to the electromagnetic device when it is driven, claims In addition to the effect described in 5, the effect that the electric circuit can be quickly interrupted is exhibited.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a ground fault detection apparatus showing a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram when the ground fault current of FIG. 1 is detected from the positive side waveform.

FIG. 3 is an operation explanatory diagram when the ground fault current of FIG. 1 is detected from the negative side waveform.

FIG. 4 is an explanatory diagram of the operation of FIG. 1 when an induced lightning strike is detected.

FIG. 5 is a configuration block diagram of a ground fault detection device showing a second embodiment of the present invention.

FIG. 6 is an operation explanatory view when the ground fault current of FIG. 5 is detected from the positive side waveform.

FIG. 7 is an operation explanatory diagram when the ground fault current of FIG. 5 is detected from the negative side waveform.

FIG. 8 is an explanatory diagram of the operation when the induced lightning of the thing of FIG. 5 is detected.

[Explanation of symbols]

1 Zero-phase current transformer 2 Switching element 3 Electromagnet device 4 Positive side comparison means 5 Negative side comparison means 6 Logic means 7 Time delay means 8 Discrimination means 9 Waveform shaping means 10 Integrating means C1 Third capacitor C2 First capacitor C3 Second capacitor

Claims (6)

(57) [Claims] 1. A ground fault current detected in an AC circuit is detected.
A zero-phase current transformer, a positive-side comparison unit that outputs when the output signal of the zero-phase current transformer exceeds a predetermined value set on the positive side, and an output signal of the zero-phase current transformer is negative. Negative side comparing means for outputting when the value becomes equal to or less than a predetermined value set on the side, logical means for logically adding and outputting the outputs of the positive side and negative side comparing means, and the output of this logical means is a time valve. ground with the signal output by discriminating means for actuating the switching element Betsushite, the
In the detection device, the discrimination means is constantly charged only when the logic means outputs.
The first capacitor is discharged and the first capacitor is discharged.
Outputs a signal when the sensor voltage drops below a specified value
Always release the waveform shaping means and only when this waveform shaping means outputs.
The second capacitor is charged and the second capacitor is charged.
When the voltage on the
A ground fault detection device characterized by comprising an integrating means for outputting a signal to a grounding element . 2. A time delaying means for charging / discharging a third capacitor in response to the output of the logic means and outputting to the discriminating means as an output of the logic means when the third capacitor has a predetermined value or more. The ground fault detection device according to claim 1, further comprising: 3. The time delay means outputs as a one-shot signal when the third capacitor exceeds a predetermined value, and the waveform shaping means outputs the first capacitor to a substantially zero voltage when the time delay means outputs. Claim to discharge up to
2. The ground fault detection device according to 2. Wherein said waveform shaping means, characterized in that the charging time from a substantially zero voltage of the first capacitor to a predetermined value, and one cycle less time than the half period with respect to the power supply frequency of the AC circuit The ground fault detection device according to claim 3 . Wherein said positive and ground fault sensing device according to any one of claims 1 to 4, characterized in that the set either larger one than the other predetermined value of the negative-side comparison means . The method according to claim 6, wherein said switching element, characterized in that it is connected via the opening capable electromagnet device and the full-wave rectifying means contacts interposed AC circuit from the AC circuit
The ground fault detection device according to claim 5 .