JP2009081926A - Apparatus for detecting grounding current for resistor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus which can easily determine whether the state of the normal leak current of an electric path is in a range of being able to guarantee the detection accuracy of a requested grounding current for a resistor and also is practical and economical, relating to an apparatus such as a molded case circuit breaker, an earth leakage breaker, or a relay, which includes a means for detecting the ground leakage current of an electric path and detecting the magnitude of the leakage current due to resistor grounding, based on the phase difference between the magnitude and the voltage of the electric path. <P>SOLUTION: The apparatus includes a means that detects the ground leakage current of the electric path and computes the grounding current for the resistor, based on the phase shift between the magnitude and the voltage of the electric path, thereby detecting the grounding current for the resistor having surpassed the specified magnitude. The apparatus detects the grounding current for the resistor, including a means that issues an alarm when the ground leakage current is over a value that is set according to the detection sensitivity of the grounding current for the resistor. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The invention of the present invention is a circuit breaker, a leakage breaker or a relay having a means for detecting a ground leakage current of a circuit and detecting a resistance ground fault current based on the magnitude and a phase shift from the circuit voltage. Relates to a device such as

It is well known that the ground leakage current of the circuit includes a constant leakage current that flows through the capacitance of the circuit ground capacitance and the noise filter capacitance of the device, and a resistance ground fault current due to poor insulation.

Since the constant leakage current is a current flowing through the ground capacitance, the phase advances by 90 degrees with respect to the ground voltage, and the resistance ground fault current due to insulation failure is in phase with the ground voltage. Therefore, there is a phase difference between the circuit voltage and the ground leakage current that is determined by the ratio of the magnitude of the constant leakage current and the resistance ground fault current.

Therefore, a method is known in which only the resistance ground fault current due to insulation failure is classified based on the phase difference between the magnitude of the ground leakage current and the circuit voltage.
JP-A-2005-140532 JP 2006-71341 A

However, depending on the phase difference between the earth leakage current and the circuit voltage, the detection accuracy of the phase difference greatly affects the detection accuracy of the resistance ground fault current. Even if the detection accuracy of the phase difference is the same, the influence on the calculation result of the resistance ground fault current is almost not when the phase difference is near 0 degrees, but is considerably large when the phase difference is near 90 degrees.

Therefore, depending on the angle range of the phase difference of the ground leakage current with respect to the circuit voltage, the resistance ground fault current may not be detected with the required accuracy. For example, if the detection accuracy of the phase difference is ± 1 degree and an attempt is made to detect a resistance ground fault current of 1 mA with an accuracy of ± 10%, the accuracy can be guaranteed only by detection errors other than the phase difference. Is ignored, the leakage current always has a magnitude of 0 mA to about 6.3 mA, that is, the angle range of the phase difference is limited to 0 degree to about 81 degrees.

In other words, the detection accuracy of the phase affects the detection accuracy of the resistance ground fault current, but if you try to guarantee the detection accuracy of the resistance ground fault current at a phase difference close to 90 degrees, which is likely to cause errors, Therefore, it is necessary to improve the accuracy of detection, which increases the cost of the apparatus.

Therefore, the present invention detects a leakage current to the ground of the circuit, and based on the phase difference between the magnitude of the circuit and the circuit voltage, detects a magnitude of the leakage current due to the resistance ground fault or a circuit breaker or a leakage current. In devices such as circuit breakers or relays, it is possible to easily determine whether there is a constant leakage current state in the circuit within a range where the required resistance ground fault current detection accuracy can be guaranteed. It is intended to provide an economical device.

Therefore, in the first aspect of the present invention, the ground leakage current of the circuit is detected, the resistance ground fault current is calculated based on the phase shift between the magnitude and the circuit voltage, and the resistance ground fault current has a predetermined magnitude. Characterized in that, in a device having means for detecting exceeding, a means for issuing a warning when the ground leakage current exceeds a value set in accordance with the detection sensitivity of the resistance ground fault current is provided. An apparatus for detecting a resistance ground fault current is provided.

According to a second aspect of the present invention, there is provided the apparatus for detecting a resistance ground fault current according to the first aspect, wherein the means for issuing an alarm has means for temporarily functioning.

According to a third aspect of the present invention, the value of the ground leakage current set according to the detection sensitivity of the resistance ground fault current is a resistance ground fault calculated based on a phase shift between the ground leakage current and the circuit voltage. A device for detecting a resistance ground fault current, which is variably set from a vector synthesis of a constant leakage current set according to the current current value and the detection sensitivity of the resistance ground fault current Is provided.

According to a fourth aspect of the present invention, there is provided a circuit breaker for generating a warning when the resistance ground fault current exceeds a predetermined magnitude. The apparatus for detecting a resistance ground fault current according to any one of claims 1 to 3, wherein the earth leakage breaker or the earth leakage relay is provided.

According to a fifth aspect of the present invention, there is provided an earth leakage circuit breaker for interrupting a circuit when the resistance ground fault current exceeds a predetermined magnitude. 4. An apparatus having means for detecting a resistance ground fault current according to claim 1, wherein the apparatus is an earth leakage relay that generates an output.

According to the present invention, the ground leakage current of the circuit is detected, the resistance ground fault current is calculated based on the phase shift between the magnitude and the circuit voltage, and the resistance ground fault current has a predetermined magnitude. In a device equipped with a means for detecting exceeding, since the earth leakage current exceeds the value set according to the detection sensitivity of the resistance ground fault current, it is provided with a means for issuing an alarm. When the ground leakage current of the circuit is within a range where the detection accuracy of the ground fault current cannot be guaranteed, it can be easily determined whether or not the detected output meets the required accuracy when a predetermined resistance ground fault current is detected. Further, by providing the device with such a warning means, it is possible to obtain a device having a phase shift detection accuracy that does not interfere with practical use, and it is possible to reduce the cost of the device.

A first embodiment of the present invention is shown in FIG. FIG. 1 shows an example in which a circuit breaker 10 with a resistance ground fault current detection display function and the circuit breaker 10 are installed in an electric circuit. In FIG. 1, reference numeral 1 denotes a transformer for supplying a commercial voltage to the electric lines 2 and 2 ′, and the 2′-side terminal of the low-voltage side winding is grounded as 3. For convenience, the electric circuit will be described as a single-phase two-wire system, but the same principle can be applied to a single-phase three-wire electric circuit or a three-phase three-wire electric circuit with a Δ connection and a single-pole grounding type.

1001 and 1002 are switching contacts, and 1003 is an overcurrent detection element. When the current in the electric circuit exceeds a predetermined value, the overcurrent detection element 1003 acts on a switching mechanism (not shown) in a time period corresponding to the magnitude of the current. And 1002 are automatically opened. Reference numeral 1004 denotes a zero-phase current transformer that detects the difference between the reciprocating currents of the electric circuits 2 and 2 '. The current detected by the zero-phase current transformer 1004 is a zero-phase leakage current Io consisting of a constant leakage current Ioc flowing in the ground capacitance 4 of the circuit 2 and a ground-fault leakage current Ior flowing in the ground-fault resistor 5 due to insulation failure. It is.

Reference numeral 1005 denotes an input circuit for a current detected by the zero-phase current transformer 1004, which includes an over-input protection circuit, a filter circuit, an amplifier circuit, a phase shift circuit and the like as necessary. Note that the phase shift circuit is used for the purpose of correcting the phase difference between the actual zero-phase current and the current signal handled by the detection circuit, but may be included in the arithmetic circuit 1007.

Generally, the voltage of the electric circuit includes harmonics and high frequencies due to the nonlinearity of the transformer 1 and the load current waveform with respect to the original commercial fundamental wave. The current flowing through the ground fault resistor 5 linearly corresponds to those voltage waveform distortions. However, the current flowing through the ground capacitance 4 changes relatively as the frequency increases because the impedance changes with respect to the frequency of the waveform distortion component. Therefore, it is desirable to remove harmonics and high-frequency components with a filter in order to detect a ground fault current of only a commercial fundamental frequency more accurately.

Reference numeral 1006 denotes an input circuit for an electric circuit voltage, which has an insulating circuit for the electric circuit, an over-input protection circuit as in the case of 1005, and a filter circuit if necessary. In this case, the circuit voltage corresponds to the ground voltage.

Reference numeral 1007 denotes an arithmetic circuit that calculates the phase difference between the circuit voltage and the zero-phase current, and calculates the ground fault current for the resistance from the absolute magnitude of the phase difference and the zero-phase current. This will be described with reference to FIGS.

In FIG. 2, 6 is a circuit voltage vector and 7 is a zero-phase current vector. The zero-phase current 7 is a combined current of a constant leakage current 9 due to a resistance ground fault current 8 and a ground capacitance. The arithmetic circuit 1007 calculates the phase difference θ between the circuit voltage vector 6 and the zero phase current vector 7 from the time lag between the zero point of the circuit voltage and the zero point of the zero phase current, and the phase difference is calculated as the absolute value of the zero phase current vector 7. The magnitude of the resistance ground fault current 8 is calculated by multiplying by the cosine (cos) of θ.

FIG. 3 shows another method. FIG. 3 shows a method of calculating the magnitude of the resistance ground fault current 12 by integrating the instantaneous values of the circuit voltage 10 and the zero-phase current 11. (A) is an example where there is no phase difference between the circuit voltage and the zero-phase current. Since there is no phase difference, when the instantaneous values are multiplied, the value is doubled in the positive range of 0 or more. The average value is proportional to the magnitude of the resistance ground fault current.

(B) is an example in which the phase difference between the circuit voltage and the zero-phase current is 90 degrees. When the instantaneous values are multiplied, the average value is zero and the frequency is doubled. FIG. 3 is the same as the method by so-called synchronous rectification.

Here, the detection accuracy of the phase difference between the circuit voltage and the leakage current and the detection accuracy of the resistance ground fault current will be described with reference to FIG. In FIG. 4, when there is a zero-phase leakage current 16 having a small phase difference θ1 with respect to the circuit voltage phase 15, if the detection error range of the phase difference is ± α, the error α with respect to the resistance ground fault current 17 to be detected The effect of is 18 and is relatively small with respect to 17. However, when the phase difference of the leakage current 16 ′ is large as θ2 with respect to the circuit voltage phase 15, the resistance ground fault current 17 ′ is small even if the phase difference detection error range is the same as ± α and the influence of the error α. Since it becomes as large as ± 18 ', it becomes relatively large with respect to 17', and even if the detection accuracy of the phase difference is the same, the detection accuracy of the resistance ground fault current greatly changes.

Therefore, the phase difference between the circuit voltage and the leakage current that can guarantee the detection accuracy, in other words, the magnitude of the leakage current at all times, is limited by the requirement of the magnitude and accuracy of the resistance ground fault current to be detected. As described above, when the detection accuracy of the phase difference is ± 1 degree, if the detection accuracy 18 when the resistance ground fault current 17 is 1 mA is to be guaranteed to 0.1 mA, 10% of 17, the resistance component of 1 mA. The phase difference between the circuit voltage and the zero-phase leakage current with respect to the ground fault current is within 81 degrees, or when the resistance ground fault current is 1 mA, the magnitude of the zero-phase leakage current is not within 6.4 mA. You will not be able to answer. Strictly speaking, in the case of a device such as a circuit breaker with a resistance ground fault current detection function shown in FIG. 1, the detection of the above resistance ground fault current 1 mA is guaranteed with an accuracy of ± 0.1 mA. The constant leakage current must be within 6.3 mA. That is, the maximum value of the constant leakage current is within 6.3 mA, and the zero-phase leakage current at that time is 6.3 mA (at the time of resistance ground fault current 0 mA) to 6.4 mA depending on the magnitude of the resistance ground fault current. (Resistance ground fault current 1 mA) must be within.

When the phase difference detection accuracy is ± 5 degrees, the phase difference between the circuit voltage and the zero-phase leakage current is within 45 degrees when the resistance ground fault current is 1 mA, or the magnitude of the zero-phase leakage current is large. If it is not within 1.4 mA, the above-mentioned requirement for detection accuracy cannot be answered, and at that time, the leakage current must always be within 1 mA. Therefore, the range of the zero-phase leakage current is within the range from 1 mA when there is no resistance ground fault current to 1.4 mA when the resistance ground fault current is 1 mA, depending on the magnitude of the resistance ground fault current. There must be.

FIG. 5 explains how the constant leakage current that can guarantee the detection accuracy of the resistance ground fault current and the ground leakage current that can guarantee the detection accuracy change according to the magnitude of the resistance ground fault current. . In addition, when trying to detect the 1 mA resistance ground fault current given in the above example with an accuracy of ± 10%, if errors other than the phase difference detection error can be ignored, the phase difference is 45 degrees. The permissible detection accuracy is ± 5 degrees, but if the phase difference is 85 degrees, the required phase difference detection accuracy is ± 0.5 degrees, and the phase difference is detected as the phase difference approaches 90 degrees. The demand for accuracy becomes stricter and the cost of the apparatus increases. However, if there are many cases where the phase difference is within 45 degrees when the resistance ground fault current to be detected is flowing in a general circuit, a device with a phase difference detection accuracy of ± about 5 degrees is sufficient. In the unlikely event that the phase difference is exceeded, it is practically sufficient to know that the accuracy cannot be guaranteed by an alarm.

In FIG. 1, reference numeral 1008 denotes a means for outputting the result of the resistance ground fault current calculation by the arithmetic circuit 1007. When the calculation result exceeds a predetermined value, an output is generated by voice or a lamp or output at a contact. Reference numeral 1009 denotes an alarm output means for determining whether or not the calculation result satisfies the required accuracy, and the magnitude of the ground leakage current is not more than a value set in accordance with the detection sensitivity of the resistance ground fault current. Is determined by the arithmetic circuit 1007 and displayed / outputted. The display output may either output that the accuracy can be guaranteed or output that the accuracy cannot be guaranteed. Further, 1009 may receive the output of the direct input circuit 1005 and determine whether the ground leakage current is equal to or less than a value set in accordance with the detection sensitivity of the resistance ground fault current. Reference numeral 1012 denotes a means for temporarily functioning the alarm output means, such as a push button SW. Only when the SW is pressed, the ground leakage current is set according to the detection sensitivity of the resistance ground fault current. It is judged whether or not the value is below the specified value, and an alarm is output. In this case, the value set according to the detection sensitivity of the resistance ground fault current is a constant leakage current value that can guarantee the detection accuracy described above.

The circuit breaker as shown in Fig. 1 is used as follows. When it is first installed on a healthy electrical circuit, 1012 is first operated. As a premise, since the electric circuit is healthy, the resistance ground fault current is close to zero, and almost always leakage current flows. If the leakage current is less than the value that can guarantee the accuracy of the resistance ground fault current to be detected, an alarm will not be generated, so a circuit breaker can be installed as it is, and then if a predetermined resistance ground fault current occurs. A detection output is generated with the required accuracy. If an alarm is generated when 1012 is operated, the detection sensitivity of the resistance ground fault current cannot be guaranteed with the detection sensitivity, so change to one with low detection sensitivity, or the resistance ground fault current of the circuit breaker If there is a means for switching the detection sensitivity current, reset the sensitivity to a slower direction.

It is possible to omit the function 1012 in FIG. In that case, in the arithmetic circuit 1007, as shown in FIG. 5, the vector of the constant leakage current that can guarantee the accuracy and the resistance ground fault current calculated by the arithmetic circuit 1007 is combined, and the magnitude is set to the above-mentioned resistance component. The value set according to the detection sensitivity of the ground fault current is compared with the ground leakage current. If the ground leakage current exceeds the set value, an alarm is issued. As a result, the circuit breaker shown in Fig. 1 can always check whether the leakage current is always within a range where accuracy can be guaranteed, so that the circuit breaker can be used with the required accuracy from installation to use. Whether or not the ground fault current can be detected can be determined.

Note that the constant leakage current that can guarantee the above-mentioned accuracy needs to be set for each detection sensitivity when the detection sensitivity of the resistance ground fault current can be switched in stages. In addition, as described above, the setting value to be compared with the ground leakage current does not need to be calculated by vector synthesis each time, but a value corresponding to each detected resistance ground fault current is set in the arithmetic circuit in advance. You may make it compare with an electric current.

As described above, when the detection accuracy of the phase difference is ± 1 degree and the resistance ground fault current 1 mA is to be detected with an accuracy of ± 10%, the zero-phase leakage current when there is no resistance ground fault current Since there is almost no difference between the upper limit of 6.3 mA and the zero-phase current upper limit of 6.4 mA when the resistance ground fault current is 1 mA, the upper limit of the zero-phase leakage current is always constant in the range of 6.3 to 6.4 mA. There is no problem.

6 and 7 show an embodiment in which a resistance ground fault current detection function is added to an earth leakage breaker that breaks the circuit depending on the magnitude of the leakage current, and functions in stages with respect to the leakage current. Reference numerals 1001 to 1009 and 1012 in the embodiment of FIG. 6 have the same functions as those of the embodiment of FIG. In the figure, reference numeral 1010 denotes a trip device that acts on an opening / closing mechanism (not shown) and separates the contacts 1001 and 1002 and operates according to the determination result of the arithmetic circuit 1007. In this case, the leakage current can be either a ground leakage current or a resistance ground fault current. The embodiment in FIG. 7 is an example in which a leakage current detection circuit 1011 for driving the trip device 1010 is provided separately from the arithmetic circuit 1007. The earth leakage breakers shown in Figs. 6 and 7 detect whether the resistance ground fault current is 1 mA or more, for example, if the insulation failure does not require urgent, and the emergency such as electric shock that the leakage current exceeds 30 mA. In the case of an accident that requires an operation, it operates in stages so as to interrupt the electric circuit. At that time, it is possible to know whether or not the detection output of the resistance ground fault current detection before the interruption operation is performed within a range in which the accuracy can be guaranteed.

6 and 7, the display unit 1008 can be omitted, and the trip coil 1010 can be suddenly driven when the arithmetic circuit 1007 detects a predetermined resistance ground fault current. In this case, if the display of 1009 is electrically backed up or a mechanical latch mechanism is used, the circuit can be shut off by driving the trip coil 1010 based on the detection accuracy required to be shut off later. You can determine whether it was done. It is also possible to drive the trip coil 1010 even when the ground leakage current exceeds the range in which the required detection accuracy can be guaranteed.

FIG. 8 shows an earth leakage relay that does not have a main circuit contact that interrupts the circuit. In the figure, reference numerals 1004 to 1009 are the same as those in FIG. However, the zero-phase current transformer may be installed outside the relay casing or built in. Further, the zero-phase current transformer is not provided in the electric circuit, but may be one that detects the ground leakage current of the B-type ground wire of the transformer. Reference numeral 1010 'denotes a relay, which outputs a contact to the outside instead of the circuit breaker of FIG. 6 or 7 interrupting the circuit. Alternatively, a signal may be output from the arithmetic circuit 1007 to the outside.

In such a relay, in addition to the relay operation of 1010 ′, it is possible to detect the resistance ground fault current of the prior circuit, and the detected resistance ground fault current depends on the accuracy with which the resistance ground fault current is required. You can determine at a glance whether it is a thing. Further, the display unit 1008 is omitted, and the relay unit 1010 ′ is operated when the resistance ground fault current exceeds a predetermined value as described in “0034”, and the alarm unit 1009 is operated during the relay operation. You may make it show that the ground leakage current exceeded the predetermined range.

In the above description, the display means 1008 has been described in the case where the detection sensitivity of the resistance ground fault current is one, but a plurality of display means may be provided in stages and selectively switched. In addition, it is optional to add a means for calculating the leakage current constantly by the arithmetic circuit 1007 and displaying the value.

In addition to circuit breakers, earth leakage circuit breakers, relays, and other monitoring devices with other functions can be used.

Configuration diagram of circuit breaker with resistance ground fault current alarm function according to the present invention Explanatory drawing of the method to detect the resistance ground fault current from the ground leakage current Explanatory drawing of the method to detect the resistance ground fault current from the ground leakage current Diagram explaining detection error due to phase difference between voltage and ground leakage current Diagram of change in ground leakage current due to constant leakage current that can guarantee accuracy and detected resistance ground fault current Configuration diagram of earth leakage breaker with resistance ground fault current alarm function according to the present invention Configuration diagram of earth leakage breaker with resistance ground fault current alarm function according to the present invention Configuration diagram of relay with resistance ground fault current alarm function according to the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transformer 2, 2 '... Electric circuit 3 ... Grounding 4 ... Ground capacitance of electric circuit 5 ... Ground fault resistance 6 ... Voltage vector 7 ... Ground leakage current vector 8: Resistance ground fault current vector 9: Constant leakage current vector 10: Circuit waveform unit waveform 11, 13: Ground leakage current waveform 12, 14: Circuit voltage unit waveform Accumulated waveform of instantaneous value and instantaneous value of ground leakage current 15... Voltage vector 16, 16 '.. ground leakage current vector 17, 17' .. resistance ground fault current 18, 18 '.. detection error 1001, 1002 ... Main circuit contact 1003 ... Overcurrent detection element 1004 ... Current transformer 1005 ... Waveform shaping circuit 1006 ... Waveform shaping circuit 1007 ... Arithmetic circuit 1008 ... Display means 1009 ... Alarm means 1010 ... Trip carp 1010 '... relay 1011 ... leakage detector 1012 ... temporary function means

Claims (5)

Means for detecting a ground leakage current of a circuit, calculating a resistance ground fault current based on a phase shift between the magnitude and the circuit voltage, and detecting that the resistance ground fault current exceeds a predetermined magnitude Detects a resistance ground fault current characterized by having a means to issue an alarm when the ground leakage current exceeds a value set according to the detection sensitivity of the resistance ground fault current. Device to do. 2. The apparatus for detecting a resistance ground fault current according to claim 1, wherein said alarm generating means includes means for temporarily functioning. The value of the ground leakage current set according to the detection sensitivity of the resistance ground fault current is the current value of the resistance ground fault current calculated based on the phase shift between the ground leakage current and the circuit voltage, and the resistance An apparatus for detecting a resistance ground fault current, wherein the resistance ground fault current is variably set based on a vector composition of a constant leakage current set in accordance with a detection sensitivity of the ground fault current. The device for detecting a resistance ground fault current is a circuit breaker for wiring that generates an alarm when the resistance ground fault current exceeds a predetermined magnitude, or a ground fault circuit breaker or a ground fault for which the alarm is a prior warning. 4. The device for detecting a resistance ground fault current according to claim 1, wherein the device is a relay. The device provided with the means for detecting the resistance ground fault current is an earth leakage breaker that interrupts the circuit or an earth leakage relay that generates an output when the resistance ground fault current exceeds a predetermined magnitude. 4. An apparatus comprising means for detecting a resistance ground fault current according to claim 1, wherein said resistance ground fault current is detected.

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