JP6714455B2 - Ground capacitance measuring device and ground capacitance measuring method - Google Patents

Description

The present invention is capable of measuring the total ground electrostatic capacity of the entire low-voltage side electric circuit of an electric equipment and the ground electrostatic capacity of each of a plurality of downstream side branch electric circuits branched on the downstream side of the low-voltage side electric circuit. The present invention relates to a device and a method for measuring capacitance to ground.

In Japanese Unexamined Patent Application Publication No. 2014-92386 (Patent Document 1), an upstream side is connected to a high-voltage side electric circuit via a power receiving transformer, and a downstream side is divided into a plurality of systems to connect to a load device. A ground insulation resistance measuring device for measuring a ground insulation resistance is described. The device superimposes a voltage signal as a monitoring signal on the class B ground line of the power receiving transformer and detects the leakage current flowing in the class B ground line due to the AC voltage to measure the ground insulation resistance. A fixed type measuring device configured to detect a current flowing through a desired position of the low-voltage side electric circuit and to measure a resistance component included in the current based on the current and the voltage signal transmitted from the fixed type measuring device. And a portable measuring device configured.

In the earth insulation resistance measuring device, since the voltage signal is transmitted from the fixed measuring device to the portable measuring device, it is not necessary to detect the voltage by the portable measuring device, and the clip for connection is used to measure the earth insulating resistance. There is no need for complicated work such as connecting the cable to an electric wire. Further, it is possible to know the deterioration of the insulation resistance to any lineage by the portable measuring device that you are generated easily and quickly.

JP, 2014-92386, A

By the way, in recent years, the low-voltage side electric circuit has become long, and since an electronic device having a built-in line filter or the like having a capacitor as a constituent element is often connected as a load, the capacitance to ground of the low-voltage side electric circuit is reduced. It's getting bigger. As described above, when the capacitance to ground of the low-voltage side electric path becomes large, a leakage current flows and the leak breaker or the leak alarm operates, so there is an increasing demand for measurement of capacitance to ground.

Therefore, it is conceivable to measure the ground capacitance at a desired position of the low-voltage side electric circuit (each downstream branch electric circuit on the low-voltage side electric circuit side) using the ground insulation resistance measuring device described in the above-mentioned publication. However, the capacitance to ground varies easily depending on the operating conditions of the load connected to the branch circuit on the downstream side of the low-voltage side circuit (operation mode of equipment, on/off of heating and cooling equipment, etc.), so the capacitance to ground is measured. In the case where the capacitance to ground is varied, accurate measurement cannot be performed with the configuration of the measuring device described in the above publication.

The present invention has been made in view of the above, and a ground capacitance measuring device and a ground electrostatic capacitance measuring device capable of measuring the ground capacitance in a downstream branch electric circuit on the low voltage side electric circuit side with an accurate and simple configuration. It is an object to provide a capacity measuring method.

According to the preferred embodiment of the ground capacitance measuring device according to the present invention, the total ground capacitance of the entire low-voltage side electric path of the electrical equipment and a plurality of downstream branch electric paths branched on the downstream side of the low-voltage side electric path A ground capacitance measuring device capable of measuring the capacitance is configured. The ground capacitance measuring device includes a transmitter and main receiver and a sub receiver. The transmitter/main receiver is installed on the B-type ground line of the low-voltage side electric line, applies a voltage signal having a frequency different from the commercial frequency to the B-type ground line, and causes the low-voltage side electric line and the It is configured to detect a leakage current circulating through the ground to the class B ground line at predetermined time intervals. The transmitter/main receiver also calculates the total capacitance to ground on the basis of the voltage signal and the detected leakage current, and the leakage current used for the calculation and the total capacitance to ground. Based on the leakage current and the voltage signal detected when the predetermined condition is satisfied, the first ratio calculating means for calculating the first ratio which is the ratio of the Second ratio for calculating the second ratio which is the ratio of the leakage current used for the recalculation and the recalculated total capacitance to ground, and the total ground capacitance recalculation means for recalculating the total capacitance to ground The calculation means and the voltage signal correction means for correcting the applied voltage signal based on the ratio of the first ratio and the second ratio are provided. Then, the transmitter/main receiver is configured to apply the corrected voltage signal corrected by the voltage signal correcting means to the class B ground line instead of the voltage signal when a predetermined condition is satisfied. Further, the sub transmitter is installed in any of the plurality of downstream branch electric circuits, and is configured to detect a shunt current that is a shunt component of the leakage current flowing through the downstream branch electric circuit. Then, the sub-receiver is configured to calculate the ground capacitance of the downstream branch electric circuit based on the detected shunt current and the ratio of the first ratio and the second ratio.

Here, in the aspect of "installed in any of the plurality of downstream branch electric paths" in the present invention, in addition to the aspect in which the sub-receiver is installed only in any one of the plurality of downstream branch electric paths, Preferably, the sub-receiver is installed so as to include one or more of the downstream branch electric circuits.

The present inventor has found that the ratio of the leakage current circulated to the class B grounding wire to the shunt current measured in the downstream branch circuit is such that the total static current capacity of the entire low-voltage side circuit and the static current of the downstream branch circuit. Paying attention to the fact that it is equal to the ratio to the capacitance, when measuring the capacitance to ground in the downstream branch circuit, the ratio of the leakage current circulated to the class B ground line and the total static current capacity is always approximately The voltage signal to be applied is corrected so as to have the same value. As a result, the operating status of the load connected to one of the downstream branch circuits (such as the operation mode of the equipment and the on/off of cooling/heating equipment) is changed, and the capacitance to ground is measured on the downstream branch circuit. Even when the capacitance to ground changes, the capacitance to ground in the downstream branch circuit can be accurately measured. In addition, the ground capacitance of the downstream branch circuit is only calculated based on the shunt current flowing in the downstream branch circuit and the ratio of the leakage current circulating in the class B ground line and the total static current capacity. Therefore, it is possible to easily calculate the capacitance to ground of the downstream branch electric circuit in a very short time.

According to a further embodiment of the ground capacitance measuring device of the present invention, the transmitter/main receiver is configured to apply a high-frequency voltage signal having a frequency higher than the commercial frequency to the class B ground line as a voltage signal. Has been done.

According to the present embodiment, it is possible to make almost no leakage current flow through the insulation resistance due to the impedance ratio of the insulation resistance of the entire low-voltage side electric circuit and the total capacitance to ground. The insulation resistance can be ignored. As a result, the calculation of the capacitance to ground can be simplified and the measurement time can be further shortened. Further, when a clamp type is used for the transmitter and the main receiver, the diameter of the iron core can be reduced, so that the device can be made compact and the cost can be reduced.

According to a preferred embodiment of the ground capacitance measuring method according to the present invention, the total ground capacitance of the entire low-voltage side electric path of the electrical equipment and a plurality of downstream branch electric paths branched on the downstream side of the low-voltage side electric path. A ground capacitance measuring method for measuring a ground capacitance is configured. The ground capacitance measuring method includes a transmitter and main receiver and a sub receiver. The transmitter/main receiver is installed on the B-type ground line of the low-voltage side electric line, applies a voltage signal of a frequency different from the commercial frequency to the B-type ground line, and causes the low-voltage side due to the voltage signal. It is configured to detect the leakage current flowing back to the type B ground wire via the electric path and the ground every predetermined time. The sub-receiver is installed in any of the plurality of downstream branch circuits and is configured to detect a shunt current that is a shunt component of the leakage current flowing through the downstream branch circuit. In the ground capacitance measuring method, (a) the total ground capacitance is calculated based on the voltage signal and the detected leakage current, and (b) the leakage current used for the calculation and the total ground capacitance. A first ratio, which is a ratio, is calculated, and (c) it is determined whether or not a predetermined condition is satisfied, and (d) when the predetermined condition is satisfied, the leakage current detected when the predetermined condition is satisfied. And recalculate the total capacitance to ground based on the voltage signal, and calculate the second ratio, which is the ratio of the leakage current used for recalculation and the recalculated total capacitance to ground, and apply (e). The voltage signal is corrected based on the ratio of the first ratio and the second ratio, and the corrected voltage signal which is changed into the voltage signal is applied to the class B ground line, and (f) the shunt current detected by the sub-receiver. The capacitance to ground of the downstream branch electric circuit is calculated based on the current and the ratio of the first ratio and the second ratio.

Here, in the aspect of "installed in any of the plurality of downstream branch electric paths" in the present invention, in addition to the aspect in which the sub-receiver is installed only in any one of the plurality of downstream branch electric paths, Preferably, the sub-receiver is installed so as to include one or more of the downstream branch electric circuits.

The present inventor has found that the ratio of the leakage current circulated to the class B grounding wire to the shunt current measured in the downstream branch circuit is such that the total static current capacity of the entire low-voltage side circuit and the static current of the downstream branch circuit. Paying attention to the fact that it is equal to the ratio to the capacitance, when measuring the capacitance to ground in the downstream branch circuit, the ratio of the leakage current circulated to the class B ground line and the total static current capacity is always approximately The voltage signal to be applied is corrected so as to have the same value. As a result, the operating status of the load connected to one of the downstream branch circuits (such as the operation mode of the equipment and the on/off of cooling/heating equipment) is changed, and the capacitance to ground is measured on the downstream branch circuit. Even when the capacitance to ground changes, the capacitance to ground in the downstream branch circuit can be accurately measured. In addition, the ground capacitance of the downstream branch circuit is only calculated based on the shunt current flowing in the downstream branch circuit and the ratio of the leakage current circulating in the class B ground line and the total static current capacity. Therefore, it is possible to easily calculate the capacitance to ground of the downstream branch electric circuit in a very short time.

According to a further aspect of the method for measuring the capacitance to ground according to the present invention, the transmitter/main receiver is configured to apply a high-frequency voltage signal having a frequency higher than the commercial frequency as a voltage signal to the B-type ground line. Has been done.

According to this embodiment, it is possible to make almost no leakage current flow through the insulation resistance due to the impedance ratio of the insulation resistance of the entire low-voltage side electric circuit and the total capacitance to ground. The insulation resistance can be ignored. As a result, the calculation of the capacitance to ground can be simplified and the measurement time can be further shortened. Further, when a clamp type is used for the transmitter and the main receiver, the diameter of the iron core can be reduced, so that the device can be made compact and the cost can be reduced.

According to the present invention, it is possible to measure the capacitance to ground in the downstream branch circuit on the low voltage side circuit side accurately and with a simple configuration.

It is explanatory drawing which shows a mode that the total earth capacitance Ca, Cp in the low voltage side electric circuit 70 of the electric equipment 80 is measured using the earth capacitance measuring device 1 which concerns on embodiment of this invention. FIG. 3 is a block diagram showing a schematic configuration of a transmitter/main receiver 10. 3 is a block diagram showing a schematic configuration of a sub receiver 30. FIG. 5 is a simulation circuit diagram showing a simulation circuit for obtaining a total ground capacitance Ca in the low voltage side electric circuit 7. FIG. 5 is an equivalent circuit diagram showing an equivalent circuit for obtaining a total ground capacitance Ca in the low voltage side electric circuit 7. FIG. 7 is a flowchart showing an example of voltage signal correction processing executed by the control unit 22 of the transmitter/main receiver 10. 6 is a flowchart showing an example of a ground capacitance calculating process executed by a control unit 42 of the sub receiver 30. It is a vector diagram showing the vector relationship of the voltage signal V, the leak current Ig, the potential difference Vc between both ends of the total ground capacitance Ca, and the synthetic ground resistance Re.

Next, the best mode for carrying out the present invention will be described using embodiments.

As shown in FIG. 1, the ground capacitance measuring device 1 according to the embodiment of the present invention includes an entire electric path in a low-voltage side electric path 70 arranged on the low-voltage side of an electric facility 80 with a power receiving transformer 90, 92 interposed therebetween. Of the transmitter/main receiver 10 configured to be able to measure the total ground capacitance Ca of the above, and the ground capacitance CP of each of the plurality of downstream branch electric paths 72 branched on the downstream side of the low voltage side electric path 70. And a sub-receiver 30 configured as possible.

The neutral point of the secondary windings of the power receiving transformers 90 and 92 is connected to the type B ground electrode EB via the ground line L1. Further, although not shown, various loads (for example, a personal computer, a heating/cooling device, a processing device, a lighting device, etc.) are connected to the downstream side of the plurality of downstream branch electric paths 72, and the ground line L2. Is connected to the D-type ground electrode ED via.

As shown in FIG. 2, the transmitter/main receiver 10 electrically connects to the signal injection clamp 12 and the clamp sensor 14 which are clamped to the ground line L1 connected to the type B ground electrode EB, and the signal injection clamp 12. The signal output unit 16 connected to the clamp sensor 14, the filter 18 electrically connected to the clamp sensor 14, the A/D converter 20 electrically connected to the filter 18, the signal output unit 16 and the A/D converter 20. The control unit 22 is electrically connected to the control unit 22, and the operation unit 24, the display unit 26, and the communication unit 28 electrically connected to the control unit 22 are mainly configured. For example, the control unit 22 is installed in a switchboard room or the like. It

The signal injection clamp 12 is configured so that the voltage signal V output from the signal output unit 16 can be applied to the ground line L1 connected to the type B ground electrode EB. As shown in FIG. 1, when the ground lines 90a and 92a of the plurality of power receiving transformers 90 and 92 are connected to the B-type ground electrode EB via the common ground line L1, the ground lines 90a and 92a are connected. It is desirable to install the signal injection clamp 12 on the ground line L1 in the immediate vicinity of the type B grounding electrode EB to which is coupled. The clamp sensor 14 is configured to be able to detect a current signal (current circulating in the ground) flowing in the low voltage side electric circuit 70. The filter 18 is caused by applying the voltage signal V ₀ to the current signal of the frequency component of the voltage signal V ₀ from the current signal detected by the clamp sensor 14, that is, the ground line L1 connected to the type B ground electrode EB. Then, a signal corresponding to the leakage current Ig ₀ flowing in the low voltage side electric circuit 70 is taken out. The A/D converter 20 is configured to convert a signal corresponding to the leakage current Ig ₀ into a digital value. Further, the operation unit 24 has a switch for turning on/off the power supply, an operation button for setting the value of the voltage signal V ₀ applied to the ground line L1 connected to the type B ground electrode EB, and the like. ..

The control unit 22 is constructed as a microprocessor including a CPU, not shown Figure, a ROM for storing the processing programs of the CPU, a RAM that temporarily stores data, input and output ports (not shown), Is equipped with. A power supply ON/OFF signal from the operation unit 24, a voltage signal V ₀ , a digital signal corresponding to the leakage current Ig from the A/D converter 20, and the like are input to the control unit 22 via an input port. Here, in the present embodiment, the frequency of the voltage signal V ₀ is set to a frequency higher than the commercial frequency (50 Hz to 60 Hz), for example, selected from the range of 100 Hz to 500 Hz. The reason for setting the frequency of the voltage signal V to a high frequency in this way is as follows.

As shown in FIG. 4, the low-voltage side electric path 70 of the present embodiment has a total ground electrostatic capacity Ca that is the sum of the ground electrostatic capacity Cp of the entire low-voltage side electric path 70 and the insulation of the entire low-voltage side electric path 70. Although the total parallel insulation resistance combined value R of the resistors and the parallel circuit portion 52 connected in parallel are provided, the voltage signal V ₀ applied to the ground line L1 connected to the type B ground electrode EB Since the frequency is set to the high frequency as described above, the leakage current Ig hardly flows through the total parallel insulation resistance combined value R due to the impedance ratio between the total ground capacitance Ca and the total parallel insulation resistance combined value R. The total parallel insulation resistance combined value R can be ignored. As a result, in the low voltage side electric circuit 70 of the present embodiment, as shown in FIG. 5, the total ground capacitance Ca and the series combined insulation resistance Re of the B type ground resistance Reb and the D type ground resistance Red are connected in series. It can be replaced with an equivalent circuit that is only connected. Since the total parallel insulation resistance combined value R can be ignored in this way, the calculation of the total ground capacitance Ca can be simplified.

In addition, the control unit 22 outputs a display signal to the display unit 26 through an output port. The transmitter/main receiver 10 wirelessly exchanges various data and various signals with the sub receiver 30 via the communication unit 28. Specifically, the transmitter/main receiver 10 receives a power-on/off signal, which will be described later, from the sub-receiver 30 via the communication unit 28, and the reference ratio k ₀ , which will be described later, is set to the sub-receiver 30. Is being output to.

As shown in FIG. 3, the sub-receiver 30 is electrically connected to the clamp sensor 32, which is clamped in any of the plurality of downstream branch electric paths 72 of the low voltage side electric path 70 (see FIG. 1 ), and the clamp sensor 32. Filter 34, A/D converter 36 electrically connected to filter 34, control unit 38 electrically connected to A/D converter 36, and operation electrically connected to control unit 38 The unit 40, the display unit 42, and the communication unit 44 are mainly configured, and are configured so that a measurer who measures the ground capacitance Cp of the downstream branch electric path 72 can be carried around.

The clamp sensor 32 is configured so as to be able to detect a shunt current signal flowing in the downstream branch electric path 72 as a shunt component of the current signal flowing in the low voltage side electric path 70 (current circulating in the ground). The filter 34 is configured to extract a current signal having a frequency component of the voltage signal V ₀ , that is, a signal corresponding to the shunt current Igp which is a shunt component of the leakage current Ig, from the shunt current signal detected by the clamp sensor 32. .. The A/D converter 36 is configured to convert a signal corresponding to the shunt current Igp into a digital value. The operation unit 40 has a switch for turning the power on and off.

The control unit 38 is constructed as a microprocessor including a CPU, not shown Figure, a ROM for storing the processing programs of the CPU, a RAM that temporarily stores data, input and output ports (not shown), Is equipped with. A power on/off signal from the operation unit 40, a digital signal corresponding to the shunt current Igp from the A/D converter 36, and the like are input to the control unit 38 via an input port. Further, the control unit 38 outputs a display signal or the like to the display unit 42 via the output port. The sub receiver 10 wirelessly exchanges various data and various signals with the transmitter/main receiver 10 via the communication unit 44. Specifically, the sub receiver 30 receives a reference ratio k ₀ described later from the transmitter/main receiver 10 via the communication unit 44, and transmits a power on/off signal from the operation unit 40. It is output to the device/main receiver 10.

Next, an operation of the ground capacitance measuring apparatus 1 thus configured, particularly, an operation when measuring the ground capacitance Cp of the downstream side branch electric path 72 in the low voltage side electric path 70 of the electric equipment 80 will be described. FIG. 6 is a flowchart showing an example of the voltage signal correction process executed by the control unit 22 of the transmitter/main receiver 10, and FIG. 7 is a flowchart showing the electrostatic grounding process executed by the control unit 38 of the sub receiver 30. It is a flow chart which shows an example of capacity calculation processing. These processes are executed when both the transmitter/main receiver 10 and the sub receiver 30 are powered on. First, the voltage signal correction process by the transmitter/main receiver 10 will be described, and then the ground capacitance calculation process by the sub receiver 30 will be described.

When the voltage signal correction processing is executed, the CPU of the control unit 22 of the transmitter/main receiver 10 first applies the voltage signal V to the ground line L1 connected to the type B ground electrode EB via the signal injection clamp 12. ₀ is applied (step S100). Then, the leakage current Ig ₀ flowing through the low-pressure side path 70 due to the voltage signal V ₀ and detects by the clamp sensor 14, a phase difference based on the voltage signal V ₀ and the detected leakage current Ig ₀ theta _0, The total capacitance to ground Ca ₀ and the series combined insulation resistance Re ₀ are calculated (step S102).

That is, the relationship between the voltage signal V, the leakage current Ig, the potential difference Vc at both ends of the total ground capacitance Ca, and the potential difference Vr at both ends of the series combined insulation resistance Re is as shown in FIG. , (2), (3), and (4), the phase difference θ ₀ , the potential differences Vc and Vr, the total ground capacitance Ca _0, and the series combined insulation resistance Re ₀ are obtained. The control unit 22 that executes the process of step S102 for calculating the total ground capacitance Ca ₀ based on the voltage signal V ₀ and the detected leakage current Ig ₀ is the “total ground capacitance calculating means” of the present invention. It is an example of a corresponding implementation configuration.

(Equation 1)
Vr=V·Cos θ (1)
Vc=V·sin θ (2)
Ca=Ig/(2πf·Vc·sin θ) (3)
Re=Vr·cos θ/Ig (4)

Then, the detected leak current Ig _{0, the} calculated total ground capacitance Ca ₀ , and the series combined insulation resistance Re ₀ are displayed on the display unit 26 (step S104), and the power-on signal from the sub receiver 30 is received. A process of determining whether or not it is executed (step S106). Here, the power-on signal from the sub receiver 30 is input to the communication unit 28 of the transmitter/main receiver 10. The fact that the power-on signal is transmitted from the sub-receiver 30 means that the measurement of the ground capacitance Cp in the downstream branch electric circuit 72 by the sub-receiver 30 has started. The control unit 22 that executes the process of step S106 for determining whether or not the power-on signal from the sub-receiver 30 is received is an example of an implementation configuration corresponding to the “determination unit” in the present invention.

If the transmitter/main receiver 10 has not received the power-on signal from the sub-receiver 30, from step S102 until the transmitter/main receiver 10 receives the power-on signal from the sub-receiver 30. The processes up to step 106 are repeatedly executed. On the other hand, when the transmitter/main receiver 10 receives the power-on signal from the sub receiver 30, that is, when the measurement of the ground capacitance Cp in the downstream branch electric path 72 by the sub receiver 30 is started. Performs a process of calculating a reference ratio k ₀ (k ₀ =Ig ₀ /Ca ₀ ) between the leakage current Ig ₀ and the total capacitance Ca ₀ to ground (step S108), and also calculates the calculated reference ratio k ₀ . It transmits to the sub receiver 30 (step S110). When the transmitter/main receiver 10 receives the power-on signal from the sub-receiver 30, that is, when the measurement of the ground capacitance Cp in the downstream branch electric path 72 by the sub-receiver 30 is started. 2 is an example of an implementation configuration corresponding to “when a predetermined condition is satisfied” in the present invention. The control unit 22 that performs step S108 to calculate the baseline ratio k ₀ of the leakage current Ig ₀ total earth capacitance Ca ₀ corresponds to a "first ratio calculating means" in the present invention, reference The ratio k ₀ is an example of an implementation configuration corresponding to the “first ratio” in the present invention.

Subsequently, a process of applying the voltage signal V _n to the ground line L1 connected to the type B ground electrode EB via the signal injection clamp 12 is executed (step S112). Here, when the process of step S112 is performed for the first time, since n=0, the voltage signal V ₀ is applied to the ground line L1. Then, the leakage current _{Ig n + 1} flows to the low pressure side path 70 due to the voltage signal _{V 0} and detects by the clamp sensor 14, a phase difference theta _{n +} 1 on the basis of the leakage current _{Ig n + 1} which is the voltage signal _{V 0} and the detection, The total ground capacitance Ca _n+1 and the series combined insulation resistance Re _n+1 are calculated (step S114). The control unit 22 that executes the process of step S114 for calculating the total ground capacitance Ca _n+1 based on the voltage signal V ₀ and the detected leakage current Ig _n+1 is “total ground capacitance recalculation” in the present invention. 2 is an example of an implementation configuration corresponding to "means".

Subsequently, a process of calculating a ratio k _n+1 (k _n+1 =Ig _n+1 /C _n+1 ) of the leakage current Ig _n+1 and the total capacitance C _n+1 to the ground is executed (step S116), and the reference ratio calculated in step S108. The corrected voltage signal V _n+1 (V _n+1 =(k ₀ /k _n+1 )·V ₀ ) is calculated by multiplying the ratio of k ₀ and the ratio k _n+1 calculated this time by the voltage signal V ₀ (step S118). The control unit 22 that executes the process of step S116 for calculating the ratio k _n+1 of the leakage current Ig _n+1 and the total capacitance C _n+1 to ground corresponds to the “second ratio calculating means” in the present invention, and the ratio k. _n+1 is an example of an implementation configuration corresponding to the “second ratio” in the present invention. Further, the control unit 22 that executes the process of step S118 of calculating the correction voltage signal V _n+1 by multiplying the ratio of the reference ratio k ₀ and the ratio k _n+1 by the voltage signal V ₀ is the “voltage signal correction means” in the present invention. It is an example of the implementation structure corresponding to.

In this way, the voltage signal V ₀ is corrected by operating conditions (PC, cooling/heating equipment, lighting, etc.) of a load (for example, PC, cooling/heating equipment, processing device, lighting equipment, etc.) not shown connected to the downstream branch electric circuit 72. The on/off of the power supply of the equipment, the change of the operation mode of the equipment such as the processing device) is changed, and thus the ground capacitance Cp varies during the measurement of the ground capacitance Cp in the downstream branch electric path 72. Even if it occurs, the reference ratio k ₀ between the leakage current Ig circulated in the ground line L1 connected to the type-B grounding electrode EB and the total ground capacitance Ca is maintained at substantially the same value, and the downstream is maintained. This is so that the ground capacitance Cp in the side branch electric path 72 can be accurately measured.

When the correction voltage signal V _n+1 is calculated in this way, the CPU of the control unit 22 determines whether or not the reception of the power-on signal from the sub receiver 30 is maintained (step S120). That is, it is determined whether or not the measurement of the ground capacitance Cp in the downstream branch electric circuit 72 by the sub receiver 30 is being continued. When the measurement of the ground capacitance Cp in the downstream branch electric path 72 by the sub-receiver 30 is continuing, the value n is incremented by 1 (step S122), and the calculated correction voltage signal V _n+1 is signaled. The process returns to step S112 to apply to the ground line L1 connected to the type-B grounding electrode EB via the injection clamp 12, and thereafter, until the power-on signal is not received from the sub-receiver 30, that is, the sub-receiver 30. The steps from step S112 to step S122 are repeatedly executed until the measurement of the ground capacitance Cp in the downstream branch electric circuit 72 is stopped.

On the other hand, when the reception of the power-on signal is not maintained in step S120, that is, when the measurement of the ground capacitance Cp in the downstream branch electric path 72 by the sub-receiver 30 is stopped, the value n is set to 0. (Step S124), the process returns to step S100 and the above-described processing (steps S100 to S124) is repeatedly executed.

Next, the measurement of the ground capacitance Cp in the downstream branch electric path 72 by the sub-receiver 30 will be described. When the power of the sub-receiver 30 is turned on in order to start the measurement of the ground capacitance Cp in the downstream branch electric path 72, the ground capacitance calculation process is executed. When the electrostatic capacitance calculation process is executed, the CPU of the control unit 38 of the sub receiver 30 first transmits a power-on signal to the transmitter/main receiver 10 and also the transmitter/main receiver 10 concerned. The process of receiving the reference ratio k ₀ from is executed (step S200).

Subsequently, the shunt current Igp (shunt component of the leakage current Ig) flowing through the downstream branch electric path 72 is detected by the clamp sensor 32 (step S202), and based on the detected shunt current Igp and the received reference ratio k _0. The ground capacitance Cp of the downstream branch electric circuit 72 is calculated (step S204). The ground capacitance Cp can be obtained by dividing the detected shunt current Igp by the reference ratio k ₀ (Cp=Igp/k ₀ ). This is because the ratio of the leakage current Ig circulated to the ground line L1 connected to the type-B grounding electrode BE and the shunt current Igp measured in the downstream side branch circuit 72 is the total electrostatic capacitance to ground of the entire low voltage side circuit 70. It is based on the fact that it is equal to the ratio of the capacitance Ca to the electrostatic capacitance Cp of the downstream side branch circuit 72.

The calculated ground capacitance Cp is displayed on the display unit 42 (step S206), and the process returns to step 202 until the power of the sub receiver 30 is turned off, that is, the downstream branch electric circuit 72 by the sub receiver 30. The processing from step S202 to step 206 is repeatedly executed until the measurement of the ground capacitance Cp at is stopped.

According to the electrostatic capacitance measuring device 1 of the present invention according to the present embodiment described above, the leakage current Ig circulated in the ground line L1 connected to the B-type ground electrode BE and the downstream branch electric path 72 are measured. Paying attention to the fact that the ratio of the divided current Igp to the divided current Igp is equal to the ratio of the total electrostatic capacitance Ca of the entire low voltage side electric circuit 70 to the electrostatic capacitance Cp of the downstream branch electric circuit 72, Since the ground capacitance Cp is obtained by dividing by the reference ratio k ₀ which is the ratio of the leakage current Ig ₀ and the total ground capacitance Ca ₀ , the ground capacitance Cp can be easily calculated in a very short time. Cp can be measured. Moreover, since the voltage signal V ₀ to be applied is corrected so that the reference ratio k ₀ is always substantially the same value, the operating condition of the load connected to any of the downstream branch electric circuits 72 (operation of equipment) Even if a change occurs in the ground electrostatic capacitance Cp during the measurement of the ground electrostatic capacitance Cp in the downstream side branch electric circuit 72 due to a change in the mode or the ON/OFF of the cooling/heating equipment). It is possible to accurately measure the electrostatic capacitance Cp to the ground in the downstream branch electric circuit 72.

Further, according to the ground capacitance measuring apparatus 1 of the present invention according to the present embodiment, the frequency of the voltage signal V ₀ is selected from frequencies higher than the commercial frequency (50 Hz to 60 Hz), for example, 100 Hz to 500 Hz. Since the configuration is set as described above, the total parallel insulation resistance combined value R can be ignored, and the low voltage side electric circuit 70 can be replaced with a simple equivalent circuit. As a result, the calculation of the total ground capacitance Ca can be simplified, and the measurement time can be further shortened. Further, since the diameter of the iron core of the signal injection clamp 12 can be reduced, the device can be made compact and the cost can be reduced.

In the present embodiment, the frequency of the voltage signal V _{0 is set to} a frequency higher than the commercial frequency (50 Hz to 60 Hz), for example, 100 Hz to 500 Hz, but the frequency is not limited to this. For example, the frequency may be lower than 100 Hz or higher than 500 Hz. Further, the frequency may be lower than 50 Hz.

In the present embodiment, the signal injection clamp 12 is used to apply the voltage signal V output from the signal output unit 16 to the ground line L1 connected to the type B ground electrode EB, but the present invention is not limited to this. For example, instead of the signal injection clamp 12, the ground line L1 connected to the B type ground electrode EB and the ground line L2 connected to the D type ground electrode ED are connected by a cable or the like, and the signal output unit is connected to the cable or the like. The voltage signal V output from 16 may be directly applied.

The present embodiment shows an example of a mode for carrying out the present invention. Therefore, the present invention is not limited to the configuration of this embodiment. The correspondence relationship between each component of this embodiment and each component of the present invention is shown below.

1 Ground capacitance measurement device (ground capacitance measurement device)
10 Transmitter and main receiver (transmitter and main receiver)
12 signal injection clamp 14 clamp sensor 16 signal output section 18 filter 20 A/D converter 22 control unit (total ground capacitance calculating means, first ratio calculating means, determining means,
Total capacitance recalculation means, second ratio calculation means, voltage signal correction means 24 Operation unit 26 Display unit 28 Communication unit 30 Sub receiver (sub receiver)
32 clamp sensor 34 filter 36 A/D converter 38 control unit 40 operation unit 42 display unit 44 communication unit 52 parallel circuit unit 70 low voltage side electric line (low voltage side electric line)
72 Downstream branch circuit (downstream branch circuit)
80 electrical equipment (electrical equipment)
90 Power receiving transformer 90a Grounding wire 92 Power receiving transformer 92a Grounding wire Ca Total capacitance to ground (total capacitance to ground)
Cp capacitance to ground (capacitance to ground)
R Total parallel insulation resistance combined value Reb Class B ground resistance Red Class D ground resistance Re Series combined insulation resistance L1 Ground wire (class B ground wire)
L2 Ground wire EB Class B ground pole ED Class D ground pole V ₀ Voltage signal (voltage signal)
V _n+1 correction voltage signal (correction voltage signal)
Ig ₀ leakage current (leakage current)
k ₀ reference ratio (first ratio)
k _n+1 ratio (second ratio)

Claims (4)

A ground capacitance measuring device capable of measuring the total ground capacitance of the entire low-voltage side electric circuit of an electric facility and the ground capacitance of each of a plurality of downstream side branch electric circuits branched on the downstream side of the low-voltage side circuit. ,
The voltage signal having a frequency different from the commercial frequency is installed on the type B ground wire of the low-voltage side electric line, and the voltage B is applied to the type B ground line via the low-voltage side electric line and ground due to the voltage signal. A transmitter/main receiver configured to detect a leakage current circulating in the seed ground wire at predetermined time intervals;
A sub-receiver that is installed in any of the plurality of downstream branch circuits and is configured to be able to detect a shunt current that is a shunt component of the leakage current flowing through the downstream branch circuit,
Equipped with
The transmitter and main receiver are
Total ground capacitance calculating means for calculating the total ground capacitance based on the voltage signal and the detected leakage current;
A first ratio calculating means for calculating a first ratio which is a ratio of the leakage current used for the calculation and the total capacitance to ground;
Determination means for determining whether or not a predetermined condition is satisfied,
Total ground capacitance recalculation means for recalculating the total ground capacitance based on the leakage current and the voltage signal detected when the predetermined condition is satisfied,
The ratio of the leakage current used for recalculation and the recalculated total capacitance to ground
A second ratio calculating means for calculating a ratio,
Voltage signal correction means for correcting the applied voltage signal based on the ratio of the first ratio and the second ratio,
Equipped with
When the predetermined condition is satisfied, the voltage signal is converted into the voltage signal and the correction voltage signal corrected by the voltage signal correction unit is applied to the B-type ground line.
The sub-receiver is configured to calculate a ground capacitance of the downstream side branch circuit based on the detected shunt current and a ratio of the first ratio and the second ratio. Capacity measuring device. The ground capacitance measuring device according to claim 1, wherein the transmitter/main receiver is configured to apply, as the voltage signal, a high frequency voltage signal having a frequency higher than the commercial frequency to the class B ground line. .. A ground capacitance measuring method for measuring the total ground capacitance of the entire low-voltage side electric path of the electrical equipment and a plurality of downstream side branch electric paths branched on the downstream side of the low-voltage side electric path,
The voltage signal having a frequency different from the commercial frequency is installed on the type B ground wire of the low-voltage side electric line, and the voltage B is applied to the type B ground line via the low-voltage side electric line and ground due to the voltage signal. A transmitter/main receiver configured to detect a leakage current circulating in the seed ground wire at predetermined time intervals;
A sub-receiver that is installed in any of the plurality of downstream branch circuits and is configured to be able to detect a shunt current that is a shunt component of the leakage current flowing through the downstream branch circuit
Equipped with
(A) calculating the total capacitance to ground based on the voltage signal and the detected leakage current,
(B) calculating a first ratio, which is a ratio of the leakage current used for the calculation and the total capacitance to ground,
(C) It is determined whether or not a predetermined condition is satisfied,
(D) When the predetermined condition is satisfied, the total ground capacitance is recalculated based on the leak current and the voltage signal detected when the predetermined condition is satisfied, and used for recalculation. Calculating a second ratio which is the ratio of the leakage current and the recalculated total capacitance to ground;
(E) The applied voltage signal is corrected based on the ratio of the first ratio and the second ratio, and the corrected voltage signal converted into the voltage signal is applied to the type B ground line,
(F) A ground capacitance measuring method for calculating a ground capacitance of the downstream side branch circuit based on the shunt current detected by the sub-receiver and the ratio of the first ratio and the second ratio. .. The grounding capacitance measuring method according to claim 3, wherein the transmitter/main receiver is configured to apply, as the voltage signal, a high-frequency voltage signal having a frequency higher than the commercial frequency to the class B ground line. ..

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