JP6896158B2 - Leakage detector and earth leakage breaker - Google Patents

Description

The present invention relates to an earth leakage detection device and an earth leakage breaker for determining an earth leakage generated in an electric circuit.

Conventionally, the leakage breaker uses a zero-phase current transformer that detects the zero-phase current of the electric circuit, a voltage conversion circuit that converts the secondary current of the zero-phase current transformer into a voltage, and a high-frequency component of the converted voltage. It includes a low-pass filter to be removed and a leak-determining circuit that determines the leakage of the electric circuit based on the voltage output from the low-pass filter.

In this type of leakage circuit breaker, Patent Document 1 states that the withstand voltage of an electronic component arranged on the secondary side of a zero-phase current transformer is exceeded when a short-term overcurrent occurs sporadically due to a lightning surge or the like. A technique for providing a clamp circuit that limits the voltage between the secondary terminals of a zero-phase current transformer to a voltage equal to or lower than the clamp voltage is disclosed.

Japanese Unexamined Patent Publication No. 2006-148990

However, in the above-mentioned conventional technique, since the clamp circuit and the low-pass filter are connected in parallel, the maximum value of the voltage input to the leakage determination circuit via the low-pass filter is defined by the clamp voltage of the clamp circuit. Will be done. Since the clamp voltage is defined by the forward voltage of the diode constituting the clamp circuit, the clamp voltage cannot be lowered to a value smaller than the forward voltage of the diode. Therefore, even when a Schottky barrier diode having a low forward voltage is used, it is difficult to set the maximum value of the voltage input to the leakage determination circuit to, for example, 100 [mV]. As described above, in the above-mentioned conventional technique, the maximum value of the voltage input to the earth leakage determination circuit cannot be adjusted independently of the clamp voltage, so that the maximum value of the voltage input to the earth leakage determination circuit can be reduced. There is a problem that it is difficult to do.

The present invention has been made in view of the above, and an object of the present invention is to obtain an earth leakage detection device capable of adjusting the maximum value of the voltage input to the earth leakage determination circuit independently of the clamp voltage.

In order to solve the above-mentioned problems and achieve the object, the earth leakage detection device of the present invention includes a zero-phase current transformer, a clamp circuit, a voltage conversion circuit, a low-pass filter, and an earth leakage determination circuit. The zero-phase current transformer detects the zero-phase current flowing in the electric circuit. The clamp circuit limits the voltage between the secondary terminals of the zero-phase current transformer to below the clamp voltage. The voltage conversion circuit is connected in parallel with the clamp circuit and converts the output current of the zero-phase current transformer into a voltage. The low-pass filter removes the high-frequency component of the voltage converted by the voltage conversion circuit, and outputs the voltage from which the high-frequency component has been removed. The leakage determination circuit determines the leakage of the electric circuit based on the voltage output from the low-pass filter. The voltage conversion circuit has a series circuit of a voltage conversion element that converts the output current of the zero-phase transformer into a voltage and outputs the converted voltage to a low-pass filter, and an impedance adjustment element that adjusts the impedance of the voltage conversion circuit. ..

According to the present invention, the maximum value of the voltage input to the leakage determination circuit can be adjusted independently of the clamp voltage.

The figure which shows the structural example of the electric leakage circuit breaker which concerns on Embodiment 1 of this invention. The figure which shows an example of the relationship with the clamp voltage applied to Embodiment 1, the leakage determination threshold value, the voltage between secondary side terminals, and the voltage converted by a voltage conversion circuit. The figure for demonstrating the operation of the earth leakage detection part which concerns on Embodiment 1. The figure which shows the structural example of the electric leakage circuit breaker which concerns on Embodiment 2 of this invention.

Hereinafter, the earth leakage detection device and the earth leakage breaker according to the embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1.
FIG. 1 is a diagram showing a configuration example of a leakage circuit breaker according to a first embodiment of the present invention. As shown in FIG. 1, the earth leakage circuit breaker 1 according to the first embodiment has an earth leakage detection unit 3 for opening and closing an electric circuit 2, an earth leakage detection unit 4 for detecting an earth leakage current flowing through the electric circuit 2, and an earth leakage detection unit 4. When is detected, a trip device 5 for controlling the opening / closing unit 3 is provided. The earth leakage detection unit 4 is an example of an earth leakage detection device.

The opening / closing unit 3 has opening / closing contacts 3 ₁ and 3 ₂ for opening and closing the electric path 2. Each opening / closing contact 3 ₁ and 3 ₂ has a fixed contact (not shown) and a movable contact (not shown). In the switching contacts 3 ₁ by the fixed contact and the movable contact is in contact, with the power source side connection terminal ₆₁ and load side connecting terminal ₇₁ are electrically connected via a conductor 8 _1. Further, a fixed contact and the movable contact in the switching contact 3 ₂ By contacting, the power-side connector 6 ₂ and load side connecting terminal 7 ₂ are electrically connected via a conductor _82. As a result, a current flows through the electric circuit 2 and the leakage breaker 1 is turned on.

Each switching contact 3 _1, 3 ₂ opening of the switching contact 3 _1, 3 ₂ is performed by the fixed contact and the movable contact are separated at the power supply side connection terminals 6 _1, 6 ₂ and the load side connecting terminal 7 ₁ , 7 ₂ are electrically disconnected. As a result, the current in the electric circuit 2 is cut off, and the electric leakage breaker 1 is turned off. In the example shown in FIG. 1, in the electric circuit 2, one of the three phases of R phase, S phase, and T phase (not shown) is grounded, but any of the R phase, S phase, and T phase is grounded. May also be configured not to be grounded. In this case, the opening / closing portion 3 is provided with three opening / closing contacts.

The earth leakage detection unit 4 includes a zero-phase current transformer 10, a clamp circuit 20, a voltage conversion circuit 30, a low-pass filter 40, and an earth leakage determination circuit 50.

The zero-phase current transformer 10 detects the zero-phase current flowing in the electric circuit 2. Such zero-phase current transformer 10 includes an annular iron core 11 with the conductor _81, 82 is wound through or winding and a secondary winding 12 which is wound toroid 11 wound. Secondary side terminals 13 and 14 are provided at both ends of the secondary winding 12, and a current Iz indicating a detection result of a zero-phase current by the zero-phase current transformer 10 from the secondary side terminals 13 and 14 Is output. Hereinafter, the current Iz may be referred to as an output current Iz.

The clamp circuit 20 is connected between the secondary side terminals 13 and 14 of the zero-phase current transformer 10 and sets the voltage Vz between the secondary side terminals 13 and 14 to the clamp voltage Vlamp or less. In the example shown in FIG. 1, the clamp circuit 20 has two diodes 21 and 22 connected in antiparallel. As a result, the voltage Vz between the secondary terminals 13 and 14 is suppressed to be equal to or lower than the forward voltage of the diodes 21 and 22. In this way, the clamp circuit 20 operates with the forward voltage of the diodes 21 and 22 as the clamp voltage V clamp.

The voltage conversion circuit 30 includes a voltage conversion element 31 that converts the output current Iz of the zero-phase current transformer 10 into a voltage Vch, and an impedance adjustment element 32 that adjusts the impedance Z of the voltage conversion circuit 30. The voltage conversion element 31 and the impedance adjusting element 32 are connected in series. The series circuit of the voltage conversion element 31 and the impedance adjusting element 32 is connected in parallel to the clamp circuit 20. The voltage conversion circuit 30 will be described in detail later.

The low-pass filter 40 removes the high frequency component of the voltage Vch output from the voltage conversion circuit 30. The high frequency component of the voltage Vch is a frequency component higher than the frequency of the leakage current detected by the leakage detection unit 4. The cutoff frequency of the low-pass filter 40 is set to a frequency higher than the frequency of the leakage current so that the frequency component of the leakage current is not removed.

The leakage determination circuit 50 determines the leakage of the electric circuit 2 based on the voltage Vin output from the low-pass filter 40. Specifically, the earth leakage determination circuit 50 compares the instantaneous value of the voltage Vin output from the low-pass filter 40 with the earth leakage determination threshold value Vlake in a preset period T1. The earth leakage determination circuit 50 determines that an earth leakage has occurred in the electric circuit 2 when the instantaneous value of the voltage Vin continuously exceeds the earth leakage determination threshold value Vlake for a preset period T2, and determines that an earth leakage has occurred in the electric circuit 2 and causes an active level earth leakage to the trip device 5. Outputs the detection signal Threshold. The period T1 is, for example, 1 [ms], and the period T2 is, for example, 3 [ms].

When the electric leakage determination circuit 50 determines that an electric leakage has occurred in the electric circuit 2, the leakage detection signal Slake of the active level is torn off and output to the device 5. The active level earth leakage detection signal Slake is, for example, a high level signal.

When the leakage detection signal Slake of the active level is output from the leakage detection unit 4, the trip device 5 cuts off the electric circuit 2 by separating the fixed contact and the movable contact that are in contact with each other in the opening / closing unit 3. The earth leakage breaker 1 is turned off. The opening / closing unit 3 has an opening / closing mechanism (not shown) for moving the movable contact, and the tripping device 5 acts on the opening / closing mechanism to open the fixed contact and the movable contact in contact with each other. Can be done.

Further, the earth leakage determination circuit 50 determines that no earth leakage has occurred in the electric circuit 2 when the state in which the instantaneous value of the voltage Vin is equal to or more than the earth leakage determination threshold value Vleak does not continue for T2 or more for a preset period, and determines that the active level The leakage detection signal Slak is not output to the trip device 5. In this case, the fixed contact and the movable contact remain in contact with each other in the opening / closing unit 3, and the earth leakage breaker 1 is maintained in the ON state.

Next, the voltage conversion circuit 30 will be described in more detail. In the following, an overcurrent that occurs sporadically in a short period of time due to a lightning surge or the like may be referred to as a lightning surge current for convenience of explanation. As described above, the voltage conversion circuit 30 includes an impedance adjusting element 32 that adjusts the impedance Z of the voltage conversion circuit 30 in addition to the voltage conversion element 31 that converts the output current Iz of the zero-phase current transformer 10 into the voltage Vch. Have.

As the impedance Z of the voltage conversion circuit 30 becomes smaller, the voltage generated between the secondary terminals 13 and 14 due to the lightning surge current becomes smaller, so that the rate of being clamped by the clamp circuit 20 becomes smaller. If the rate of being clamped by the clamp circuit 20 becomes small, there is a high possibility that the leakage breaker 1 will malfunction due to the lightning surge current.

Therefore, in the leakage breaker 1, the impedance Z of the voltage conversion circuit 30 is adjusted by the impedance adjusting element 32 so that the voltage generated between the secondary terminals 13 and 14 due to the lightning surge current is clamped by the clamping circuit 20. There is.

Here, the impedance Z of the voltage conversion circuit 30 and the clamp voltage Vlamp of the clamp circuit 20 will be specifically described. The voltage conversion element 31 of the voltage conversion circuit 30 is a resistor having a resistance value Rf, and the impedance adjusting element 32 is a resistor having a resistance value Radj.

When the leakage detection unit 4 does not have the clamp circuit 20 and the impedance adjusting element 32, the voltage Vz between the secondary terminals 13 and 14 is represented by the following equation (1).
Vz = Iz × Rf ・ ・ ・ (1)

Further, when the leakage detection unit 4 does not have the clamp circuit 20 but has the impedance adjusting element 32, the voltage Vz between the secondary terminals 13 and 14 is represented by the following equation (2).
Vz = Iz × (Rf + Radj) ・ ・ ・ (2)

The impedance of the secondary winding 12 of the zero-phase current transformer 10 is negligibly small as compared with the impedance Z of the voltage conversion circuit 30. Therefore, the magnitude of the output current Iz of the zero-phase current transformer 10 does not substantially change even if the magnitude of the impedance Z of the voltage conversion circuit 30 changes.

Therefore, by providing the impedance adjusting element 32 in the voltage conversion circuit 30, a voltage of (Rf + Radj) / Rf times can be generated between the secondary terminals 13 and 14 as compared with the case where the impedance adjusting element 32 is not provided. As a result, the proportion of the component clamped by the clamp circuit 20 among the components generated on the secondary side of the zero-phase current transformer 10 due to the component of the lightning surge current can be increased.

The impedance Z of the voltage conversion circuit 30 is represented by the following formula (3), and the voltage Vch output from the voltage conversion circuit 30 to the low-pass filter 40 is represented by the following formula (4).
Z = Rf + Radj ・ ・ ・ (3)
Vch = Rf / (Rf + Radj) × Vz ・ ・ ・ (4)

Therefore, by appropriately adjusting the resistance value Radj of the impedance adjusting element 32 and the resistance value Rf of the voltage conversion element 31, the voltage Vch output from the voltage conversion circuit 30 can be made smaller than the clamp voltage Vclamp of the clamp circuit 20. Can be adjusted to the value of. For example, by setting the voltage Vch output to the low-pass filter 40 to 100 [mV] or less, the voltage Vin input to the leakage determination circuit 50 can be set to 100 [mV] or less. In this way, the earth leakage detection unit 4 can adjust the maximum value of the voltage Vin input to the earth leakage determination circuit 50 independently of the clamp voltage V clamp.

By the way, if the impedance Z of the voltage conversion circuit 30 is too large, the voltage Vz between the secondary terminals 13 and 14 generated by the minimum leakage current detected by the leakage detection unit 4 becomes larger than the clamp voltage Vlamp. , The leakage determination circuit 50 cannot determine the leakage. Therefore, the upper limit of the impedance Z of the voltage conversion circuit 30 is a voltage in which the voltage Vz between the secondary terminals 13 and 14 generated by the minimum leakage current detected by the leakage detection unit 4 is equal to or less than the clamp voltage Vlamp. Is a condition.

Here, when the peak value of the output current Iz of the secondary side terminals 13 and 14 generated by the minimum leakage current detected by the leakage detection unit 4 is Iz_trip, the clamp voltage Vclamp is calculated by the following equation (5). The condition is to meet. The minimum value leakage current is the lower limit value of the leakage current for detecting the leakage by the leakage detection unit 4, and when the leakage current flowing through the electric path 2 is equal to or more than the minimum leakage current, the leakage detection unit 4 causes the leakage. Detected.
Vclamp ≧ Iz_trip × (Rf + Radj) ・ ・ ・ (5)

Further, the earth leakage determination threshold value Vlake of the earth leakage determination circuit 50 must satisfy the following equation (6).
Vleak = Rf × Iz_trip ・ ・ ・ (6)

Therefore, the resistance value Radj of the impedance adjusting element 32 can be expressed by the following equation (7).
Radj ≤ (Vclamp-Vleak) / Iz_trip
... (7)

Since the leakage determination circuit 50 detects the leakage depending on whether or not the instantaneous value of the voltage Vin is equal to or higher than the leakage determination threshold value Vleak, it does not matter how much the instantaneous value of the voltage Vin exceeds the leakage determination threshold value Vleak. .. Therefore, the maximum value Radjmax of the resistance value Radj can be expressed by the following equation (8).
Radjmax = (Vclamp-Vleak) / Iz_trip ... (8)

Here, it is assumed that Vlamp = 1 [V], Vlake = 100 [mV], and Iz_trip = 200 [μA]. In this case, from the above equation (8), Radjmax = 4.5 [kΩ]. Further, from the above equation (6), Rf = 0.5 [kΩ].

FIG. 2 is a diagram showing an example of the relationship between the clamp voltage, the leakage determination threshold, the voltage between the secondary terminals, and the voltage converted by the voltage conversion circuit according to the first embodiment, and is shown by the leakage determination circuit 50. An example is shown in the case where the minimum value leakage current determined to have leaked is flowing in the electric circuit 2.

In the example shown in FIG. 2, the peak value of the voltage Vz between the secondary terminals 13 and 14 is the same as the clamp voltage Vlamp. The peak value of the voltage Vch output from the voltage conversion circuit 30 is the same as the leakage determination threshold value Vleak. Further, since the cutoff frequency of the low-pass filter 40 is set higher than the frequency of the leakage current, the peak value of the voltage Vin output from the low-pass filter 40 is the peak of the voltage Vch output from the voltage conversion circuit 30. Same as the value.

Therefore, during the period when the peak value of the voltage Vz between the secondary side terminals 13 and 14 is higher than the clamp voltage Vclamp, the peak value of the voltage Vin output from the low pass filter 40 becomes the same as the leakage determination threshold Vleak. Therefore, it is determined that the period in which the peak value of the voltage Vz between the secondary terminals 13 and 14 is higher than the clamp voltage Vlamp is the period T2 or more, and the earth leakage determination circuit 50 determines that an electric leakage has occurred in the electric circuit 2. Will be done.

Further, even when a lightning surge is applied to the electric circuit 2, the peak value of the voltage Vz between the secondary side terminals 13 and 14 is the same as the clamp voltage Vclamp, and the voltage Vch output from the voltage conversion circuit 30 The peak value becomes the same as the leakage determination threshold voltage. The voltage Vch output from the voltage conversion circuit 30 is input to the low-pass filter 40.

Since the cutoff frequency of the low-pass filter 40 is lower than the frequency of the lightning surge current, the low-pass filter 40 reduces the voltage component due to the lightning surge current. Therefore, the peak value of the voltage Vin output from the low-pass filter 40 is lower than the peak value of the voltage Vch output from the voltage conversion circuit 30, and the leakage determination circuit 50 determines that an electric leakage has occurred in the electric circuit 2. Not done. In this way, the leakage detection unit 4 can improve the S / N ratio (Signal-to-Noise Ratio), which is the ratio of the voltage components due to the lightning surge current to the voltage Vin.

FIG. 3 is a diagram for explaining the operation of the leakage detection unit according to the first embodiment, in which a lightning surge is applied to the electric circuit 2 in which a leakage current having a size not determined to have leaked by the leakage determination circuit 50 is flowing. Here is an example when it is done.

As shown in FIG. 3, when a lightning surge current is applied to the electric circuit 2 through which the leakage current is flowing, a current in which the component of the lightning surge current is superimposed on the leakage current flows in the electric circuit 2. At this time, the output current Iz of the waveform shown in FIG. 3 is output from the zero-phase current transformer 10.

A voltage is generated across the voltage conversion circuit 30 by the output current Iz of the zero-phase current transformer 10, and a voltage exceeding the clamp voltage V clamp of the clamp circuit 20 is clamped by the clamp circuit 20. Therefore, the voltage Vz between the secondary terminals 13 and 14 has the waveform shown in FIG.

The voltage conversion circuit 30 outputs the voltage Vch, which is the voltage of the voltage conversion element 31 generated by the output current Iz, to the low-pass filter 40. Since the low-pass filter 40 removes high-frequency components from the voltage Vch output from the voltage conversion circuit 30, the voltage Vin of the waveform shown in FIG. 3 is input from the low-pass filter 40 to the leakage determination circuit 50.

In the example shown in FIG. 3, since the voltage Vin output from the low-pass filter 40 is less than the leakage determination threshold value Vleak, the leakage determination circuit 50 does not determine that there is an leakage. As described above, when the lightning surge current is applied to the electric circuit 2, the electric leakage determination circuit 50 does not determine that there is an electric leakage and does not malfunction due to the lightning surge current of the electric circuit 2.

As described above, the earth leakage detection unit 4 of the earth leakage circuit breaker 1 according to the first embodiment includes a zero-phase current transformer 10, a clamp circuit 20, a voltage conversion circuit 30, a low-pass filter 40, and an earth leakage determination circuit 50. And. The zero-phase current transformer 10 detects the zero-phase current flowing in the electric circuit 2. The clamp circuit 20 limits the voltage Vz between the secondary terminals 13 and 14 of the zero-phase current transformer 10 to the clamp voltage Vlamp or less. The voltage conversion circuit 30 is connected in parallel to the clamp circuit 20 and converts the output current Iz of the zero-phase current transformer 10 into a voltage Vch. The low-pass filter 40 removes the high-frequency component of the voltage Vch converted by the voltage conversion circuit 30, and outputs the voltage Vin from which the high-frequency component is removed from the voltage Vch. The leakage determination circuit 50 determines the leakage of the electric circuit 2 based on the voltage Vin output from the low-pass filter 40. The voltage conversion circuit 30 is a voltage conversion element 31 that converts the output current Iz of the zero-phase current transformer 10 into a voltage Vch and outputs the converted voltage Vch to the low-pass filter 40, and an impedance that adjusts the impedance of the voltage conversion circuit 30. It has a series circuit with the adjusting element 32.

As a result, the voltage Vin input to the leakage determination circuit 50 can be adjusted independently of the clamp voltage Vlamp of the clamp circuit 20. Therefore, for example, even when the earth leakage determination threshold voltage Vlake of the earth leakage determination circuit 50 is lower than the clamp voltage Vclamp, it is possible to prevent the earth leakage determination circuit 50 from malfunctioning due to a single overcurrent such as a lightning surge current. .. For example, when the diodes 21 and 22 of the clamp circuit 20 are general diodes, the clamp voltage Vlamp is 0.7 to 1 [V]. If the diodes 21 and 22 are Schottky barrier diodes, the clamp voltage Vlamp is, for example, 0.3 [V]. Therefore, it is difficult to set the clamp voltage Vlamp to 100 [mV], and if the impedance adjusting element 32 is not provided, the voltage Vin input to the leakage determination circuit 50 due to the lightning surge current exceeds 100 [mV]. At this time, if the earth leakage determination threshold Vlake of the earth leakage determination circuit 50 is 100 [mV], the earth leakage determination circuit 50 erroneously detects the lightning surge current as the earth leakage current. On the other hand, since the earth leakage detection unit 4 of the earth leakage breaker 1 according to the first embodiment has the earth leakage adjusting element 32, the earth leakage determination threshold of the earth leakage determination circuit 50 does not need to adjust the clamp voltage Vlamp itself. The maximum value of the voltage Vin input to the leakage determination circuit 50 can be easily adjusted according to the Leak. Therefore, the earth leakage detection unit 4 can prevent erroneous detection even if the earth leakage determination threshold value Vlake is, for example, 100 [mV].

Further, the impedance adjusting element 32 includes a resistor. Thereby, the voltage Vch output from the voltage conversion circuit 30 can be adjusted without depending on the frequency. Therefore, the voltage conversion circuit 30 can be adjusted without considering the frequency.

Further, the electric leakage determination circuit 50 determines that there is an electric leakage in the electric path 2 when the instantaneous value of the voltage Vin output from the low pass filter 40 continues to be T2 or more for a preset period in which the electric leakage determination threshold is Vleak or more. To do. As a result, for example, the leakage generated in the electric circuit 2 can be detected at a higher speed than the case where the electric leakage in the electric circuit 2 is detected when the voltage Vin output from the low-pass filter 40 exceeds both the positive threshold value and the negative threshold value. It is possible to detect.

Embodiment 2.
In the first embodiment, the impedance adjusting element is composed of a resistor, but in the second embodiment, the impedance adjusting element is composed of an inductor, which is different from the first embodiment. In the following, components having the same functions as those of the first embodiment will be designated by the same reference numerals and description thereof will be omitted, and the differences from the earth leakage breaker 1 of the first embodiment will be mainly described.

FIG. 4 is a diagram showing a configuration example of the leakage breaker according to the second embodiment of the present invention. As shown in FIG. 4, the earth leakage breaker 1A according to the second embodiment includes an opening / closing unit 3, an earth leakage detection unit 4A, and a tripping device 5. The earth leakage detection unit 4A includes a zero-phase current transformer 10, a clamp circuit 20, a voltage conversion circuit 30A, a low-pass filter 40, and an earth leakage determination circuit 50.

The voltage conversion circuit 30A includes a voltage conversion element 31 and an impedance adjusting element 32A. The voltage conversion element 31 is a resistor having a resistance value Rf, and the impedance adjusting element 32A is an inductor having an inductance value L.

The impedance Z of the voltage conversion circuit 30A is represented by the following formula (10), and the voltage Vch output from the voltage conversion circuit 30A is represented by the following formula (11).
Z = √ {Rf ² + (ωL) ² } ... (10)
Vch = Rf / √ {Rf ² + (ωL) ² } × Vz ・ ・ ・ (11)

Therefore, by appropriately adjusting the inductance value L of the impedance adjusting element 32A and the resistance value Rf of the voltage conversion element 31, the voltage Vch output from the voltage conversion circuit 30A is smaller than the clamp voltage Vclamp of the clamp circuit 20. It can be adjusted to any value. For example, the voltage Vin input to the leakage determination circuit 50 can be set to a small value such that it is 100 mV or less.

Further, when the peak value of the output current Iz of the secondary side terminals 13 and 14 generated by the minimum leakage current detected by the leakage detection unit 4A is Iz_trip, the clamp voltage Vclamp satisfies the following equation (12). Is a condition.
Vclamp ≧ Iz_trip × √ {Rf ² + (ωL) ² }
... (12)

Further, the earth leakage determination threshold value Vlake of the earth leakage determination circuit 50 must satisfy the following equation (13).
Vleak ≧ Rf × Iz_trip ・ ・ ・ (13)

Therefore, the inductance value L of the impedance adjusting element 32A is represented by the following equation (14).
L ≤ √ (Vclamp ² / Iz_trip ^{2- Rf 2} ) / ω
... (14)

Since the earth leakage determination circuit 50 detects the earth leakage depending on whether or not the instantaneous value of the voltage Vin is equal to or more than the earth leakage determination threshold value Vleak, the value of the voltage exceeding the earth leakage determination threshold value Vleak is not used for the processing. Therefore, the maximum value Lmax of the inductance value L is expressed by the following equation (15).
Lmax = √ (Vlamp ² / Iz_trip ^{2- Rf 2} ) / ω
... (15)

Here, it is assumed that Vlamp = 1 [V], Iz_trip = 200 [μA], ω = 2πf, f = 50 [Hz], and Rf = 500 [Ω]. In this case, from the above equation (15), Lmax = 15.8 [H].

Since the frequency of the lightning surge current is higher than the frequency of the leakage current, “ω” in the above equation (15) can be set to a frequency higher than the frequency of the leakage current. For example, when the frequency of the lightning surge current is known, "ω" in the above equation (15) can be used as the frequency of the lightning surge current. For example, when the frequency of the lightning surge current is 100 [kHz], Lmax = 7.9 [mH] can be obtained by setting ω = 100 [kHz] in the above equation (15). Thereby, for example, the voltage Vin input to the leakage determination circuit 50 can be limited in the frequency band of the high frequency component of the output current Iz and lower than the cutoff frequency of the low-pass filter 40.

In the earth leakage detection unit 4A of the earth leakage breaker 1A according to the second embodiment, the impedance adjusting element 32A includes an inductor. As a result, the impedance of the impedance adjusting element 32A when the lightning surge current flows through the electric circuit 2 is larger than the impedance of the impedance adjusting element 32A when the leakage current flows through the electric circuit 2. Therefore, the voltage Vin input to the earth leakage determination circuit 50 when a lightning surge current flows through the electric circuit 2 can be made significantly smaller than the earth leakage determination threshold Vleak, and erroneous detection in the earth leakage determination circuit 50 can be accurately suppressed. be able to.

Capacitance elements may be connected in parallel or in series to the impedance adjusting elements 32 and 32A according to the first and second embodiments. As a result, when a high-frequency current such as a lightning surge current flows through the electric circuit 2, the voltage Vin input to the electric leakage determination circuit 50 can be made smaller than when the electric leakage current flows through the electric circuit 2. Further, the voltage conversion element 31 of the first embodiment is composed of a resistor, but the voltage conversion element 31 may be composed of an element in which a resistor and an inductor are connected in series. Further, the adjustment of the impedance adjusting elements 32 and 32A described above is an example, and the adjustment of the impedance adjusting elements 32 and 32A is not limited to the above example.

The configuration shown in the above-described embodiment shows an example of the content of the present invention, can be combined with another known technique, and is one of the configurations without departing from the gist of the present invention. It is also possible to omit or change the part. The earth leakage detection units 4 and 4A can be applied to equipment or devices other than the earth leakage breakers 1 and 1A. For example, the earth leakage detection units 4 and 4A can be applied to an earth leakage monitoring device, an earth leakage relay, and other measuring instruments.

1,1A earth leakage breaker, 2 electric circuit, 3 opening / closing part, 3 ₁ , 3 ₂ opening / closing contact, 4, 4A earth leakage detector, 5 tripping device, 6 ₁ , 6 ₂ power supply side connection terminal, 7 ₁ , 7 ₂ load Side connection terminals, 8 ₁ , 8 ₂ conductors, 10 zero-phase earth faults, 11 annular cores, 12 secondary windings, 13, 14 secondary side terminals, 20 clamp circuits, 21 and 22 diodes, 30, 30A voltage conversion Circuit, 31 voltage conversion element, 32, 32A impedance adjustment element, 40 low pass filter, 50 earth leakage judgment circuit, Iz output current, Vch, Vin, Vz voltage, Vleak earth leakage judgment threshold, T2 period.

Claims (5)

A zero-phase current transformer that detects the zero-phase current flowing in the electric circuit,
A clamp circuit that limits the voltage between the secondary terminals of the zero-phase current transformer to the clamp voltage or less, and
A voltage conversion circuit that is connected in parallel to the clamp circuit and converts the output current of the zero-phase current transformer into a voltage.
A low-pass filter that removes the high-frequency component of the voltage converted by the voltage conversion circuit and outputs the voltage from which the high-frequency component has been removed.
A leakage determination circuit for determining an leakage in the electric circuit based on the voltage output from the low-pass filter is provided.
The voltage conversion circuit
It has a series circuit of a voltage conversion element that converts the output current of the zero-phase current transformer into the voltage and outputs the converted voltage to the low-pass filter, and an impedance adjusting element that adjusts the impedance of the voltage conversion circuit. An earth leakage detection device characterized by this. The impedance adjusting element is
The leakage detection device according to claim 1, further comprising a resistor. The impedance adjusting element is
The leakage detection device according to claim 1, further comprising an inductor. The earth leakage determination circuit is
Claims 1 to 3, wherein it is determined that there is an electric leakage in the electric circuit when the state in which the instantaneous value of the voltage output from the low-pass filter is equal to or higher than the threshold value continues for a preset period or longer. The leakage detection device according to any one. The earth leakage detection device according to any one of claims 1 to 4.
An opening / closing part that opens / closes the electric circuit and
A leakage circuit breaker comprising: a tripping device that cuts off the electric circuit at the opening / closing portion when the electric leakage determination circuit determines that there is an electric leakage in the electric circuit.

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