JP2007220382A - Ground fault interrupter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance reliability of a testing action by improving a filter circuit of an operational amplifier booster provided on a secondary output side of a zero-phase current transformer for a ground fault interrupter with a leakage test circuit. <P>SOLUTION: The ground fault interrupter comprises a zero-phase current transformer 3 for detecting a leakage current of a polyphase alternating current path 1, a leakage detection circuit 4, a tripping device 5 for opening a contact of an AC electric path by an output signal of the leakage detection circuit, a testing circuit 6 for supplying the zero-phase current tranfsormer 3 with a testing current It for simulating leakage by switching on a testing switch 6a and a power supply circuit 9 for supplying the testing circuit and the amplifying means with electricity. In the ground fault interrupter, an amplifying means 10 using an operation amplifier as an amplifying element, and a leakage sensitivity setting device 11 for selecting a rated sensitivity current of the ground fault interrupter and an amplifying degree setting device 12 for the amplifying means 10 are provided between a secondary side of the zero-phase current transformer and the leakage detection circuit. The secondary output current Is supplied from the zero-phase current transformer 3 to the leakage detection circuit 4 is amplified to an amplifying degree corresponding to setting of the leakage sensitivity setting device 11 by switching on the test switch 6a. Thus, a leakage test can be appropriately conducted without affected by leakage sensitivity setting. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a leakage breaker that detects a leakage occurring in a distribution system and prevents a leakage accident in advance, and more particularly relates to a leakage breaker including a test circuit that confirms the operation of a leakage trip function.

  As is well known, the earth leakage breaker is provided with a test circuit for confirming the operation of the earth leakage trip function (see, for example, Patent Document 1), and a conventional configuration circuit diagram thereof is shown in FIG.

  In FIG. 4, 1 is a three-phase AC circuit, 2 is a main circuit switching contact that opens and closes the AC circuit 1, 3 is a zero-phase current transformer that detects the leakage current of the AC circuit using the AC circuit 1 as a primary winding, A leakage detection circuit that determines whether or not leakage has occurred in the AC circuit 1 from the output current of the leakage current detection winding (secondary winding) 3a of the zero-phase current transformer 3, and outputs a trip signal when the leakage is detected. 5 is a trip coil (tripping means) for opening the switching contact 2 by an output signal of the leakage detection circuit 4, 6 is a test circuit for checking the operation of the leakage trip function, 7 is an AC power source, and 8 is an AC circuit 1 Reference numeral 9 denotes a power supply circuit that rectifies the interphase voltage of the AC circuit 1 and supplies power to the leakage detection circuit 4.

  Here, the test circuit 6 comprises a current limiting resistor 6a for adjusting the magnitude of the test current flowing through the circuit and a push button type test switch 6b, and is wound around the secondary side of the zero-phase current transformer 3. It is connected between the two phases of the AC circuit 1 through a test winding 3b that is electromagnetically coupled to the leakage current detection winding 3a. The leakage detection circuit 4 supplies power via a power circuit (rectifier circuit) 9 connected between the two phases of the three-phase AC circuit 1.

  With the above configuration, if a leakage (ground fault, leakage current) occurs on the load side of the AC circuit 1 and an unbalanced current flows in the primary circuit of the zero-phase current transformer 3, the leakage current becomes a zero-phase current. The secondary output is input to the leakage detection circuit 4 from the leakage current detection winding 3a. When the leakage current detected by the leakage detection circuit 4 exceeds a preset threshold value (threshold value corresponding to the rated sensitivity current), the leakage detection circuit 4 generates an output signal and supplies it to the trip coil 5, based on this. It is well known that the trip coil 5 trips the switching mechanism to open the main circuit switching contact 2 and interrupts the AC circuit 1 to protect the load 8 and the like from leakage.

  Further, when performing an operation test of the earth leakage breaker function, the push button type test switch 6b of the test circuit 6 is turned on while the main circuit switching contact 2 is ON, and the AC circuit 1 is connected via the current limiting resistor 6a. A test current (simulated leakage current) It that simulates leakage is supplied to the test winding 3b wound around the zero-phase current transformer 3. As a result, a secondary output is generated in the zero-phase current transformer 3 in the same manner as when a leakage current flows in the AC circuit 1, and an output current Is is supplied from the leakage current detection winding 3a to the leakage detection circuit 4, Based on this, the leakage detection circuit 4 outputs a trip signal, trips the main circuit switching contact 2 and interrupts the AC circuit 1. This test makes it possible to check whether the functions of the tripping mechanism including the zero-phase current transformer 3, the leakage detection circuit 4, and the trip coil 5 operate normally.

  On the other hand, the above earth leakage breaker tends to require a more advanced protection function, and the international standard (IEC) requires the earth leakage breaker to have a function corresponding to an open phase protection. In this regard, in the leakage breaker having the conventional configuration shown in FIG. 4, if the three-phase AC circuit 1 is in a steady state, the leakage break test can be performed normally. If the phase to which the leakage detection circuit 4 is connected is open, or if a leakage current with a low phase opposite to the rated sensitivity current is generated, the leakage test cannot be performed normally. .

  Therefore, the inventors have adopted a power supply circuit that receives power from all phases of the three-phase AC circuit as a power supply for the test circuit and the leakage detection circuit as a countermeasure, and the test circuit has a test current having a frequency different from the commercial frequency. Japanese Patent Application No. 2005-121052 previously proposed an earth leakage circuit breaker that provides an oscillation circuit that achieves the above-mentioned characteristics so that a leakage test can be performed properly even when a leakage current of a phase loss or lower than the rated sensitivity current occurs in the AC circuit. Next, the circuit configuration and function will be described with reference to FIGS.

  That is, in the circuit configuration shown in FIGS. 5 and 6, the power supply circuit 9 includes a three-phase full-wave rectifier circuit 9a connected to all phases of the AC circuit 1, a constant voltage power supply circuit 9b, and a smoothing capacitor (capacitor) 9c. Power is supplied to the leakage detection circuit 4 and the test circuit 6 through the power supply circuit 9. The test circuit 6 combines a push button type test switch 6a and an oscillation circuit 6b, and generates a test current It in a frequency band different from the commercial frequency (50 Hz or 60 Hz) in the oscillation circuit 6b during a test operation. The test is performed by supplying the test winding 3 b of the phase current transformer 3.

By adopting the power supply circuit 9 and the test circuit 6 having the above-described configuration, even when one phase of the three-phase AC circuit 1 is lost, or in a state where a minute leakage current less than the rated sensitivity current is generated in the AC circuit 1 The leakage test can be performed normally.
Japanese Patent Laying-Open No. 2003-45312 (FIG. 1)

  The proposed earth leakage circuit breaker (FIGS. 5 and 6) improves the reliability of the earth leakage test operation as compared to the conventional earth leakage circuit breaker shown in FIG. Issues to be solved remain.

  That is, a general earth leakage breaker is connected to the secondary output circuit of the zero-phase current transformer 3 so that the rated sensitivity current can be selected and set according to the protection purpose on the user side, the protective earth resistance of the distribution system, etc. A sensitivity setting unit that switches the detection resistance value according to the setting of the rated sensitivity current is provided.

  By the way, during the test operation of the earth leakage circuit breaker, the sensitivity setting set on the secondary side of the zero-phase current transformer 3 through the test circuit 6 (generally, there is a difference of about 10 times between the minimum sensitivity current and the maximum sensitivity current). ) Must be supplied to the test winding 6b. However, in the circuit configuration shown in FIGS. 5 and 6, the test current It is limited to a substantially constant value by the power supply capacity of the power supply circuit 9. For this reason, when the leakage detection test is performed with the leakage detection sensitivity set on the secondary side of the zero-phase current transformer 3 set to the lowest sensitivity, for example, from the secondary side of the zero-phase current transformer 3 There is a possibility that the output current Is supplied to the leakage detection circuit 4 is too small and does not exceed the threshold set by the leakage detection circuit 4 so that the leakage test function does not operate normally.

  In addition, with regard to the above power supply circuit, a surge absorber such as a varistor is provided on the input side as a means for preventing malfunction due to surges entering from the outside and destruction of circuit elements in the conventional circuit so as to increase surge resistance. However, for example, if a 1000V class varistor is provided in each phase power supply line, the occupied space becomes large, the leakage circuit breaker becomes larger, and there is a problem that the cost of parts also increases.

  The present invention has been made in view of the above points. The object of the present invention is based on the previously proposed circuit configuration shown in FIGS. 5 and 6, and the secondary side output circuit of the zero-phase current transformer, and the power source. An object of the present invention is to provide an earth leakage circuit breaker which improves the reliability of the earth leakage test by reducing the circuit and improves the reliability of the earth leakage test, and reduces the size and cost of components.

To achieve the above object, according to the present invention, a switching contact that opens and closes a multiphase AC circuit, a zero-phase current transformer that detects a leakage current of the AC circuit, and a secondary output of the zero-phase current transformer A leakage detection circuit for determining whether or not the AC circuit has a leakage, and outputting a signal when a leakage occurs, a tripping means for receiving the output signal of the leakage detection circuit and opening the switching contact, and a test switch A leakage circuit breaker equipped with a test circuit that supplies a simulated leakage current to a test winding wound around a zero-phase current transformer by turning ON the power supply, and a power supply circuit that supplies power to the leakage detection circuit and test circuit from the AC circuit The power supply circuit is a constant voltage power supply circuit that rectifies all phases of the AC circuit and converts it into DC, and the test circuit that uses the power supply circuit as a power supply sets the frequency of the simulated leakage current to a frequency different from the commercial frequency. Equipped with oscillation circuit to set In things,
An earth leakage sensitivity setting device that selectively sets the earth leakage detection sensitivity between the secondary side of the zero phase current transformer and the earth leakage detection circuit, and the earth leakage from the zero phase current transformer when the test switch is turned on using the power supply circuit as a power source. Amplifying means for controlling the secondary output current supplied to the detection circuit with an amplification degree corresponding to the setting of the leakage sensitivity setting device is provided (Claim 1). Here, the amplifying means and the power supply circuit are concretely provided. It shall be comprised in the following aspects.
(1) The amplifying means is an amplifier in which an OP amplifier is used as an amplifying element, and an amplification degree setting means that variably adjusts the amplification degree corresponding to the setting of the leakage sensitivity setting device is combined.
(2) Further, a passive filter element is added to the OP amplifier to constitute an active filter for noise cut.
(3) Further, in order to improve the surge withstand capability for the power circuit, an input resistor for surge attenuation is connected to all phases of the power line connecting the AC circuit and the power circuit. And a time constant that is the product of the smoothing capacitor of the power supply circuit is set to 0.001 or more.

According to said structure, there exists the following effect. That is,
(1) On the secondary output side of the zero-phase current transformer, an earth leakage sensitivity setting device that selectively sets the leakage detection sensitivity, and from the zero-phase current transformer to the leakage detection circuit when the test switch is turned on using the power supply circuit as a power source By providing amplification means that variably controls the secondary output current to be supplied with an amplification degree corresponding to the setting of the leakage sensitivity setting device, the leakage detection sensitivity of the leakage breaker is selected and used, for example, as the lowest sensitivity. Even when there is a leakage test, the secondary output of the zero-phase current transformer is amplified to an amplification level corresponding to the sensitivity setting and is input to the subsequent leakage detection circuit. Can be output. Thereby, regardless of the selection of the rated sensitivity current selected on the user side, the earth leakage circuit breaker can be tested normally and the reliability is improved.
(2) Here, the amplification means is an amplifier having an OP amplifier as an amplification element, and an active filter (low-pass filter) is formed by adding a passive filter element to the OP amplifier, thereby generating an active element in the circuit. This suppresses the superimposed noise from being superimposed on the output of the OP amplifier, prevents the influence of the amplification means additionally provided in the circuit on the leakage detection function, and ensures high reliability.
(3) Also, as a countermeasure for reducing surges in the power supply circuit, connect an input resistor for surge attenuation to all phases of the power supply line connecting the AC circuit and the power supply circuit, and connect it to the subsequent stage of the rectifier circuit of the power supply circuit. By constructing a surge filter in combination with a capacitor, an ingress surge can be effectively attenuated using small and inexpensive components, and the time constant between the input resistor and the smoothing capacitor is 0.001. By setting as described above, a surge resistance with high reliability can be secured practically.

  Hereinafter, embodiments of the present invention will be described based on the illustrated examples. In the drawing of the embodiment, members corresponding to those in FIG. 4 and FIG.

  First, FIG. 1 and FIG. 2 show a circuit of an earth leakage circuit breaker according to the first embodiment of the present invention. 1 is a main circuit diagram of the earth leakage circuit breaker, and FIG. 2 is a circuit diagram of the amplifying means provided on the secondary output side of the zero-phase current transformer in FIG.

  That is, in the circuit configuration of the illustrated embodiment, the secondary side output circuit of the zero-phase current transformer 3 is newly equipped with an amplifying means 10, an sensitivity setting unit 11, and an amplification degree setting unit 12 using an OP amplifier as an amplification element, When performing the leakage test, the amplification degree (gain) of the amplification means 10 is variably adjusted to the amplification degree corresponding to the sensitivity setting selected by the sensitivity setting device 11 (selecting and setting the rated sensitivity current of the leakage breaker). The output current Is output from the leakage detection winding 3a of the zero-phase current transformer 3 when the test switch 6a is turned on is supplied to the subsequent leakage detection circuit 4 via an OP amplifier described later.

  Here, the amplifying means 10 includes an analog switch 10b as a non-inverting amplifier in which an operational amplifier (low-pass filter) is formed by externally connecting resistors R1 to R6 and a capacitor C1 with the OP amplifier 10a as an amplifying element. The analog switch 10b that performs switching operation in response to a control signal output from an amplification setter described later at the time of testing selects the input resistors R2 to R5, and determines the amplification degree based on this. In addition, in order to prevent noise in a higher frequency band than the frequency of the test current from being superimposed on the output of the OP amplifier 10a, parameters of the capacitor C1 and the resistor R1 connected to the feedback circuit of the OP amplifier 10a are appropriately set. To do.

  On the other hand, the sensitivity setting device 11 connects a resistor 11b having a different resistance value to each contact of the changeover switch 11a, and a detection resistor 13 in which the resistor 11b selected by the changeover switch 11a is connected to the secondary output side of the zero-phase current transformer 3. In combination with, the leakage detection sensitivity of the leakage breaker is switched. The amplification setter 12 combines resistors R7 to R9 and capacitors C2 to C4 with the changeover switch 12a and inputs the output signal to the control signal port of the analog switch 10b. A two-circuit four-contact switch is configured mechanically connected to the change-over switch 11a of the setting device 11.

  In addition, the analog switch 10b and the amplification degree setting unit 12 of the amplifying means 10 and the output terminal of the test switch 6a disposed in the test circuit 6 are connected by wiring so that the analog switch 10b is activated when the test switch 6a is turned on. In addition, the amplification degree setting device 12 is connected to a power source.

  On the other hand, in the power supply circuit 9 (see FIG. 1) of the illustrated embodiment, an input resistor 14 is connected to each phase of the AC circuit 1 as means for increasing the surge resistance, and the input resistor 14 and the smoothing capacitor 9c of the power supply circuit 9 are connected. Constitutes a surge filter for the power line. Further, in order to secure a sufficient surge attenuation effect with this surge filter, a resistance of several tens of KΩ is used for the input resistor 14 so that the time constant between the input resistor 14 and the capacitor 9c is 0.001 or more. It is good to set.

Next, the basic operation at the time of a leakage test with the above circuit configuration will be described.
(1) When test switch is OFF:
In this state, the oscillation circuit 6b is stopped, the analog switch 10b of the amplification means 10 is inactive, each contact thereof is OFF, the amplification degree setting device 12 is OFF, and the OP amplifier 10a functions as a buffer. Yes.
(2) When test switch is ON:
When the test switch 6a is turned ON, a test current It having a frequency different from the commercial frequency is supplied to the test winding 3b of the zero-phase current transformer 3 through the oscillation circuit 6b, and the analog switch 10b of the amplification means 10 is in an active state. , The amplification degree setting device 12 is turned on. The changeover switch 12a of the amplification degree setting device 12 is linked to the changeover switch 11a of the sensitivity setting device 11, and the control signal output from the amplification degree setting device 12 is amplified in response to the sensitivity setting in the sensitivity setting device 11. The signal is inputted to the control signal port of the analog switch 10b of the means 10, and each contact of the analog switch 10b is turned ON / OFF according to this signal, and the input resistances R2 to R5 of the OP amplifier 10a corresponding to this ON / OFF pattern. Is selected. As for the control signal port of the analog switch 10b pulled up by the resistors R7 to R9, the selected port is at the L level and the other ports are at the H level. As a result, the OP amplifier has an equivalent resistance obtained by adding R6 to a resistor (Rx) selected from R2 to R5 corresponding to the contact ON / OFF pattern of the analog switch 10b and a resistor R1 (feedback resistor). The amplification degree A (A = 1 + R1 / (Rx + R6)) is variably adjusted according to the ratio.

  That is, at the time of the leakage test, the secondary output of the zero-phase current transformer 3 by the test current It is amplified to an amplification degree corresponding to the sensitivity setting in the sensitivity setting unit 11 and input to the subsequent leakage detection circuit 4. become. Therefore, even when the leakage detection sensitivity of the leakage breaker is selected by using the lowest sensitivity, for example, the secondary output current Is of the zero-phase current transformer 3 input to the leakage detection circuit 4 during the test is the leakage detection circuit. Therefore, the trip signal is output to the tripping device (trip coil 5 in FIG. 4), and the test can be properly performed. Further, by providing the operational amplifier function to the operational amplifier of the amplification means, it is possible to prevent noise generated in the active element in the circuit from being superimposed on the output of the operational amplifier and maintain high leakage detection characteristics.

  Furthermore, by combining the power supply circuit 9 (see FIG. 1) with the earth leakage breaker, the reliability of the test operation performed in a state where a three-phase AC circuit 1 is open and low-level leakage current is generated is improved. Furthermore, higher surge resistance can be secured.

  Next, a second embodiment having a circuit configuration different from that of the first embodiment will be described with reference to FIG.

  That is, in this embodiment, the amplifying means 10 uses an operational amplifier (multiple feedback type low-pass filter) that uses the OP amplifier 10a as an inverting amplifier and externally attaches resistors R1 to R3 and a capacitor C to cut noise. Further, on the inverting terminal side, an analog switch for selecting any of the resistors R4 to R6 for adjusting the amplification degree and the resistors R4 to R6 corresponding to the sensitivity setting in the sensitivity setting unit 11 in parallel with the resistor R1. 10b is combined.

Next, the operation at the time of a leakage test with the above circuit configuration will be described.
(1) When test switch is OFF:
In this state, the oscillation circuit 6b is stopped, the analog switch 10b of the amplification means 10 is inactive, the input resistors R4 to R6 are not connected to the circuit, and the amplification degree (voltage gain) A of the amplifier is A = R2 / R1.
(2) When test switch is ON:
When the test switch 6a is turned on, the test current It is supplied to the test winding 3b of the zero-phase current transformer 3 via the oscillation circuit 6b, and the analog switch 10b of the amplifying means 10 becomes active, and at the same time, the leakage sensitivity setting device In response to the sensitivity setting at 11, a resistor selected from the input resistors R4 to R6 is connected in parallel with the resistor R1. As a result, the amplification factor A (pass gain of the filter circuit) of the amplifier (OP amplifier) is A = R2 × (R1 + Rx) / R1 × Rx, where Rx is the selected resistance. Here, by appropriately determining the resistances R4 to R6 in accordance with the setting of the leakage sensitivity, the leakage detection sensitivity of the leakage breaker is detected during the test even in the usage state where the lowest sensitivity is selected, for example. The secondary output current Is of the zero-phase current transformer 3 that is input to the circuit 4 is amplified to a value that exceeds a preset threshold value by the leakage detection circuit, and thereby a trip signal is sent to the trip device (trip coil 5 in FIG. 4). You can output and test properly. Further, by providing the function of the active low-pass filter in the amplifier circuit of the OP amplifier, the noise (higher frequency than the commercial frequency) generated in the active element of the amplifier means 10 is similar to that of the first embodiment in the OP amplifier 10a. It can be prevented from being superimposed on the output and being input to the subsequent leakage detection circuit 4.

FIG. 2 is a configuration circuit diagram of a main part of an earth leakage breaker according to Embodiment 1 of the present invention. Detailed circuit diagram of the amplification means, sensitivity setting device, and amplification setting device in FIG. Detailed circuit diagram of the amplifying means, sensitivity setting device, and amplification setting device of the earth leakage circuit breaker according to the second embodiment of the present invention Block circuit diagram of a conventional earth leakage breaker Block circuit diagram of an earth leakage breaker according to the prior application of the present invention Detailed circuit diagram of power supply circuit and test circuit in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC circuit 2 Main circuit switching contact 3 Zero phase current transformer 3a Earth leakage detection winding 3b Test winding 4 Earth leakage detection circuit 5 Trip coil (tripping device)
6 Test circuit 6a Test switch 6b Oscillator circuit 9 Power supply circuit 9a Three-phase full-wave rectifier circuit 9c Smoothing capacitor 10 Amplifying means 10a OP amplifier 10b Analog switch 11 Sensitivity setter 12 Amplification degree setter 14 Input resistance of power supply circuit

Claims (5)

An open / close contact that opens and closes the multi-phase AC circuit, a zero-phase current transformer that detects the leakage current of the AC circuit, and the presence or absence of leakage in the AC circuit is determined from the secondary output of the zero-phase current transformer. A leakage detection circuit that outputs a signal in the case of failure, a tripping means that opens the switching contact in response to the output signal of the leakage detection circuit, and a test wound around the zero-phase current transformer by turning on the test switch An earth leakage circuit breaker having a test circuit for supplying a simulated leakage current to the winding, a leakage detection circuit from the AC circuit, and a power circuit for supplying power to the test circuit, the power circuit rectifying all phases of the AC circuit In the constant voltage power supply circuit that converts to direct current, and the test circuit that uses the power supply circuit as a power supply includes an oscillation circuit that sets the frequency of the simulated leakage current to a frequency different from the commercial frequency,
An earth leakage sensitivity setting device that selectively sets the earth leakage detection sensitivity between the secondary side of the zero phase current transformer and the earth leakage detection circuit, and the earth leakage from the zero phase current transformer when the test switch is turned on using the power supply circuit as a power source. An earth leakage breaker comprising an amplifying means for controlling a secondary output current supplied to the detection circuit with an amplification degree corresponding to the setting of the earth leakage sensitivity setting device. 2. The earth leakage circuit breaker according to claim 1, wherein the amplifying means is an amplifier having an OP amplifier as an amplifying element and an amplification degree setting means that variably adjusts the amplification degree according to the setting of the leakage sensitivity setting device. An earth leakage circuit breaker characterized by comprising: 3. The earth leakage circuit breaker according to claim 2, wherein a passive filter element is added to the OP amplifier to form an active filter for noise reduction. 2. The earth leakage breaker according to claim 1, wherein an input resistor for surge attenuation is connected to all phases of the power line connecting the AC circuit and the power circuit, and the power circuit has a smoothing capacitance. An earth leakage circuit breaker. 5. The earth leakage circuit breaker according to claim 4, wherein a time constant that is a product of an input resistance connected to the power line and a smoothing capacitance of the power circuit is 0.001 or more.

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