JP4935455B2 - Earth leakage detector - Google Patents

Description

  The present invention relates to a leakage detecting device used for a leakage breaker or the like that detects the occurrence of a leakage due to a ground fault or the like in an electrical circuit, interrupts the electrical circuit, and protects a load and the electrical circuit from leakage.

  The leakage detection device is provided with a test circuit for confirming whether or not it operates normally. FIG. 3 shows a circuit configuration of a leakage detection device including a test circuit that has been most commonly used in a conventional leakage breaker.

  In FIG. 3, 1 is a leakage circuit breaker, R, S, and T are power supply side terminals of the leakage circuit breaker 1, and U, V, and W are load side terminals corresponding to the power supply side terminals R, S, and T, respectively. . The earth leakage breaker 1 includes a main electric circuit 2 made of a three-phase conductor that connects the power-side terminals R, S, T and the load-side terminals U, V, W, respectively. The main electric circuit 2 includes an interrupting part 2A having an opening / closing contact for opening / closing the main electric circuit 2 and an overcurrent of each phase conductor of the main electric circuit 2, and driving a trip device 2C to open / close the contact of the interrupting part 2A. An overcurrent detection device 2B is provided that opens and shuts off the main electric circuit 2.

  The earth leakage breaker 1 further includes an earth leakage detection device 3 for detecting an earth leakage current flowing in the main electric circuit 2 and driving the tripping device 2C to open the switching contact of the circuit breaker 2A and to interrupt the main electric circuit 2. ing.

  The leakage detection device 3 includes a zero-phase current transformer 4, an leakage detection circuit 6, a trip coil 7, a test switch 8, and a diode bridge rectifier circuit including an annular core 4A around which a secondary winding 5 and a test winding are wound. The rectifier circuit 10 is configured. The rectifier circuit 10 is a DC power source that converts the AC voltage between the R-phase conductor and the T-phase conductor of the main circuit 2 into a DC voltage and supplies operating power to the leakage detection circuit 6.

  The zero-phase current transformer 4 is connected to the main electric circuit 2 by passing all the phase conductors of the main electric circuit 2 as the primary conductor through the secondary winding 5 and the annular core 4A around which the test 11 is wound. A zero-phase current flowing in the main circuit 2 due to a ground fault or a ground fault occurring in a load circuit (not shown) is detected and taken out by the secondary winding 5. The leakage detection circuit 6 determines the magnitude of the zero-phase detection current (leakage detection current) taken from the secondary winding 5 of the zero-phase current transformer 4, and when this becomes larger than a preset reference value, A leakage detection signal indicating the occurrence of leakage is generated.

  When an electric leakage detection signal indicating the occurrence of electric leakage is generated from the electric leakage detection circuit 6, the trip coil 7 is excited and the tripping device 2C is driven, whereby the interrupting portion 2A is tripped and interrupted. Thereby, the main electric circuit 2 is interrupted | blocked and the load circuit not shown connected to the earth leakage circuit breaker 1 can be protected from a ground fault accident and an earth leakage accident.

  Further, the test winding 11 provided in the zero-phase current transformer 4 is connected to the R-phase conductor of the main circuit 2 and the T through the test contact 8A and the test resistor 12 which are opened and closed by pressing the push button 8B of the test switch 8. A test circuit is configured by connecting to the phase conductor. By pressing the push button 8B of the test switch 8 and closing the test contact 8A, it is possible to test whether or not the leakage detecting device 3 operates normally. That is, by pressing the push button 8B, a simulation is performed by causing a current to flow through the test winding 11 via the test resistor 12 and the test contact 8A according to the voltage between the R-phase conductor and the T-phase conductor of the main circuit 2. Can generate a zero-phase current. This simulated zero-phase current is selected by the test resistor 12 to a predetermined magnitude that exceeds the reference value set in the leakage detection circuit 6.

  Therefore, if the leakage detection circuit 6 or the tripping device 2C of the leakage breaker 1 is normal, the leakage detection circuit 6 indicates the occurrence of leakage due to the zero-phase detection current extracted from the secondary winding 5 at this time. An electric leakage detection signal is generated, and the interrupting unit 2A is interrupted via the trip device 2C. It is possible to confirm that the leakage detection device 3 and the leakage breaker 1 themselves are operating normally by the breaking operation of the leakage breaker 1.

  At this time, if the earth leakage breaker 1 does not perform the breaking operation, it can be confirmed that there is an abnormality somewhere in the earth leakage detection device 3 or the earth leakage breaker 1.

In such a test circuit of the leakage detection device, a floating capacitance C ₀ exists between the secondary winding 5 and the test winding 11 in the zero-phase current transformer 4. Since the negative terminal of the DC output of the rectifier circuit 10 is connected to the signal ground SG as the ground side of the electronic circuit constituting the leakage detection circuit 6 and the like, the secondary winding connected to the leakage detection circuit 6 Line 5 is approximately at the potential of signal ground SG.

  On the other hand, since the test winding 11 is connected to the two-phase conductor of the main electric circuit 2 via the test contact 8A and the test resistor 12, the test contact 8A is always open (ie, the test contact 8A is opened and the leakage breaker 1 is leaked). Is in the T phase potential of the main circuit 2 connected to one of the AC input ends of the rectifier circuit 10. The signal ground SG becomes the potential of the T phase or the R phase of the main circuit 2 in accordance with the conduction state of the two diodes Dr2 and Dt2 constituting the lower arm of the diode bridge of the rectifier circuit 10.

For this reason, a voltage e having a half-wave rectified waveform of the RT interphase voltage as shown in FIG. 5 is applied between the test winding 11 and the secondary winding 5. As shown by the dotted arrows in FIG. 3, the floating capacitance C ₀ , the input signal line c of the leakage detection circuit 6, the leakage detection circuit 6, and the negative DC power supply line (also referred to as a ground line) a are routed by this voltage e. Noise current i flows.

By the way, the input terminal of the pair of leakage detection circuits 6 to which the paired input signal lines b are connected is the input terminal of a comparison amplifier (not shown), and the impedance configuration when the ground line a side is viewed from the pair of input terminals. Is not in equilibrium. For this reason, there is a problem that an induced voltage e ₁ is generated between the pair of input terminals of the leakage detection circuit 6 due to the noise current i, and the operation sensitivity of the leakage breaker 1 is changed.

  In order to solve this problem, a leakage detection device as shown in Patent Document 1 has been proposed. FIG. 4 shows a circuit configuration of the conventional leakage detection device disclosed in Patent Document 1.

4 differs from the conventional device shown in FIG. 3 in that one terminal of the test winding 11 of the zero-phase current transformer 4 is connected to the main circuit via a series circuit of the test contact 8A and the test resistor 12. The other terminal not connected to the test contact 8A is directly connected to the negative output ground line a of the rectifier circuit 10 connected to the signal ground SG. is there. Other configurations are the same as those of the conventional apparatus shown in FIG.
JP 2003-249160 A

  With this configuration, the test winding 11 is connected to the ground line a of the rectifier circuit 10 and has the same potential as the test winding 11, so that the test winding 11 has a half-wave rectified waveform as shown in FIG. Since the common mode voltage is not induced, the detection sensitivity of the leakage detection device is not changed and is stable.

  However, in this conventional apparatus, since the connection line f for connecting the test winding 11 of the zero-phase current transformer 4 to the ground line a of the rectifier circuit 10 is provided, the connection line f serves as an antenna and radiated electromagnetic noise. There is a disadvantage that resistance to is poor. That is, when radiated electromagnetic wave noise is induced to the ground line a through the connection line f, the potential of the ground line a fluctuates, the leakage detection sensitivity changes, and an unstable problem arises.

  In order to solve the problems in the conventional device as described above, the common mode noise is not induced in the test winding of the zero-phase current transformer, and the radiated electromagnetic wave noise to the ground line of the leakage detection device It is an object of the present invention to provide a leakage detection device that suppresses the induction of noise and has a stable leakage detection sensitivity.

  In order to solve the above problems, the present invention allows a conductor of a main electric circuit to pass through an annular core provided with a secondary winding and a test winding, and detects a zero-phase current flowing through the main electric circuit to detect the secondary phase. The magnitude of the zero-phase current transformer taken out from the winding and the zero-phase detection current taken out from the secondary winding of this zero-phase current transformer is judged, and when this becomes larger than a preset reference value, An earth leakage detection circuit for outputting an earth leakage detection signal indicating the occurrence of an electric current; a DC power source comprising a rectifier circuit for converting an AC voltage of an AC power source into a DC voltage and supplying the same to the earth leakage detection circuit; and the zero-phase current transformer And a test circuit including a test switch for closing and supplying a test current only when performing an operation test on the test winding, wherein one of the test windings of the zero-phase current transformer in the test circuit is provided. Through the test switch Connected to one AC input terminal of the rectifier circuit, and the other terminal not connected to the test switch of the test winding is connected to the other terminal of the rectifier circuit via a diode whose polarity is such that the cathode faces the test winding terminal. It is characterized by being connected to an AC input terminal.

  According to the present invention, in the leakage detection circuit, one end of the test winding of the zero-phase current transformer of the test circuit connected to the test switch is connected to the AC input terminal of the rectifier circuit constituting the DC power supply of the leakage detection circuit. And the other end of the test winding to which the test switch is not connected is connected to the AC input end of the rectifier circuit via a diode whose cathode faces the test winding end. Since the common mode voltage applied to the test winding from the AC power supply is blocked by the diode inserted in the test circuit, the induction of the common mode voltage to the test winding can be eliminated. . And since there is no connection line which connects the ground line of the leakage detection circuit and the test winding of the zero-phase current transformer, induction of radiated electromagnetic noise can be suppressed. For this reason, since the induction | guidance | derivation of the noise which fluctuates the operation sensitivity of a leak detection apparatus can be suppressed, the operation sensitivity of a leak detection apparatus can be kept stable. Therefore, it is possible to provide a leakage detecting device with stable operation.

  Embodiments of the present invention will be described below based on examples shown in the drawings.

  FIG. 1 is a circuit configuration diagram showing an embodiment in which the present invention is applied to an earth leakage circuit breaker.

  The first embodiment of the present invention shown in FIG. 1 is different from the conventional apparatus shown in FIG. 4 in the following points.

That is, in the test circuit for supplying a test current to the test winding 11 of the zero-phase current transformer 4 of the leakage detection device 3, one end of the test winding 11 is rectified to constitute a DC power supply via the contact 8A of the test switch. Connect to the AC input terminal connected to the R-phase conductor of the main circuit 2 of the circuit 10, and connect the other end of the test winding 11 to the ground line a, and connect the rectifier circuit 10 via the diode D and the test resistor 12. It is a point connected to the AC input terminal connected to the T-phase conductor of the main electric circuit 2. The diode D is inserted with a polarity in which the cathode faces the test winding side.
Since other configurations of the first embodiment are the same as those of the conventional apparatus, the same elements are denoted by the same reference numerals, and the description thereof is omitted.

  The earth leakage breaker 1 provided with the earth leakage detection device according to the first embodiment shown in FIG. 1 basically operates in the same manner as the conventional device. That is, in the normal leakage monitoring state, the test switch 8 is not operated and the test contact 8A is opened. When a zero-phase current due to electric leakage or the like is generated in the main circuit 2, a zero-phase detection current corresponding to the magnitude is taken out from the secondary winding 5. The leakage detection circuit 6 determines the magnitude of the zero-phase detection current taken from the secondary winding 5 of the zero-phase current transformer 4, and when this is larger than a preset reference value, the leakage indicating the occurrence of leakage Generate a detection signal.

  As a result, the trip coil 7 is excited to drive the tripping mechanism 2C of the earth leakage circuit breaker 1, the latch of the breaking unit 2A is pulled off, and the open / close contact is opened to cut off the main electric circuit 2 and load side A load circuit (not shown) connected to the terminals U, V, and W is protected from electric leakage.

  Further, when performing an operation test of the earth leakage breaker 1 and the earth leakage detection device 3, the test button 8B of the test switch 8 is pressed. In accordance with this, the test contact 8A is closed, so that a zero-phase current exceeding the reference value level is applied to the test winding 11 via the test resistor 12 and the test contact 8A by the AC voltage between the R-phase conductor and the T-phase conductor of the main circuit 2. Simulated test current can be supplied.

  If the leakage detection device 3 or the tripping device 2C of the leakage breaker 1 is normal, the detection current based on the simulated zero-phase current is taken out from the secondary winding 5 and the leakage detection circuit 6 The occurrence is detected, and a leakage detection signal indicating the occurrence of leakage is generated. The trip coil 7 and trip device 2C are activated by this leakage detection signal, and the breaker 2 of the leakage breaker 1 is cut off. Thereby, it can be confirmed that the leakage detection device 3 and the leakage breaker 1 are operating normally.

  At this time, if there is an abnormality in the leakage detection circuit 6, the trip coil 7, the tripping device 2C, etc., the breaker 2 of the leakage breaker 1 does not perform the breaking operation, thereby causing the leakage breaker 1 or the leakage detection device. It can be confirmed that there is an abnormality somewhere.

  On the other hand, an AC power supply voltage of about 100 V to 415 V is generally applied to the power supply side terminals R, S, and T of the earth leakage breaker 1 in the first embodiment, but this AC is detected in the earth leakage detection circuit 6 of the earth leakage detection device 3. The power supply voltage is full-wave rectified by the rectifier circuit 10 and a DC voltage reduced to about 10 V by the limiting resistor 15 and the smoothing capacitor 16 is applied.

  For this reason, the power supply line b and the input line c of the leakage detection circuit 6 are placed at a potential that is substantially close to the potential of the power supply line a. On the other hand, when the potential of the AC power supply line d connected to the terminal of the test winding 11 to which the test contact 8A is not connected is based on the potential of the ground line a of the rectifier circuit 10 serving as a DC power supply, FIG. Changes to a half-wave rectified waveform as shown in FIG. However, since the diode D is connected to the terminal of the test winding 11 where the test contact 8A is not connected with the polarity facing the cathode toward the terminal side, the potential of the ground line a of the AC power supply line d is greater than the potential. High potential will be blocked. Therefore, no potential difference is generated between the test winding 11 and the secondary winding 5, and no common mode noise is induced in the secondary winding 5. Therefore, during the leakage monitoring operation of the leakage detection device 3, the operation sensitivity is stabilized without fluctuation.

  Further, according to the apparatus of the first embodiment, instead of newly inserting the diode D in the test winding 11, the connection line to the ground line a of the DC power supply circuit is omitted, so that induction of radiated electromagnetic noise is induced. Therefore, the operation sensitivity of the leakage detecting device can be stabilized.

  FIG. 2 shows a second embodiment in which the present invention is applied to a leakage protection relay.

  In the second embodiment, in terms of circuit configuration, the circuit breaker portion, that is, the circuit breaker 2A, the switching contact 2A, the overcurrent detection device, and the tripping mechanism 2C are excluded from the leakage breaker of the first embodiment. The output relay 9 is provided in place of the trip coil 7. Further, the leakage detection device of the second embodiment has substantially the same configuration as the leakage detection device shown in the first embodiment, but an AC power supply other than the main circuit 2 is used as an AC power supply for the rectifier circuit 10 and the test winding 11. The difference is that power input terminals X and Y are provided for connection to a power source.

  In the apparatus of the second embodiment, when a zero-phase current due to leakage or the like is generated in the main circuit 2 that monitors leakage, a zero-phase detection current is taken out from the secondary winding 5, and the magnitude thereof is detected by the leakage detection circuit 6. If it is determined and the reference value is exceeded, a leakage detection signal is generated, and the contact 9A is closed by the output force relay 9 to notify the detection of leakage.

  The AC input terminal of the rectifier circuit 10 forming the DC power supply is connected to power input terminals X and Y to which an external AC power supply is connected. One end of the test winding 11 of the zero-phase current transformer 4 is also connected to the power input terminal X via the contact 8A of the test switch 8, and the other end is connected to the power input terminal Y via the diode D and the test resistor 12. Is done. The cathode of the diode D is directed to the test winding end side.

  For this reason, also in the second embodiment, the voltage applied to the test winding 11 that is higher than the potential of the ground line a connected to the negative electrode of the DC output of the rectifier circuit 10 is blocked by the diode D. Thus, no potential difference is generated between the test winding 11 and the secondary winding 5, and induction of common mode noise to the secondary winding 5 is eliminated. And since there is no connection of the extra wiring to the ground line a, induction of radiated electromagnetic noise can be suppressed. Therefore, also in the leakage detection device 3 of the second embodiment, the operation sensitivity during the leakage monitoring operation can be stabilized.

It is a circuit block diagram which shows the leak detection apparatus by Example 1 of this invention. It is a circuit block diagram which shows the leak detection apparatus by Example 2 of this invention. It is a circuit block diagram which shows the conventional electric leakage detection apparatus. It is a circuit block diagram which shows the conventional different earth-leakage detection apparatus. It is a voltage waveform diagram in the apparatus for operation | movement description of a leak detection apparatus.

Explanation of symbols

1: Earth leakage breaker 2: Circuit breaker 3: Earth leakage detection device 4: Zero phase current transformer 5: Secondary detection winding 6: Earth leakage detection circuit 7: Trip coil 8: Test switch 9: Output relay 10: Rectifier circuit 11 : Test winding D: Diode

Claims (1)

  A zero-phase current transformer in which a conductor of a main electric circuit is passed through an annular core provided with a secondary winding and a test winding, and a zero-phase current flowing in the main electric circuit is detected and taken out from the secondary winding; Leakage detection that determines the magnitude of the zero-phase detection current taken from the secondary winding of the zero-phase current transformer and outputs a leakage detection signal that indicates the occurrence of a leakage when it exceeds a preset reference value Closed only when performing an operation test on the circuit, a DC power source comprising a rectifier circuit that converts the AC voltage of the AC power source into a DC voltage and supplies it to the leakage detection circuit, and a test winding provided in the zero-phase current transformer And a test circuit including a test switch configured to supply a test current, wherein one end of a test winding of a zero-phase current transformer in the test circuit is connected to the rectifier circuit via the test switch. Connect to one AC input end of And the other terminal to which the test switch of the test winding is not connected is connected to the other AC input terminal of the rectifier circuit via a diode whose cathode faces the end of the test winding. Detection device.

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