JP2006006043A - Electric leakage sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect electric leakage at a location away from a generator without pulling around a ground wire for grounding the neutral point of the generator, in an electric leakage sensor for detecting the electric leakage of a power unit using an AC generator as a power source. <P>SOLUTION: The electric leakage sensor is provided with a detection point forming circuit 5A which forms the detection point D connected to the three-phase output wire of the AC generator 1 via either a resistor Ru or Rw, a voltage detection circuit 5B for detecting the voltage between the detection point D and the ground, and an electric leakage detection section 5C for detecting the presence of the electric leakage from the voltage detected by the voltage detection circuit 5B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a leakage detection device that detects a leakage of a power supply device that supplies power to a load using an AC generator as a power source.

As a device for detecting a leakage (ground fault) of a power supply device using an AC generator as a power source, as shown in Patent Document 1 and Patent Document 2, a neutral point of an armature winding of a three-phase AC generator There has been proposed a leakage detection device that detects a leakage current by detecting a zero-phase current flowing through a ground line connecting between the ground and the ground.
JP-A-10-142282 JP 2000-149758 A

  As shown in Patent Document 1 and Patent Document 2, in a leakage detection device that detects a leakage from a zero-phase current that flows through a ground line that grounds a neutral point of a generator when a leakage occurs, the leakage detection device When it is necessary to install the cable at a location away from the generator, it is necessary to route a long grounding wire that grounds the neutral point from the generator to the installation location of the leakage detection device. There was a problem of being troublesome.

  When the AC generator armature winding has no neutral point, for example, when the three-phase armature winding is Δ-connected, or when the generator is a single-phase AC generator, The proposal of could not be applied.

  The object of the present invention can be installed at a location away from the alternator without drawing a long ground wire, and can also be applied when the alternator does not have a neutral point. The object is to provide a leakage detection device.

  The present invention is applied to a leakage detection device that detects a leakage of a power supply device that supplies power to a load using an AC generator as a power source. The power supply device to which the leakage detection device according to the present invention is applied may be any device provided with an AC generator as a power supply, and its configuration is arbitrary. A typical power supply device suitable for applying the leakage detection device of the present invention is a converter that converts the output of an AC generator into a DC voltage, and the DC voltage obtained from the converter is converted into an AC voltage. Such as an inverter having an inverter for conversion or an excitation type AC generator having a field coil and adjusting an output voltage by controlling an excitation current. It is not something.

  In the present invention, a detection point forming circuit that forms a detection point coupled to each output line of an AC generator through a high impedance element, a voltage detection circuit that detects a voltage between the detection point and ground, and a voltage detection circuit A leakage detection unit is provided for detecting that a leakage has occurred when the detected voltage is equal to or higher than a set determination value.

  When the alternator is a three-phase alternator, in a preferred aspect of the present invention, one of the three-phase output lines of the alternator is connected to one end, and the other end is connected in common. The detection point forming circuit is configured by a resistor, and a common connection point of the three resistors is used as a detection point.

  Further, when the AC generator is a single-phase AC generator, in a preferred embodiment of the present invention, the detection point forming circuit is configured by a resistance voltage dividing circuit connected between two output lines of the AC generator, The voltage dividing point of the resistance voltage dividing circuit is used as a detection point.

  As described above, a detection point coupled to each output line of the AC generator through a high impedance element is provided, and when a voltage between the detection point and the ground is detected, the detection point The voltage between the grounds is almost 0 level, and when a power leak occurs in the power supply device, the voltage between the detection point and the ground becomes equal to or higher than the threshold value. Therefore, the voltage between the detection point and ground can be detected, and when the detected voltage is less than the judgment value set to an appropriate value, it can be detected that there is no leakage in the power supply unit. When the measured voltage is equal to or higher than the determination value, it is possible to detect that a leakage has occurred.

  When configured as described above, it is only necessary to couple the detection point forming circuit to the output line of the generator near the installation location of the leakage detection device without drawing a grounding wire for grounding the neutral point of the generator. The leakage of the power supply device can be detected at a location away from the generator without requiring a grounding wiring process. In addition, even when the armature coil of the generator does not have a neutral point, the leakage can be detected.

  As described above, according to the present invention, a detection point coupled to each output line of an AC generator through a high impedance element is provided, and the presence or absence of a leakage is detected from the voltage between the detection point and the ground. Therefore, there is an advantage that the leakage of the power supply device can be detected at a location away from the generator without drawing a long grounding wire for grounding the neutral point of the generator. Further, according to the present invention, it is possible to detect a leakage even when the armature coil of the generator does not have a neutral point.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the embodiment shown in FIG. 1, the output of a three-phase AC generator is converted into a DC voltage by a converter, and then the DC voltage is converted into an AC voltage having a constant frequency by an inverter and supplied to a load. A power generation device is used as a power supply device that drives a load.

  In FIG. 1, reference numeral 1 denotes a three-phase AC generator driven by a prime mover such as an internal combustion engine. This generator has three-phase armature coils Lu to Lw connected in a star shape. The three-phase output lines 1u to 1w of the AC generator 1 are connected to the three-phase input lines 2u to 2w of the converter 2 composed of a full-wave rectifier circuit, and the voltage between the DC output terminals 2a and 2b of the converter 2 is an inverter. 3 is input. The inverter 3 outputs a full-bridge type inverter circuit (INV) 3A composed of an H-bridge circuit in which each side of the bridge is configured by switching elements such as IGBTs and MOSFETs, and an AC voltage having a desired frequency from the inverter circuit 3A. And a controller 3B that controls on / off of switch elements constituting the inverter circuit, and a filter circuit 3C that removes harmonic components from the AC voltage output from the inverter circuit 3A. In this example, an inverter device 4 is constituted by the converter 2 and the inverter 3, and a power supply device is constituted by the inverter device 4 and the AC generator 1. The filter circuit 3C is a low-pass circuit composed of coils L1, L2, a capacitor C1, and the like, and supplies a constant frequency AC voltage Vac from which harmonics have been removed to the load through the load connection terminals 4a, 4b. .

  Reference numeral 5 denotes a leakage detection device according to the present invention. This leakage detection device is a detection point forming circuit 5A that forms detection points D coupled to the three-phase output lines 1u to 1w of the AC generator 1 through high impedance elements, respectively. And a voltage detection circuit 5B that detects a voltage between the detection point D and the ground, and a leakage detection that detects that a leakage has occurred when the voltage detected by the voltage detection circuit 5B exceeds a set determination value. Part 5C.

  The detection point forming circuit 5A shown in the figure has three resistors Ru, one end of which is electrically connected to the three-phase output lines 1u to 1w of the AC generator 1, and the other end connected in common and star-connected. Or a common connection point of the three resistors Ru to Rw is used as the detection point D. When the resistance values of the resistors Ru to Rw are set equal, the potential at the detection point D becomes substantially equal to the potential at the neutral point N of the armature coils Lu to Lw of the generator. That is, the detection point D is a virtual neutral point of the power supply device. Therefore, in the state where no ground fault has occurred in the power supply device, the ground voltage at the detection point D is almost zero. However, when a ground fault occurs, a zero-phase voltage is detected between the detection point D and the ground. appear. As a matter of course, the resistance values of the resistors Ru to Rw are set to a sufficiently large value so as not to cause a loss causing a problem in the detection point forming circuit 5A.

  The illustrated voltage detection circuit 5B includes a resistance voltage dividing circuit including resistors R1 and R2 connected in series between the detection point D and the ground, and a resistor R3 having one end connected to the voltage dividing point of the resistance voltage dividing circuit. And a capacitor C2 connected between the other end of the resistor R3 and the ground, and a detection voltage Vnv proportional to the voltage between the detection point D and the ground is output to both ends of the capacitor C2.

  The leakage detection unit 5C detects that a leakage has occurred when the voltage between the detection point D detected by the voltage detection circuit 5B and the ground is equal to or higher than a set determination value. , A reference voltage generation circuit for generating a constant reference voltage for giving a judgment value, and comparing the detection voltage Vnv with the reference voltage, and outputting an output signal having different levels depending on whether the detection voltage Vnv is lower or higher than the reference voltage And a comparator that generates the signal. Further, the leakage detector 5C can be configured to detect the presence or absence of leakage by processing the output of the voltage detection circuit 5B using a microprocessor.

  The detection output of the leakage detector 5C is used as a command signal for instructing to stop the prime mover that drives the AC generator 1 when a leakage occurs, or to drive an alarm generating means when a leakage occurs. Can be used as a signal.

  In the embodiment shown in FIG. 1, a magnet generator having a three-phase armature coil is used as the AC generator 1, the output voltage of the inverter 3 is set to 100 [V], and the frequency is set to 50 [Hz]. 6 to 8 show the results of observing the detection voltage Vnv obtained from the voltage detection circuit 5B when the ground fault is not generated and when the ground fault is generated. The detection voltage Vnv obtained from the voltage detection circuit 5B when no ground fault has occurred in the power supply device is maintained at almost 0 level as shown in FIG. 6 to 8, Vac represents an output voltage of the inverter.

  On the other hand, as shown in FIG. 2, when a ground fault occurs at the point A1 of the one-phase output line of the AC generator, as shown in FIG. The output voltage of the machine 1 is equal in frequency and exhibits an AC waveform having a constant peak value. As shown in FIG. 3, when a ground fault is generated at point A2 on the output side of the inverter, as shown in FIG. 8, the detected voltage Vnv is an AC waveform having the same frequency as the output voltage Vac of the inverter. Presents.

  As described above, the voltage between the detection point D and the ground is maintained at almost 0 level when a ground fault occurs in the power supply device, and becomes a large level when a ground fault occurs in the power supply device. Therefore, by detecting the voltage between the detection point and the ground and determining whether or not the detection level is equal to or higher than the set determination value, it is possible to detect whether or not a power leak has occurred in the power supply device. it can. In addition, since the frequency of the detection voltage Vnv differs depending on whether the ground fault occurs on the generator side or on the inverter side, the location where the ground fault accident has occurred by looking at the frequency of the detection voltage Vnv It is also possible to specify.

  In the above embodiment, the resistance values of the resistors Ru to Rw constituting the detection point forming circuit 5A are made equal to make the ground potential at the detection point D substantially equal to the ground potential at the neutral point N of the AC generator. However, the detection point D may be any point as long as it is coupled to each output line of the generator through a high impedance element and has a potential different from the potential of any output line of the generator, and the resistance of the resistors Ru to Rw. The values do not necessarily have to be equal. When the resistance values of the resistors Ru to Rw are made different, a zero-phase voltage appears between the detection point D and the ground circuit even when no ground fault occurs, but the resistances of the resistors Ru to Rw If the resistance value is set appropriately so that the degree of unbalance of the resistance value of these resistors does not exceed the limit, it will appear between the detection point D and the ground when no ground fault has occurred. Since a clear difference can be produced between the voltage and the voltage appearing between the detection point D and the ground when a ground fault occurs, the reference voltage level (determination value) to be compared with the detection voltage Vnv is set. By setting appropriately, the presence or absence of a ground fault (electric leakage) can be detected without any problems.

  In the example shown in FIG. 1, the detection point forming circuit 5A is coupled to the output line of the generator in the inverter device 4. However, the detection point forming circuit 5A is connected to the generator output line outside the inverter power generation device 4. Of course, they may be combined.

  In the above embodiment, the armature coil of the AC generator 1 is star-connected. However, even when the AC generator has no neutral point, that is, when the armature coil is Δ-connected, the leakage Can be detected without any problem.

  In the above embodiment, a three-phase AC generator is used as the AC generator 1. However, as shown in FIG. 4, the AC generator 1 is a single-phase armature provided with both ends ungrounded. The present invention can also be applied when a single-phase AC generator having the coil Wa is used. When a single-phase AC generator is used as the AC generator 1, a resistance voltage dividing circuit composed of a series circuit of resistors Ra and Rb having a sufficiently large resistance value is provided between the two output lines of the generator 1. The resistance voltage dividing circuit is connected to form a detection point forming circuit 5A, and the voltage dividing point of the resistance voltage dividing circuit is set as a detection point D. The other configuration of the embodiment shown in FIG. 4 is the same as that of the embodiment shown in FIG.

  Also in the example shown in FIG. 4, the resistance values of the resistors Ra and Rb may be the same or different. It is only necessary that the potential of the detection point D is different from any of the two output lines of the generator.

  The power supply device to which the leakage detection device of the present invention is applied is not limited to the one using an inverter device. For example, as shown in FIG. 5, the excitation current is controlled by the armature coil Wa and the field control circuit 10. The leakage detection device according to the present invention can also be applied to the case where the power supply device is configured by the excitation type AC generator 1 having the field coil We. The configuration of the leakage detection device 5 in this case is the same as that shown in FIG.

  In each of the above embodiments, the detection point D is coupled to each output line of the AC generator through a resistor, but the detection point D is coupled to each output line of the AC generator through a high impedance element, Any potential may be used as long as it shows a potential different from the potential of any output line of the generator and a zero-phase voltage is generated between the power supply device and the ground potential portion when a ground fault occurs. Therefore, the high impedance element that couples between the detection point D and each output line of the generator is not limited to the resistor.

It is the circuit diagram which showed the structure of embodiment of this invention. FIG. 2 is a circuit diagram illustrating a state in which a ground fault has occurred on the AC generator side in the embodiment of FIG. 1. FIG. 2 is a circuit diagram illustrating a state in which a ground fault has occurred in a circuit on the output side of an inverter in the embodiment of FIG. 1. It is the circuit diagram which showed other embodiment of this invention. It is the circuit diagram which showed other embodiment of this invention. FIG. 2 is a waveform diagram showing a waveform of a detection voltage obtained from a voltage detection circuit together with an output voltage waveform of an inverter when no ground fault occurs in the power supply device in the embodiment shown in FIG. 1. FIG. 2 is a waveform diagram showing a waveform of a detection voltage obtained from a voltage detection circuit together with an output voltage waveform of an inverter when a ground fault occurs in a circuit on the AC generator side of the power supply device in the embodiment shown in FIG. 1. FIG. 2 is a waveform diagram showing a waveform of a detection voltage obtained from a voltage detection circuit together with an output voltage waveform of the inverter when a ground fault occurs in the output circuit of the inverter of the power supply device in the embodiment shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC generator 2 Converter 3 Inverter 4 Inverter apparatus 5 Leakage detection apparatus 5A Detection point formation circuit 5B Voltage detection overcircuit 5C Leakage detection part

Claims (5)

A leakage detection device for detecting a leakage of a power supply device that supplies power to a load using an AC generator as a power source,
A detection point forming circuit that forms a detection point coupled to each output line of the AC generator through a high impedance element, a voltage detection circuit that detects a voltage between the detection point and ground, and a voltage detection circuit that detects the detection point An earth leakage detection device comprising: an earth leakage detection unit that detects that an earth leakage has occurred when a voltage that exceeds a predetermined determination value.   The AC generator is a three-phase AC generator, and the detection point forming circuit is composed of three resistors each having one end connected to the three-phase output line of the AC generator and the other end connected in common. The leakage detection device according to claim 1, wherein a common connection point of the three resistors is used as the detection point.   The AC generator is a single-phase AC generator, and the detection point forming circuit is a resistance voltage dividing circuit connected between two output lines of the AC generator. The leakage detection device according to claim 1, wherein a partial pressure point is used as the detection point.   4. The electric leakage according to claim 1, wherein the power supply device includes a converter that converts an output of the AC generator into a DC voltage, and an inverter that converts a DC voltage obtained from the converter into an AC voltage. Detection device. 5. The leakage detecting device according to claim 1, wherein the AC generator is an excitation type AC generator having a field coil.

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