JP5480572B2 - Ground fault detection device - Google Patents

Description

  The present invention relates to a ground fault detection device, and more particularly to a ground fault detection device that quickly detects a ground fault in the event of a ground fault due to a disconnection of a power transmission line, etc., and speeds up its recovery.

  In a high-voltage transmission line, the transmission line may contact the ground due to insulation deterioration of the transmission line or damage of the underground transmission line by a civil engineering machine, and a ground fault may occur. In order to detect such a failure early and perform recovery processing, a ground fault detection device is connected to the power transmission line to constitute a system.

  An example of a general basic configuration of such a ground fault detection system is shown in FIG. The ground fault detection system shown in FIG. 4 is connected to the power transmission line 1 and is connected to the feeder 2 for detecting the current change of the power transmission line 1 and to the feeder 2 via the optical cable 3. And a detector 4 for receiving and analyzing the detection signal from the detector 2. The feeder 2 includes an optical conversion unit 5 that converts a detection signal into an optical signal. The detector 4 includes a detection unit 6 that detects a ground fault from the received detection signal, an output unit 7 that outputs a detection result, and a power supply unit 8 that supplies power to the detector 4. A telecon board, that is, a computer (CPU) is connected to the output unit 7. The ground fault device shown in FIG. 4 is an example of a device that adopts the section determination method, and corresponds to current transformers (CT) 9 disposed at both ends of the predetermined section of the transmission line 1 respectively. A feeder 2 is provided. The detection signal from each feeder 2 is sent to one detector 4.

  As a conventional example of the ground fault detection device used in the ground fault detection system having such a basic configuration, for example, there is the one shown in FIG. In the conventional ground fault detection apparatus shown in FIG. 5, the feeder 2 filters the input unit 11 for inputting the fault current from the power transmission line 1 and the detection signal input from the input unit 11. A filter 12, a half-wave rectifier circuit 13 for half-wave rectifying the waveform of the detection signal, a voltage / frequency converter (V / F converter) 14 for converting the half-wave rectified voltage signal into a pulse signal, and a pulse signal An electric / optical conversion unit (E / O conversion unit) 15 for converting the signal into an optical signal and a stabilized power source 16 for stabilizing the power source of the feeder. The detector 4 is connected to the E / O converter 15 of the feeder 2 and converts an optical signal into a pulse signal. The detector 4 analyzes the detection signal. And an arithmetic processing unit 18 that identifies a section in which a ground fault has occurred.

  In such a configuration, the detection of the ground fault is performed by taking the fault current flowing from the transmission line 1 to the metering device 2 into the input unit 11 and creating a power source necessary for the operation of the metering device 2 from this fault current. Is filtered by the filter 12, and the fault current waveform is half-wave rectified by the half-wave rectifier circuit 13. Next, the half-wave rectified voltage signal is converted into a pulse signal by the V / F converter 14, this pulse signal is converted into an optical signal by the E / O converter 15, and then transmitted to the detector 4 through the optical cable 3. ing. In the detector 4, the input optical signal is converted into an electric signal by the O / E conversion unit 17, and the electric signal is analyzed by the arithmetic processing unit 18 so that the part or section of the transmission line 1 in which the ground fault has occurred. Is identified.

  In the operation of such a conventional ground fault detection device, half-wave rectification is performed as described above, so that the half-wave portion is lost as waveform information, and only the positive side of the alternating current of the power supply voltage is used. The current differential method is not applicable for failure detection.

  Further, the disconnection monitoring of the optical cable 3 between the feeder 2 and the detector 4 is performed near the output terminal of the feeder 2, that is, at the point A in FIG. 5, as shown in FIG. An optical coupler 20 is arranged, a disconnection detection signal is transmitted from the detector 4, the optical coupler 20 is used in the feeder 2 to return to the detector 4, and the optical signal is received on the detector 4 side. By doing so, the disconnection of the optical cable 3 is monitored. That is, two optical cables 3 and an optical coupler 20 are required for monitoring disconnection. Further, when there is an abnormality in the main circuit of the feeder 2 in the previous stage (input side) from the optical coupler 20, a malfunction of the circuit cannot be detected.

  The present invention has been made in view of such a conventional problem, and a first object thereof is to apply a current differential method as a detection method of a ground fault.

  The second object of the present invention is to reduce units and parts in the ground fault detection device and reduce the manufacturing cost of the ground fault detection device.

  The third object of the present invention is to provide a function of constantly monitoring the soundness of the main circuit in the feeder, and to improve the reliability of the ground fault detector.

  A fourth object of the present invention is to reliably identify a failure location at the time of occurrence of an abnormality and to promptly perform a recovery response.

  In order to solve the above problems, a ground fault detection device of the present invention is connected to a power transmission line, detects a power change of the power transmission line, is connected to the feeder via an optical cable, and A detector that receives and analyzes a detection signal from the meter, and the meter includes an input unit that inputs a fault current from the power transmission line, and a predetermined direct current to the detection signal that is input from the input unit. Stable power supply for DC superimposing unit that superimposes voltage, voltage / frequency converting unit that converts DC superimposed voltage signal into pulse signal, electrical / optical converting unit that converts pulse signal into optical signal, and feeder The detector includes an optical / electrical converter that converts an optical signal into a pulse signal, a frequency / voltage converter that converts the pulse signal into a voltage signal, and an analysis of the detection signal. Arithmetic processing unit that identifies the section where the ground fault has occurred Comprising a, in the Okuryou unit, the DC superposition unit is characterized in that input waveform detection signal to superimpose a direct current voltage so as to full-wave output.

  According to the present invention, a load-side fault current waveform can be expressed by adding and shifting a DC component to the fault current waveform and transmitting all waveform information. Thereby, the current differential detection method by digital calculation using sampling data can be applied using two feeders.

  In addition, by recognizing that the result of adding and shifting the DC component to the waveform of the fault current is equivalent to 0 amperes, the detector can determine whether there is a signal (0 amperes) or no signal from the feeder. In addition, when there is a signal, by monitoring the DC superposition of the communication line disconnection monitoring signal on the detector side, the V / F conversion unit of the feeder, E / O, which could not be automatically inspected conventionally. The failure of the converter, the O / E converter and the F / V converter of the detector can be determined, and the reliability of the detection function can be improved. Further, it is possible to prevent erroneous detection by recognizing the state of no signal.

  In addition, the present invention has functions for monitoring disconnection of communication lines, monitoring of analog circuits, and monitoring of remaining battery capacity, so that it becomes easy to identify a faulty part and to speed up recovery.

  In the present invention, even when the ground fault signal and the communication line disconnection signal are congested, the communication line disconnection signal is a direct current of 0 amperes and therefore does not affect the ground fault detection.

  A communication line disconnection monitoring signal, a bit string for monitoring the remaining battery level, and a failure current waveform can be transmitted to the detector side through a single optical cable, and this can be separated (signal multiplexing). Therefore, the optical cable is only one way, the optical coupler is not required, and the cost of the entire system can be reduced.

It is a block diagram which shows the structure of the ground fault detection apparatus which concerns on one embodiment of this invention. It is explanatory drawing which shows the battery remaining charge evaluation method in the ground fault detection apparatus of the said embodiment. It is explanatory drawing which shows the arithmetic processing which analyzes the multiplexed transmission of various signals in the ground fault detection apparatus of the said embodiment. 1 is a block diagram showing a general basic configuration of a ground fault detection system to which the present invention is applied. It is a block diagram which shows the structure of the conventional ground fault detector. It is a block diagram which shows the structure of the optical coupler used for the communication line disconnection detection in the conventional ground fault detection apparatus.

  Hereinafter, representative examples of the present invention will be described. FIG. 1 is a block diagram showing a configuration of a ground fault detection apparatus according to an embodiment of the present invention. The basic configuration of the ground fault detection system to which this embodiment is applied has the same configuration as the system shown in FIG. In FIG. 1, reference numeral 30 denotes a feeder. The feeder 30 includes an input unit 31 that inputs a fault current from the power transmission line 1 (see FIG. 4), a DC superimposing unit 32 that superimposes a predetermined DC voltage on the detection signal input from the input unit 31, A voltage / frequency conversion unit (V / F conversion unit) 33 that converts a DC superimposed voltage signal into a pulse signal, an electrical / optical conversion unit (E / O conversion unit) 34 that converts the pulse signal into an optical signal, A stabilized power source 35 that stabilizes the power supply of the feeder 30 connected to the DC superimposing unit 32, the V / F converting unit 33, and the E / O converting unit 34, and a DC power source connected to the stabilizing power source 35 to the DC superimposing unit 32. A battery 37 serving as an auxiliary power source for applying a voltage for superimposition and a CPU 36 for calculating the remaining amount of the battery 37 by calculation are provided. The detector 40 is connected to the E / O converter 34 of the feeder 30 and converts an optical signal into a pulse signal for restoration, and an O / E converter 41. A frequency / voltage conversion unit (F / V conversion unit) 42 that converts the converted pulse signal into a voltage signal, and an arithmetic process that identifies a section in which a ground fault has occurred by analyzing the voltage signal that is a detection signal Unit, that is, a CPU 43. The feeder 30 and the detector 40 are connected by an optical cable 35. 1 corresponds to the feeder 2 in FIG. 4, the detector 40 in FIG. 1 corresponds to the detector 4 in FIG. 4, and the optical cable 35 in FIG. 1 corresponds to the optical cable 3 in FIG. To do.

  In such a configuration, the detection of the ground fault is performed by taking the fault current flowing from the power transmission line 1 to the metering device 2 into the input unit 11 and generating a power source necessary for the operation of the metering device 30 from the fault current. By 32, the DC component is added and shifted to the fault current. As a result, it is possible to transmit the entire waveform information of the fault current. Next, the DC superimposed voltage signal is converted into a pulse signal by the V / F converter 33, and this pulse signal is converted into an optical signal by the E / O converter 34, and then transmitted to the detector 40 through the optical cable 35. Yes. In the detector 40, the input optical signal is converted into an electric signal (pulse signal) by the O / E converter 41, and the pulse signal subjected to O / E conversion is converted into a voltage signal by the F / V converter 42. The voltage signal is analyzed by the CPU 43 to detect a ground fault or to identify other states that identify the part or section of the transmission line 1 where the ground fault has occurred. The detection operation as the ground fault detection device includes the following operations.

(1) Ground fault detection In the V / F conversion unit 33 of the feeder 30, all the waveform information of the fault current is sent to the detector side as a frequency signal of f ₁ ± f _n kHz (kHz is the frequency unit kilohertz). To transmit. That is, the DC superimposition is f ₁ kHz. When a ground fault occurs, the alternating current waveform on both the positive and negative sides is transmitted with the direct current component superimposed. As can be seen from the system shown in FIG. 4, one metering device 30 is connected to each side of the section of the power transmission line 1, and all the waveform information of the fault current is transmitted from both the metering devices 30 to the detector 40. Is transmitted. On the detector 40 side, all waveform information of these fault currents is sampled, and the sampling data is digitally calculated by the CPU 43 to perform current differential detection.

(2) Analog circuit monitoring and remaining battery level detection DC superimposition signal f ₁ kHz is transmitted as T ₁ ms (ms is the millisecond of the unit of time) and T ₂ ms, and T ₁ ms is logically transmitted. While assigning to “0”, T ₂ ms is assigned to logic “1” and serially transmitted from the feeder 30 to the detector 40. When the DC superimposed signal measured in the detector 40 deviates from the preset monitoring width f ₁ ± Δf kHz, it is determined that the analog circuit between the feeder 30 and the detector 40 is abnormal. Moreover, the communication line disconnection monitoring of the optical cable 35 is performed by the DC superposition.

The feeder 30 measures the voltage of the battery 37 using the CPU 36, and evaluates the remaining voltage from the battery voltage. For example, as shown in FIG. 2, the remaining amount of battery is evaluated in four stages using the above logic “0” and logic “1” for 3 bits, and bit string data is transmitted to the detector 40. As a result, the remaining battery level on the feeder side can be detected. The bit string data is transmitted to the detector 40 using the DC superimposed signal once every time interval sufficiently longer than T ₁ and T ₂ .

(3) Communication line disconnection monitoring On the detector 40 side, when the received signal is in the range of f ₁ ± f _M kHz, the signal is “present” from the feeder 30 side, and when it is less than f ₁ −f _n kHz. It is determined from the feeder 30 that the signal is “none”. The f ₁ kHz frequency signal transmitted from the feeder 30 is recognized as a current corresponding to 0 amperes on the detector 40 side. That is, a binary value of 0 ampere and a signal “none” is discriminated. In this way, by recognizing that the result of adding and shifting the DC component to the waveform of the fault current is equivalent to 0 amperes, the detector 40 outputs the signal “present” (0 amperes) or “signal absent” from the feeder 30. Binary values can be discriminated, and when the signal is “present”, automatic detection has not been possible in the past by monitoring the DC superimposition of the communication line disconnection monitoring signal in the optical cable 35 on the detector 40 side. The failure of the V / F converter 33, the E / O converter 34 of the feeder 30 and the O / E converter 41 and the F / V converter 42 of the detector 40 can be determined, and the reliability of the detection function is improved. Can be planned. Further, by recognizing the state of the signal “none”, erroneous detection can be prevented.

  In this detection operation, when a ground fault occurs and when the detector 40 receives a communication line disconnection monitoring signal, an excessively large alternating current component is present before and after the signal generation and before and after the occurrence of the ground fault signal. Although it is detected and may be a cause of erroneous detection, the state of the signal “none” can be detected from the immediately preceding DC component, and erroneous detection can be prevented. Thus, even when the ground fault signal and the communication line disconnection signal are congested, the communication line disconnection signal is a direct current of 0 amperes and thus does not affect the detection of the ground fault.

(4) Multiplexed Transmission of Detection Signal From the feeder 30, various detection signals are transmitted to the detector 40 by multiplexed transmission. The detector 40 includes an A / D converter 44 on the downstream side (downstream side) of the F / V converter 42, a DC removal filter 45 that is connected to the A / D converter 44 and removes a DC component by digital processing, A fundamental effective value calculation unit 46 connected to the removal filter 45. Further, the DC effective value calculation unit 47 connected to the A / D conversion unit 44 in a parallel relationship with the DC removal filter 45, and similarly, the DC removal filter 45 is connected to the A / D conversion unit 44 in a parallel relationship. And a detector 48 for detecting the signal “none” from the feeder 30. The DC effective value calculation unit 47 calculates the DC effective value by, for example, the area method. Then, the detector 40 restores the frequency signal to an analog waveform by the F / V conversion unit 42, further performs A / D conversion by the A / D conversion unit 44, and takes in the built-in memory. Further, the detector 40 performs a filtering process by a direct current removal filter 45 as a digital processing means, and then obtains a fundamental wave effective value by a fundamental wave effective value calculation unit 46. Also, the DC effective value calculation unit 47 obtains the DC effective value, and the detection unit 48 detects the signal “none” from the feeder 30. Thereby, the communication line disconnection monitoring signal, the bit string for monitoring the remaining battery level, and the failure current waveform can be transmitted to the detector side by one optical cable, and this can be separated (signal multiplexing). Therefore, the optical cable is only one way, the optical coupler is not required, and the cost of the entire system can be reduced.

  In the present invention, by adding and shifting the DC component to the waveform of the fault current and transmitting the entire waveform information, the negative fault current waveform can be expressed, and sampling can be performed using two feeders. A current differential detection method using digital calculation using data can be applied.

  Further, by recognizing that the result of adding and shifting the DC component to the waveform of the fault current is equivalent to 0 amperes, it is possible to determine whether there is a signal or no signal, and the V / F converter of the feeder Failure of the E / O converter, the detector O / E converter, and the F / V converter can be determined, and the reliability of the detection function can be improved.

  In addition, the present invention has functions for monitoring disconnection of communication lines, monitoring of analog circuits, and monitoring of remaining battery capacity, so that it becomes easy to identify a faulty part and to speed up recovery.

  In addition, a communication line disconnection monitoring signal, a bit string for monitoring the remaining battery level, and a fault current waveform can be transmitted to the detector side using a single optical cable, and this can be separated (signal multiplexing). Therefore, the optical cable is only one way, the optical coupler is not required, and the cost of the entire system can be reduced.

DESCRIPTION OF SYMBOLS 1 Transmission line 2,30 Feeder 3,35 Optical cable 4,40 Detector 11,31 Input part 32 DC superimposition part 33 V / F conversion part 34 E / O conversion part 36 CPU
37 Battery 41 O / E converter 42 F / V converter

Claims (5)

A feeder that is connected to both ends of the section of the transmission line and detects a current change in the transmission line,
It is connected to these metering devices via an optical cable, and consists of a detector that receives and analyzes the detection signal from the metering device,
The feeder includes an input unit for inputting a fault current from the power transmission line, a DC superimposing unit for superimposing a predetermined DC voltage on a detection signal input from the input unit, and a pulse signal for the DC superimposed voltage signal. A voltage / frequency conversion unit for converting into an electric signal, an electric / optical conversion unit for converting a pulse signal into an optical signal, and a stabilized power source for stabilizing the power source of the feeder,
The detector includes an optical / electrical converter that converts an optical signal into a pulse signal, a frequency / voltage converter that converts a pulse signal into a voltage signal, and a section in which a ground fault has occurred by analyzing the detection signal And an arithmetic processing unit for identifying
In the feeder, the DC superimposing unit superimposes a DC voltage so that the input waveform of the detection signal can be output in a full wave ,
The detector is further connected to an A / D converter on the rear side of the F / V converter, a DC removal filter connected to the A / D converter to remove a DC component by digital processing, and a DC removal filter A fundamental RMS value calculator, a DC effective value calculator connected to the A / D converter in parallel with the DC rejection filter, and A in parallel with the DC rejection filter. It has a detection unit that is connected to the / D conversion unit and detects the signal “None” from the feeder, and the communication line disconnection monitoring signal, the bit string for monitoring the remaining battery level, and the fault current waveform in one optical cable And send it to the detector for separation.
A ground fault detection device.   2. The ground fault detection device according to claim 1, wherein the DC superimposing unit transmits the entire waveform information by adding and shifting the DC component to the waveform of the fault current. In the V / F converter of the feeder, the entire waveform information of the fault current is transmitted to the detector side as a frequency signal of f ₁ ± f _n kHz (kHz is a unit of kilohertz), and the DC superimposition is f _1. 2. The ground fault detection device according to claim 1, wherein when a ground fault occurs, the AC component is transmitted on both sides of the positive and negative sides by superimposing the DC component when a ground fault occurs. The metering device transmits the DC superimposed signal f ₁ kHz as two types of durations of T ₁ ms (ms is millisecond of time unit) and T ₂ ms, and assigns T ₁ ms to logic “0”. , T ₂ ms is assigned to logic “1”, and serial transmission is performed from the feeder to the detector. The feeder further includes a battery as an auxiliary power source that is connected to the stabilized power source and applies a voltage corresponding to the DC superimposition to the DC superimposing unit, and a CPU that calculates the remaining battery level by calculation, and measures the battery voltage by the CPU. Then, the logic “0” and the logic “1” are used for a predetermined number of bits, and the remaining battery level is evaluated at a stage corresponding to the number of bits, and the bit string data is transmitted to the detector. The ground fault detection device according to claim 4, wherein the remaining battery level is detected.
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