JP7215915B2 - Insulation monitoring device and method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an insulation monitoring apparatus and method for monitoring insulation deterioration in an electric line having a plurality of branch circuits in a circuit configuration in which the secondary electric line of a transformer is ungrounded in an ungrounded power distribution system.

In the ungrounded power distribution system in which the secondary side of the transformer is ungrounded, a closed circuit is not formed even if the insulation resistance of one phase decreases. Therefore, power supply can be ensured even in the event of a single-phase dielectric breakdown (ground fault), so power failure of the entire secondary circuit of the transformer can be avoided. This ungrounded power distribution system can prevent a power outage in the entire secondary circuit of the transformer in the event of a single-phase ground fault, but in the event of a two-phase ground fault, a current that will cause an overcurrent circuit breaker to operate will flow and cut off. Since there is a possibility that the equipment will operate and the circuit will lose power, an insulation monitoring device is installed to monitor the deterioration of the insulation of the electric circuit.

As an insulation monitoring device, there is a device capable of detecting leakage current in each feeder of a power distribution facility composed of a plurality of banks and a plurality of feeders branching from each bank (for example, Patent Document 1). In addition, there is a technique that enables monitoring of which branch circuit of the branch circuit branched from the main circuit has deteriorated in insulation (for example, see Patent Document 2 and Patent Document 3).

JP 2007-285929 A JP-A-2005-195528 JP 2012-42417 A

However, in conventional insulation monitoring devices for non-grounded power distribution systems, the leakage current flowing in the secondary circuit of a transformer is very small, for example 0.14 mA, and the current sensor capable of detecting this leakage current is highly sensitive. necessary. This is because the leakage current detected by the current sensor is required to calculate the insulation resistance of the secondary circuit of the transformer.

On the other hand, the current sensor detects the leakage current of the feeder as a voltage value, but since it detects by amplifying a weak signal that is likely to be buried in noise, the output voltage of the current sensor changes over time. Further, the output voltage of the current sensor is subject to fluctuation due to changes in the ambient temperature and the ambient magnetic field due to the characteristics of the constituent materials and the substrate semiconductor, which affects the true value as an error.

FIG. 9 is a graph of the variation included in the output voltage of the current sensor that affects the measurement accuracy of the measured voltage of the current sensor, and FIG. Graph, FIG. 9(b) is a graph of the variation due to the influence of the ambient temperature contained in the output voltage of the current sensor, and FIG. 9(c) is a graph of the variation due to the influence of the ambient magnetic field contained in the output voltage of the current sensor. be.

As shown in FIG. 9(a), the output voltage of the current sensor amplifies and detects weak signals that are likely to be buried in noise, so the output voltage of the current sensor constantly changes and fluctuates over time. do. FIG. 9(a) shows a case where the variation width is 0.39V. Further, as shown in FIG. 9(b), the output voltage of the current sensor includes fluctuation due to the ambient temperature. FIG. 9(b) shows a case where the variation width is 1.63V. Furthermore, as shown in FIG. 9(c), the output voltage of the current sensor includes fluctuation due to the influence of the surrounding magnetic field. "Before energization" in Fig. 9(c) is the output voltage of the current sensor before the load current is energized to the secondary circuit, and "During energization" in Fig. 9(c) is the load current to the secondary circuit. The output voltage of the current sensor when energized, and "after energization" in FIG. 9(c) is the output voltage of the current sensor when the load current is stopped after energizing the secondary electric circuit. FIG. 9(c) shows a case where the variation width is 0.38V.

As described above, the leakage current flowing in the secondary circuit of the transformer is very small, and the temporal fluctuations contained in the output voltage of the current sensor and the fluctuations due to changes in the ambient temperature and magnetic field It affects the output voltage of the sensor and reduces the measurement accuracy of leakage current. Therefore, the leakage current cannot be detected with high accuracy, and it is difficult to improve the accuracy of calculating the insulation resistance and identifying the location of insulation deterioration. As the elapsed time increases, errors in the output voltage of the current sensor from the true value increase due to temporal fluctuations and fluctuations due to changes in ambient temperature and magnetic field.

SUMMARY OF THE INVENTION An object of the present invention is to provide an insulation monitoring device and method that can accurately identify the location of insulation deterioration in the secondary circuit of a transformer of an ungrounded distribution system and can detect the insulation resistance of the insulation deterioration location with high accuracy. It is to be.

The insulation monitoring device according to the first aspect of the invention comprises a superimposed measurement unit that applies a superimposed voltage to an electric circuit having a plurality of feeders in a main circuit drawn from the secondary side of a transformer of an ungrounded distribution system, and a superimposed voltage. A monitoring and measuring unit that measures the leakage current of the feeder caused by the Equipped with a current sensor that detects the voltage value and inputs it to the monitoring and measuring unit, and a panel computer that controls the operation of the monitoring and measuring unit, records and displays data from the monitoring and measuring unit, and transmits and receives data to and from the central monitoring device. In the measurement unit, the implementation time for measuring and monitoring the insulation resistance of the electric circuit and the stop time for not performing measurement and monitoring are periodically set in advance, and the superimposed voltage is applied to the electric circuit during the implementation time, and at each predetermined measurement time Detects the leakage current of the electric circuit and calculates the insulation resistance for each measurement time. When the insulation resistance is below the threshold value, the insulation deterioration is reported, the superimposed voltage is calibrated during the stop time, and the current measurement unit During the stop time, the output voltage of the current sensor is measured as the zero adjustment voltage, which is the reference value of the measurement voltage of the current sensor, for a predetermined zero adjustment time. The output voltage of the current sensor is measured as the measured voltage, the voltage difference between the zero adjustment voltage and the measured voltage for each measurement time is obtained, and the installation location of the current sensor where the difference voltage is greater than the threshold is specified as the insulation deterioration location. do.

The insulation monitoring device according to the invention of claim 2 comprises a superimposed measurement unit for applying a superimposed voltage to an electric circuit having a plurality of feeders in a main circuit drawn from the secondary side of a transformer of an ungrounded distribution system, and a superimposed voltage. A monitoring and measuring unit that measures the leakage current of the feeder caused by the Equipped with a current sensor that detects the voltage value and inputs it to the monitoring and measuring unit, and a panel computer that controls the operation of the monitoring and measuring unit, records and displays data from the monitoring and measuring unit, and transmits and receives data to and from the central monitoring device. In the measurement unit, an implementation time for measuring and monitoring the insulation resistance of the electric circuit and a stop time for not performing measurement monitoring are periodically set in advance, and a break time for stopping measurement monitoring during the implementation time is set. And during the implementation time other than the rest time, apply a superimposed voltage to the electric circuit, detect the leakage current of the electric circuit for each predetermined measurement time, calculate the insulation resistance for each measurement time, and insulate when the insulation resistance is less than the threshold Deterioration is reported, measurement monitoring is suspended for the suspension time when insulation deterioration is reported, superimposed voltage is calibrated during the suspension time, and the current measurement unit performs a predetermined Measure the output voltage of the current sensor as the zero adjustment voltage, which is the reference value of the measurement voltage of the current sensor, for the zero adjustment time of , and measure the output voltage of the current sensor only during the first measurement time after detecting the zero adjustment voltage. Measure as voltage, find the voltage difference between the zero adjustment voltage and one measurement voltage measured only during the first measurement time, and specify the installation location of the current sensor where the difference voltage is greater than the threshold as the insulation deterioration location characterized by

In the insulation monitoring device according to the third aspect of the present invention, the zero adjustment voltage is set during the stop time, during which the influence of fluctuations included in the output voltage of the current sensor that affects the measurement accuracy of the voltage measured by the current sensor is small. It is characterized by measuring during the stop time of

In the insulation monitoring device according to the invention of claim 4, the influence of the fluctuation included in the output voltage of the current sensor that affects the measurement accuracy of the voltage measured by the current sensor is large. 3. The insulation monitoring device according to claim 2, wherein the execution time is set longer than that of the short time period.

The insulation monitoring method according to the invention of claim 5 comprises a superimposed measurement unit for applying a superimposed voltage to an electric circuit having a plurality of feeders in a main circuit drawn from the secondary side of a transformer of an ungrounded distribution system, and a superimposed voltage. A monitoring and measuring unit that measures the leakage current of the feeder caused by the Isolation equipped with a current sensor that detects voltage values and inputs them to the monitoring and measuring unit, and a panel computer that controls the operation of the monitoring and measuring unit, records and displays data from the monitoring and measuring unit, and transmits and receives data to and from the central monitoring device. In the insulation monitoring method for monitoring insulation deterioration of an electric circuit using a monitoring device, the superimposed measurement unit calibrates the superimposed voltage during a stop time during which measurement and monitoring of the insulation resistance of the electric circuit is not performed periodically. , When the execution time for measuring and monitoring the insulation resistance of the electric circuit set in advance periodically or when there is a command to apply the superimposed voltage from the current measurement unit, the superimposed voltage is applied to the electric circuit, and every predetermined measurement time Then, the leakage current of the electric circuit is detected, and the insulation resistance is calculated for each measurement time based on the superimposed voltage and leakage current. When the insulation resistance is less than the threshold value, the insulation deterioration is reported, and the current measurement unit Before the start, the output voltage of the current sensor is measured for the zero adjustment time as the zero adjustment voltage, which is the reference value of the measurement voltage of the current sensor. Output the command, measure the output voltage of the current sensor as the measurement voltage for each measurement time in a state where the superimposed voltage is applied to the electric circuit, obtain the voltage difference between the zero adjustment voltage and the measurement voltage for each measurement time, and calculate the difference The method is characterized in that a location where a current sensor having a voltage higher than a threshold value is specified as an insulation deterioration location.

The insulation monitoring method according to the invention of claim 6 includes a superimposed measurement unit for applying a superimposed voltage to an electric circuit having a plurality of feeders in a main circuit drawn from the secondary side of a transformer of an ungrounded distribution system, and a superimposed voltage. A monitoring and measuring unit that measures the leakage current of the feeder caused by the Isolation equipped with a current sensor that detects voltage values and inputs them to the monitoring and measuring unit, and a panel computer that controls the operation of the monitoring and measuring unit, records and displays data from the monitoring and measuring unit, and transmits and receives data to and from the central monitoring device. In the insulation monitoring method for monitoring insulation deterioration of an electric circuit using a monitoring device, the superimposed measurement unit calibrates the superimposed voltage during a stop time during which measurement and monitoring of the insulation resistance of the electric circuit is not performed periodically. , When the execution time for measuring and monitoring the insulation resistance of the electric circuit set in advance periodically or when there is a command to apply the superimposed voltage from the current measurement unit, the superimposed voltage is applied to the electric circuit, and every predetermined measurement time Then, the leakage current of the circuit is detected, and the insulation resistance is calculated for each measurement time based on the superimposed voltage and leakage current. When measurement monitoring is paused for a preset rest time , the current measurement unit performs the predetermined zero adjustment time before the start of the implementation time or when there is an insulation deterioration report from the superimposition measurement unit. The output voltage of the current sensor is measured as the zero adjustment voltage, which is the reference value of the measurement voltage of the current sensor, and the superimposition voltage application command is output to the superimposition measurement unit during the implementation time after measuring the zero adjustment voltage, and the electric circuit The output voltage of the current sensor is measured as the measurement voltage only at the first measurement time in a state where the superimposed voltage is applied to the zero adjustment voltage and the one measurement voltage measured only at the first measurement time. is obtained, and the location where the current sensor is installed where the differential voltage is greater than the threshold is specified as the insulation deterioration location.

According to the invention of claim 1, the insulation resistance of the electric circuit is calculated based on the superimposed voltage and the leakage current during the execution time, and when the insulation resistance is equal to or less than the threshold value, the insulation deterioration is reported. It is possible to detect that insulation deterioration has occurred in the secondary side electric circuit. Moreover, since the superimposed voltage is corrected during the stop time, the leakage current can be detected with high accuracy, and the accuracy of calculation of the insulation resistance can be improved. During the stop time, the output voltage of the current sensor is measured for a predetermined zero adjustment time as the zero adjustment voltage, which is the reference value of the measurement voltage of the current sensor, and this zero adjustment voltage and the measurement voltage measured at each subsequent measurement time are combined. The installation location of the current sensor where the voltage difference between is greater than the threshold is specified as the insulation deterioration location. Therefore, the zero adjustment voltage, which is the reference value of the voltage measured by the current sensor, is updated each time the stop time is reached. It is possible to identify the location of insulation deterioration with a measured voltage that is less affected by fluctuations due to changes in temperature and the surrounding magnetic field. As a result, it becomes possible to narrow down the range of power outages in the secondary circuit of the transformer, and to greatly shorten the power outage recovery work.

According to the invention of claim 2, when there is an alarm of insulation deterioration in the invention of claim 1, the measurement and monitoring are suspended for the suspension time, the zero adjustment voltage is measured during the suspension time and the suspension time, and the zero adjustment is performed. After detecting the voltage, measure the output voltage of the current sensor as the measured voltage only at the first measurement time, and obtain the voltage difference between the zero adjustment voltage and the one measurement voltage measured only at the first measurement time. , the installation location of the current sensor whose differential voltage is greater than the threshold is specified as the insulation deterioration location. Therefore, the zero adjustment voltage, which is the reference value of the voltage measured by the current sensor, is updated every stop time and rest time, and the voltage measured by the current sensor immediately after updating the zero adjustment voltage is used. It is possible to specify the location of insulation deterioration with a measured voltage that reduces the effects of temporal fluctuations contained in the output voltage of the current sensor that affect measurement accuracy and fluctuations due to changes in the ambient temperature and magnetic field. As a result, it becomes possible to narrow down the range of power outages in the secondary circuit of the transformer, and to greatly shorten the power outage recovery work.

According to the invention of claim 3, in addition to the effect of the invention of claim 2, the influence of fluctuations included in the output voltage of the current sensor that affects the measurement accuracy of the voltage measured by the current sensor during the stop time is small. Since the zero adjustment voltage is measured during the stop time of the time slot, it is possible to further improve the accuracy of the zero adjustment voltage, which is the reference value of the voltage measured by the current sensor.

According to the invention of claim 4, in addition to the effect of the invention of claim 2, the execution time of the time period when the influence of the fluctuation included in the output voltage of the current sensor that affects the measurement accuracy of the measured voltage of the current sensor is large. is set to be longer than the execution time in the time period when the influence of the fluctuation is small, it is possible to avoid updating the zero adjustment voltage in the time period when the influence of the fluctuation is large.

According to the fifth aspect of the invention, the superimposed measurement unit calibrates the superimposed voltage during a period of stop time during which the measurement and monitoring of the insulation resistance of the electric circuit is not performed periodically. Therefore, the leakage current can be accurately measured. It can be detected and the accuracy of calculation of insulation resistance can be improved. In addition, when the execution time comes or when there is a command to apply the superimposed voltage from the current measurement unit, the superimposed voltage is applied to the electric circuit, and the leakage current of the electric circuit is detected at each predetermined measurement time to detect the superimposed voltage and the leakage current. Based on this, the insulation resistance is calculated for each measurement time, and when the insulation resistance is equal to or less than the threshold value, the insulation deterioration is reported, so it is possible to detect that the insulation deterioration has occurred in the secondary circuit of the transformer.

In addition, the current measurement unit measures the output voltage of the current sensor for the zero adjustment time before the start of the implementation time as the zero adjustment voltage which is the reference value of the measurement voltage of the current sensor, and in the state where the superimposed voltage is applied to the electric circuit The output voltage of the current sensor is measured as the measurement voltage for each measurement time, and the installation location of the current sensor where the voltage difference between the zero adjustment voltage and the measurement voltage for each measurement time is greater than the threshold is specified as the insulation deterioration location. Therefore, since the zero-adjustment voltage is updated each time the stop time is reached, the temporal fluctuations included in the output voltage of the current sensor that affect the measurement accuracy of the voltage measured by the current sensor, fluctuations due to changes in the ambient temperature and magnetic field, etc. It is possible to identify the location of insulation deterioration with the measured voltage that reduces the influence of the minute. As a result, it becomes possible to narrow down the range of power outages in the secondary circuit of the transformer, and to greatly shorten the power outage recovery work.

According to the sixth aspect of the invention, the superimposed measurement unit calibrates the superimposed voltage during a period of stop time during which the measurement and monitoring of the insulation resistance of the electric circuit is not performed. It can be detected and the accuracy of calculation of insulation resistance can be improved. When the execution time for measuring and monitoring the insulation resistance of the electric circuit set in advance periodically or when there is a command to apply the superimposed voltage from the current measurement unit, the superimposed voltage is applied to the electric circuit, and at each predetermined measurement time It detects the leakage current in the circuit and calculates the insulation resistance for each measurement time based on the superimposed voltage and leakage current. It can detect the occurrence of insulation deterioration.

In addition, the current measurement unit pauses measurement monitoring for the pause time when there is an insulation deterioration report, and before the predetermined zero adjustment time before the start of the implementation time or when the superimposition measurement unit issues an insulation deterioration report. The output voltage of the current sensor is measured for a predetermined zero adjustment time as the zero adjustment voltage, which is the reference value of the measured voltage of the current sensor. is measured as the measured voltage, and the installation location of the current sensor where the difference voltage between the zero adjustment voltage and one measured voltage measured only in the first measurement time is greater than the threshold is specified as the insulation deterioration location. Therefore, the zero adjustment voltage is updated every stop time and rest time, and the measured voltage of the current sensor immediately after updating the zero adjustment voltage is used. It is possible to specify the location of insulation deterioration with the measured voltage that reduces the influence of the temporal fluctuations contained in , and the fluctuations due to changes in the ambient temperature and the surrounding magnetic field. As a result, it becomes possible to narrow down the range of power outages in the secondary circuit of the transformer, and to greatly shorten the power outage recovery work.

1 is a configuration diagram of an insulation monitoring device according to a first embodiment of the present invention; FIG. 4 is a time chart showing an example of the operation of the monitoring and measuring unit of the insulation monitoring device according to the first embodiment of the present invention shown in FIG. 1; FIG. 4 is an explanatory diagram of how to detect a leakage current of a current sensor in a current measuring unit; The block diagram of the insulation monitoring apparatus which concerns on 2nd Embodiment of this invention. 5 is a time chart showing an example of the operation of the monitoring and measuring unit 16 of the insulation monitoring device according to the second embodiment of the present invention shown in FIG. 4; 5 is a time chart showing another example of the operation of the monitoring and measuring unit 16 of the insulation monitoring device according to the second embodiment of the present invention shown in FIG. 4; FIG. 11 is a flow chart showing processing contents of an insulation monitoring method according to a third embodiment of the present invention; FIG. The flowchart which shows the processing content of the insulation monitoring method which concerns on 4th Embodiment of this invention. Graph of variation included in the output voltage of the current sensor that affects the measurement accuracy of the measured voltage of the current sensor.

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram of an insulation monitoring device according to a first embodiment of the present invention. There are two types of insulation monitoring devices for non-grounded distribution systems: one that superimposes alternating current (low frequency) on the electric circuit to be monitored, and the other that superimposes direct current. FIG. 1 shows an example of an insulation monitoring device that superimposes a direct current, which is not affected by ground capacitance, on the secondary-side electric line of a transformer 11 to be monitored and monitors the location of insulation deterioration in the secondary-side electric line. .

In FIG. 1, power is supplied from an AC power supply 12 on the primary side of a transformer 11 of an ungrounded power distribution system to a main circuit 13 on the secondary side electric circuit. A plurality of feeders 14 are drawn from the main circuit 13, and FIG. 1 shows that two feeders 14a and 14b are drawn and loads 15a and 15b are connected to the feeders 14a and 14b, respectively.

The insulation monitoring device includes a monitoring and measuring unit 16 for monitoring insulation deterioration of the electric circuit, current sensors 17a and 17b for detecting leak currents in the feeders 14a and 14b, respectively, and a panel for recording and displaying operation control and data of the monitoring and measuring unit 16. computer 18. The monitoring and measuring unit 16 has a superimposed measurement unit 19 and a current measurement unit 20. A superimposed voltage Vt is applied from the superimposed measurement unit 19 to the secondary electric circuit, and the insulation resistance Rg of the entire secondary electric circuit is measured from the leakage current Ig. Monitor the required insulation deterioration. On the other hand, the current sensors 17a and 17b detect the leak current Ig as a voltage value, and the current measurement unit 20 monitors insulation deterioration based on the leak current Ig of the feeder 14 detected by the current sensors 17a and 17b.

The superimposed measurement unit 19 of the monitoring and measurement unit 16 includes a DC power supply 22 for applying a DC superimposed voltage Vt to the secondary electric circuit, a switch 23a for grounding the DC power supply 22, and an internal resistor Ro. A voltmeter 24 that is connected to and detects a leakage current Ig flowing in the secondary electric circuit with the application of the superimposed voltage Vt by converting it into a voltage, and a series circuit of a DC power supply 22 and an internal resistor Ro, a reference resistor Rr and a switch 23b are connected in parallel, and the insulation resistance Rg of the secondary electric circuit is adjusted based on the superimposed voltage Vt and the leakage current Ig of the voltage value detected by the voltmeter 24. and an insulation deterioration alarm unit 26 that alarms insulation deterioration when the insulation resistance Rg calculated by the insulation resistance calculator 25 is equal to or less than a threshold value RL.

The insulation resistance calculation unit 25 has an execution time T1 for measuring and monitoring the insulation resistance Rg of the secondary electric circuit and a stop time T2 for not performing measurement and monitoring, which are set periodically in advance. Then, the insulation resistance calculator 25 closes the switch 23a at the implementation time T1 to apply the superimposed voltage Vt from the DC power supply 22 to the secondary electric circuit. That is, the insulation resistance calculation unit 25 calculates the insulation resistance Rg of the secondary electric circuit based on the superimposed voltage Vt and the leakage current Ig of the voltage value detected by the voltmeter 24 at the implementation time T1. The insulation resistance Rg of the secondary electric circuit is output to the panel computer 18 . The open/closed state of the switch 23 a is output from the insulation resistance calculation section 25 to the zero adjustment voltage detection section 27 of the current measurement unit 20 of the monitoring measurement unit 16 . The insulation deterioration alarm unit 26 alarms insulation deterioration when the insulation resistance Rg calculated by the insulation resistance calculation unit 25 is equal to or less than the threshold RL during the execution time T1, and the insulation resistance Rg exceeds the threshold RL. Stops the alarm when The alarm issued by the insulation deterioration alarm unit 26 is output to the panel computer 18 .

The switch 23b of the superimposed voltage calibration unit 32 is closed when the switch 23a is open, and is opened when the switch 23a is closed. In other words, the superimposed voltage calibration unit 32 calibrates the superimposed voltage Vt during the stop time T2 during which the measurement and monitoring of the insulation resistance Rg are not performed. A series circuit of the resistor Ro and the reference resistor Rr is formed. The insulation resistance calculator 25 stores the voltage value of the internal resistance Ro at this time as a reference value voltage of the leakage current Ig, and corrects the actually detected leakage current Ig based on the reference value voltage.

Next, the current measurement unit 20 of the monitoring measurement unit 16 measures the output voltages of the current sensors 17a and 17b as the zero adjustment voltage V0 which is the reference value of the measurement voltage Vs of the current sensors 17a and 17b. A superimposed voltage application unit 28 that outputs a command to apply a superimposed voltage Vt to the secondary electric circuit to the DC power supply 22 of the superimposed measurement unit 19, and the output voltages of the current sensors 17a and 17b are measured every predetermined measurement time. It has a continuous voltage measuring unit 29 that measures the voltage Vs and an insulation deterioration point determination unit 30 that identifies an insulation deterioration point.

The zero adjustment voltage detector 27 acquires from the insulation resistance calculator 25 the stop time T2 during which the switch 23a of the superposition measurement unit 19 is open. Then, the zero adjustment voltage detection section 27 detects the output voltages of the current sensors 17a and 17b for a predetermined zero adjustment time T3 during the stop time T2 during which the switch 23a of the superposition measurement unit 19 is open. It is measured as a zero adjustment voltage V0, which is a reference value of Vs, and is output to the insulation deterioration point determination section 30. FIG. After the zero adjustment voltage detection unit 27 detects the zero adjustment voltage V0, the superimposed voltage application unit 28 instructs the DC power supply 22 of the superimposed measurement unit 19 to apply the superimposed voltage Vt to the secondary electric circuit ( command to close the switch 23a).

The continuous voltage measurement unit 29 measures the output voltage of the current sensors 17a and 17b as the measurement voltage Vs every predetermined measurement time while the DC power supply 22 of the superimposition measurement unit 19 is applying the superimposition voltage Vt to the secondary electric circuit. measure. The insulation deterioration point determination unit 30 calculates the voltage difference ΔV between the zero adjustment voltage V0 and the measured voltage Vs, and specifies the installation points of the current sensors 17a and 17b where the voltage difference ΔV is greater than the threshold value VL as the insulation deterioration point. This voltage difference ΔV represents the leakage current Ig as a voltage value. This is because the zero adjustment voltage V0, which is the reference value of the measured voltage Vs of the current sensors 17a and 17b, is the measured voltage Vs of the output voltages of the current sensors 17a and 17b when the superimposed voltage Vt is not applied. . That is, the voltage difference ΔV between the measured voltage Vs and the zero adjustment voltage V0 when the superimposed voltage Vt is applied is the leakage current Ig represented by a voltage value. The insulation deterioration location specified by the insulation deterioration location determination unit 30 is output to the panel computer 18 .

Assume now that insulation deterioration has occurred at the insulation deterioration location 21 of the feeder 14b in FIG. When the superimposed measurement unit 19 measures and monitors the insulation resistance Rg of the secondary circuit of the transformer 11, the insulation resistance calculator 25 of the superimposed measurement unit 19 closes the switch 23a at the measurement and monitoring implementation time T1, and the internal This is done by applying a superimposed voltage Vt (eg, 20 V) to the electric circuit from a DC power source 22 connected in series with a resistor Ro (eg, 40 kΩ). When the superimposed measurement unit 19 applies the superimposed voltage Vt to the secondary electric path of the transformer 11, the superimposed measurement unit 19→ground (earth)→insulation degradation point 21→feeder 14b→main circuit 13→transformer 11→superimposed measurement unit. Nineteen closed circuits are formed. If the insulation deteriorates to, for example, 100 kΩ at the insulation deterioration point 21 of the feeder 14b, the leakage current Ig is obtained by adding the superimposed voltage Vt (for example, 20 V) to the internal resistance Ro (40 kΩ) and the insulation resistance of 100 kΩ at a resistance value of 140 kΩ. Calculated by division. The leak current Ig at this time is 0.14 mA. This leakage current Ig is detected by the current sensor 17b and input to the current measurement unit 20. FIG. The current measurement unit 20 determines insulation deterioration based on this leakage current Ig.

FIG. 2 is a time chart showing an example of the operation of the monitoring and measuring unit 16 of the insulation monitoring device according to the first embodiment shown in FIG. The superimposition measurement unit 19 of the monitoring measurement unit 16 performs measurement monitoring of the insulation resistance Rg of the secondary side electric circuit of the transformer 11 at predetermined time intervals. That is, the measurement monitoring implementation time T1 and the stop time T2 are repeated periodically (for example, every 30 minutes). Now, when the measurement monitoring stop time T2 starts at time t1, the insulation resistance calculator 25 of the superimposed measurement unit 19 opens the switch 23a to stop applying the superimposed voltage Vt to the secondary circuit of the transformer 11. At the same time, measurement monitoring also stops. On the other hand, as the switch 23a is opened, the switch 23b is closed and the superimposed voltage calibrator 32 operates to correct the superimposed voltage Vt during the stop time T2.

At time t2, which is a predetermined time before the start of the implementation time T1 during the stop time T2, the zero adjustment voltage detection section 27 of the current measurement unit 20 operates the current sensor for a predetermined zero adjustment time T3 from time t2 to time t3. The output voltages of 17a and 17b are measured as a zero adjustment voltage V01 to perform so-called zero adjustment of the current sensors 17a and 17b. The zero adjustment voltage V01 is the measured voltage Vs of the output voltages of the current sensors 17a and 17b when the superimposed voltage Vt is not applied, and is the reference value of the measured voltage Vs of the current sensors 17a and 17b.

At time t3, when the zero adjustment of the current sensors 17a and 17b is completed, the superimposed voltage applying section 28 instructs the DC power supply 22 of the superimposed measurement unit 19 to apply the superimposed voltage Vt to the secondary electric circuit (superimposition measurement unit 19 command to close the switch 23a). As a result, the superimposed voltage Vt is applied to the secondary electric path of the transformer 11, and the continuous voltage measurement unit 29 detects the current sensor 17a at a constant cycle (sampling cycle) after time t4 after a predetermined time T4 has elapsed from time t3. , 17b is measured as the measurement voltage Vs. The predetermined time T4 is the time from the application of the superimposed voltage Vt until the leakage current Ig of the electric circuit can be stably measured.

That is, the continuous voltage measurement unit 29 measures the output voltages of the current sensors 17a and 17b every predetermined measurement time while the DC power supply 22 of the superimposition measurement unit 19 is applying the superimposed voltage Vt to the secondary electric circuit. Measure as Vs. For example, when the predetermined measurement time is 1 s, the average value of a plurality of measured voltage data obtained during the 1 s is used as the measured voltage for the predetermined period. If the execution time is 20 minutes, 60×20 (=1200) measured voltages Vs are obtained.

The leakage current Ig in the secondary circuit caused by the superimposed voltage is obtained by subtracting the zero adjustment voltage V01, which is the reference value of the measured voltage Vs of the current sensors 17a and 17b, from the measured voltage Vs measured by applying the superimposed voltage Vt. . This is because, as described above, the zero adjustment voltage V01, which is the reference value of the voltage Vs measured by the current sensors 17a and 17b, is the output voltage of the current sensors 17a and 17b when the superimposed voltage Vt is not applied. . As a result, the influence of temporal fluctuations included in the output voltages of the current sensors 17a and 17b and fluctuations due to changes in the ambient temperature and the ambient magnetic field are reduced.

Next, the insulation resistance calculator 25 of the superimposed measurement unit 19 calculates the superimposed voltage Vt and the voltmeter 24 at every predetermined measurement time after the time t4 after a predetermined time T4 has elapsed from the time t3 when the implementation time T1 starts. Based on the leakage current Ig of the detected voltage value, the insulation resistance Rg of the secondary electric circuit is calculated by the following equation (1). Ro is an internal resistance connected in parallel with the voltmeter 24 .

Rg=Vt/Ig−Ro (1)
The insulation resistance Rg calculated by the insulation resistance calculator 25 is output to the panel computer 18 and recorded and displayed as described above.

In addition, the insulation deterioration alarm unit 26 of the superimposition measurement unit 19 compares the calculated insulation resistance Rg with a predetermined threshold RL, and when the calculated insulation resistance Rg becomes equal to or less than the predetermined threshold RL, a predetermined At a time ta after the time limit, an alarm is issued that the secondary circuit of the transformer 11 has insulation deterioration. stop reporting. The reason why the predetermined time limit is given is to prevent repeated start and stop of the alarm.

On the other hand, the insulation deterioration point determining section 30 of the current measuring unit 20 calculates the voltage difference ΔV between the zero adjustment voltage V01 and the measured voltage Vs after the time t4 after a predetermined time T4 has elapsed from the time t3, and calculates the voltage difference ΔV. is larger than the threshold value VL, the installation locations of the current sensors 17a and 17b are specified as insulation deterioration locations. The insulation deterioration location specified by the insulation deterioration location determination unit 30 is output to the panel computer 18. Then, when the measurement monitoring implementation time T1 ends at time t11 and the stop time T2 starts, from time t11 to time t14 , the same operations as those from time t1 to time t4 described above are repeated. Note that the zero adjustment voltage V01 detected at time t3 and the zero adjustment voltage V02 detected at time t13 are different values between time t3 and time t13 due to temporal fluctuations, ambient temperature, and ambient magnetic field. becomes.

As described above, in the insulation monitoring device according to the first embodiment of the present invention shown in FIG. During the stop time T2, the application of the superimposed voltage Vt to the secondary-side electric circuit of the transformer 11 is stopped, and the superimposed voltage Vt is calibrated during the stop time T2. On the other hand, in the current measurement unit 20, the current sensors 17a and 17b are zero-adjusted during the stop time T2 when the superimposed voltage Vt is stopped, and the zero-adjustment voltage V01 is obtained. and the zero adjustment voltage V0.

FIG. 3 is an explanatory diagram of how the leakage current Ig of the current sensors 17a and 17b in the current measurement unit 20 is detected. The output voltages of the current sensors 17a and 17b during zero adjustment, that is, the current measurement unit 20 measures the output voltages of the current sensors 17a and 17b when the superimposition measurement unit 19 does not apply the superimposed voltage Vt to the secondary electric circuit. Measured as the zero adjustment voltage V0, which is the reference value of the measured voltage Vs of the current sensor, and measured as the measured voltage Vs is the output voltage of the current sensors 17a and 17b when the superimposed voltage Vt is applied to the secondary electric circuit. Then, the voltage difference ΔV (=Vs−V0) between the zero adjustment voltage V0 and the voltage Vs measured by the current sensors 17a and 17b when the superimposed voltage Vt is applied to the secondary electric circuit is the leakage current Ig flowing through the secondary electric circuit. Detect as

According to the first embodiment, the superimposed voltage Vt is applied to the secondary circuit of the transformer 11, the leakage current Ig flowing in the secondary circuit of the transformer 11 is converted into a voltage, and the voltage of the superimposed measurement unit 19 is Detected by the total 24, the insulation resistance Rg of the electric circuit is calculated based on the superimposed voltage Vt and the leakage current Ig. It is possible to detect that insulation deterioration has occurred in the secondary side electric circuit. Further, since the superimposed voltage Vt is corrected during the stop time T2, the leakage current Ig can be detected with high accuracy, and the accuracy of calculation of the insulation resistance Rg can be improved. The output voltages of the current sensors 17a and 17b are measured as the zero adjustment voltage V0, which is the reference value of the measured voltage Vs of the current sensors 17a and 17b, for a predetermined zero adjustment time T3 during the stop time T2 during which measurement monitoring is not performed. A voltage difference ΔV between the adjusted voltage V0 and the measured voltage Vs measured at each subsequent measurement time is obtained, and the installation locations of the current sensors 17a and 17b where the voltage difference ΔV is greater than the threshold value VL are identified as insulation deterioration locations.
Therefore, the zero adjustment voltage V0, which is the reference value of the voltage Vs measured by the current sensors 17a and 17b, is updated every stop time T2. , 17b, and the measurement voltage Vs that reduces the influence of the fluctuation due to changes in the ambient temperature and the ambient magnetic field. As a result, it becomes possible to narrow down the power failure range of the secondary electric circuit of the transformer 11, and the power failure restoration work can be greatly shortened.

Next, a second embodiment of the invention will be described. FIG. 4 is a configuration diagram of an insulation monitoring device according to a second embodiment of the present invention. This second embodiment is different from the first embodiment shown in FIG. An intermittent voltage measurement unit 31 is provided instead of the . That is, the insulation resistance calculation unit 25 detects the leakage current Ig of the electric circuit for each predetermined measurement time during the execution time T1 other than the stop time T2 and the rest time Tx, calculates the insulation resistance Rg for each measurement time, The adjustment voltage detection unit 27 adjusts the output voltages of the current sensors 17a and 17b to the zero adjustment voltage V0 which is the reference value of the measured voltage Vs of the current sensors 17a and 17b for a predetermined zero adjustment time T3 during the stop time T2 and the rest time Tx. , the intermittent voltage measurement unit 31 measures the output voltages of the current sensors 17a and 17b as the measurement voltage Vs only at the first measurement time T5 after detecting the zero adjustment voltage V0, and the insulation deterioration location determination unit A reference numeral 30 specifies, as an insulation deterioration location, the installation locations of the current sensors 17a and 17b where the voltage difference ΔV between the zero adjustment voltage V0 and one measurement voltage Vs measured only at the first measurement time T5 is greater than the threshold value VL. It is designed to The same elements as those in FIG. 1 are denoted by the same reference numerals, and overlapping descriptions are omitted.

In FIG. 4, the insulation resistance calculation unit 25 of the monitoring and measuring unit 16 calculates an execution time T1 for performing measurement monitoring of the insulation resistance Rg of the secondary electric circuit preset periodically and a stop time T2 for not performing measurement monitoring. and further has a pause time Tx for pausing measurement monitoring during the implementation time T1. Then, the insulation resistance calculator 25 closes the switch 23 and applies the superimposed voltage Vt from the DC power supply 22 to the secondary electric circuit during the stop time T2 or the execution time T1 other than the rest time Tx. That is, the insulation resistance calculation unit 25 calculates the insulation resistance of the secondary electric circuit based on the superimposed voltage Vt and the leakage current Ig of the voltage value detected by the voltmeter 24 during the execution time T1 other than the stop time T2 or the rest time Tx. Rg will be calculated.

When the insulation resistance Rg calculated by the insulation resistance calculator 25 is equal to or less than the threshold value RL during the execution time T1, the insulation deterioration alarm unit 26 notifies that the insulation is deteriorated. Then, the switch 23a is opened to set the pause time Tx for measurement and monitoring. The alarm is stopped when the insulation resistance Rg exceeds the threshold RL. The pause time Tx is a predetermined time. The alarm issued by the insulation deterioration alarm unit 26 is output to the panel computer 18 . The superimposed voltage calibration unit 32 calibrates the superimposed voltage Vt during the stop time T2 when the switch 23b is closed. The insulation resistance calculator 25 stores the voltage value of the internal resistance Ro at this time as a reference value voltage of the leakage current Ig, and corrects the actually detected leakage current Ig based on the reference value voltage.

The zero adjustment voltage detection unit 27 of the current measurement unit 20 acquires the stop time T2 or the pause time Tx during which the switch 23a of the superposition measurement unit 19 is open from the insulation resistance calculation unit 25, and determines the stop time T2 during which the switch 23a is open and The output voltage of the current sensors 17a and 17b is measured as the reference value of the measured voltage Vs of the current sensors 17a and 17b for a predetermined zero adjustment time T3 during the pause time Tx as the zero adjustment voltage V0, and is output to the insulation deterioration point determination unit 30. do.

After the zero adjustment voltage detection unit 27 detects the zero adjustment voltage V0, the superimposed voltage application unit 28 instructs the DC power supply 22 of the superimposed measurement unit 19 to apply the superimposed voltage Vt to the secondary electric circuit ( command to close the switch 23). As a result, the intermittent voltage measurement unit 31 detects the zero adjustment voltage V0, and the DC power supply 22 of the superposition measurement unit 19 is applying the superposition voltage Vt to the secondary electric circuit. Only at T5, the output voltages of the current sensors 17a and 17b are measured as the measurement voltage Vs. The insulation deterioration point determination unit 30 obtains the voltage difference ΔV between the zero adjustment voltage V0 and one measurement voltage Vs measured only at the first measurement time T5, and the current sensor 17a, 17b is specified as an insulation deterioration location. The insulation deterioration location specified by the insulation deterioration location determination unit 30 is output to the panel computer 18 .

FIG. 5 is a time chart showing an example of the operation of the monitoring and measuring unit 16 of the insulation monitoring device according to the second embodiment of the invention shown in FIG. The superimposed measurement unit 19 of the monitoring measurement unit 16 periodically repeats measurement monitoring of the insulation resistance Rg of the secondary side electric circuit of the transformer 11 between the execution time T1 and the stop time T2. When the insulation deterioration reporting unit 26 issues an insulation deterioration report during the execution time T1, a suspension time Tx is provided during which measurement and monitoring of the insulation resistance Rg of the secondary circuit of the transformer 11 is suspended. .

In FIG. 5, when the measurement monitoring stop time T2 starts at time t1, the insulation resistance calculator 25 of the superimposed measurement unit 19 opens the switch 23a, and the superimposed voltage Vt to the secondary circuit of the transformer 11 When the application is stopped, measurement monitoring is also stopped. On the other hand, as the switch 23a is opened, the switch 23b is closed and the superimposed voltage calibrator 32 operates to correct the superimposed voltage Vt during the stop time T2.

At time t2, which is a predetermined time before the start of the implementation time T1 during the stop time T2, the zero adjustment voltage detection section 27 of the current measurement unit 20 operates the current sensor for a predetermined zero adjustment time T3 from time t2 to time t3. The output voltages of 17a and 17b are measured as a zero adjustment voltage V01 to perform so-called zero adjustment of the current sensors 17a and 17b. The zero adjustment voltage V01 is the output voltage of the current sensors 17a and 17b when the superimposed voltage Vt is not applied, and is the reference value of the measured voltage Vs of the current sensors 17a and 17b. The zero adjustment voltage V01 detected by the zero adjustment voltage detection section 27 is input to the insulation deterioration point determination section 30 of the current measurement unit 20. FIG.

At time t3, when the zero adjustment of the current sensors 17a and 17b by the zero adjustment voltage detection unit 27 of the current measurement unit 20 is completed, the superimposed voltage application unit 28 of the current measurement unit 20 causes the DC power supply 22 of the superimposition measurement unit 19 to In response, a command to apply the superimposed voltage Vt to the secondary electric circuit (a command to close the switch 23 of the superimposed measurement unit 19) is output. As a result, the superimposed voltage Vt is applied to the secondary circuit of the transformer 11, and the implementation time T1 starts. After time t4 after a predetermined time T4 has elapsed from time t3 when the execution time T1 starts, the insulation resistance calculator 25 of the superposition measurement unit 19 calculates the superimposition voltage Vt and the voltage value detected by the voltmeter 24 at regular intervals. The insulation resistance Rg of the secondary-side electric circuit is calculated by the above-described equation (1) based on the leakage current Ig. The insulation resistance Rg calculated by the insulation resistance calculator 25 is output to the panel computer 18 and recorded and displayed.

On the other hand, after time t4 after the lapse of the predetermined time T4 from time t3, the intermittent voltage measurement section 31 of the current measurement unit 20 detects the voltage from time t4 to time t5 while the superimposed voltage Vt is being applied to the secondary electric circuit. The output voltages of the current sensors 17a and 17b are measured as the measurement voltage Vs for a predetermined measurement time T5 between . The measured voltage Vs is a voltage value corresponding to the leakage current Ig. Since the intermittent voltage measurement unit 31 measures the output voltages of the current sensors 17a and 17b as the measurement voltage Vs for the predetermined measurement time T5, the current sensors 17a and 17b affect the measurement accuracy of the measurement voltage Vs of the current sensors 17a and 17b. It is possible to reduce the influence of temporal fluctuations included in the output voltage of 17b and fluctuations due to changes in ambient temperature and ambient magnetic field.

A measured voltage Vs measured by the intermittent voltage measuring unit 31 for a predetermined measuring time T5 is input to the insulation deterioration point determining unit 30 of the current measuring unit 20 . The insulation deterioration point determination unit 30 calculates the voltage difference ΔV between the zero adjustment voltage V01 and the measured voltage Vs, and specifies the installation points of the current sensors 17a and 17b where the voltage difference ΔV is greater than the threshold value VL as the insulation deterioration point. Since the insulation deterioration portion determination unit 30 measures the leakage current Ig from the voltage difference ΔV of the measured voltage Vs with improved measurement accuracy and determines the insulation deterioration, the measurement accuracy of the insulation deterioration portion is improved.

Here, if the insulation deterioration reporting unit 26 of the superimposed measurement unit 19 issues an insulation deterioration report during the implementation time T1, the insulation resistance calculation unit 25 of the superimposed measurement unit 19 suspends measurement monitoring. That is, when the insulation resistance Rg calculated by the insulation resistance calculator 25 of the superimposed measurement unit 19 is equal to or less than the threshold value RL during the execution time T1, the insulation deterioration alarm unit 26 of the superimposed measurement unit 19 indicates that the insulation is deteriorated. At the same time, the switch 23a is opened via the insulation resistance calculator 25 to suspend the measurement and monitoring, and the measurement and monitoring is set to the suspension time Tx.

Suppose now that the insulation deterioration notification unit 26 of the superposition measurement unit 19 issues an insulation deterioration notification at time ta in FIG. The alerting time ta and the alerting stop time tb in FIG. 5 are the same as in the first embodiment shown in FIG. When the insulation deterioration is reported, the insulation resistance calculator 25 opens the switch 23a at time t21, stops applying the superimposed voltage Vt to the secondary electric circuit, and stops measurement and monitoring. The zero adjustment voltage detection unit 27 of the current measurement unit 20 receives an insulation deterioration notification from the insulation deterioration notification unit 26 of the superimposition measurement unit 19, and at time t22, which is a predetermined time before the end of the pause time Tx, reaches time t22. The output voltages of the current sensors 17a and 17b are measured as the zero adjustment voltage V0a for a predetermined zero adjustment time T3 from the time t23 to the point of time t23, and the result is output to the insulation deterioration point determining section 30. FIG. The superimposed voltage applying section 28 outputs a close command to the switch 23 of the superimposed measurement unit 19 after the zero adjustment voltage detection section 27 detects the zero adjustment voltage V0a.

After time t24 after the lapse of a predetermined time T4 from time t23, the intermittent voltage measurement unit 31 of the current measurement unit 20 measures the time from time t24 to time t25 while the superimposed voltage Vt is being applied to the secondary electric circuit. The output voltages of the current sensors 17a and 17b are measured as the measurement voltage Vs for a predetermined measurement time T5.

In this way, even when insulation deterioration is reported, the intermittent voltage measurement unit 31 measures the output voltages of the current sensors 17a and 17b as the measurement voltage Vs for the predetermined measurement time T5. It is possible to reduce the effects of temporal fluctuations included in the output voltages of the current sensors 17a and 17b and fluctuations due to changes in the ambient temperature and the ambient magnetic field that affect the measurement accuracy of the measured voltage Vs. Further, the insulation deterioration point determination unit 30 calculates the voltage difference ΔV between the zero adjustment voltage V0a and the measured voltage Vs, and specifies the installation points of the current sensors 17a and 17b where the voltage difference ΔV is greater than the threshold value VL as the insulation deterioration point. Therefore, since the insulation deterioration point determination unit 30 measures the leakage current Ig from the voltage difference ΔV of the measured voltage Vs with improved measurement accuracy and determines the insulation deterioration, the measurement accuracy of the insulation deterioration point is also improved.

Next, when the execution time T1 for measurement and monitoring ends at time t11 and the stop time T2 starts, the same operations as those from time t1 to time t5 described above are repeated from time t11 to time t15. It should be noted that the zero adjustment voltage V01 detected at time t3, the zero adjustment voltage V0a detected at time t23, and the zero adjustment voltage V02 detected at time t13 vary with time at time t3, time t23, and time t13. The values are different because the surrounding magnetic field is changing.

According to the insulation monitoring device of the second embodiment of the present invention, when the insulation resistance Rg of the secondary circuit of the transformer 11 is measured and monitored by the superposition measurement unit 19, the insulation resistance Rg becomes equal to or less than the threshold value RL, and insulation deterioration occurs. When there is information, the same processing (zero adjustment of the current sensors 17a and 17b, measurement of the output voltage of the current sensors 17a and 17b) is performed during the pause time Tx as during the stop time T2. Not only at the time T1, which is performed periodically, but also when insulation deterioration is reported, the location of insulation deterioration can be identified at an early stage with high accuracy.

In the current measurement unit 20, the predetermined time T4 from zero adjustment to measurement of the output voltages of the current sensors 17a and 17b should be shortened, and the predetermined measurement time T5 of the output voltages of the current sensors 17a and 17b should also be shortened. Therefore, the output voltage of the current sensors 17a and 17b after zero adjustment is measured intermittently for a short period of time. It is possible to reduce the influence of fluctuation due to changes in

Furthermore, when the insulation deterioration is reported by the superimposed measurement unit 19, the insulation deterioration location is specified by the measurement by the current measurement unit 20 and the current sensors 17a and 17b. The role of constant monitoring (insulation resistance measurement and monitoring) of the secondary electric circuit and the role of searching (intermittent monitoring) of insulation deterioration locations performed by the current measurement unit 20 and the current sensors 17a and 17b can be divided.

FIG. 6 is a time chart showing another example of the operation of the monitoring and measuring unit 16 of the insulation monitoring device according to the second embodiment of the invention shown in FIG. For the example of the operation shown in FIG. 5, the measurement of the zero adjustment voltage V0 performed during the stop time T2 affects the output voltage of the current sensors 17a and 17b, which affects the measurement accuracy of the measured voltage Vs of the current sensors 17a and 17b. This is done during the stop time T2 in the time zone where the effects of fluctuations due to changes in the ambient temperature and the surrounding magnetic field are small.

In FIG. 6, the period from time t32, which is a predetermined time before the start of the implementation time T1 after the time t31 when the measurement and monitoring stop time T2 starts, to time 33 when the implementation time T1 starts, should be the zero adjustment time T3. be. Similarly, the period from time t42, which is a predetermined time before the start of the implementation time T1 after the time t41 when the stop time T2 of the measurement and monitoring is started, to time 43 when the implementation time T1 starts is essentially the zero adjustment time T3. . In these zero adjustment times T3, the zero adjustment voltage V0 is originally measured, but in FIG. Since it is a time period in which the influence of fluctuations due to changes in the magnetic field is large, the measurement of the zero adjustment voltage V0 is omitted. Further, in FIG. 6, the zero adjustment voltage V0 is less affected by temporal fluctuations in the output voltages of the current sensors 17a and 17b and fluctuations due to changes in the ambient temperature and the ambient magnetic field (time points t11 to t13). The case of measurement is shown. It should be noted that during the rest time Tx, the zero adjustment voltage V0 cannot be measured regardless of the influence of temporal fluctuations contained in the output voltages of the current sensors 17a and 17b and fluctuations due to changes in the ambient temperature and the ambient magnetic field. conduct. Thereby, the accuracy of the zero adjustment voltage V0, which is the reference value of the voltage Vs measured by the current sensors 17a and 17b, can be further improved. A time period in which the effects of temporal fluctuations contained in the output voltages of the current sensors 17a and 17b and fluctuations due to changes in the ambient temperature and the surrounding magnetic field are less affected is, for example, nighttime. It is daytime.

In addition, the zero adjustment voltage V0 is measured during the stop time T2, which is a time period in which the effects of temporal fluctuations contained in the output voltages of the current sensors 17a and 17b and fluctuations due to changes in the ambient temperature and magnetic field are small. Instead, the execution time T1 in the time period when the influence of the fluctuation included in the output voltage of the current sensors 17a and 17b that affects the measurement accuracy of the measured voltage Vs of the current sensors 17a and 17b is large has less influence of the fluctuation. It may be made longer than the execution time T1 of the time slot. As a result, more zero adjustment voltage V0 can be measured in a time period when the influence of fluctuations is small, so that the accuracy of the zero adjustment voltage V0, which is the reference value of the voltage Vs measured by the current sensors 17a and 17b, can be further improved. can.

Next, an insulation monitoring method according to a third embodiment of the invention will be described. FIG. 7 is a flow chart showing the processing contents of the insulation monitoring method according to the third embodiment of the present invention. 7A is a flow chart showing the processing contents of the superposition measurement unit 19 shown in FIG. 1, and FIG. 7B is a flow chart showing the processing contents of the current measurement unit 20 shown in FIG.

In the insulation monitoring method according to the third embodiment of the present invention, a superimposed voltage Vt is applied to an electric line having a plurality of feeders 14 in a main circuit 13 drawn from the secondary side of a transformer 11 of an ungrounded distribution system. A monitoring and measuring unit 16 having a superimposed measurement unit 19 and a current measurement unit 20 that measures leakage current Ig of the feeder 14 caused by the superimposed voltage Vt and monitors insulation deterioration of the secondary side circuit of the transformer 11; current sensors 17a and 17b provided downstream of the branch point of the feeder 14 to detect the leakage current Ig of the feeder 14 as a voltage value and input to the monitoring and measuring unit 16; is recorded and displayed, and the insulation deterioration of the electric circuit is monitored using an insulation monitoring device provided with a panel computer 18 that transmits and receives data to and from the central monitoring device.

As shown in FIG. 7A, the superimposed measurement unit 19 first determines whether or not the stop time T2 of measurement monitoring has come (S1). Whether or not the stop time T2 has come is determined, for example, by whether or not the start time t1 of the preset stop time T2 shown in FIG. 2 has come. When the stop time T2 starts at time t1, the superimposed voltage calibration unit 32 calibrates the superimposed voltage Vt (S2). If it is determined in step S1 that the start time t1 of the stop time T2 has not come, or if the superimposed voltage Vt has been calibrated, it is determined whether or not the implementation time T1 has come (S3). When the execution time T1 has not come, it is determined whether or not there is a command to apply the superimposed voltage Vt from the current measurement unit 20 (S4). When there is no command to apply the superimposed voltage Vt from the current measuring unit 20, the process returns to step (S1).

When the execution time T1 for measurement and monitoring has arrived in step S3, or when there is a command to apply the superimposed voltage Vt from the current measuring unit 20 in the decision of step S4, the superimposed voltage Vt is applied (S5). Application of the superimposed voltage Vt to the secondary electric circuit is performed by closing the switch 23a and connecting the DC power supply 22 to the ground. As a result, when the execution time T1 for measuring and monitoring the insulation resistance Rg of the electric circuit set periodically in advance comes, or when there is a command to apply the superimposed voltage Vt from the current measurement unit 20, it is superimposed on the secondary electric circuit. A voltage Vt is applied.

After applying the superimposed voltage Vt to the secondary electric circuit, the leakage current Ig is measured (S6). Leakage current Ig is measured by applying superimposed voltage Vt to the secondary circuit, and converting leakage current Ig in the secondary circuit caused by superimposed voltage Vt into a voltage value with voltmeter 24 provided in superimposition measurement unit 19. to detect. Then, the insulation resistance Rg is calculated (S7). The calculation of the insulation resistance Rg is performed by the superimposed measurement unit 19 based on the superimposed voltage Vt and the leakage current Ig of the voltage value detected by the voltmeter 24 . After the insulation resistance Rg is calculated, it is determined whether or not the insulation resistance Rg is equal to or less than the threshold value RL (S8). If the insulation resistance Rg is not less than the threshold RL, the process returns to step S6.

On the other hand, when the insulation resistance Rg is equal to or less than the threshold value RL, the application of the superimposed voltage Vt is stopped (S9), and insulation deterioration is reported (S10). As a result, it can be seen that insulation deterioration has occurred in the secondary electric circuit. Then, it is determined whether or not the process is finished (S11). If the process is not finished, the process returns to step S1, and if the process is finished, the process is finished.

Next, as shown in FIG. 7B, the current measurement unit 20 first determines whether or not it is a predetermined time before the start time t3 of the measurement monitoring implementation time T1 (S12). Whether or not it is a predetermined time before the start time t3 of the implementation time T1 of measurement monitoring is determined by whether or not it is a predetermined zero adjustment time T3 before the start time of the implementation time T1. When it is a predetermined time before the start time t3 of the measurement monitoring implementation time T1, that is, a predetermined zero adjustment time T3 before the start time t3 of the implementation time T1, the zero adjustment voltage V0 is measured (S13). The zero adjustment voltage V0 is measured by detecting the output voltage of the current sensor for a predetermined zero adjustment time T3. As a result, the output voltages of the current sensors 17a and 17b are detected as the zero adjustment voltage V0 for a predetermined zero adjustment time T3 before the start of the implementation time T1. Then, after detecting the zero adjustment voltage V0, a command to apply the superimposed voltage Vt is output to the superimposed measurement unit 19 (S14). On the other hand, if it is determined in step S12 that it is not the predetermined time before the start time t3 of the measurement and monitoring implementation time T1, the process returns to step S12 and waits until the predetermined time before the start time t3 of the measurement and monitoring implementation time T1.

By the processing of step S14, the superimposed voltage Vt is applied to the secondary electric path. With the superimposed voltage Vt applied to the secondary electric circuit, the output voltages of the current sensors 17a and 17b are measured as the measurement voltage Vs at predetermined measurement times (S15).

Then, the voltage difference ΔV between the zero adjustment voltage V0 and the measured voltage Vs is calculated (S16), and it is determined whether or not the voltage difference ΔV is greater than the threshold value VL (S17). When the voltage difference ΔV is not larger than the threshold value VL as a result of this determination, the process returns to step S12. On the other hand, when the voltage difference ΔV is greater than the threshold value VL, the installation locations of the current sensors 17a and 17b where the voltage difference ΔV is greater than the threshold value VL are identified as insulation deterioration locations (S18). After that, it is determined whether or not the process is finished (S19). If the process is not finished, the process returns to step S12, and if the process is finished, the process is finished.

According to the third embodiment, the superimposed measurement unit 19 calibrates the superimposed voltage Vt during the stop time T2 during which the measurement and monitoring of the insulation resistance Rg of the electric circuit is periodically set in advance. Ig can be detected with high accuracy, and the accuracy of calculation of the insulation resistance Rg can be improved. When the execution time T1 for periodically measuring and monitoring the insulation resistance Rg of the electric circuit comes, or when there is a command to apply the superimposed voltage Vt from the current measurement unit 20, the superimposed voltage Vt is applied to the electric circuit, and the predetermined Insulation resistance Rg is calculated for each measurement time based on superimposed voltage Vt and leakage current Ig, and insulation deterioration is reported when insulation resistance Rg is less than threshold RL. Therefore, it is possible to detect that insulation deterioration has occurred in the secondary side electric circuit of the transformer 11 .

Further, the current measurement unit 20 measures the output voltages of the current sensors 17a and 17b for the zero adjustment time T3 before the start of the implementation time T1 as the zero adjustment voltage V0 which is the reference value of the measurement voltage Vs of the current sensors 17a and 17b, During the implementation period T1 after measuring the zero adjustment voltage V0, an application command for the superimposed voltage Vt is output to the superimposed measurement unit 19, and the current sensor 17a, The output voltage of 17b is measured as the measured voltage Vs, the voltage difference ΔV between the zero adjustment voltage V0 and the measured voltage for each measurement time is obtained, and the difference voltage ΔV is greater than the threshold value VL. Identify as a point. Therefore, since the zero adjustment voltage V0 is updated every stop time T2, the temporal fluctuations included in the output voltages of the current sensors 17a and 17b that affect the measurement accuracy of the measured voltage Vs of the current sensors 17a and 17b, The location of insulation deterioration can be identified by the measured voltage Vs that is less affected by fluctuations due to changes in the ambient temperature and the ambient magnetic field. As a result, it becomes possible to narrow down the power failure range of the secondary electric circuit of the transformer 11, and the power failure restoration work can be greatly shortened.

Next, an insulation monitoring method according to a fourth embodiment of the present invention will be described. FIG. 8 is a flow chart showing the processing contents of the insulation monitoring method according to the fourth embodiment of the present invention. 8A is a flow chart showing the processing contents of the superposition measurement unit 19 shown in FIG. 4, and FIG. 8B is a flow chart showing the processing contents of the current measurement unit 20 shown in FIG. In the insulation monitoring method according to the fourth embodiment of the present invention, steps SS1 and SS2 are added to the insulation monitoring method according to the fourth embodiment of the present invention shown in FIG. SS3 is provided.

In FIG. 8(a), steps S1 to S10 of the superposition measurement unit 19 are the same as those in FIG. 7(a), so description thereof will be omitted. After the insulation deterioration is reported in step S10, the measurement and monitoring of the insulation resistance Rg are paused for the pause time Tx (SS1). Then, it is determined whether or not the process is finished (S11). If the process is not finished, the process returns to step S1, and if the process is finished, the process is finished.

In FIG. 8B, the current measurement unit 20 determines whether or not it is a predetermined time before the start time t3 of the measurement monitoring implementation time T1 (S12). If it is not the predetermined time before the start time t3 of the measurement monitoring implementation time T1, it is determined whether or not the superimposition measurement unit 19 has issued an insulation deterioration report (SS2). When there is no notification of insulation deterioration from the superimposition measurement unit 19, the process returns to step S12 and waits until a predetermined time before the start time t3 of the measurement monitoring implementation time T1.

On the other hand, when it is determined in step S12 that it is a predetermined time before the start time t3 of the measurement monitoring implementation time T1, that is, a predetermined zero adjustment time T3 before the start time t3 of the implementation time T1, or the insulation deterioration from the superimposition measurement unit 19 is issued, the zero adjustment voltage V0 is measured (S13). Then, after detecting the zero adjustment voltage V0, a command to apply the superimposed voltage Vt is output to the superimposed measurement unit 19 (S14).

When the superimposed voltage Vt is applied to the secondary electric circuit by the process of step S14, the current sensor 17a is turned on for the first measurement time T5 while the superimposed voltage Vt is being applied to the secondary electric circuit. , 17b is measured as the measurement voltage Vs (SS3).

Then, the voltage difference ΔV between the zero adjustment voltage V0 and the measured voltage Vs is calculated (S16), and it is determined whether or not the voltage difference ΔV is greater than the threshold value VL (S17). When the voltage difference ΔV is not larger than the threshold value VL as a result of this determination, the process returns to step S12. On the other hand, when the voltage difference ΔV is greater than the threshold value VL, the installation locations of the current sensors 17a and 17b where the voltage difference ΔV is greater than the threshold value VL are identified as insulation deterioration locations (S18). After that, it is determined whether or not the process is finished (S19). If the process is not finished, the process returns to step S12, and if the process is finished, the process is finished.

According to the insulation monitoring method of the fourth embodiment of the present invention, similarly to the third embodiment, the superimposed measurement unit 19 periodically sets in advance the stop time T2 during which the measurement and monitoring of the insulation resistance Rg of the electric circuit is not performed. When , the superimposed voltage Vt is calibrated, so the leakage current Ig can be detected with high accuracy, and the accuracy of calculation of the insulation resistance Rg can be improved. Furthermore, in the measurement and monitoring of the insulation resistance Rg of the secondary circuit of the transformer 11 performed by the superimposition measurement unit 19, if the insulation resistance Rg becomes equal to or less than the threshold value RL and an insulation deterioration alarm is issued, even after the pause time Tx, the second Since the same processing (zero adjustment of the current sensors 17a, 17b, measurement of the output voltage of the current sensors 17a, 17b) is performed as in the stop time T2 in the third embodiment, the current measurement unit 20 periodically performs only during the implementation time T1 In addition, even when insulation deterioration is reported, the current sensors 17a and 17b are zero-adjusted and the output voltages of the current sensors 17a and 17b are measured.

Further, during the stop time T2 and the rest time Tx, in a state where the superimposed voltage Vt is applied to the electric circuit, the current sensor is detected only during the first measurement time T5 instead of the predetermined measurement time T1 of the third embodiment. The current sensor 17a measures the output voltages of 17a and 17b as the measured voltage Vs, and the difference voltage ΔV between the zero adjustment voltage V0 and one measured voltage Vs measured only at the first measurement time T5 is greater than the threshold value VL, 17b is specified as an insulation deterioration location. Therefore, the zero adjustment voltage V0 is updated every stop time T2 and rest time Tx, and the voltages Vs measured by the current sensors 17a and 17b immediately after updating the zero adjustment voltage V0 are used. The location of insulation deterioration can be identified with the measured voltage Vs that reduces the effects of temporal fluctuations contained in the output voltages of the current sensors 17a and 17b and fluctuations due to changes in the ambient temperature and magnetic field that affect the measurement accuracy of Vs. As a result, it becomes possible to narrow down the power failure range of the secondary electric circuit of the transformer 11, and the power failure restoration work can be greatly shortened.

Although several embodiments of the invention have been described above, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 11... Transformer, 12... AC power supply, 13... Main circuit, 14... Feeder, 15... Load, 16... Monitoring and measuring unit, 17... Current sensor, 18... Panel computer, 19... Superimposed measuring unit, 20... Current measuring unit , 21... Insulation deterioration part, 22... DC power supply, 23... Switch, 24... Voltmeter, 25... Insulation resistance calculation unit, 26... Insulation deterioration alarm unit, 27... Zero adjustment voltage detection unit, 28... Superimposed voltage application unit , 29... Continuous voltage measurement unit, 30... Insulation deterioration point determination unit, 31... Intermittent voltage measurement unit

Claims (6)

A superimposition measuring unit that applies a superimposed voltage to an electric circuit having a plurality of feeders in a main circuit drawn from the secondary side of a transformer of an ungrounded distribution system, and measures the leakage current of the feeder caused by the superimposed voltage. a monitoring and measuring unit having a current measuring unit for monitoring insulation deterioration of the secondary electric circuit of the transformer; A current sensor for inputting to a monitoring and measuring unit, a panel computer for controlling the operation of the monitoring and measuring unit, recording and displaying data from the monitoring and measuring unit, and transmitting and receiving data to and from a central monitoring device,
In the superimposition measurement unit, an execution time for measuring and monitoring the insulation resistance of the electric circuit and a stop time for not performing the measurement and monitoring are periodically set in advance, and the superimposed voltage is applied to the electric circuit during the execution time. , detecting the leakage current of the electric circuit for each predetermined measurement time, calculating the insulation resistance for each measurement time, and issuing a warning of insulation deterioration when the insulation resistance is equal to or less than a threshold value, and during the stop time is calibrated for the superimposed voltage,
The current measurement unit measures the output voltage of the current sensor for a predetermined zero adjustment time during the stop time as a zero adjustment voltage that is a reference value of the measured voltage of the current sensor, and after measuring the zero adjustment voltage measuring the output voltage of the current sensor as the measurement voltage for each measurement time during the execution time of , obtaining a voltage difference between the zero adjustment voltage and the measurement voltage for each measurement time, wherein the difference voltage is greater than a threshold An insulation monitoring device, wherein the location where the current sensor is installed is specified as an insulation deterioration location. A superimposition measuring unit that applies a superimposed voltage to an electric circuit having a plurality of feeders in a main circuit drawn from the secondary side of a transformer of an ungrounded distribution system, and measures the leakage current of the feeder caused by the superimposed voltage. a monitoring and measuring unit having a current measuring unit for monitoring insulation deterioration of the secondary electric circuit of the transformer; A current sensor for inputting to a monitoring and measuring unit, a panel computer for controlling the operation of the monitoring and measuring unit, recording and displaying data from the monitoring and measuring unit, and transmitting and receiving data to and from a central monitoring device,
In the superimposed measurement unit, an execution time for measuring and monitoring the insulation resistance of the electric circuit and a stop time for not performing the measurement and monitoring are periodically set in advance, and a pause time for stopping the measurement and monitoring during the implementation time. is set, the superimposed voltage is applied to the electric circuit during the execution time other than the stop time and the rest time, the leakage current of the electric circuit is detected every predetermined measurement time, and insulation is performed for each measurement time resistance is calculated, and when the insulation resistance is equal to or less than a threshold value, an insulation deterioration alarm is issued; when the insulation deterioration alarm is issued, the measurement and monitoring are paused for the pause time; Calibrate the superimposed voltage,
The current measurement unit measures the output voltage of the current sensor for a predetermined zero adjustment time during the stop time and the rest time as a zero adjustment voltage that is a reference value of the measured voltage of the current sensor, and measures the zero adjustment voltage The output voltage of the current sensor is measured as the measurement voltage only at the first measurement time during the implementation time after measuring, and the zero adjustment voltage and the one measured only at the first measurement time and a voltage difference between the measured voltage and the installation location of the current sensor where the difference voltage is greater than a threshold is specified as an insulation deterioration location. 3. The insulated monitoring device according to claim 2, wherein the zero-adjustment voltage is affected by the variation included in the output voltage of the current sensor that affects the measurement accuracy of the measured voltage of the current sensor during the stop time. An insulation monitoring device characterized in that the measurement is performed during the stop time in a time period when the insulation is low. 3. The insulated monitoring device according to claim 2, wherein the execution time of the time period in which the fluctuation contained in the output voltage of the current sensor that affects the measurement accuracy of the measured voltage of the current sensor has a large influence is equal to the fluctuation. The insulation monitoring device is characterized in that the execution time is set longer than the execution time in a time zone when the influence of the insulation is small. A superimposition measuring unit that applies a superimposed voltage to an electric circuit having a plurality of feeders in a main circuit drawn from the secondary side of a transformer of an ungrounded distribution system, and measures the leakage current of the feeder caused by the superimposed voltage. a monitoring and measuring unit having a current measuring unit for monitoring insulation deterioration of the secondary electric circuit of the transformer; An insulation monitoring device comprising a current sensor that inputs to a monitoring and measuring unit, and a panel computer that controls the operation of the monitoring and measuring unit, records and displays data from the monitoring and measuring unit, and transmits and receives data to and from a central monitoring device. In the insulation monitoring method for monitoring insulation deterioration of the electric circuit using
The superimposed measurement unit calibrates the superimposed voltage during a stop time during which the measurement and monitoring of the insulation resistance of the electric circuit is not performed, and periodically sets the insulation resistance of the electric circuit. When the implementation time for performing the measurement and monitoring comes or when there is a command to apply the superimposed voltage from the current measurement unit, the superimposed voltage is applied to the electric circuit, and the leakage current of the electric circuit is applied every predetermined measurement time. is detected, the insulation resistance is calculated for each measurement time based on the superimposed voltage and the leakage current, and when the insulation resistance is equal to or less than a threshold value, insulation deterioration is reported,
The current measurement unit measures the output voltage of the current sensor as a zero adjustment voltage that is a reference value of the measurement voltage of the current sensor for a zero adjustment time before the start of the implementation time, and after measuring the zero adjustment voltage During the execution time of , an application command for the superimposed voltage is output to the superimposed measurement unit, and the output voltage of the current sensor is used as the measured voltage for each measurement time while the superimposed voltage is being applied to the electric circuit. measuring, obtaining a voltage difference between the zero adjustment voltage and the measured voltage for each measurement time, and specifying an installation location of the current sensor where the difference voltage is greater than a threshold as an insulation deterioration location . . A superimposition measuring unit that applies a superimposed voltage to an electric circuit having a plurality of feeders in a main circuit drawn from the secondary side of a transformer of an ungrounded distribution system, and measures the leakage current of the feeder caused by the superimposed voltage. a monitoring and measuring unit having a current measuring unit for monitoring insulation deterioration of the secondary electric circuit of the transformer; An insulation monitoring device comprising a current sensor that inputs to a monitoring and measuring unit, and a panel computer that controls the operation of the monitoring and measuring unit, records and displays data from the monitoring and measuring unit, and transmits and receives data to and from a central monitoring device. In the insulation monitoring method for monitoring the insulation deterioration of the electric circuit using
The superimposed measurement unit calibrates the superimposed voltage during a stop time during which the measurement and monitoring of the insulation resistance of the electric circuit is not performed, and periodically sets the insulation resistance of the electric circuit. When the implementation time for performing the measurement and monitoring comes or when there is a command to apply the superimposed voltage from the current measurement unit, the superimposed voltage is applied to the electric circuit, and the leakage current of the electric circuit is applied every predetermined measurement time. is detected, the insulation resistance for each measurement time is calculated based on the superimposed voltage and the leakage current, and when the insulation resistance is equal to or less than a threshold value, the insulation deterioration is reported, and the insulation deterioration is reported. Pausing the measurement and monitoring for a preset pause time when there is,
The current measurement unit reduces the output voltage of the current sensor for the predetermined zero adjustment time before the start of the implementation time or for the predetermined zero adjustment time when the insulation deterioration is reported from the superimposition measurement unit. Measured as a zero adjustment voltage that is a reference value of the measured voltage of the current sensor, outputting an application command for the superimposed voltage to the superimposed measurement unit during the implementation time after measuring the zero adjustment voltage, and applying the superimposed voltage to the electric circuit The output voltage of the current sensor is measured as the measurement voltage only during the first measurement time while the superimposed voltage is being applied, and one voltage is measured only during the zero adjustment voltage and the first measurement time. obtaining a voltage difference from the measured voltage, and specifying an installation location of the current sensor where the difference voltage is greater than a threshold value as an insulation deterioration location.

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