Live-line DC insulation resistance monitoring device, power reception equipment, and live-line DC insulation monitoring method

Abstract

To provide a live-line DC insulation resistance monitoring device capable of measuring DC insulation resistance under live conditions using a simple device configuration even when three-phase currents are balanced.SOLUTION: A live-line DC insulation resistance monitoring device provided herein is configured to compute a voltage-to-ground signal at a power receiving point of each phase using an inter-line voltage signal output from an instrument transformer and a zero phase voltage signal output from a capacitive zero phase voltage meter, and estimate DC insulation resistance of each phase from a phase difference between the voltage-to-ground signal and a current signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a DC insulation resistance live-line monitoring device, a power receiving facility, and a DC insulation resistance live-line monitoring method. [Background technology]

[0002] A common conventional method for measuring DC insulation resistance at high voltage consumers is to cut off the power distribution system, connect a high voltage DC power supply, and measure the leakage current.

[0003] To improve this situation, a DC insulation resistance (leakage resistance) monitoring device is disclosed, for example, in Patent Document 1. The system in Patent Document 1 is intended for a single-wire grounded power distribution system. This system measures the DC insulation resistance of the power distribution system in a live state using the phase angle between the zero-phase current and line voltage measured by a zero-phase current transformer (ZCT). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-205700 Summary of the Invention [Problem to be solved by the invention]

[0005] The DC insulation resistance monitoring device described in Patent Document 1 has the following issues: it requires a zero-phase current transformer ZCT; it requires a means for measuring line voltage; when the three-phase currents are balanced, the output of the zero-phase current transformer ZCT becomes zero, making it impossible to measure DC insulation resistance; when applying it to an ungrounded three-phase system of a high-voltage consumer, the neutral point potential fluctuates, resulting in large errors in DC insulation resistance estimation; and it is not possible to measure changes in DC insulation resistance of the ground phase.

[0006] To begin with, Patent Document 1 is a technology used for a power distribution system with single-wire grounding on the low-voltage side of a transformer, and is not a technology used on the power receiving panel side.

[0007] An object of the present invention is to provide a live DC insulation resistance monitoring device that uses a simple device configuration to measure DC insulation resistance in a live-line state even when three-phase currents are balanced. [Means for solving the problem]

[0008] A live-line DC insulation resistance monitoring device according to one aspect of the present invention is a live-line DC insulation resistance monitoring device that monitors the DC insulation resistance of a multi-phase power distribution system in a power receiving facility of a high-voltage consumer in a live state, and is characterized by comprising: a voltage-to-ground calculation unit that calculates a voltage-to-ground signal at the power receiving point of each phase based on a line voltage signal output from a potential transformer that measures the voltage and current at the power receiving point and a zero-phase sequence voltage signal output from a capacitor-type zero-phase sequence voltage meter that measures the zero-phase sequence voltage; and a phase resistance calculation unit that calculates a phase difference between the voltage-to-ground signal and the current signal based on the calculated voltage-to-ground signal and the current signal output from the potential transformer, and estimates the DC insulation resistance of each phase from the phase difference. [Effects of the Invention]

[0009] According to one aspect of the present invention, in a live DC insulation resistance monitoring device, it is possible to measure the DC insulation resistance in a live-line state even when three-phase currents are balanced, using a simple device configuration. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a live-line DC insulation resistance monitoring device according to a first embodiment. [Figure 2] 3 is a voltage vector diagram showing the operation of the live line DC insulation resistance monitoring device of the first embodiment. [Figure 3] 3 is a current vector diagram showing the operation of the live line DC insulation resistance monitoring device of the first embodiment. [Figure 4] 3 is a current and voltage waveform diagram showing the operation of the live line DC insulation resistance monitoring device of the first embodiment. FIG. [Figure 5] 3 is a characteristic diagram of the voltage-current phase difference and earth resistance of the live DC insulation resistance monitoring device of the first embodiment. FIG. [Figure 6]FIG. 10 is a diagram showing the configuration of a live-line DC insulation resistance monitoring device according to a second embodiment. [Figure 7] FIG. 10 is a diagram showing the configuration of a live-line DC insulation resistance monitoring device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described below with reference to the drawings. Note that the following are merely examples of the present invention, and the content of the invention is not limited to the specific embodiments described below. The present invention can of course be modified into various embodiments, including the embodiments described below. The embodiments will be described below with reference to the drawings. [Example]

[0012] The first embodiment will be described with reference to FIGS. 1 to 5. FIG.

[0013] First, Fig. 1 shows a live DC insulation resistance monitoring device according to a first embodiment. A high-voltage power receiving panel 2 of a high-voltage consumer is connected to an ungrounded high-voltage distribution system 1. The ungrounded high-voltage distribution system 1 consists of multiple phases (U phase, V phase, and W phase). Here, "high voltage" refers to 6,600V.

[0014] The high-voltage power receiving panel 2 is equipped with an instrument transformer 5 for measuring the voltage and current at the receiving point, a capacitor-type zero-phase voltage measuring device 6 for measuring the zero-phase voltage, and a sending circuit breaker 4. In addition, a transformer panel 3 is connected to the secondary side of the high-voltage power receiving panel 2. The transformer panel 3 is equipped with a transformer 7, which transforms the high voltage to a low voltage and supplies power to a load (not shown).

[0015] The area where the high voltage of the transformer 7 of the high-voltage incoming panel 2 and the transformer panel 3 is applied is hereinafter referred to as the ungrounded high-voltage distribution system. The ungrounded high-voltage distribution system has DC insulation resistance 30 and leakage capacitance 31. DC insulation resistance 30 causes heat generation and is an indicator of deterioration of the earth insulation performance, so it needs to be measured regularly. Here, DC insulation resistance is also called leakage resistance.

[0016] In the first embodiment, the line voltage signal 10 of the potential transformer 5 and the zero-phase voltage signal 12 of the capacitor-type zero-phase voltage measuring instrument 6 are input to a voltage-to-ground calculation unit 20 to calculate the voltage to ground of each phase.

[0017] The calculated voltage-to-ground signal 23 for each phase and the current signal 11 from the instrument transformer 5 are input to a phase resistance calculation unit 21 to calculate the phase difference between the voltage-to-ground and current for each phase, and the DC insulation resistance for each phase is calculated from this phase. The calculated DC insulation resistance signal 24 is input to a display unit 22 to display the DC insulation resistance and, if necessary, to compare it with a reference value to issue a warning of an abnormality in the DC insulation resistance.

[0018] FIG. 2 is a vector diagram showing the process of calculating the voltage to ground of each phase from the line voltage signal 10 of the instrument transformer 5 and the zero-phase voltage signal 12 of the capacitor-type zero-phase voltage measuring instrument 6 in the first embodiment.

[0019] First, the UV line voltage b (42UVb) and WU line voltage b (42WUb) are output from the potential transformer VCT5, but the voltage to ground is undefined. Next, the zero-phase sequence voltage 44a is output from the capacitor-type zero-phase sequence voltage meter 5. Since the zero-phase sequence voltage 44a corresponds to the neutral point potential 200 of each phase, the voltages to ground Vu, Vv, and Vw of each phase can be calculated by adding the zero-phase sequence voltage 44a to the UV line voltage b (42UVb) and WU line voltage b (42WUb).

[0020] FIG. 3 is a vector diagram showing the process of calculating each phase current from the current signal 11 of the instrument transformer 5 in the first embodiment.

[0021] For example, when U-phase current 46U and V-phase current 46V are output from instrument transformer 5, the reverse vector of the vector sum of U-phase current 46U and V-phase current 46V is calculated as the W-phase current.

[0022] FIG. 4 shows the results of calculating the U-phase-to-ground voltage and U-phase current waveform when the DC insulation resistance 30 of the ungrounded high-voltage distribution system is 100 kΩ and 10 MΩ in Example 1.

[0023] When the DC insulation resistance 30 in (a) is 100 kΩ, the phase difference between the U phase-to-earth voltage and the U phase current is phase difference a (48), and when the DC insulation resistance 30 in (b) is 10 MΩ, the phase difference between the U phase-to-earth voltage and the U phase current is phase difference b (49).

[0024] FIG. 5 shows the characteristics of the DC insulation resistance 30 versus the phase difference between the U phase-to-ground voltage and the U-phase current in the first embodiment.

[0025] When DC insulation resistance 30 changes from 100 MΩ to 100 kΩ, the phase difference between the U-phase-to-ground voltage and the U-phase current changes by 13°. Based on this characteristic, DC insulation resistance 30 can be estimated from the phase difference between the U-phase-to-ground voltage and the U-phase current.

[0026] As described above, this first embodiment includes a voltage-to-ground calculation unit 20 that calculates a voltage-to-ground signal 23 at the power receiving point of each phase based on the line voltage signal 10 output from the potential transformer 5 that measures the voltage and current at the power receiving point and the zero-phase-sequence voltage signal 12 output from the capacitor-type zero-phase-sequence voltage measuring instrument 6 that measures the zero-phase-sequence voltage, and a phase resistance calculation unit 21 that calculates the phase difference between the voltage-to-ground signal 23 and the current signal 11 based on the calculated voltage-to-ground signal 23 and the current signal 11 output from the potential transformer 5, and estimates the DC insulation resistance of each phase from the phase difference. [Example]

[0027] The second embodiment will be described with reference to FIG.

[0028] In this second embodiment, two lines (output line 1 (60a) and output line 2 (60b)) are output from the high-voltage incoming panel 2. Output line 1 (60a) is provided with a current transformer 8a. Output line 2 (60b) is provided with a current transformer 8b. A transformer panel 3 is connected to each of the current transformers 8a and 8b. The other configurations are almost the same as those in the first embodiment, so a description thereof will be omitted.

[0029] Then, as in the first embodiment, the voltage to ground of each phase is calculated from the line voltage signal 10 of the potential transformer 5. Furthermore, the current of each phase is calculated from the current signal 11a of the potential transformer 5, the current signal 11b of the current transformer 8a, and the current signal 11c of the current transformer 8b, and the DC insulation resistance of the entire ungrounded high-voltage distribution system is calculated from the phase difference between the voltage and current of each phase.

[0030] In this way, in the second embodiment, current transformers 8a and 8b are provided for each of sending lines 1 (60a) and 2 (60b), and current signals 11b and 11c are output from the current transformers 8a and 8b, respectively. Then, the DC insulation resistance is estimated for each channel (3CH) of the current signal.

[0031] Furthermore, in this second embodiment, the current of each phase flowing through each line is calculated using current transformers 8a and 8b provided for each line (outgoing line 1 (60a) and outgoing line 2 (60b)), and the DC insulation resistance of each line is calculated from the phase difference with the voltage to ground of each phase. Then, the display / area determination unit 220 determines in which area of ​​the high-voltage distribution system the DC insulation resistance has decreased, and displays the DC insulation resistance. Here, "area" means the area from the downstream side of the current transformer to the transformer panel 3.

[0032] As described above, in the present embodiment 2, the phase resistance calculation unit 21 determines the area where the DC insulation resistance has decreased by estimating the DC insulation resistance of the output lines 60a, 60b from the current signals 11b, 11c of the multiple current transformers 8a, 8b provided on each of the multiple output lines 60a, 60b of the high-voltage power receiving panel 2 of the power receiving equipment.

[0033] For example, the phase resistance calculation unit 21 determines one of the plurality of transformer panels 3 provided for each of the plurality of current transformers 8a, 8b as the region where the DC insulation resistance has decreased. [Example]

[0034] A third embodiment will be described with reference to Fig. 7. In the third embodiment, a wattmeter 50 is provided that calculates power from a line voltage signal 10 and a current signal 11 of an instrument transformer 5.

[0035] When the power consumption falls below a certain value, the power meter 50 sends a DC insulation resistance measurement command 51 to the phase resistance calculation unit 21 to measure the DC insulation resistance from the phase difference between the voltage and current. As a result, there is an effect that the estimation error of the DC insulation resistance is reduced. The other configurations are almost the same as those of the first embodiment, so a description thereof will be omitted.

[0036] As described above, in the third embodiment, the power meter 50 calculates the power consumption based on the line voltage signal 10 and the current signal 11 output from the instrument transformer 5, and transmits a DC insulation resistance measurement command 51 to the phase resistance calculation unit 21 to measure the DC insulation resistance when the power consumption falls below a certain value.

[0037] In the above embodiment, for ungrounded high voltage consumers, the use of the existing instrument transformer VCT5 and capacitor-type zero-phase-sequence voltage measuring device ZPD6 eliminates the need to add voltage / current measuring means or zero-phase-sequence current transformer ZCT. In addition, even when the three-phase current is balanced, the DC insulation resistance of ungrounded high-voltage consumers can be measured live. Furthermore, the measurement error of the DC insulation resistance can be reduced and the DC insulation resistance of each phase can be measured. [Explanation of symbols]

[0038] 1 Ungrounded high voltage distribution system 2 High-voltage power receiving panel 3 Transformer panel 4 Circuit Breaker 5. Instrument transformer 6. Capacitor-type zero-phase voltage measuring instrument 7. Transformers 8a, 8b current transformer 20. Voltage to ground calculation section 21 Phase resistance calculation section 22 Display section 30 DC insulation resistance 31 Leakage capacitance 50 wattmeter 220 Display / area determination section

Claims

1. A DC insulation resistance live-line monitoring device that monitors DC insulation resistance of a power distribution system consisting of multiple phases in a power receiving facility of a high-voltage consumer in a live-line state, a voltage-to-ground calculation unit that calculates a voltage-to-ground signal at the power receiving point of each phase based on a line voltage signal output from an instrument transformer that measures the voltage and current at the power receiving point and a zero-phase sequence voltage signal output from a capacitor-type zero-phase sequence voltage measuring device that measures the zero-phase sequence voltage; a phase resistance calculation unit that calculates a phase difference between the voltage to ground signal and the current signal based on the calculated voltage to ground signal and the current signal output from the instrument transformer, and estimates the DC insulation resistance of each phase from the phase difference; A live line DC insulation resistance monitoring device comprising:

2. The voltage-to-ground calculation unit 2. The live line DC insulation resistance monitoring device according to claim 1, wherein the voltage to ground signal is calculated by correcting the line voltage signal output from the instrument transformer using the zero-phase sequence voltage signal output from the capacitor-type zero-phase sequence voltage measuring device.

3. The zero-phase voltage signal output from the capacitor-type zero-phase voltage measuring device corresponds to the neutral point potential of each phase, The voltage-to-ground calculation unit 3. The DC insulation resistance live line monitoring device according to claim 2, wherein the voltage-to-ground signal of each phase is calculated by adding the zero-phase voltage signal to the line voltage signal of each phase.

4. The phase resistance calculation unit calculating a phase current for each phase from the current signal output from the instrument transformer; 2. The live line DC insulation resistance monitoring device according to claim 1, wherein the DC insulation resistance of each phase is estimated from the phase difference between the voltage-to-ground signal and the phase current of each phase.

5. 2. The DC insulation resistance live-line monitoring device according to claim 1, further comprising a display unit that displays the DC insulation resistance and issues a warning of an abnormality in the DC insulation resistance by comparing the DC insulation resistance with a predetermined reference value.

6. The phase resistance calculation unit 2. The live-line DC insulation resistance monitoring device according to claim 1, wherein the DC insulation resistance of the sending lines is estimated from current signals of a plurality of current transformers provided on each of a plurality of sending lines of the power receiving panel of the power receiving equipment, thereby determining an area where the DC insulation resistance has decreased.

7. The phase resistance calculation unit 7. The live-line DC insulation resistance monitoring device according to claim 6, wherein the DC insulation resistance is determined to be the area where the DC insulation resistance has decreased on one of a plurality of transformer panels provided for each of the plurality of current transformers.

8. 2. The live-line DC insulation resistance monitoring device according to claim 1, further comprising a wattmeter that calculates power consumption based on the line voltage signal and the current signal output from the instrument transformer, and transmits a command to the phase resistance calculation unit to measure the DC insulation resistance when the power consumption falls below a certain value.

9. A power receiving facility of a high-voltage consumer having a power receiving panel, a transformer panel, and a multi-phase power distribution system, The receiving panel is an instrument transformer for measuring the voltage and current at the receiving point; a capacitor-type zero-phase voltage measuring instrument for measuring zero-phase voltage; a DC insulation resistance live-line monitoring device that monitors the DC insulation resistance of the power distribution system in a live-line state, The DC insulation resistance live line monitoring device is a voltage-to-ground calculation unit that calculates a voltage-to-ground signal at the power receiving point of each phase based on the line voltage signal output from the instrument transformer and the zero-phase-sequence voltage signal output from the capacitor-type zero-phase-sequence voltage measuring device; a phase resistance calculation unit that calculates a phase difference between the voltage to ground signal and the current signal based on the calculated voltage to ground signal and the current signal output from the instrument transformer, and estimates the DC insulation resistance of each phase from the phase difference; A power receiving facility characterized by having:

10. A DC insulation resistance live-line monitoring method for monitoring DC insulation resistance of a power distribution system consisting of multiple phases in a power receiving facility of a high-voltage consumer in a live-line state, comprising: a voltage-to-ground calculation step of calculating a voltage-to-ground signal at the power receiving point of each phase based on a line voltage signal output from an instrument transformer that measures the voltage and current at the power receiving point and a zero-phase-sequence voltage signal output from a capacitor-type zero-phase-sequence voltage measuring device that measures the zero-phase-sequence voltage; a phase resistance calculation step of calculating a phase difference between the voltage to ground signal and the current signal based on the calculated voltage to ground signal and the current signal output from the instrument transformer, and estimating the DC insulation resistance of each phase from the phase difference; A live line monitoring method for DC insulation resistance, comprising:

Images