Partial discharge detection system of electrical apparatus

Abstract

To provide a partial discharge detection system targeting a power receiving / distributing apparatus.SOLUTION: A partial discharge detection system of a power receiving / distributing apparatus includes: a control device housing a plurality of power devices such as a breaker and a disconnector within a grounded metal case and configured to control / monitor the plurality of power devices; and a partial discharge sensor dependent on an electromagnetic wave. The partial discharge detection system is configured to: measure a voltage of one phase among three phases as a reference phase; calculate the number of times by which an output of the partial discharge sensor dependent on an electromagnetic wave enters a range of a phase angle of a preset voltage; and determine a phase corresponding to a range of a phase angle reaching a prescribed number of times or more as a phase at which a partial discharge is occurring.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a partial discharge detection system for electrical equipment. [Background technology]

[0002] Background art in this technical field is found in Japanese Patent Application Laid-Open No. 2005-189226 (Patent Document 1), which describes "a small-sized partial discharge monitoring device that can be remotely monitored by significantly reducing the number of partial discharge detection pulses and distinguishing between partial discharge and noise." [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-189226 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 describes a partial discharge monitoring device and a partial discharge remote monitoring system that detects the same pulse in two bands and detects only the partial discharge crest with high resolution in response to the partial discharge occurrence phenomenon in a rotating electrical machine. The device is also configured to lengthen the discharge detection repetition time in consideration of the interval between partial discharge occurrences. This configuration enables high-resolution detection and a reduced number of detected pulses, provides excellent noise removal capabilities, and is compact.

[0005] However, since a partial discharge sensor is installed on each phase, three sets of current-dependent partial discharge sensors are used, and a phase switch is also used, resulting in high costs.

[0006] The present invention provides an inexpensive partial discharge detection system for power distribution equipment that can determine the phase in which a partial discharge has occurred without using three sets of current-dependent partial discharge sensors and a phase switch. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one aspect of the partial discharge detection system of the present invention is a partial discharge detection system that detects partial discharges in electrical equipment having electric power equipment housed in a grounded metal case and a control device that controls the electric power equipment, and includes an electromagnetic wave-dependent partial discharge sensor, a partial voltage measuring device that measures voltage using any one of three phases as a reference phase, and a partial discharge occurrence phase determiner that calculates the number of times the output of the partial discharge sensor falls within a predetermined phase angle range of the voltage relative to the reference phase voltage, and determines that the phase corresponding to the phase angle range in which this number is equal to or greater than a predetermined number is the phase in which partial discharge is occurring. [Effects of the Invention]

[0008] According to the present invention, it is possible to realize an inexpensive partial discharge detection system that can identify the phase in which a partial discharge has occurred. Note that problems, configurations, and effects other than those described above will become clear from the description of the following embodiments. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of a partial discharge detection system for an electric device according to a first embodiment. [Figure 2A] FIG. 2A is a diagram illustrating an example of the configuration of a partial discharge detection system. [Figure 2B] FIG. 2B is a diagram illustrating an example of a hardware configuration of the partial discharge occurrence phase determination device. [Figure 3] FIG. 3 is a diagram showing phase voltages of a three-phase AC current. [Figure 4] FIG. 4 is a diagram showing a processing flow of the partial discharge occurrence phase determiner 11. [Figure 5] FIG. 5 is a diagram illustrating an example of a partial discharge detection system for an electric device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the partial discharge detection system for power receiving and distribution equipment of the present invention will be described with reference to the drawings. In each embodiment, the same components are designated by the same reference numerals.

[0011] In electrical equipment, it is important to identify the phase in which a partial discharge occurs in order to diagnose the insulation condition, perform maintenance management, and prevent accidents. Diagnosis of insulation condition is carried out by detecting partial discharges, which are weak localized discharges that occur at insulation defects in electrical equipment. By identifying the phase in which the partial discharge occurred in electrical equipment, the insulation condition of that phase can be diagnosed. Identifying signs of insulation deterioration and problem areas is important for taking appropriate measures. Diagnosing the insulation condition enables maintenance management and accident prevention. By monitoring changes in partial discharge over time, trends in insulation deterioration can be identified. As the insulation condition deteriorates, partial discharges can become larger and occur more frequently. Insulation diagnosis makes it possible to understand the insulation condition during operation and prevent serious accidents before they occur. [Example]

[0012] 1 shows a partial discharge detection system for electrical equipment according to the first embodiment. Hereinafter, the electrical equipment includes substation equipment, power distribution equipment, and power receiving and distributing equipment that receive and distribute power. In addition, the description will be given taking power receiving and distributing equipment as an example, but the present invention is not limited to this.

[0013] The power receiving and distribution equipment 1 shown in Fig. 1 has a grounded metal case 2. Although the interior of the metal case 2 is not shown, it contains a plurality of power devices such as circuit breakers, disconnecting switches, and instrument transformers, and is equipped with a control device 3 that controls the plurality of power devices. Three-phase AC 4 (U phase 5, V phase 6, W phase 7) is input from the outside to the power receiving and distribution equipment 1 via a high-voltage cable or the like, and is connected to the power devices placed inside the metal case 2. The high-voltage section inside the power receiving and distribution equipment 1 is electrically insulated and supported by insulating materials such as insulators fixed to the grounded metal case 2 and steel material that has the same potential as the metal case 2.

[0014] The partial discharge detection system 12 includes a voltage divider 9, an electromagnetic wave-dependent partial discharge sensor 10, and a partial discharge occurrence phase determiner 11.

[0015] Partial discharge is explained below. When dust accumulates on the high-voltage section of the power distribution equipment 1 and causes contamination, the surface of the high-voltage section may become uneven. If this unevenness becomes significant, a high electric field is generated, causing a discharge that connects the high-voltage section to the ground, i.e., a ground fault. Furthermore, when power distribution equipment is used for a long period of time, the insulating performance of the insulator surface or inside the insulator gradually deteriorates due to aging of the insulators, etc., and ultimately leads to a ground fault. Generally, before a ground fault develops, a weak discharge that does not connect the high-voltage section to the ground, i.e., a partial discharge, occurs. Partial discharge generally occurs frequently near the peak value of the phase voltage, and it is known that electromagnetic waves 8 containing megahertz-level signals are emitted.

[0016] 2A shows the configuration of a partial discharge detection system 12 of this embodiment. It is composed of a voltage divider 9 that measures the phase voltage (reference phase voltage) of a reference phase, in this case the U-phase 5, an electromagnetic wave-dependent partial discharge sensor (PD sensor) 10 that detects electromagnetic waves 8 generated from point a where partial discharge has occurred, and a partial discharge occurrence phase determiner 11 that determines the phase in which partial discharge has occurred based on the reference phase voltage and the output of the electromagnetic wave-dependent partial discharge sensor.

[0017] Instead of the voltage divider 9, the reference phase voltage may be obtained from a line voltage detector installed between the U phase 5 and the V phase 6. A configuration for measuring the reference phase voltage from the voltage divider 9 or line voltage detector is called a voltage divider measuring device. Below, an embodiment will be described using the voltage divider 9.

[0018] 2B shows the hardware configuration of the partial discharge occurrence phase determination device 11. The partial discharge occurrence phase determination device 11 has a processor 111, a storage device 112, an input IF 113 that receives a signal from the voltage divider 9, an output IF 114 that outputs a signal to the control device 3, and a bus 115 that electrically connects the processor 111, the storage device 112, the input IF 113, and the output IF 114 and transmits and receives signals. The storage device 112 includes a main memory (RAM or the like) and an auxiliary memory (SSD or the like). The partial discharge occurrence phase determination device 11 executes a program stored in the storage device 112 to perform the processing shown in FIG. 4, which will be described later, and realizes its functions.

[0019] The partial discharge occurrence phase detector 11 shown in FIG. 2B can also be configured within the control device 3 using the resources of the control device 3.

[0020] The partial discharge occurrence phase detector 11 may also employ a circuit that counts the number of partial discharges in an analog manner.

[0021] Figure 3 shows the phase voltages of three-phase AC, with U phase 5 shown as a thick line, V phase 6 as a dotted line, and W phase 7 as a dashed line, all representing peak value E. Because it is three-phase AC, U phase 5 and V phase 6 are out of phase with each other by 120°, and U phase 5 and W phase 7 are out of phase with each other by 240°.

[0022] The partial discharge detection system of this embodiment is configured to input to an input IF 113 of a partial discharge occurrence phase determiner 11 a voltage measured by a voltage divider 9 as the phase voltage of a reference phase (here, U phase 5) and an output of an electromagnetic wave-dependent partial discharge sensor 10 that detects electromagnetic waves 8 generated from point a where partial discharge has occurred.

[0023] Here, a method for determining the phase in which partial discharge has occurred in this embodiment will be described.

[0024] First, the voltage of the reference phase (U phase 5) is measured when the electromagnetic wave-dependent partial discharge sensor 10 detects a partial discharge, and the phase angle of the reference phase (U phase 5) is calculated from the measured voltage value. In general, partial discharges occur frequently near the peak value of the phase voltage, and it is known that electromagnetic waves 8 having megahertz-class signals are emitted.

[0025] 3, partial discharges in each phase can be determined by counting the number of partial discharges at phase angles exceeding 0.866 of the peak value E for the U, V, and W phases. The value 0.866 corresponds to phase angles of 60°<120° and 240°<300° for the reference phase (U phase 5), to phase angles of 0°<60° and 180°<240° for the V phase 6, which is 120° out of phase with the reference phase (U phase 5), and to phase angles of 120°<180° and 300°<360° for the W phase 7, which is 240° out of phase with the reference phase (U phase 5).

[0026] When the calculated phase angle is in the range of greater than 60° and less than 120°, or greater than 240° and less than 300°, the number of partial discharges in the reference phase (U-phase 5) is counted.

[0027] Furthermore, when the calculated phase angle is in the range of greater than 0° and less than 60°, or greater than 180° and less than 240°, the number of partial discharges is counted as V-phase 6.

[0028] Furthermore, when the calculated phase angle is in the range of greater than 120° but less than 180°, or greater than 300° but less than 360°, the number of partial discharges is counted as being in the W phase.

[0029] When the number of partial discharges reaches a predetermined number or more, the phase in which the number of partial discharges reaches the predetermined number or more is determined to be the phase in which the partial discharge has occurred.

[0030] Here, for example, if a partial discharge occurs at a U-phase phase angle of 59°, it is determined that a partial discharge has occurred in the V-phase. However, because partial discharges occur frequently near the peak value of the phase voltage, the overall impact is small, so it is possible to determine the phase in which the partial discharge occurred without any problems.

[0031] Furthermore, if the phase angle calculated using the above method is 60°, 120°, 180°, 240°, 300°, or 360°, it will not be counted, but this also has a small overall impact, so it is possible to determine the phase in which the partial discharge occurred without any problems.

[0032] In Figure 3, to count the number of partial discharges near the peak value E, the number of partial discharges is counted at the following phase angles for each phase. ·Reference phase (U phase 5): Phase angle 60°<120°, 240°<300° ·V phase 6: Phase angle 0°<60°, 180°<240° ·W phase 7: Phase angle 120°<180°, 300°<360° It is sufficient to detect partial discharges in each phase, and the phase angles for counting the number of partial discharges in each phase are as follows: ·Reference phase (U phase 5): Phase angle 90°, 270° ·V phase 6: Phase angle 30°, 210° ·W phase 7: Phase angle 150°, 330° The range may be any range as long as partial discharges in each phase can be appropriately detected at a certain time while taking noise into consideration, and may be, for example, the following phase angles: ·Reference phase (U phase 5): Phase angle 90±15°, 270±15° ·V phase 6: Phase angle 30±15°, 210±15° ·W phase 7: Phase angle 150±15°, 330±15° However, if the fixed time is too short, it becomes difficult to distinguish between noise and partial discharge. Therefore, the detection of partial discharge occurrence should be appropriately determined depending on the installation environment of the power receiving and distribution equipment and its specifications, such as once per minute to once per 10 minutes.

[0033] The number of partial discharge pulses is extremely large, ranging from several hundred to several thousand per second, and includes noise. In this embodiment, the partial discharge occurrence phase determiner 11 counts as one the number of times that the partial discharge sensor 10 receives an output, when the partial discharge sensor 10 measures an electromagnetic wave exceeding a predetermined threshold (first threshold) within a range of a phase angle between the reference phase (U phase) voltage and a preset voltage.

[0034] The bottom of Figure 3 shows that the partial discharge occurrence phase detector 11 detects partial discharge at a phase angle of 60°<120° in the U phase. In other words, the partial discharge occurrence phase detector 11 counts one partial discharge occurrence in the U phase between a phase angle of 60°<120°. The bottom of Figure 3 shows an enlarged view of the output of the electromagnetic wave-dependent partial discharge sensor 10 at a phase angle of 60°<120° in the U phase. It can be seen that the output of the electromagnetic wave-dependent partial discharge sensor 10 exceeds the first threshold (e). If the output of the electromagnetic wave-dependent partial discharge sensor 10 exceeds the first threshold at a phase angle of 60°<120° in the U phase, it is counted as one partial discharge occurrence in the U phase between a phase angle of 60°<120° in the U phase.

[0035] Although not shown in FIG. 3, the partial discharge occurrence phase determination device 11 similarly counts the number of partial discharges in the U phase when the phase angle is 240°<300°, and similarly counts the number of partial discharges using the first threshold value (e) when the phase angle is 0°<60° and 180°<240° in the V phase, and when the phase angle is 120°<180° and 300°<360° in the W phase.

[0036] FIG. 4 shows a processing flow of the partial discharge occurrence phase determining device 11.

[0037] In step S11, the partial discharge occurrence phase determiner 11 measures the voltage of the reference phase (U phase 5) using the partial discharge sensor 10. Note that the voltage may be a V phase other than the U phase.

[0038] In step S12, it is determined whether the phase angle is 60°<120° and 240°<300°. If the determination result is YES, the process proceeds to step S13, and if the determination result is NO, the process proceeds to step S17.

[0039] In step S13, it is determined whether the partial discharge sensor 10 is equal to or greater than a predetermined threshold (first threshold), and if it is equal to or greater than the first threshold, the process proceeds to step S14, and if not, the process returns to step S11.

[0040] In step S14, the number of partial discharges occurring when the phase angle is 60°<120° and 240°<300° is counted.

[0041] In step S15, it is determined whether the number of partial discharges is equal to or greater than a predetermined number. If it is equal to or greater than the predetermined number, the process proceeds to step S16, and if it is not equal to or greater than the predetermined number, the process returns to step S11. In step S16, it is determined that a partial discharge has occurred in the reference phase (U phase).

[0042] If the determination in step S12 is NO, then in step S17 it is determined whether the phase angle is 0°<60° and 180°<240°. If the determination result is YES, the process proceeds to step S18, and if NO, the process proceeds to step S22.

[0043] In step S18, it is determined whether the partial discharge sensor 10 is equal to or greater than a predetermined threshold (first threshold), and if it is equal to or greater than the first threshold, the process proceeds to step S19, and if not, the process returns to step SD11.

[0044] In step S19, the number of partial discharges occurring when the phase angle is 60°<120° and 240°<300° is counted.

[0045] In step S20, it is determined whether the number of partial discharges is equal to or greater than a predetermined number. If it is equal to or greater than the predetermined number, the process proceeds to step S21, and if it is not equal to or greater than the predetermined number, the process returns to step S11.

[0046] In step S21, it is determined that a partial discharge has occurred in the V phase.

[0047] If the determination in step S17 is NO, then in step S22 it is determined whether the phase angle is 120°<180° and 300°<360°. If the determination result is YES, the process proceeds to step S23, and if NO, the process returns to step S11.

[0048] In step S23, it is determined whether the partial discharge sensor 10 is equal to or greater than a predetermined threshold (first threshold), and if it is equal to or greater than the first threshold, the process proceeds to step S24, and if not, the process returns to step S11.

[0049] In step S24, the number of partial discharges occurring when the phase angle is 120°<180° and 300°<360° is counted.

[0050] In step S25, it is determined whether the number of partial discharges is equal to or greater than a predetermined number. If it is equal to or greater than the predetermined number, the process proceeds to step S26; if not, the process returns to step S11.

[0051] In step S26, it is determined that a partial discharge has occurred in the W phase.

[0052] Steps S14, S19, and S24 are reset after a certain period of time has elapsed. This is because if counting continues for a long period of time, it becomes difficult to distinguish between noise and partial discharge. Steps S12, S17, and S22 may be interchanged.

[0053] According to the partial discharge detection system for power distribution equipment described above, it is possible to realize an inexpensive partial discharge detection system that can determine the phase in which a partial discharge has occurred using a single electromagnetic wave-dependent partial discharge sensor, without using three sets of current-dependent partial discharge sensors and a phase switch. [Example]

[0054] Fig. 5 shows Example 2. Explanation of the same parts as in Example 1 will be omitted. The partial discharge detection system for power distribution equipment in this example is configured to include a display 13 that lights up when it determines the phase in which a partial discharge has occurred. The display 13 is configured by a display device such as a general liquid crystal display device.

[0055] When it is determined in steps S16, S21, and S26 of FIG. 4 that a partial discharge has occurred in each phase, the partial discharge occurrence phase determiner 11 sends a signal indicating in which phase a partial discharge has occurred to the display 13.

[0056] The display 13 displays a U-phase signal if the partial discharge occurred in the U-phase, a V-phase signal if the partial discharge occurred in the V-phase, and a W-phase signal if the partial discharge occurred in the W-phase, according to the signal sent from the partial discharge occurrence phase determiner 11. The display 13 may display the U-phase, V-phase, or W-phase signals in different colors or flash differently depending on the U-phase, V-phase, or W-phase signals.

[0057] The display 13 may also be an alarm, and in this case too, it outputs an alarm assigned to each phase in accordance with the signal sent from the partial discharge occurrence phase determiner 11.

[0058] The partial discharge detection system for power distribution equipment configured in this manner not only has the same effects as those of Example 1, but also makes it possible to confirm an abnormality in the power distribution equipment, i.e., the occurrence of partial discharge, based on whether or not the signal is lit, and to identify an abnormality at an early stage of deterioration in insulation performance, thereby enabling safe and secure operation of electrical equipment.

[0059] This allows maintenance of electrical equipment to be performed at low cost.

[0060] The present invention is not limited to the above-described embodiments, but includes various modifications. For example, the above-described embodiments have been specifically described to clearly explain the present invention, and the present invention is not necessarily limited to those having all of the described configurations. Furthermore, a portion of the configuration of one embodiment can be replaced with a portion of the configuration of another embodiment. Furthermore, a portion of the configuration of another embodiment can be added to a portion of the configuration of one embodiment. Furthermore, a portion of the configuration of each embodiment can be deleted, and a portion of another configuration can be added or replaced with a portion of another configuration. [Explanation of symbols]

[0061] 1: Power receiving and distribution equipment, 2: Metal case, 3: control device, 4: Three-phase AC, 5: U phase, 6:V phase, 7: W phase, 8: Electromagnetic waves, 9: voltage divider, 10: Electromagnetic wave dependent partial discharge sensor, 11: Partial discharge occurrence phase detector, 12: Partial discharge detection system, 13: Indicator.

Claims

1. A partial discharge detection system for detecting partial discharge in an electric device having an electric power device housed in a grounded metal case and a control device for controlling the electric power device, an electromagnetic wave dependent partial discharge sensor; a voltage divider measuring device that measures voltage using one of the three phases as a reference phase; and a partial discharge occurrence phase determiner that calculates the number of times that the output of the partial discharge sensor falls within a predetermined range of phase angles of the voltage of the reference phase and voltage, and determines that a phase corresponding to a phase angle range in which the number of times is equal to or greater than a predetermined number is a phase in which a partial discharge occurs. Partial discharge detection system for electrical equipment.

2. 2. The partial discharge detection system for electrical equipment according to claim 1, The partial discharge occurrence phase determination device is The number of times that the partial discharge sensor outputs is counted as one when the partial discharge sensor measures an electromagnetic wave exceeding a first threshold value within a range of a phase angle between the reference phase voltage and a preset voltage. Partial discharge detection system for electrical equipment.

3. 3. The partial discharge detection system for electrical equipment according to claim 2, The partial discharge occurrence phase determination device is determining that the reference phase is a phase in which a partial discharge is occurring when the number of times the output of the partial discharge sensor falls within a phase angle range of 60° to 120° and 240° to 300° of the voltage of the reference phase is equal to or greater than a predetermined number; When the number of times that the output of the partial discharge sensor falls within the phase angles of 0° to 60° and 180° to 240° of the voltage of the reference phase is equal to or greater than a predetermined number, the phase that is shifted 120° in phase from the reference phase is determined to be the phase in which a partial discharge is occurring; When the number of times that the output of the partial discharge sensor falls within the phase angles of 120° to 180° and 300° to 360° of the voltage of the reference phase is equal to or greater than a predetermined number, the phase that is shifted 240° in phase from the reference phase is determined to be the phase in which partial discharge is occurring. Partial discharge detection system for electrical equipment.

4. 4. The partial discharge detection system for electrical equipment according to claim 3, The partial discharge occurrence phase determination device is The output of the partial discharge sensor counts phase angles of 90±15° and 270±15° of the voltage of the reference phase as partial discharges of a first phase; The output of the partial discharge sensor counts phase angles of 30±15° and 210±15° of the voltage of the reference phase as partial discharges of a second phase; The output of the partial discharge sensor counts phase angles of 150±15° and 330±15° of the voltage of the reference phase as partial discharges of the third phase. Partial discharge detection system for electrical equipment.

5. 3. The partial discharge detection system for electrical equipment according to claim 2, The partial discharge occurrence phase determination device is the output of the partial discharge sensor is counted as a first-phase partial discharge when the phase angle of the reference phase voltage is near 90° and near 270°; the output of the partial discharge sensor is counted as a partial discharge of a second phase when the phase angle of the voltage of the reference phase is near 30° and near 210°; The output of the partial discharge sensor is counted as a partial discharge of a third phase when the phase angle of the voltage of the reference phase is around 150° and around 330°. Partial discharge detection system for electrical equipment.

6. The partial discharge detection system for electrical equipment according to any one of claims 1 to 5, The partial discharge detection system further comprises: and a display that receives the determination result from the partial discharge occurrence phase determination device and displays a display corresponding to the phase in which the partial discharge occurred. Partial discharge detection system for electrical equipment.

7. 7. The partial discharge detection system for electrical equipment according to claim 6, The display includes: The determination result is received from the partial discharge occurrence phase determination device, and a flashing light corresponding to the phase in which the partial discharge occurred is performed. Partial discharge detection system for electrical equipment.

8. The partial discharge detection system for electrical equipment according to any one of claims 1 to 5, The partial discharge detection system further comprises: and an alarm that receives the determination result from the partial discharge occurrence phase determination device and issues an alarm corresponding to the phase in which the partial discharge occurred. Partial discharge detection system for electrical equipment.

Images