High voltage switchgear and method for measuring insulation resistance of high voltage switchgear

Abstract

To provide a high-voltage switchgear which is attached to an electric pole and can reduce labor and cost required for inspection work.SOLUTION: A disconnector 11 of a circuit breaker 2 with a disconnector disposed in an upper portion of a power line is provided with a changeover switch that is switched between a current-carrying position in which the circuit breaker is energized and a non-current-carrying position in which the circuit breaker is not energized, an inspection circuit 40 connected at the non-current-carrying position of the changeover switch is formed, and a relay 41 capable of connecting an insulation resistance measuring instrument 51 is disposed in the inspection circuit 40 below the circuit breaker 2 with a disconnector. According to such a configuration, since the insulation resistance can be easily measured by connecting the insulation resistance measuring instrument 51 to the relay 41 by setting the changeover switch to the non-conduction position, the labor and cost of the inspection work can be reduced.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a high-voltage switchgear for energizing a load facility such as a commercial facility, a factory, or a charging station and a distribution line of a power system, and a method for measuring the insulation resistance of the high-voltage switchgear. [Background technology]

[0002] Commercial facilities and factories receive electricity from the power grid of a power company at a higher voltage (for example, 6600 V) than the low voltage used in ordinary households (low voltages such as 100 V or 200 V). These facilities are equipped with high-voltage power receiving devices that include a transformer that transforms high voltage to low voltage and a distribution panel that distributes low-voltage electricity within the facility. For example, Patent Document 1 discloses an example of a high-voltage power receiving device, an interconnection panel (equivalent to a cubicle-type high-voltage power receiving facility) that transforms the high voltage supplied from the power grid and distributes it to charging stations. This interconnection panel is equipped with a disconnecting switch and a circuit breaker, and in the event of an electrical accident such as a short circuit or leakage current, the electrical accident can be isolated from the power grid to prevent it from spreading to other facilities.

[0003] Furthermore, for example, Patent Document 2 discloses a configuration in which a circuit breaker and a transformer are attached to a utility pole erected on the premises of a charging station as the high-voltage power receiving device. In this configuration, electricity distributed from a power grid flows to the transformer via the circuit breaker, and the low-voltage electricity transformed by the transformer is supplied to the charging station. Because each device in this type of high-voltage power receiving device is mounted on a utility pole, it has the advantage of requiring less installation space and lower installation costs compared to the above-mentioned cubicle-type high-voltage power receiving equipment. Furthermore, even with this high-voltage power receiving device, the circuit breaker trips in the event of an electrical accident, preventing the accident from spreading to other facilities. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Publication 2020-22311 [Patent Document 2] Publication No. 2021-36744 Summary of the Invention [Problem to be solved by the invention]

[0005] The aforementioned high-voltage power receiving device is required by law to undergo safety inspections. One type of safety inspection, the annual inspection (performed once a year), involves shutting down the entire facility and inspecting the insulation of the high-voltage section (the part through which high-voltage electricity flows) and the operation of each device. The aforementioned conventional cubicle-type high-voltage power receiving equipment (corresponding to the interconnection panel in Patent Document 1) is installed on the ground, making it relatively easy to inspect the insulation of the high-voltage section, including the circuit breaker and transformer. On the other hand, in the aforementioned configuration in which the circuit breaker and transformer are mounted on a utility pole (the configuration in Patent Document 2), workers must climb to the top of the utility pole on which the circuit breaker is installed to inspect the insulation of the high-voltage section. This requires equipment for working at height, and also equipment to prevent electric shock due to proximity to the distribution line through which high voltage is applied. Such a configuration in which the circuit breaker is mounted on a utility pole poses the problem of increased labor and cost required for inspection work.

[0006] The present invention proposes a high-voltage switchgear that is a device attached to a utility pole and that can reduce the labor and cost required for annual inspection work, and a method for measuring the insulation resistance of the high-voltage switchgear. [Means for solving the problem]

[0007] A first aspect of the present invention is a high-voltage switchgear that is disposed between a distribution line of an electric power system and a load equipment to allow current to flow between the distribution line and the load equipment, the high-voltage switchgear comprising: a disconnector connected to the distribution line; a circuit breaker connected to the distribution line via the disconnector; a circuit breaker with disconnector disposed at the top of a utility pole; a changeover switch that is provided on the disconnector of the circuit breaker with disconnector and that is changeable between an energized position that energizes the distribution line and the circuit breaker and a de-energized position that does not energize the distribution line and the circuit breaker; an inspection circuit that is formed so as to be connected when the changeover switch is in the de-energized position and to be de-connected when the changeover switch is in the energized position, and that connects the circuit breaker to earth via the changeover switch in the de-energized position; and instrument connection means that is disposed below the circuit breaker with disconnector and connected to the inspection circuit, and that is capable of connecting an insulation resistance meter for measuring the insulation resistance of the inspection circuit.

[0008] In this configuration, by setting the selector switch of the disconnector installed at the top of the utility pole to the de-energized position (and the circuit breaker to the energized state), a test circuit is connected to the high-voltage section including the circuit breaker, and by connecting an insulation resistance meter to the instrument connection means of the test circuit, the insulation resistance of the high-voltage section (test circuit) can be easily measured. Furthermore, since the instrument connection means of the present invention is installed below the disconnector-equipped circuit breaker installed at the top of the utility pole, there is no need to climb to the top of the utility pole to measure the insulation resistance, and the person in charge can move away from the distribution line during the measurement. In this way, the configuration of the present invention can reduce the effort and cost required for the annual inspection work described above.

[0009] The configuration of the present invention is preferably used when power is supplied from a power system to a load facility, but is not limited to this and can also be applied when electricity generated by a power generation means (for example, a solar power generation system or a wind power generation system) provided on the load facility side is transmitted to the power system. When transmitting power from the load facility side to the power system, a configuration in which another disconnector is provided on the load facility side of the disconnector-equipped circuit breaker, or a configuration in which the disconnector-equipped circuit breaker is connected to the distribution line via a switch, is preferable.

[0010] In the high-voltage switchgear of the present invention described above, it is proposed that the meter connection means be arranged in a position where an operator can operate the insulation resistance measuring instrument connected to the meter connection means without having to climb the utility pole.

[0011] With this configuration, during annual inspection work, workers can measure the insulation resistance of the inspection circuit without having to climb the utility pole, which further reduces the effort and cost required for this inspection work and makes it easier and safer to measure the insulation resistance.

[0012] On the other hand, the second aspect of the present invention is a method for measuring the insulation resistance of a test circuit in the high-voltage switchgear of the present invention described above, comprising the steps of: a first step of converting a circuit breaker of a circuit breaker equipped with a disconnector from a connected state in which current can be passed through to a disconnected state in which current cannot be passed through; a second step of converting the circuit breaker from an energized position to a non-energized position after the first step while the circuit breaker is held in the disconnected state; a third step of converting the circuit breaker from the disconnected state to a connected state after the second step while the disconnector is held in the non-energized position; and a measurement step of connecting an insulation resistance meter to the instrument connection means of the test circuit formed by the third step to measure the insulation resistance of the test circuit.

[0013] According to this method, it is possible to accurately and stably measure the insulation resistance of a high-voltage switchgear, and it is also possible to improve safety when measuring the insulation resistance. [Effects of the Invention]

[0014] According to the high-voltage switchgear of the present invention, the insulation resistance of the inspection circuit can be easily measured during annual inspection, thereby reducing the effort and cost required for the annual inspection.

[0015] According to the method for measuring the insulation resistance of a high-voltage switchgear of the present invention, the insulation resistance of a test circuit in the high-voltage switchgear can be measured accurately and stably, and the insulation resistance measurement can be carried out safely. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing a high-voltage switchgear 1 according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing a circuit breaker 2 with a disconnector. [Figure 3] FIG. 2 is a circuit diagram showing a circuit breaker 2 with a disconnector. [Figure 4] 2 is a circuit diagram showing the disconnector-equipped breaker 2 and the inspection circuit 40 when current is applied. FIG. [Figure 5] 1A is a circuit diagram showing a tripped state of a disconnector-equipped circuit breaker 2 and FIG. 1B is a circuit diagram showing a completely disconnected state of the disconnector-equipped circuit breaker 2. FIG. [Figure 6] FIG. 1 is a circuit diagram showing a state in which an inspection circuit 40 for measuring insulation resistance is connected. [Figure 7] FIG. 2 is a circuit diagram showing a state in which insulation resistance is measured. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. As shown in Fig. 1 , a high-voltage switchgear 1 of the embodiment is disposed between a distribution line 101 of a power system and a charging stand 102, and is connected to the charging stand 102 via a transformer 3. In such an installation, high-voltage electricity received from the distribution line 101 via the high-voltage switchgear 1 is transformed into low-voltage electricity by the transformer 3 and supplied to the charging stand 102. That is, in the embodiment, the high-voltage switchgear 1 is used as a high-voltage power receiving device that receives high-voltage electricity.

[0018] High-voltage switchgear 1 includes a circuit breaker with a disconnector 2 connected to the distribution line 101, a low-voltage panel 4 that distributes low-voltage electricity transformed by the transformer 3 to charging stations 102, and a control panel 5 for controlling and operating the devices and equipment installed in the high-voltage switchgear 1. The high-voltage switchgear 1 of this embodiment is attached to a utility pole 9 erected on the premises where the charging stations 102 are installed. The circuit breaker with a disconnector 2 is fixed to the upper end of the utility pole 9, and the transformer 3 is installed on the upper part of the utility pole 9 below the circuit breaker with a disconnector 2. The low-voltage panel 4 and control panel 5 are disposed at the bottom of the utility pole 9, and the control panel 5 is disposed at a height that allows an operator (the manager of the high-voltage switchgear 1 or a person requested by the manager) to operate it without using a ladder or the like. Specifically, the control panel 5 is disposed at a height of 1 m to 1.5 m from the base end of the utility pole 9. This allows the worker to operate the control panel 5 easily.

[0019] As described above, the disconnector-equipped circuit breaker 2 is mounted on the upper end of the utility pole 9, making it inaccessible without the use of a ladder or the like. As shown in FIGS. 2 and 3 , the disconnector-equipped circuit breaker 2 of this embodiment comprises a disconnector 11 and a circuit breaker 12 connected in series, and the disconnector 11 and the circuit breaker 12 are housed within a housing 10. The disconnector 11 is disposed on the distribution line 101 side, and the circuit breaker 12 is disposed on the transformer 3 side. Thus, high-voltage electricity distributed from the distribution line 101 is transmitted to the transformer 3 via the disconnector 11 and the circuit breaker 12 in this order. Furthermore, the disconnector-equipped circuit breaker 2 also includes a zero-phase current transformer (ZCT) 15, a current transformer (CT) 16, and a zero-phase voltage detector (ZPD) 17 disposed within the housing 10. These function as sensors for detecting faults. The housing 10 of the disconnector-equipped circuit breaker 2 is connected to earth.

[0020] The disconnector 11 converts the distribution line 101 between an energized state and a de-energized state, and includes a changeover switch 21 that is operable to change its position between an energized position in which the distribution line 101 is energized and a de-energized position in which the distribution line 101 is de-energized. The changeover switch 21 includes an energized terminal 22 connected to the distribution line 101 and a tiltable switch piece 23. By tilting the switch piece 23, the position of the switch piece 23 is changed between the energized position in which the switch piece 23 abuts against the energized terminal 22 and the de-energized position in which the switch piece 23 is separated from the energized terminal 22. When the switch piece 23 is in the energized position, high-voltage electricity distributed from the distribution line 101 is passed through the switch piece 23 to the circuit breaker 12. The changeover switch 21 is provided with an operating means that an operator manually changes the position of the switch piece 23. This operating means is, for example, constituted by a wire (not shown) suspended from the disconnector-equipped circuit breaker 2, and by manually operating this wire, the switch piece 23 of the changeover switch 21 can be switched between an energized position and a de-energized position. This wire is suspended to the bottom of the utility pole 9 and can be operated by the worker. The disconnector 11 is provided with an interlock (not shown) that can switch the changeover switch 21 to the de-energized position only when the circuit breaker 12 is in a cut-off state (disconnected state) to prevent current from passing through.

[0021] The circuit breaker 12 includes a vacuum interrupter 31, a fixed electrode 32 and a movable electrode 33 disposed within the vacuum interrupter 31, and a drive unit 34 for actuating the movable electrode 33. The fixed electrode 32 is connected to the switch piece 23 of the disconnector 11, and the movable electrode 33 is connected to the transformer 3. The movable electrode 33 is disposed within the vacuum interrupter 31 so as to be movable back and forth, and is switched between a connected state in which the movable electrode 33 and the fixed electrode 32 are in contact with each other and a disconnected state in which they are separated. The drive unit 34 moves the movable electrode 33 back and forth, and the movement of the movable electrode 33 switches between the connected state and the disconnected state. The drive unit 34 is also provided with an automatic cut-off switch (not shown) that automatically switches from the connected state to the disconnected state to forcibly cut off current when the zero-phase-sequence current transformer 15, the current transformer 16, and the zero-phase-sequence voltage detector 17 detect a fault. The circuit breaker 12 is also provided with an operating piece 36 (see FIG. 1 ) for operating to change the position of the movable electrode 33 between the connected position and the disconnected position. The operating piece 36 is rotatably disposed on a case body (not shown) of the circuit breaker with disconnector 2, and the movable electrode 33 can be changed between the connected position and the disconnected position by operating a wire (not shown) attached to the operating piece 36 and hanging down. The wire attached to the operating piece 36 hangs down to the bottom of the utility pole 9 and can be operated by the worker. The circuit breaker 12 is also provided with an interlock (not shown) that prevents the movable electrode 33 from being changed from the disconnected state to the connected state when voltage is applied to the transformer 3 side (charging stand 102 side) of the circuit breaker 12.

[0022] When the disconnector 11 of the disconnector-equipped circuit breaker 2 is in the energized position and the circuit breaker 12 is in the connected state, high-voltage electricity distributed from the distribution line 101 flows to the transformer 3, and low-voltage electricity transformed from high voltage by the transformer 3 flows to the low-voltage panel 4. The low-voltage electricity is then sent to the charging stand 102 via the low-voltage panel 4. Note that since conventionally known transformers 3 and low-voltage panel 4 can be used, details thereof will be omitted.

[0023] Next, the main part of the present invention will be described. As shown in Figures 2 and 3, the disconnector-equipped circuit breaker 2 of this embodiment includes a measurement terminal 25 with which the switch piece 23 of the disconnector 11 abuts when the switch piece 23 is in the non-energized position. As a result, the switch piece 23 is moved between the energized position and the non-energized position, and abuts against one of the energized terminal 22 and the measurement terminal 25. As shown in Figure 4, the measurement terminal 25 is connected to a relay 41 disposed in the control panel 5 via a connector 27. The connector 27 is formed of a metal outlet and disposed in the housing 10 of the disconnector-equipped circuit breaker 2, and the measurement terminal 25 is insulated from the housing 10 by the connector 27. The connector 27 makes it relatively easy to connect and disconnect the measurement terminal 25 to and from the relay 41 (first instrument connection terminal 42, described later), which is advantageous in that the connection and disconnection work can be easily performed at the top of the utility pole 9. Since the connector 27 is configured with a commonly known metal outlet, a detailed description thereof will be omitted.

[0024] The relay 41 includes a first instrument connection terminal 42 connected to the measurement terminal 25 and a second instrument connection terminal 43 connected to earth. The first instrument connection terminal 42 is connected to the measurement terminal 25, and the second instrument connection terminal 43 is connected to earth. The relay 41 further includes a terminal connection part 45 that converts the first instrument connection terminal 42 and the second instrument connection terminal 43 between a conducting state where electricity can be passed and a non-conducting state where electricity cannot be passed. The terminal connection part 45 is normally maintained in a conducting state.

[0025] In the high-voltage switchgear 1 of this embodiment, by setting the switch piece 23 of the disconnecting switch 11 to the non-energized position and the circuit breaker 12 to the connected state, an inspection circuit 40 is connected, which connects the circuit breaker 12 and the transformer 3 to earth via a relay 41. This inspection circuit 40 is a circuit in which a section including the circuit breaker 12 and the transformer 3, through which high-voltage electricity wired from the distribution line 101 flows (the so-called high-voltage section), is separated from the distribution line 101 and connected to earth via the switch piece 23. By connecting a predetermined insulation resistance measuring instrument 51, the insulation resistance of this high-voltage section can be measured. The insulation resistance measuring instrument 51 can be easily connected and disconnected to the first and second instrument connection terminals 42, 43 of the relay 41.

[0026] The following describes an insulation resistance measurement method for measuring the insulation resistance of the high-voltage section of the high-voltage switchgear 1 of this embodiment. Here, in the circuit breaker 2 with disconnector, the changeover switch 21 of the disconnector 11 is normally in the energized position and the circuit breaker 12 is normally in the connected state.

[0027] First, an operator (the manager of the high-voltage switchgear 1 or a person requested by the manager) measuring the insulation resistance operates the operating lever 36 of the circuit breaker 12 to separate the fixed electrode 32 and the movable electrode 33 of the circuit breaker 12, as shown in FIG. 5(A) (first step). This places the circuit breaker 12 in an interrupted state, preventing current from passing through it. Then, in this interrupted state, the operator manually shifts the switch lever 23 of the circuit breaker 11 from the energized position to the de-energized position, as shown in FIG. 5(B) (second step). This interrupts current to the circuit breaker 11 and causes the switch lever 23 to abut against the measurement terminal 25. Next, the operator operates the operating lever 36 to bring the fixed electrode 32 and the movable electrode 33 of the circuit breaker 12 into contact with each other, as shown in FIG. 6 (third step). As a result, the circuit breaker 12 is connected to a relay 41 disposed on the control panel 5 via the switch piece 23 of the disconnecting switch 11, and a test circuit 40 that grounds the circuit breaker 12 and the transformer 3 is connected via the switch piece 23. Thereafter, as shown in FIG. 7 , an insulation resistance measuring instrument 51 is connected to the first meter connection terminal 42 and the second meter connection terminal 43, with the terminal connection portion 45 of the relay 41 in the non-energized state. Then, the insulation resistance between the first meter connection terminal 42 and the second meter connection terminal 43 is measured by the insulation resistance measuring instrument 51 (measurement step). By measuring the insulation resistance of the test circuit 40 in this manner, the insulation resistance of the high-voltage section can be measured.

[0028] After the insulation resistance measurement is completed, the insulation resistance measuring device 51 is removed and the terminal connector 45 is returned to the energized state. Then, the circuit breaker 12 is switched to the interrupted state, and the switch piece 23 of the disconnecting switch 11 is switched from the de-energized position to the energized position. After this, the circuit breaker 12 is switched back to the connected state. This restores the normal state in which power can be supplied to the charging stand 102 via the high-voltage switchgear 1.

[0029] The high-voltage switchgear 1 of this embodiment has the following features. (1) Because the charging station 102 is attached to a utility pole 9 erected within the premises of the facility where it is installed, the installation space can be made smaller and the installation costs can be reduced compared to a configuration in which a conventional cubicle-type high-voltage power receiving facility is installed. (2) When the changeover switch 21 of the disconnector 11 is set to the non-energized position that does not conduct current to the distribution line 101, the test circuit 40 that earths the high-voltage section (circuit breaker 12 and transformer 3) is connected via the changeover switch 21, and further, the relay 41 of the control panel 5 is provided with the first meter connection terminal 42 and the second meter connection terminal 43 for measuring the insulation resistance of the test circuit 40, so that the insulation resistance of the high-voltage section can be measured easily and safely. This reduces the effort and cost required for measuring the insulation resistance of the high-voltage section during the statutory annual inspection. (3) In the event of an electrical accident such as a short circuit occurring on the charging stand 102 side, the circuit breaker 12 of the circuit breaker with disconnector 2 cuts off the fault current, thereby isolating the electrical accident without causing a power outage on the power grid side, thereby preventing the accident from spreading to other facilities.

[0030] Furthermore, since cubicle-type high-voltage power receiving equipment is equipped with a transformer, a distribution panel, and protective devices, and is installed on the ground, restrictions on installation space and weight are relatively relaxed, and installation and maintenance work are easy. In contrast, equipment installed on utility poles 9, as in the configuration of this embodiment, is subject to strict restrictions on installation space and weight, making installation and maintenance work less easy compared to a ground-mounted configuration. For these reasons, it can be said that the features of this embodiment described above are extremely useful for a configuration installed on utility poles 9.

[0031] In this embodiment, the charging stand 102 corresponds to the load equipment of the present invention. The first meter connection terminal 42 and the second meter connection terminal 43 of the relay 41 correspond to the meter connection means of the present invention.

[0032] The present invention is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present invention. The embodiment is a high-voltage switchgear 1 for transforming high-voltage electricity supplied from a distribution line 101 into low-voltage electricity and supplying it to a charging station 102, but it is not limited to this and can also be applied as a high-voltage switchgear for supplying electricity to commercial facilities and factories, for example.

[0033] Although the embodiment is directed to supplying power from the distribution line 101 to a load facility (charging stand), it can also be used to transmit power from a power generating means (for example, a solar power generation system) provided in the load facility to the distribution line 101. In such a configuration for transmitting power to the distribution line 101, it is preferable that the circuit breaker with disconnector has a disconnector on the transformer side of the circuit breaker. Furthermore, the configuration of this embodiment can be installed, for example, when a cubicle-type high-voltage power receiving equipment is already installed as a device that receives power from a distribution line. That is, when a new solar power generation system is installed in a load facility where a cubicle-type high-voltage power receiving equipment that receives power from a distribution line is installed and the power is to be sold, it is necessary to install a new cubicle-type high-voltage power receiving equipment for power sales or to replace the old cubicle-type high-voltage power receiving equipment with a larger one. However, this poses the problem of increasing installation space and costs. Therefore, by installing the high-voltage switchgear of the present invention for power sales, it is possible to overcome the problems of installation space and costs. [Explanation of symbols]

[0034] 1 High voltage switchgear 2 Circuit breaker with disconnector 3. Transformer 4 Low-voltage board 5. Control device 9. Electric pole 11 Disconnector 12 Circuit Breaker 15 Zero phase alternator 16 Instrument alternator 17 Zero-phase voltage detector 21 Selector switch 22 Power terminal 23 Switch piece 25 Measurement terminal 27 Connectors 31 Vacuum valve 32 Fixed electrode 33 Movable electrode 34 Drive unit 36 Operation piece 40 Test Circuit 41 Relay 42 First instrument connection terminal (measurement connection means) 43 Second instrument connection terminal (measurement connection means) 51 Insulation resistance measuring instrument 101 Power Distribution Line 102 Charging station (load equipment)

Claims

1. A high-voltage switchgear is arranged between a distribution line of an electric power system and a load facility, and energizes the distribution line and the load facility, a disconnector-equipped circuit breaker provided on an upper portion of a utility pole, the disconnector-equipped circuit breaker including a disconnector connected to the distribution line and a circuit breaker connected to the distribution line via the disconnector; a changeover switch that is provided in the disconnector of the disconnector-equipped circuit breaker and that is converted between an energized position that energizes the distribution line and the circuit breaker and a de-energized position that does not energize the distribution line and the circuit breaker; Equipped with and an inspection circuit configured to be connected when the changeover switch is in the non-energized position and to be disconnected when the changeover switch is in the energized position, and to connect the circuit breaker to earth via the changeover switch in the non-energized position. an instrument connection means that is disposed below the disconnector-equipped breaker and connected to the inspection circuit, and that can connect an insulation resistance measuring instrument for measuring the insulation resistance of the inspection circuit; A high-voltage switchgear comprising:

2. 2. The high-voltage switchgear according to claim 1, wherein the meter connection means is disposed at a position where an operator can operate the insulation resistance measuring instrument connected to the meter connection means without climbing the utility pole.

3. 3. A method for measuring insulation resistance of a high-voltage switchgear according to claim 1 or 2, comprising: a first step of converting a circuit breaker of the circuit breaker with disconnector from a connected state in which current can be passed to a disconnected state in which current cannot be passed; a second step, after the first step, of converting the disconnector from an energized position to a de-energized position while the circuit breaker is maintained in an interrupted state; a third step, after the second step, of converting the circuit breaker from a disconnected state to a connected state while the disconnector is held in a non-energized position; a measuring step of connecting an insulation resistance measuring instrument to the meter connection means of the inspection circuit formed by the third step and measuring the insulation resistance of the inspection circuit; A method for measuring insulation resistance of a high-voltage switchgear, comprising:

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