KR-20260067831-A - IMD(INSULATION MONITORING DEVICE) AND INSULATION MONITORING SYSTEM INCLUDING THE IMD

KR20260067831AKR 20260067831 AKR20260067831 AKR 20260067831AKR-20260067831-A

Abstract

The present invention relates to an insulation monitoring device, and is characterized by comprising: a signal generating unit that applies a pulse signal having a preset voltage to a power line connecting a power conditioning system (PCS) and a load or between the power conditioning system and a power source; a signal measuring unit connected to ground, receiving a measurement signal corresponding to the applied pulse signal from the connected ground, and measuring a detection voltage for calculating an insulation resistance from the received measurement signal; a memory storing a plurality of reference values having different insulation resistance values; and a control unit that calculates the size of the insulation resistance based on the detection voltage, the voltage of the pulse signal, and a preset internal resistance size, detects the operating state of the power conditioning system, and determines the insulation state of the power line by comparing a first reference value among the plurality of reference values with the size of the calculated insulation resistance or comparing a second reference value among the plurality of reference values with the size of the calculated insulation resistance according to the detected operating state of the power conditioning system.

Inventors

박민수
이채린

Assignees

엘에스일렉트릭(주)

Dates

Publication Date: 20260513
Application Date: 20241106

Claims (15)

A signal generation unit that applies a pulse signal having a preset voltage to a power line connecting a power conditioning system (PCS) and a load or between the power conditioning system and a power source; A signal measuring unit connected to ground, receiving a measurement signal corresponding to the applied pulse signal from the connected ground, and measuring a detection voltage for calculating insulation resistance from the received measurement signal; A memory storing a plurality of reference values having different insulation resistance values; and, The magnitude of the insulation resistance is calculated based on the above detection voltage, the voltage of the above pulse signal, and the preset internal resistance magnitude, and An insulation monitoring device characterized by including a control unit that detects the operating state of the power converter and, depending on the detected operating state of the power converter, compares a first reference value among the plurality of reference values with the magnitude of the calculated insulation resistance or compares a second reference value among the plurality of reference values with the magnitude of the calculated insulation resistance to determine the insulation state of the power line.
In paragraph 1, the control unit is, An insulation monitoring device characterized by detecting a voltage change of the power line that increases or decreases above a certain level, and determining the operating state of the power converter based on the detected voltage change of the power line.
In paragraph 2, The above insulation monitoring device is, It further includes a communication unit that performs a communication connection with another insulation monitoring device placed on another power line connected through the power conversion device, and The above control unit is, An insulation monitoring device characterized by receiving a result of detecting a voltage change of the other power line from the other insulation monitoring device, and determining the operating state of the power converter based on the received result of the voltage change of the other power line and the result of detecting the voltage change of the power line.
In paragraph 3, The above load is a battery, and The above insulation monitoring device is, The magnitude of the insulation resistance is calculated from the power line through which direct current flows between the power converter and the battery, and The above other insulation monitoring device is, An insulation monitoring device characterized by calculating the magnitude of insulation resistance from another power line through which alternating current flows between the power conversion device and the power source.
In paragraph 1, The above insulation monitoring device is, It further includes a communication unit that collects information related to the operating status of the power conversion device from the power conversion device, The above control unit is, An insulation monitoring device characterized by determining the operating state of the power converter based on operating state-related information collected from the power converter.
In paragraph 2 or 5, the control unit is, An insulation monitoring device characterized by changing a reference value for determining the insulation state of the power line according to the determined operating state of the power conversion device when the operating state of the power conversion device changes as a result of the above determination.
In paragraph 1, The above first standard value is, It is an insulation resistance reference value for determining the insulation state of a first power line section connecting the power converter and the load or the power converter and the power source when the power converter is not operating, and The above second standard value is, An insulation monitoring device characterized by having a value smaller than the first reference value as an insulation resistance reference value for determining the insulation state of an integrated section in which a second power line section and a first power line section, which are other sections connected through the power conversion device, are integrated, as the power conversion device is driven.
In Paragraph 7, The above memory is, Further storing information on the intrinsic resistance value of the power conversion device and information on the internal resistance magnitude of another insulation monitoring device placed in the second power line section, The above control unit is, The detection voltage is inversely calculated based on the internal resistance of the insulation monitoring device, the detection resistance of the insulation monitoring device, the magnitude of the insulation resistance corresponding to the first reference value, and the voltage of the pulse signal, and An insulation monitoring device characterized by adding the magnitude of the intrinsic resistance of the power conversion device and the magnitude of the internal resistance of the other insulation monitoring device placed in the second power line section to the magnitude of the internal resistance of the insulation monitoring device, and calculating the second reference value based on the magnitude of the added internal resistance and the inversely calculated detection voltage, and the voltage of the pulse signal and the magnitude of the detection resistance of the insulation monitoring device.
In an insulation monitoring system for monitoring the insulation status of a line section to which an energy storage system (ESS) is connected, An insulation monitoring device connected to a first power line section connecting a power source and a power conditioning system (PCS) of the energy storage device, and determining the insulation status of the first power line section; and, It includes an insulation monitoring device connected to a second power line section connecting the power conversion device and the battery of the energy storage device, and determining the insulation status of the second power line section. One of the above insulation monitoring devices, It is a first insulation monitoring device whose operating state is determined based on whether the above-mentioned power conversion device is driven, and Another one of the above insulation monitoring devices is, An insulation monitoring system characterized by being a second insulation monitoring device that determines the insulation state of either one of the first power line section and the second power line section based on a first reference value for determining the insulation state of either one of the first power line section and the second power line section, or a second reference value for determining the insulation state of the integrated section in which the first power line section and the second power line section are integrated, depending on whether the power conversion device is driven.
In Paragraph 9, The first insulation monitoring device and the second insulation monitoring device are An insulation monitoring system characterized by determining the operating state of a power converter based on a voltage change of the first power line or the second power line that increases or decreases above a preset level for a set period of time, or based on operating state information collected from the power converter.
In paragraph 9, the first insulation monitoring device is, When the above power conversion device is in a driven state, it operates in a standby state that does not monitor the insulation state of the first power line, and An insulation monitoring system characterized by operating in an insulation monitoring state that monitors the insulation state of the first power line when the above power conversion device is not in operation.
In Paragraph 9, The above-mentioned first insulation monitoring device is, It is an insulation monitoring device that monitors the insulation status of the first power line section through which alternating current flows, and The above second insulation monitoring device is, An insulation monitoring system characterized by being an insulation monitoring device that monitors the insulation status of the second power line section through which direct current flows.
In Paragraph 9, The above first standard value is, It includes a plurality of insulation resistance sizes for determining the insulation state of a power line as one of a plurality of different states according to the calculated insulation resistance, and The above second standard value is, It includes a plurality of insulation resistance sizes for determining the insulation state of a power line as one of a plurality of different states according to the calculated insulation resistance, and Each of the insulation resistance magnitudes included in the above second reference value is, An insulation monitoring system characterized by having a value smaller than each of the insulation resistance magnitudes included in the corresponding first reference value.
In Paragraph 9, The above first standard value is, It is determined based on 1000 Ohm per 1 volt of power line voltage ((1000 Ohm/V)), and The above second standard value is, An insulation monitoring system characterized by determining 100 Ohm per 1 volt of power line voltage ((100 Ohm/V)).
In paragraph 9, the second insulation monitoring device is, The device further comprises a memory including information on the intrinsic resistance size of the power conversion device and the internal resistance size of the first insulation monitoring device, and An insulation monitoring system characterized by calculating the size of the internal resistance corresponding to the integrated section based on the intrinsic resistance size of the power conversion device, the internal resistance size of the first insulation monitoring device, and the internal resistance of the second insulation monitoring device, and calculating the second reference value based on the calculated internal resistance size of the integrated section and the insulation resistance size corresponding to the first reference value.

Description

Insulation monitoring device and insulation monitoring system including the insulation monitoring device {IMD (INSULATION MONITORING DEVICE) AND INSULATION MONITORING SYSTEM INCLUDING THE IMD} The present invention relates to an insulation monitoring system comprising an insulation monitoring device and a plurality of insulation monitoring devices. The IT (Insulation Terra) grounding method is a grounding system in which neither side of the power line is grounded, and grounding is achieved solely through the load's enclosure. This IT grounding method has the advantage of ensuring continuous system operation, as it allows for sufficient time to locate the fault site without halting system operations even if a ground fault occurs on any of the power lines. Since the system can be operated even in the event of a ground fault, it is necessary to continuously monitor the insulation status of power lines while the system is in operation. Accordingly, the International Electrotechnical Commission (IEC) 61557 standard mandates the installation of insulation monitoring devices capable of monitoring the insulation status of power lines. This insulation monitoring device (IMD) may include a pulse signal generator that forms a circuit between the transmission line and the ground through an insulation resistance formed between the transmission line and the ground, and injects a square wave (pulse) signal into the formed circuit, and a detection resistor for detecting a voltage according to the square wave signal. When the pulse signal generator applies a signal (voltage: Vp) to the ground (Protective Earth, PE), the insulation resistance (Re) is calculated based on a signal (voltage: Vm) in which the voltage is distributed by the virtual resistance (insulation resistance (Re)) between the ungrounded line and the ground and the internal resistance (Ri) of the IMD from the applied signal (Vp), thereby enabling monitoring of the insulation status of the ungrounded line. Meanwhile, as the penetration rate of renewable energy increases, there is a trend toward constructing power grids for load management and the stabilization of renewable energy. As part of this trend, energy storage systems are being installed in power grids. These energy storage systems store excess power generated and, when there is an energy shortage in the power grid, discharge the stored power, thereby enabling more stable and efficient power supply to loads. As such, the energy storage device is installed in the power grid and is connected to an ungrounded line through which alternating current supplied from the power source flows. In this case, the line section from the power source to the energy storage device and the line section connecting the power conditioning system (PCS) installed in the energy storage device and the battery can be connected. In this case, the entire line section from the power source to the battery can be divided into a first line section through which alternating current flows (the line section from the power source to the energy storage device) and a second line section through which direct current flows (the line section from the PCS to the battery), with the PCS as the boundary. In this case, if the above-mentioned PCS is not operated, the first line section and the second line section are not connected to each other and can be divided into separate sections. In this case, the insulation status of each section can be monitored through separate insulation monitoring devices installed in each section, and the insulation status of each section can be monitored according to the insulation resistance reference value set in each insulation monitoring device and the magnitude of the insulation resistance calculated in each section. On the other hand, if the above-mentioned PCS is in operation, the first line section and the second line section are connected to each other, so they can be integrated into a single line section. In this case, any one of the insulation monitoring devices placed in each section can calculate the insulation resistance from the integrated section, and the insulation status of the integrated section can be monitored according to the magnitude of the calculated insulation resistance and the magnitude of the preset insulation resistance. However, when the insulation status of the aforementioned integrated section is monitored, there is a problem in that the magnitude of the insulation resistance calculated may be reduced due to the influence of other integrated line sections. Consequently, even if no leakage current or similar issues occur, the insulation status of the aforementioned integrated section may be falsely detected as damaged, leading to a problem where a false alarm may be output. FIG. 1 is a block diagram illustrating the configuration of an insulation monitoring system that includes an insulation monitoring device for monitoring the insulation status in each line section separated by a power