Distributed terminal monitoring and positioning system for reducing insulation to ground of direct current system

Abstract

The invention provides a DC system ground insulation reduction distributed terminal monitoring and positioning system. The system comprises a leakage current acquisition module and an insulation reduction distributed monitoring host. Wherein the leakage current acquisition module comprises a plurality of leakage current transmitters and is used for judging and identifying whether the positive electrode insulation is reduced or the negative electrode insulation is reduced according to the positive and negative of monitored leakage current; and the insulation reduction distributed monitoring host is used for calculating a corresponding insulation reduction resistance value by measuring the DC positive and negative voltage to ground and the leakage current. The invention provides a direct-current system ground insulation reduction distributed terminal monitoring and positioning system which can monitor the insulation reduction condition of a specified point of a current feeder loop in real time, feed back the current feeder insulation monitoring condition in real time, measure the ground insulation resistance value of a specific point in a direct-current system and improve the reliability of the direct-current system. The insulation reduction of the positive electrode and the negative electrode is distinguished; the monitored state may be uploaded to the centralized monitoring platform in the form of a hard node or a soft message.

Description

Technical Field

[0001] The invention belongs to the technical field of distributed terminal monitoring of reduced insulation of a DC system to the ground, and in particular relates to a distributed terminal monitoring and positioning system for reduced insulation of a DC system to the ground. Background Art

[0002] Substations, power plants and other DC power supply systems are responsible for providing stable and reliable DC power supply for all station equipment. With the development of intelligent and automated technologies, more and more devices are connected to the DC power supply system, and the devices connected to the DC operating power supply system are getting farther and farther away from the DC power supply system. The insulation monitoring device of the DC power supply system is generally in the integrated power supply panel or each sub-panel. When the access equipment is far away from the insulation monitoring point, when the insulation reduction occurs near the equipment access point, the insulation monitoring of the DC power supply system can only select the insulation reduction in this feeder loop, and fail to locate the specific location.

[0003] At present, various complex situations such as insulation reduction in equipment input measurement often occur, which makes it difficult to locate the insulation reduction fault point, making it difficult for maintenance personnel to troubleshoot the fault and taking a long time to locate the fault, making it inconvenient to quickly troubleshoot and solve the insulation reduction fault point.

[0004] The technology of this patent proposes a fast, high-efficiency online insulation reduction fault point monitoring and positioning technology and method to solve the above problems. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a distributed terminal monitoring and positioning system for insulation reduction of a DC system to the ground, which can monitor the insulation reduction of a specified point of the current feeder loop in real time, and provide real-time feedback on the current insulation monitoring status of this feeder. It can measure the insulation resistance value to the ground at a specific point in the DC system, and distinguish between the insulation reduction of the positive and negative poles; the monitoring status may be uploaded to a centralized monitoring platform in the form of a hard node or a soft message.

[0006] The present invention specifically provides a distributed terminal monitoring and positioning system for DC system-to-ground insulation reduction, a leakage current acquisition module and an insulation reduction distributed monitoring host;

[0007] The leakage current acquisition module includes multiple leakage current sensors, which are used to determine whether the positive electrode insulation is reduced or the negative electrode insulation is reduced by monitoring the positive and negative of the leakage current;

[0008] The insulation reduction distributed monitoring host is used to calculate the corresponding insulation reduction resistance value by measuring the DC positive and negative voltages to ground and the leakage current;

[0009] Furthermore, the insulation reduction distributed monitoring host comprises:

[0010] Power module: used to power the insulation reduction distributed monitoring host and the leakage current sensor;

[0011] MCU module: used to use MCU and DSP to realize corresponding functions as a data processing center;

[0012] Leakage current measurement module: includes a digital leakage current sensor and an analog sensor; used to measure the leakage current from the digital leakage current sensor through communication; obtains the leakage current measured by the analog sensor through high-speed AD analog-to-digital conversion;

[0013] The DC positive and negative voltage to ground measurement module uses a direct voltage divider circuit to monitor the DC positive and negative voltage to ground in real time through high-speed ADC analog-to-digital conversion;

[0014] Human-machine interface module, including buttons and display screen, through which relevant display information can be viewed or designed;

[0015] Relay output module, used for device fault alarm output and insulation degradation alarm output;

[0016] RS485 communication message module, i.e. monitoring center communication, is used to upload relevant measurement quantities and alarm status information;

[0017] Buzzer and LED indicator for sound and light alarm.

[0018] Further, the insulation reduction distributed monitoring host specifically includes the following steps;

[0019] Step 1: The distributed monitoring host measures the DC positive and negative voltages to the ground by reducing the insulation, and then communicates with the leakage current sensor to obtain the leakage current from this point to the input end of the device;

[0020] Step 2, calculating the insulation reduction resistance value of this point through the positive and negative voltages to ground and the leakage current, and determining the early warning value and alarm value of insulation reduction;

[0021] Step 3: Send the insulation reduction fault signal to the monitoring background in the form of RS485 communication soft message; or the communication relay passive node outputs it to the monitoring background.

[0022] Further, the positive and negative voltage signals to ground are processed as follows:

[0023] Computationally separate DC and AC signals;

[0024] Among them, the derivation of the AC signal is as follows:

[0025] Assuming a pure sinusoidal voltage waveform, it can be expressed as follows

[0026]

[0027] Among them, U is the AC voltage signal; ω is the angular frequency; t is time.

[0028] The average value Uavg is calculated by definition

[0029]

[0030] Substituting (1) into (2), we get

[0031]

[0032] In addition, Fourier transform of equation (1) yields

[0033]

[0034] The calculation principle is tested by a multimeter.

[0035]

[0036] The effective value, or the root mean square value, is obtained by definition

[0037]

[0038] The effective value displayed in a common multimeter is calculated by averaging U avg , and then calculate the effective value after correction, that is

[0039] U rms ≈1.1U avg (7)

[0040] Perform FFT transformation on the sampled signal to calculate the spectrum distribution of the AC signal;

[0041] Extract AC voltage signal: U = U0sin(ω0+θ2);

[0042] Calculate the true RMS value of the AC signal;

[0043] The DC signal is the average of the data collected in a single cycle.

[0044] The grounding calculation and identification of the monitoring point are as follows:

[0045] The monitoring points include point A grounding CT1 monitoring point, point B grounding CT2 monitoring point, and point C grounding CT3 monitoring point;

[0046] If point A is grounded:

[0047] The DC leakage current I is measured at the CT1 monitoring point. The current grounding resistance is negative, that is, the current measured at I is negative. The positive and negative states of the current are used to infer that the grounding at point A is negative. The grounding resistance at point A is R y :

[0048] R y =(U n ) / (|I|) (8)

[0049] Where Ry is the grounding resistance value, Un is the negative voltage to ground value, and I is the current value measured by the leakage current sensor;

[0050] If the contact at point A is positively grounded, the current measured by CT1 is positive, and the grounding resistance at point A is R x :

[0051] R x =(U p ) / (|I|) (9)

[0052] Where Rx is the grounding resistance value, Up is the negative voltage to ground value, and I is the current value measured by the leakage current sensor;

[0053] If there are multiple points on a single branch, points B and C are used to monitor multiple grounding points on a single branch;

[0054] The current measured by CT2 is I2, and the current measured by CT3 is I3;

[0055] The calculation of the grounding resistance at point C only considers single-pole grounding:

[0056] When I is 0, the grounding resistance is infinite;

[0057] Positive electrode R x When grounded, I is positive: R x =(U p ) / (|I|) (10);

[0058] Negative electrode R y When grounded, I is negative: R y =(U n ) / (|I|) (11);

[0059] The calculation of the grounding resistance at point B only considers single-pole grounding and has the same polarity as point C.

[0060] When the current at point C is 0 and the current at point B is 0, it means that both points B and C are not grounded;

[0061] When the current at point C is 0 and there is current at point B, the grounding resistance at point B is calculated using formulas (10) and (11); its current is calculated using the current at point B;

[0062] When there is current at point C and it is the same as the current at point B, there is no grounding at point B;

[0063] When there is current at point C and it is not equal to the current at point B, the grounding resistance value at point B is calculated as:

[0064] Positive electrode R x When grounded, I is positive: R x =(U p ) / (|I2-I3|) (12);

[0065] Negative electrode R y When grounded, I is negative: R y =(U n ) / (|I2-I3|) (13);

[0066] I2 and I3 in equations (12) and (13) are the measured currents at points B and C, respectively.

[0067] Compared with the prior art, the beneficial effects are:

[0068] 1. A distributed terminal monitoring and positioning technology and method for the insulation reduction of a DC system to the ground can monitor the insulation reduction of a specified point of the current feeder loop in real time, provide real-time feedback on the insulation monitoring status of the current feeder, measure the insulation resistance value of a specific point in the DC system to the ground, and distinguish the insulation reduction of the positive and negative electrodes; the monitoring status can be uploaded to the centralized monitoring platform in the form of hard nodes or soft messages;

[0069] 2. The present invention does not affect the DC insulation monitoring device in the DC power supply system, and can work simultaneously with the system insulation monitoring device without interfering with each other; it can locate the grounding point of a complex system for online diagnosis of grounding faults in the DC system of a substation; it proposes a monitoring and positioning method and device design application effect, which can improve the work efficiency at the project site and reduce the risks brought by blind wiring. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a structural schematic diagram of a distributed terminal monitoring and positioning system for reducing insulation of a DC system to the ground according to the present invention;

[0071] Figure 2 This is a schematic diagram of the structure of the insulation reduction distributed monitoring host of the present invention;

[0072] Figure 3 It is a schematic diagram of a single-pole grounding equivalent circuit of the present invention;

[0073] Figure 4 Schematic diagram of distributed single-pole grounding measurement and positioning device;

[0074] Figure 5 The main operation interface of the distributed monitoring device for insulation reduction of the present invention;

[0075] Figure 6 This is the main menu interface of the insulation reduction distributed monitoring device of the present invention. DETAILED DESCRIPTION

[0076] The specific implementation of a distributed terminal monitoring and positioning system for reducing insulation of a DC system to the ground according to the present invention is described in detail below with reference to the accompanying drawings.

[0077] The invention provides a distributed terminal monitoring and positioning system for insulation reduction of a DC system to the ground, which can monitor the insulation reduction of a specified point of the current feeder loop in real time, provide real-time feedback on the insulation monitoring status of the current feeder, measure the insulation resistance value of a specific point in the DC system to the ground, and distinguish the insulation reduction of the positive and negative electrodes. The monitoring status can be uploaded to the centralized monitoring platform in the form of hard nodes or soft messages.

[0078] The distributed terminal monitoring and positioning system for reducing insulation of a DC system to the ground of the present invention does not affect a DC insulation monitoring device in a DC power supply system, and can work simultaneously with the system insulation monitoring device without interfering with each other.

[0079] like Figure 1 As shown, the DC system to ground insulation reduction distributed terminal monitoring and positioning system of the present invention, the leakage current acquisition module and the insulation reduction distributed monitoring host;

[0080] The leakage current acquisition module includes multiple leakage current sensors, which are used to determine whether the positive electrode insulation is reduced or the negative electrode insulation is reduced by monitoring the positive and negative of the leakage current;

[0081] The insulation reduction distributed monitoring host is used to calculate the corresponding insulation reduction resistance value by measuring the DC positive and negative voltages to ground and the leakage current;

[0082] like Figure 2 As shown, the insulation reduction distributed monitoring host includes:

[0083] Power module: used to power the insulation reduction distributed monitoring host and the leakage current sensor;

[0084] MCU module: used to use MCU and DSP to realize corresponding functions as a data processing center;

[0085] Leakage current measurement module: includes a digital leakage current sensor and an analog sensor; used to measure the leakage current from the digital leakage current sensor through communication; obtains the leakage current measured by the analog sensor through high-speed AD analog-to-digital conversion;

[0086] The DC positive and negative voltage to ground measurement module uses a direct voltage divider circuit to monitor the DC positive and negative voltage to ground in real time through high-speed ADC analog-to-digital conversion;

[0087] Human-machine interface module, including buttons and display screen, through which relevant display information can be viewed or designed;

[0088] Relay output module, used for device fault alarm output and insulation degradation alarm output;

[0089] RS485 communication message module, i.e. monitoring center communication, is used to upload relevant measurement quantities and alarm status information;

[0090] Buzzer and LED indicator for sound and light alarm.

[0091] The insulation reduction distributed monitoring host specifically includes the following steps;

[0092] Step 1: The distributed monitoring host measures the DC positive and negative voltages to the ground by reducing the insulation, and then communicates with the leakage current sensor to obtain the leakage current from this point to the input end of the device;

[0093] Step 2, calculating the insulation reduction resistance value of this point through the positive and negative voltages to ground and the leakage current, and determining the early warning value and alarm value of insulation reduction;

[0094] Step 3: Send the insulation reduction fault signal to the monitoring background in the form of RS485 communication soft message; or the communication relay passive node outputs it to the monitoring background.

[0095] The present invention monitors the DC positive and negative voltages to ground and the leakage current measured by the leakage current sensor in real time, processes the insulation reduction measurement value and state through a data processing center (MCU), displays it on a display screen, outputs an alarm state through a relay, outputs a sound report through a buzzer and an LED indicator, and outputs relevant information to the monitoring center through RS485.

[0096] When the data processing center (MCU) recognizes that the fault has been restored from the real-time monitoring of the DC positive and negative voltages to ground and the leakage current measured by the leakage current sensor, the related alarms and indications also return to normal.

[0097] Single-pole grounding analysis and feature identification: The most dangerous and common way of DC grounding is single-pole grounding. Only single-pole grounding monitoring is considered here. Figure 3 shown.

[0098] Figure 3 A, B, and C in the figure all belong to the same branch single-pole grounding situation. CT1 DC leakage current detects the leakage current to A; CT3 detects the leakage current of C; CT2 detects the sum of the leakage currents of B and C.

[0099] (1) In the low-frequency injection signal detection system, Figure 5 A, B, C grounding points:

[0100] The positive and negative ground voltage signals at the CT monitoring point are composed of the DC ground voltage and the injected low-frequency signal voltage, which can be converted into digital quantities through a high-speed ADC analog-to-digital converter, and then the AC and DC components can be effectively separated through software FFT algorithms and filtering algorithms.

[0101] The leakage current at the CT monitoring point is composed of the injected low-frequency signal current and the DC current to ground. It can enable a high-precision digital leakage current sensor with an integrated low-frequency current filtering algorithm. It can obtain accurate DC current signal measurement values.

[0102] (2) In the bridge detection system, Figure 3 A, B, C grounding points:

[0103] The positive and negative ground voltage signals at the CT monitoring point are only DC ground voltages, which can be converted into digital quantities through a high-speed ADC, and then the DC voltage can be effectively measured through a software filtering algorithm.

[0104] The leakage current at the CT monitoring point is only the DC current to ground. It can enable a high-precision digital leakage current sensor with an integrated low-frequency current filtering algorithm. It can obtain accurate DC current signal measurement values.

[0105] Positive and negative voltage to ground signal processing

[0106] The calculation separates the DC and AC signals.

[0107] The derivation of the AC signal is as follows:

[0108] First, assume that the pure sinusoidal voltage waveform can be expressed as follows

[0109]

[0110] Among them, U is the AC voltage signal; ω is the angular frequency; t is time.

[0111] The average value Uavg is calculated by definition

[0112]

[0113] Substituting (1) into (2), we get

[0114]

[0115] In addition, Fourier transform of equation (1) yields

[0116]

[0117] The calculation principle is tested by a multimeter.

[0118]

[0119] The effective value (ie, the root mean square value) is obtained by definition

[0120]

[0121] The effective value displayed in a common multimeter is calculated by averaging U avg , and then calculate the effective value after correction, that is

[0122] U rms ≈1.1U avg (7)

[0123] Perform FFT transformation on the sampled signal to calculate the spectrum distribution of the AC signal;

[0124] Extract AC voltage signal: U = U0sin(ω0+θ2);

[0125] Calculate the true RMS value of the AC signal.

[0126] The DC signal is the average of the data collected in a single cycle.

[0127] Grounding calculation and identification of monitoring points

[0128] by Figure 3 For example:

[0129] (1) Point A is grounded. CT1 measures the DC leakage current I. The current grounding resistance is negative, that is, the measured current I is negative.

[0130] The positive and negative states of the current can be used to infer that point A is grounded as a negative pole. y :

[0131] R y =(U n ) / (|I|) (8)

[0132] Among them, Ry is the grounding resistance value, Un is the negative voltage to ground value, and I is the current value measured by the leakage current sensor.

[0133] If the contact at point A is positively grounded, the current measured by CT1 is positive, and the grounding resistance at point A is R x :

[0134] R x =(U p ) / (|I|) (9)

[0135] In formula (9), Rx is the grounding resistance value, Up is the negative voltage to ground, and I is the current value measured by the leakage current sensor.

[0136] (2) Single branch multi-point grounding, such as Figure 5Points B and C in the diagram monitor multiple grounding points in a single branch.

[0137] The current measured by CT2 is I2, and the current measured by CT3 is I3

[0138] Calculation of grounding resistance at point C (only single-pole grounding is considered):

[0139] When I is 0, the grounding resistance is infinite.

[0140] Positive electrode R x When grounded, I is positive: R x =(U p ) / (|I|) (10)

[0141] Negative electrode R y When grounded, I is negative: R y =(U n ) / (|I|) (11)

[0142] Calculation of grounding resistance at point B (only single-pole grounding and the same polarity as point C)

[0143] When the current at point C is 0 and the current at point B is 0, it means that both points B and C are not grounded.

[0144] When the current at point C is 0 and there is current at point B, the grounding resistance at point B is calculated using formulas (10) and (11). The current is calculated using the current at point B.

[0145] When there is current at point C and it is the same as the current at point B, there is no grounding at point B.

[0146] When there is current at point C and it is not equal to the current at point B, the grounding resistance value at point B is calculated as:

[0147] Positive electrode R x When grounded, I is positive: R x =(U p ) / (|I2-I3|) (12)

[0148] Negative electrode R y When grounded, I is negative: R y =(U n ) / (|I2-I3|) (13)

[0149] Note: I2 and I3 in formulas (12) and (13) are the measured currents at points B and C respectively.

[0150] like Figure 4 As shown, the insulation degradation distributed monitoring device:

[0151] The device uses a chip with a Cortex-M0 core, integrating three independent 24-bit ultra-high precision AD sampling, with a sampling rate of 7200 times per second. It can collect AC voltage and DC voltage. The chip has high integration, strong anti-interference ability, fast operation speed and low power consumption.

[0152] The device uses 4 buttons and a 128*64 dot LCD display screen, and the interface can display 4 lines of Chinese characters;

[0153] The device consists of two parts: the host and the CT. The terminal adopts a distributed mode of decentralized measurement and centralized management. This design concept makes the system composition clear and the expansion is convenient and flexible;

[0154] The device does not need to inject any signal into the DC system and has no adverse effect on the DC system;

[0155] The intelligent mutual inductor used in the device can resist the influence of residual magnetism, and the design principle ensures that there will be no zero point drift, and it can operate reliably for a long time;

[0156] The device host can collect and display the voltage and insulation information of the busbar in real time, and can immediately give an alarm if an abnormality occurs. The voltage alarm threshold and insulation alarm threshold value can be freely set, which is flexible and reliable;

[0157] The device has an RS485 serial port and passive alarm contacts, supports standard Modbus protocol, and can communicate with the host computer.

[0158] Device technical parameters:

[0159] Voltage monitoring range: 0~300V (DC220 system);

[0160] Resistance detection range: 0~999KΩ;

[0161] AC detection range: 0~220V;

[0162] DC voltage detection accuracy: <±0.2%;

[0163] Bus resistance detection accuracy: <±5%;

[0164] Branch resistance detection accuracy: <±10%;

[0165] The device can monitor 64 grounding points.

[0166] Device interface design:

[0167] (I) The main operation interface displays positive and negative resistance to ground, AC voltage, bus voltage, positive and negative voltage to ground, insulation, voltage, AC series connection status and number of selected lines, etc. You can turn pages by pressing the [↑] and [↓] keys.

[0168] like Figure 5 As shown, the display description:

[0169] 1>, Positive ground resistance is the real-time measured positive ground resistance value;

[0170] 2> Negative ground resistance is the negative ground resistance value measured in real time;

[0171] 3>, AC voltage is the real-time measurement of the effective value of AC power connected to the DC system;

[0172] 4>, bus voltage is the DC bus voltage value measured in real time;

[0173] 5>, Positive ground voltage is the positive ground voltage value measured in real time;

[0174] 6>, Negative ground voltage is the negative ground voltage value measured in real time;

[0175] 7>, Insulation status:

[0176] When the insulation resistance of the DC system drops to the warning value, "warning" is displayed;

[0177] When the insulation resistance of the DC system drops to the alarm value, "Alarm" is displayed.

[0178] Other conditions are displayed as “normal”;

[0179] 8>, Voltage status:

[0180] When the bus voltage and ground voltage are detected to be abnormal, "positive undervoltage" / "negative undervoltage" / "bus voltage undervoltage" / "bus voltage overvoltage" are displayed;

[0181] Other conditions are displayed as “normal”;

[0182] 9>、AC serial connection status:

[0183] When the AC series voltage is detected to be out of limit, "coupling" is displayed;

[0184] Other situations display "Normal".

[0185] 10>、Number of selected lines: the number of CTs in the DC feeder circuit monitored by the terminal.

[0186] (II) In the main operation interface, press The main menu has two pages. The first line in the upper right corner shows "1 / 3", the page number and the total number of pages.

[0187] like Figure 6 As shown, the main menu interface.

[0188] Display instructions:

[0189] 1>, Branch information: Enter the real-time data display interface to view branch insulation, branch current, and branch ID number;

[0190] 2>, Historical records: Enter to view historical records, including event records, event records, and occurrence time;

[0191] 3>、Parameter setting: enter the parameter setting main menu interface;

[0192] 4>, Branch settings: enter the branch settings interface;

[0193] 5>, Equipment information: information related to this equipment;

[0194] 6>, Factory debugging: mainly used to calibrate relevant parameters (operated by professionals);

[0195] 7>, Manual control: buzzer sound test, constant current source output control interface;

[0196] On the main menu display page, press the up and down keys to switch the cursor to the submenu, and press the confirm key to enter the submenu page.

[0197] Test and results:

[0198] Test environment: In a 220V DC system, the DC system has more than 32 feeder branches.

[0199] (I) Install an insulation detection device that injects low-frequency signals on the DC system. The distributed single-pole grounding measurement and positioning device is used to monitor the 10th and 12th branches on the DC system. The test points are as follows: Figure 3 The 10th branch is tested at point A, and the 12th branch is tested at points B and C. The experimental results are shown in Table 1.

[0200] Table 1

[0201]

[0202] (II) Install the insulation detection device of the bridge method on the DC system. The distributed single-pole grounding measurement and positioning device is used to monitor the 10th and 12th branches on the DC system. The test points are as follows: Figure 3 The 10th branch is tested at point A, and the 12th branch is tested at points B and C. The experimental results are shown in Table 2.

[0203] Table 2

[0204]

[0205]

[0206] Through the above tests, the distributed single-pole grounding measurement and positioning device can be prepared to measure and locate the online positioning of the DC system grounding.

[0207] The technical problem to be solved by the present invention is to provide a distributed terminal monitoring and positioning method for the reduction of insulation between the DC system and the ground in view of the shortcomings of the background technology; the insulation reduction of a specified point of the current feeder loop can be monitored in real time, and the current insulation monitoring status of the feeder can be fed back in real time. The insulation resistance value of a specific point in the DC system to the ground can be measured, and the insulation reduction between the positive and negative poles can be distinguished; the monitoring status can be uploaded to a centralized monitoring platform in the form of a hard node or a soft message.

[0208] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention and are not intended to limit the present invention. A person skilled in the art should understand that the specific implementation of the present invention can be modified or replaced by equivalents, but these modifications or changes are within the scope of protection of the pending claims.

Claims

1. A distributed terminal monitoring and positioning system for reduced insulation of a DC system to the ground, characterized in that: The monitoring and positioning system includes a leakage current acquisition module and an insulation reduction distributed monitoring host; The leakage current acquisition module adopts a leakage current sensor, which is used to judge and identify whether the positive electrode insulation is reduced or the negative electrode insulation is reduced by monitoring the positive and negative of the leakage current; The insulation reduction distributed monitoring host is used to calculate the corresponding insulation reduction resistance value by measuring the DC positive and negative voltages to ground and the leakage current.

2. A method for monitoring and locating distributed terminals for reduced insulation of a DC system to the ground according to claim 1, characterized in that: The insulation reduction distributed monitoring host comprises: Power supply module: used to supply power to the insulation reduction distributed monitoring host and to supply power to the leakage current sensor; MCU module: used to use MCU and DSP to realize corresponding functions as a data processing center; Leakage current measurement module: uses a leakage current sensor, including a digital leakage current sensor and an analog sensor; is used to measure the leakage current from the digital leakage current sensor through communication; obtains the leakage current measured by the analog sensor through high-speed AD analog-to-digital conversion; The DC positive and negative voltage to ground measurement module uses a direct voltage divider circuit to monitor the DC positive and negative voltage to ground in real time through high-speed ADC analog-to-digital conversion; Human-machine interface module, including buttons and display screen, through which relevant display information can be viewed or designed; Relay output module, used for device fault alarm output and insulation degradation alarm output; RS485 communication message module, i.e. monitoring center communication, is used to upload relevant measurement quantities and alarm status information; Buzzer and LED indicator for sound and light alarm.

3. A method for monitoring and locating distributed terminals for reduced insulation of a DC system to the ground according to claim 2, characterized in that: The insulation degradation distributed monitoring host shown specifically includes the following steps: Step 1: The distributed monitoring host measures the DC positive and negative voltages to the ground by reducing the insulation, and then communicates with the leakage current sensor to obtain the leakage current from this point to the input end of the device; Step 2, calculating the insulation reduction resistance value of this point through the positive and negative voltages to ground and the leakage current, and determining the early warning value and alarm value of insulation reduction; Step 3: Send the insulation reduction fault signal to the monitoring background in the form of RS485 communication soft message; or the communication relay passive node outputs it to the monitoring background.

4. A method for monitoring and locating distributed terminals for reduced insulation of a DC system to the ground according to claim 3, characterized in that: The specific method for processing positive and negative voltage signals to ground is as follows: Computationally separate DC and AC signals; Among them, the derivation of the AC signal is as follows: Assuming a pure sinusoidal voltage waveform, it can be expressed as follows Wherein, U is the AC voltage signal; ω is the angular frequency; t is the time; The average value Uavg is calculated by definition Substituting (1) into (2), we get In addition, Fourier transform of equation (1) yields The calculation principle is tested by a multimeter. The effective value, or the root mean square value, is obtained by definition The effective value displayed in a common multimeter is calculated by averaging U avg , and then calculate the effective value after correction, that is U rms ≈1.1U avg (7) Perform FFT transformation on the sampled signal to calculate the spectrum distribution of the AC signal; Extract AC voltage signal: U = U0sin(ω0+θ2); Calculate the true RMS value of the AC signal; The DC signal is the average of the data collected in a single cycle.

5. A method for monitoring and locating distributed terminals for reduced insulation of a DC system to the ground according to claim 4, characterized in that: The grounding calculation and identification of the monitoring point are as follows: The monitoring points include point A grounding CT1 monitoring point, point B grounding CT2 monitoring point, and point C grounding CT3 monitoring point; If point A is grounded: The DC leakage current I is measured at the CT1 monitoring point. The current grounding resistance is negative, that is, the current measured at I is negative. The positive and negative states of the current are used to infer that the grounding at point A is negative. The grounding resistance at point A is R y : R y =(U n ) / (|I|) (8) Where Ry is the grounding resistance value, Un is the negative voltage to ground value, and I is the current value measured by the leakage current sensor; If the contact at point A is positively grounded, the current measured by CT1 is positive, and the grounding resistance at point A is R x : R x =(U p ) / (|I|) (9) Where Rx is the grounding resistance value, Up is the negative voltage to ground value, and I is the current value measured by the leakage current sensor; If there are multiple points on a single branch, points B and C are used to monitor multiple grounding points on a single branch; The current measured by CT2 is I2, and the current measured by CT3 is I3; The calculation of the grounding resistance at point C only considers single-pole grounding: When I is 0, the grounding resistance is infinite; Positive electrode R x When grounded, I is positive: R x =(U p ) / (|I|) (10); Negative electrode R y When grounded, I is negative: R y =(U n ) / (|I|) (11); The calculation of the grounding resistance at point B only considers single-pole grounding and has the same polarity as point C. When the current at point C is 0 and the current at point B is 0, it means that both points B and C are not grounded; When the current at point C is 0 and there is current at point B, the grounding resistance at point B is calculated using formulas (10) and (11); its current is calculated using the current at point B; When there is current at point C and it is the same as the current at point B, there is no grounding at point B; When there is current at point C and it is not equal to the current at point B, the grounding resistance value at point B is calculated as: Positive electrode R x When grounded, I is positive: R x =(U p ) / (|I2-I3|) (12); Negative electrode R y When grounded, I is negative: R y =(U n ) / (|I2-I3|) (13); I2 and I3 in equations (12) and (13) are the measured currents at points B and C, respectively.

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