A method for protecting the stator grounding of a phase modifier based on SCADA data acquisition

Abstract

The present application relates to the technical field of AC power grid reactive power compensation and voltage regulation, and discloses a method for stator ground protection of a phase modifier based on SCADA data acquisition, which establishes the corresponding relationship of a target phase modifier, an outlet circuit breaker, a neutral point grounding loop, an injected stator grounding protection loop and a protection measurement device, synchronously acquires the data of the phase modifier body, a TSI monitoring system, circulating cooling water, lubricating oil and purification and reactive power support control, identifies the operation stage and the reactive power support state, performs working condition compensation on the original grounding resistance, and corrects the grounding protection threshold based on the hot spot equivalent temperature of the cold start temperature rise migration period, so as to form a positive evidence path and a negative evidence path when the electrical quantity, the compensated grounding resistance, the stator temperature field, the shaft voltage or the shaft current deviates, so as to distinguish the strong excitation, cooling, lubrication or TSI abnormality from the real stator grounding risk, and to link the safety removal, cooling and lubrication maintenance and fault tracing, thereby improving the protection reliability.

Description

Technical Field

[0001] This invention relates to the field of reactive power compensation and voltage regulation technology for AC power grids, and in particular to a method for stator grounding protection of synchronous condensers based on SCADA data acquisition. Background Technology

[0002] A synchronous condenser is a type of reactive power support device that connects to the power system. It can provide dynamic reactive power support in new energy power plants, weak power grids, or long-distance transmission systems, thereby improving the system's short-circuit capacity, voltage stability, and power transmission capacity. Distributed synchronous condensers typically consist of a condenser main unit, a step-up transformer, an excitation system, an SFC starting system, a plant power supply and DC system, a cooling system, a lubrication system, a protection system, a thermal system, and an intelligent monitoring system. Its operating status not only affects the safety of the condenser itself but also directly affects the grid connection point's voltage support capacity, short-circuit capacity support capacity, and new energy power transmission capacity. Distributed synchronous condensers have the characteristics of overload capacity, minimal impact of reactive power output on system voltage, ability to increase short-circuit current, and good operational stability.

[0003] Existing stator grounding protection for synchronous condensers mostly focuses on motor protection, typically relying on zero-sequence voltage, third harmonic voltage, or injection-type grounding protection to determine stator winding insulation faults. When the protection criteria meet the operating conditions, an alarm or trip is directly triggered. This method can protect the synchronous condenser itself to a certain extent. However, for synchronous condensers in renewable energy power plants or weak power grids, disconnection of the synchronous condenser may lead to a decrease in reactive power support capacity at the grid connection point, insufficient short-circuit capacity support, and increased voltage fluctuations, thereby affecting the stability of power transmission. Therefore, stator grounding protection logic centered solely on whether a trip occurs is insufficient to meet the safe operation requirements of the power supply and distribution system when the synchronous condenser serves as a reactive power support device for the power grid.

[0004] The above-mentioned and existing related technologies often have the following drawbacks: 1. When a wind farm experiences voltage drop, reactive power deficit, or fault disturbance in its weak power grid, the synchronous condenser needs to enter a state of forced excitation reactive power support. This causes the fundamental zero-sequence voltage, third harmonic voltage, injected grounding resistance, shaft voltage, shaft current, and stator temperature field to deviate from the preset reference synchronously within the same time window. The cause may be the deterioration of the stator insulation to ground, or the increase in forced excitation current, changes in the end electric field, the forced excitation response of the synchronous condensers at the same station, or changes in the cooling boundary. This can lead to the traditional fixed threshold stator grounding protection mistakenly disconnecting the synchronous condenser when the power grid needs reactive power support the most, or delaying the clearing of the real stator grounding fault by mistaking the forced excitation disturbance as a normal support process.

[0005] 2. Due to the continuous changes in speed, injection frequency, excitation state, neutral point grounding circuit parameters, grounding transformer equivalent parameters, cooling water temperature, lubricating oil condition, and TSI vibration state during the static standby, SFC start-up, excitation boost, grid-connected operation, forced excitation reactive power support, and shutdown coasting stages, the fault meaning corresponding to the same original grounding resistance, the same stator temperature deviation, or the same shaft current deviation is inconsistent at different stages. The reason is that electrical quantities, heat quantities, mechanical quantities, cooling quantities, and lubrication quantities have different response times and different measurement boundaries, which leads to the early insulation degradation trend being masked by start-up and shutdown conditions or temperature rise migration process, or misjudging normal start-up and shutdown, cold start temperature rise, and shaft lubrication disturbance as stator grounding risk. Summary of the Invention

[0006] The technical problem to be solved by this invention is that the existing technology has the disadvantage of inconsistent meaning of stator grounding protection quantity fault under the strong excitation support of synchronous condenser and the start-stop operation conditions, which leads to misjudgment of stator grounding risk, wrong disconnection of synchronous condenser or delayed disconnection of real fault. To this end, we propose a method for stator grounding protection of synchronous condenser based on SCADA data acquisition.

[0007] To achieve the above objectives, this application adopts the following technical solution: a method for stator grounding protection of a synchronous condenser based on SCADA data acquisition, comprising the following steps: S1: Establish a correspondence between the target synchronous condenser and its output circuit breaker, neutral point grounding circuit, injection-type stator grounding protection circuit and protection measurement device. The injection-type stator grounding protection circuit is a measurement circuit that injects detection signals into the neutral point grounding circuit and outputs injection voltage, injection current, injection frequency and original grounding resistance. S2: Collect stator grounding protection electrical quantities through protection measurement devices and injection-type stator grounding protection circuit, and simultaneously collect multi-source status data from the target phase condenser body measurement point, TSI monitoring system, circulating cooling water system, lubricating oil and purification system and reactive power support control system through SCADA system; S3: Identify the operating stage and reactive power support status of the target synchronous condenser based on the stator grounding protection electrical quantities and multi-source status data, and perform operating condition compensation on the original grounding resistance to obtain the compensated grounding resistance. S4: Based on the circulating cooling water status data and the synchronous condenser body status data, determine the hot spot equivalent temperature during the cold start temperature rise migration period, and correct the grounding protection threshold according to the hot spot equivalent temperature. S5: When the stator grounding protection electrical quantity, compensation grounding resistance, or stator temperature field, shaft voltage, and shaft current obtained from the synchronous condenser body status data deviate from the preset abnormal reference, a positive evidence path and a negative evidence path are formed respectively. The preset abnormal reference is the protection setting value or historical reference corresponding to the current operating stage, reactive power support state, and cooling boundary. S6: Determine the stator grounding risk level based on the path scores of the positive evidence path and the negative evidence path; S7: Match control actions according to the stator grounding risk level. Among them, the insulation deterioration warning level corresponds to reactive power support limitation control, the high resistance grounding suspected level corresponds to strong excitation lockout control, the grounding fault confirmation level corresponds to station-level coordination control, and the severe grounding requiring disconnection level corresponds to safety disconnection control, cooling and lubrication maintenance control, and fault tracing control.

[0008] Preferably, the correspondence includes at least one of the following: target synchronous condenser number, output circuit breaker number, neutral point grounding circuit number, injection stator grounding protection circuit number, protection measurement device number, excitation system number, and SFC frequency converter starting system number; The stator grounding protection electrical quantities, multi-source status data, and output protection control commands are all attributed to the same target synchronous condenser according to their corresponding relationships. The electrical quantities of stator grounding protection include fundamental zero-sequence voltage, third harmonic voltage on the generator terminal side, third harmonic voltage on the neutral point side, zero-sequence current, injected voltage, injected current, injected frequency, original grounding resistance, output circuit breaker position signal, excitation activation status, and SFC start-up status. Among them, the injected voltage, injected current, injected frequency, and original grounding resistance are output by the injection-type stator grounding protection circuit.

[0009] Preferably, the multi-source status data includes synchronous condenser body status data, TSI monitoring system status data, circulating cooling water status data, lubricating oil and purification status data, and reactive power support status data; the synchronous condenser body status data is collected from the measuring points of the target synchronous condenser body and includes stator bar temperature, stator out-of-line tooth pressure plate temperature, stator non-out-of-line tooth pressure plate temperature, stator core tooth temperature, stator core yoke temperature, slip ring inlet temperature, slip ring outlet temperature, shaft voltage, and shaft current; The TSI monitoring system status data is collected by the TSI monitoring system and includes rotor speed, shaft vibration, bearing vibration, shaft displacement, bearing temperature, vibration alarm status, and vibration protection status. The circulating cooling water status data is collected by the circulating cooling water system and includes the operating status of the cooling water pump, the outlet pressure of the cooling water pump, the supply temperature of the cooling water, the return temperature of the cooling water, the differential pressure of the cooling water filter, the pressure of the expansion tank, the position of the electric regulating valve of the cooling water, the operating status of the circulating water heater and the operating status of the air-cooled fan. Lubricating oil and purification status data are collected by the lubricating oil and purification system, including lubricating oil supply pressure, lubricating oil supply temperature, lubricating oil return temperature, lubricating oil tank level, lubricating oil filter differential pressure, main oil pump operating status, auxiliary oil pump operating status, DC emergency oil pump operating status, oil purification device operating status, and bearing temperature. The reactive power support status data is collected by the reactive power support control system and includes synchronous condenser reactive power, excitation current, excitation voltage, grid connection point bus voltage, dispatch reactive power commands, standby reactive power source status, and station-level coordination status.

[0010] Preferably, identifying the operating phase and reactive power support status of the target synchronous condenser includes: Based on the position signal of the outgoing circuit breaker, the start-up status of the SFC, the excitation engagement status, the rotor speed, the terminal voltage, and the bus voltage at the grid connection point, the operation phase is divided into at least one of the following: static standby phase, SFC start-up phase, excitation boost phase, grid-connected operation phase, forced excitation reactive power support phase, fault disturbance support phase, shutdown coasting phase, and maintenance lockout phase. The reactive power support strength is calculated based on the reactive power of the synchronous condenser, the excitation current, the voltage deviation at the grid connection point, and the reactive power change rate. The reactive power support state is then classified into at least one of the following: conventional reactive power support state, high reactive power support state, and strong excitation reactive power support state. Under forced excitation reactive power support, the deviations of the fundamental zero-sequence voltage, the third harmonic voltage at the generator terminal, the third harmonic voltage at the neutral point, the compensation grounding resistance, the shaft voltage, the shaft current, and the stator temperature field are used to determine the stator grounding risk level according to the path scores of the positive evidence path and the negative evidence path.

[0011] Preferably, the operating condition compensation for the original grounding resistance includes: Calculate the equivalent admittance of the injection circuit based on the injection voltage, injection current, and injection frequency; Based on the equivalent parameters of the grounding transformer, the equivalent parameters of the neutral point grounding circuit, the stator-to-ground distributed capacitance, and the inherent admittance of the injection circuit, the admittance component corresponding to the non-stator insulation factor is subtracted from the equivalent admittance of the injection circuit to obtain the equivalent admittance of the stator-to-ground insulation. The intermediate grounding resistance is calculated using the reciprocal of the real part of the equivalent admittance of the stator-to-ground insulation. Calculate the frequency compensation factor based on the operating stage, SFC startup status, excitation input status, and injection frequency; The intermediate grounding resistance is corrected according to the frequency compensation factor to obtain the compensated grounding resistance; The compensation grounding resistance is the grounding resistance value obtained according to the same compensation rule, corresponding to the static standby stage, SFC start-up stage, excitation boost stage, grid-connected operation stage, and shutdown coasting stage.

[0012] Preferably, determining the hotspot equivalent temperature and correcting the grounding protection threshold includes: Based on the duration of the previous shutdown interval, the site altitude, the operating status of the circulating water heater, the cooling water supply temperature, the cooling water return temperature, the operating status of the cooling water pump, the operating status of the air-cooled fan, and the operating time after the synchronous condenser is started, determine whether the target synchronous condenser is in the cold start temperature rise transition period. When the target synchronous condenser is in the cold start temperature rise transition period, the hot spot equivalent temperature is calculated based on the cooling water supply temperature, stator steady-state temperature rise, thermal time constant and the running time of the synchronous condenser after startup. The grounding protection threshold is corrected based on the hot spot equivalent temperature, preset reference temperature, insulation medium temperature coefficient, frequency compensation factor, and stator-to-ground distributed capacitance correction factor. When the compensation grounding resistance is lower than the grounding protection threshold, an injection-type grounding risk evidence node is generated; When the compensation grounding resistance is not lower than the grounding protection threshold but continues to decrease under the same operating stage, the same reactive power support state and the same cooling boundary, an evidence node of insulation degradation trend is generated. The same cooling boundary is determined by the cooling water supply temperature range, the cooling water return temperature range, the operating status of the cooling water pump, the operating status of the air-cooled fan and the cooling water electric regulating valve position range.

[0013] Preferably, the paths to positive evidence and paths to negative evidence include: The following positive evidence is taken as evidence: a continuous decrease in the compensation grounding resistance, an increase in the fundamental zero-sequence voltage, a shift in the third harmonic voltage ratio, an increase in the local temperature of the stator, and deviations in the shaft voltage and shaft current. Positive evidence paths are formed according to the temporal sequence, spatial correspondence, and consistency of the operational phases among the positive evidence. At least one of the following can be used as counter-evidence: strong excitation reactive power support response, abnormal circulating cooling water status, abnormal lubricating oil and purification status, abnormal TSI monitoring system status, and measurement point failure. A counter-evidence path is formed according to the chronological relationship between the counter-evidence and the positive evidence. When abnormal circulating cooling water pressure, abnormal supply and return water temperature difference, abnormal filter differential pressure, abnormal cooling water valve position, or abnormal air-cooled fan operation occur before the occurrence of stator temperature field abnormality, a counter-evidence path for cooling abnormality is formed. When abnormal lubricating oil supply pressure, abnormal oil temperature, abnormal filter differential pressure, oil pump switching, abnormal bearing temperature, abnormal shaft vibration, or abnormal bearing vibration occur before the occurrence of abnormal shaft voltage or shaft current, a path of evidence for shaft system abnormality is formed. When multiple synchronous condensers at the same station simultaneously enter a strongly excited reactive power support state after the voltage drop at the grid connection point, and the excitation current or reactive power output of multiple synchronous condensers shows a step change in the same direction, a group strongly excited counter-evidence path is formed.

[0014] Preferably, determining the stator grounding risk level includes: extracting the credibility of evidence nodes, the weight of evidence constraint edges, the time decay factor, the evidence level factor, and the key feature coverage factor from the positive evidence path and the negative evidence path, respectively; The path scores for each positive evidence path and each negative evidence path are calculated based on the credibility of the evidence node, the weight of the evidence constraint edge, the time decay factor, the evidence level factor, and the key feature coverage factor. The strength of a positive evidence path is obtained by summing the path scores of the positive evidence path, and the strength of a counter-evidence path is obtained by summing the path scores of the counter-evidence path. The stator grounding risk index is calculated based on the forward path strength, the reverse path strength, the deviation between the compensation grounding resistance and the grounding protection threshold, the degree of local deviation of the stator temperature field, and the degree of continuous deviation of the shaft voltage or shaft current. According to the stator grounding risk index, the stator grounding risk is divided into one of the following: R0 normal level, R1 insulation deterioration warning level, R2 high resistance grounding suspected level, R3 grounding fault confirmed level, and R4 severe grounding requiring disconnection level. The electrical quantity location results are generated based on the changing trends of the fundamental zero-sequence voltage, the third harmonic voltage on the machine terminal side, the third harmonic voltage on the neutral point side, and the compensation grounding resistance. The reliability of fault location is calculated based on the consistency between the electrical quantity location results and the spatial position of the temperature measuring points that deviate from the preset abnormal reference in the stator temperature field. The reliability of fault location is obtained by weighting the electrical location consistency, the spatial consistency of the temperature measuring points, the electrical consistency of the shaft system, and the degree of elimination of the counter-evidence of cooling and lubrication. When the compensation grounding resistance is not lower than the grounding protection action threshold and the fundamental zero-sequence voltage does not reach the preset action threshold, and the counter-proof path strength meets the preset strong counter-proof conditions, the stator grounding risk level is not greater than the R2 high-resistance grounding suspected level.

[0015] Preferably, controls are implemented according to the stator grounding risk level, including: When the stator grounding risk level is R0 (normal level), conventional reactive power support control is executed, and the target synchronous condenser participates in reactive power support according to the dispatch reactive power command or station-level coordination command. When the stator grounding risk level is R1 insulation degradation warning level, sampling density increase control and strong excitation duration limit control are implemented, and the target synchronous condenser is kept in grid-connected operation. When the stator grounding risk level is R2 high-resistance grounding suspected level, the reactive power output upper limit control, the new strong excitation command interlocking control and the high-resistance grounding suspected alarm transmission control are executed. When the stator grounding risk level is R3 grounding fault confirmation level, the station-level coordination control before the protection output is executed, and the station-level coordination equipment sends a backup reactive power capacity pre-allocation instruction to the backup reactive power source. When the stator grounding risk level is R4 (severe grounding requiring disconnection), implement safety disconnection control, SCADA interlocking control, and fault tracing control.

[0016] Preferably, the safety clearance control, SCADA interlock handling control, and fault tracing control include: Open the output circuit breaker of the target synchronous condenser, exit excitation and execute de-excitation, block the SFC restart command, and remove the target synchronous condenser from the list of available reactive power support devices. When the target synchronous condenser enters the stop coasting stage, the operating status of the lubrication system and the circulating cooling water system is maintained or switched according to the rotor speed, bearing temperature, lubricating oil supply pressure, stator temperature, slip ring temperature, cooling water supply temperature and cooling water return temperature. When the rotor speed is higher than the preset safe shutdown speed or the bearing temperature is higher than the preset safe bearing temperature, the main oil pump or auxiliary oil pump is kept running, and the DC emergency oil pump is started when the AC power supply is abnormal. When the stator temperature or slip ring temperature is higher than the preset safe temperature, keep the cooling water pump or air-cooled fan running until the rotor speed, bearing temperature, stator temperature, slip ring temperature and lubricating oil supply pressure all fall into the preset safe shutdown range. The corresponding relationships, stator grounding protection electrical quantities, multi-source status data, positive evidence paths, negative evidence paths, stator grounding risk index, stator grounding risk level, protection action records, station-level coordination records, and SCADA interlocking action sequence are written into the historical database to generate a traceable stator grounding protection fault report.

[0017] The technical effects and advantages of this invention are as follows: This invention does not rely solely on fundamental zero-sequence voltage, third harmonic voltage, or original grounding resistance for fixed threshold judgment. Instead, it first establishes the correspondence between the target synchronous condenser and the output circuit breaker, neutral point grounding circuit, injection-type stator grounding protection circuit, and protection measurement device. Then, it synchronously accesses data from the synchronous condenser body, TSI monitoring system, circulating cooling water system, lubricating oil and purification system, and reactive power support control system through the SCADA system. This ensures that the stator grounding protection quantity and auxiliary system status have clear attribution. By identifying the operating stage and reactive power support status, and by performing condition compensation on the original grounding resistance output by the injection-type stator grounding protection circuit, the operating resistance can be reduced. Measurement deviations caused by frequency and grounding transformer parameter changes during low SFC start-up, excitation boost, grid-connected operation, and shutdown coasting can be corrected by adjusting the grounding protection threshold using the equivalent temperature of hot spots during the cold start temperature rise migration period. This reduces interference from seasonal temperature, cooling boundaries, and startup residual heat on stator insulation judgment. By forming positive and negative evidence paths, it is possible to distinguish between forced excitation reactive power support, cooling anomalies, lubrication anomalies, TSI anomalies, and actual stator grounding risks. This reduces the risk of synchronous condenser mis-clearance and delayed clearing of actual grounding faults. In cases of severe risk, it can also trigger safety clearing, cooling and lubrication maintenance, and fault tracing, thereby improving the protection reliability and operational safety when synchronous condensers participate in reactive power support. Attached Figure Description

[0018] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts: Figure 1 This is a flowchart of the synchronous condenser stator grounding protection method based on SCADA data acquisition according to the present invention; Figure 2 This is a schematic diagram of the circulating cooling water system and measuring points of the synchronous condenser of the present invention; Figure 3 This is a schematic diagram of the lubricating oil and purification system and measuring points of the camera condenser of the present invention; Figure 4 This is a schematic diagram of the synchronous condenser protection measurement and SCADA access of the present invention. Detailed Implementation

[0019] Synchronous condensers are synchronous motors that operate in parallel with the AC power grid. After being accelerated and connected to the grid by an SFC variable frequency drive, they operate at synchronous speed. By adjusting the excitation current, they absorb or send reactive power to the grid. In wind farms or new energy collection stations, synchronous condensers participate in grid connection point voltage regulation, reactive power compensation, and support for weak system short-circuit capacity.

[0020] The SCADA system is a monitoring system that performs data acquisition, monitoring, control, historical storage, and interlocking output for the switching camera and its auxiliary systems. The SCADA system connects to the status data of protection and measurement devices, TSI monitoring system, circulating cooling water system, lubricating oil and purification system, excitation system, SFC frequency converter starting system, station-level coordination equipment, and backup reactive power source.

[0021] The correspondence between the synchronous condenser stator grounding protection indicates the data ownership relationship between the target synchronous condenser and the output circuit breaker, neutral point grounding circuit, injection-type stator grounding protection circuit, protection measuring device, excitation system and SFC frequency converter starting system.

[0022] The correspondence is expressed as follows: (1) In equation (1), This indicates the corresponding relationship of the phase converter stator grounding protection. Indicates the target camera number. Indicates the circuit breaker number at the outlet. This indicates the step-up transformer number. This indicates the number of the neutral point grounding circuit or the injection-type stator grounding protection circuit.

[0023] When collecting the protection and measurement device number, excitation system number, and SFC variable frequency start system number, the corresponding relationship is extended as follows: (2) In equation (2), Indicates the protection measuring device number, Indicates the excitation system number. This indicates the SFC variable frequency start system number.

[0024] Synchronous data frames represent a set of data encapsulated by the SCADA system within the same sampling period, using a unified timestamp, and are represented as: (3) In equation (3), Indicates time Synchronous data frames, Represents the set of electrical quantities. This represents the collection of temperature fields of the stator and the body. Indicates the electrical assembly of the shaft system. This represents the set of states of the TSI monitoring system. Indicates the collection of circulating cooling water. This indicates a collection of lubricating oil and purification systems. This represents a set of reactive power support and power grid level operation data.

[0025] A positive evidence path represents a chain of evidence supporting the establishment of a stator grounding risk; a negative evidence path represents a chain of evidence supporting the establishment of anomalies in electrical quantities, temperature fields, or shaft electrical quantities caused by forced excitation reactive power support, cooling anomalies, lubrication anomalies, TSI anomalies, or measurement point failures, for candidate risk events. The set of positive evidence paths and the set of negative evidence paths are represented as follows: (4) (5) In equation (4), Indicates candidate risk events The set of positive evidence paths, Indicates the first A positive evidence path, Take 1 to , In equation (5), the number of positive evidence paths is represented. Indicates candidate risk events The set of paths to proof by contradiction, Indicates the first One path to proof by contradiction, Take 1 to , This indicates the number of paths to prove the disproving statement.

[0026] Path scores are represented as: (6) In equation (6), Representing a path Path score, Representing a path The fusion value of the credibility of each piece of evidence node in the data. Representing a path The fusion value of the edge weights of the evidence constraints. Representing a path Time decay factor, Representing a path Evidence hierarchy factor Representing a path Key feature coverage factor.

[0027] path The fusion value of the credibility of each evidence node is expressed as follows: (7) In equation (7), Representing a path The Middle The credibility of each evidence node. Take 1 to , Representing a path The number of evidence nodes involved in the calculation. This represents the chain multiplication operator.

[0028] path The fusion value of the weights of each evidence constraint edge is expressed as: (8) In equation (8), Representing a path The Middle The edge weight of each evidence constraint edge, Take 1 to ; Representing a path The number of evidence constraint edges involved in the calculation.

[0029] The time decay factor is expressed as: (9) In equation (9), This indicates the time interval between the time of evidence collection and the current judgment time. This indicates the effective time threshold for the corresponding type of evidence. Indicates the time decay coefficient. This represents the natural exponential function.

[0030] The stator grounding risk index is expressed as: (10) In equation (10), Indicates candidate risk events Stator grounding risk index Indicates the first The path score of a positive evidence path. Indicates the first The path score of the path of proof by contradiction. This represents the path suppression coefficient for proof by contradiction. This represents the summation operator.

[0031] The positive evidence path and the negative evidence path calculate their path scores separately and remain independent of each other. The two paths jointly participate in the stator grounding risk assessment based on their respective path contributions. The path score of each path is jointly determined by the credibility of the evidence node, the weight of the evidence constraint edge, the time decay factor, the evidence level factor, and the key feature coverage factor.

[0032] Example 1 like Figure 1 As shown in the figure, this embodiment illustrates the complete steps of the stator grounding protection method for a synchronous condenser based on SCADA data acquisition.

[0033] Step 1: Establish the correspondence and connect the protection measurement data. SCADA system according to Figure 4 The diagram shows the protection measurement and SCADA access relationship of the synchronous condenser, establishing the correspondence between the target synchronous condenser and the synchronous condenser. The corresponding relationships determine the data attribution among the electrical quantities at the synchronous condenser terminals, the neutral point grounding circuit, the injection-type stator grounding protection circuit, the output circuit breaker, and the step-up transformer side measurements. Figure 4 In the diagram, solid lines represent the connection relationship between the main circuit of the synchronous condenser or between devices, while dashed lines represent the transmission relationship of measured quantities, status quantities, event quantities, control commands, or interlocking signals. Different line types are only used to distinguish the connection relationship between devices and the signal transmission relationship, and do not represent the actual line length or spatial location.

[0034] The SCADA system receives the fundamental zero-sequence voltage from the protection measurement device. Third harmonic voltage at the machine terminal Third harmonic voltage on the neutral point side Original grounding resistance Injection voltage Injected current Injection frequency Output circuit breaker position signal Excitation activation status Demagnetization state, SFC inverter start state And the voltage of the step-up transformer bus.

[0035] The set of electrical quantities is represented as: (11) In equation (11), Indicates time The set of electrical quantities, and the meanings of the other symbols are consistent with those defined in this step.

[0036] Step 2: Collect SCADA multi-source status data according to the synchronous sampling period. The SCADA system operates according to a preset synchronous sampling period. Collect the status data of the target synchronous condenser, the status data of the TSI monitoring system, the status data of the circulating cooling water, the status data of the lubricating oil and purification system, and the status data of the reactive power support, and form a synchronous data frame. .

[0037] Adjusting the temperature field collection of the camera body This includes the temperature of the stator bar, the temperature of the stator output tooth pressure plate, the temperature of the stator non-output tooth pressure plate, the temperature of the stator output tooth, the temperature of the stator non-output tooth, the temperature of the stator output yoke, the temperature of the stator non-output yoke, the temperature of the slip ring inlet air, the temperature of the slip ring outlet air, the temperature of the cold air inlet, the temperature of the cold air outlet, and the temperature of the hot air in the middle of the synchronous condenser.

[0038] Shaft electrical assembly Includes shaft voltage, shaft current, high shaft voltage alarm, low shaft voltage alarm, high shaft current alarm, and low shaft current alarm; TSI monitoring system status set. This includes dual-path rotor speed, X-axis shaft vibration at the output end, Y-axis shaft vibration at the output end, X-axis shaft vibration at the non-output end, Y-axis shaft vibration at the non-output end, X-axis bearing vibration at the output end, Y-axis bearing vibration at the output end, X-axis bearing vibration at the non-output end, Y-axis bearing vibration at the non-output end, shaft vibration protection status, bearing vibration protection status, and unit vibration level 2 alarm status.

[0039] Circulating cooling water collection correspond Figure 2 This includes the operating status of the cooling water pump, the outlet pressure of the cooling water pump, the motor current of the cooling water pump, the inlet and outlet temperatures of the cooling system, the differential pressure of the main cooling water filter, the inlet water temperature of the synchronous condenser, the return water temperature of the synchronous condenser, the inlet and outlet water temperatures of the air cooler, the inlet and outlet water temperatures of the slip ring cooler, the operating status of the circulating water heater, the pressure of the expansion tank, the opening degree of the electric regulating valve for cooling water, and the operating status of the air-cooled fan. Figure 2 In the diagram, TT represents temperature measurement point, PT represents pressure measurement point, DP represents differential pressure measurement point, ZS represents operating status measurement point, and ZV represents valve position measurement point; the solid line represents the direction of circulating cooling water flow, and the dashed line represents the transmission relationship of measurement point signals to the monitoring and control system.

[0040] Lubricating oil and purification system integration correspond Figure 3 This includes lubricating oil supply pressure, lubricating oil supply temperature, lubricating oil return temperature, lubricating oil tank level, oil tank temperature, oil tank vacuum, main oil pump operating status, auxiliary oil pump operating status, DC emergency oil pump operating status, lubricating oil filter differential pressure, oil purification device operating status, accumulator inlet pressure, outlet bearing temperature, and non-outlet bearing temperature.

[0041] Figure 3 In the diagram, P represents the oil supply pressure measuring point, T represents the oil supply temperature measuring point, TE represents the return oil temperature measuring point, ΔP represents the filter differential pressure measuring point, L represents the oil tank level measuring point, WT represents the bearing temperature measuring point at the outlet or non-outlet end, solid circles represent pump or motor operating status measuring points, and QS represents oil purification device status measuring points; solid lines represent lubricating oil pipelines, arrows indicate the flow direction of the corresponding medium, dashed lines are used to indicate the correlation between measuring points or equipment status and external cooling water connections, dashed boxes represent complete equipment units, and shut-off valves, check valves, filters or filter screens are represented by corresponding pipeline symbols.

[0042] Reactive power support and power grid level operation data set Including adjusting the camera's reactive power Active power Excitation current Excitation voltage, grid connection point bus voltage, dispatching reactive power command, reactive power output of other synchronous condensers at the same station, and excitation current of other synchronous condensers at the same station.

[0043] Step 3: Identify the operating phase and reactive power support status. SCADA system based on output circuit breaker position signal Rotor speed, SFC start-up status, excitation activation status, generator terminal voltage, grid connection point bus voltage, and reactive power. The operation phases of the target synchronous condenser are identified, including the static standby phase, SFC start-up phase, excitation boost phase, grid-connected conventional reactive power support phase, forced excitation reactive power support phase, fault disturbance support phase, shutdown coasting phase, and maintenance lockout phase.

[0044] The reactive power support strength is expressed as: (12) In equation (12), Indicates time The reactive power support strength, Indicates time Adjusting the camera's reactive power, Indicates the rated reactive power capacity of the camera. Indicates time The excitation current, Indicates the rated excitation current. Indicates the rate of change of reactive power. Indicates time The voltage deviation at the grid connection point bus, Indicates the rated bus voltage. , , , Let represent the weighting coefficients, and satisfy: (13) when When the value is less than the preset first support threshold, it is determined to be in a normal reactive power support state. When the value is greater than or equal to the first support threshold and less than the preset second support threshold, it is determined to be a high reactive power support state. When the value is greater than or equal to the second support threshold, it is determined to be in a forced excitation reactive power support state.

[0045] Step 4: Perform operating condition compensation on the measured values ​​of the injection-type stator grounding protection. The original grounding resistance measured by the SCADA system for injection-type stator grounding protection Perform working condition compensation.

[0046] According to injection voltage With injected current Calculate the equivalent admittance of the injection loop: (14) In equation (14), This represents the equivalent admittance of the injection circuit.

[0047] Subtracting the equivalent admittance of the grounding transformer, the stator-to-ground distributed capacitance admittance, and the inherent admittance of the injection circuit from the equivalent admittance of the injection circuit, we obtain the equivalent admittance of the stator-to-ground insulation: (15) In equation (15), This represents the equivalent admittance of the stator insulation to ground. This represents the equivalent admittance of the grounding transformer at the current frequency and temperature. Represents the imaginary unit; Represents pi (π). This represents the stator-to-ground distributed capacitance. This represents the intrinsic admittance of the injection circuit.

[0048] The intermediate grounding resistance is expressed as: (16) In equation (16), Indicates the intermediate grounding resistance. express The real part.

[0049] The frequency compensation factor is expressed as: (17) In equation (17), Indicates the frequency compensation factor. Indicates the current injection frequency. Indicates the preset rated injection frequency. Indicates time The output frequency of the SFC inverter starter device This indicates the preset rated power grid frequency.

[0050] The compensation grounding resistance is expressed as: (18) In equation (18), This indicates the compensation grounding resistance.

[0051] Step 5: Calculate the equivalent temperature of hot spots during the cold start temperature rise transition period. SCADA system based on the duration of the previous downtime On-site altitude Circulating water heater commissioning status Cooling water inlet main pipe temperature Determine whether the target camera is in the cold start-up and temperature rise transition period.

[0052] The thermal time constant is expressed as: (19) In equation (19), Indicates the thermal time constant; This indicates the preset basic thermal time constant; This indicates the correction factor for the duration of the previous downtime; Indicates the altitude correction factor; This indicates the correction factor for the operation status of the circulating water heater.

[0053] The duration of the cold start temperature rise transition period is expressed as follows: (20) In equation (20), This indicates the duration of the cold start temperature rise transition period, when the output circuit breaker of the synchronous condenser is closed. Up to the current moment runtime Less than At that time, it was determined that the target camera was in the cold start temperature rise transition period.

[0054] The equivalent temperature of the stator winding hot spot is expressed as: (twenty one) In equation (21), Indicates time The equivalent temperature of the hot spot in the stator winding; Indicates time The temperature of the cooling water inlet manifold, This indicates the steady-state temperature rise of the stator winding hot spot relative to the cooling medium under the preset rated steady-state operation. This indicates the temperature rise shift caused by altitude. This indicates the temperature rise deviation caused by the residual heat in the circulating water heater.

[0055] The altitude correction factor is expressed as: (twenty two) In equation (22), The elevation of the site is indicated in meters. This represents the altitude correction factor.

[0056] Step 6: Dynamically adjust the injection-type grounding protection threshold according to the hotspot equivalent temperature. The SCADA system corrects the threshold for injection-type stator grounding protection based on the hotspot equivalent temperature. (twenty three) In equation (23), Indicates time The dynamic grounding protection threshold, This indicates the calibration threshold at the preset reference temperature. Indicates the preset reference temperature. Indicates the temperature coefficient of the insulating medium. This represents the stator-to-ground distributed capacitance and the correction factor for process differences.

[0057] When the compensation grounding resistance satisfies At that time, the SCADA system generates an injection-type grounding risk evidence node when the compensation grounding resistance does not meet the requirements. However, when the insulation continues to decline under the same operating phase, the same reactive power support state, and the same cooling boundary, the SCADA system generates evidence nodes of insulation degradation trend.

[0058] Step 7: Generate positive evidence path and negative evidence path When the SCADA system detects one or more anomalies, such as an increase in fundamental zero-sequence voltage, a shift in the third harmonic voltage ratio, a decrease in compensation grounding resistance, a deviation in shaft voltage, a deviation in shaft current, or a deviation in the stator temperature field, candidate risk events are generated. And generate a set of positive evidence paths respectively. With the set of proof by contradiction .

[0059] Positive evidence pathways include: (twenty four) (25) (26) In equations (24) to (26), This represents the ratio of the third harmonic voltage. , Indicates the local stator temperature. This indicates the temperature of the area at the wire outlet or non-wire outlet. This indicates the temperature corresponding to the bar or slot. The arrows indicate the axial current and the order of occurrence of the evidence. Indicates a decrease. Indicates an increase, Indicates offset.

[0060] The paths to proof by contradiction include: (27) (28) (29) In equations (27) to (29), This indicates an abnormality in the circulating cooling water system. This indicates an abnormality in the lubricating oil and purification system. This indicates that the TSI monitoring system is in an abnormal state. This indicates an increase in reactive power support strength. This indicates an increase in the excitation current.

[0061] Step 8: Calculate the stator grounding risk index and classify the risk level. The SCADA system calculates candidate risk events according to equations (6) to (10). Stator grounding risk index In the implementation of the project, the stator grounding risk index is extended as follows: (30) In equation (30), The normalized value representing the degree of deviation between the zero-sequence voltage and the third harmonic voltage. The normalized value representing the degree of deviation of the compensating grounding resistance. The normalized value representing the degree of local deviation of the stator temperature field. A normalized value representing the degree of sustained deviation of shaft voltage or shaft current. Indicates the positive evidence path score. Indicates the score for the proof by contradiction path. to Indicates weight, Let represent the path suppression coefficient for proof by contradiction, and satisfy: (31) SCADA system according to The range of values ​​is used to classify stator grounding risk into five levels: R0 is the normal level, R1 is the insulation degradation warning level, R2 is the high resistance grounding suspected level, R3 is the grounding fault confirmation level, and R4 is the severe grounding that needs to be cleared level.

[0062] When the compensation grounding resistance is not lower than the grounding protection operation threshold and the fundamental zero-sequence voltage does not reach the preset operation threshold, the counter-proof path scoring is applied. When the value is greater than or equal to the preset strong counter-evidence threshold, the stator grounding risk level shall not be greater than R2.

[0063] When the stator grounding risk level reaches R2 or above, the SCADA system will follow the corresponding relationship. Determine the machine terminal measurement point, neutral point measurement point, injection-type grounding protection circuit, and output circuit breaker, based on the third harmonic voltage at the machine terminal side. Third harmonic voltage on the neutral point side Fundamental zero-sequence voltage and compensating grounding resistance The electrical quantity positioning results are generated, which include the machine end side area, neutral point side area, outgoing terminal area, or non-outgoing terminal area.

[0064] The reliability of fault location is expressed as follows: (32) In equation (32), Indicates the reliability of fault location. Indicates electrical positioning consistency; This indicates spatial consistency of temperature measurement points. Indicates the electrical consistency of the shaft system. This indicates the degree of exclusion of cooling and lubrication evidence. to Represent the weights and satisfy: (33) Step 9: Determine the availability status of the synchronous condenser's reactive power support according to the risk level. The SCADA system maps stator grounding risk levels R0 to R4 to synchronous condenser reactive power support availability status A to E: R0 corresponds to level A, performing routine reactive power support control; R1 corresponds to level B, maintaining grid-connected reactive power support and increasing sampling density; R2 corresponds to level C, limiting reactive power output upper limit and prohibiting new forced excitation commands; R3 corresponds to level D, notifying the station-level coordinator to prepare a backup reactive power source, and the unit does not undertake new forced excitation commands; R4 corresponds to level E, performing stator grounding protection output actions and removing the unit from the list of available reactive power support devices.

[0065] The available state of reactive power support is represented as follows: (34) In equation (34), Indicates time Adjusting the camera's reactive power support status. This indicates the preset mapping function.

[0066] Step 10: Perform station-level coordination before protecting the exit. When the stator grounding risk reaches R3 or R4 and the synchronous condenser is in grid-connected reactive power support state, the SCADA system performs station-level coordination before the protection output is activated.

[0067] The confidence level for fault identification of this machine is expressed as follows: (35) In equation (35), This indicates the confidence level of fault identification on the machine. Indicates the degree to which electrical quantities exceed limits. Indicates the degree to which the temperature rise exceeds the limit. Indicates the degree of electrical overrun of the shaft system. Indicates the degree of vibration exceeding the limit. , , , Represent the weights and satisfy: (36) same station The correlation index of the group response of the parallel-connected cameras is expressed as follows: (37) In equation (37), Indicates time Group response correlation index Indicates the number of synchronous condensers operating in parallel at the same station. Indicates the first The excitation current of the condenser camera, Indicates the first The excitation current of the condenser camera, Represents a symbolic function. This represents the summation operator.

[0068] when When the electrical quantities of multiple synchronous condensers exceed the preset group threshold and occur in the same direction within the same time window, but the temperature rise, shaft electrical and vibration do not form independent fault evidence, the station-level coordinator determines it as a false positive of the group strong excitation response. The SCADA system enters a high threshold delay observation. During the delay observation period, if the temperature rise, shaft current, compensation grounding resistance and zero-sequence voltage of the machine continue to increase, the station-level coordinator cancels the false positive determination and instructs the machine to perform protection output actions.

[0069] when When the score of the local positive evidence path is less than or equal to the preset group threshold and the score of the local station is greater than the preset independent fault threshold, the station-level coordinator sends a backup reactive power capacity pre-allocation instruction to the SVG, other synchronous condensers or parallel reactive power compensation devices. After the backup reactive power source confirms that it covers the current reactive power output of the local station, the local station executes the protection output action.

[0070] Step 11: Perform protective actions and SCADA interlock procedures. When the stator grounding risk reaches level R4, or level R3 continues to worsen during the delay observation period, the SCADA system executes protection output actions, trips the synchronous condenser output circuit breaker, exits excitation and performs de-excitation, blocks the SFC restart command, and sends the unit's unavailable status to the station-level reactive power control system.

[0071] After the protection action, the SCADA system executes controlled interlocks based on the rotor speed, bearing temperature, lubricating oil supply pressure, stator temperature, cooling water inlet manifold temperature, cooling water outlet manifold temperature, and slip ring temperature during the synchronous condenser's coasting phase: when the rotor speed is higher than the preset safe stop speed, the main oil pump is maintained or switched to the DC emergency oil pump; when the stator temperature or slip ring temperature is higher than the preset safe temperature, the cooling water pump or air-cooled fan is maintained; when the rotor speed, bearing temperature, stator temperature, slip ring temperature, and lubricating oil supply pressure all fall within the preset safe stop range, the cooling water pump, oil pump, and air-cooled fan are controlled to shut down.

[0072] Step 12: Perform fault tracing and evidence path storage. The SCADA system presets the time before a fault occurs. Preset time after fault clearance Synchronous data frames, corresponding relationships, positive evidence paths, negative evidence paths, path scores, dynamic thresholds, risk levels, support availability status, station-level coordination messages, standby reactive capacity responses, and interlocking action sequences within a given time period are written into the historical database.

[0073] The traceability record is represented as follows: (38) In equation (38), This indicates fault tracing records. This represents the synchronized data frames within the time period before and after the fault; It indicates the sequence of protective actions and interlocking actions.

[0074] Example 2 This embodiment illustrates the specific implementation process of cold start temperature rise migration period identification, hot spot equivalent temperature calculation, and grounding protection threshold correction.

[0075] In new energy collection stations, synchronous condensers have cyclical operating conditions of standby, startup, grid connection, shutdown, and restart. After the target synchronous condenser has been shut down, the heat in the stator winding, core, frame, cooling water, lubricating oil, and collector ring cooling branch is released according to different time constants. When restarted, the synchronous condenser is not in a completely cold state, nor is it immediately in a steady-state temperature rise state. The SCADA system reads the time of the previous shutdown, the time of closing the output circuit breaker, the cooling water supply temperature, the cooling water return temperature, the operating status of the circulating water heater, the operating status of the cooling water pump, the operating status of the air-cooled fan, and the site altitude parameters each time it is started, and determines whether the target synchronous condenser is in the cold start temperature rise transition period based on this.

[0076] Specifically, the SCADA system classifies the startup status into fully cold start, partially residual heat start, and short-interval hot restart based on the duration of the previous shutdown interval. When the duration of the previous shutdown interval is greater than or equal to five times the basic thermal time constant, the target synchronous condenser is determined to be close to a fully cold start. When the duration of the previous shutdown interval is greater than or equal to two times the basic thermal time constant but less than five times the basic thermal time constant, it is determined to be a partially residual heat start. When the duration of the previous shutdown interval is less than two times the basic thermal time constant, it is determined to be a short-interval hot restart. The above statuses serve as the basis for determining the value of the correction coefficient for the duration of the previous shutdown interval.

[0077] The SCADA system refreshes every preset sampling period. and When compensating for grounding resistance Less than or equal to At that time, an injection-type grounding risk evidence node is generated. Not lower than However, when the insulation degradation trend evidence node is generated when the temperature drops for multiple consecutive sampling cycles under the same operating stage, the same reactive power support state, and the same cooling boundary, the same cooling boundary includes the cooling water supply temperature being in the same temperature range, the number of operating cooling water pumps being the same, the operating status of the air-cooled fan being the same, and the position of the electric regulating valve of the cooling water being in the same opening range.

[0078] Taking the first synchronous condenser of a new energy collection station in a wind farm as an example, the altitude of the site is... The interval between the previous shutdown and the current startup is 800 meters. The startup time is 36 hours. During this startup, the circulating water heater is in operation, and the cooling water inlet main pipe temperature is... The temperature is 12 degrees Celsius. The preset fundamental thermal time constant is... Take 1800 seconds. Take 1.00, According to formula (22), we take 1.064. If we take 0.92, then Second, Within 2.45 hours after grid connection, the SCADA system marks the target synchronous condenser as a cold start temperature rise migration period, and refreshes the hot spot equivalent temperature and grounding protection threshold according to Equations (21) and (23) during this period.

[0079] exist The equivalent temperature of the hot spot is obtained according to equation (21) at a given time. Celsius, at seconds, Celsius, at seconds, The SCADA system obtains the dynamic grounding protection threshold according to the equivalent temperature of the hot spot mentioned above, and compares the compensation grounding resistance with the dynamic grounding protection threshold at the corresponding time. Therefore, the change in grounding resistance formed by the synchronous condenser during the cold start heating process is no longer directly compared with a single fixed threshold, but is compared with the threshold corresponding to the current thermal state.

[0080] In winter cold start scenarios, the cooling water supply temperature is low, and the initial insulation resistance value is high. If the stator insulation of the target synchronous condenser has already deteriorated early, the original grounding resistance may still not be lower than the fixed protection setting. The SCADA system uses the hot spot equivalent temperature and dynamic grounding protection threshold to place the grounding resistance value at that moment into the benchmark of the current temperature rise migration period for judgment, generating evidence nodes of insulation degradation trend. Conversely, in summer high-temperature cold start scenarios, the initial cooling water temperature is high, and the grounding resistance of healthy insulation may be lower than that in the same state in winter. The SCADA system corrects the grounding protection threshold according to the higher hot spot equivalent temperature, reducing the probability of misjudgment caused by seasonal high temperatures.

[0081] Example 3 This embodiment illustrates how to generate a group strong excitation counter-evidence path by utilizing the excitation changes, bus voltage changes, reactive power command changes, and local multi-source status data of multiple synchronous condensers at the same station in the scenario of voltage drop or reactive power deficit in a wind farm weak grid.

[0082] In wind farm renewable energy collection stations, multiple distributed synchronous condensers typically participate in bus voltage regulation. When the bus voltage at the grid connection point drops, the automatic voltage control system issues a reactive power increase command, or the dispatch system requests increased reactive power support, multiple synchronous condensers may simultaneously enter a strong-excitation reactive power support state. In this state, the excitation current, stator current, and reactive power output of each synchronous condenser increase, accompanied by short-term deviations in the fundamental zero-sequence voltage, third harmonic voltage, shaft voltage, shaft current, and stator temperature field. These deviations are synchronized with the bus voltage drop and reactive power command changes in time and do not necessarily indicate a stator grounding fault.

[0083] The SCADA system collects the excitation current, reactive power output, grid connection point bus voltage, and dispatch reactive power commands of the target synchronous condenser and other synchronous condensers at the same station. The group response correlation index is calculated according to formula (37) for the parallel operation of the synchronous condensers.

[0084] when When the voltage drop at the grid connection point bus or the reactive power command increase occurs earlier than the deviation time of the target synchronous condenser's fundamental zero-sequence voltage, the SCADA system forms a strong excitation counter-evidence path for the group: (39) In equation (39), This indicates a drop in bus voltage at the grid connection point; This indicates that the automatic voltage control system has issued a command to increase reactive power. This indicates that the excitation current of multiple synchronous condensers at the same station is rising in the same direction. This indicates an increase in the fundamental zero-sequence voltage.

[0085] Taking three synchronous condensers operating in parallel as an example, the SCADA system collects data at a certain moment. Ampere per second Ampere per second Amperes per second, the sign function of all three is incremented by one, after substituting into equation (37), If the preset group threshold is 0.7, the SCADA system determines that the synchronous condenser at the same station is in a group strong excitation and same direction response state. At this time, the fundamental zero-sequence voltage of the target synchronous condenser rises briefly, the shaft current deviates briefly, and the stator temperature rises slightly. It first enters the delayed observation state instead of directly forming the R3 or R4 risk level.

[0086] During the delayed observation period, the SCADA system continuously monitors the following data: whether the compensation grounding resistance continues to decrease, whether the third harmonic voltage ratio continues to deviate, whether the local temperature of the target phase converter stator continues to rise relative to the historical benchmark under the same operating conditions, whether the shaft current deviation continues to exist after the excitation process ends, and whether the circulating cooling water, lubricating oil and purification system, and TSI monitoring system can form corresponding counter-evidence paths.

[0087] During the time-lapse observation period, if the following positive evidence path is formed on this machine: (40) In equation (40), This indicates that the compensating grounding resistance is continuously decreasing; Indicates the shift in the third harmonic voltage ratio. This indicates that the temperature of the corresponding bar or slot has increased; This indicates an increase in shaft current.

[0088] If the path score of the positive evidence path shown in equation (40) continues to increase, and the circulating cooling water, lubricating oil and purification system, TSI monitoring system and group strong excitation response do not form a counter-evidence path that meets the preset strong counter-evidence conditions, then the SCADA system will raise the stator grounding risk level from R2 to R3 or R4. If the fundamental zero-sequence voltage, shaft current and stator temperature field of the target synchronous condenser return to the preset reference range after the strong excitation process ends, and the compensation grounding resistance does not continue to decrease, then the SCADA system will keep the risk level no higher than R2 and record the event as a group strong excitation response event.

[0089] In an independent fault scenario, if only the excitation current or shaft current of the target synchronous condenser is abnormal, while other synchronous condensers at the same station do not show changes in their excitation current in the same direction, the SCADA system will calculate... If the value is below the preset group threshold, no group strong excitation counter-evidence path is formed. The decrease in the compensation grounding resistance of the target synchronous condenser, the deviation of the third harmonic voltage ratio, and the increase in local temperature directly enter the positive evidence path scoring. When the risk level reaches R3, the station-level coordinator sends a pre-allocation instruction to the backup reactive power source, and executes the protection output when the risk level reaches R4.

[0090] Example 4 This embodiment illustrates how the circulating cooling water system, lubricating oil and purification system, and TSI monitoring system can serve as data sources for the counter-evidence path in determining stator grounding risk.

[0091] 1. Path to prove the cooling anomaly in the circulating cooling water system When the SCADA system detects that the stator bar temperature, tooth pressure plate temperature, core tooth temperature, or core yoke temperature deviates from the normal reference, the SCADA system reads the circulating cooling water collection... The circulating cooling water system includes the operating status of the cooling water pump, pump outlet pressure, cooling water supply temperature, cooling water return temperature, filter differential pressure, expansion tank pressure, cooling water electric regulating valve position, circulating water heater operating status, and air-cooled fan operating status.

[0092] Figure 2The circulating cooling water system measuring points shown generate cooling water status data during the synchronous acquisition phase. This data is used to identify whether the temperature rise is caused by an abnormal cooling boundary during the cold start temperature rise migration period. It is also used to generate a counter-evidence path for cooling anomalies and determine the corresponding path score during the evidence path generation and risk assessment phases.

[0093] The SCADA system establishes a cooling anomaly counter-evidence path according to the time sequence of anomaly occurrence. When the cooling water pump outlet pressure drops, the filter differential pressure rises, the cooling water supply temperature rises, the cooling water electric regulating valve position is abnormal, or the air-cooled fan stops operating, the cooling anomaly counter-evidence path is formed before the stator temperature field deviates from the occurrence time, i.e., equation (27).

[0094] Among them, when the cooling water pump outlet pressure drops and the cooling water supply temperature rises simultaneously, it indicates a decrease in the cooling medium delivery capacity; when the filter differential pressure rises and the supply and return water temperature difference increases simultaneously, it indicates an increase in the cooling circuit resistance; when the air-cooled fan operates abnormally and the hot air temperature in the middle of the synchronous condenser rises simultaneously, it indicates a decrease in the air cooling capacity. The above counter-evidence paths are included in the calculation of the stator grounding risk index as counter-evidence path scores.

[0095] If there are no abnormalities in cooling water pressure, temperature, valve position, fan or filter differential pressure before the stator temperature field deviation occurs, and the stator temperature deviation is concentrated in the local bar or local tooth pressure plate area, the SCADA system will not generate a strong counter-evidence path for cooling abnormality, and the stator local temperature rise will enter the positive evidence path.

[0096] 2. The lubricating oil and purification system form a path of evidence against shaft system abnormalities. When the SCADA system detects that the shaft voltage or shaft current deviates from the normal reference, the SCADA system reads the lubrication and purification system data. and TSI monitoring system status set The lubricating oil and purification system includes oil supply pressure, oil supply temperature, return oil temperature, oil tank level, filter differential pressure, main oil pump operating status, auxiliary oil pump operating status, DC emergency oil pump operating status, oil purification device operating status, and bearing temperature. The TSI monitoring system status includes rotor speed, shaft vibration, bearing vibration, shaft displacement, bearing temperature, vibration alarm status, and vibration protection status.

[0097] Figure 3 The measurement points shown generate lubricating oil and purification status data and shaft system related status data during the synchronous acquisition phase; during the shaft voltage or shaft current anomaly judgment phase, the sequence of occurrence of oil pressure, oil temperature, filter differential pressure, oil pump switching, bearing temperature and TSI status is combined to form a shaft system anomaly counter-evidence path, and this counter-evidence path is used in the stator grounding risk judgment.

[0098] When the lubricating oil supply pressure drops, the oil temperature is abnormal, the filter differential pressure is abnormal, the oil pump switches, the bearing temperature is abnormal, the shaft vibration is abnormal, or the bearing vibration is abnormal, the occurrence time is earlier than the occurrence time of the shaft voltage or the shaft current deviates from the occurrence time, a reverse proof path of shaft system abnormality is formed, namely equation (28).

[0099] For example, if the lubricating oil supply pressure drops and the bearing temperature at the outlet rises, followed by increased bearing vibration and shaft current deviation, the SCADA system will classify the shaft current deviation as a reverse evidence path for shaft system anomalies. If the shaft current deviation occurs before the oil pressure, oil temperature, bearing temperature and vibration anomalies, and the decrease in compensation grounding resistance and the shift in the third harmonic voltage ratio occur simultaneously, then the shaft current deviation will enter the positive evidence path.

[0100] 3. Competition and scoring between the evidence-by-doing and evidence-for-doing paths The SCADA system retains both positive evidence paths and negative evidence paths separately, and does not merge them into a single anomaly score. The positive evidence path corresponds to the direction in which the stator grounding risk is established, and the negative evidence path corresponds to the direction in which the non-stator grounding cause is established. The path score is calculated according to formula (6), and the negative evidence path strength is determined by the sum of the negative evidence path scores.

[0101] If the compensated grounding resistance is not lower than the grounding protection action threshold and the fundamental zero-sequence voltage does not reach the preset action threshold, and the cooling abnormality counter-proof path, shaft abnormality counter-proof path, or group strong excitation counter-proof path meets the preset strong counter-proof conditions, then the stator grounding risk level value is not greater than R2. If the compensated grounding resistance is lower than the grounding protection action threshold, or the fundamental zero-sequence voltage reaches the preset action threshold, then the strong counter-proof conditions do not restrict the stator grounding risk level from entering R3 or R4.

[0102] Example 5 This embodiment illustrates the process of protection measurement configuration and fault location reliability calculation.

[0103] When the stator grounding risk level reaches R2 or above, the SCADA system will follow the corresponding relationship. The system determines the corresponding terminal measurement point, neutral point measurement point, injection-type stator grounding protection circuit, and output circuit breaker of the target synchronous condenser. The SCADA system then uses the third harmonic voltage at the terminal side... Third harmonic voltage on the neutral point side Fundamental zero-sequence voltage Compensation for grounding resistance The electrical quantity positioning results are generated.

[0104] The electrical quantity location results include at least one of the following regions: machine terminal side region, neutral point side region, outgoing terminal region, and non-outgoing terminal region. The SCADA system is based on the third harmonic voltage ratio. The direction of change, the amplitude of the fundamental zero-sequence voltage, the rate of decrease of the compensation grounding resistance, and the time of the anomaly are used to determine the preliminary electrical location results.

[0105] Subsequently, the SCADA system verifies the consistency between the electrical quantity positioning results and the spatial locations of temperature measurement points in the stator temperature field that deviate from the preset abnormal reference. The temperature measurement points in the stator temperature field that deviate from the preset abnormal reference include stator bar temperature measurement points, outlet end tooth pressure plate temperature measurement points, non-outlet end tooth pressure plate temperature measurement points, core tooth temperature measurement points, and core yoke temperature measurement points. When the electrical quantity positioning results point to the outlet end area, and the outlet end tooth pressure plate temperature, outlet end tooth temperature, or corresponding bar temperature continues to deviate, the spatial consistency of the temperature measurement points is improved. When the electrical quantity positioning results point to the neutral point side area, and the temperature anomaly is concentrated in the non-outlet end area and the cooling anomaly confirms the path, the spatial consistency of the temperature measurement points is reduced.

[0106] The reliability of fault location is calculated according to formula (32), when When the value exceeds a preset location reliability threshold, the SCADA system outputs a stator grounding risk area. This stator grounding risk area includes the machine terminal side area, neutral point side area, outgoing terminal area, and non-outgoing terminal area. If the preset positioning reliability threshold is not reached, the SCADA system outputs the positioning result to be verified and writes the corresponding electrical quantities, temperature field, shaft electrical quantities, cooling water status and lubricating oil status into the fault tracing record.

[0107] Example 6 This embodiment illustrates the complete operation process of the method of this application in a wind farm new energy collection station.

[0108] A wind farm's renewable energy collection station is equipped with multiple distributed synchronous condensers. The target synchronous condenser is connected to the collection station bus via a step-up transformer and participates in bus voltage regulation together with the SVG and parallel reactive power compensation device. The protection and measurement devices of the target synchronous condenser are connected to the fundamental zero-sequence voltage, third harmonic voltage, injection-type stator grounding protection measurement quantity, and output circuit breaker position signal. The SCADA system synchronously collects the target synchronous condenser's status data, TSI monitoring system status data, circulating cooling water status data, lubricating oil and purification status data, and reactive power support status data.

[0109] When a sudden change in wind speed at a wind farm causes a drop in the bus voltage at the grid connection point, the station-level coordination equipment issues a reactive power increase command, and the target synchronous condenser enters a strongly excited reactive power support state. The SCADA system establishes the correspondence between the target synchronous condenser according to S1, generates a synchronization data frame according to S2, calculates the reactive power support strength according to S3, and determines that the target synchronous condenser is in a strongly excited reactive power support state.

[0110] At this point, if the fundamental zero-sequence voltage rises briefly and the shaft current deviates, the SCADA system generates a candidate risk event. Meanwhile, the SCADA system reads the excitation current changes of other synchronous condensers at the same station. If the excitation currents of multiple synchronous condensers rise in the same direction, and this change occurs after the bus voltage drop and the reactive power increase command, a group strong excitation counter-evidence path is formed. If the grounding resistance of the target synchronous condenser does not continue to decrease, the local temperature of the stator does not continue to deviate, and the status of the circulating cooling water and the lubricating oil and purification does not show positive evidence consistent with the stator grounding, then the SCADA system will keep the stator grounding risk level at or below R2 and enter a delayed observation period.

[0111] During the delayed observation period, if the compensation grounding resistance continues to decrease, the third harmonic voltage ratio continues to deviate, the temperature of a certain group of stator bars at the output end continues to rise relative to the historical benchmark under the same operating conditions, and the shaft current deviation continues to exist after the excitation process ends, while the circulating cooling water, lubricating oil and purification system, and TSI monitoring system do not form a strong counter-evidence path, then the SCADA system will increase the forward path strength and raise the risk level to R3 or R4.

[0112] When the risk level reaches R3, the SCADA system limits the reactive power output limit of the target synchronous condenser, prohibits new forced excitation commands, and sends a request for pre-allocation of standby reactive power capacity to the station-level coordination equipment. The station-level coordination equipment issues pre-allocation instructions for standby reactive power capacity to the SVG, other synchronous condensers, or parallel reactive power compensation devices. When the risk level reaches R4, the SCADA system trips the output circuit breaker of the target synchronous condenser, stops excitation and performs de-excitation, blocks the SFC restart command, and removes the target synchronous condenser from the list of available reactive power support devices.

[0113] After the protected exit, the SCADA system reads the rotor speed, bearing temperature, lubricating oil supply pressure, stator temperature, slip ring temperature, cooling water supply temperature, and cooling water return temperature during the stop coasting phase. When the rotor speed is higher than the preset safe stop speed or the bearing temperature is higher than the preset safe bearing temperature, the main oil pump or auxiliary oil pump is kept running. When the AC power supply is abnormal, the DC emergency oil pump is started. When the stator temperature or slip ring temperature is higher than the preset safe temperature, the cooling water pump or air-cooled fan is kept running. After all the above states fall into the preset safe stop range, the SCADA system executes the controlled shutdown of the cooling water pump, oil pump, and air-cooled fan.

[0114] Throughout the fault process, the SCADA system writes the synchronous data frames, positive evidence paths, negative evidence paths, path scores, risk levels, reactive power support availability status, station-level coordination messages, and interlocking action sequences into the historical database, forming a traceable stator grounding protection fault report.

Claims

1. A method for protecting the stator grounding of a synchronous condenser based on SCADA data acquisition, characterized in that, Includes the following steps: S1: Establish a correspondence between the target synchronous condenser and its output circuit breaker, neutral point grounding circuit, injection-type stator grounding protection circuit and protection measurement device. The injection-type stator grounding protection circuit is a measurement circuit that injects a detection signal into the neutral point grounding circuit and outputs the injection voltage, injection current, injection frequency and original grounding resistance. S2: The stator grounding protection electrical quantities are collected through the protection measurement device and the injection-type stator grounding protection circuit, and multi-source status data are simultaneously collected from the target phase condenser body measurement point, TSI monitoring system, circulating cooling water system, lubricating oil and purification system and reactive power support control system through the SCADA system; S3: Identify the operating stage and reactive power support status of the target synchronous condenser based on the stator grounding protection electrical quantity and the multi-source status data, and perform operating condition compensation on the original grounding resistance to obtain the compensated grounding resistance; S4: Based on the circulating cooling water status data and the synchronous condenser body status data, determine the hot spot equivalent temperature during the cold start temperature rise migration period, and correct the grounding protection threshold according to the hot spot equivalent temperature. S5: When the stator grounding protection electrical quantity, the compensation grounding resistance, or the stator temperature field, shaft voltage, and shaft current obtained from the synchronous condenser body status data deviate from the preset abnormal reference, a positive evidence path and a negative evidence path are formed respectively. The preset abnormal reference is the protection setting value or historical reference corresponding to the current operating stage, reactive power support state, and cooling boundary. S6: Determine the stator grounding risk level based on the path scores of the positive evidence path and the negative evidence path; S7: Match control actions according to the stator grounding risk level, wherein the insulation degradation warning level corresponds to reactive power support limitation control, the high resistance grounding suspected level corresponds to strong excitation blocking control, the grounding fault confirmation level corresponds to station-level coordination control, and the severe grounding requiring disconnection level corresponds to safety disconnection control, cooling and lubrication maintenance control, and fault tracing control.

2. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 1, characterized in that, The correspondence includes at least one of the following: target synchronous condenser number, output circuit breaker number, neutral point grounding circuit number, injection-type stator grounding protection circuit number, protection measurement device number, excitation system number, and SFC variable frequency start system number. The stator grounding protection electrical quantities, the multi-source status data, and the output protection control commands are all attributed to the same target synchronous condenser according to the corresponding relationship. The stator grounding protection electrical quantities include fundamental zero-sequence voltage, third harmonic voltage at the generator terminal side, third harmonic voltage at the neutral point side, zero-sequence current, injected voltage, injected current, injected frequency, original grounding resistance, output circuit breaker position signal, excitation activation status, and SFC start-up status. The injected voltage, injected current, injected frequency, and original grounding resistance are output by the injection-type stator grounding protection circuit.

3. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 1, characterized in that, The multi-source status data includes synchronous condenser body status data, TSI monitoring system status data, circulating cooling water status data, lubricating oil and purification status data, and reactive power support status data; the synchronous condenser body status data is collected by the measuring points of the target synchronous condenser body and includes stator bar temperature, stator out-of-line tooth pressure plate temperature, stator non-out-of-line tooth pressure plate temperature, stator core tooth temperature, stator core yoke temperature, slip ring inlet temperature, slip ring outlet temperature, shaft voltage, and shaft current; The TSI monitoring system status data is collected by the TSI monitoring system and includes rotor speed, shaft vibration, bearing vibration, shaft displacement, bearing temperature, vibration alarm status, and vibration protection status. The circulating cooling water status data is collected by the circulating cooling water system and includes the operating status of the cooling water pump, the outlet pressure of the cooling water pump, the supply temperature of the cooling water, the return temperature of the cooling water, the differential pressure of the cooling water filter, the pressure of the expansion tank, the position of the electric regulating valve of the cooling water, the operating status of the circulating water heater and the operating status of the air-cooled fan. The lubricating oil and purification status data are collected by the lubricating oil and purification system and include lubricating oil supply pressure, lubricating oil supply temperature, lubricating oil return temperature, lubricating oil tank level, lubricating oil filter differential pressure, main oil pump operating status, auxiliary oil pump operating status, DC emergency oil pump operating status, oil purification device operating status, and bearing temperature. The reactive power support status data is collected by the reactive power support control system and includes synchronous condenser reactive power, excitation current, excitation voltage, grid connection point bus voltage, dispatching reactive power commands, standby reactive power source status, and station-level coordination status.

4. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 2, characterized in that, Identifying the operating phase and reactive power support status of the target synchronous condenser includes: Based on the position signal of the outgoing circuit breaker, the start-up status of the SFC, the excitation input status, the rotor speed, the terminal voltage, and the bus voltage at the grid connection point, the operation phase is divided into at least one of the following: static standby phase, SFC start-up phase, excitation boost phase, grid-connected operation phase, forced excitation reactive power support phase, fault disturbance support phase, shutdown coasting phase, and maintenance lockout phase. The reactive power support strength is calculated based on the reactive power of the synchronous condenser, the excitation current, the voltage deviation at the grid connection point, and the reactive power change rate. The reactive power support state is then classified into at least one of the following: conventional reactive power support state, high reactive power support state, and strong excitation reactive power support state, based on the reactive power support strength. Under the strongly excited reactive power support state, the deviations of the fundamental zero-sequence voltage, the third harmonic voltage at the generator terminal side, the third harmonic voltage at the neutral point side, the compensation grounding resistance, the shaft voltage, the shaft current, and the stator temperature field are used to determine the stator grounding risk level according to the path scores of the positive evidence path and the negative evidence path.

5. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 4, characterized in that, Compensating the original grounding resistance under operating conditions includes: calculating the equivalent admittance of the injection circuit based on the injection voltage, injection current, and injection frequency; Based on the equivalent parameters of the grounding transformer, the equivalent parameters of the neutral point grounding circuit, the stator-to-ground distributed capacitance, and the inherent admittance of the injection circuit, the admittance component corresponding to the non-stator insulation factor is subtracted from the equivalent admittance of the injection circuit to obtain the equivalent admittance of the stator-to-ground insulation. The intermediate grounding resistance is calculated based on the reciprocal of the real part of the equivalent admittance of the stator-to-ground insulation. Calculate the frequency compensation factor based on the operating phase, the SFC startup state, the excitation input state, and the injection frequency; The intermediate grounding resistance is corrected according to the frequency compensation factor to obtain the compensated grounding resistance; The compensation grounding resistance is the grounding resistance value obtained according to the same compensation rule, corresponding to the static standby stage, SFC start-up stage, excitation boost stage, grid-connected operation stage, and shutdown coasting stage.

6. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 5, characterized in that, Determining the equivalent temperature of the hotspot and correcting the grounding protection threshold includes: Based on the duration of the previous shutdown interval, the site altitude, the operating status of the circulating water heater, the cooling water supply temperature, the cooling water return temperature, the operating status of the cooling water pump, the operating status of the air-cooled fan, and the operating time after the synchronous condenser is started, determine whether the target synchronous condenser is in the cold start temperature rise transition period. When the target synchronous condenser is in the cold start temperature rise migration period, the hot spot equivalent temperature is calculated based on the cooling water supply temperature, stator steady-state temperature rise, thermal time constant and the running time of the synchronous condenser after startup. The grounding protection threshold is corrected according to the hot spot equivalent temperature, preset reference temperature, insulation medium temperature coefficient, frequency compensation factor and stator-to-ground distributed capacitance correction factor. When the compensated grounding resistance is lower than the grounding protection threshold, an injection-type grounding risk evidence node is generated; When the compensation grounding resistance is not lower than the grounding protection threshold but continues to decrease under the same operating stage, the same reactive power support state and the same cooling boundary, an insulation degradation trend evidence node is generated. The same cooling boundary is determined by the cooling water supply temperature range, the cooling water return temperature range, the cooling water pump operating status, the air-cooled fan operating status and the cooling water electric regulating valve position range.

7. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 1, characterized in that, The formation of the positive evidence path and the negative evidence path includes: The positive evidence path is formed by taking at least one of the following as positive evidence: continuous decrease in compensation grounding resistance, increase in fundamental zero-sequence voltage, shift in third harmonic voltage ratio, increase in stator local temperature, deviation of shaft voltage and deviation of shaft current. The positive evidence path is formed by the temporal sequence, spatial correspondence and consistency of operation phase among the positive evidence. At least one of the following is used as counter-evidence: strong excitation reactive power support response, abnormal circulating cooling water status, abnormal lubricating oil and purification status, abnormal TSI monitoring system status, and measurement point failure. The counter-evidence path is formed according to the chronological relationship between the counter-evidence and the positive evidence. When the occurrence of abnormal circulating cooling water pressure, abnormal supply and return water temperature difference, abnormal filter differential pressure, abnormal cooling water valve position, or abnormal air-cooled fan operation precedes the occurrence of the abnormal stator temperature field, a counter-evidence path for cooling abnormality is formed. When abnormal lubricating oil supply pressure, abnormal oil temperature, abnormal filter differential pressure, oil pump switching, abnormal bearing temperature, abnormal shaft vibration, or abnormal bearing vibration occur before the occurrence of abnormal shaft voltage or shaft current, a path of evidence for shaft system abnormality is formed. When multiple synchronous condensers at the same station simultaneously enter a strongly excited reactive power support state after the voltage drop at the grid connection point, and the excitation current or reactive power output of multiple synchronous condensers shows a step change in the same direction, a group strongly excited counter-evidence path is formed.

8. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 7, characterized in that, Determining the stator grounding risk level includes: extracting the credibility of evidence nodes, the weight of evidence constraint edges, the time decay factor, the evidence level factor, and the key feature coverage factor from the positive evidence path and the negative evidence path, respectively; The path scores for each positive evidence path and each negative evidence path are calculated based on the credibility of the evidence node, the weight of the evidence constraint edge, the time decay factor, the evidence level factor, and the key feature coverage factor. The strength of the positive path is obtained by summing the path scores of the positive evidence paths, and the strength of the counter-evidence path is obtained by summing the path scores of the counter-evidence paths. The stator grounding risk index is calculated based on the forward path strength, the reverse path strength, the deviation between the compensation grounding resistance and the grounding protection threshold, the local deviation of the stator temperature field, and the continuous deviation of the shaft voltage or the shaft current. According to the stator grounding risk index, the stator grounding risk is classified into one of the following: R0 normal level, R1 insulation deterioration warning level, R2 high resistance grounding suspected level, R3 grounding fault confirmation level, and R4 severe grounding requiring disconnection level. The electrical quantity positioning results are formed based on the changing trends of the fundamental zero-sequence voltage, the third harmonic voltage on the machine terminal side, the third harmonic voltage on the neutral point side, and the compensation grounding resistance. The reliability of fault positioning is calculated based on the consistency between the electrical quantity positioning results and the spatial position of the temperature measuring points in the stator temperature field that deviate from the preset abnormal reference. The reliability of fault positioning is obtained by weighting the electrical positioning consistency, the spatial consistency of the temperature measuring points, the electrical consistency of the shaft system, and the degree of exclusion of the cooling and lubrication counter-evidence. When the compensation grounding resistance is not lower than the grounding protection action threshold and the fundamental zero-sequence voltage does not reach the preset action threshold, and when the counter-proof path strength meets the preset strong counter-proof condition, the stator grounding risk level is not greater than the R2 high-resistance grounding suspected level.

9. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 8, characterized in that, Control measures implemented according to the aforementioned stator grounding risk level include: When the stator grounding risk level is the R0 normal level, conventional reactive power support control is performed, and the target synchronous condenser participates in reactive power support according to the dispatch reactive power command or the station-level coordination command. When the stator grounding risk level is the R1 insulation degradation warning level, sampling density increase control and strong excitation duration limit control are executed, and the target synchronous condenser remains in grid-connected operation; When the stator grounding risk level is the R2 high-resistance grounding suspected level, the reactive power output upper limit control, the new strong excitation command blocking control, and the high-resistance grounding suspected alarm transmission control are executed. When the stator grounding risk level is the R3 grounding fault confirmation level, the station-level coordination control before the protection output is executed, and the station-level coordination equipment sends a backup reactive power capacity pre-allocation instruction to the backup reactive power source. When the stator grounding risk level is the R4 severe grounding requiring disconnection level, safety disconnection control, SCADA interlocking handling control, and fault tracing control are executed.

10. The method for stator grounding protection of a synchronous condenser based on SCADA data acquisition according to claim 9, characterized in that, The safety disconnection control, the SCADA interlocking handling control, and the fault tracing control include: The output circuit breaker of the target synchronous condenser is disconnected, excitation is stopped and de-excitation is performed, the SFC restart command is blocked, and the target synchronous condenser is removed from the list of available reactive power support devices. When the target synchronous condenser enters the stop coasting stage, the operating status of the lubrication system and the circulating cooling water system is maintained or switched according to the rotor speed, bearing temperature, lubricating oil supply pressure, stator temperature, slip ring temperature, cooling water supply temperature and cooling water return temperature. When the rotor speed is higher than the preset safe shutdown speed or the bearing temperature is higher than the preset safe bearing temperature, the main oil pump or auxiliary oil pump is kept running, and the DC emergency oil pump is started when the AC power supply is abnormal. When the stator temperature or slip ring temperature is higher than the preset safe temperature, keep the cooling water pump or air-cooled fan running until the rotor speed, bearing temperature, stator temperature, slip ring temperature and lubricating oil supply pressure all fall into the preset safe shutdown range. The corresponding relationship, the stator grounding protection electrical quantity, the multi-source status data, the positive evidence path, the negative evidence path, the stator grounding risk index, the stator grounding risk level, the protection action record, the station-level coordination record, and the SCADA interlocking action sequence are written into the historical database to generate a traceable stator grounding protection fault report.

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