On-line monitoring method and system for a transformer

Abstract

The embodiment of the application provides an on-line monitoring method and system of a mutual inductor. The on-line monitoring method of the mutual inductor comprises the following steps: acquiring electrical acquisition values, environmental parameters and operating state parameters of a load loop of the mutual inductor to form a multi-source time sequence data stream; acquiring a pre-labeled admittance decoupling reference model; calculating current equivalent admittance measured values of a mutual inductor port according to the electrical acquisition values; decomposing the current equivalent admittance measured values into characteristic admittance reference components, environmental disturbance admittance components, load disturbance admittance components and real state admittance components based on the admittance decoupling reference model; and calculating evaluation indexes of the mutual inductor according to the real state admittance components to perform on-line monitoring on the mutual inductor. The embodiment of the application can accurately decouple environmental temperature and humidity disturbances and load fluctuation disturbances, obtain real admittance components reflecting only insulation deterioration and measurement performance changes of the mutual inductor, and further realize reliable state early warning for specific equipment.

Description

Technical Field

[0001] This application relates to the field of instrument transformer detection technology, specifically to an online monitoring method and system for instrument transformers. Background Technology

[0002] Instrument transformers are critical equipment in power systems, and accurate monitoring of their operating status is of great significance for power grid safety, energy metering, and relay protection. Online monitoring methods for instrument transformers typically assess insulation status by collecting leakage current at the end screen to calculate the dielectric loss factor and equivalent capacitance, or by extracting characteristic parameters from voltage and current signals to determine whether metering errors exceed tolerances.

[0003] However, the actual operating environment of instrument transformers is highly complex, and their operating conditions are affected by various factors such as temperature, humidity, and load fluctuations. The fluctuations in measured values ​​caused by these complex operating disturbances are often on the same order of magnitude as those caused by insulation degradation or increased metering errors, making them difficult to distinguish effectively. The measured values ​​cannot accurately reflect the actual operating state of the instrument transformer, easily misinterpreting normal environmental fluctuations as equipment malfunctions, or masking true performance degradation within the disturbance signals. Maintenance personnel find it difficult to accurately determine the operating status of the instrument transformer based on existing monitoring results, and timely and reliable status warnings are also impossible. Summary of the Invention

[0004] This application provides an online monitoring method and system for instrument transformers, which can accurately decouple environmental temperature and humidity disturbances and load fluctuation disturbances, accurately isolate the admittance changes caused by environmental temperature and humidity and load fluctuations, and obtain the true admittance component that only reflects the insulation degradation and metering performance changes of the instrument transformer itself, thereby achieving reliable status early warning for specific equipment.

[0005] The online monitoring method for a current transformer according to this application includes: acquiring electrical acquisition values, environmental parameters, and operating status parameters of the load circuit of the current transformer to form a multi-source time series data stream; acquiring a pre-calibrated admittance decoupling benchmark model, wherein the admittance decoupling benchmark model includes a characteristic admittance benchmark of the current transformer port, a first sensitivity parameter of the influence of environmental factors on the equivalent admittance of the current transformer port, and a second sensitivity parameter of the influence of load factors on the equivalent admittance of the current transformer port; calculating the current equivalent admittance measured value of the current transformer port based on the electrical acquisition values ​​of the current transformer; decomposing the current equivalent admittance measured value into a characteristic admittance benchmark component corresponding to the standard operating condition, an environmental disturbance admittance component caused by the deviation of environmental parameters from the standard operating condition, a load disturbance admittance component caused by the change of the operating status of the load circuit, and a true state admittance component based on the true state admittance component; and calculating the evaluation index of the current transformer based on the true state admittance component to perform online monitoring of the current transformer.

[0006] In some embodiments, the characteristic admittance reference is defined as the equivalent admittance value of the transformer port under preset standard environmental conditions, with a rated electrical quantity applied and the load circuit at a preset typical operating point; the first sensitivity parameter is determined based on the deviation of the equivalent port admittance relative to the characteristic admittance reference under different temperature and humidity combinations of the transformer, the first sensitivity parameter characterizing the degree of influence of temperature change alone, humidity change alone, and simultaneous temperature and humidity change on the equivalent port admittance; the second sensitivity parameter is determined based on the dynamic correlation between the equivalent port admittance and the operating state parameters of the load circuit during normal operation of the transformer, the second sensitivity parameter characterizing the degree of influence and dynamic response characteristics of the active power, reactive power, and switch state changes of the load circuit on the equivalent port admittance.

[0007] In some implementations, the step of decomposing the current equivalent admittance measured value into a characteristic admittance reference component corresponding to the standard operating condition, an environmental disturbance admittance component caused by the deviation of the environmental parameters from the standard operating condition, a load disturbance admittance component caused by changes in the operating state of the load circuit, and a true state admittance component based on the admittance decoupling reference model and according to the environmental parameters and the operating state parameters of the load circuit, includes: determining the environmental disturbance admittance component based on the deviation of the environmental parameters from the calibration reference value and the first sensitivity parameter; determining the load disturbance admittance component based on the operating state parameters of the load circuit and the second sensitivity parameter; and subtracting the characteristic admittance reference component, the environmental disturbance admittance component, and the load disturbance admittance component sequentially from the current equivalent admittance measured value to obtain the true state admittance component.

[0008] In some embodiments, the online monitoring method for the instrument transformer further includes: obtaining the equipment type connected to the secondary side of the instrument transformer by parsing a substation configuration description file, a system specification description file, or an equipment ledger database. Obtaining the pre-calibrated admittance decoupling benchmark model includes: obtaining matching parameters from a preset model library based on the equipment type connected to the secondary side of the instrument transformer to determine the characteristic admittance benchmark, the first sensitivity parameter, and the second sensitivity parameter.

[0009] In some embodiments, obtaining matching parameters from a preset model library based on the type of equipment connected to the secondary side of the transformer includes: determining the load characteristic classification of the load circuit according to the equipment type, wherein the load characteristic classification includes continuous load, event-type load, and mixed load, wherein the continuous load is characterized by continuous changes in active and reactive power, the event-type load is characterized by abrupt changes in switching state, and the mixed load has both continuous and event-type characteristics; when the load characteristic classification of the load circuit is a continuous load, obtaining the impulse response coefficient sequence of active and reactive power to the port equivalent admittance as the parameter set of the second sensitivity parameter; when the load characteristic classification of the load circuit is an event-type load, obtaining the admittance step coefficient and decay time constant caused by the change in switching state as the parameter set of the second sensitivity parameter; when the load characteristic classification of the load circuit is a mixed load, obtaining the impulse response coefficient sequence of active and reactive power to the port equivalent admittance, as well as the admittance step coefficient and decay time constant caused by the change in switching state as the parameter set of the second sensitivity parameter.

[0010] In some implementations, the step of decomposing the current equivalent admittance measured value into a characteristic admittance reference component corresponding to the standard operating condition, an environmental disturbance admittance component caused by the deviation of environmental parameters from the standard operating condition, a load disturbance admittance component caused by changes in the operating state of the load circuit, and a true state admittance component based on the admittance decoupling reference model and according to the environmental parameters and the operating state parameters of the load circuit, includes: when the load characteristics of the load circuit are classified as continuous loads, obtaining the load disturbance admittance component by convolving and summing the active power sequence and reactive power sequence within a preset time window with the corresponding impulse response coefficients; when the load characteristics of the load circuit are classified as event-type loads, obtaining the load disturbance admittance component through the step amount of the switching state change event and the recovery function that decays with the event occurrence time; when the load characteristics of the load circuit are classified as mixed loads, obtaining the load disturbance admittance component by superimposing the convolution summation result corresponding to the continuous load with the step decay result corresponding to the event-type load.

[0011] In some embodiments, calculating the evaluation index of the current transformer based on the true state admittance component for online monitoring of the current transformer includes: determining a metering error index based on the real conductance component and the imaginary susceptance component of the true state admittance component, and the rated load parameters of the current transformer; determining a dielectric loss index based on the ratio of the imaginary susceptance component to the real conductance component; determining a capacitance change index based on the deviation between the equivalent capacitance corresponding to the imaginary susceptance component and the rated capacitance; and performing online monitoring of the current transformer based on the metering error index, the dielectric loss index, and the capacitance change index.

[0012] In some embodiments, the online monitoring method for the instrument transformer further includes: obtaining the equipment type connected to the secondary side of the instrument transformer by parsing a substation configuration description file, system specification description file, or equipment ledger database; the online monitoring of the instrument transformer based on the metering error index, the dielectric loss index, and the capacitance change index includes: retrieving a sensitivity weight vector corresponding to the equipment type from a preset weight library based on the equipment type connected to the secondary side of the instrument transformer, wherein the sensitivity weight vector includes the weight coefficients of the metering error index and the insulation status index, and different weight coefficient allocation ratios correspond to different equipment types; and weighting and fusing the amplitude index, phase index, dielectric loss index, and capacitance change index in the metering error index according to the sensitivity weight vector to obtain a comprehensive health index for the equipment type, so as to perform online monitoring of the instrument transformer based on the comprehensive health index.

[0013] In some implementations, the different weighting coefficient allocation ratios for different equipment types include: determining the load characteristic classification of the load circuit according to the equipment type, wherein the load characteristic classification includes continuous load, event-type load, and mixed load, wherein the continuous load is characterized by continuous changes in active and reactive power, the event-type load is characterized by abrupt changes in switch state, and the mixed load has both continuous and event-type characteristics; when the load characteristic classification of the load circuit is a continuous load, the weighting coefficient of the metering error index is higher than the weighting coefficient of the insulation status index; when the load characteristic classification of the load circuit is an event-type load, the weighting coefficient of the insulation status index is higher than the weighting coefficient of the metering error index; when the load characteristic classification of the load circuit is a mixed load, a weighting coefficient allocation ratio matching the equipment functional positioning is used.

[0014] This application provides an online monitoring system for a current transformer, including a processor and a memory. The memory stores a computer program, which is executed by the processor to perform the online monitoring method for the current transformer described above.

[0015] The online monitoring method for a current transformer according to this application includes: acquiring electrical acquisition values, environmental parameters, and operating status parameters of the load circuit of the current transformer to form a multi-source time series data stream; acquiring a pre-calibrated admittance decoupling benchmark model, wherein the admittance decoupling benchmark model includes a characteristic admittance benchmark of the current transformer port, a first sensitivity parameter of the influence of environmental factors on the equivalent admittance of the current transformer port, and a second sensitivity parameter of the influence of load factors on the equivalent admittance of the current transformer port; calculating the current equivalent admittance measured value of the current transformer port based on the electrical acquisition values ​​of the current transformer; decomposing the current equivalent admittance measured value into a characteristic admittance benchmark component corresponding to the standard operating condition, an environmental disturbance admittance component caused by the deviation of environmental parameters from the standard operating condition, a load disturbance admittance component caused by the change of the operating status of the load circuit, and a true state admittance component based on the true state admittance component; and calculating the evaluation index of the current transformer based on the true state admittance component to perform online monitoring of the current transformer.

[0016] The implementation method of this application retrieves differentiated admittance decoupling model parameters and state assessment criteria to accurately isolate admittance changes caused by environmental temperature and humidity, load fluctuations, and changes in the working state of secondary equipment. This yields a true admittance component that reflects only the insulation degradation and metering performance changes of the instrument transformer itself, thereby enabling timely and reliable state warnings for specific equipment. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating the online monitoring method for current transformers provided in this application embodiment.

[0019] Figure 2 This is a schematic diagram of the process for retrieving differentiated admittance decoupling model parameters provided in the embodiments of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] This application provides an online monitoring system for instrument transformers, which can accurately decouple environmental temperature and humidity disturbances and load fluctuation disturbances, accurately isolate the admittance changes caused by environmental temperature and humidity and load fluctuations, and obtain the true admittance component that only reflects the insulation degradation and metering performance changes of the instrument transformer itself, thereby achieving reliable status early warning for specific equipment.

[0022] The online monitoring method for current transformers provided by the exemplary embodiments of this application will be described below with reference to the accompanying drawings and the application scenarios described above. It should be noted that the application scenarios described above are only shown for the purpose of understanding the principles of this application, and the embodiments of this application are not limited in any way.

[0023] Figure 1 A flowchart illustrating the online monitoring method for current transformers provided in this application embodiment.

[0024] like Figure 1 As shown, this application provides an online monitoring method for a current transformer, including:

[0025] Step 01: Acquire the electrical acquisition values ​​of the current transformer, environmental parameters, and operating status parameters of the load circuit to form a multi-source time series data stream;

[0026] Step 02: Obtain the pre-calibrated admittance decoupling benchmark model;

[0027] Step 03: Calculate the measured value of the current equivalent admittance at the current transformer port based on the electrical acquisition values ​​of the current transformer;

[0028] Step 04: Based on the admittance decoupling benchmark model, according to the environmental parameters and the operating state parameters of the load circuit, the current equivalent admittance measured value is decomposed into the characteristic admittance benchmark component corresponding to the standard operating condition, the environmental disturbance admittance component caused by the deviation of the environmental parameters from the standard operating condition, the load disturbance admittance component caused by the change of the operating state of the load circuit, and the true state admittance component.

[0029] Step 05: Calculate the evaluation index of the current transformer based on the true state admittance component in order to monitor the current transformer online.

[0030] Specifically, in step 01, relevant data can be synchronously collected according to a unified satellite synchronization clock time reference to form a multi-source time series data stream with time stamp.

[0031] The electrical data acquired by the instrument transformer includes: the instantaneous value of the primary voltage u1(t) and the instantaneous value of the primary current i1(t). For voltage transformers, the primary voltage is obtained through a capacitive voltage divider or an electromagnetic unit output; for current transformers, the primary current is obtained through electromagnetic induction of the iron core coil; the instantaneous values ​​of the secondary voltage u2(t) and the secondary current i2(t) are directly acquired through the secondary measurement circuit.

[0032] Environmental parameters include: ambient temperature T(t), in degrees Celsius (°C); and ambient humidity H(t), in percentage of relative humidity (%RH).

[0033] The operating status parameters of the load circuit include: active power P(t), reactive power Q(t), and switch state sequence S(t), which are obtained through the data interface with the substation monitoring system.

[0034] The sampling interval can be flexibly set according to the working mode of the current transformer and the monitoring requirements. For steady-state monitoring scenarios, it can be set to 10 minutes or 15 minutes, while for scenarios that need to capture transient processes, it can be shortened to 1 minute or less.

[0035] In step 02, the pre-calibrated admittance decoupling reference model serves to provide a reference and a basis for disturbance stripping. The admittance decoupling reference model defines the port equivalent admittance reference value of the transformer under standard operating conditions, as well as the sensitivity parameters of admittance deviation from the reference caused by environmental factors and load factors, respectively.

[0036] In step 03, by using the admittance decoupling reference model, the real-time measured equivalent admittance can be quantitatively decomposed into inherent reference components, environmental disturbance components, load disturbance components, and true state components. This allows external interference to be removed from the measured values, and effective state information that only reflects the insulation degradation or metering drift of the transformer itself can be extracted. This solves the problem of the measurement value deviation caused by environmental temperature and humidity fluctuations and load changes being difficult to distinguish from the actual performance degradation of the equipment. It also avoids normal operating condition disturbances being misjudged as faults or the actual degradation being submerged in interference signals.

[0037] In step 04, the true state admittance component serves as the only signal source reflecting the state of the current transformer itself. It eliminates external interference and only contains information on admittance changes caused by internal factors such as insulation degradation of the current transformer body, winding deformation, or metering drift. By calculating the evaluation index of the current transformer, the actual working state of the current transformer can be accurately determined.

[0038] In some implementations, the admittance decoupling reference model includes a characteristic admittance reference for the transformer port, a first sensitivity parameter for the influence of environmental factors on the equivalent admittance of the transformer port, and a second sensitivity parameter for the influence of load factors on the equivalent admittance of the transformer port.

[0039] Step 02 above includes:

[0040] The characteristic admittance benchmark is defined as the equivalent admittance value of the transformer port under preset standard environmental conditions, when the rated electrical quantity is applied and the load circuit is at a preset typical operating point;

[0041] The first sensitivity parameter is determined based on the deviation of the equivalent admittance of the measuring port from the characteristic admittance reference under different temperature and humidity combinations of the current transformer. The first sensitivity parameter characterizes the degree of influence of temperature change alone, humidity change alone, and temperature and humidity change simultaneously on the equivalent admittance of the port.

[0042] The second sensitivity parameter is determined based on the dynamic correlation between the port equivalent admittance and the load circuit operating state parameters during normal operation of the current transformer. The second sensitivity parameter characterizes the degree of influence of the load circuit's active power, reactive power, and switch state changes on the port equivalent admittance and its dynamic response characteristics.

[0043] Specifically, the admittance decoupling benchmark model Ybase(f) can be defined as: the equivalent admittance frequency response curve measured at the secondary port of the instrument transformer under standard environmental conditions (ambient temperature T0=25℃, ambient humidity H0=50%RH), with rated voltage (or rated current) applied to the primary side, and all secondary-side connected equipment at their respective typical operating points (metering circuit at rated load, protection device in normal monitoring state, measurement and control device in normal acquisition state, etc.). The admittance decoupling benchmark model Ybase(f) is calibrated once by the instrument transformer manufacturer during factory testing, and the parameters are stored in the instrument transformer's electronic tag or model database.

[0044] The complete mathematical model of the admittance decoupling benchmark model adopts a rational fractional form, which can accurately describe the conductance and susceptance characteristics of the secondary circuit at different frequencies:

[0045]

[0046] Where G0 is the DC conductance component, representing the fixed resistive load of the secondary circuit. C0 is the inherent parallel capacitance, including the distributed capacitance of the transformer secondary winding and the capacitance of the connecting cables. A q p is the residue of the q-th resonant pole. q Let Q be the location of the q-th resonant pole. Q is the number of poles, and usually Q=2~5 is sufficient to meet the accuracy requirements from the power frequency to the 2.5kHz frequency band.

[0047] Condition diagnosis is mainly based on the fundamental frequency component f0, and the fundamental frequency reference admittance is abbreviated as:

[0048]

[0049] The first sensitivity parameter is used to quantitatively describe the linear and nonlinear offsets of the equivalent admittance on the secondary side of the transformer at various frequencies when the ambient temperature TT and ambient humidity H deviate from the reference values ​​(T0 and H0).

[0050] This parameter set was calibrated once during the temperature and humidity cycling test at the time of the instrument transformer's delivery. The test was conducted in a controlled temperature and humidity laboratory, with a full combination of operating conditions (a total of 24 test points) at temperatures of -10℃, 0℃, 10℃, 25℃, 40℃, and 60℃ and humidity levels of 30%, 50%, 70%, and 90%. The deviation of the equivalent admittance of the secondary side of the instrument transformer relative to the reference value was measured, and the following coefficient matrix was obtained using the least squares multiple linear regression method:

[0051]

[0052] The admittance increment caused by environmental temperature and humidity disturbances can be expressed as:

[0053]

[0054] Where ΔT = T(t) - 25 represents the deviation between the current ambient temperature and the reference temperature (25℃). ΔH = H(t) - 50 represents the deviation between the current ambient humidity and the reference humidity (50%RH).

[0055] is the linear sensitivity coefficient of temperature to the real part of admittance. is the linear sensitivity coefficient of humidity to the real part of admittance. This is the sensitivity coefficient of the temperature and humidity cross term to the real part of the admittance. is the linear sensitivity coefficient of the imaginary part of the admittance to temperature. is the linear sensitivity coefficient of humidity to the imaginary part of admittance. f is the sensitivity coefficient of the temperature and humidity cross term to the imaginary part of the admittance. k f is the frequency of the kth harmonic, and k=0 corresponds to the fundamental frequency of 50Hz.

[0056] The introduction of cross-term coefficients is to correct the nonlinear coupling effect that occurs when both temperature and humidity deviate from the baseline value. For example, under high temperature and high humidity conditions, the change in dielectric constant of insulating materials is not a simple linear superposition of temperature and humidity effects; cross-terms can effectively compensate for this nonlinearity.

[0057] The second sensitivity parameter is used to quantitatively describe the increase in the equivalent admittance of the secondary side caused by changes in the control parameters of the secondary side connection equipment of the current transformer.

[0058] Caused by power fluctuations in the secondary-side connected equipment, the change process is relatively smooth and can be described by a finite impulse response model:

[0059]

[0060] and Let P and Q be the influence coefficients of active power P and reactive power Q on the admittance at the m-th sampling lag step, respectively, where m = 0, 1, ..., M-1, and M is the sliding window length. A typical window length is M = 24, corresponding to a 6-hour time span with a 15-minute sampling interval, which can cover most daily load fluctuation cycles. The corresponding formula for calculating the first disturbance admittance increment is:

[0061]

[0062] P(t-mΔt) and Q(t-mΔt) are the active power and reactive power values ​​before m sampling periods, respectively, and Δt is the sampling interval.

[0063] The system's impulse response coefficient γ is automatically learned using the ARX model system identification method based on the normal operating data of the first 30 days after the current transformer is put into operation. It is then updated monthly using newly added normal data to adapt to seasonal changes in the secondary load.

[0064] When discrete events such as switch state changes and protection signal shifts occur, the load admittance of the equipment experiences a step-like change at the moment of occurrence, and then decays and recovers according to a certain time constant:

[0065]

[0066] ηkn is the admittance step coefficient caused by the nth switching state change, ζkn is the complex frequency domain parameter corresponding to the decay time constant of the admittance recovery process after the event, and the corresponding formula for calculating the second disturbance admittance increment is:

[0067]

[0068] ΔSn(tevent) is the state change of the nth switch quantity at the event time tevent, with a value of +1 (contact closed / protection started) or -1 (contact open / protection reset), and t-tevent is the time difference between the current time and the event time.

[0069] This parameter set is obtained by analyzing the difference in admittance before and after known switching operation events (such as circuit breaker opening and closing, protection test actions, etc.) recorded in the first 30 days after the transformer is put into operation, and offline fitting is used to obtain the step coefficient and decay time constant. It is then updated every quarter.

[0070] In some embodiments, step 03 above includes:

[0071] A sliding time window with a length of N sampling points and the current time t as the endpoint is selected. The instantaneous value sequence of secondary voltage u2(t-nΔts) and the instantaneous value sequence of secondary current i2(t-nΔts) within the window are subjected to windowed fast Fourier transform (FFT) to extract the complex phasor at the fundamental frequency f0=50Hz.

[0072] The fundamental frequency phasor of the secondary voltage is:

[0073]

[0074] The fundamental frequency phasor of the secondary current is:

[0075]

[0076] w(n) is a window function (such as the Hanning window) used to reduce spectral leakage. Phasors U2 and I2 contain amplitude and phase information:

[0077]

[0078] The measured equivalent admittance of the secondary side of the current transformer at time t and fundamental frequency f0 is defined as follows:

[0079]

[0080] In some implementations, step 04 above includes:

[0081] The environmental disturbance admittance component is determined based on the deviation of the environmental parameters from the calibration reference value and the first sensitivity parameter.

[0082] The load disturbance admittance component is determined based on the operating state parameters of the load circuit and the second sensitivity parameter.

[0083] The true state admittance component is obtained by successively subtracting the characteristic admittance reference component, the environmental disturbance admittance component, and the load disturbance admittance component from the current equivalent admittance measured value.

[0084] Specifically, the measured admittance can be expressed as the algebraic sum of the following four components:

[0085]

[0086] Among them, the characteristic admittance reference component Ybase(f0) can be retrieved from the model library and characterizes the inherent admittance of the secondary side of the transformer under standard conditions and when the secondary equipment is at a typical operating point.

[0087] The increase in environmental disturbance admittance can be expressed as:

[0088]

[0089] In the formula is the linear sensitivity coefficient of temperature to the real part of admittance. is the linear sensitivity coefficient of humidity to the real part of admittance. This is the sensitivity coefficient of the temperature and humidity cross term to the real part of the admittance. is the linear sensitivity coefficient of the imaginary part of the admittance to temperature. is the linear sensitivity coefficient of humidity to the imaginary part of admittance. This is the sensitivity coefficient of the temperature and humidity cross-term to the imaginary part of the admittance. k is set to 0 to represent the fundamental frequency.

[0090] The load disturbance admittance increment is obtained by convolving the active power sequence and the reactive power sequence with the corresponding impulse response coefficients to obtain the first component of the load disturbance admittance:

[0091]

[0092] and Let P(t-mΔt) and Q(t-mΔt) be the influence coefficients of active power P and reactive power Q on admittance at the m-th sampling lag step, respectively, where m = 0, 1, ..., M-1, and M is the sliding window length. P(t-mΔt) and Q(t-mΔt) are the active power and reactive power values ​​before m sampling periods, respectively, and Δt is the sampling interval.

[0093] The second component of the load disturbance admittance is obtained by using the step value of the switching event and the decay recovery function:

[0094]

[0095] η0n is the admittance step coefficient of the nth switching quantity, ΔSn(tevent) is the state change at the event time, and ζ0n is the decay time constant.

[0096] The load disturbance admittance component can be the sum of the first and second components of the above load disturbance admittance components.

[0097] Figure 2 This is a schematic diagram of the process for retrieving differentiated admittance decoupling model parameters provided in the embodiments of this application.

[0098] like Figure 2 As shown, in some embodiments, the online monitoring method for current transformers further includes:

[0099] Step 011: Obtain the equipment type connected to the secondary side of the instrument transformer by parsing the substation configuration description file, system specification description file, or equipment ledger database.

[0100] Step 02 above also includes:

[0101] Step 021: Based on the type of equipment connected to the secondary side of the current transformer, obtain matching parameters from the preset model library to determine the characteristic admittance benchmark, the first sensitivity parameter, and the second sensitivity parameter.

[0102] Specifically, by parsing the SCD (Substation Configuration Description) file, SSD (System Specification Description) file, or equipment ledger database of the substation monitoring system, a list of all equipment types connected to each winding on the secondary side of the tested instrument transformer is automatically obtained, and they are classified into three types according to their electrical load characteristics: continuous load, event load, and mixed load.

[0103] 1 Electricity metering equipment MM, MMXU Continuous High impedance stabilizes the load, resulting in smooth and slow power changes. 2 Relay protection equipment PDIF, PTOC, PDIS Event-based The load is stable under normal conditions, but transient surges occur during faults. 3 Measurement and control device MMXU, GGIO Continuous Medium impedance load, power change is gradual 4 Fault recording device RDRE, RADR Event-based Sensitive to transient processes, broadband sampling 5 Power quality monitoring device MHAI, MFLK Continuous Requirements for transmission characteristics in the harmonic frequency band 6 Automatic transfer switch for backup power ATS Event-based A sudden change in switch state occurs during operation. 7 Automatic voltage control system AVCO Continuous High accuracy of voltage amplitude is required 8 WAMS / PMU Synchronous Phasor Measurement Unit PMU Continuous Extremely high precision is required for amplitude and absolute phase angle. 9 Distributed power grid connection interface device DRCT, DGEN Hybrid It combines continuous power fluctuations and abrupt switching states. 10 Electrified railway traction protection control device TPRO Event-based Impact load, rich in harmonic content

[0104] In some embodiments, step 021 above includes:

[0105] The load characteristics of the load circuit are classified according to the type of equipment. The load characteristics are classified into continuous load, event load and mixed load. Among them, continuous load is characterized by continuous changes in active power and reactive power, event load is characterized by sudden changes in switch state, and mixed load has both continuous and event characteristics.

[0106] When the load characteristics of the load loop are classified as continuous load, the impulse response coefficient sequence of active power and reactive power to the port equivalent admittance is obtained as the parameter set of the second sensitivity parameter.

[0107] When the load characteristics of the load circuit are classified as event-type loads, the set of parameters obtained is the admittance step coefficient and decay time constant caused by the change of switch state as the second sensitivity parameter.

[0108] When the load characteristics of the load circuit are classified as mixed load, the set of parameters is obtained as follows: the impulse response coefficient sequence of active power and reactive power to the equivalent admittance of the port, and the admittance step coefficient and decay time constant caused by the change of switching state.

[0109] Specifically, the continuous load parameter set is applicable to equipment with continuous changes in active power P and reactive power Q, such as those connected to the secondary side including power metering devices, control devices, power quality monitoring devices, AVC systems, and PMU devices. The load admittance changes of this type of equipment are mainly caused by power fluctuations, and the change process is relatively smooth. The parameter set of the second sensitivity parameter can be described as follows:

[0110]

[0111] The explanation of the relevant parameters can be found in the above implementation method, and will not be repeated here.

[0112] Event-based load parameter sets are applicable to equipment with secondary-side connections including relay protection devices, fault recording devices, automatic transfer switches, and railway traction protection control devices, characterized by discrete events such as switch state changes and protection signal shifts. The load admittance of this type of equipment experiences a step-like change at the moment the event occurs, subsequently decaying and recovering according to a certain time constant. The parameter set of the second sensitivity parameter can be described as follows:

[0113]

[0114] The explanation of the relevant parameters can be found in the above implementation method, and will not be repeated here.

[0115] The hybrid load parameter set is suitable for devices with distributed power grid-connected interface devices on the secondary side, which exhibit both continuous power fluctuations and discrete switching events. The parameter set of the second sensitivity parameter for the hybrid load can be expressed as:

[0116]

[0117] In some embodiments, step 03 above includes:

[0118] When the load characteristics of the load loop are classified as continuous load, the load disturbance admittance component is obtained by convolving and summing the active power sequence and reactive power sequence within a preset time window with the corresponding impulse response coefficients.

[0119] When the load characteristics of the load circuit are classified as event-type loads, the load disturbance admittance component is obtained by the step amount of the switch state change event and the recovery function that decays with the event occurrence time.

[0120] When the load characteristics of the load loop are classified as mixed loads, the load disturbance admittance component is obtained by superimposing the convolution summation result corresponding to the continuous load with the step decay result corresponding to the event load.

[0121] Specifically, the load disturbance admittance component corresponding to a continuous load can be expressed as:

[0122]

[0123] The explanation of the relevant parameters can be found in the above implementation method, and will not be repeated here.

[0124] The load disturbance admittance component corresponding to event-driven loads can be expressed as:

[0125]

[0126] The explanation of the relevant parameters can be found in the above implementation method, and will not be repeated here.

[0127] The load disturbance admittance component corresponding to a mixed load can be expressed as:

[0128]

[0129] In some implementations, step 05 above includes:

[0130] Based on the real and imaginary conductance components of the true state admittance component, as well as the rated load parameters of the instrument transformer, the metering error index is determined.

[0131] The dielectric loss index is determined based on the ratio of the imaginary susceptance component to the real conductivity component.

[0132] The capacitance change index is determined based on the deviation between the equivalent capacitance corresponding to the imaginary susceptance component and the rated capacitance.

[0133] The current transformer is monitored online based on measurement error indicators, dielectric loss indicators, and capacitance change indicators.

[0134] Specifically, the measurement error index is used to quantify the accuracy of amplitude and phase of the current transformer during signal transmission.

[0135] The difference compensation value can be expressed as:

[0136]

[0137] The angle difference compensation value can be expressed as:

[0138]

[0139] G f B is the real part of the conductance of the true state admittance component. f The imaginary susceptance component of the real state admittance component, |Zrated| is the rated load impedance amplitude of the secondary winding of the transformer, and 3438′ is the conversion factor between radians and minutes.

[0140] G f|Zrated| is approximately the relative value of the additional voltage drop in the secondary circuit caused by changes in the actual state, corresponding to the turns ratio error; B f |Zrated| is approximately the reactive component of the secondary circuit caused by changes in the actual state, corresponding to the phase angle shift.

[0141] Corrected dielectric loss factor tanδ true Defined as the ratio of the imaginary part to the real part of the true state admittance:

[0142]

[0143] The rate of change of equivalent capacitance ΔCeq (unit: %) is defined as the percentage change in equivalent capacitance relative to the rated capacitance corresponding to the imaginary part of the true admittance.

[0144]

[0145]

[0146] In some embodiments, the online monitoring of the current transformer based on the metering error index, the dielectric loss index, and the capacitance change index includes:

[0147] Based on the capacitance change index and the dielectric loss index, determine the insulation status index;

[0148] According to the type of equipment connected to the secondary side of the current transformer, the sensitivity weight vector corresponding to the equipment type is retrieved from the preset weight library. The sensitivity weight vector includes the weight coefficient of the metering error index and the weight coefficient of the insulation status index. Different equipment types correspond to different weight coefficient allocation ratios.

[0149] According to the sensitivity weight vector, the measurement error index and the insulation status index are weighted and fused to obtain a comprehensive health index for the equipment type, so as to perform online monitoring of the transformer based on the comprehensive health index.

[0150] Specifically, for each type of connected equipment, based on its functional positioning in the power system, its sensitivity to various errors of the instrument transformer, and relevant technical standards and engineering operation experience, a predefined equipment sensitivity weight vector is defined:

[0151]

[0152] The values ​​for each weighted element range from 0 to 1. A higher weight indicates greater sensitivity of the equipment to the deterioration of the corresponding indicator. For example, electricity metering equipment is extremely sensitive to amplitude error (ratio difference) and phase error (angle difference) (both with a weight of 1.0), because ratio and angle differences directly affect the accuracy of electricity billing; however, it is relatively less sensitive to changes in dielectric loss factor and capacitance (weights of 0.2 and 0.3 respectively), because slow insulation degradation has limited impact on metering accuracy before triggering a sudden change in the transformer ratio. Relay protection equipment, on the other hand, has the opposite approach, assigning higher weights (0.9 and 1.0) to insulation indicators (dielectric loss factor and equivalent capacitance change rate), because insulation breakdown can lead to maloperation or failure to operate, causing serious consequences.

[0153] In some implementations, the different weighting coefficient allocation ratios corresponding to different device types include:

[0154] The load characteristics of the load circuit are classified according to the equipment type. The load characteristics classification includes continuous load, event load and mixed load. The continuous load is characterized by continuous changes in active power and reactive power. The event load is characterized by abrupt changes in switching state. The mixed load has both continuous and event characteristics.

[0155] When the load characteristics of the load circuit are classified as continuous load, the weighting coefficient of the metering error index is higher than that of the insulation status index.

[0156] When the load characteristics of the load circuit are classified as event-type loads, the weighting coefficient of the insulation status index is higher than that of the metering error index.

[0157] When the load characteristics of the load circuit are classified as mixed loads, the weighting coefficients are allocated according to the functional positioning of the equipment.

[0158] Specifically, the core function of electricity metering equipment is to accurately measure electricity consumption. It is extremely sensitive to amplitude and phase errors, while the insulation condition has limited impact on metering accuracy as long as it does not cause a sudden change in the transformer ratio. The core function of relay protection equipment is to reliably isolate faults. Insulation breakdown can lead to maloperation or failure to operate, making it extremely sensitive to insulation degradation. Small metering errors under steady-state conditions have little impact on protection decisions. Based on this difference, continuous loads typically correspond to metering equipment, which should be assigned high weight to metering indicators and low weight to insulation indicators. Event-driven loads typically correspond to protection equipment, which should be assigned high weight to insulation indicators and low weight to metering indicators. Mixed loads should be flexibly configured according to the specific functional positioning of the equipment.

[0159] To facilitate better implementation of the online monitoring method for current transformers according to the embodiments of this application, the embodiments of this application provide an online monitoring system for current transformers.

[0160] The online monitoring system for current transformers provided in this application includes a processor and a memory. The memory stores a computer program, which is executed by the processor to perform the online monitoring method for current transformers described above.

[0161] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0162] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0163] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0164] In the embodiments of this application, the terms "module" or "unit" refer to a computer program or part of a computer program that has a predetermined function and works with other related parts to achieve a predetermined goal, and can be implemented wholly or partially using software, hardware (such as processing circuitry or memory), or a combination thereof. Similarly, a processor (or multiple processors or memory) can be used to implement one or more modules or units. Furthermore, each module or unit can be part of an overall module or unit that includes the functionality of that module or unit.

[0165] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0166] In addition, the functional units in the embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0167] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer or a server) to execute all or part of the steps of the methods of the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0168] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An online monitoring method for a current transformer, characterized in that, include: The electrical acquisition values, environmental parameters, and operating status parameters of the load circuit of the current transformer are obtained to form a multi-source time series data stream; Obtain a pre-calibrated admittance decoupling benchmark model, which includes a characteristic admittance benchmark of the transformer port, a first sensitivity parameter of the influence of environmental factors on the equivalent admittance of the transformer port, and a second sensitivity parameter of the influence of load factors on the equivalent admittance of the transformer port. Based on the electrical acquisition values ​​of the current transformer, calculate the measured value of the current equivalent admittance at the current transformer port; The environmental disturbance admittance component is determined based on the deviation between the environmental parameters and the calibration reference value and the first sensitivity parameter. The load disturbance admittance component is determined based on the operating state parameters of the load circuit and the second sensitivity parameter. The true state admittance component is obtained by sequentially subtracting the characteristic admittance reference component, the environmental disturbance admittance component, and the load disturbance admittance component from the current equivalent admittance measured value. Based on the true state admittance component, the evaluation index of the current transformer is calculated to perform online monitoring of the current transformer.

2. The online monitoring method for current transformers according to claim 1, characterized in that, The admittance decoupling benchmark model includes a characteristic admittance benchmark for the transformer port, a first sensitivity parameter for the influence of environmental factors on the equivalent admittance of the transformer port, and a second sensitivity parameter for the influence of load factors on the equivalent admittance of the transformer port. Obtaining the pre-calibrated admittance decoupling benchmark model includes: The characteristic admittance benchmark is defined as the equivalent admittance value of the current transformer port under preset standard environmental conditions, when a rated electrical quantity is applied and the load circuit is at a preset typical operating point; The first sensitivity parameter is determined based on the deviation of the equivalent admittance of the measured port of the current transformer from the characteristic admittance reference under different temperature and humidity combination conditions. The first sensitivity parameter characterizes the degree of influence of temperature change alone, humidity change alone, and temperature and humidity change simultaneously on the equivalent admittance of the port. The second sensitivity parameter is determined based on the dynamic correlation between the port equivalent admittance and the load circuit operating state parameters during normal operation of the current transformer. The second sensitivity parameter characterizes the degree of influence and dynamic response characteristics of the load circuit's active power, reactive power, and switch state changes on the port equivalent admittance.

3. The online monitoring method for current transformers according to claim 1 or 2, characterized in that, The online monitoring method for the current transformer also includes: The equipment type connected to the secondary side of the instrument transformer is obtained by parsing the substation configuration description file, system specification description file, or equipment ledger database. The process of obtaining the pre-calibrated admittance decoupling benchmark model also includes: Based on the type of device connected to the secondary side of the current transformer, matching parameters are obtained from a preset model library to determine the characteristic admittance benchmark, the first sensitivity parameter, and the second sensitivity parameter.

4. The online monitoring method for current transformers according to claim 3, characterized in that, The step of obtaining matching parameters from a preset model library based on the type of equipment connected to the secondary side of the current transformer includes: The load characteristics of the load circuit are classified according to the equipment type. The load characteristics classification includes continuous load, event load and mixed load. The continuous load is characterized by continuous changes in active power and reactive power. The event load is characterized by abrupt changes in switching state. The mixed load has both continuous and event characteristics. When the load characteristics of the load circuit are classified as continuous load, the impulse response coefficient sequence of active power and reactive power to the port equivalent admittance is obtained as the parameter set of the second sensitivity parameter. When the load characteristics of the load circuit are classified as event-type load, the admittance step coefficient and decay time constant caused by the change in switch state are obtained as the parameter set of the second sensitivity parameter. When the load characteristics of the load circuit are classified as a mixed load, the pulse response coefficient sequence of active power and reactive power to the equivalent admittance of the port, as well as the admittance step coefficient and decay time constant caused by the change of switching state, are obtained as the parameter set of the second sensitivity parameter.

5. The online monitoring method for current transformers according to claim 3, characterized in that, The admittance decoupling benchmark model, based on the environmental parameters and the operating state parameters of the load circuit, decomposes the current equivalent measured admittance value into a characteristic admittance benchmark component corresponding to the standard operating condition, an environmental disturbance admittance component caused by the deviation of environmental parameters from the standard operating condition, a load disturbance admittance component caused by changes in the operating state of the load circuit, and a true state admittance component, including: When the load characteristics of the load circuit are classified as continuous load, the load disturbance admittance component is obtained by convolving and summing the active power sequence and reactive power sequence within a preset time window with the corresponding impulse response coefficients. When the load characteristics of the load circuit are classified as event-type loads, the load disturbance admittance component is obtained by the step amount of the switch state change event and the recovery function that decays with the event occurrence time. When the load characteristics of the load loop are classified as a mixed load, the load disturbance admittance component is obtained by superimposing the convolution summation result corresponding to the continuous load with the step decay result corresponding to the event-type load.

6. The online monitoring method for current transformers according to claim 1, characterized in that, The step of calculating the evaluation index of the current transformer based on the true state admittance component for online monitoring of the current transformer includes: Based on the real and imaginary conductance components of the true state admittance component, and the rated load parameters of the current transformer, the metering error index is determined. The dielectric loss index is determined based on the ratio of the imaginary susceptance component to the real conductivity component. The capacitance change index is determined based on the deviation between the equivalent capacitance corresponding to the imaginary susceptance component and the rated capacitance. The current transformer is monitored online based on the metering error index, the dielectric loss index, and the capacitance change index.

7. The online monitoring method for current transformers according to claim 6, characterized in that, The online monitoring method for the current transformer also includes: The equipment type connected to the secondary side of the instrument transformer is obtained by parsing the substation configuration description file, system specification description file, or equipment ledger database. The online monitoring of the current transformer based on the metering error index, the dielectric loss index, and the capacitance change index includes: According to the type of equipment connected to the secondary side of the current transformer, the sensitivity weight vector corresponding to the equipment type is retrieved from the preset weight library. The sensitivity weight vector includes the weight coefficient of the power metering equipment and the weight coefficient of the relay protection equipment. Different equipment types correspond to different weight coefficient allocation ratios. According to the sensitivity weight vector, the amplitude index, phase index, dielectric loss index and capacitance change index in the metering error category are weighted and fused to obtain a comprehensive health index for the equipment type, so as to perform online monitoring of the current transformer based on the comprehensive health index.

8. The online monitoring method for current transformers according to claim 7, characterized in that, The different weighting coefficient allocation ratios corresponding to different equipment types include: Insulation status indicators are determined based on the dielectric loss index and the capacitance change index. The load characteristics of the load circuit are classified according to the equipment type. The load characteristics classification includes continuous load, event load and mixed load. The continuous load is characterized by continuous changes in active power and reactive power. The event load is characterized by abrupt changes in switching state. The mixed load has both continuous and event characteristics. When the load characteristics of the load circuit are classified as continuous load, the weighting coefficient of the metering error index is higher than that of the insulation status index. When the load characteristics of the load circuit are classified as event-type loads, the weighting coefficient of the insulation status index is higher than that of the metering error index. When the load characteristics of the load circuit are classified as mixed loads, the weighting coefficients are allocated according to the functional positioning of the equipment.

9. An online monitoring system for a current transformer, characterized in that, It includes a processor and a memory, the memory storing a computer program, and the processor executing the computer program to implement the online monitoring method for the current transformer as described in any one of claims 1 to 8.

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