Method and system for judging accuracy of harmonic voltage measurement on high-voltage side of main transformer in substation

Abstract

The application discloses a substation main transformer high-voltage side harmonic voltage measurement accuracy discrimination method and system, and the method comprises the following steps: synchronously collecting harmonic voltage phasors of a substation main transformer high-voltage side, medium-voltage side and low-voltage side power supply bus and harmonic current phasors of each outgoing line within the same time; establishing an equivalent impedance model of the main transformer high-voltage side, medium-voltage side and low-voltage side according to main transformer specification parameters; calculating the neutral point harmonic voltage of the main transformer equivalent impedance model; calculating the main transformer medium-voltage side harmonic voltage, comparing the main transformer medium-voltage side harmonic voltage with the actually measured main transformer medium-voltage side harmonic voltage, discriminating the main transformer medium-voltage side harmonic voltage measurement accuracy, calculating the main transformer high-voltage side harmonic voltage, comparing the main transformer high-voltage side harmonic voltage with the actually measured main transformer high-voltage side harmonic voltage, and discriminating the main transformer high-voltage side harmonic voltage measurement accuracy. The application solves the technical problem of discriminating whether the substation main transformer high-voltage side and medium-voltage side exist harmonic voltage measurement distortion.

Description

Technical Field

[0001] This invention relates to the field of harmonic voltage measurement technology, specifically a method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer in a substation. Background Technology

[0002] With the large-scale application of various power electronic devices and nonlinear, impulsive loads, harmonic problems in new power systems are becoming increasingly prominent. Accurate acquisition of harmonic measurement data is a prerequisite for conducting harmonic analysis, assessment, and mitigation. Currently, in power grid substations, electromagnetic current transformers are widely used for current measurement, which produce virtually no measurement distortion for harmonic currents below 1000Hz. The vast majority of 10 / 35kV bus voltage measurements use electromagnetic voltage transformers (PTs), which have high measurement accuracy and can provide accurate voltage measurement data. However, in 110kV and above power systems, the main sensing terminal for voltage measurement is the capacitive voltage transformer (CVT). The equivalent impedance of the stray capacitance of its compensation reactor and the stray capacitance of the primary winding of the intermediate transformer varies with frequency, leading to resonance problems in certain scenarios. This can cause harmonic voltage measurement distortion, easily misleading the implementation of harmonic source tracing and mitigation work. For example, at a power frequency of 50Hz, the voltage divider capacitor and the compensation reactor in the CVT resonate in series. Under non-power frequency conditions, the reactor cannot fully compensate or the undercompensated capacitor voltage divider causes voltage distortion, the resonance state is destroyed, and the transformation ratio of the capacitive voltage transformer will change with the frequency.

[0003] Patent application CN112305484A discloses a method and device for judging the accuracy of harmonic measurement in a capacitive voltage transformer, which mainly identifies the accuracy of harmonic phase measurement in a high-voltage side capacitive voltage transformer. However, it cannot simultaneously identify the accuracy of harmonic amplitude measurement in both high- and medium-voltage side capacitive voltage transformers.

[0004] Patent application CN10365445A discloses a method for high-voltage harmonic measurement using a capacitive voltage transformer. This method primarily modifies the conventional capacitive voltage transformer on the high-voltage side and the electromagnetic unit branch on the low-voltage side, rather than relying on the accuracy assessment of the original measurement data. Furthermore, it cannot simultaneously assess the harmonic measurement accuracy of the original high- and medium-voltage capacitive voltage transformers.

[0005] The invention patent with patent application publication number CN117517825A discloses a real-time monitoring method for the medium-voltage side of a distribution transformer based on digital twin technology. This patent uses the low-voltage side voltage and current and the resistance and inductance of the distribution transformer to calculate the medium-voltage side voltage and current using differentiation and integration methods. However, the monitoring object of this patent is the medium-voltage side voltage and current of the transformer, rather than harmonic voltage. At the same time, it does not identify the accuracy of harmonic measurement.

[0006] Therefore, how to effectively determine the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer by utilizing harmonic current monitoring data and low-voltage side harmonic voltage monitoring data of the main transformer, and combining them with substation system parameters, is a key technical problem that urgently needs to be solved. Summary of the Invention

[0007] The technical problem to be solved by this invention is to propose a method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer in a substation. This method comprehensively utilizes the harmonic current data of each outgoing line of the main transformer, the harmonic voltage data on the low voltage side of the main transformer, and the system electrical parameters to solve the technical problem of simultaneously judging whether there is harmonic voltage measurement distortion on the high and medium voltage sides of the main transformer in a substation.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] A method for determining the accuracy of harmonic voltage measurement on the high- and intermediate-voltage side of a substation main transformer includes:

[0010] Simultaneously collect the harmonic voltage phasors of the high, medium, and low voltage sides of the main transformer in the substation, as well as the harmonic current phasors of each outgoing line, at the same time.

[0011] Based on the specifications of the main transformer, establish equivalent impedance models for the high, medium, and low voltage sides of the main transformer;

[0012] Based on the harmonic voltage phasor and harmonic current phasor on the low-voltage side, calculate the neutral point harmonic voltage of the equivalent impedance model of the main transformer.

[0013] Based on the harmonic current phasor collected from the medium-voltage side and the neutral point harmonic voltage, the harmonic voltage on the medium-voltage side of the main transformer is calculated and compared with the effective voltage value corresponding to the actual measured harmonic voltage phasor on the medium-voltage side to determine the accuracy of the measurement of the harmonic voltage on the medium-voltage side of the main transformer.

[0014] Based on the collected harmonic current phasor on the high-voltage side and the neutral point harmonic voltage, the high-voltage side harmonic voltage of the main transformer is calculated, and then compared with the effective voltage value corresponding to the actual measured high-voltage side harmonic voltage phasor to determine the accuracy of the high-voltage side harmonic voltage measurement of the main transformer.

[0015] Technical Effects: This invention is based on a data-model joint driving method. On the one hand, it fully utilizes harmonic monitoring data, using accurate harmonic current data and low-voltage side harmonic voltage data of the main transformer as data drivers. On the other hand, the mechanism model is simple and clear, using the system topology and grid parameters to construct the equivalent impedance model of the main transformer, which serves as the model driver. Finally, the high- and medium-voltage side harmonic voltages of the main transformer are jointly calculated and compared with the measured high- and medium-voltage side harmonic voltages of the main transformer. This allows for the identification of the accuracy of the high- and medium-voltage side harmonic voltage measurements, verifies the accuracy of the high- and medium-voltage side harmonic data, and effectively improves the accuracy of high- and medium-voltage side harmonic measurements. This provides reliable data support for subsequent harmonic anomaly analysis of the power grid across voltage levels.

[0016] In one embodiment of the present invention, an equivalent impedance model for the high, medium, and low voltage sides of the main transformer is established based on the specifications of the main transformer. This includes: establishing the equivalent impedance model for the high, medium, and low voltage sides of the main transformer based on the rated capacity, capacity percentage, connection method, maximum short-circuit loss, rated voltage on the high voltage side, short-circuit voltage between the high and medium voltage side windings, short-circuit voltage between the medium and low voltage side windings, and short-circuit voltage between the low and high voltage side windings of the main transformer.

[0017] In one embodiment of the present invention, the expressions for the equivalent impedance models of the high, medium, and low voltage sides of the main transformer are as follows:

[0018] ;

[0019] ;

[0020] ;

[0021] in,

[0022] ;

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] ;

[0028] In the formula, , , These represent the equivalent high-voltage side, medium-voltage side, and low-voltage side windings of the main transformer, respectively, on the high-voltage side. Subharmonic impedance; , , These are the equivalent resistances of the high-voltage, medium-voltage, and low-voltage windings of the main transformer, respectively, directed to the high-voltage side. , , These are the reactances of the high-voltage, medium-voltage, and low-voltage windings of the main transformer, respectively, equivalent to the high-voltage side. For harmonic order; The imaginary unit; This refers to the short-circuit voltage between the high-voltage and intermediate-voltage windings. This refers to the short-circuit voltage between the medium and low voltage side windings; This refers to the short-circuit voltage between the low-voltage and high-voltage side windings. This is the rated voltage on the high-voltage side; The rated capacity of the main transformer; The resistance of the main transformer winding at 100% capacity, equivalent to the high-voltage side; The resistance of the main transformer winding at 50% capacity is equivalent to that on the high-voltage side.

[0029] In one embodiment of the present invention, calculating the neutral point harmonic voltage of the equivalent impedance model of the main transformer includes:

[0030] Based on the data collected from the low-voltage side of the main transformer In the model of subharmonic voltage phasors, harmonic current phasors, and the equivalent impedance of the main transformer, the low-voltage winding is equivalent to the high-voltage side. The second harmonic impedance, combined with the main transformer connection method, is used to obtain the neutral point equivalent to the high-voltage side. The subharmonic voltage phasor is used as the neutral point harmonic voltage.

[0031] In one embodiment of the present invention, the expression for the neutral point harmonic voltage of the equivalent impedance model of the main transformer is as follows:

[0032] ;

[0033] In the formula, The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; Main transformer low voltage side Second harmonic voltage phasor; Main transformer low voltage side Second harmonic current phasor; The low-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; The ratio of the high-voltage to low-voltage side transformers; For angle; For harmonic order; It is a natural number.

[0034] In one embodiment of the present invention, determining the accuracy of harmonic voltage measurement on the medium-voltage side of the main transformer includes:

[0035] Calculate the difference between the effective voltage values ​​corresponding to the intermediate-voltage side harmonic voltage of the main transformer and the actual measured intermediate-voltage side harmonic voltage phasors, and use this as the intermediate-voltage side harmonic voltage difference rate. ;

[0036] The harmonic voltage difference on the medium voltage side With medium-pressure side harmonic threshold In comparison, if If the harmonic voltage measurement on the medium-voltage side of the main transformer is accurate, then the measurement is accurate. If this happens, the measurement of harmonic voltage on the medium-voltage side of the main transformer will be inaccurate.

[0037] In one embodiment of the present invention, the harmonic voltage on the medium-voltage side of the main transformer is obtained by the following formula:

[0038] ;

[0039] ;

[0040] In the formula, medium voltage side of main transformer Theoretical values ​​of subharmonic voltage phasors; medium voltage side of main transformer Subharmonic voltage; medium voltage side of main transformer The theoretical value of the real part of the subharmonic voltage phasor; medium voltage side of main transformer The theoretical value of the imaginary part of the subharmonic voltage phasor; The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; medium voltage side of main transformer Second harmonic current phasor; The medium-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; For high-pressure side transformer ratio; For harmonic order; It is the imaginary unit.

[0041] In one embodiment of the present invention, determining the accuracy of harmonic voltage measurement on the high-voltage side of the main transformer includes:

[0042] Calculate the difference between the effective voltage values ​​corresponding to the high-voltage side harmonic voltage of the main transformer and the actual measured high-voltage side harmonic voltage phasors, and use this as the high-voltage side harmonic voltage difference rate. ;

[0043] High-voltage side harmonic voltage difference Harmonic threshold of high voltage side In comparison, if If the high-voltage side harmonic voltage measurement of the main transformer is accurate, then the measurement is accurate. If this happens, the measurement of harmonic voltage on the high-voltage side of the main transformer will be inaccurate.

[0044] In one embodiment of the present invention, the harmonic voltage on the high-voltage side of the main transformer is obtained by the following formula:

[0045] ;

[0046] ;

[0047] In the formula, Main transformer high voltage side Theoretical values ​​of subharmonic voltage phasors; Main transformer high voltage side Subharmonic voltage; Main transformer high voltage side The theoretical value of the real part of the subharmonic voltage phasor; Main transformer high voltage side The theoretical value of the imaginary part of the subharmonic voltage phasor; The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; Main transformer high voltage side Second harmonic current phasor; The high-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; For harmonic order; It is the imaginary unit.

[0048] This invention also provides a system for judging the accuracy of harmonic voltage measurement on the intermediate and high voltage sides of a substation main transformer, which applies the above-described method for judging the accuracy of harmonic voltage measurement on the intermediate and high voltage sides of a substation main transformer, including:

[0049] The data acquisition module is used to synchronously acquire the harmonic voltage phasors of the high, medium and low voltage side power supply busbars of the substation main transformer and the harmonic current phasors of each outgoing line at the same time.

[0050] The impedance modeling module is used to establish equivalent impedance models for the high, medium, and low voltage sides of the main transformer based on the main transformer's specifications.

[0051] The neutral point module is used to calculate the neutral point harmonic voltage based on the harmonic voltage phasor and harmonic current phasor of the low-voltage side.

[0052] The medium-voltage side identification module is used to calculate the harmonic voltage on the medium-voltage side of the main transformer based on the harmonic current phasor collected on the medium-voltage side and the neutral point harmonic voltage, and compare it with the effective voltage value corresponding to the actual measured medium-voltage side harmonic voltage phasor to identify the accuracy of the measurement of the harmonic voltage on the medium-voltage side of the main transformer.

[0053] The high-voltage side identification module is used to calculate the high-voltage side harmonic voltage of the main transformer based on the acquired high-voltage side harmonic current phasor and the neutral point harmonic voltage, and compare it with the effective voltage value corresponding to the actual measured high-voltage side harmonic voltage phasor to identify the accuracy of the high-voltage side harmonic voltage measurement of the main transformer.

[0054] Compared with the prior art, the beneficial effects of the present invention are:

[0055] This invention does not require modification of the harmonic monitoring device. It directly identifies the accuracy of the data measurement of the amplitude and phase of harmonic voltage in the high-voltage power grid based on the harmonic monitoring data provided by the power grid company. This provides further assurance for the reliability of the harmonic voltage data measured by CVT and avoids misjudgment in harmonic source tracing analysis caused by distorted harmonic voltage monitoring data.

[0056] In existing technologies, the accuracy of harmonic voltage measurement can only be determined by measuring only one side. However, this invention can jointly calculate the harmonic voltages on the high and medium voltage sides of the main transformer, thereby determining the accuracy of the high and medium voltage side harmonic voltage measurement of the main transformer. Attached Figure Description

[0057] Figure 1 This is a flowchart illustrating a method for determining the accuracy of harmonic voltage measurement on the high- and medium-voltage side of a substation main transformer, according to an embodiment of the present invention.

[0058] Figure 2 This is a schematic diagram showing the location of harmonic voltage and harmonic current sampling points in an embodiment of the present invention.

[0059] Figure 3 This is a schematic diagram of the equivalent impedance model of the high, medium and low voltage sides of the main transformer in an embodiment of the present invention.

[0060] Figure 4 This is a measurement diagram of the effective values ​​of the fifth harmonic voltage and current of the high-voltage side power supply bus of the substation main transformer, according to an embodiment of the present invention.

[0061] Figure 5 This is a measurement diagram of the effective values ​​of the fifth harmonic voltage and current of the medium-voltage side power supply bus of the main transformer in a substation, according to an embodiment of the present invention.

[0062] Figure 6 This is a measurement diagram of the effective values ​​of the fifth harmonic voltage and current of the low-voltage side power supply bus of the main transformer in a substation, according to an embodiment of the present invention.

[0063] Figure 7This is a block diagram of a substation main transformer high-voltage side harmonic voltage measurement accuracy judgment system according to an embodiment of the present invention. Detailed Implementation

[0064] To facilitate understanding of the technical solution of the present invention by those skilled in the art, the technical solution of the present invention will now be further described in conjunction with the accompanying drawings.

[0065] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0066] Please see Figure 1 As shown in the figure, this embodiment provides a method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer in a substation, including:

[0067] S10 synchronously collects the harmonic voltage phasors of the high, medium, and low voltage sides of the substation main transformer and the harmonic current phasors of each outgoing line within the same time period.

[0068] Please see Figure 2 As shown, in this embodiment, the voltage time-domain discrete signal is simultaneously sampled at voltage measurement points 1, 2, and 3 and current measurement points 1, 2, and 3 within the same time period. , , and current time-domain discrete signal , , The direction of the current is as follows Figure 3 As shown. Among them. The sampled voltage and current waveforms are numbered in the discrete time domain, with 1, 2, and 3 representing the high, medium, and low voltage sides of the main transformer, respectively. It is known that the current measurements on the high, medium, and low voltage sides of the main transformer are accurate; the low voltage side voltage is measured using a PT (potential transformer), and the results are accurate; however, the accuracy of the high and medium voltage side voltages measured using a CVT (conductively coupled transducer) is uncertain. The sampled signals are converted from a time-domain representation to a frequency-domain representation using a Discrete Fourier Transform (DFT), with a window width of 10 cycles. The specific calculation formula is as follows:

[0069] ;

[0070] ;

[0071] ;

[0072] ;

[0073] In the formula, Voltage measurement point Place Second harmonic voltage phasor; Voltage measurement point Place The real part of the second harmonic voltage phasor; Voltage measurement point Place The imaginary part of the subharmonic voltage phasor; For current measuring point Place Second harmonic current phasor; For current measuring point Place The real part of the phasor of the second harmonic current; For current measuring point Place The imaginary part of the phasor of the second harmonic current; For voltage and current measurement points, =1, 2, 3, representing the high, medium, and low voltage sides of the main transformer, respectively; Voltage measurement point Place RMS value of subharmonic voltage; Voltage measurement point Place RMS value of subharmonic current; For harmonic order; This refers to the number of 10 sampling points for a discrete-time signal of a voltage or current waveform. The number of the discrete-time signal, with a value range of . ; The imaginary unit; It is a natural constant.

[0074] In this embodiment, considering the effectiveness of harmonic voltage and current data acquisition, voltage difference thresholds are set respectively. Current difference threshold .Require and Keep the filtered results and ,in for The mean, for The mean, It is recommended to set it to or Equivalent, It is recommended to set it to or Setting a deviation of 5% or 10% is beneficial to the effectiveness of harmonic voltage and current data acquisition. Because the acquired harmonic voltage and current data may contain abnormal data due to changes in the power grid's operating conditions, the recommended deviation is based on engineering experience. Under these settings, the acquired harmonic voltage and current data has a higher validity.

[0075] S20. Based on the specifications of the main transformer, establish the equivalent impedance models for the high, medium, and low voltage sides of the main transformer.

[0076] Please see Figure 3 As shown, in this embodiment, the rated capacity of the main transformer is obtained. Capacity percentage, connection method is YY-Δ, maximum short-circuit loss Rated voltage on the high-voltage side High and medium pressure side transformer ratio High and low voltage side transformer ratio Short-circuit voltage between high and medium voltage side windings Short-circuit voltage between medium and low voltage side windings Short-circuit voltage between low and high voltage side windings Establish equivalent impedance models for the high, medium, and low voltage sides of the main transformer.

[0077] In this embodiment, the capacity percentage is divided into three categories: 100% / 100% / 100%, 100% / 100% / 50%, and 100% / 50% / 100%. The equivalent resistance of the main transformer winding to the high-voltage side corresponding to different capacities is as follows:

[0078] ;

[0079] ;

[0080] In the formula, The resistance of the main transformer winding at 100% capacity, equivalent to the high-voltage side; The resistance of the main transformer winding at 50% capacity is equivalent to that on the high-voltage side.

[0081] In this embodiment, the types of capacity percentages are explained: For example, if the rated capacity of a three-winding transformer is 750MVA and the capacity percentage is 100% / 100% / 100%, then the rated capacities of the high, medium, and low voltage sides of the three-winding transformer are 750MVA, 750MVA, and 750MVA, respectively. For example, if the rated capacity of a three-winding transformer is 500MVA and the capacity percentage is 100% / 100% / 50%, then the rated capacities of the high, medium, and low voltage sides of the three-winding transformer are 500MVA, 500MVA, and 250MVA, respectively.

[0082] In this embodiment, the equivalent resistance of each winding of the main transformer to the high-voltage side is as follows:

[0083] ;

[0084] ;

[0085] ;

[0086] In the formula, The resistance of the high-voltage side winding of the main transformer is equivalent to that on the high-voltage side. The resistance of the medium-voltage winding of the main transformer is equivalent to that on the high-voltage side. The resistance of the low-voltage winding of the main transformer is equivalent to that on the high-voltage side.

[0087] In this embodiment, the reactance of each winding of the main transformer equivalent to the high-voltage side is as follows:

[0088] ;

[0089] ;

[0090] ;

[0091] In the formula, The reactance of the high-voltage side winding of the main transformer is equivalent to that on the high-voltage side. The reactance of the medium-voltage side winding of the main transformer is equivalent to that of the high-voltage side; The reactance of the low-voltage side winding of the main transformer is equivalent to that on the high-voltage side.

[0092] In this embodiment, the formula for calculating the harmonic impedance of each winding of the main transformer equivalent to the high-voltage side, that is, the expression of the equivalent impedance model of the high, medium, and low voltage sides of the main transformer, is as follows:

[0093] ;

[0094] ;

[0095] ;

[0096] In the formula, The high-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; The medium-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; The low-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance.

[0097] S30, based on the harmonic voltage phasor and harmonic current phasor on the low-voltage side, calculate the neutral point harmonic voltage of the equivalent impedance model of the main transformer.

[0098] In one embodiment of the present invention, based on the collected data from the low-voltage side of the main transformer... Subharmonic voltage phasor Current phasor The equivalent value of the low-voltage side winding of the main transformer to the high-voltage side has been obtained. Subharmonic impedance Given a main transformer connection configuration of YY-Δ, calculate the equivalent neutral point on the high-voltage side. Subharmonic voltage The calculation formula is as follows:

[0099] ;

[0100] In the formula, The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; Main transformer low voltage side Second harmonic voltage phasor; Main transformer low voltage side Second harmonic current phasor; The low-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; The ratio of the high-voltage to low-voltage side transformers; The angle is used, and the specific value depends on the connection group. In particular, when the connection group is Yd11, =30°; It is a natural number.

[0101] S40: Based on the collected harmonic current phasor on the medium-voltage side and the neutral point harmonic voltage, calculate the harmonic voltage on the medium-voltage side of the main transformer, and compare it with the effective voltage value corresponding to the actual measured harmonic voltage phasor on the medium-voltage side to determine the accuracy of the measurement of the harmonic voltage on the medium-voltage side of the main transformer.

[0102] In one embodiment of the present invention, based on the collected data from the medium-voltage side of the main transformer... Subharmonic current phasor The obtained neutral point of the main transformer is equivalent to the high-voltage side. Subharmonic voltage The equivalent value of the medium-voltage side winding of the main transformer to the high-voltage side has been obtained. Subharmonic impedance Find the medium-voltage side of the main transformer. Theoretical value of subharmonic voltage phasor The calculation formula is as follows:

[0103] ;

[0104] ;

[0105] In the formula, medium voltage side of main transformer Theoretical values ​​of subharmonic voltage phasors; medium voltage side of main transformer The theoretical value of the effective value of the second harmonic voltage is the same as that of the medium-voltage side of the main transformer. Subharmonic voltage; medium voltage side of main transformer The theoretical value of the real part of the subharmonic voltage phasor; medium voltage side of main transformer The theoretical value of the imaginary part of the subharmonic voltage phasor; The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; medium voltage side of main transformer Second harmonic current phasor; The medium-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; The high-pressure side transformer ratio is used.

[0106] calculate and The formula for the change in the difference is as follows:

[0107] ;

[0108] In the formula, medium voltage side of main transformer The rate of change of the difference between the measured and theoretical values ​​of the effective value of the second harmonic voltage, i.e., the harmonic voltage difference rate on the medium voltage side. For the actual measurement of the medium-voltage side of the main transformer Effective value of subharmonic voltage.

[0109] like If the harmonic voltage measurement on the medium-voltage side of the main transformer is accurate, then the measurement is accurate. If this happens, the measurement of harmonic voltage on the medium-voltage side of the main transformer will be inaccurate. Among these, For the set medium voltage side of the main transformer The threshold for the rate of change of the difference between the measured and theoretical root mean square value of the subharmonic voltage, i.e. the high-voltage side harmonic threshold, is recommended to be 5% or 10%.

[0110] S50 calculates the high-voltage side harmonic voltage of the main transformer based on the collected harmonic current phasor on the high-voltage side and the neutral point harmonic voltage, and compares it with the effective voltage value corresponding to the actual measured high-voltage side harmonic voltage phasor to determine the accuracy of the high-voltage side harmonic voltage measurement of the main transformer.

[0111] In one embodiment of the present invention, based on the collected data from the high-voltage side of the main transformer... Subharmonic current phasor The obtained neutral point of the main transformer is equivalent to the high-voltage side. Subharmonic voltage The equivalent high-voltage side of the main transformer, as obtained from the calculation, is... Subharmonic impedance Find the high-voltage side of the main transformer. Theoretical value of subharmonic voltage phasor The calculation formula is as follows:

[0112] ;

[0113] ;

[0114] In the formula, Main transformer high voltage side Theoretical values ​​of subharmonic voltage phasors; Main transformer high voltage side Theoretical value of the effective value of the second harmonic voltage, i.e., the high-voltage side of the main transformer. Subharmonic voltage; Main transformer high voltage side The theoretical value of the real part of the subharmonic voltage phasor; Main transformer high voltage side The theoretical value of the imaginary part of the subharmonic voltage phasor; The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; Main transformer high voltage side Second harmonic current phasor; The high-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance.

[0115] calculate and The formula for the change in the difference is as follows:

[0116] ;

[0117] In the formula, Main transformer high voltage side The rate of change of the difference between the measured and theoretical values ​​of the effective value of the subharmonic voltage, i.e., the high-voltage side harmonic voltage difference rate; For the actual measurement of the high-voltage side of the main transformer Effective value of subharmonic voltage.

[0118] like If the high-voltage side harmonic voltage measurement of the main transformer is accurate, then the measurement is accurate. If this happens, the measurement of harmonic voltage on the high-voltage side of the main transformer will be inaccurate. Among these, For the set high-voltage side of the main transformer The threshold for the rate of change of the difference between the measured and theoretical root mean square value of the subharmonic voltage, i.e. the high-voltage side harmonic threshold, is recommended to be 5% or 10%.

[0119] In one embodiment of the present invention, it is obvious that the order of steps S40 and S50 can be interchanged.

[0120] To better illustrate the present invention, a specific embodiment is provided below for detailed description:

[0121] A certain 220kV substation Figure 2 As shown, the 5th harmonic voltage phasors of the high, medium, and low voltage sides of the substation main transformer and the 5th harmonic current phasors of each outgoing line were simultaneously collected at voltage measuring points 1, 2, and 3 and current measuring points 1, 2, and 3 at the same time. Let... for , for ,according to and Keep the filtered results and Its effective value diagram is as follows Figure 4 , Figure 5 , Figure 6 As shown.

[0122] Obtain the rated capacity of the main transformer =180MVA, capacity percentage is 100% / 100% / 50%, connection method is YNyn0d11, maximum short-circuit loss =100kW, rated voltage on the high-voltage side =230kV, high-voltage side transformer ratio =230 / 121, High and low voltage side transformer ratio =230 / 10.5, Short-circuit voltage between high and medium voltage side windings =13.78%, Short-circuit voltage between medium and low voltage side windings =7.55%, Short-circuit voltage between low and high voltage side windings =23.80%. Establish equivalent impedance models for the high, medium, and low voltage sides of the main transformer as follows: Figure 3 As shown in Table 1, the equivalent fifth harmonic impedance of each winding on the high, medium, and low voltage sides of the main transformer to the high voltage side is calculated.

[0123] Table 1. Equivalent 5th harmonic impedance of each winding on the high, medium, and low voltage sides of the main substation to the high voltage side.

[0124]

[0125] Calculate the theoretical values ​​of the effective values ​​of the 5th harmonic voltage on the high and medium voltage sides of the main transformer. , The effective values ​​of the 5th harmonic voltage on the high and medium voltage sides of the main transformer were compared with those values. , The rate of change of the difference was calculated, and the results are shown in Table 2.

[0126] Table 2 Comparison of theoretical and measured values ​​of the effective values ​​of the 5th harmonic voltage on the high and medium voltage sides of the main substation.

[0127]

[0128] set up 5%, The effective value is 5%. Therefore, the theoretical value of the 5th harmonic voltage on the high-voltage side of the main transformer is... With measured value rate of change of difference If the high-voltage side harmonic voltage measurement of the main transformer is accurate, then the theoretical effective value of the 5th harmonic voltage on the medium-voltage side of the main transformer is accurate. With measured value rate of change of difference If the harmonic voltage measurement on the medium-voltage side of the main transformer is accurate, then the measurement will be accurate.

[0129] Please see Figures 1 to 7 As shown, in another embodiment of the present invention, a substation main transformer high-medium voltage side harmonic voltage measurement accuracy discrimination system is also provided, which applies the above-described substation main transformer high-medium voltage side harmonic voltage measurement accuracy discrimination method, including:

[0130] The data acquisition module is used to synchronously acquire the harmonic voltage phasors of the high, medium and low voltage sides of the substation main transformer and the harmonic current phasors of each outgoing line within the same time period.

[0131] The impedance modeling module is used to establish equivalent impedance models for the high, medium, and low voltage sides of the main transformer based on the main transformer's specifications.

[0132] The neutral point module is used to calculate the neutral point harmonic voltage based on the harmonic voltage phasors and harmonic current phasors of the low-voltage side in the equivalent impedance model of the main transformer.

[0133] The medium-voltage side identification module is used to calculate the harmonic voltage on the medium-voltage side of the main transformer based on the collected harmonic current phasor on the medium-voltage side and the neutral point harmonic voltage, and compare it with the effective voltage value corresponding to the actual measured medium-voltage side harmonic voltage phasor to identify the accuracy of the measurement of the harmonic voltage on the medium-voltage side of the main transformer.

[0134] The high-voltage side identification module is used to calculate the high-voltage side harmonic voltage of the main transformer based on the acquired high-voltage side harmonic current phasor and the neutral point harmonic voltage, and compare it with the effective voltage value corresponding to the actual measured high-voltage side harmonic voltage phasor to identify the accuracy of the high-voltage side harmonic voltage measurement of the main transformer.

[0135] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention, and no reference numerals in the claims should be construed as limiting the scope of the claims.

[0136] The above embodiments are merely examples of implementation methods of the invention. The scope of protection of the present invention is not limited to the above embodiments. For those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of a substation main transformer, characterized in that, include: Simultaneously collect the harmonic voltage phasors of the high, medium, and low voltage sides of the main transformer in the substation, as well as the harmonic current phasors of each outgoing line, at the same time. Based on the specifications of the main transformer, equivalent impedance models for the high, medium, and low voltage sides are established. This includes establishing the equivalent impedance models for the high, medium, and low voltage sides of the main transformer based on its rated capacity, capacity percentage, connection method, maximum short-circuit loss, rated voltage on the high-voltage side, short-circuit voltage between the high and medium voltage windings, short-circuit voltage between the medium and low voltage windings, and short-circuit voltage between the low and high voltage windings. The expressions for these models are as follows: ； ； ； in, ； ； ； ； ； ； In the formula, , , These represent the equivalent high-voltage side, medium-voltage side, and low-voltage side windings of the main transformer, respectively, on the high-voltage side. Subharmonic impedance; , , These are the equivalent resistances of the high-voltage, medium-voltage, and low-voltage windings of the main transformer, respectively, directed to the high-voltage side. , , These are the reactances of the high-voltage, medium-voltage, and low-voltage windings of the main transformer, respectively, equivalent to the high-voltage side. For harmonic order; The imaginary unit; This refers to the short-circuit voltage between the high-voltage and intermediate-voltage windings. This refers to the short-circuit voltage between the medium and low voltage side windings; This refers to the short-circuit voltage between the low-voltage and high-voltage side windings. This is the rated voltage on the high-voltage side; The rated capacity of the main transformer; The resistance of the main transformer winding at 100% capacity, equivalent to the high-voltage side; The equivalent resistance of the main transformer windings at 50% capacity to the high-voltage side; Based on the harmonic voltage phasor and harmonic current phasor on the low-voltage side, calculate the neutral point harmonic voltage of the equivalent impedance model of the main transformer. Based on the harmonic current phasor collected from the medium-voltage side and the neutral point harmonic voltage, the harmonic voltage on the medium-voltage side of the main transformer is calculated and compared with the effective voltage value corresponding to the actual measured harmonic voltage phasor on the medium-voltage side to determine the accuracy of the measurement of the harmonic voltage on the medium-voltage side of the main transformer. Based on the collected harmonic current phasor on the high-voltage side and the neutral point harmonic voltage, the high-voltage side harmonic voltage of the main transformer is calculated, and then compared with the effective voltage value corresponding to the actual measured high-voltage side harmonic voltage phasor to determine the accuracy of the high-voltage side harmonic voltage measurement of the main transformer.

2. The method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer in a substation according to claim 1, characterized in that, Calculate the neutral point harmonic voltage of the equivalent impedance model of the main transformer, including: Based on the data collected from the low-voltage side of the main transformer In the model of subharmonic voltage phasors, harmonic current phasors, and the equivalent impedance of the main transformer, the low-voltage winding is equivalent to the high-voltage side. The second harmonic impedance, combined with the main transformer connection method, is used to obtain the neutral point equivalent to the high-voltage side. The subharmonic voltage phasor is used as the neutral point harmonic voltage.

3. The method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer in a substation according to claim 2, characterized in that, The expression for the neutral point harmonic voltage in the equivalent impedance model of the main transformer is: ； In the formula, The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; Main transformer low voltage side Second harmonic voltage phasor; Main transformer low voltage side Second harmonic current phasor; The low-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; The ratio of the high-voltage to low-voltage side transformers; For angle; For harmonic order; It is a natural number.

4. The method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer in a substation according to claim 1, characterized in that, Determining the accuracy of harmonic voltage measurements on the medium-voltage side of the main transformer includes: Calculate the difference between the effective voltage values ​​corresponding to the intermediate-voltage side harmonic voltage of the main transformer and the actual measured intermediate-voltage side harmonic voltage phasors, and use this as the intermediate-voltage side harmonic voltage difference rate. ; The harmonic voltage difference on the medium voltage side With medium-pressure side harmonic threshold In comparison, if If the harmonic voltage measurement on the medium-voltage side of the main transformer is accurate, then the measurement is accurate. If this happens, the measurement of harmonic voltage on the medium-voltage side of the main transformer will be inaccurate.

5. The method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer in a substation according to claim 1, characterized in that, The harmonic voltage on the medium-voltage side of the main transformer is obtained using the following formula: ； ； In the formula, medium voltage side of main transformer Theoretical values ​​of subharmonic voltage phasors; medium voltage side of main transformer Subharmonic voltage; medium voltage side of main transformer The theoretical value of the real part of the subharmonic voltage phasor; medium voltage side of main transformer The theoretical value of the imaginary part of the subharmonic voltage phasor; The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; medium voltage side of main transformer Second harmonic current phasor; The medium-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; For high-pressure side transformer ratio; For harmonic order; It is the imaginary unit.

6. The method for judging the accuracy of harmonic voltage measurement on the high and medium voltage side of the main transformer in a substation according to claim 1, characterized in that, Determining the accuracy of harmonic voltage measurements on the high-voltage side of the main transformer includes: Calculate the difference between the effective voltage values ​​corresponding to the high-voltage side harmonic voltage of the main transformer and the actual measured high-voltage side harmonic voltage phasors, and use this as the high-voltage side harmonic voltage difference rate. ; High-voltage side harmonic voltage difference Harmonic threshold of high voltage side In comparison, if If the high-voltage side harmonic voltage measurement of the main transformer is accurate, then the measurement is accurate. If this happens, the measurement of harmonic voltage on the high-voltage side of the main transformer will be inaccurate.

7. The method for judging the accuracy of harmonic voltage measurement on the high and medium voltage sides of the main transformer in a substation according to claim 1, characterized in that, The harmonic voltage on the high-voltage side of the main transformer is obtained using the following formula: ； ； In the formula, Main transformer high voltage side Theoretical values ​​of subharmonic voltage phasors; Main transformer high voltage side Subharmonic voltage; Main transformer high voltage side The theoretical value of the real part of the subharmonic voltage phasor; Main transformer high voltage side The theoretical value of the imaginary part of the subharmonic voltage phasor; The neutral point of the main transformer is equivalent to the high-voltage side. Second harmonic voltage phasor; Main transformer high voltage side Second harmonic current phasor; The high-voltage side winding of the main transformer is equivalent to the high-voltage side. Subharmonic impedance; For harmonic order; It is the imaginary unit.

8. A system for judging the accuracy of harmonic voltage measurement on the intermediate and high voltage sides of a substation main transformer, characterized in that, The method for determining the accuracy of harmonic voltage measurement on the high- and intermediate-voltage side of the main transformer in a substation, as described in any one of claims 1-7, includes: The data acquisition module is used to synchronously acquire the harmonic voltage phasors of the high, medium and low voltage side power supply busbars of the substation main transformer and the harmonic current phasors of each outgoing line at the same time. The impedance modeling module is used to establish equivalent impedance models for the high, medium, and low voltage sides of the main transformer based on the main transformer's specifications. The neutral point module is used to calculate the neutral point harmonic voltage based on the harmonic voltage phasor and harmonic current phasor of the low-voltage side. The medium-voltage side identification module is used to calculate the harmonic voltage on the medium-voltage side of the main transformer based on the harmonic current phasor collected on the medium-voltage side and the neutral point harmonic voltage, and compare it with the effective voltage value corresponding to the actual measured medium-voltage side harmonic voltage phasor to identify the accuracy of the measurement of the harmonic voltage on the medium-voltage side of the main transformer. The high-voltage side identification module is used to calculate the high-voltage side harmonic voltage of the main transformer based on the acquired high-voltage side harmonic current phasor and the neutral point harmonic voltage, and compare it with the effective voltage value corresponding to the actual measured high-voltage side harmonic voltage phasor to identify the accuracy of the high-voltage side harmonic voltage measurement of the main transformer.

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