79 results about "Short circuit impedance" patented technology

The invention discloses a capacity detection method and system for an electric furnace transformer, electronic equipment and a storage medium, and the method comprises the steps: comparing a short-circuit impedance obtained through conversion of a test result with a standard short-circuit impedance corresponding to a preset capacity, and determining a first evaluation capacity of the electric furnace transformer if the deviation between the two is within a preset range; moreover, the dynamic temperature rise characteristic of the electric furnace transformer under the periodic load is considered, a multi-physical field coupling temperature rise model is constructed, and the second evaluation capacity of the electric furnace transformer can be dynamically determined according to the load characteristic, the environment temperature, the heat dissipation condition and the like in the actual operation of the electric furnace transformer. And finally, the final capacity of the electric furnace transformer is determined by integrating the two capacity evaluation results and the operation condition of the electric furnace transformer, the capacity of the electric furnace transformer can be accurately measured under different operation conditions, the accuracy of capacity detection of the electric furnace transformer is greatly improved, large test equipment and long-time measurement are not needed, and the cost is reduced.

The invention discloses a method for calculating equivalent circuit parameters of a double-current-system multi-winding traction transformer, which comprises the following steps of: constructing a full-size equal-scale model of the double-current-system multi-winding traction transformer, and establishing a finite element calculation model; according to the finite element calculation model, inductance matrixes formed among the I-type winding, the II-type winding and the III-type winding under the two power supply modes of 25kV / 50Hz and 15kV / 16.7 Hz are calculated respectively; based on the formed inductance matrix, establishing a transformer multi-winding equivalent model, and considering circulating current influence caused by internal parallel connection of the I-type winding to obtain actual current sequences of the windings under short-circuit tests between the I-type winding and the III-type winding, between the I-type winding and the II-type winding and between the II-type winding and the III-type winding; according to the obtained actual current sequence of each winding, the short-circuit impedance between the I-type winding and the III-type winding, the short-circuit impedance between the I-type winding and the II-type winding and the short-circuit impedance between the II-type winding and the III-type winding are calculated through an energy method; and obtaining equivalent circuit parameters of the transformer according to the obtained short-circuit impedance value.

The invention provides a ship direct current distribution board fuse setting method considering on-off arcing. Establishing a fuse breaking arcing model: describing a fuse arcing process based on a Cassie arc model, fitting test data through a genetic algorithm to establish a model parameter change rule, and establishing a relationship between a test loop resistance value and an arc voltage constant and an arc time constant through a BP neural network; the method comprises the following steps: calculating equivalent short-circuit impedance of a fault branch, and calculating a test loop impedance parameter which can be equivalent to a system short-circuit fault current waveform according to a short-circuit current peak proportional relation of a system and a test loop; and executing constraint driving type fuse setting: taking the condition that the rated current of the fuse is not less than the product of a safety margin coefficient and the maximum continuous working current of the branch and the total Joule integral value of the non-fault branch does not exceed 50% of the pre-arc Joule integral value as constraint conditions, and adopting a minimum pre-arc Joule integral value priority strategy, iteratively selecting the model from the minimum-scale branch group and expanding to a whole-system branch.

The present invention discloses an online monitoring system and method for transformer winding deformation, which relates to the technical field of transformers, including a current sensor and a voltage sensor, which are respectively used to sample the three-phase current and voltage waveforms of the transformer, and send the collected data to a data processing device for further processing; the data processing device is used to control the sensor to perform sampling operations, and analyze and process the sampling results, calculate the short-circuit impedance, determine whether the winding is deformed, and give the degree of deformation; the data processing device provides a network interface to the outside, and sends the winding deformation monitoring results to a server; the client is used to connect to the server to display the real-time monitoring results of the winding deformation and the winding deformation alarm information. The present invention can perform long-term online monitoring of transformer winding deformation, discover transformer winding deformation problems early, deal with them as soon as possible, and improve the stability and safety of transformer operation.

The high-impedance autotransformer comprises an iron core, a series winding, a common winding I and a common winding II, the common winding I and the common winding II are distributed in the axial direction of the iron core and located on different sections of the iron core, and the series winding, the common winding I and the common winding II are sequentially connected to the iron core in a sleeved mode. The coil supporting block is arranged between the windings and is fastened with the iron core; the supporting cushion blocks are arranged on winding end faces at the two ends of the transformer, and the coil supporting blocks and the supporting cushion blocks are made of insulating materials. The self-coupling transformer solves the technical problems that the self-coupling transformer in the prior art is low in short-circuit impedance and easy to damage during short-circuit impact.

The invention discloses a method for measuring and calculating parameters of a same-tower double-circuit alternating-current transmission line under high induced voltage. The method comprises the following steps: dividing the same-tower double-circuit transmission line into three groups of wiring modes; measuring the short-circuit impedance in each wiring mode and the line impedance in a mode that the tail end of the line is grounded through impedance; calculating the characteristic impedance and the propagation coefficient in the corresponding wiring mode by using the impedance measurement result of the line through impedance grounding and the line short-circuit impedance measurement result in each wiring mode, and further calculating the distribution impedance and the distribution admittance in the corresponding mode; and finally, calculating the resistance, inductance and ground capacitance of each phase lead of the same-tower double-circuit line, the inter-phase coupling capacitance and inter-phase coupling inductance of the single-circuit line, and the coupling capacitance and coupling inductance between each phase lead of the double-circuit line through the distributed impedance and distributed admittance in each wiring mode and simultaneous equations. Through the method, the induced voltage on the measured circuit can be effectively reduced, and meanwhile accurate measurement can be achieved.

The invention relates to the technical field of electrical equipment testing, and discloses a high-precision anti-interference intelligent transformer short-circuit impedance testing machine which comprises an isolation power supply module and a testing host module, an electrostatic shielding layer is arranged in the isolation power supply module, a suspension working power supply isolated from power grid noise is provided for a testing host, and the anti-interference capability is improved from the source. The test host module integrates a power management and inversion module to generate a controllable three-phase AC excitation signal, and the central processing and control module performs closed-loop feedback control on a test current according to a high-precision synchronously acquired signal, so that an external voltage regulator is replaced, and automatic stabilization of a test condition is realized. According to the invention, tedious manual adjustment is not needed, full automation of the testing process is realized, and the precision, repeatability and safety of short-circuit impedance testing are remarkably improved.

The invention discloses a short circuit parameter measurement and analysis method, system, equipment and medium, and relates to the technical field of power system detection, and the method comprises the steps: carrying out the synchronous sampling of a voltage signal and a current signal in a detected line, carrying out the conditioning and conversion of an obtained sampling signal, and generating an original digital quantity; calibrating the original digital quantity to obtain calibrated effective measurement data; short-circuit parameters are calculated based on the effective measurement data, the short-circuit parameters comprise short-circuit current, short-circuit impedance and short-circuit power, and the calculation process comprises fundamental wave extraction and phasor analysis; visually displaying the calculated short-circuit parameters, and generating report data containing a measurement result according to user operation; and in the measurement process, the running state is dynamically adjusted according to the current task type and the energy consumption state. According to the invention, the authenticity of measured data is improved through synchronous sampling and conditioning conversion of voltage and current signals in combination with a multi-dimensional calibration strategy.

The invention provides a reactive voltage partitioning method considering transient voltage safety and network topology characteristics, belongs to the technical field of reactive voltage partitioning of a power grid, and aims to solve the problems that in a traditional reactive voltage partitioning method of the power grid, enough reactive margin cannot be ensured in each region, and some nodes are unreasonably partitioned. Comprising the following steps: calculating a transient voltage characteristic distance and a short-circuit impedance distance between a generator node and a load node; constructing a first initial partition according to the transient voltage characteristic distance of the motor node and the load node, and constructing a second initial partition according to the short-circuit impedance distance of the motor node and the load node; traversing the first initial partition and the second initial partition, constructing a region set according to the common region group, and performing hierarchical clustering iteration combination to obtain a combined sequence; and screening the combined sequence according to modularity index screening, and taking a region set with the maximum modularity in the combined sequence as a final partition.

The embodiment of the invention discloses a distribution transformer operation gear synchronization vector online detection method and device, and the method comprises the steps: obtaining a nameplate parameter of a distribution transformer, and carrying out the calculation to obtain a short-circuit impedance value of a low-voltage side to a high-voltage side under each gear; synchronously measuring a voltage vector of the low-voltage side of the distribution transformer, an output current vector and a neutral point voltage vector; when the amplitude of the low-voltage-side zero-sequence current reaches a current detection threshold value or the module value of the low-voltage-side neutral point voltage vector reaches a voltage detection threshold value, obtaining a detection loop and combining a circuit principle and a low-voltage-side synchronous voltage vector, a synchronous current vector output by the low-voltage side and a low-voltage-side neutral point synchronous voltage vector of the distribution transformer; calculating to obtain a short-circuit impedance value of the low-voltage side to the high-voltage side; calculating to obtain the absolute value of the impedance difference value of each gear; determining the gear corresponding to the minimum absolute value of the impedance difference value of each gear as the current operation gear of the distribution transformer; the operation gear of the transformer can be accurately detected on the low-voltage side in the operation state.

The invention discloses a method for introducing a power bus short-circuit fault equivalent model for a manufacturing enterprise and belongs to the field of power supply and distribution systems. Comprises: setting an enterprise typical introduction power supply system; screening system short-circuit current equivalent branches; the enterprise introduces power supply short-circuit impedance equivalent processing; equivalently processing a tie line between the first and second lead-in power buses of the enterprise; modeling by using professional short-circuit current calculation software; the method comprises the following steps: opening a connecting line between two sections of lead-in power supply buses, modeling by taking a first lead-in power supply bus and a second lead-in power supply bus of an enterprise as two independent power supply systems, constructing an equivalent model of a short-circuit fault of the lead-in power supply buses of the enterprise through an impedance equivalent processing method of the connecting line of the lead-in power supply buses, and carrying out short-circuit fault simulation modeling. The method for establishing the equivalent model of the tie line between the two introduced power buses of the internal power grid of the enterprise is provided by performing equivalent processing on the impedance of the introduced power buses, especially the tie line, so that the correctness of short-circuit current calculation of the enterprise can be improved. The method is suitable for the field of enterprise internal power grid simulation modeling.

The invention discloses a high-density myoelectricity acquisition function test system and method, and relates to the field of test tools.The system comprises an analog multiplexer, a signal test module, a short circuit test module and an impedance test module; each channel of the analog multiplexer corresponds to each channel of the signal acquisition module or the impedance acquisition module; the signal test module is used for performing signal test on the signal acquisition module and judging whether the acquisition function of each channel of the signal acquisition module is normal or not; the short-circuit test module is used for realizing short-circuit test between adjacent channels of the signal acquisition module and judging whether the adjacent channels of the signal acquisition module are short-circuited or not; the impedance test module performs function test on the impedance acquisition module and judges whether the acquisition function of each channel of the impedance acquisition module is normal. The function test efficiency of the signal acquisition module and the impedance acquisition module is improved.

The invention relates to the technical field of power distribution monitoring, and discloses an electrical equipment operation monitoring system based on intelligent control, and the system comprises a grid structure recognition unit which collects a switch contact signal, and determines a real-time power grid topology model; the short-circuit capacity evaluation unit reconstructs a node admittance matrix by using a real-time power grid topology model, and calculates node equivalent short-circuit impedance; the transient feature extraction unit samples a node transient current signal and extracts a high-frequency transient component sequence; a monitoring fixed value follow-up setting unit determines a mapping relation between node equivalent short-circuit impedance and short-circuit capacity, and a monitoring threshold value is corrected in a follow-up mode; according to the system and the method, a physical coupling mechanism of the monitoring constant value and the power grid rigidity is established, sensitivity mismatch caused by grid structure reconstruction is eliminated, and the sensing capacity of the system to the initial degradation of equipment is enhanced. The transient integral energy of the high-frequency transient component sequence is calculated, and an abnormal operation signal is generated when the transient integral energy deviates from a monitoring threshold value.

The invention relates to the technical field of angular-difference closed-loop power regulation of a 10kV power distribution network of a power system, in particular to a power distribution network angular-difference closed-loop power regulation setting and risk checking method and system, and provides an accurate, simple and convenient short-circuit impedance calculation method through which closed-loop current during angular-difference closed-loop can be simply and quickly calculated, so that the power distribution network angular-difference closed-loop power regulation setting and risk checking is realized. Meanwhile, a simple and convenient loop opening point setting calculation principle is provided, after loop closing current is calculated, a proper temporary protection constant value is set at a loop opening point, manual loop closing and protection loop opening are achieved, and the field constant value is rapidly, accurately and simply changed.

The present application discloses a short-circuit impedance adjustment device and method for an MMC converter transformer. The short-circuit impedance adjustment device includes a short-circuit impedance adjustment circuit electrically connected to the secondary winding of the converter transformer. The short-circuit impedance adjustment circuit is a three-phase short-circuit impedance adjustment sub-circuit, and the short-circuit impedance adjustment sub-circuit includes a first bidirectional IGBT component, a second bidirectional IGBT component, a third bidirectional IGBT component, a first adjustment inductor, and a second adjustment inductor. According to different operating states of the MCC, the conduction states of the three IGBT components are controlled. When the MMC is operating normally, the short-circuit impedance is adjusted to a smaller value, so that the system reduces the consumption of reactive power and at the same time meets the control response requirements. When a short-circuit fault occurs on the DC side of the MMC, it instantaneously switches to the large-impedance mode of operation to limit the rise of the short-circuit current. According to different operating modes, the inductance value input is flexibly switched, improving the stability of the system.

This application discloses a method and apparatus for optimizing the short-circuit impedance of converter transformers. The method includes: establishing the relationship between the cost of each transformer and its short-circuit impedance, the relationship between the loss discount of each transformer and its short-circuit impedance, and the relationship between the reactive power consumption of the converter valve and its short-circuit impedance; further determining the relationship between the number of reactive power compensation devices and the short-circuit impedance of the transformers, thereby determining the relationship between the cost of the reactive power compensation devices and the short-circuit impedance of the transformers; integrating these relationships to obtain a comprehensive cost function of the system cost with respect to the transformer short-circuit impedance; and determining the target short-circuit impedance value. It is evident that the comprehensive cost function considers the cost of the transformers, the loss discount, and the reactive power compensation devices. Therefore, in the design process of equipment in a high-voltage direct current transmission system, not only the cost of the transformers, but also the cost of losses and reactive power consumption are considered, and the determined target short-circuit impedance value is the most economical design value.

The invention relates to a DC bus short-circuit current level calculation method, device and equipment of a multi-terminal flexible DC back-to-back system. The method comprises the following steps: acquiring system data, electrical quantity data and parameter data; valve side system short-circuit impedance, first valve side short-circuit impedance and first impedance data are obtained through calculation according to the system data, the parameter data and the electrical quantity data; obtaining a first manufacturing deviation and a second manufacturing deviation, and updating the first valve side short-circuit impedance according to the first manufacturing deviation to obtain a second valve side short-circuit impedance; updating the first impedance data according to the second manufacturing deviation to obtain second impedance data; calculating according to the system data, the parameter data, the valve side system short-circuit impedance, the second valve side short-circuit impedance and the second impedance data to obtain an AC short-circuit current component; calculating a discharge current according to the endurance capacity type and the electrical quantity data; calculating short-circuit current according to the discharge current and the alternating-current short-circuit current component; and calculating the short-circuit current level according to the short-circuit current.

The present invention provides a fuse setting method for a ship's DC distribution board that takes arcing into account. A fuse breaking arcing model is established: the fuse arcing process is described based on the Cassie arc model. The model parameter variation pattern is established by fitting test data using a genetic algorithm. A BP neural network is used to construct the relationship between the test loop resistance value and the arc voltage constant and arc time constant. The equivalent short-circuit impedance of the fault branch is calculated, and based on the proportional relationship between the short-circuit current peaks of the system and the test loop, the test loop impedance parameters that can be equivalent to the system short-circuit fault current waveform are calculated. Constraint-driven fuse setting is performed: with the constraints that the fuse rated current is not less than the product of the safety margin factor and the branch's maximum continuous operating current, and that the total joule integral value of the non-fault branch does not exceed 50% of its pre-arcing joule integral value, a minimum pre-arcing joule integral value priority strategy is adopted. Iterative selection begins with the smallest branch group and expands to all system branches.

The invention relates to the technical field of transformer equipment, and discloses a transformer short-circuit impedance configuration method, a transformer short-circuit impedance configuration system, transformer short-circuit impedance configuration equipment, a medium and a product. Determining a standard value of the short-circuit impedance of each voltage tap of the to-be-selected transformer by combining the short-circuit impedance value of each voltage tap of the in-operation transformer according to the parallel topological relation between the to-be-selected transformer and the at least one in-operation transformer; therefore, the short-circuit impedance value of each voltage tap of the in-operation transformer is utilized to accurately match the short-circuit impedance of each voltage tap of the to-be-selected transformer, the accuracy of the short-circuit impedance of the new transformer is improved, the synchronous full load of the parallel transformers is ensured, and the capacity waste or overload risk is avoided.

The present invention discloses a method for indirectly measuring system impedance based on a low voltage fault generating device, wherein a low voltage fault generating device is used to perform a no-load test, and the no-load test data is used to list the system impedance Z. sx The resistance R sx and inductor X sx Solve the quadratic equations with two unknown variables to get the resistance R sx and inductor X sx value, and finally obtain the system impedance Z sx ; In view of the fact that there is a certain deviation between the measured value and the true value, in order to improve the accuracy of the system impedance, multiple no-load tests are carried out for different test conditions, and the equation groups are listed in pairs to solve the system impedance under each test condition. The system impedance is averaged to obtain a more accurate system impedance value. Based on the system impedance value, the low-voltage fault generating device can efficiently and accurately select the current limiting impedance and short-circuit impedance, accurately control the voltage drop amplitude and phase jump, and reduce the damage of high voltage to the wind turbine and converter.

The present invention discloses a distributed wireless control system and method for transformer winding deformation detection, including a plurality of transformers, a first deformation detection device and a second deformation detection device electrically connected to the windings of the transformers, an edge computing server, and a cloud platform; the first deformation detection device is used to generate a first fault signal when detecting a winding deformation fault; the edge computing server is used to analyze and obtain a first fault credibility level according to the type of the faulty winding and the change amount of the short-circuit impedance; the cloud platform is used to obtain a second fault credibility according to the historical data of the transformer winding, and also determine a secondary fault judgment strategy according to the first fault credibility level and the second fault credibility. The present invention sets two different types of winding deformation detection devices to work together, and executes a secondary judgment strategy based on the judgment of the fault credibility level and the fault credibility, reducing the problem of false alarms of deformation faults in actual work and improving the accuracy and reliability of deformation fault detection.

The invention discloses a method for measuring parameters of a same-tower parallel double-circuit direct-current transmission line in a high induced voltage environment, and the method comprises the steps: enabling the head ends of four polar leads to adopt a plurality of parallel combination modes, measuring series impedance when the tail ends of the four polar lines are grounded through impedance and short-circuit impedance when the tail ends are directly grounded under different parallel combination conditions under a certain non-power frequency; according to the line length, the series impedance when the tail ends of the four pole wires are grounded through impedance and the short-circuit impedance when the tail ends are directly grounded under different parallel combination conditions, characteristic impedance and propagation coefficients under different parallel combination conditions are calculated respectively, and then equivalent distribution impedance and equivalent distribution admittance are calculated; and according to the equivalent distribution impedance and the equivalent distribution admittance under different parallel combination conditions, obtaining each distribution parameter under the unit length of the line polar wire. According to the scheme, in an environment with high induced voltage, the induced voltage can be effectively suppressed, and line parameters can be accurately measured.

The invention discloses a three-phase five-column transformer equivalent circuit model construction method and device, and the method comprises the steps: building a geometric model of a three-phase five-column transformer in finite element simulation software, carrying out the zero-sequence short-circuit test and the positive-sequence short-circuit test of the geometric model of the three-phase five-column transformer, obtaining the zero-sequence short-circuit impedance and the positive-sequence short-circuit impedance between windings, and obtaining the equivalent circuit model of the three-phase five-column transformer. A coupling leakage inductance matrix representing the coupling relation of the windings of the three-phase five-column transformer is calculated, and an equivalent circuit model of the three-phase five-column transformer is constructed in electromagnetic transient simulation software based on the coupling leakage inductance matrix of the three-phase five-column transformer. The technical problems of high resource consumption and long simulation time existing in modeling of the equivalent circuit model of the three-phase five-column transformer in an existing finite element modeling mode and the problem that the coupling relation among three-phase windings cannot be accurately represented in modeling of the equivalent circuit model of the three-phase five-column transformer in an equivalent circuit modeling mode are solved. And the accurate simulation requirement of a multi-winding structure cannot be met.

The high-impedance angle-joint phase-shifting transformer is mainly composed of a three-column iron core, an excitation winding, a phase-modulation winding, a phase-modulation on-load tap-changer and reactors, the two ends of the excitation winding are connected with the two three-phase reactors in series respectively and then are in triangular connection, and the third end of the excitation winding is connected with the phase-modulation winding; one end of a moving contact of the phase modulation switch is connected with the phase modulation winding, and the other end of the moving contact of the phase modulation switch is connected in series with a third three-phase reactor after three phases are led out; the phase angle between the voltage of the power supply side and the voltage of the load side is changed by adjusting the number of turns of coils connected into a circuit through the phase modulation winding through the phase modulation switch, and loop closing and power flow control of the transformer are achieved. According to the invention, overvoltage from a power grid is borne by the reactor, and the reactor adopts a shielding or entanglement mode to improve the capability of withstanding overvoltage impact. In addition, the reactor is connected in series, so that the overall short-circuit impedance of the phase-shifting transformer is improved, and the short-circuit resistance of the phase-shifting transformer is improved.

The invention discloses a same-tower parallel four-circuit alternating-current power transmission line parameter measurement method for inhibiting induced voltage. The method comprises the following steps: dividing a same-tower four-circuit power transmission line into five groups of wiring modes; measuring the short-circuit impedance in each wiring mode and the series impedance in a mode that the tail end of the line is grounded through impedance; calculating the characteristic impedance and the propagation coefficient in the corresponding wiring mode by using the impedance grounding series impedance measurement result and the line short-circuit impedance measurement result of the line in each wiring mode, and further calculating the distribution impedance and the distribution admittance in the corresponding mode; and finally, calculating the resistance, inductance and ground capacitance of each phase lead of the same-tower four-circuit line, the inter-phase coupling capacitance and inter-phase coupling inductance of the single-circuit line, and the coupling capacitance and coupling inductance between each phase lead of the four-circuit line through the distributed impedance and distributed admittance in each wiring mode and simultaneous equations. According to the method, the no-load power frequency induced voltage of the line can be effectively suppressed, and the line parameters can be accurately measured.

The invention relates to the technical field of power system automation, and discloses a short-circuit parameter measurement optimization method suitable for multiple scenes, which comprises the following steps: acquiring electric data and environmental parameters of a power system, and carrying out standardized preprocessing; constructing a scene feature vector to represent the current system operation state based on the preprocessed data, establishing a basic measurement model for calculating the short-circuit impedance, and evaluating the precision of an initial measurement model; configuring model parameters through an optimization algorithm, and designing a fitness function to guide an optimization process; scene feature changes are monitored in real time, a collaborative optimization objective function is constructed based on scene switching judgment, and measurement model parameters are dynamically adjusted based on a gradient parameter updating method; and outputting an optimized short-circuit parameter measurement result. According to the method, through dynamic scene modeling and intelligent closed-loop optimization, the influence of environmental interference and working condition change on measurement can be eliminated, and the core problems that a traditional short-circuit parameter measurement method is insufficient in precision and poor in adaptability in a complex scene are solved.

The embodiment of the invention relates to the technical field of new energy grid-connected testing, and provides an automatic testing method for new energy fault ride-through and related products, and the method comprises the steps: obtaining an impedance partial voltage value of a preset partial voltage impedance circuit according to a preset fault voltage value during voltage fault ride-through and a short-circuit impedance value of a system impedance circuit; acquiring an actual fault moment voltage value of the new energy grid-connected point; according to the fault voltage set value and the actual fault moment voltage value, a voltage comparison error is obtained; if the voltage comparison error is smaller than or equal to the preset threshold value, the impedance voltage division value of the preset voltage division impedance circuit is kept unchanged, and the next preset fault working condition is tested; and if the voltage comparison error is greater than the preset threshold value, adjusting the impedance voltage division value of the preset voltage division impedance circuit, and returning to the step of determining the fault triggering moment. According to the embodiment of the invention, the fault ride-through automatic test based on the impedance voltage division method can be realized, and the fault accuracy and the test efficiency are effectively improved.

The invention belongs to the field of new energy grid-connected relay protection, and particularly relates to a pilot reactance protection method based on time domain model recognition. Presetting a pilot reactance protection action area according to the inherent impedance and capacitive reactance parameters of the power transmission line; acquiring three-phase current and voltage sampling values at two sides of the power transmission line, synthesizing differential voltage and differential current data, and calculating the variable quantity of two adjacent sampling points of the differential current; whether longitudinal reactance protection is started or not is determined according to the differential current variable quantity, and waveform similarity detection is conducted on currents on the two sides after protection is started; when a waveform similarity detection result is greater than a threshold value, an external fault is judged, and pilot reactance protection is locked; otherwise, establishing an R-L equivalent circuit model equation, performing parameter identification on the short-circuit impedance, and when the vector positions of the pilot resistor and the pilot reactance in the complex plane fall into a preset pilot reactance protection action area, performing pilot reactance protection section entering, and performing pilot reactance protection action after confirmation.

The present invention belongs to the field of power electronics technology and relates to a method for calculating the short-circuit impedance of a multi-winding transformer. The multi-winding transformer includes a primary winding P and n, where n ≥ 2, secondary windings. Given the rated voltage, rated current, and number of turns of each winding in the multi-winding transformer, the specific steps for calculating the short-circuit impedance are as follows: Step 1: Based on the ampere-turn balance principle, the number of turns of each of the secondary windings S2 to Sn is respectively equivalent to the number of turns of the secondary winding S1; Step 2: Treating the n secondary windings as a single secondary winding S to obtain the number of turns of the secondary winding S; Step 3: Based on the ampere-turn balance principle, the multi-winding transformer is equivalent to a two-winding transformer, and the short-circuit impedance is calculated as for a two-winding transformer. The present invention can simplify the short-circuit impedance testing steps of the multi-winding transformer and improve the test accuracy.

The invention relates to the technical field of electrical tests, and particularly discloses a static short circuit test method for verifying the differential protection polarity of a generator and a transformer, and the method comprises the steps: S1, obtaining a first technical parameter and a second technical parameter of a to-be-verified generator and a to-be-verified transformer respectively; s2, first short-circuit impedance and second short-circuit impedance of the generator to be verified and the transformer to be verified are calculated according to S1; s3, respectively calculating a first short-circuit power supply capacity and a second short-circuit power supply capacity of a generator and a transformer required by differential protection polarity verification according to the S2; s4, selecting an adaptive target frequency converter according to the first short-circuit power supply capacity and the second short-circuit power supply capacity; and S5, respectively setting a generator verification short circuit point and a transformer verification short circuit point on the generator to be verified and the transformer to be verified, and carrying out differential protection polarity verification on the generator-transformer group protection device according to a static short circuit test method. According to the invention, the safety and economy of the test can be improved.