247 results about "Short circuit impedance" patented technology

The invention discloses a vehicle-mounted transformer comprehensive test system. The system is characterized by comprising an industrial personal computer (IPC), a communication module, a hub conversion plate, a short-circuit impedance short connector, a load switch adjuster, and a comprehensive test device, wherein the IPC carries out data communication with each test device of the comprehensive test device through the communication module; each test device of the comprehensive test device is connected with the hub conversion plate through an internal connection wire; the hub conversion plate is connected with a tested transformer through a test wire; a medium-voltage short-circuit impedance short connector and a low-voltage short-circuit impedance short connector are respectively connected with the medium-voltage side and the low-voltage side of the tested transformer through the test wire; the load switch adjuster is connected with a load switch adjusting device of the tested transformer through the test wire. The comprehensive test system provided by the invention can complete all of the test items by a single connection, thereby avoiding frequent replacement of instruments and connection wires.

The invention belongs to the technical field of electrical power systems, and particularly relates to an on-line measurement method for deformation of a transformer winding. Because change conditions of a short-circuit reactor of the transformer directly reflect the degree of deformation of the transformer winding. An on-line detecting principle comprises that an equivalent short-circuit impedance value of the transformer is deduced according to a T-type equivalent circuit model of the transformer, on the basis, a short-circuit reactance value of the transformer is calculated, a data acquirer is used for acquiring voltage and current signals of a primary end and a secondary end of the transformer, the acquired voltage and current signals are subjected to numerical calculation, finally, the voltage and current signals which are subjected to numerical calculation are calculated according to a curve-fitting principle, and on-line measurement of short-circuit reactance of the transformer is realized. By the measurement method, the short-circuit reactance of the transformer can be measured accurately, and the deformation condition of the transformer winding can be accurately judged.

The invention discloses an accurate measurement and calculation method for parameters of a power transmission line. In the method, the parameters of the power transmission line are accurately calculated according to short-circuit impedance ZS and open-circuit impedance ZO of the power transmission line. The method comprises the following steps of: measuring the short-circuit impedance ZS and the open-circuit impedance ZO of the power transmission line with length of D; acculate calculating characteristic impedance zc and propagation coefficient gamma of the power transmission line according to a calculation formula provided by the invention; further, calculating impedance z and admittance y under the condition of unit length of the line through the formulas of z=zc gamma and y=gamma/zc; and accurately calculating impedance Z' and admittance Y' of an equivalent pi circuit of the power transmission line according to the calculation formula provided by the invention. By adopting the measurement and calculation method provided by the invention, the accuracy for the parameters of the power transmission line can be greatly improved, manpower and material resources are saved, tide current of a power system is stably analyzed; protection setting is performed; and fault positioning is more accurate.

A surface-acoustic-wave filter couples a two-port surface-acoustic-wave resonator filter circuit coupled in parallel or in series with a two-port impedance circuit. The two-port impedance circuit has an impedance that creates a pole of attenuation, by making the open-circuit impedance of the surface-acoustic-wave filter equal to the short-circuit impedance. High attenuation over a wide range of stopband frequencies is obtained in this way, combined with steep roll-off between the passband and stopband.

The invention discloses an overall test and construction method of a differential protection system of a large-scale transformer, which comprises the steps of: firstly, short-connecting an appropriate position at the low-voltage side of the transformer with a bus bar by using a short circuit clamp and utilizing the characteristic of short-circuit impedance of the transformer, and arranging a low-voltage power supply at the high-voltage side of the transformer so as to obtain short-circuit large current in a primary circuit of the differential protection system of the transformer; then, clamping the current of all phases in a differential current secondary circuit of a relay protecting screen by a double-pincerlike phase meter, recording the phase differences and values of all phases, and comparing with all phases of current of the differential circuit of a synthetic microcomputer protection device; and displaying the numerical value on the double-pincerlike phase meter, and outputtinga tripping signal when the numerical value reaches a certain operating value so as to realize the overall test of the whole differential protection system of the transformer. In the test method, lines do not need to be disassembled or assembled, and any primary circuit or secondary circuit is not changed; and the test method is characterized by simpleness, convenience and high efficiency.

The invention relates to an integrated test stand for transformers, which comprises a test stand body, a CPU (central processing unit), a keyboard, a liquid crystal display, a switch control circuit, a test wiring switching circuit, a bushing end shield grounding terminal, a wireless communication module, a remote controller, an LED display and an LED alarm lamp screen. The integrated test stand has the advantages that (1), a wire outlet terminal of a winding of a transformer can be automatically switched onto corresponding testing equipment according to testing items, equipment side wiring and instrument side wiring do not need to be changed, required testing staffs are few, testing time is short, and operation is safe; and (2), the testing items for insulating resistance of the winding, dielectric loss of the winding, direct-current resistance of the winding, low-voltage short-circuit impedance, on-load switch recording, transformation ratio of the winding, bushing testing and the like of the transformer can be completed by one-step wiring.

The invention discloses an impedance-self-adaptive inverter reactive voltage control parameter optimization method which is characterized in that a power distribution network Jacobi matrix and a reactive voltage amplitude sensitivity matrix are obtained via load flow calculation firstly; then coupling decomposition is performed on the reactive voltage amplitude sensitivity matrix by utilizing an epsilon decoupling algorithm and a power distribution network comprising distributed photovoltaic is correspondingly divided into subareas which are not mutually overlapped; then short-circuit impedance of each inverter access point is measured in an online and real-time way via an impedance self-adaptive method, and dead zone width D controlled by inverter reactive voltage V(Q) is confirmed by the measured short-circuit impedance; and finally optimization and setting of the dead zone width D controlled by the inverter V(Q) of each subarea are performed with the minimal whole year voltage fluctuation of each subarea of the power distribution network, the minimal reactive power demand and the lowest network loss acting as the objectives. A problem of inverter parameter online self-adaptive setting is solved so that photovoltaic consumption capacity of the power distribution network is enhanced and distributed photovoltaic safe and friendly grid connection is also realized.

The invention provides an online evaluation method for the capacity of a power distribution transformer. The method comprises a step of using a correlation coefficient method to realize the automaticidentification of a power distribution transformer connection group, a step of calculating Dyn11 distribution transformer short-circuit impedance and Yyn0 distribution transformer zero-sequence impedance and comparing the impedances with a standard reference value, and a step of finally obtaining a power distribution transformer evaluation capacity. According to the operating voltage data of the power distribution transformer, a correlation coefficient method is applied to realize the self-identification of the power distribution transformer connection group. Under the condition that the primary side electric quantity of the power distribution transformer cannot be obtained, the rated capacity of the power distribution transformer can be accurately evaluated by a Dyn11 distribution transformer capacity online evaluation method. Under the condition that a neutral point of a Yyn0 distribution transformer is offset, the rated capacity of the power distribution transformer can be accurately evaluated by a Yyn0 distribution transformer capacity online evaluation method.

The invention discloses an SOGI-based single-phase transformer short-circuit parameter on-line real-time identification method. The identification method comprises steps of establishing a T-type equivalent circuit of a single-phase transformer; listing the short-circuit impedance parameter equation and the T-type equivalent circuit equation of the transformer; respectively obtaining the d axis equation and the q axis equation of the T-type equivalent circuit in a dq coordinate system; and using a SOGI-FLL model to extract fundamental wave components and fundamental wave orthogonal components of all input signals, obtaining the d axis component and the q axis component of all input signals in the dq coordinate system, and calculating the short-circuit resistance values Rk and Xk of the single-phase transformer, thereby achieving on-line monitoring of operation states of single-phase transformer windings. When windings of the transformer deforms and break down, the short-circuit impedance of the transformer will change. By measuring voltage and current of the primary side and the secondary side of the transformer, short-circuit parameters of the transformer windings can be identified. Thus, on-line monitoring of the operation states of the transformer windings is achieved; potential risks of the transformer can be found as soon as possible; fault points can be timely removed; operation accidents can be avoided; and service lifetime of the transformer is extended.

The invention discloses a method for automatically measuring a direct-current resistor, a short-circuit impedance, an on-load switch and a non-load voltage ratio of a transformer. In the measurement process, the opening-and-closing status of a high-pressure switch can be controlled so as to achieve the status of a transformer winding in the measurement process, and the status is pressurization or an open circuit or a short circuit or grounding. The current measuring item is selected by controlling a multi-way selection switch, and the item is the direct-current resistor or the on-load tapping switch or the short-circuit impedance or the non-load voltage ratio. The method can achieve automatic measurement of the direct-current resistor, the on-load tapping switch, the non-load voltage ratio and the short-circuit impedance of the power transformer, the winding status is automatically switched in the whole measurement process, manual intervention is not required, the measurement error can be reduced, working intensity can be relieved, and working efficiency is improved.

The invention discloses an apparatus for large-scale oil-immersed transformer no-load and on-load comprehensive tests and a method. The apparatus is composed of a test power source part and a measurement system. The test power source part includes an induction regulator, an intermediate transformer, an oil-immersed intensive compensation capacitor bank and a test control system which are successively connected via a circuit. The measurement system includes a precision measurement current transformer, a voltage transformer and a power analyzer. The apparatus can conduct on-site no-load and on-load loss measurement tests on 110-kV and 220-kV voltage class transformers, and can complete measurements of no-load current, no-load loss, no-load harmonic waves, short circuit impedance and load loss of transformers, and can automatically calculate the measurement test results of no-load and load loss.

The invention discloses a method for detecting deformation of power transformer windings. The method includes the following steps that the short-circuit impedance relative change rate, the overall correlation coefficients of amplitude-frequency curves, the amplitude-frequency curves of a low frequency band, a medium frequency band and a high frequency band, the local correlation coefficients of the amplitude-frequency curves of all the frequency bands, the voltage ratio deviation and the capacitance relative change rate are acquired; the deformed windings and phase results are acquired according to the short-circuit impedance relative change rate and the overall correlation coefficients of the amplitude-frequency curves; according to the correlation coefficient of the amplitude-frequency curve of the low frequency band and the voltage ratio deviation, turn-to-turn or cake-to-cake short circuit detection results are acquired; according to the correlation coefficient of the amplitude-frequency curve of the medium frequency band and the capacitive relative change rates between the windings, local deformation results are acquired; according to the correlation coefficient of the amplitude-frequency curve of the high frequency band and the ground capacitance relative change rates of the windings, whole displacement or lead displacement deformation detection results of winding coils are acquired; the results are logically processed, and a comprehensive detection result is acquired. According to the method, reliability of the deformation detection result of the power transformer windings is greatly improved.

The invention discloses a method for deformation test of a transformer winding by utilization of a frequency sweep short circuit impedance method. The method integrates advantages of test technologies of a frequency response method and a short circuit impedance method, corresponding improvement is carried out, and therefore a short circuit impedance value of a transformer at 50Hz can be extracted and calculated in a low frequency stage through one-time measurement. Through comparison with the nameplate value, whether the transformer deforms can be determined elementarily and directly. In addition, further determination can be carried out by comprehensive utilization of other determination methods, so good determination effects can be achieved. The method is advantaged by convenient operation and high accuracy, and has good popularization and application values.

The invention provides a transformer winding deformation and short-circuit impedance change relationship analysis method which comprises a step of using a finite element method to establish a finite element simulation model of transformer winding displacement, wherein each pillar in the finite element simulation model comprises high, middle and low transformer windings, and disc modules are employed by the transformer windings, a step of using a middle-low voltage winding operation mode lower field circuit coupling model to process a winding in a finite element area as an inductor in a circuit, wherein the lower field circuit coupling model is obtained by coupling an electromagnetic field and a circuit generated by the electromagnetic field generated in the operation of a transformer, and a step of simulating the change trend of transformer short-circuit impedance when the transformer windings have radial displacement and axial displacement based on the field circuit coupling model. By using the method, a transformer winding deformation and short-circuit impedance change relationship can be accurately analyzed, a winding deformation security risk is timely found, the elimination of a possible sudden failure of the transformer in a maintenance cycle is facilitated, and an accident is prevented.

The invention relates to a capacitance-current measuring system and method of power distribution network with an ungrounded neutral point, and relates to capacitance and current measuring technology of the power distribution network. The measuring system comprises a bus voltage transformer, an adjustable resistor, a frequency-variable voltage source and a voltage measuring instrument, the adjustable resistor and the frequency-variable voltage source are connected in series and then connected to the two ends of a third winding of the bus voltage transformer, and the voltage measuring instrument is also connected to the two ends of the third winding of the bus voltage transformer. The method by which the measuring system is used for measurement solves the problem that short-circuit impedance of the bus voltage transformer influences the measuring precision, influence of zero sequence voltage on the capacitance and current measured by a signal injection method caused by imbalance degree of the electrical network is taken into consideration, the capacitance and current measuring accuracy of the power distribution network is improved, an accurate Thevenin's equivalent circuit model is used, and the grounding capacitance of the system is solved. A measuring process is carried out in the third winding side of the transformer, wiring of primary equipment needs not to be changed, the measuring method is safe and convenient, and a result is accurate and reliable.

The invention provides a mechanical-state on-line monitoring device of a transformer winding. The output end of an electricity quantity sensor is connected with a synchronous square wave conversion circuit and an anti-aliasing low-pass filter, and the anti-aliasing low-pass filter is connected with a control unit sequentially through an amplitude-limiting circuit and an A/D conversion circuit, the synchronous square wave conversion circuit is connected with the A/D conversion circuit sequentially through a zero cross detection circuit, a modified phase locking frequency multiplier circuit and a sampling control selection circuit; the control unit comprises a single-chip microcomputer unit and a digital signal processor, the single-chip microcomputer unit and the digital signal processor are connected through a double-port RAM, the digital signal processor carries out transformer short-circuit impedance calculation on electric parameter digital signals sent by the A/D conversion circuit, and the single-chip microcomputer unit stores and displays the data and sends the data to an electricity system monitoring platform. Compared with the prior art, the mechanical-state on-line monitoring device of the transformer winding can carry out real-time on-line monitoring on transformer short-circuit impedance, avoid a sudden breakdown of a transformer due to sudden mechanical faults, and largely improve the operation reliability of the transformer.

The invention relates to a high-capacity unified power quality conditioner based on a chain structure and a control method of the high-capacity unified power quality conditioner. A three-phase three-wire system series-and-parallel structure is adopted in the high-capacity unified power quality conditioner. The high-capacity unified power quality conditioner comprises a series type voltage source converter and a parallel type voltage source converter, wherein the series type voltage source converter and the parallel type voltage source converter are connected through a common direct-current bus, single-phase H-bridge cascade structures are adopted in the series type voltage source converter, the H-bridge cascade structure of each phase is connected to an alternating-current side power grid through a series capacitor, single-phase H-bridge chain link structures are adopted in the parallel side converter, a back-to-back structure is formed by the single-phase H-bridge chain link structures and H-bridge chain links of the series type voltage source converter, and each H-bridge chain link of the parallel side converter is connected to a direct-current side power grid through the secondary side of a single-phase multi-winding transformer. The invention further provides the control method of the high-capacity unified power quality conditioner. According to the high-capacity unified power quality conditioner, a series side transformer is omitted, short-circuit impedance of a loop is reduced, voltage accuracy of open-loop control is improved, performance of the high-capacity unified power quality conditioner is improved, and the problem that the instantaneous inrush current phenomenon happens when voltage drop of the series side happens is solved.

The invention discloses an operational curved surface method for determining asymmetric short-circuit current of a distributed generation access power grid. The method comprises steps of acquiring a three-node simplified network and transfer impedance between different nodes by using network simplification when multiple DGs and conventional generators have access to the power grid; in view of different types of asymmetric short-circuit faults, ignoring the influence of DG zero-sequence current injection, obtaining a short-circuit calculation compound sequence network and positive and negative sequence augmented networks according to a fault point boundary condition, and calculating the additional voltage and additional impedance in the augmented networks; performing Thevenin equivalent on systems except the DG access points in the positive and negative sequence networks, and deriving short-circuit impedance and open-circuit voltage open-circuit voltage computational formulas when DC injection current is zero; establishing a operational curved surface of a DG short-circuit current negative-sequence component, computing impedance, and positive and negative sequence open-circuit voltage in order to obtain a DG short-circuit current negative-sequence component; calculating a DG asymmetric short-circuit current positive-sequence component in combination with a three-phase short-circuit operational curved surface according to a DG access positive-sequence augmented network access point equivalent open-circuit voltage computing method.

The invention discloses an online monitoring method for the short-circuit impedance of a V/X connection traction transformer. In two time intervals when the negative feeder line current of a power supply arm is 90-95% of the rated current and 95-100% of the rated current, the method tests and records a voltage vector and a current vector of the incoming line side and the feeder line side of the transformer respectively, calculates to obtain a primary test value of the short-circuit impedance by use of a deduced formula, and repeatedly tests and calculates for n times (n is not less than 20) to obtain two groups of primary test data; for each group of data, the method judges the relative standard deviation of the primary test data to eliminate the data with large error; and if the number of the eliminated data is less than n/4, the average of the remaining data is the value of the tested short-circuit impedance. The method is simple to test and has high accuracy; and the curve of the monitored short-circuit impedance changing with time can be used as the basis for monitoring and judging the winding deformation.

The embodiments of the invention disclose a parameter measurement method for high-voltage and ultra-high-voltage direct-current transmission lines. According to the method, a direct-current transmission line model having distributed-parameter characteristics is constructed. Meanwhile, the expression of the impedance per unit length and the admittance per unit length, corresponding to the direct-current transmission line model, is established, wherein the earth resistance is involved. During the resolving process of a mathematical model, a homogeneous differential equation between the voltage and the current of the line in the boundary condition is solved to obtain a two-port power transmission line equation, wherein a telegraph equation is involved. After that, assisted by the open-circuit measurement means and the short-circuit measurement means at the end of the transmission line, the open-circuit impedance and the short-circuit impedance at the sending terminal of the transmission line are respectively measured. Furthermore, the distribution parameters of the direct-current transmission line are solved out and a computational formula for the earth resistance per unit length is given. According to the technical scheme of the invention, initial measurement data are acquired through constructing the transmission line model. Meanwhile, the two-port power transmission line equation is solved accurately. Therefore, the precise distribution parameters of the direct-current transmission line can be obtained.

The invention discloses a transformer winding deformation intelligent detection method based on sweep frequency impedance curve identification. A short-circuit impedance method and a frequency response analysis method are combined, a transformer winding equivalent circuit model is established and acquisition of a transformer winding sweep frequency impedance curve is performed; the method comprises the following steps: under the condition that a sampling resistor R and a voltage U of the sampling resistor R are known, a current I flowing through a winding can be obtained through a formula I =U/R, and a sweep frequency impedance method wiring mode which effectively combines a short circuit impedance method and a frequency response analysis method can be obtained; during testing, one side of a transformer winding is short-circuited by using a wire, and sine sweep signals with the frequency of 10Hz-1MHz are injected into the head end of the transformer winding on the other side; and theresistance values of sampling resistors RC1 and RC2 in the test system are 50 omega, so that the current flowing through the non-short-circuited side is shown in the description. According to the invention, the transformer winding deformation is intelligently detected according to the change condition of the element parameter value, the situation that the transformer winding deformation excessively depends on experienced professionals is avoided, the analysis conclusion is unified, and great convenience is brought to the maintenance decision.

A production method for three cleaving transmission transformer belongs to transformer technology field and solves impedance matching problem of three low press windings. It counts electric field, magnetic field, short circuit impedance, short circuit intensity and leak magnetic field of transformer to match impedance of three low press windings. a. Count voltage and current parameter. b. Select iron core parameter. c. Select loop parameter. d. Count short circuit impedance. e. Count spoilage, temperature rise and mechanical power. f. Confirm structure collocation type and parameter. It finds the rule about the three cleaving transmission transformer to solve the problem of high voltage winding circumfluence and keep the transformer with natural function at all kinds of load condition. When satisfied the coequal load condition, it can reduce 50% area and 15-20%spoilage with high over loading ability and its sequential course can reach to 115% of rated capability.

The invention belongs to the field of electric system reactive power compensation, and provides a combination switch type step controllable shunt reactor. The controllable shunt reactor body adopts a transformer structure and can be designed into two forms based on requirements, i.e. the high short circuit impedance form or the form of an ordinary transformer with an external reactor. In the controllable shut reactor, combination switches are controlled to be matched with body short circuit impedance, thus the output of reactive capacity and the step regulation can be realized; each combination switch includes a circuit breaker, a thyristor valve, and a reactor, wherein the circuit breaker is connected in series with the reactor; when the controllable shunt reactor operates stably at a capacity step, the circuit breakers are closed to bear long-term working current, and the thyristor valves do not need work for a long time; and during step regulation of capacity, the to-be-taken energy and the turning-on voltage are provided for the thyristor valves based on the divided voltage provided by the reactor connected with the circuit breaker in series, so that current can be connected and disconnected in a zero-crossing switching manner by the thyristor valves without switching on/off the circuit breakers, so that the service life of the circuit breaker is prolonged.