130 results about "Distributed parameter model" patented technology

The present invention discloses a failure distance-measuring method of uniform and non-uniform zero-sequence mutual inductance and multi-loop circuit with loops of different voltage levels arranged on the same rod or with the same electricity-transmitting corridor. Based on a distributed parameter model, the method samples the voltage and current synchronously at two ends. As for the parallel multi-loop circuit with the loops arranged on the same rod and with the same electricity-transmitting corridor, the influence of mutual inductance of the positive sequence and negative sequence between the loops can be ignored. When the power line has a single-line or over-line failure, the positive-sequence voltage and the negative-sequence voltage, which are respectively calculated from two sides of the fault point, should be equal to the sum of the positive-sequence voltage and the negative-sequence voltage, so as to solve the fault distance equation based on the positive-sequence component, negative-sequence component, or the positive-sequence and negative-sequence component. When the protection indicates that the line has an internal failure, the failure distance can be measured according to the fault distance equation. The mutual inductance between the lines which can be even or uneven has no influence on the distance measurement of the loops arranged on the same rod. The method can be used for precise distance measurement of the loops arranged on the same rod, which have various topological structures.

The invention discloses a simulation method for calculating the lightning back-striking performance of UHV transmission lines. The simulation method comprises the following steps: dividing wires among long-span transmission towers into a plurality of line segments, establishing a distributed parameter circuit model for each line segment, establishing a multi-wave impedance model for each tower, then selecting the lightning parameters according to lightning activities, integrating all models and calculating the lightning withstand level, and calculating to obtain the back-striking trip rate of the UHV transmission lines according to the lightning withstand level and a series of formulae. The simulation method disclosed by the invention establishes the distributed parameter models of the line segments in consideration of high long-span transmission towers and long line spans, subdivides the wave impedance of different parts of the towers, and establishes the multi-wave impedance models in consideration of the refraction and reflection processes of lightning waves on the tower bodies so as to make the simulation results more precise and practical.

A power distribution network one-phase grounding fault location method based on a zero sequence voltage belongs to a power distribution network grounding fault location method. The fault location method starts from an overall zero sequence parameter of a single-end radial medium voltage power distribution network, analyzes a one-phase grounding fault while taking a distributed parameter model influence into consideration, measures a steady-state zero sequence voltage value and a zero sequence current of each feeder line at a bus position and at a tail end of each outlet line, and finds zero sequence voltage variation characteristics of a fault feeder line and non-fault feeder line. According to the invention, a large number of existing devices are used, the data sampling requirement is low in terms of being real-time, and the method of the invention is easy to realize; the simulation model analysis is established according to the actual parameters, so that the fault location can be realized in the system in which the neutral point is not grounded or the neutral point is grounded through an arc suppression coil; the precision is quite high; and the location method of the invention can be applied to the medium and low voltage power distribution network.

The invention relates to the relay protection field of electric transmission line of electric power system, in particular to a distance protection method based on the distributed parameter model. The invention is aimed to solve the problem that the current distance protection is affected by distributed capacitance current and harmonic. The invention uses the voltage and current in the protection mounting place to compensate the end of the section I of the distance according to the distributed parameter model, and simplifies the line between the end of the section I and the fault point into a R-L model. That weather the fault is at inside or outside can be determined by solving differential equation. The invention has the advantages that: comparing to the distance protection based on the R-L model of the electric transmission line, the invention avoids the affect of distributed capacitance current and harmonic; comparing to the distance protection based on the pi model of the electric transmission line, the invention has higher reliability on fault determine; comparing to the distance protection based on the Bergeron model of the electric transmission line, the invention has the advantages of low requirement on sampling rate, low amount of calculation, low requirement on the hardware for the distance protection apparatus.

The invention discloses a UHV DC transmission line protection method utilizing current abrupt change characteristics based on a distributed parameter model. The UHV DC transmission line protection method comprises the steps of processing voltage and current signals measured by transformers at both ends of a DC line by means of an intelligent electronic device (IED), and identifying internal and external faults according to polarities of current abrupt variables. The UHV DC transmission line protection method adopts a distributed parameter model for carrying out distributed capacitive current compensation, eliminates the influence of asynchronization of the distributed capacitive current and data. A protection criterion selects components with the frequency band of [0,100] Hz in current information, avoids the electromagnetic coupling between DC side characteristic harmonics and a bipolar DC line and the influence of lightning interference. The polarities of current abrupt variables at both ends of the line are Boolean quantities, and the communication traffic of longitudinal channels is small. The UHV DC transmission line protection method utilizing the current abrupt change characteristics based on the distributed parameter model only utilizes polarities of the current abrupt variables for identifying the internal and external faults, is simple in principle and small in communication traffic, and is stable and reliable.

The invention discloses an ultra-high-voltage transmission line relay protection method based on a break variable differential coefficient matrix. The method includes by utilizing a distributed parameter model, computing three-phase current break variables of the other end of an ultra-high-voltage transmission line by positive, negative and zero-sequence voltage break variables and current break variables of one end of the ultra-high-voltage transmission line and positive, negative and zero-sequence current break variables of the other end of the ultra-high-voltage transmission line by the aid of a symmetrical component method, further computing the break variable differential coefficient matrix, forming protection criterions according to size relationships of elements of the break variable differential coefficient matrix, and distinguishing fault phases of the ultra-high-voltage transmission line. The distributed parameter model is used as a physical model and unaffected by distributed capacitance current, and the method is applicable to any voltage classes and in particular to ultra-high-voltage transmission lines.

The invention discloses a series-compensation double-circuit line fault locating method based on a distributed parameter model. The method comprises a step I, a six-sequence component method is adopted to perform decoupling, and a reverse voltage cross a bus on two sides is zero when a fault occurs in a circuit after the decoupling is performed; a step II, according to characteristics that voltages at a fault spot are equal and currents at two ends of a series compensation device are reverse and which are respectively reckoned from the two sides, a series compensation voltage and the currents at the two ends in a transmission equation are eliminated; and a step III, by utilizing a pure resistance property of a transition resistor at a position of the fault spot and a fault timing sequence network boundary condition, a fault locating function when double-circuit lines containing series compensation are erected on the same pole is constructed, and a fault distance is solved by utilizing the fault locating function when the fault occurs. The method does not rely on a model of the series compensation device and is not influenced by MOV nonlinearity, a position of the fault spot relative to the series compensation does not need to be known in advance, the ranging principle is simple, one-dimensional searching for the fault distance is needed only, and a pseudo root discrimination problem does not exist.

The invention relates to a zero-sequence parameter measuring method for an ultrahigh-voltage transmission line with a four-circuit alternating current on one tower and a double-circuit double-electrode direct current. By setting up an ultrahigh-voltage transmission line model with the four-circuit alternating current on one tower and the double-circuit double-electrode direct current based on distribution parameters, the zero-sequence voltages and the zero-sequence currents at the head end and the tail end of an ultrahigh-voltage transmission line with the four-circuit alternating current on one tower and the double-circuit double-electrode direct current are simultaneously measured through the GPS, and therefore the zero-sequence voltages and the zero-sequence currents can be synchronously sampled; then, parameters such as zero-sequence resistance, zero-sequence inductance and zero-sequence capacitance of the ultrahigh-voltage transmission line with the four-circuit alternating current on one tower and the double-circuit double-electrode direct current are obtained through the measuring and calculating method. According to the method, by means of the model based on the distribution parameters and a transmission line equation, measuring accuracy is greatly improved, and the method can meet the requirement of actual engineering measurement.

The invention provides a direct-current transmission line low-voltage protective method built on the basis of a time domain distributed parameter model. The voltage value in the end of a protective range is obtained by utilizing a time domain calculating method of a line voltage according to the voltage and current measured values at a protection installation position, and a protection criterion is constructed by utilizing the voltage calculated value of the protective range end. When a line end voltage calculated value and the voltage calculated value at the protection installation position have opposite signs, a metallicity or low-transition resistor fault happens in a power transmission line area is judged, so that quick protection action is carried out; and when the line end calculated voltage amplitude is less than a set value, a high-transition resistor fault or an outside fault happens in the power transmission line area is judged, and selectivity is provided when in related protection coordination, so that at the moment, protection action can be realized after time is delayed. The method is realized in a time domain, so that a needed data window is short and calculating amount is low. The method is mainly used for the relay protection of the direct-current transmission line in an electrical power system.

The invention discloses a range finding method for a single-phase earth fault of a line based on actual measurement of transition resistance. The method includes the steps of measuring fault phase voltage, fault phase current, fault phase negative sequence current and zero sequence current at the protective installation part of a power transmission line, describing the physical characteristics of voltage and current transmission of the power transmission line by using a distributed parameter model, calculating the transition resistance at the single-phase earth fault point of the power transmission line, and sequentially calculating the transition resistance and transition resistance difference function value of each point on the power transmission line by using a one-dimensional searching method. Accurate range finding for the single-phase earth fault of the power transmission line is realized by using the characteristic that the transition resistance difference function value at the fault point of the power transmission line reaches the minimal value, which theoretically eliminating the influence of the factors including distribution capacitance, transition resistor and load current, and ensuring high range finding precision. The method is a searching method which means no false solution problem of equation solving methods and misconvergence problems of iterative methods, and the method is highly practical.

The invention relates to a method for recognizing a single-phase permanent fault of a single-ended electric transmission line with a paralleling reactor. Existing fault property adjustment methods are different in application range and can be influenced by various factors. According to the method for recognizing the single-phase permanent fault of the single-ended electric transmission line with the paralleling reactor, the single-end sound-phase current and the current of the paralleling reactor are sampled firstly after fault-phase tripping, then the quantity of corresponding phases can be extracted with the full-wave Fourier algorithm, and thus the line voltage of the local-end and the current of the line in the flow direction can be represented according to the quantity of the corresponding phases; then, the voltage and current of a fault point relevant to the double-end voltage and current are calculated respectively according to a permanent fault distributed parameter model, it is deduced that the voltage to ground and current to ground of the fault point are only relevant to the single-end sound-phase current and the current of the paralleling reactor according to the boundary conditions which are met by the voltage and current of the fault point and the condition that the phase current of the opposite end is zero after fault tripping, and thus transition resistance can be calculated; the property of the fault can be recognized accurately through continuous calculation of the transition resistance. The method for recognizing the single-phase permanent fault of the single-ended electric transmission line with the paralleling reactor has the advantages that the fault property judgment is influenced by few factors, and the sensitivity is high.

The invention discloses a wind power farm grid-connected power transmission line instant single-phase grounding fault single-end distance measuring method. Three-phase voltages and three-phase currents at two specific moments are acquired on a wind farm side, and are used as inputs, and the three-phase voltages and the three-phase currents acquired on the wind farm side at two specific moments are used to calculate corresponding positive, negative, zero sequence voltage, current phasors. Based on a power transmission line distribution parameter model, the calculated wind farm side voltage, current sequence components are used to establish voltage, current relations on two ends of a power transmission line. Power supply potential, equivalent system impedance, fault distances and transition resistors of a system side are adopted as unknown quantities, and an established non-linear electric equation set is solved by using an improved Levenbery-Marquardt method, and an accurate fault distance measuring result is acquired. A problem of wind power farm grid-connected power transmission line fault distance measurement is effectively solved.

The invention, which belongs to the field of relay protection of a power system, particularly relates to a single-ended fault ranging method of an alternating-current line for flexible direct-currentfeeding. The method comprises the following steps that: after a power transmission system detects a single-phase ground fault, a single-ended electrical quantity of a conventional alternating-currentpower supply side is collected; discrete Fourier transform is carried out on an electrical quantity in a sampled data window and a fundamental frequency component is extracted; with a symmetrical component method, phase-mode transformation is carried out on the fundamental frequency component in a frequency domain to obtain sequence components of a fault voltage and a fault current; on the basis of a distributed parameter model, fault voltage and negative-sequence fault current distribution of a fault phase along a line is calculated; a data group formed by fault voltages and negative-sequencefault currents of fault phases at different distances at different times along the line is obtained in a time domain and fault ranging is carried out by using unary linear regression according to thecharacteristic of meeting a direct proportional linear relationship by the data group only at a fault point. Therefore, a problem that the traditional fault location method has low applicability is solved; and the single-ended fault ranging method has advantages of high ranging accuracy and wide applicability.

A method of dynamic contrast enhanced (DCE) imaging includes: for a region of interest, sampling the concentration of a tracer liquid in a fluid over a time interval to arrive at a plurality of samples; fitting the plurality of samples to a plurality of multi-compartment mamillary pharmacokinetic models, each of the plurality of models modelling fluid flow in a number of interstitial compartments about a central compartment at the region interest, as a result of flow caused by a source of the fluid, so as to determine a plurality of fitting parameters for each of the plurality of models; determining a preferred one of the plurality of models; and presenting indicators indicative of values of the plurality of parameters for the preferred one of the models. Numerous multi-compartment mamillary pharmacokinetic models are disclosed. The models and methods may be used in DCE imaging systems and software.

The invention relates to a frequency domain method of fault location of a high-voltage direct current earth electrode line based on a distributed parameter model, and belongs to the field of fault location technologies of power systems. The frequency domain method comprises the following steps of computing voltage distribution along the earth electrode line from a measuring end by utilizing the measured voltage and current of a fault line when the high-voltage direct current earth electrode line has an earth fault; calculating an electrode address point by utilizing the measured voltage and current of a non-fault line, and computing the voltage and the current of the electrode address point; computing the voltage distribution along the earth electrode line from an electrode address end by utilizing the voltage and the current of the electrode address point, writing out a fault location function according to pure resistivity of a transition resistor at the fault point, and computing a fault distance through solving the location function. The frequency domain method is capable of implementing the fault location of a single end of the earth electrode on the basis of the conventional fault measurement data, parameters of an opposite end are not needed, and the frequency domain method has the advantages of simple algorithm and easiness in implementation.

The invention relates to a method for positioning transmission line fault based on power frequency phasor, which comprises the following steps: confirming a characteristic impedance of propagation constant line according to a distribution parameter model of the transmission line; measuring the voltage Un and current In at tail end N of the transmission line by measuring the voltage Um and current Im at the starting end M of the transmission line, wherein DL is the actual length of transmission line; and calculating a distance DMf between the starting end M of the transmission line and the fault point according to the formula: DmF is equal to [th-1(BJ/AJ)]/gammaJ, thereby increasing the precision of positioning the transmission line fault.

The invention provides a novel distribution type fin compact heat exchanger designed by the combination with a distributed parameter model, which comprises a baffle plate, a hot fluid side fin, a cold fluid side fin, an end cover and the like. The heat exchanger is characterized in that the idea of the distributed parameter model is applied to the design of the heat exchanger, and the fin types, the number of fins and the fin sizes at different positions in the heat exchanger can be particularly designed according to the heat exchanging conditions at the positions, and the heat exchanging capability in the limited space can be maximized, and the resistance is minimized, thereby lowering energy consumption and saving materials; moreover, the hot side fin and the cold side fin can both be the combination of the fins with various structural sizes.