192 results about "Transmission line protection" patented technology

The invention discloses a method for analyzing ultra-high voltage direct current system lockout caused by a lightning stroke of an electric transmission line. The method comprises the first step of summarizing electric quantity characteristics and direct current circuit protection action characteristics in the lightning stroke lockout process, the second step of establishing an ultra-high voltage direct current system lightning stroke simulation model, the third step of establishing a converter station measuring system simulation model, the fourth step of establishing a control system and circuit protection simulation model, the fifth step of combining the three simulation models to form a closed loop real-time simulation system, and the sixth step of studying the ultra-high voltage direct current lockout situation caused by the lightning stroke by utilizing the simulation system. A lightning stroke simulation modeling method of an ultra-high voltage direct current power transmission system in a circuit with the length reaching to thousands of kilometers is put forward, the coupling real-time simulation of the lightning stroke simulation model and the circuit protection simulation model is achieved, and an effective means is provided for studying the ultra-high voltage direct current system lightning stroke lockout mechanism and optimizing the direct current transmission line protection definite value.

The invention provides a transmission line protection method and a transmission line protection device. The transmission line protection method comprises the steps that three voltage equivalent travelling waves of three voltage fault transient traveling wave phasors on one end of a transmission line are constructed, and three current equivalent travelling waves of three current fault transient traveling wave phasors on one end of the transmission line are constructed; the polarity of three voltage equivalent travelling waves and the polarity of three current equivalent travelling waves are acquired; according to the polarity of three voltage equivalent travelling waves and the polarity of three current equivalent travelling waves, whether one end of the transmission line has a forward fault is determined; if the fact that one end of the transmission line has the forward fault is determined, whether the other end of the transmission line has a forward fault is determined; if the determining result is yes, the transmission line is cut off to protect the transmission line. According to the technical scheme of the invention, whether the transmission line has a line fault can be quickly detected, and appropriate measures are taken to effectively improve the protection reliability of the transmission line.

A method for determining transient errors in an unsynchronized, digital current differential transmission line protection system includes receiving a first current phasor measurement at a time, t, and receiving a second current phasor measurement at time t. The second current phasor is adjusted so as to account for a determined offset between a first sampling clock associated with the first current phasor measurement and a second sampling clock associated with the second current phasor measurement, thereby resulting in a rotated second current phasor measurement. A residual transient error is then obtained from the rotated second current phasor measurement and the first current phasor measurement.

The invention relates to a half-wavelength transmission line protection method based on transient energy, belonging to the technical field of power system relay protection. If a fault is detected, thevoltage and current abrupt change are calculated by transient electrical quantities detected at the first and last terminals, , through the product of transient voltage and the current abrupt changes, the instantaneous power is calculated, and the transient energy is obtained by integrating the instantaneous power. Based on the polarity of the transient energy, the fault criterion is constructedin and outside the region, no matter where the fault point is located on the line, the method can reliably realize the fault identification in and outside the region. In addition, the polarity of transient energy is not affected by the fault angle and the transient resistance changes. Therefore, the transient energy protection method is suitable for half-wavelength transmission lines.

The invention discloses a line single-phase earth fault relay protection method implemented by the aid of distributed parameters. The line single-phase earth fault relay protection method includes measuring fault-phase voltages, fault-phase currents, fault-phase negative-sequence currents and a zero-sequence current at a power transmission line protection mounting position and using the fault-phase voltages, the fault-phase currents, the fault-phase negative-sequence currents and the zero-sequence current as input variables; computing voltage drop from a single-phase earth fault point to a power transmission line protection setting range position by the aid of a distributed parameter model, computing voltage drop from the power transmission line protection mounting position to the transmission line protection setting range position by the aid of the distributed parameter model, and then judging whether a leading angle between the voltage drop from the power transmission line protection mounting position to the power transmission line protection setting range position and the voltage drop from the single-phase earth fault point to the power transmission line protection setting range position is within the range between -90 degrees and 90 degrees or not. The line single-phase earth fault relay protection method has the advantages that the action performance is unaffected by distributed capacitance currents or transition resistance or load currents, actions can be correctly and reliably performed by the method when a power transmission line single-phase high-impedance earth fault occurs, and the method has high practical value.

The invention provides a method for processing the fault traveling wave of a flexible DC transmission line. The method comprises a step of obtaining the pole mode current and pole mode voltage fault transient traveling wave of the flexible DC transmission line, a step of obtaining a pole mode reverse voltage fault transient traveling wave, a step of obtaining the modulus maximum of the pole mode reverse voltage fault transient traveling wave, and obtaining the equivalent pole mode inverse voltage travelling wave of the pole mode reverse voltage fault transient traveling wave. According to the technical scheme of the invention, the difference between the fault traveling wave and high-frequency transient interference can be effectively displayed, thus the overall characteristic of a flexible DC transmission line fault is more simple and intuitive, the influences of direct current and low frequency signal in the pole mode reverse voltage fault transient traveling wave can be eliminated, the high frequency characteristic of a traveling wave process is highlighted, the analysis difficulty of a flexible DC system downgoing wave process is reduced, and the ultra high speed flexible DC transmission line protection is possible.

The invention discloses a single-phase ground fault type diagnosis method for an ultra-high voltage alternating current transmission line. The method includes the steps: firstly, modeling by a lumped parameter model and calculating a fault distance according to the linear relation between voltage drop and the fault distance from an ultra-high voltage alternating current transmission line protection mounting position to a single-phase ground fault point; secondly, accurately describing physical characteristics of voltage and current transmission of the ultra-high voltage alternating current transmission line by a long line equation and calculating compensation current of the transmission line according to the calculated fault distance; and thirdly, accurately diagnosing single-phase ground fault types of the ultra-high voltage alternating current transmission line according to single-phase ground fault type diagnosis criteria of the ultra-high voltage alternating current transmission line. The method is applicable to single-phase low, medium and high resistance ground fault type diagnosis in the whole fault process of the ultra-high voltage alternating current transmission line, and diagnosis performances are not affected by factors such as transition resistance, load current and system operation modes.

The invention provides a direct-current transmission line protection method and system based on pure current characteristics. The method is characterized in that a current difference value and a current break variable of a line are determined by collecting the current of a direct-current transmission line, and whether a preset protection criterion is established or not is determined according to the current difference value and the current break variable of the line, so that whether the direct-current protection action is outputted or not is determined. The method is advantaged in that the action speed of metallic fault protection can be further increased, the action speed of high-resistance fault protection is greatly improved, protection is reliable and does not act when lightning strokeor abnormal large number occurs, the protection of a non-fault pole line is reliable and does not malfunction under a single-pole grounding fault working condition, and protection performance of thedirect-current transmission line is comprehensively improved.

The invention discloses a line inter-phase fault distance measuring method based on a discrete sampling value. According to the method, effects of inter-phase short circuit fault point voltage instantaneous values on inter-phase fault distance measuring accuracy are considered in an algorithm model, differential discrete processing is performed on differential equations, and fault inter-phase electric quantity sampling values of three adjacent sampling moments are used for calculating fault distances from inter-phase short circuit fault points to electric transmission line protection mounting positions. The method is used for measuring fault distances of inter-phase distance protection, the data amount required to be calculated is small, the calculation speed is fast, the measuring result is not affected by fault positions, transition resistors, system operation modes and load currents, and the measuring accuracy is better than fault distance measuring accuracy of traditional inter-phase distance protection.

The invention discloses a line single-phase earthing fault single-end ranging method realized by utilizing voltage drop imaginary part characteristics. The method utilizes the fault phase negative sequence voltage and the transmission line positive sequence impedance per unit length to calculate the single-phase earthing fault point voltage phase angle, and further calculate an additional fault distance caused by a transition resistance, and the imaginary part of the ratio of the fault phase voltage to the zero sequence compensating current divides the imaginary part of the transmission line positive sequence impedance per unit length and then subtracts the additional fault distance to obtain a fault distance between the transmission line protection mounting part and the single-phase earthing fault point. The method provided by the invention overcomes the impact defects of the transition resistance and load current on single-end fault ranging precision, the ranging precision is high when the transmission line has a single-phase high resistance earthing fault, the ranging principle is simple, the program is easily realized, the fault distance is directly calculated without using a search algorithm, the ranging speed is quick, and the real-time is strong.

The invention relates to a T-connection power grid transient state quantity unit protection method utilizing voltage and current abrupt change quantity wavelet coefficient correlation analysis and belongs to the power system relay protection technical field. The method comprises the following steps that: transient state quantities of three groups of fault voltage and current are obtained through directional elements of R1, R2 and R3 at an M, N and Q end when a single-phase grounding fault occurs on a T-connection power grid; the transient state quantities of the voltage and current 0.5ms after the fault are respectively intercepted, and 8-scale wavelet decomposition is performed on the transient state quantities; wavelet coefficients of the transient state quantities of the voltage and current under the first scale are correspondingly selected so as to be subjected to correlation analysis; and when three groups of correlation coefficients are simultaneously greater than or equal to -1 and are smaller than or equal to -0.8, the fault is determined as an intra-cell fault, otherwise, the fault is determined as an extra-cell fault. As indicated by a large number of simulation experiments, the method is greatly applicable to T-connection power grid AC transmission line protection.

The invention discloses a line interphase fault single-ended distance measurement method based on an interphase fault location factor. The method includes firstly, calculating the ratio of fault impedance, from an electric transmission line protection mounting position to an interphase short-circuit fault point, to line impedance, from the electric transmission line protection mounting position to an electric transmission line protection setting range, to acquire the electric transmission line interphase fault location factor b; selecting a fault location default value as lfault, and sequentially calculating the absolute values of [Zc1th(gamma1lfault) / Zc1th(gamma1lset)]-b of points on an electric transmission line by means of progressive increase of a fixed step length delta l until the total length of the electric transmission line is calculated; selecting the distance between the point with the maximum absolute value of [Zc1th(gamma1lfault) / Zc1th(gamma1lset)]-b on the electric transmission line and the electric transmission line protection mounting position as the fault distance. The method has the advantages that influences of electric transmission line interphase short-circuit fault point voltage, transition resistance and load current on electric transmission line interphase short-circuit fault single-ended distance measurement accuracy are eliminated theoretically, and the method has high distance measurement accuracy and is particularly applicable to interphase short-circuit fault single-ended distance measurement of extra-high-voltage alternating-current electric transmission lines.