2041 results about "Differential protection" patented technology

An apparatus and method compensate for the sensitivity of at least one line current differential element of a first current differential relay providing differential protection for a transmission line of a power system during a single-phase pole-open condition. The apparatus includes a first delta filter configured to remove a first pre-fault current from a first fault current of the transmission line to derive a compensated first current phasor. The apparatus also includes a second delta filter configured to remove a second pre-fault current from a second fault current of the transmission line to derive a compensated second current phasor. The compensated first and second current phasors are provided to the at least one line current differential element to compensate the sensitivity of the at least one line current differential element.

The present invention relates to a centralized and networked protection system and method of regional distribution network, and belongs to the field of electrical system automation and relay protection. The protection system includes at least two centralized protection devices, an intelligent terminal and a communication network module, the centralized protection devices being communication with the intelligent terminal via the communication network module, the intelligent terminal being configured along with switching devices to distribute in each line section, for sampling data, backup protection and executing of tripping and closing commands, the centralized protection devices configured in the monitoring center of the regional distribution network, for generating differential protection elements based on the information sampled by the intelligent terminal and the topologic structure of the regional distribution network; and for determining the region where fault occurs and sending tripping and closing control commands.

The invention relates to a current differential protection method for a smart distribution network, which comprises: mounting current transformers and smart distribution terminals at the positions of all switches in the smart distribution network, wherein each smart terminal serves as an agent, the agents are connected with one another through an optical fiber Ethernet, and the positive directions of all currents is the direction from a system power supply to the end of a circuit; automatically detecting the working state of a communication network through the agents, and determining if to perform current differential protection; when the communication network fails to work normally, applying the conventional three-stage current protection; when the communication network works normally, applying current differential protection and using the current differential protection as main protection; and allowing a local agent to compute a differential current and a braking current according to the local switching current detected by the local agent and downstream switching current transmitted by a downstream agent and determine if the protection is actuated. The overcurrent protection is local backup protection, and the protection of an upstream agent is local remote backup protection.

The disclosed protection method for internal fault of large power transformer comprises: the protector samples the secondary current of current transformers on power transformer sides to obtain current instantaneous value and calculate complex number form of electric values by Fourier algorithm, corrects phase of connection form, and balances amplitude of transformation ratio; then, it calculates the complex number form of negative sequence current according to three-phase ac complex form, and computes negative sequence differential current and break current as the negative sequence differential protection principle to decide asymmetric inside and outside fault and drop out all breakers. This invention also contains exactly the negative sequence differential rate breaking feature and protection criterion, the adjusting means for protection values, the positive sequence current breaking criterion, and the block function for error action protection.

The invention relates to an electric secondary AC circuit detection method which comprises the following steps: before a power plant machine set is started, a low-voltage short-circuit point or a short-circuit bogie is input; three-phase 380 V voltage is added at the high-voltage side of a booster station to form a circuit by means of the impedance of a transformer and a generator; current amplitude and phase are measured through a current detecting apparatus to check polarity and transformation ratio in advance; all current protective directions such as generator differential motion are measured. When a neutral point is not connected, a short-circuit point is made at a high plant transformer low-voltage side, and the three-phase 380 V voltage is added at the neutral point of the generator, thereby realizing overall checkup of a generator AC circuit; then, the three-phase 380 V voltage is converted into one-phase voltage or two-phase voltage to carry out overall checkup of a zero sequence circuit. The detection method can check all CT and PT circuits of a generation-transformer group before power transmission; moreover, all protection directions of the generation-transformer group are checked in advance, thereby saving time and fuel oil along with economical efficiency, environmental protection and safety. The electric secondary AC circuit detection method can check secondary circuits such as the transformer and the bus differential protection of a transformer substation.

A method for fault detection in a power transformer / autotransformer and / or interconnected power lines, which are within the zone protected by the differential protection, and particularly suitable for detecting turn-to-turn faults in power transformer / autotransformer windings. All individual instantaneous phase currents of the protected object are measured, individual phase currents as fundamental frequency phasors are calculated, the contributions of the individual protected object sides negative sequence currents to the total negative sequence differential current are calculated by compensating for the phase shift of an eventual power transformer within the protected zone, the relative positions of the compensated individual sides negative sequence currents in the complex plane are compared, in order to determine whether the source of the negative sequence currents, i.e. the fault position, is within the protected zone or outside of the protected zone, delimited with current transformer locations, the protected object is disconnected if determined that the source of the negative sequence currents is within the protected zone.

An apparatus and method compensate for the sensitivity of at least one line current differential element of a first current differential relay providing differential protection for a transmission line of a power system during a single-phase pole-open condition. The apparatus includes a first delta filter configured to remove a first pre-fault current from a first fault current of the transmission line to derive a compensated first current phasor. The apparatus also includes a second delta filter configured to remove a second pre-fault current from a second fault current of the transmission line to derive a compensated second current phasor. The compensated first and second current phasors are provided to the at least one line current differential element to compensate the sensitivity of the at least one line current differential element.

This invention relates to reclosing method for power transmission line. For joint parallel double circuit type: each circuit being equiped with individual protector, main protection being phase-splitting current differential protection or phase-command longitudinal protection; for various type single circuit fault or overline fault withni a zone, tripping fault being detected, determinnig no serious permanent fault, sequentially reclosing the tripping phases. For double-circuit fault, there must be two different type circuit being of no fault for reclosing, if not, two circuits must be tripped-off. This invention method increases the reclosing rate, together with minimizing the shock to the system after reclosing permanent fault.

The invention provides an identification method for transformer inrush current which belongs to power system main equipment relay protection technology field. The method has characteristics in that the method identifies inrush current and fault current base on waveform correlation degree. By comparison with each sampling point algebraic sum in dynamic differential current short data window, non-saturation region of transformer under inrush current and fault current is searched, two form standard sine waves are constituted of max value and position of sampling data in non-saturation region, then differential current sampling waveform in non-saturation region and two form standard sine waves correlation degrees are calculated respectively, inrush current and fault current are differentiated according with correlation coefficient average. The method can open longitudinal differential protection rapidly when internal fault and no-load closing with fault occur in transformer operation; and can lock longitudinal differential protection reliably when on-load closing occurs inrush current.

The invention discloses a method for current differential protection of a direct current electric transmission line, which comprises the following steps: according to a distributed parameter model of the electric transmission line, using mode transformation in a time domain to transform sampling values of direct current and direct current voltage into a modulus; then using the mode voltage and the current of two ends from two ends of a line respectively to calculate mode current of certain point of the line at each moment; and using the mode current to directly construct a current differential protection criterion, or synthesizing electrode current through electrode mode inverse transformation, and then constructing the current differential protection criterion according to the electrode current. The method can improve the sensitivity and the reliability of direct current line protection, has good controllability and high security, has a complete setting theory, overcomes the defects of the conventional traveling-wave protection as the main protection of a high-voltage direct current line, and requires no recognition of a traveling-wave wave head; besides, the calculation is simple. The method is mainly used for the current differential protection of the direct current electric transmission line in an electric power system, in particular for the protection of an ultra / extra high-voltage direct current electric transmission line.

A differential protection system for power transformers using Rogowski coils as current sensors can support an inrush current detection method based on sensing lows in the derivative of the sensed current. Effective detection of power transformer inrush conditions can enable blocking of a protection relay during inrush where the differential current may exceed a differential threshold value indicative of a fault without the presence of an actual fault. The outputs of the Rogowski coils, being proportional to the first time derivative of the sensed current, may be useful in the inrush detection method. Also, with reduced saturation concerns, the Rogowski coil protection system may employ a single slope response with increased sensitivity. A discrete time sampling technique for identifying low di / dt portions within the sensed current also may be useful in detecting power transformer inrush conditions.

Provided is an apparatus and method for providing to a differential relay an operational vector-group compensation setting pair that automatically provides correction for a phase shift occurring between currents of at least two windings of a power transformer. The method includes calculating a first and second plurality of phasors using secondary currents derived from respective first and second winding of the at least two windings. The method also includes selecting one pair of vector-group compensation settings based on operate current values calculated using different pair combinations of the vector-group compensation settings applied to the first and second plurality of phasors. The method further includes comparing phase angles of like-phase phasors to determine if the phase angles are within a pre-determined angle range, and enabling application of the selected pair of vector-group compensation settings as the operational vector-group compensation setting pair if the phase angles are within the pre-determined angle range.

A method for fault detection in a power transformer / autotransformer and / or interconnected power lines, which are within the zone protected by the differential protection, and particularly suitable for detecting turn-to-turn faults in power transformer / autotransformer windings. All individual instantaneous phase currents of the protected object are measured, individual phase currents as fundamental frequency phasors are calculated, the contributions of the individual protected object sides negative sequence currents to the total negative sequence differential current are calculated by compensating for the phase shift of an eventual power transformer within the protected zone, the relative positions of the compensated individual sides negative sequence currents in the complex plane are compared, in order to determine whether the source of the negative sequence currents, i.e. the fault position, is within the protected zone or outside of the protected zone, delimited with current transformer locations, the protected object is disconnected if determined that the source of the negative sequence currents is within the protected zone.

The invention relates to a high reliable inrush current brake method for a transformer, which comprises the steps of sampling, calculating the three-phase differential current fundamental wave content and the second harmonic content of a current sampling point, setting and calculating a floating threshold, and carrying out differential starting judgment, the judgment of the change characteristics of the fundamental wave content and the judgment of the change characteristics of the ratio between second harmonic content and the fundamental wave content by a discriminant so as to determine reliable locking or immediate differential opening. On the basis of a traditional second harmonic braking principle, the method sets the floating threshold, tracks and masters the change characteristics of the fundamental wave and the second harmonic in a real-time manner, analyzes and judges the operation state of the transformer in time by utilizing the change characteristics of the fundamental wave and the second harmonic, solves the contradiction of the right and fast motion between the inrush current brake and differential protection in the current method and ensures the reliable brake of the transformer under the condition of the only existence of the inrush current and the right and fast motion of the transformer under the situation of any fault in the sample space. Meanwhile, the method reduces the value scope of the brake coefficient of the second harmonic and improves the sensitivity of inrush current brake.

The invention concerns a method of impedance groundfault detection for differential protection of an overhead transmission line in a three-phase high voltage electric power transmission system which comprises many lines (1,12) and many protection relays (2,4), which comprises the following steps: 1) in prefault condition: —measuring the differential current (I); —measuring the phase voltage (II) at the relay location; —measuring the phase current (III) the relay location; —calculating the differential admittance (IV), with the following equation: (formula (V)). With (VI): the positive sequence impedance of the line-protected. 2) In operating condition: —measuring the differential current (VII); —measuring the phase voltage (VIII) at the relay location; —measuring the phase current (IX) at the relay location; calculating the differential admittance (X), with the following equation: (formula (XI)); —detecting a high impedance groundfault detection, if the following formula is verified: (XII) with (XIII); B0=the total line admittance.I_dphpre(I)U_fphpre(II)I_fphpre(III)Y_dpre(IV)Y_dpre=I_dphpreU_fphpre-0.5ZL1I_fphpre(V)ZL1(VI)I_dph(VII)U_jph(VIII)I_jph(IX)Y_d(X)Y_d-I_dphU_jph-0.5ZL1I_jph(XI)abs(Y_dN)>0.75Bd(XII)Y_dR=Y_d-Y_dpre(XIII)

Provided is an apparatus and method for providing differential protection for a phase angle regulating transformer having a load side and a source side in a three-phase power system. The method includes calculating a first positive sequence component and a first negative sequence component associated with incoming secondary currents detected on the source side, calculating a second positive sequence component and a second negative sequence component associated with outgoing secondary currents detected on the load side, applying a phase angle shift to the second positive sequence component and the second negative sequence component to form a compensated positive sequence component and a compensated negative sequence component, respectively, and determining an operate current value and a restraint current value for each of a positive and negative sequence differential element of the differential protection based on the compensated positive sequence component and the compensated negative sequence component.

Provided is an apparatus and method for providing differential protection for a phase angle regulating transformer having a load side and a source side in a three-phase power system. The method includes calculating a first positive sequence component and a first negative sequence component associated with incoming secondary currents detected on the source side, calculating a second positive sequence component and a second negative sequence component associated with outgoing secondary currents detected on the load side, applying a phase angle shift to the second positive sequence component and the second negative sequence component to form a compensated positive sequence component and a compensated negative sequence component, respectively, and determining an operate current value and a restraint current value for each of a positive and negative sequence differential element of the differential protection based on the compensated positive sequence component and the compensated negative sequence component.

The invention provides a method for reducing time limit combination step progression of distribution network relaying protection, comprising the following steps: 1, realizing differential protection (DP) between all incoming switches and all outgoing switches in a distribution switching station or a distribution firewall; and 2.1,, if the DP meets action conditions, tripping off all the incoming switches without time delay; 2.2, if the DP does not meet the action conditions, executing overcurrent criterion on all the outgoing switches: judging whether the overcurrent I is more than set current Iset, namely I is more than Iset; and if the outgoing switches meet the overcurrent criterion at some time, tripping off the outgoing switches. The method is utilized to realize selective actions without time delay for the relaying protection between two-stage panel switches in the distribution switching station (or a distribution firewall), thus reducing the time limit combination step progression of the distribution network relaying protection, and greatly decreasing maintenance workload of relaying protection personnel. The invention also discloses a device for reducing time limit combination step progression of distribution network relaying protection.

A differential protection system and a differential protection method for a flexible DC distribution network line are provided. An FPGA-based protection device sends a sample pulse to a data collector. To achieve synchronized sampling and data window synchronization, line dual-end protection devices are arranged as a reference end and a following end respectively. The following end firstly sends a synchronization request command including a number of a sample and a corresponding time of the sample. The reference end returns information including a sample number and a corresponding sample time of the reference end after receiving the command sent by the following end. After receiving a corresponding data message of the reference end, the following end calculates a communication transmission time delay and a deviation between the sample times of the two sides. Through compensation of the communication transmission time delay and a secondary interpolation sampling synchronization method, synchronized sampling of the following end and the reference end is achieved. Through calculating the differential current of two ends of a direct current line, the method determines whether differential current protection criteria are satisfied and achieves differential protection of the direct current line. The system and the method can ensure correct actions on internal faults and correct non-actions on external faults.

The invention discloses a double loop network-based protection device free of a main in-situ transformer and a protection method. The double loop network-based protection device free of the main in-situ transformer comprises in-situ protection sub-machines, which are arranged at a high-voltage side, a medium-voltage side and a low-voltage side of a transformer respectively; the protection sub-machines are in hand-in-hand connection through double loop networks; each protection sub-machine collects the analogue quantity and the switch quantity of the side in situ, and is in bidirectional communication with the other protection sub-machines through the double loop networks to share data; each protection sub-machine comprises the same main and backup protection-integrated protection module for the transformer; a circuit breaker is arranged between each protection sub-machine and the side of the transformer; and each protection module trips off the corresponding circuit breaker according to the set backup protection action conditions and differential protection action conditions. By the double loop network-based protection device free of the main in-situ transformer and the protection method, the problem that a host of an existing protection device with the main transformer cannot be installed in situ is solved; and furthermore, multiple sets of differential 'conjunction gate' logics are adopted by the protection device, so that the protection reliability is improved.

The invention discloses a power distribution net rack wiring structure which comprises multiple switch stations and substations, wherein each switch station comprises a first section of bus and a second section of bus connected in series through a section switch; each section of bus is connected with an incoming line, multiple outgoing lines and a connection line respectively; two incoming lines of each switch station are connected with different substations respectively; the connection line is arranged between the switch stations; one end of the connection line is connected with the first section of bus of one switch station, and the other end of the connection line is connected with the second section of bus of the other switch station. The power distribution net rack wiring structure disclosed by the invention has flexible operation mode and high reliability; with a centralized power supply mode of the switch stations, the operation and maintenance management is facilitated; the incoming line and connection line of each switch station are configured with optical-fiber longitudinal differential protection, and the section switch and connection switch of the bus of each switch station are configured with spare power automatic switching and expansion spare power automatic switching, so that the fault elimination of the distribution network and the power supply of the non-fault section can be accelerated, the fault-caused power failure time is reduced, the power supply reliability is improved, and the power distribution net rack wiring structure is suitable for the regions with insufficient medium-voltage interval of substations, limited outgoing line corridors, centralized loads and high reliability requirements.

The invention discloses a d-side current phase compensation method for YNd5 transformer longitudinal differential protection. The method is characterized by connecting the high-voltage side TA secondary winding and the low-voltage side TA secondary winding of an YNd5 transformer both in a star connection manner and performing current phase compensation on the d side of the YNd5 transformer. The method has beneficial effects of being a current phase software compensation technology scheme suitable for transformer longitudinal differential protection devices with various voltage classes for YNd5 wiring in a power transmission and distribution network power station, being simple and clear, and being easy to implement.

The invention relates to a pilot channel transmission device, a pilot channel optical fiber differential protective device and a pilot channel optical fiber differential protective method, and belongs to the technical field of relay protection of electric power systems. The pilot channel optical fiber differential protective device comprises a merging unit, a pilot channel transmission device, differential protective devices, a fault wave recording device, an SMV network switch and a GOOSE network switch, wherein the GOOSE network switch is respectively connected with the pilot channel transmission device, the differential protective devices and the fault wave recording device; the merging unit, the differential protective devices, the pilot channel transmission device and the fault wave recording device are connected to the SMV network switch through an optical fiber interface; the pilot channel transmission device realizes the synchronous sampling of a home station and a transformer substation on the opposite side, and outputs sampling values of the transformer substation on the opposite side to the SMV network switch; and data with different formats is transformed by using a converter according to requirements, so that manufacturers of the differential protective devices at both ends of a transmission line do not need to be limited, and the compatibility of the protective devices is improved.

The invention relates to a longitudinal differential protection current phase compensation method for an YNd series transformer. The method is that TA secondary winding of the high-voltage side and TA secondary winding of the low-voltage side of the YNd series transformer are respectively connected through star connection, A phase current, B phase current and C phase current of the TA secondary winding of the Y side of the YNd series transformer are respectively switched in an A phase current loop, a B phase current loop and a C phase current loop of YNd11 or YNd1 transformer differential protection, and phase current of the TA secondary winding of the d side of the transformer is correspondingly switched in a phase current loop of the d side of an YNd11 or YNd1 wiring microcomputer transformer differential protection device when certain phase current of the d side of the transformer is the same as a certain phase current phase of the d side of a YNd11 or YNd1 transformer. The method is simple in principle and convenient to implement, completely conforms to a transformer differential protection current phase compensation principle, and can adapt to unusual YNd series transformer longitudinal differential protection current phase compensation of the transformers of various voltage levels.

The invention relates to a main transformer differential protection CT polarity check method of a pumped storage power station. In the invention, an applied power method is adopted to solve the problem that the main transformer differential, bus differential and high-voltage cable differential protection CT polarity cannot be checked during the inversed electrification of a main transformer before the machine set of the power station is started, thereby the safety and reliability of the system and the inversed electrification of the main transformer are ensured. The method has the advantages that the operation and the using condition are simple, the used test instrument equipment can be used repeatedly, the water debugging straight-line period of the machine set is not occupied, the temporary high-voltage cable investment is saved, and the commissioning cost is reduced; therefore, the method has favorable popularization and application prospect.

Provided is an apparatus and method for providing to a differential relay an operational vector-group compensation setting pair that automatically provides correction for a phase shift occurring between currents of at least two windings of a power transformer. The method includes calculating a first and second plurality of phasors using secondary currents derived from respective first and second winding of the at least two windings. The method also includes selecting one pair of vector-group compensation settings based on operate current values calculated using different pair combinations of the vector-group compensation settings applied to the first and second plurality of phasors. The method further includes comparing phase angles of like-phase phasors to determine if the phase angles are within a pre-determined angle range, and enabling application of the selected pair of vector-group compensation settings as the operational vector-group compensation setting pair if the phase angles are within the pre-determined angle range.

The invention provides a transformer excitation inrush current and fault differential current recognition method based on a Hausdorff distance algorithm. The transformer excitation inrush current and fault differential current recognition method comprises the steps of: acquiring secondary currents of current transformers at two differential protection sides of a transformer on each cyclic wave N point, and form a differential current signal sequence I; judging whether a value of the differential current signal sequence I exceeds a setting valve of a differential protection starting component, and starting a criterion disclosed by the invention for distinguishing a fault differential current and an excitation inrush current if the value exceeds the setting value differential protection starting component; judging and acquiring an extreme value of the differential current signal sequence I by adopting a 1 / 4 cyclic wave data window, regarding a differential sequence A after per-unit treatment as an edge feature point of a Hausdorff distance algorithm object graph, regarding a standard sine sequence B with amplitude being 1 as an edge feature point of a Hausdorff distance algorithm template graph, comparing an Hi value with a set Hausdorff distance threshold value Hset, and conducting protection action if the Hi value is less than the threshold value; and blocking protection if the Hi value is greater than the threshold value. The transformer excitation inrush current and fault differential current recognition method is used for directly judging difference of waveform pattern overall features of inrush currents including symmetric inrush currents, and ensures correct action of transformer differential protection.

A synchronization method for current differential protection comprises: selecting a point on the transmission line protected by the current differential protection; measuring the current and the voltage of each of the terminals of said transmission line; calculating the compensating voltage at the selected point respectively according to the measured current and the voltage of the each terminal; detecting and calculating the synchronization error by comparing all the compensating voltages.

This invention concerns the relaying protection field of the power transmission line, especially concerned with the occasion of electric current differential protection and phase differential protection proceeding in the extra-high voltage and ultra-high voltage long distance ling. In order to solve the problem of which the traditional electric current differential protection and phase differential protection is influenced largely by distributed capacitance's current, thereby to improve the sensitivity of relaying protection, safety and reliability of the operation, the technique plan adopted by this invention is: according to a transmission line model formula, calculate a side of the line current moment flow, get calculated value, then using a filtering algorithm, filter the current actual value and calculate value, get the fundamental wave vector separately.

The invention discloses a traveling-wave differential protection method suitable for a series capacitor compensation circuit. The method comprises the steps: 1) current calculation under a mold domain, calculating mold currents im<x> and in<x> flowing into a series capacitor device from onside and offside; 2) establishment of differential equation; 3) resolution of differential currents, utilizingthe reverse transformation of phase molds to solve vectors icd<phi> of the differential currents of each fault phase and each non-fault phase; 4) action judgment of a differential relay: utilizing the fault-phase action amount as braking, and adding an appropriate fixing threshold. The invention can effectively solve the effect of capacitor current on differential protection of long-distance transmission lines, can be well suitable for the series capacitor compensation circuit, and enhances the sensitivity of differential protection.