A relay protection system and method suitable for extending T zone

Abstract

The present invention discloses a relay protection system and method suitable for lengthening T zone, the system includes a main machine and several sub-machines arranged in the lengthened T zone, the main machine and the several sub-machines are connected by optical fiber, and the internal time is synchronized; the main machine is used to perform relay protection logic discrimination of the lengthened T zone based on the data collected by each sub-machine, and issue a protection trip command to the corresponding sub-machine, wherein the relay protection includes ratio braking differential protection, overcurrent protection, circuit breaker failure joint trip protection, CT disconnection discrimination, remote transmission, and CT saturation discrimination; the sub-machine is used for the collection and uploading of analog and switch quantity data, receiving and executing the protection trip command and removing the fault, and the sub-machines have the signal and joint trip mutual remote transmission function. The present invention does not rely on external clocks and long cable secondary current and switch quantity transmission, and can reach up to 32 terminals, solving the existing T zone protection technology problems.

Description

Technical Field

[0001] The invention belongs to the technical field of relay protection of electric power systems, and relates to a relay protection system and method suitable for lengthening a T zone. Background Art

[0002] With the development of the power grid, large thermal power plants, hydropower plants, nuclear power plants and pumped storage power stations at the source end are generally connected to the main grid through the T zone after boosting to a voltage level of 500kV or higher. Due to the constraints of geographical location and renovation and expansion conditions, the busbars and host equipment of the booster station are arranged at a long distance, resulting in a long-distance extended T zone that is different from conventional power stations. The branch lines of the access system are much longer than 300 meters, or even several kilometers. For example, in the typical 500kV voltage level 3 / 2 wiring, the unit is connected to the high-voltage system through the combined unit wiring; similarly, the installation location of the host equipment is far away, the lead distance on the high-voltage side is long, and one side of the unit has its own T zone, resulting in an enhanced version of the double T connection area; in addition, there are also cases where the internal bridge, angle electrical wiring or connection through leads are used in situations where the distance between the main equipment and the system power grid is far away, and the interconnection wiring area will also cover a long distance and a large area.

[0003] The increase in the length of the secondary circuit cable of the transformer used for conventional T-zone protection can easily cause attenuation of the secondary transmission signal, which may cause distortion of the analog quantity obtained by the protection device; the increase in the length of the cable used to drive the remote switch to trip may cause the risk of instability in the transmission signal due to the influence of the distributed capacitance along the cable during long-distance transmission; moreover, systems with voltage levels of 500kV or higher have higher requirements on the protection's anti-CT saturation capability and the timeliness of the action output. Some extended T-zones have as many as 6 terminals or more. The conventional three-terminal T-zone protection solution cannot meet the relay protection requirements of the extended T-zone in terms of the number of ports, current cable access length, action speed and data acquisition. Summary of the invention

[0004] In order to solve the deficiencies in the prior art, the present invention provides a relay protection system and method suitable for extending the T zone. The master and slave machines are connected by optical fiber and internally synchronized. The master machine completes relay protection functions and logic discrimination such as differential protection, overcurrent protection, and failure linkage. The slave machine is responsible for analog and switch quantity data collection, execution of protection tripping and fault removal. The slave machines have the function of mutual remote transmission of signals and linkage. The protection differential protection adopts a busbar protection ratio braking scheme, with fast action speed and strong anti-CT saturation ability. The present invention does not rely on external clocks and long cable secondary current and switch quantity transmission, and can reach up to 32 terminals, solving the technical problems of existing T zone protection.

[0005] The present invention adopts the following technical solution.

[0006] A relay protection system suitable for an extended T zone, comprising a main unit and a plurality of sub-units arranged in the extended T zone, wherein the extended T zone comprises a bus side and a component or line side, and the interconnection wiring area of ​​the bus side and the component or line side is in a "T"-shaped structure;

[0007] The host is arranged at a half circuit breaker terminal on the bus side, and a side switch CT and a middle switch CT are respectively arranged on both sides of the half circuit breaker terminal;

[0008] The plurality of sub-machines include sub-machine 1 and sub-machine 2 arranged according to the side switch CT and the middle switch CT respectively, and n-2 sub-machines arranged according to the branch CTs on the component or line side, where n is less than or equal to 32;

[0009] The host and several slaves are connected via optical fiber and synchronized internally;

[0010] The host is used to perform extended T-zone relay protection logic judgment based on the data collected by each slave, and issue a protection trip command to the corresponding slave, wherein the relay protection includes ratio brake differential protection, overcurrent protection, circuit breaker failure trip protection, CT disconnection judgment, remote transmission, and CT saturation judgment;

[0011] The sub-machine is used for collecting and uploading analog and switch quantity data, receiving and executing protection tripping commands and clearing faults, and the sub-machines have the function of mutual remote transmission of signals and joint tripping.

[0012] Preferably, the host and the slave are configured as dual CPU plug-ins, the dual CPU of the host is point-to-point connected to the dual CPU of each slave respectively; and the host and the slave use IEEE1588 for internal time synchronization.

[0013] Preferably, the relay protection system dynamically tracks the operating conditions on site by introducing the primary isolation switch state, specifically:

[0014] There is no isolating switch in the interval on the busbar side, and the current value is fixedly included in the differential and braking currents;

[0015] The outgoing line interval of the branch is set with the position of the isolation switch, and the state of the isolation switch G1 determines whether the current value is included in the small differential current, and the small differential current and the braking current do not take into account the outgoing line interval where the isolation switch G1 is in the split position.

[0016] Preferably, the sub-machines arranged according to the branch CT are equipped with the outgoing line interval "isolation switch position TWJ" input and "isolation switch strong separation" hard pressure plate to identify abnormal isolation switch position, specifically:

[0017] When the "isolation switch position TWJ" input state is inconsistent with the "isolation switch forced separation" hard pressure plate state, or when the "isolation switch position TWJ" input state is 1 and there is current in the outgoing line interval, it means that the isolation switch position is abnormal, and the switch position abnormal alarm is issued;

[0018] When the knife switch position is abnormal, the knife switch position status takes the state of the isolation knife switch strong separation hard pressure plate.

[0019] Preferably, the action equation of the ratio braking differential protection is:

[0020]

[0021]

[0022] In the formula, I i is the branch current of the i-th branch in zone T;

[0023] n is the total number of branches in the T zone;

[0024] I d0 is the differential action current threshold;

[0025] K is the braking coefficient.

[0026] Preferably, the action equation of the overcurrent protection is:

[0027]

[0028]

[0029] T>T SETⅠ

[0030] T>T SETⅡ

[0031]

[0032] In the formula, I t.φ.max It is the maximum phase current of the CT on the component or line side;

[0033] I gldzⅠ ,I gldzⅡ They are respectively the current setting values ​​of stage I and stage II of overcurrent protection;

[0034] T SETⅠ / T SETⅡ They are respectively the time setting values ​​of stage I and stage II of overcurrent protection;

[0035] T is the overcurrent protection time;

[0036] It is the phase current after the branch current with side switch CT and middle switch CT on the bus side is converted to the component or line side;

[0037] is the component or line side current.

[0038] Preferably, the circuit breaker failure joint trip protection means that when the host determines that the circuit breaker in the T zone fails, the circuit breaker connected in the T zone is tripped, specifically:

[0039] When the two failure start inputs provided by the external failure start device to the slave are detected at the same time, the current discrimination element is detected to see if it is open:

[0040] If it is open, the side switch CT failure interlocking protection starts, and the side switch connected to the busbar is tripped after a delay;

[0041] The current discrimination elements include phase current, zero-sequence current and negative-sequence current, and the “OR” logic of the three is open;

[0042] The phase current is opened by the "AND" logic of the phase current steady-state quantity and the sudden change quantity; the sudden change quantity of the phase current is the phase current of any phase of the branch, and it is opened when it is greater than the sudden change quantity threshold value, and it is fixed and widened for 15 seconds after opening; the steady-state quantity of the phase current is the largest phase current of all branches, and it is opened when it is greater than the steady-state quantity threshold value;

[0043] The zero-sequence current and negative-sequence current are both steady-state quantity criteria, and the maximum of the zero-sequence current and negative-sequence current of all branches is taken respectively, and the circuit is opened when it is greater than the set threshold value.

[0044] Preferably, the CT disconnection judgment is divided into CT disconnection judgment based on the alarm section differential current exceeding the limit value and based on the locking section differential current exceeding the limit value, wherein the alarm section differential current exceeding the limit value is lower than the locking section differential current exceeding the limit value; specifically:

[0045] When the differential current in the T zone exceeds the differential current over-limit value of the alarm section but does not exceed the differential current over-limit value of the locking section, an alarm signal is issued after a fixed delay;

[0046] When the differential current exceeds the differential current over-limit value of the locking section, an alarm signal is issued after a fixed delay, and the differential protection is locked according to the phase.

[0047] Preferably, the remote transmission refers to multiplexing the communication network link between the master and slave machines to bidirectionally transmit the remote jump command or the information of the required switch quantity.

[0048] Preferably, the transient CT saturation judgment logic is:

[0049] Within the first time threshold T1 of ΔIf>Id0, the ratio braking condition Id>K*If is not satisfied. After ΔIf>Id0 for a time greater than T1, the ratio braking condition is satisfied, indicating transient CT saturation;

[0050] The steady-state CT saturation discrimination logic is as follows:

[0051] After ΔIf > Id0 reaches the second time threshold T2, within the third time threshold T3 when ΔDId < KS * ΔDIf, if the ratio restraint condition Id > K * If is not satisfied and the time of ΔDId < KS * ΔDIf is greater than T3, and then the ratio restraint condition is satisfied, it indicates steady-state CT saturation;

[0052] Among them, ΔIf is the sudden change of the braking current, I d is the differential current, I f is the braking current, K is the braking coefficient of the ratio restraint differential protection, Id0 is the differential threshold, ΔDI d is the differential current difference value, ΔDI f is the braking current difference value, and Ks is the current difference ratio restraint coefficient.

[0053] A relay protection method applicable to an extended T zone includes:

[0054] Each slave unit collects analog and switch data of its corresponding branch and uploads them to the master unit;

[0055] The master unit performs relay protection logic discrimination for the extended T zone based on the data collected by each slave unit and issues a protection trip command to the corresponding slave unit, where the relay protection includes ratio restraint differential protection, overcurrent protection, breaker failure tripping protection, CT disconnection discrimination, remote transmission, and CT saturation discrimination;

[0056] After each slave unit receives the protection trip command, it executes the protection trip command to cut off the fault.

[0057] The beneficial effects of the present invention are as follows compared with the prior art:

[0058] The present invention adopts a split design of the master unit and slave units. The master and slave units are connected by a star network and fiber optic point-to-point. The master unit is shared, and the slave units are configured according to the breaker CT. The master unit supports the access of up to 32 slave units at most. Among them, the master unit performs relay protection logic discrimination for the extended T zone based on the data collected by each slave unit and issues a protection trip command to the corresponding slave unit. The relay protection includes ratio restraint differential protection, overcurrent protection, breaker failure tripping protection, CT disconnection discrimination, remote transmission, and CT saturation discrimination; the slave units collect and upload analog and switch data, receive and execute the protection trip command and cut off the fault, and there is a function of mutual remote transmission of signals and tripping between slave units.

[0059] The present invention solves the interference problem caused by long cables by using optical fiber communication between master and slave units, and can use multi-terminal T zones, and adopts ratio differential protection similar to busbar protection, which has fast action speed and strong anti-CT saturation ability, and increases the stability of the power system; the remote transmission function between slave units of the present invention solves the weak link that the existing remote transmission function cannot be operated in the reverse direction and cannot be multi-to-multi; the adaptive overcurrent protection of the present invention can prevent the circuit breaker from losing protection in the dead zone; the failure linkage function of the present invention can prevent external faults in the T zone, and the fault range caused by circuit breaker failure is increased; the present invention thoroughly solves the shortcomings of the existing T zone protection, shortens the T zone fault removal time, and improves the reliability of T zone protection. The differential current calculation of the relay protection system of the present invention is changed from static calculation to dynamic tracking. The present invention can accurately distinguish steady-state CT saturation and transient CT saturation, and the action outlet of the protection differential current can prevent protection malfunction through CT saturation judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 It is a master-slave device layout diagram of the present invention;

[0061] Figure 2 It is a communication diagram between the main and sub machine chassis of the present invention;

[0062] Figure 3 : is a diagram for distinguishing abnormal position of an isolation switch in an embodiment of the present invention;

[0063] Figure 4 is the T-zone protection range corresponding to different isolation switch positions in the embodiment of the present invention;

[0064] Figure 5 It is the isolation switch position abnormality judgment logic in the embodiment of the present invention;

[0065] Figure 6 It is the CT saturation judgment logic in the embodiment of the present invention. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0067] Embodiment 1 of the present invention provides a relay protection system suitable for an extended T zone. In a preferred but non-limiting embodiment of the present invention, the relay protection system includes a main unit and several slave units arranged in an extended (more than 300 m) T zone, wherein the extended T zone includes a bus side and a component or line side, and the interconnection wiring area of ​​the bus side and the component or line side is in a "T"-shaped structure;

[0068] The host is arranged at a half circuit breaker terminal on the bus side, and a side switch CT and a middle switch CT are respectively arranged on both sides of the half circuit breaker terminal;

[0069] The plurality of sub-machines include sub-machine 1 and sub-machine 2 arranged according to the side switch CT and the middle switch CT respectively, and n-2 sub-machines arranged according to the branch CTs on the component or line side, where n is less than or equal to 32;

[0070] The host and several slaves are connected via optical fiber and synchronized internally;

[0071] The host is used to perform extended T-zone relay protection logic judgment based on the data collected by each slave, and issue a protection trip command to the corresponding slave, wherein the relay protection includes ratio brake differential protection, overcurrent protection, circuit breaker failure joint trip protection, CT disconnection judgment, remote transmission, and CT saturation judgment. The host also communicates with the station control layer to realize the display and processing of information uploaded by the slave;

[0072] The sub-machine is used to collect analog quantity (CT current) and switch quantity (isolation switch, remote trip, remote transmission) data and convert them into agreed format data before uploading to the host, receiving and executing protection tripping commands and removing faults, and the sub-machines have signal and joint tripping mutual remote transmission functions, including electric quantity, non-electric quantity, shutdown, failure start and other signals. The sub-machine provides the required conventional relay output contacts, accesses the operation box control circuit tripping, and is compatible with the LOCKOUT relay function, which is used to access the direct tripping circuit and send the necessary tripping alarm information to the host.

[0073] In specific implementation, the master and slave devices are arranged as follows: Figure 1 As shown, Figure 1 In the system, the slaves are arranged according to CT, and the host is generally arranged at a semi-connected terminal. Slave 1 and slave 2 collect data from a semi-connected side switch CT and a middle switch CT respectively, and the remaining slaves are set according to the T zone branches to collect data from CT and isolation switches; the host determines the logical function, and the slave executes data collection and tripping commands.

[0074] The physical connection method of the master and slave machines is as follows Figure 2 As shown, Figure 2In the system, the master and slave are configured with dual CPU plug-ins. The CPU1 and CPU2 of the master are point-to-point connected with the CPU1 and CPU2 of each slave, respectively, to ensure the independence and reliability of the sampling and tripping of the two CPUs. Damage to any CPU will not cause malfunction of the protection.

[0075] The host chassis includes CPU plug-in, input plug-in, output plug-in, power plug-in, management plug-in, etc. The slave chassis includes CPU plug-in, AC plug-in, input plug-in, output plug-in, LOCKOUT plug-in, power plug-in, etc. The host management plug-in is equipped with a time synchronization function and supports the GMRP network multicast protocol. The device provides hard pulse time synchronization (including IRIG-B time synchronization, second pulse time synchronization), network time synchronization and IEEE1588 time synchronization. The master and slave adopt IEEE1588 and are not affected by external clocks. Correspondingly, the hardware system of the master and slave machines includes a power module, a communication and management module, a processor module, an input module, and an output module; the communication and management module, the processor, the input module and the output module realize information exchange through a bus; the processor module includes a first processor CPU1, a second processor CPU2, and an AC converter; the AC converter converts the AC current and AC voltage and inputs them into the first processor and the second processor respectively through an analog-to-digital converter; the input module includes an input plug-in, which receives a hard pressure plate signal and an external input signal; the output module includes multiple output plug-ins, which send a tripping and closing signal; the communication and management module has a built-in MASTER plug-in, and the communication and management module is also connected to the human-machine interface; the power module provides power to the communication and management module, the processor module, the input module and the output module.

[0076] The differential current calculation of the relay protection system in the T zone system is changed from static calculation to dynamic tracking. The operating conditions on site are dynamically tracked by introducing the state of a primary isolating switch. Taking the three-side T zone as an example, the software can select up to 32 branches. The exited sub-machine is not included in the differential and braking current; there is no isolating switch on the bus side, and the current value is fixedly included in the differential and braking current; the state of the isolating switch G1 determines whether the current value is included in the small differential current in the outgoing line interval, and the small differential current and braking current are not included in the outgoing line interval where the isolating switch G1 is in the split position.

[0077] The T zone protection range corresponding to different isolation switch positions is as follows Figure 4 As shown. Since the isolation knife switch position may be abnormal, the "isolation knife switch position TWJ" input and "isolation knife switch strong separation" hard pressure plate can be configured on the slave machine to solve the problem. The specific solution is as follows:

[0078] The "isolation knife switch position TWJ" input represents the state of the isolation knife switch position, that is, when the knife switch is closed, the isolation knife switch position TWJ contact is disconnected, and when the knife switch is disconnected, the isolation knife switch position TWJ contact is closed.

[0079] In order to ensure the correct activation and deactivation of the isolating knife switch and prohibit the activation and deactivation of the knife switch under power, the device is equipped with a "forced deactivation of the isolating knife switch" hard pressure plate. The operating personnel must activate and deactivate the hard pressure plate before isolating the isolating knife switch.

[0080] There is no isolation switch position on the busbar side, so there is no need to put the "isolation switch position TWJ" into operation and the "isolation switch forced separation" hard pressure plate into operation. The busbar access is handled according to the default settings.

[0081] When the outgoing line interval is put into the isolation knife switch position, there is no need to put in the "isolation knife switch position TWJ" and the "isolation knife switch forced separation" hard pressure plate. When the isolation knife switch position is exited, both the "isolation knife switch position TWJ" and the "isolation knife switch forced separation" hard pressure plate need to be put into operation.

[0082] like Figure 4 As shown in the figure, the extended T-zone protection is equipped with isolation switch position abnormality judgment logic for the outgoing line interval with isolation switch position:

[0083] (1) The opening state of the isolation knife switch position TWJ of the corresponding interval is inconsistent with the state of the isolation knife switch hard pressure plate:

[0084] When the isolation switch position TWJ is turned on to 0 and the isolation switch hard pressure plate is put into operation, the device will alarm that the switch position is abnormal;

[0085] When the isolation switch position TWJ is opened to 1 and the isolation switch hard pressure plate is withdrawn, the device will alarm that the switch position is abnormal.

[0086] (2) When the isolation switch position TWJ is turned on to 1 and there is current in the outgoing line interval, the device will alarm that the switch position is abnormal.

[0087] When the knife gate position is abnormal, the knife gate position status takes the status of the isolation knife gate's forced separation hard pressure plate, that is, when the isolation knife gate's forced separation hard pressure plate is put into operation, the knife gate status is judged to be open (that is, the G1 knife gate status is 0), and when the isolation knife gate's forced separation hard pressure plate is withdrawn, the knife gate status is judged to be closed (that is, the G1 knife gate status is 1).

[0088] In the relay protection system, the host is used to perform extended T-zone relay protection logic judgment based on the data collected by each slave, and issue a protection trip command to the corresponding slave, wherein the relay protection includes ratio brake differential protection, overcurrent protection, circuit breaker failure trip protection, CT disconnection judgment, remote transmission, and CT saturation judgment, as follows:

[0089] (1) The following relationship is used to determine the action of the T-zone ratio braking differential protection function:

[0090]

[0091]

[0092] In the formula,

[0093] I i is the branch current of the ith subunit branch;

[0094] n is the total number of subunit branches in the T region;

[0095] I d0 is the differential action current threshold, I d0 The value range is 0.05 to 20I n , I n is the secondary rated current value of the current transformer;

[0096] K is the braking coefficient, and its value range is 0.2 to 0.9.

[0097] (2) Each slave unit bay is equipped with two sections of overcurrent protection. The start and trip of overcurrent protection need to be coordinated with differential protection. Take the three-side T zone as an example:

[0098] When the disconnector G1 of the outgoing line is disconnected, the three-side ratio-braked current differential protection is automatically converted to the two-side ratio-braked current differential protection, and the T zone outgoing line is no longer protected. At the same time, the two-stage overcurrent protection on the outgoing line side is opened as outgoing line protection. When an outgoing line fault occurs, the two-stage overcurrent protection is activated and sends a remote trip signal to the opposite side.

[0099] The overcurrent protection has two stages, and the action equation is:

[0100]

[0101]

[0102] T>T SETⅠ

[0103] T>T SETⅡ

[0104]

[0105] In the formula, I t.φ.max is the maximum phase current of the CT on the component or line side;

[0106] I gldzⅠ ,I gldzⅡ They are respectively the current setting values ​​of stage I and stage II of overcurrent protection;

[0107] T SETⅠ / T SETⅡ They are respectively the time setting values ​​of stage I and stage II of overcurrent protection;

[0108] T is the overcurrent protection time;

[0109] It is the phase current after the branch current with side switch CT and middle switch CT on the bus side is converted to the component or line side;

[0110] It is the component or line side current, which consists of three phases A, B and C respectively.

[0111] Overcurrent protection stage I current setting range: 0.000A~20(In)A;

[0112] Overcurrent protection stage II current setting range: 0.000A~20(In)A;

[0113] Overcurrent protection stage I time setting range: 0.01s~10.00s;

[0114] Overcurrent protection II stage time setting range: 0.01s~10.00s.

[0115] (3) Circuit breaker failure interlocking protection, that is, failure via bus differential tripping protection is set to realize the tripping of the side circuit breaker connected to the bus when the side circuit breaker of a half-circuit breaker connection system fails. The external failure starting device of each branch provides two nodes to the bus protection device. When the device detects the two failure interlocking inputs of branch X at the same time and no failure input abnormal alarm has appeared, it checks whether the current discrimination element of branch X is open. If it is open, the failure via bus differential tripping protection is initiated, and the side circuit breaker connected to the bus is tripped after a 50ms delay. Whether the side circuit breaker failure occurs is mainly determined by the breaker control unit. The current discrimination element of the failure via bus differential tripping protection of this device is to prevent the failure interlocking input of the device itself from making mistakes.

[0116] The current discrimination elements include phase current, zero-sequence current and negative-sequence current, and the "OR" logic of the three is open.

[0117] The phase current adopts the "AND" logic opening of the phase current steady-state quantity and the sudden change quantity.

[0118] When the phase current mutation fails, the judgment begins as soon as the bus differential trip protection control word and pressure plate are put into operation. If the phase current of any phase of the branch is greater than the mutation threshold value of 0.06In, it will be opened. After opening, it will be fixed and widened for 15s.

[0119] The steady-state phase current is the largest phase current among all branches, and it is opened when it is greater than the threshold value 0.08In.

[0120] Zero-sequence current and negative-sequence current are both steady-state quantity criteria. The maximum of the zero-sequence current and negative-sequence current of all branches is taken respectively, and the circuit is opened when it is greater than the threshold value 0.06In.

[0121] If the failure interlock input persists for 10 seconds, it will alarm the failure input abnormality and lock the failure bus differential tripping protection function.

[0122] (4) When the differential protection function is activated, the device performs CT disconnection detection without considering three-phase CT disconnection.

[0123] The CT disconnection judgment of the device is divided into two stages: the alarm stage and the locking stage, in which the alarm stage, i.e. the differential current exceeding the limit value, is lower than the differential current exceeding the limit value of the locking stage.

[0124] Both the alarm section and the locking section send out alarm signals after a fixed delay of 10s.

[0125] When the CT line break blocking conditions are met, the device executes phase-by-phase blocking differential protection, and automatically releases the blocking when the CT line break blocking conditions disappear.

[0126] CT disconnection alarm setting value (differential current over-limit value) setting range: 0.000A ~ 20 (In) A; recommended setting range: 0.06In ~ 0.2In;

[0127] CT line break blocking value setting range: 0.000A~20(In)A; recommended setting range: 0.06In~0.2In;

[0128] (5) The remote transmission function can be used for applications such as tripping the circuit breaker switch at the substation, starting the circuit breaker failure of the side and middle switch, tripping the generator and transformer group, and tripping the three-phase inconsistency of the side and middle switch. This function reuses the communication network link between the master and slave machines, and bidirectionally transmits the information of remote tripping commands or required auxiliary switch quantities such as power, non-power, shutdown, failure start, etc., to reduce the risk of long cable switch quantity transmission. The setting range of the remote transmission export time setting value is: 0s~10.00s.

[0129] (6) To prevent the busbar protection from malfunctioning due to the differential current formed by severe CT saturation when an out-of-zone fault occurs near the busbar, the host is equipped with a CT saturation detection component to perform CT saturation judgment, which is divided into steady-state CT saturation judgment and transient CT saturation judgment.

[0130] like Figure 6 As shown, the transient CT saturation judgment logic is:

[0131] Within the first time threshold T1 of ΔIf>Id0, the ratio braking condition Id>K*If is not satisfied. After ΔIf>Id0 for a time greater than T1, the ratio braking condition is satisfied, indicating transient CT saturation;

[0132] The steady-state CT saturation judgment logic is:

[0133] After ΔIf>Id0 reaches the second time threshold T2, within the third time threshold T3 when ΔDId<KS*ΔDIf, if the ratio restraint condition Id>K*If is not satisfied and the time when ΔDId<KS*ΔDIf is greater than T3, and the ratio restraint condition is satisfied, it indicates steady-state CT saturation.

[0134] Among them, ΔIf is the sudden change in braking current, I d is the differential current, I f is the braking current, K is the braking coefficient of ratio restraint differential protection (generally 0.3 - 0.8), Id0 is the differential threshold, ΔDI d is the differential current difference value, ΔDI f is the braking current difference value (generally 0.3 - 0.8), Ks is the current difference ratio restraint coefficient, generally 0.2.

[0135] The T area is a current node. Under the external fault condition at time t, any T area system can be simplified to two currents, the inflow and outflow currents i1(t) and i2(t), which can be expressed as

[0136]

[0137] Among them, φ is a constant related to the CT time; ω = 2πf, f is the frequency of the alternating current;

[0138] Ts and Tp are the primary and secondary time constants of the system respectively, N is the sampling frequency, θ is the initial fault angle, is the angle related to the CT time constant, ω = 2πf, f is the frequency of the alternating current.

[0139]

[0140]

[0141] I max is the maximum secondary current at the fault moment.

[0142] Assume T is the sampling time interval, let t = nT, then the digital formula (1) according to the sampling value is formula (2):

[0143]

[0144] The differential current I d and the braking current I f for internal faults are i1(n) and |i1(n)|. In the case of external faults and without CT errors, the differential is zero and the braking current is twice |i1(n)|.

[0145] For internal faults, the differential current difference value is the differential current at the current point minus the differential current at the previous point:

[0146]

[0147] Where n is the nth sampling point.

[0148] When there is an out-of-zone fault, considering a 10% CT error, the differential current is twice the CT error, that is, 0.2 times the differential value, and the differential value is:

[0149]

[0150] When there is an out-of-zone fault, the differential value of the braking current is:

[0151]

[0152] The braking current mutation is:

[0153] ΔI f =|I fx -I dx-T |

[0154] I fx are the braking current of the current cycle, I fx-T are the braking currents of the previous cycle respectively, and T is the sampling period.

[0155] Although CT saturation of out-of-zone faults generates differential current, even in the most serious CT saturation, there is still a linear transition zone at the current zero point and the initial stage of the fault. The differential current is zero in this transition zone, and differential current will be generated after passing this zone. The CT saturation detection component uses this feature to form several parallel CT saturation criteria by real-time processing of various variable relationships in the linear transition zone, including differential current, braking current mutation, differential current change rate, braking current change rate, etc., and assigns different synchronization factors according to the characteristics of different criteria. The relationship between the synchronization factor and the time variable is used to accurately identify the moment when CT saturation occurs, and the harmonic analysis of the differential current harmonic quantity makes the CT saturation detection component have a strong ability to resist CT saturation and can identify 2ms CT saturation.

[0156] CT saturation outside the zone can also be identified through waveform recognition technology. For example, when there is a discontinuity angle in the differential current waveform, it means that the CT outside the fault zone in the bus zone is saturated.

[0157] For faults outside the saturated phase area and inside the area, waveform recognition technology is used to quickly cut off the fault. When the differential current waveform has no discontinuity angle, it indicates a fault inside the busbar area.

[0158] Embodiment 2 of the present invention provides a relay protection method suitable for extending the T zone, comprising:

[0159] Each slave collects analog and switch data of the branch where it is located and uploads it to the host;

[0160] The host computer performs extended T-zone relay protection logic judgment based on the data collected by each slave computer, and sends a protection trip command to the corresponding slave computer. The relay protection includes ratio brake differential protection, overcurrent protection, circuit breaker failure trip protection, CT disconnection judgment, remote transmission, and CT saturation judgment.

[0161] After receiving the protection tripping command, each slave executes the protection tripping command and clears the fault.

[0162] The beneficial effects of the present invention are as follows:

[0163] The present invention adopts a split design of a host and a slave, a star network and optical fiber point-to-point connection are adopted between the host and the slave, the host is shared, and the slave is configured according to the corresponding configuration of the circuit breaker CT. The host supports the access of 32 slaves at most, wherein the host performs a logic judgment of the extended T-zone relay protection based on the data collected by each slave, and sends a protection trip command to the corresponding slave, and the relay protection includes ratio braking differential protection, overcurrent protection, circuit breaker failure joint trip protection, CT disconnection judgment, remote transmission, and CT saturation judgment; the slave collects and uploads analog and switch data, receives and executes the protection trip command and cuts off the fault, and the slaves have the function of mutual remote transmission of signals and joint tripping.

[0164] The present invention solves the interference problem caused by long cables by using optical fiber communication between master and slave machines, and can use multi-terminal T zones. It adopts ratio differential protection similar to busbar protection, has fast action speed and strong anti-CT saturation capability, and increases the stability of the power system. The remote transmission function between slave machines of the present invention solves the weak links that the existing remote transmission function cannot be operated in the reverse direction and cannot be multi-to-multi. The adaptive overcurrent protection of the present invention can prevent the circuit breaker from losing protection in the dead zone. The failure linkage function of the present invention can prevent external faults in the T zone, and the fault range caused by the failure of the circuit breaker is increased. The present invention thoroughly solves the shortcomings of the existing T zone protection, shortens the removal time of the T zone fault, and improves the reliability of the T zone protection.

[0165] The present disclosure may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0166] A computer-readable storage medium may be a tangible device that can hold and store instructions used by an instruction execution device. A computer-readable storage medium may be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media (a non-exhaustive list) include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, such as a punch card or a raised structure in a groove on which instructions are stored, and any suitable combination of the foregoing. As used herein, a computer-readable storage medium is not to be interpreted as a transient signal per se, such as a radio wave or other freely propagating electromagnetic wave, an electromagnetic wave propagating through a waveguide or other transmission medium (e.g., a light pulse through a fiber optic cable), or an electrical signal transmitted through a wire.

[0167] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, optical fiber transmissions, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions for storage in the computer-readable storage medium in each computing / processing device.

[0168] The computer program instructions for performing the operation of the present disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages, such as Smalltalk, C++, etc., and conventional procedural programming languages, such as "C" language or similar programming languages. Computer-readable program instructions may be executed completely on a user's computer, partially on a user's computer, as an independent software package, partially on a user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), may be customized by utilizing the state information of the computer-readable program instructions, and the electronic circuit may execute the computer-readable program instructions, thereby realizing various aspects of the present disclosure.

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A relay protection system applicable to an extended T zone, comprising a host and several slave machines arranged in the extended T zone. The extended T zone includes a bus side and an element or line side, and the interconnection wiring area of the bus side and the element or line side has a "T" - shaped structure. It is characterized in that: The host is arranged at one - and - a - half - breaker terminal on the bus side, and an edge - switch CT and a middle - switch CT are respectively arranged on both sides of the one - and - a - half - breaker terminal; The several slave machines include slave machine 1 and slave machine 2 arranged according to the edge - switch CT and the middle - switch CT respectively, and n - 2 slave machines arranged according to each branch CT on the element or line side, where n is less than or equal to 32; The host and the several slave machines are connected by optical fibers and perform internal time synchronization; The host is used to perform relay protection logic discrimination for the extended T zone based on the data collected by each slave machine, and send a protection trip command to the corresponding slave machine. The relay protection includes ratio - restraint differential protection, over - current protection, breaker failure inter - tripping protection, CT disconnection discrimination, remote transmission, and CT saturation discrimination. The CT saturation discrimination is divided into steady - state CT saturation discrimination and transient CT saturation discrimination; The transient CT saturation discrimination logic is: Within the first time threshold T1 when ΔIf > Id0, if the ratio - restraint condition Id > K * If is not satisfied, and after the time when ΔIf > Id0 is greater than T1, the ratio - restraint condition is satisfied, it indicates transient CT saturation; The steady - state CT saturation discrimination logic is: After ΔIf > Id0 reaches the second time threshold T2, within the third time threshold T3 when ΔDId < KS * ΔDIf, if the ratio - restraint condition Id > K * If is not satisfied, and the time when ΔDId < KS * ΔDIf is greater than T3, and then the ratio - restraint condition is satisfied, it indicates steady - state CT saturation; Wherein, ΔIf is the sudden change of braking current, Id is the differential current, If is the braking current, K is the braking coefficient of ratio - restraint differential protection, Id0 is the differential threshold, ΔDId is the differential current difference value, ΔDIf is the braking current difference value, and KS is the current - difference ratio - restraint coefficient; The slave machine is used for the acquisition and upload of analog and digital quantity data, receiving and executing the protection trip command and removing the fault, and the slave machines have the function of mutual remote transmission of signals and inter - tripping; The relay protection system dynamically tracks the on - site operating conditions by introducing the state of the primary isolating switch. Specifically: there is no isolating switch in the interval on the bus side, and the current value is fixedly included in the differential and braking currents; the isolating switch position is set in the outgoing line interval of the branch. Whether the current value is included in the differential current of the small differential is determined by the state of the isolating switch G1, and the differential current of the small differential and the braking current do not include the outgoing line interval where the isolating switch G1 is in the open position.

2. The relay protection system applicable to an extended T zone according to claim 1, characterized in that: Both the host and the slave machines are configured with dual - CPU plug - ins. The dual - CPUs of the host are respectively connected point - to - point with the dual - CPUs of each slave machine; and the host and the slave machines perform internal time synchronization using IEEE1588.

3. The relay protection system applicable to an extended T zone according to claim 1, characterized in that: According to the branch CT layout, the sub-machine is equipped with the outgoing line interval "isolation switch position TWJ" input and "isolation switch strong separation" hard pressure plate to identify abnormal isolation switch position. Specifically: When the "isolation switch position TWJ" input state is inconsistent with the "isolation switch forced separation" hard pressure plate state, or when the "isolation switch position TWJ" input state is 1 and there is current in the outgoing line interval, it means that the isolation switch position is abnormal, and the switch position abnormality alarm is issued; When the knife switch position is abnormal, the knife switch position status takes the state of the isolation knife switch strong separation hard pressure plate.

4. A relay protection system suitable for extending the T zone according to claim 1, characterized in that: The action equation of the ratio-restrained differential protection is: In the formula, I i is the branch current of the i-th branch in zone T; n is the total number of branches in the T zone; I d0 is the differential action current threshold; K is the braking coefficient.

5. A relay protection system suitable for extending the T zone according to claim 1, characterized in that: The action equation of the overcurrent protection is: T>T SETⅠ T>T SETⅡ In the formula, I t.φ.max It is the maximum phase current of the CT on the component or line side; I gldzⅠ ,I gldzⅡ They are respectively the current setting values ​​of stage I and stage II of overcurrent protection; T SETⅠ / T SETⅡ They are respectively the time setting values ​​of stage I and stage II of overcurrent protection; T is the overcurrent protection time; It is the phase current after the branch current with side switch CT and middle switch CT on the bus side is converted to the component or line side; is the component or line side current.

6. A relay protection system suitable for extending the T zone according to claim 1, characterized in that: Circuit breaker failure joint trip protection means that when the host determines that the circuit breaker in the T zone fails, the circuit breaker connected in the T zone will trip, specifically: When the two failure start inputs provided by the external failure start device to the slave are detected at the same time, the current discrimination element is detected to see if it is open: If it is open, the side switch CT failure interlocking protection starts, and the side switch connected to the busbar is tripped after a delay; The current discrimination elements include phase current, zero-sequence current and negative-sequence current, and the "OR" logic of the three is open; The phase current is opened by the "AND" logic of the phase current steady-state quantity and the sudden change quantity; the sudden change quantity of the phase current is the phase current of any phase of the branch, and it is opened when it is greater than the sudden change quantity threshold value, and it is fixed and widened for 15 seconds after opening; the steady-state quantity of the phase current is the largest phase current of all branches, and it is opened when it is greater than the steady-state quantity threshold value; The zero-sequence current and negative-sequence current are both steady-state quantity criteria, and the maximum of the zero-sequence current and negative-sequence current of all branches is taken respectively, and the circuit is opened when it is greater than the set threshold value.

7. A relay protection system suitable for extending the T zone according to claim 1, characterized in that: CT disconnection judgment is divided into CT disconnection judgment based on the alarm section differential current exceeding the limit value and based on the blocking section differential current exceeding the limit value, where the alarm section differential current exceeding the limit value is lower than the blocking section differential current exceeding the limit value; specifically: When the differential current in the T zone exceeds the differential current over-limit value of the alarm section but does not exceed the differential current over-limit value of the locking section, an alarm signal is issued after a fixed delay; When the differential current exceeds the differential current over-limit value of the locking section, an alarm signal is issued after a fixed delay, and the differential protection is locked according to the phase.

8. The relay protection system suitable for extending the T zone according to claim 1, characterized in that: The remote transmission refers to multiplexing the communication network link between the master and slave machines to bidirectionally transmit the remote jump command or the information of the required switching quantity.

9. A relay protection method suitable for extending the T zone, implemented based on the relay protection system according to any one of claims 1 to 8, characterized in that: The method comprises: Each slave collects analog and switch data of the branch where it is located and uploads it to the host; The host computer performs extended T-zone relay protection logic judgment based on the data collected by each slave computer, and sends a protection trip command to the corresponding slave computer. The relay protection includes ratio brake differential protection, overcurrent protection, circuit breaker failure trip protection, CT disconnection judgment, remote transmission, and CT saturation judgment. After receiving the protection trip command, each slave executes the protection trip command and cuts off the fault.

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