CN112271698A - Comprehensive protection system and method for power collection line and box transformer substation of wind power plant - Google Patents
Comprehensive protection system and method for power collection line and box transformer substation of wind power plant Download PDFInfo
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- CN112271698A CN112271698A CN202011085496.9A CN202011085496A CN112271698A CN 112271698 A CN112271698 A CN 112271698A CN 202011085496 A CN202011085496 A CN 202011085496A CN 112271698 A CN112271698 A CN 112271698A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0061—Details of emergency protective circuit arrangements concerning transmission of signals
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
- H02H7/045—Differential protection of transformers
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
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Abstract
The invention relates to a comprehensive protection system and a comprehensive protection method for a power collection line and a box transformer substation of a wind power plant.A grid-connected protection device is arranged at a grid-connected point of the power collection line, and three-phase current and three-phase voltage of the grid-connected point are collected; setting a transformer side protection device to acquire the three-phase current at the high-voltage side and the three-phase current at the low-voltage side of the transformer, and judging whether the corresponding transformer has faults or not; sending the three-phase current of the high-voltage side of the transformer to a communication host; and the grid-connected protection device calculates the difference value between the sum of the three-phase currents at the high-voltage side of each transformer and the three-phase current at the grid-connected point, and judges whether a fault exists. The invention solves the problem of difficult setting of the protection fixed value of the current collection line and the box type transformer, effectively avoids the problem of override trip, and considers the selectivity, the quick action performance and the sensitivity of relay protection. The fault point can be safely and quickly removed, accident enlargement is avoided, the power generation facility of a normal line can continue to generate power, and the income of a power generation enterprise is improved.
Description
Technical Field
The invention relates to the technical field of power protection, in particular to a comprehensive protection system and method for a power collection line and a box transformer substation of a wind power plant.
Background
With the continuous expansion of the wind power generation capacity, the fault characteristics of the power transmission network are greatly different from those of a conventional power transmission line, and the special fault characteristics cause that the relay protection device cannot calculate according to a traditional fixed value setting method and cannot meet the selectivity, the quick action performance and the sensitivity of relay protection. In the power generation process, the electric energy of the wind driven generator is converted into 50Hz voltage with the same frequency as the power grid through an inverter of a tower, and then is boosted to 10kV or 35kV through a box-type substation (hereinafter referred to as box-type substation) and then is connected to a current collection circuit. Because the random fluctuation of wind power and the current direction can also change during the fault, the fault characteristic of the power generation system is obviously different from that of the traditional power supply. However, the current protection of the existing current collection line generally adopts the setting and configuration principle of the traditional power grid relay protection, but cannot meet the requirements of quick action, selectivity and sensitivity of the relay protection.
At present, a current collection circuit uses three-stage overcurrent protection according to a traditional relay protection scheme, but the setting of a fixed value is difficult, and the selectivity, the quick action and the sensitivity cannot be met aiming at the faults inside and outside the area. The other existing method adopts a scheme of configuring a fuse by adopting a current setting principle with time delay, but cannot meet the requirement of quick action and simultaneously has the problem of override trip.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a comprehensive protection system and a comprehensive protection method for a power collection line and a box transformer substation of a wind power plant, which solve the problem of difficult setting of protection fixed values of the power collection line and a box transformer, effectively avoid the problem of override trip, and give consideration to the selectivity, the quick action performance and the sensitivity of relay protection.
In order to achieve the aim, the invention provides a comprehensive protection system for a power collection line and a box transformer substation of a wind power plant, which comprises a grid-connected point protection device and a plurality of transformer side protection devices;
the grid-connected point protection device is arranged at a grid-connected point of a power collection circuit and is used for collecting three-phase current i of the grid-connected pointZAnd three phase voltage uZ；
The transformer side protection device collects three-phase current i at the high-voltage side of the transformerHLow voltage side three phase current iLJudging whether the corresponding transformer has faults or not; will be at the high voltage side three-phase current i of the transformerHSending the data to a communication host;
the grid-connected point protection device calculates the sum of three-phase currents at the high-voltage side of each transformer and the three-phase current i at the grid-connected pointZAnd judging whether a fault exists or not.
Further, the grid-connected point protection device and the plurality of transformer side protection devices are interconnected in a mode of an optical fiber transmission network, a lora network, a 5G network or a power carrier.
Furthermore, the grid-connected point protection device is used as a communication host and sends a time mark signal at regular time in a broadcasting mode; the box transformer substation side protection device is arranged on the box transformer substation side and used as a slave, and the sampling time is adjusted according to the time scale signal and the communication time delay of the communication host, so that the sampling is synchronous with the communication host.
Further, the transformer side protection device calculates a high-voltage side three-phase current iHAnd low-voltage side three-phase current iLIf the difference exceeds a set threshold, performing differential protection; tripping off the high-voltage side circuit breakers and the low-voltage side circuit breakers of the transformer, sending a tripping locking command to the grid-connected point protection device, locking the local side protection for delayed starting after the grid-connected point protection device receives the tripping locking command, waiting for the box transformer side protection device to trip to isolate faults, starting the local side tripping protection if the delayed overtime faults do not disappear, and tripping off the grid-connected point circuit breakers.
Furthermore, each transformer is also provided with a low-voltage side overcurrent protection device for judging the low-voltage side three-phase current iLAnd whether the corresponding threshold value is exceeded or not, and if the threshold value is exceeded, tripping off the breaker on the low-voltage side of the transformer.
Further, the transformer side protection device collects switching value signals of high-voltage side circuit breakers and low-voltage side circuit breakers of the transformer and sends the switching value signals to the grid-connected point protection device, the grid-connected point protection device judges states of corresponding circuit breakers, if the corresponding circuit breakers are not correctly tripped, the grid-connected point circuit breakers are tripped, a long-trip instruction is sent to the slave machines, and all the slave machines trip the high-voltage side circuit breakers.
Further, the transformer side protection device collects low-voltage side three-phase voltage uCAnd low-voltage side three-phase current iCCalculating power and sending the power to the communication host at regular time; i of low-voltage side three-phase currentCThe sampling precision is higher than the high-voltage side three-phase current iHLow voltage side three phase current iL。
Furthermore, the substation automation monitoring system is connected to the host through a network cable or a serial port, and reads data collected by the slave and the communication host.
Further, the grid-connected point protection device calculates the sum of three-phase currents on the high-voltage side of each transformer and the grid-connected point threePhase current iZIf the difference exceeds the set threshold, the grid-connected point circuit breaker is tripped, a long trip instruction is sent to the slave machine, and the slave machine trips the high-voltage side circuit breaker.
The invention also provides a comprehensive protection method using the comprehensive protection system for the power distribution plant power collection line and the box transformer substation, which comprises the following steps:
the grid-connected point protection device is used as a communication host and regularly sends a time mark signal in a broadcasting mode; the box transformer substation side protection device is arranged on the box transformer substation side and used as a slave, and the sampling time is adjusted according to the time scale signal and the communication time delay of the communication host, so that the sampling is synchronous with the communication host.
The transformer side protection device calculates high-voltage side three-phase current iHAnd low-voltage side three-phase current iLIf the difference exceeds a set threshold, performing differential protection; tripping off the high-voltage side circuit breakers and the low-voltage side circuit breakers of the transformer, sending a tripping locking command to the grid-connected point protection device, locking the tripping protection of the local side after the grid-connected point protection device receives the tripping locking command, waiting for the tripping isolation fault of the box transformer side protection device, and starting the tripping protection of the local side if the time delay overtime fault does not disappear.
Each transformer is also provided with a low-voltage side overcurrent protection device for judging a low-voltage side three-phase current iLWhether the voltage exceeds the corresponding threshold value or not, if so, tripping off the breaker on the low-voltage side of the transformer;
the grid-connected point protection device calculates the sum of three-phase currents at the high-voltage side of each transformer and the three-phase current i at the grid-connected pointZIf the difference exceeds the set threshold, the grid-connected point circuit breaker is tripped, a long trip instruction is sent to the slave machine, and the slave machine trips the high-voltage side circuit breaker.
The technical scheme of the invention has the following beneficial technical effects:
(1) the invention solves the problem of difficult setting of the protection fixed value of the current collection line and the box type transformer, effectively avoids the problem of override trip, and considers the selectivity, the quick action performance and the sensitivity of relay protection. The fault point can be safely and quickly removed, accident enlargement is avoided, the power generation facility of a normal line can continue to generate power, and the income of a power generation enterprise is improved.
(2) The current collection line and the box type transformer are protected as a whole, wherein fault current of the current collection line is synthesized and calculated by current vector values collected by all protection devices, and whether a fault exists in the current collection line is judged. The internal fault current of the box transformer substation is calculated by the high-low voltage side current of the transformer collected by a single device, and then whether a fault exists is judged.
(3) For the external fault, the differential motion of a collecting line and the differential motion of a transformer cannot be started, and the fault of the part from the inverter to the low-voltage side of the box transformer is tripped and isolated through the overcurrent protection of the device.
(4) Besides the protection function, the device can also collect the measured current and voltage of the box transformer substation, calculate the power generation power and the electric energy information, and upload telemetering and remote signaling information to a superior monitoring platform through a communication port of any device.
Drawings
FIG. 1 is a schematic diagram of a protection system architecture;
fig. 2 protection system fault diagram.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings in conjunction with the following detailed description. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
The method is characterized in that a plurality of power generation points exist on a current collection line of a wind field, the power generation points transmit electric energy to the current collection line during normal work, and when a box transformer substation or a line fails, the current flow direction of the power generation points is uncertain, so that the current flow direction of a grid connection point of the current collection line is uncertain, and the problem that an overcurrent fixed value cannot be set is caused. At present, a fixed value is set by a three-section type overcurrent method still adopted for a current collection circuit and a box transformer substation. The overcurrent protection is set according to the following principle:
a. setting according to the sensitivity related to the regulation of the two-phase short circuit at the tail end of the line in the minimum operation mode;
b. the maximum short-circuit current of the fault at the low-voltage side of the first box-type transformer is avoided;
c. maximum short-circuit current avoiding the fault at the tail end of the collecting wire;
under the scheme b, the current quick-break protection cannot protect the line for the full length, the time-limited current quick-break protection is adopted, the setting principle is set according to the specified sensitivity of the two-phase short circuit at the tail end of the line in the minimum operation mode, and otherwise, the setting principle is not adopted. The overcurrent protection is set according to the maximum load current of the circuit, and the action time limit is one time step higher than that of the current quick-break protection.
The above tuning principle has adaptability problem, and the following conclusion can be obtained:
1) the protection range of the current quick-break protection may enter the box-type transformer close to the bus, so that the current protection setting value cannot distinguish the near high-voltage side fault of the box-type transformer and the fault of the power collection line. Therefore, when the box type transformer fails, the protection of the collecting line (zero time limit) can trip step by step, and the protection loses selectivity.
2) In order to avoid override trip and improve selectivity, the current quick-break protection of the current collection line can be properly delayed, but the quick-acting performance of the protection is sacrificed at the moment, and the delay matching of the current collection line and the box type transformer is difficult because the fuse protection adopted by the box type transformer has the inverse time limit fusing characteristic.
3) If a short-circuit fault occurs in the rear section of the collecting line and the short-circuit current is not very large, the protection device of the grid-connected point may not be started, so that the fault exists for a long time and the accident is enlarged.
Based on the above conclusion, the present invention discloses a centralized protection system for a current collecting line and a box transformer substation as an integrated system, and the structure of the centralized protection system is shown in fig. 1. A. Laying an optical fiber network with the same path as the current collecting line, and installing an optical splitter at the connection position of the box transformer substation; B. a current Transformer (TA) and a voltage Transformer (TV) are arranged at a grid connection point of a collecting line; C. respectively installing a protection TA, a measurement TA and a TV at the high-voltage side and the low-voltage side of the box transformer substation, wherein the TV can not be installed at the high-voltage side; D. the protection measurement and control device is respectively arranged in a grid-connected point of a collecting line and a box transformer substation; E. the protection devices are connected through an optical fiber network, wherein the grid-connected point device is a host, the box transformer substation side device is a slave, the host collects current and voltage of a grid-connected point, and the slave collects current and voltage of two sides of a box transformer substation; F. the protection method comprises two functions of large differential and small differential, wherein the differential of the high-low voltage side of the small differential box transformer substation is realized, the high-low voltage side current is collected by the protection device, and the difference comparison is carried out after vector conversion to judge whether the box transformer substation has faults or not. G. When the host computer is synchronized with the slave computers through the optical fiber network, the sampling time of all the devices is kept consistent. The slave computer sends current sampling information of the high-voltage side of the box transformer substation to the host computer at regular time, the host computer collects the current information of all the slave computers in the network by using a high-speed transmission network, and meanwhile, the current information is compared with the current information collected by the main body to judge whether a current collecting circuit has a fault. H. The device uses differential protection as main protection, and is also provided with over-current protection, voltage protection, frequency protection and non-electric quantity protection functions as backup protection; I. the device has a protection function, and can also collect signals of a measurement TA of the box transformer substation to calculate measurement data and electric energy information, and the comprehensive automation system of the transformer substation is connected with a grid-connected point host through a network cable to read the protection measurement information of all devices in the network.
The comprehensive protection system for the power collection line and the box transformer substation of the wind power plant comprises a grid-connected point protection device and a plurality of transformer side protection devices.
The transformer side protection device collects three-phase current i at the high-voltage side of the transformerHLow voltage side three phase current iLJudging whether the corresponding transformer has faults or not; will be at the high voltage side three-phase current i of the transformerHAnd sending the information to the communication host. The transformer side protection device collects three-phase voltage u at the low-voltage sideCAnd low-voltage side three-phase current iCCalculating power and sending the power to the communication host at regular time; i of low-voltage side three-phase currentCThe sampling precision is higher than the high-voltage side three-phase current iHLow voltage side three phase current iL. High-voltage side three-phase current iHLow voltage side three phase current iLI of collected range ratio to low-voltage side three-phase currentCThe range of the measuring range is larger. The transformer side protection device collects the switching value signals of the high-voltage side circuit breaker and the low-voltage side circuit breaker of the transformer and sends the switching value signals to the grid-connected point protection device.
The box transformer substation side protection device is arranged on the box transformer substation side and used as a slave, and the sampling time is adjusted according to the time scale signal and the communication time delay of the communication host, so that the sampling is synchronous with the communication host.
The grid-connected point protection device is arranged at a grid-connected point of a power collecting line and is used for collecting three-phase current i of the grid-connected pointZAnd three phase voltage uZ(ii) a The grid-connected protection device calculates the sum of three-phase currents at the high-voltage side of each transformer and the three-phase current i at the grid-connected pointZAnd judging whether a fault exists or not. The grid-connected point protection device is used as a communication host, and signals with time marks are sent regularly in a broadcasting mode, so that the sampling time of the host and the slave are unified. The grid-connected point protection device calculates the sum of three-phase currents at the high-voltage side of each transformer and the three-phase current i at the grid-connected pointZIf the difference exceeds the set threshold, the grid-connected point circuit breaker is tripped, a long trip instruction is sent to the slave machine, and the slave machine trips the high-voltage side circuit breaker. Through sampling synchronization, the slave machine sends a current vector value and a switching value signal of the high-voltage side of the slave machine to the host machine at regular time, and the host machine receives the slave machine signal of the line and then performs differential flow calculation with the sampling signal of the master machine, so that whether the line has a fault or not is judged.
Each transformer is also provided with a low-voltage side overcurrent protection device for judging a low-voltage side three-phase current iLWhether the voltage exceeds the corresponding threshold value or not, if so, tripping off the breaker on the low-voltage side of the transformer;
the grid connection point protection device and the transformer side protection device comprise: nine-grid keyboard circuit, LCD, switching value acquisition circuit, trip circuit for driving circuit breaker, AC acquisition circuit for acquiring analog signals, signal processing circuit, RS485 communication circuit, optical fiber communication circuit and RJ45 interface.
As shown in fig. 2, the current calculation in the protection system is characterized in that: the current flowing from the transformer to the grid connection point is taken as a positive direction, and the current flowing from the grid connection point to the transformer is taken as a negative direction. In normal operation, the host side samples the current iZ＝i1H+i2H+...+inH。
If the point k1 fails, as in FIG. 2, the host judges the current i according to the grid-connected point voltageZDirection when iZWhen the current is positive, the host computer calculates the fault current ik1＝i1H+i2H+...+inH-iZ. When i isZIn the reverse direction, the fault current ik1＝i1H+i2H+...+inH+iZThe master machine can judge whether the fault current exceeds the differential constant value or not, judge whether a fault occurs or not, and if the fault occurs, trip off the grid-connected point switch and send a long-trip command to the slave machine.
If the point k2 fails, as in FIG. 2, the host judges the current i according to the grid-connected point voltageZDirection when iZWhen the current is positive, the host computer calculates the fault current ik2＝i1H+i2H+...+inH-iZ. When i isZIn the reverse direction, the fault current ik2＝i1H+i2H+...+inH+iZThe master machine can judge whether the fault current exceeds the differential constant value or not, judge whether a fault occurs or not, and if the fault occurs, trip off the grid-connected point switch and send a long-trip command to the slave machine.
As shown in fig. 2, if the k3 point fails, the slave can calculate the fault current | i through the current of the high-low voltage sidek3|＝|i2H|-|i2LL. The slave starts the differential protection logic, trips the upper circuit breaker and the lower circuit breaker of the transformer, and simultaneously sends a tripping locking command to the host to prevent override tripping.
As shown in fig. 2, if point k4 fails, the calculated current between the master and the slave still satisfies iZ＝i1H+i2H+...+inHAnd the host judges that the overcurrent at the moment is an out-of-range fault, a tripping program is not started, the # N transformer side protection device calculates that differential current does not exist according to high-low voltage current, differential protection cannot be started, the fault at the point is judged and the tripping program is started by low-voltage side overcurrent protection logic of the # N transformer side protection device, and a box-type transformer low-voltage side switch is tripped.
The slave computer calculates the starting electric power and electric energy information according to the low-voltage side measured current and the low-voltage side voltage, the starting electric power and the electric energy information are sent to the host computer at regular time through the optical fiber network, the automatic transformer substation monitoring system is connected to the host computer through a network cable or a serial port, and the remote measuring and remote signaling information of the slave computer and the host computer is read. Wherein telemetry refers to current, voltage, power, frequency; the remote signaling indicates the switch position of the circuit breaker, the switch state of a transformer door, the switch state of auxiliary monitoring equipment in the box transformer substation and the like.
The communication between the devices is not limited to EPON optical fiber transmission, and data transmission can be carried out by adopting a lora networking mode, an 4/5G networking mode, a power carrier networking mode and a wifi networking mode.
The invention also provides a comprehensive protection method using the comprehensive protection system for the power distribution plant power collection line and the box transformer substation, which comprises the following steps:
the grid-connected point protection device is used as a communication host and regularly sends a time mark signal in a broadcasting mode; the box transformer substation side protection device is arranged on the box transformer substation side and used as a slave, and the sampling time is adjusted according to the time scale signal and the communication time delay of the communication host, so that the sampling is synchronous with the communication host.
The transformer side protection device calculates high-voltage side three-phase current iHAnd low-voltage side three-phase current iLIf the difference exceeds a set threshold, performing differential protection; tripping off the high-voltage side circuit breakers and the low-voltage side circuit breakers of the transformer, sending a tripping locking command to the grid-connected point protection device, locking the local side protection for delayed starting after the grid-connected point protection device receives the tripping locking command, waiting for the box transformer side protection device to trip to isolate faults, starting the local side tripping protection if the delayed overtime faults do not disappear, and tripping off the grid-connected point circuit breakers.
Each transformer is also provided with a low-voltage side overcurrent protection device for judging a low-voltage side three-phase current iLWhether the voltage exceeds the corresponding threshold value or not, if so, tripping off the breaker on the low-voltage side of the transformer;
the grid-connected point protection device calculates the sum of three-phase currents at the high-voltage side of each transformer and the three-phase current i at the grid-connected pointZIf the difference exceeds the set threshold, the grid-connected point circuit breaker is tripped off, and a long-trip instruction is sent to the slave,the slave trips the high side breaker.
In summary, the invention relates to a comprehensive protection system and method for a power collection line and a box transformer substation of a wind power plant, wherein a grid-connected point protection device is arranged at a grid-connected point of the power collection line, and three-phase current and three-phase voltage of the grid-connected point are collected; setting a transformer side protection device to acquire the three-phase current at the high-voltage side and the three-phase current at the low-voltage side of the transformer, and judging whether the corresponding transformer has faults or not; sending the three-phase current of the high-voltage side of the transformer to a communication host; and the grid-connected point protection device calculates the difference value between the sum of the three-phase currents at the high-voltage side of each transformer and the three-phase current at the grid-connected point, and judges whether a fault exists. The invention solves the problem of difficult setting of the protection fixed value of the current collection line and the box type transformer, effectively avoids the problem of override trip, and considers the selectivity, the quick action performance and the sensitivity of relay protection. The fault point can be safely and quickly removed, accident enlargement is avoided, the power generation facility of a normal line can continue to generate power, and the income of a power generation enterprise is improved.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (10)
1. A comprehensive protection system for a power collection line and a box transformer substation of a wind power plant is characterized by comprising a grid-connected point protection device and a plurality of transformer side protection devices;
the grid-connected point protection device is arranged at a grid-connected point of a power collection circuit and is used for collecting three-phase current i of the grid-connected pointZAnd three phase voltage uZ；
The transformer side protection device collects three-phase current i at the high-voltage side of the transformerHLow voltage side three phase current iLAnd judging whether the corresponding transformer has a fault(ii) a Will be at the high voltage side three-phase current i of the transformerHSending the data to a communication host;
the grid-connected point protection device calculates the sum of three-phase currents at the high-voltage side of each transformer and the three-phase current i at the grid-connected pointZAnd judging whether a fault exists or not.
2. The integrated protection system for the power distribution lines and box transformers of the wind power plant according to claim 1, wherein the grid-connected point protection device and the plurality of transformer side protection devices are interconnected by means of an optical fiber transmission network, a lora network, a 5G network or a power carrier.
3. The integrated protection system for the power distribution lines and box substations of the wind power plant according to claim 1 or 2, wherein the grid-connected point protection device is used as a communication host and periodically sends a time scale signal in a broadcast manner; the box transformer substation side protection device is arranged on the box transformer substation side and used as a slave, and the sampling time is adjusted according to the time scale signal and the communication time delay of the communication host, so that the sampling is synchronous with the communication host.
4. The integrated protection system for the power distribution line and box transformer substation of the wind power plant according to claim 3, wherein the transformer side protection device calculates a high-voltage side three-phase current iHAnd low-voltage side three-phase current iLIf the difference exceeds a set threshold, performing differential protection; tripping off the high-voltage side circuit breakers and the low-voltage side circuit breakers of the transformer, sending a tripping locking command to the grid-connected point protection device, locking the local side protection for delayed starting after the grid-connected point protection device receives the tripping locking command, waiting for the box transformer side protection device to trip to isolate faults, starting the local side tripping protection if the delayed overtime faults do not disappear, and tripping off the grid-connected point circuit breakers.
5. The integrated protection system for the power distribution line and box transformer substation of the wind power plant as claimed in claim 4, wherein each transformer is further provided with a low-voltage side overcurrent protection device for judging a low-voltage side three-phase current iLWhether or not the corresponding threshold value is exceededAnd if the voltage exceeds the preset value, tripping off the breaker on the low-voltage side of the transformer.
6. The integrated protection system for the power collection line and the box transformer of the wind power plant according to claim 5, wherein the transformer side protection device collects switching value signals of high-voltage side circuit breakers and low-voltage side circuit breakers of a transformer and sends the signals to the grid-connected point protection device, the grid-connected point protection device judges states of corresponding circuit breakers, if the circuit breakers are not correctly tripped, the grid-connected point circuit breakers are tripped, a long tripping instruction is sent to the slave machines, and all the slave machines trip off the high-voltage side circuit breakers.
7. The integrated protection system for the power distribution line and box transformer substation of the wind power plant according to claim 5, wherein the transformer side protection device collects a low-voltage side three-phase voltage uCAnd low-voltage side three-phase current iCCalculating power and sending the power to the communication host at regular time; i of low-voltage side three-phase currentCThe sampling precision is higher than the high-voltage side three-phase current iHLow voltage side three phase current iL。
8. The integrated protection system for the power distribution lines and box substations of the wind power plant according to claim 7, wherein the substation automation monitoring system is connected to the host computer through a network cable or a serial port, and reads data collected from the slave computer and the communication host computer.
9. The integrated protection system for the power distribution network and the box transformer of the wind power plant according to claim 5, wherein the grid-connected point protection device calculates the sum of the three-phase currents on the high-voltage side of each transformer and the three-phase current i of the grid-connected pointZIf the difference exceeds the set threshold, the grid-connected point circuit breaker is tripped, a long trip instruction is sent to the slave machine, and the slave machine trips the high-voltage side circuit breaker.
10. An integrated protection method using the integrated protection system for the power plant power collection line and box transformer substation of any one of claims 1 to 9, comprising:
the grid-connected point protection device is used as a communication host and regularly sends a time mark signal in a broadcasting mode; the box transformer substation side protection device is arranged on the box transformer substation side and used as a slave, and the sampling time is adjusted according to the time scale signal and the communication time delay of the communication host, so that the sampling is synchronous with the communication host.
The transformer side protection device calculates high-voltage side three-phase current iHAnd low-voltage side three-phase current iLIf the difference exceeds a set threshold, performing differential protection; tripping off the high-voltage side circuit breakers and the low-voltage side circuit breakers of the transformer, sending a tripping locking command to the grid-connected point protection device, locking the tripping protection of the local side after the grid-connected point protection device receives the tripping locking command, waiting for the tripping isolation fault of the box transformer side protection device, and starting the tripping protection of the local side if the time delay overtime fault does not disappear.
Each transformer is also provided with a low-voltage side overcurrent protection device for judging a low-voltage side three-phase current iLWhether the voltage exceeds the corresponding threshold value or not, if so, tripping off the breaker on the low-voltage side of the transformer;
the grid-connected point protection device calculates the sum of three-phase currents at the high-voltage side of each transformer and the three-phase current i at the grid-connected pointZIf the difference exceeds the set threshold, the grid-connected point circuit breaker is tripped, a long trip instruction is sent to the slave machine, and the slave machine trips the high-voltage side circuit breaker.
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