CN112448373B - Method for realizing metal lateral difference protection of parallel multi-terminal direct current transmission system - Google Patents
Method for realizing metal lateral difference protection of parallel multi-terminal direct current transmission system Download PDFInfo
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- CN112448373B CN112448373B CN202011195970.3A CN202011195970A CN112448373B CN 112448373 B CN112448373 B CN 112448373B CN 202011195970 A CN202011195970 A CN 202011195970A CN 112448373 B CN112448373 B CN 112448373B
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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
- H02H7/262—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 involving transmissions of switching or blocking orders
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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
- H02H7/268—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 for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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Abstract
The invention discloses a method for realizing metal lateral difference protection of a parallel multi-terminal direct current transmission system, which relates to the technical field of direct current transmission systems, wherein a metal loop longitudinal difference protection device is arranged in each of a first converter station, a second converter station and a third converter station, a metal loop fault line selection device is also arranged in each of the third converter stations, and a bus area is also arranged in each of the third converter stations and is provided with a quick isolating switch; and arranging a metal loop lateral difference protection device at the second converter station and the third converter station. When communication faults occur between stations, the metal loop longitudinal differential protection device stops working, and the metal loop transverse differential device is put into working; the metal loop lateral difference device triggers corresponding protection actions according to the current of the opposite-station opposite-pole direct current line and the current of the opposite-station opposite-pole direct current line; the metal loop fault line selection device judges the type of the metal loop fault according to the protection action of the metal loop transverse difference device and adopts a corresponding fault clearing strategy.
Description
Technical Field
The invention relates to the technical field of direct current transmission systems, in particular to a method for realizing metal transverse error protection of a parallel multi-terminal direct current transmission system.
Background
The parallel multi-terminal direct current transmission system refers to a direct current transmission system of three or more converter stations, and is characterized in that multiple power supplies or multiple drop points are powered, and when multiple power supply areas are arranged on one transmission corridor to supply power to multiple load centers, the parallel multi-terminal direct current transmission system is more economical and flexible than the direct current transmission system at two ends.
The metal loop operation mode of the direct current transmission system refers to a monopole operation mode that one pole exits operation and the other pole uses the transmission line as a current return path between neutral points of the converter stations, and a line connecting the neutral points of the converter stations is called a metal loop. Compared with the conventional two-end direct current transmission system, the topological structure of the metal loop running mode of the parallel multi-end direct current transmission system is more complex, the metal loop line is divided into different line sections by the converter station, and the conventional protection and fault clearing method for the fault configuration of the metal loop by direct current is not fully applicable any more.
The metal loop longitudinal differential protection is the main protection for detecting the faults of the metal loop line, the realization of the protection function depends on the inter-station communication function, the metal loop longitudinal differential protection exits when the inter-station communication faults, and the faults of the metal loop line are detected by the metal loop transverse differential protection.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for realizing the metal lateral difference protection of a parallel multi-terminal direct current transmission system, which optimizes the configuration scheme of the original metal loop lateral difference protection and is suitable for the parallel multi-terminal direct current transmission system.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
a method for realizing metal transverse difference protection of a parallel multi-terminal direct current transmission system,
the parallel multi-terminal direct current transmission system has at least:
the first convertor station is positioned in the first area and is used for converting alternating current of a three-phase alternating current power grid in the first area into direct current and transmitting the converted direct current out through a direct current transmission line connected with the first convertor station;
the second converter station is positioned in the second area and is used for converting direct current input by a direct current transmission line connected with the second converter station into alternating current and inputting the converted alternating current into an alternating current power grid of the second area;
the third converter station is positioned in a third area, is connected with the first converter station and the second converter station in parallel through a direct current transmission line, is used for switching to a rectification operation mode when receiving a rectification operation instruction, converts alternating current of a three-phase alternating current power grid in the third area into direct current after the third area is put into operation, and transmits the converted direct current through the direct current transmission line connected with the third area; switching to an inversion operation mode when receiving an inversion operation instruction, converting direct current input by a direct current transmission line connected with the inverter into alternating current after the inverter operation instruction is put into operation, and inputting the converted alternating current into an alternating current power grid of the third area;
the first converter station, the second converter station and the third converter station are respectively provided with a metal loop longitudinal differential protection device, the third converter station is also provided with a metal loop fault line selection device, and the third converter station is also provided with a bus bar area and a quick isolating switch; the second converter station and the third converter station are provided with a metal loop lateral difference protection device
The method comprises the following steps:
the metal loop longitudinal differential protection device of the converter station triggers corresponding protection actions according to the current of the opposite pole direct current line of the station and the current of the opposite pole direct current line of the station;
the metal loop fault line selection device judges the type of the metal loop fault according to the protection action of the metal loop longitudinal differential protection device and adopts a corresponding fault clearing strategy;
when communication faults occur between stations, the metal loop longitudinal differential protection device stops working, and the metal loop transverse differential device is put into working;
the metal loop lateral difference device triggers corresponding protection actions according to the current of the opposite-station opposite-pole direct current line and the current of the opposite-station opposite-pole direct current line;
the metal loop fault line selection device judges the type of the metal loop fault according to the protection action of the metal loop transverse difference device and adopts a corresponding fault clearing strategy.
The realization method of the metal lateral difference protection of the parallel multi-terminal direct current transmission system comprises the steps of, further,
the metal loop lateral difference protection device of the third converter station adopts the following criteria:
the ground fault on the metal loop line 1 is detected, and the criterion is as follows:
|IdL1–IdL1_op|>Δ
and after the criterion is met, the third converter station protects the action.
The method for realizing the metal lateral difference protection of the parallel multi-terminal direct current transmission system comprises the following steps:
protection is put into operation under the working condition that the metal loop runs and the first converter station and the third converter station are simultaneously unlocked, and protection action delay and action strategy are as follows:
the action delay is T1, and the action strategy is: line 1 fault locks.
The realization method of the metal lateral difference protection of the parallel multi-terminal direct current transmission system comprises the steps of, further,
the metal loop lateral difference protection device of the second converter station adopts the following criteria:
|IdL_SC–IdL_op_SC|>Δ
and delta is a protection action fixed value, which can be the same as the protection fixed value of the third converter station, and after the criterion is met, the second converter station protects the action.
The realization method of the metal lateral difference protection of the parallel multi-terminal direct current transmission system comprises the steps of, further,
the second converter station protection action specifically includes:
protection is put into operation when the metal loop runs and is a grounding station, and protection action delay and action strategy are as follows:
the action delay is T2, and the action strategy is: line 2 fault locks.
In the implementation method of the metal lateral difference protection of the parallel multi-terminal direct current transmission system, further, the metal loop longitudinal difference protection device, the metal loop lateral difference protection device and the metal loop fault line selection device can adopt an embedded industrial control platform or a PC device.
The method for realizing the metal lateral difference protection of the parallel multi-terminal direct current transmission system further comprises the following steps:
when the third converter station operates, the protection of the metal loop line 1 is opened, and the criterion is that:
|IdL_op_SA–IdL1_op|>Δ；
when the third converter station exits, the protection of the whole length of the metal loop line is opened, and the criterion is that:
|IdL_op_SA–IdL_op_SC|>Δ
the metal loop line 1 is a metal loop between the first converter station and the third converter station, and the metal loop line 1 and the full-length protection criterion of the line cannot be opened at the same time, and the criterion meets the post-protection action.
The method for realizing the metal lateral difference protection of the parallel multi-terminal direct current transmission system further comprises the following steps:
when the first converter station and the third converter station are operated simultaneously, the protection of the metal loop line 1 is opened, and the criterion is that:
|IdL_op_SA–IdL1_op|>Δ
when the third converter station and the second converter station are operated simultaneously, the protection of the metal loop line 2 is opened, and the criterion is that:
|IdL_op_SC–IdL3_op|>Δ
the metal loop line 1 is a metal loop between the first converter station and the third converter station, the metal loop line 2 is a metal loop between the second converter station and the third converter station, and protection criteria of the metal loop line 1 and the metal loop line 2 may be simultaneously opened, and any criterion satisfies a post-protection action.
The realization method of the metal lateral difference protection of the parallel multi-terminal direct current transmission system comprises the steps of, further,
the metal loop longitudinal differential protection device of the second converter station adopts the following criteria:
when the third converter station operates, the protection of the metal loop line 2 is opened, and the criterion is:
|IdL_op_SC–IdL3_op|>Δ；
when the third converter station exits, the protection of the whole length of the metal loop line is opened, and the criterion is that:
|IdL_op_SA–IdL_op_SC|>Δ
the metal loop line 2 and the full-length protection criterion of the line cannot be opened at the same time, and the criterion meets the post-protection action.
The method for realizing the metal lateral difference protection of the parallel multi-terminal direct current transmission system further comprises the steps that the protection action result of the metal loop longitudinal difference protection device of each converter station is divided into two sections, and the action delay and action strategies of each section are respectively as follows:
the action delay of the first section is 600ms, and the action strategy is as follows: restarting the phase shift once, and locking the line fault if the phase shift is satisfied for the second time within 10 seconds;
the action delay of the second section is 1000ms, and the action strategy is as follows: line fault blocking.
The method for realizing the metal lateral difference protection of the parallel multi-terminal direct current transmission system further comprises the step of identifying the fault position of the metal loop line fault according to the protection action result detected by the third converter station:
when the protection action of the metal loop line 1 is exported, judging that the metal loop line 1 fails;
when the protection action of the metal return line 2 is exported, the metal return line 2 is judged to be faulty.
Compared with the prior art, the invention has the beneficial effects that: 1. the configuration scheme of the metal loop lateral difference protection is optimized, and the enabling conditions of protection opening of each converter station are determined, so that the protection can be suitable for a parallel multi-terminal direct current transmission system; 2. the fault line selection function of the metal loop line based on the metal loop lateral difference protection is configured, the fault position can be determined after the fault, and the selection of a fault clearing strategy is convenient.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following description will briefly explain the drawings needed in the embodiments, and it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a conventional dc power transmission system in a metal loop operation mode.
Fig. 2 is a schematic diagram of a metal loop operation mode of the parallel three-terminal dc power transmission system during differential protection, in which the station B operates in a rectifying mode.
Fig. 3 is a schematic diagram of a metal loop operation mode of the parallel three-terminal dc power transmission system during differential protection, in which the station B operates in an inversion mode.
Fig. 4 is a schematic diagram of a three-terminal dc power transmission system during differential protection, wherein station B operates in a rectifying mode.
Fig. 5 is a schematic diagram of a three-terminal dc power transmission system during differential protection, in which station B operates in an inversion mode.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
Examples:
it should be noted that the terms "first," "second," and the like in the description and the claims of the present invention and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the invention described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed or inherent to such process, method, article, or apparatus.
In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise. Furthermore, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
It should be understood that, in this embodiment, the first converter station, the third converter station, and the second converter station are denoted by the station a, the station B, and the station C, respectively; furthermore, some technical terms in the present invention are described: phase shift restarting once: the rectifier increases the triggering angle to a set angle at a certain speed, so that the rectifier is converted into an inversion state to operate; locking: in a conventional direct current transmission system, a fault pole is retreated to a locking state, and a converter is still connected with a direct current field; line fault blocking: the invention aims at a locking mode of line fault configuration of a parallel multi-terminal direct current transmission system, and a locked converter station is required to be selected according to the system operation mode and the fault position; unique type of converter station: a unique rectifying station or a unique inverting station in the system.
For better understanding of the invention, the prior art scheme is simply introduced, and the metal loop lateral difference protection function of the conventional direct current transmission system is configured as follows:
i IdL-IdL _op| >0.024pu, delay 1000ms lock.
Wherein IdL is the direct current of the local station, idL _op is the direct current of the opposite pole of the local station.
The metal loop differential protection is configured at both converter stations, but is only effective at the ground station in the metal loop mode of operation. When the metal loop has a grounding fault, the fault point and the grounding point form a circulation current, so that direct current line currents of the current electrode and the opposite electrode of the inversion station have a difference current, and the fault of the metal loop is judged.
Under the metal loop operation mode, the conventional two-end direct current transmission system only has one metal loop transmission line, and when the metal loop detects fault locking, the system is directly stopped.
In the parallel multi-terminal direct current transmission system, under the metal loop operation mode, two or more metal loop transmission lines are arranged, when a certain metal loop transmission line fails and needs to be locked, on the premise of ensuring reliable fault isolation, each converter station needs to be ensured to continue to operate to the greatest extent, so that the loss of the transmission power of the system is reduced.
Therefore, the existing metal loop lateral difference protection cannot meet the requirements of the parallel multi-terminal direct current transmission system, and research on a metal loop lateral difference protection configuration scheme and a fault line selection scheme suitable for the parallel multi-terminal direct current transmission system plays an important role in improving the reliability of the system.
The invention optimizes the enabling conditions of the original metal loop lateral difference protection, so that the invention is suitable for a parallel multi-terminal direct current transmission system; the metal loop fault position identification function is added, so that the judgment and identification of the metal loop fault position are realized, and the rapid removal of faults and the maintenance of the transmission power of the system are realized.
Referring to fig. 1 to 5, fig. 1 is a schematic diagram of a conventional dc power transmission system in a metal loop operation mode; fig. 2 is a schematic diagram of a metal loop operation mode of the parallel three-terminal dc power transmission system during differential protection, in which the station B operates in a rectifying mode; fig. 3 is a schematic diagram of a metal loop operation mode of the parallel three-terminal dc power transmission system during differential protection, in which the station B operates in an inversion mode; fig. 4 is a schematic diagram of a three-terminal dc power transmission system during differential protection, wherein station B is operating in a rectifying mode; fig. 5 is a schematic diagram of a three-terminal dc power transmission system during differential protection, in which station B operates in an inversion mode.
A method for realizing metal lateral difference protection of a parallel multi-terminal direct current transmission system comprises three or more converter stations, wherein an intermediate converter station can be a rectifier station or an inverter station. The implementation of the metal loop lateral difference protection of the parallel three-terminal direct current transmission system is used for illustration.
The station A, the station C and the station B are respectively provided with a metal loop longitudinal differential protection device, the station B is also provided with a metal loop fault line selection device, and the station B is also provided with a bus bar area and a quick disconnecting switch (HSS); the method comprises the steps of:
the metal loop longitudinal differential protection device of the converter station triggers corresponding protection actions according to the current of the opposite pole direct current line of the current station and the current of the opposite pole direct current line of the current station;
the metal loop fault line selection device judges the type of the metal loop fault according to the protection action of the metal loop longitudinal differential protection device and adopts a corresponding fault clearing strategy;
when communication faults occur between stations, the metal loop longitudinal differential protection device stops working, and the metal loop transverse differential device is put into working;
the metal loop lateral difference device triggers corresponding protection actions according to the current of the opposite-station opposite-pole direct current line and the current of the opposite-station opposite-pole direct current line;
the metal loop fault line selection device judges the type of the metal loop fault according to the protection action of the metal loop transverse difference device and adopts a corresponding fault clearing strategy.
As an alternative embodiment, in some embodiments, a metal loop differential protection is configured at the station B, and the ground fault on the metal loop line 1 is detected, where the criterion is:
|IdL1–IdL1_op|>Δ
and after the criterion is met, the station B protects the action.
In the above embodiment, further, protection is put into operation under the working condition that the metal loop runs and the AB two stations are simultaneously unlocked, and protection action delay and action strategy are:
the action delay is T1, and the action strategy is: line 1 fault locks.
As an alternative implementation, in some embodiments, a metal loop differential protection is configured at station C, with the criteria being:
|IdL_SC–IdL_op_SC|>Δ
the delta is a protection action fixed value, which can be the same as the protection fixed value of the station B, and after the criterion is met, the station C protects the action.
In the above embodiment, further, the protection is put into operation when the metal loop is in operation and is a ground station, and the protection action delay and action strategy are:
the action delay is T2, and the action strategy is: line 2 fault locks.
The action delay T2 is larger than the high-slope station metal loop lateral difference protection action delay T1, and T2=T1+200ms is set.
It should be noted that, after receiving the line fault blocking action signal and determining the fault location, different fault clearing strategies may be adopted for the metal loop faults at different locations, so as to reduce the power loss during line fault blocking.
As an alternative embodiment, in some embodiments, the station a is configured with a metal loop longitudinal differential protection, where the protection range is the metal loop line 1 or the full length of the metal loop line.
When the station B operates, the protection of the metal loop line 1 is opened, and the criterion is as follows:
|IdL_op_SA–IdL1_op|>Δ；
when the station B exits, the protection of the whole length of the metal loop line is opened, and the criterion is as follows:
|IdL_op_SA–IdL_op_SC|>Δ
the line 1 and the full-length protection criterion of the line cannot be opened at the same time, and the criterion meets the post-protection action.
As an alternative embodiment, in some embodiments, a metal loop longitudinal differential protection is configured at station B, with the protection range being metal loop line 1 and metal loop line 2.
When the station A and the station B operate simultaneously, the protection of the metal loop line 1 is opened, and the criterion is as follows:
|IdL_op_SA–IdL1_op|>Δ
when the station B and the station C operate simultaneously, the protection of the metal loop line 2 is opened, and the criterion is that:
|IdL_op_SC–IdL3_op|>Δ
the protection criteria of the line 1 and the line 2 may be simultaneously opened, and any criterion satisfies the post-protection action.
As an alternative embodiment, in some embodiments, the station C is configured with a metal loop longitudinal differential protection, where the protection range is the metal loop line 2 or the full length of the metal loop line.
When the station B operates, the protection of the metal loop line 2 is opened, and the criterion is:
|IdL_op_SC–IdL3_op|>Δ；
when the station B exits, the protection of the whole length of the metal loop line is opened, and the criterion is as follows:
|IdL_op_SA–IdL_op_SC|>Δ
the line 2 and the full-length protection criterion of the line are not opened at the same time, and the criterion meets the post-protection action.
As an alternative implementation manner, in some embodiments, each converter station collects the current on the metal loop line of other converter stations through inter-station communication, and a certain time is required for inter-station communication data transmission, so that when the differential current is calculated by each converter station metal loop longitudinal differential protection, the current of the current station needs to be delayed, and the delay time is the inter-station communication transmission time.
As an alternative implementation manner, in some embodiments, the protection action result of each station is divided into two sections, and the action delay and action policy of each section are respectively:
the action delay of the first section is 600ms, and the action strategy is as follows: restarting the phase shift once, and locking the line fault if the phase shift is satisfied for the second time within 10 seconds;
the action delay of the second section is 1000ms, and the action strategy is as follows: line fault blocking.
As an alternative implementation, in some embodiments, metal loop fault line selection logic is added. The protection action result can be used for judging whether the protected line has a grounding fault or not, and the fault position identification of the metal loop line fault is identified according to the protection action result detected by the station B:
when the protection action of the metal loop line 1 is exported, judging that the metal loop line 1 fails;
when the protection action of the metal return line 2 is exported, the metal return line 2 is judged to be faulty.
As an optional implementation manner, in some embodiments, after receiving the line fault blocking action signal, different fault clearing strategies are adopted for metal loop faults at different positions so as to reduce power loss during line fault blocking, and specific strategies for metal loop longitudinal differential protection are as follows:
1) After receiving the line fault locking action signal, judging whether the system runs at two ends, if so, turning to the step 8); if the operation is not the two-end operation, the step 2 is switched to
2) Judging whether the metal loop line 1 is faulty or not, if yes, turning to the step 3); if not, turning to step 5);
3) Judging whether the station A is a unique type converter station or not, and if so, converting to the step 8); if not, turning to step 4);
4) And (3) locking the station A, simultaneously executing phase shifting restarting once, pulling out a bipolar fast disconnecting switch HSS1 of the station B after the current is reduced, isolating a fault line from the station A, and finally automatically restarting the station B and the station C to realize continuous operation of the system.
5) Judging whether the fault is the fault of the metal loop line 2, if so, turning to the step 6); if not, turning to step 8);
6) Judging whether the station C is a unique type converter station or not, and if so, converting to the step 8); if not the only type converter station, turning to step 7);
7) And (3) locking the station C, simultaneously performing phase shifting restarting once, pulling out a bipolar fast disconnecting switch HSS3 of the station B after the current is reduced, isolating a fault line from the station C, and finally automatically restarting the station A and the station B to realize continuous operation of the system.
8) And locking all converter stations of the station, and stopping the system.
As an alternative implementation manner, in some embodiments, the metal loop longitudinal differential protection device, the metal loop lateral differential protection device and the metal loop fault line selection device may use an embedded industrial control platform or a PC device.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement the same, and are not intended to limit the scope of the present invention. All equivalent changes or modifications made in accordance with the essence of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. A method for realizing metal transverse difference protection of a parallel multi-terminal direct current transmission system,
the parallel multi-terminal direct current transmission system has at least:
the first convertor station is positioned in the first area and is used for converting alternating current of a three-phase alternating current power grid in the first area into direct current and transmitting the converted direct current out through a direct current transmission line connected with the first convertor station;
the second converter station is positioned in the second area and is used for converting direct current input by a direct current transmission line connected with the second converter station into alternating current and inputting the converted alternating current into an alternating current power grid of the second area;
the third converter station is positioned in a third area, is connected with the first converter station and the second converter station in parallel through a direct current transmission line, is used for switching to a rectification operation mode when receiving a rectification operation instruction, converts alternating current of a three-phase alternating current power grid in the third area into direct current after the third area is put into operation, and transmits the converted direct current through the direct current transmission line connected with the third area; switching to an inversion operation mode when receiving an inversion operation instruction, converting direct current input by a direct current transmission line connected with the inverter into alternating current after the inverter operation instruction is put into operation, and inputting the converted alternating current into an alternating current power grid of the third area;
the device is characterized in that the first converter station, the second converter station and the third converter station are respectively provided with a metal loop longitudinal differential protection device, the third converter station is also provided with a metal loop fault line selection device, and the third converter station is also provided with a bus bar area and a quick isolating switch; the second converter station and the third converter station are provided with a metal loop lateral difference protection device
The method comprises the following steps:
the metal loop longitudinal differential protection device of the converter station triggers corresponding protection actions according to the current of the opposite pole direct current line of the station and the current of the opposite pole direct current line of the station;
the metal loop fault line selection device judges the type of the metal loop fault according to the protection action of the metal loop longitudinal differential protection device and adopts a corresponding fault clearing strategy;
when communication faults occur between stations, the metal loop longitudinal differential protection device stops working, and the metal loop transverse differential device is put into working;
the metal loop lateral difference device triggers corresponding protection actions according to the current of the opposite-station opposite-pole direct current line and the current of the opposite-station opposite-pole direct current line;
the metal loop fault line selection device judges the type of the metal loop fault according to the protection action of the metal loop transverse difference device and adopts a corresponding fault clearing strategy.
2. The method for realizing the metal differential protection of the parallel multi-terminal direct current transmission system according to claim 1, wherein the method comprises the following steps of,
the metal loop lateral difference protection device of the third converter station adopts the following criteria:
the ground fault on the metal loop line 1 is detected, and the criterion is as follows:
| IdL1 – IdL1_op | >Δ
wherein, delta is a protection action fixed value, idL is direct current of the metal loop line 1; idL1_op is the protection action of the third converter station after the criterion of the current of the opposite pole direct current line of the metal loop line 1 is met.
3. The method for implementing metal differential protection of a parallel multi-terminal dc power transmission system according to claim 2, wherein the third converter station protection action specifically includes:
protection is put into operation under the operating mode that metal loop is operated and first converter station and third converter station unblock simultaneously, and protection action time delay and action strategy are:
the action delay is T1, and the action strategy is: line 1 fault locks.
4. The method for realizing the metal differential protection of the parallel multi-terminal direct current transmission system according to claim 1, wherein the method comprises the following steps of,
the metal loop lateral difference protection device of the second converter station adopts the following criteria:
| IdL_SC – IdL_op_SC | >Δ
wherein, delta is a protection action fixed value which is the same as the protection fixed value of the third converter station, and IdL _SC is the direct current of the third converter station; idL _op_SC is the antipodal DC link current of the third converter station; and after the criterion is met, the second converter station protects the action.
5. The method for implementing metal differential protection of parallel multi-terminal DC power transmission system of claim 4, wherein,
the second converter station protection action specifically includes:
protection is put into operation when the metal loop runs and is a grounding station, and protection action delay and action strategy are as follows:
the action delay is T2, and the action strategy is: line 2 fault locks.
6. The method for implementing metal differential protection of parallel multi-terminal dc power transmission system according to any one of claims 1 to 5, wherein the metal loop differential protection device, the metal loop differential protection device and the metal loop fault line selection device may be embedded industrial control platforms or PC devices.
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| EP3909105A1 (en) * | 2019-01-08 | 2021-11-17 | ABB Power Grids Switzerland AG | Differential protection of a transmission line |
| CN109659917B (en) * | 2019-01-18 | 2020-02-07 | 云南电网有限责任公司电力科学研究院 | Transient voltage-based multi-terminal flexible direct current line protection method and device |
| CN110071485B (en) * | 2019-04-22 | 2021-09-07 | 国网冀北电力有限公司 | Protection configuration method suitable for multi-terminal flexible substation |
| CN110797848B (en) * | 2019-11-25 | 2021-06-04 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Line longitudinal differential protection method suitable for three-terminal conventional direct-current power transmission system |
| CN111244915B (en) * | 2020-03-03 | 2022-06-28 | 南京南瑞继保电气有限公司 | Method for processing fault in metal return operating station of parallel multi-terminal direct-current transmission system |
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