CN113555858A - Control method, device and protection system for direct current power transmission system under metal return wire - Google Patents
Control method, device and protection system for direct current power transmission system under metal return wire Download PDFInfo
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- CN113555858A CN113555858A CN202110858431.1A CN202110858431A CN113555858A CN 113555858 A CN113555858 A CN 113555858A CN 202110858431 A CN202110858431 A CN 202110858431A CN 113555858 A CN113555858 A CN 113555858A
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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
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
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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]
Abstract
The application relates to a control method, a device and a protection system of a direct current transmission system under a metal return wire, when the direct current transmission system operates in a single-pole metal return wire connection mode, analysis can be carried out by obtaining the state of a metal return wire change-over switch of the direct current transmission system at the moment, and if the metal return wire change-over switch is combined and the current value flowing through the metal return wire change-over switch meets a preset condition, the metal return wire change-over switch is directly controlled to be opened. Through the scheme, the metal return line change-over switch can be cut off only under the condition that the metal return line change-over switch is similar to be stolen, so that the fault is eliminated on the premise of not stopping the direct current power transmission system, and the direct current utilization rate is effectively improved.
Description
Technical Field
The application relates to the technical field of high-voltage direct-current power transmission, in particular to a control method, a device and a protection system of a direct-current power transmission system under a metal return wire.
Background
High Voltage Direct Current (HVDC) is high power long distance DC transmission with stable DC without inductive reactance, synchronization and other advantages. The method has the advantages that the short-circuit capacity of the system is not increased, and the asynchronous networking operation of two power systems and the networking of the power systems with different frequencies are convenient to realize; the power modulation of the direct current system can improve the damping of the power system, inhibit low-frequency oscillation and improve the power transmission capacity of the alternating current power transmission lines running in parallel.
The high-voltage direct-current transmission system has three wiring modes, namely a bipolar earth return wire, a monopolar earth return wire and a monopolar metal return wire. Under the condition of the single-pole metal return wire, only one grounding point of the direct current transmission system is needed, namely, an in-station grounding grid of a certain station is used as a clamping point of the direct current transmission system, and the station is a grounding station under the metal return wire. When a second grounding point occurs in the system, current flows between the two grounding points through the ground, overcurrent occurs in the grounding network in the station of the grounding station, and the direct current protection system stops direct current when detecting that large current flows into the grounding network in the station in order to protect the grounding network in the station from being damaged.
However, in addition to the ground fault, a situation similar to theft occurs due to the metal return line changeover switch of the high-voltage direct-current transmission system, so that a large current flows into the in-station grounding grid. At the moment, if the direct current protection system detects that large current flows into the station grounding grid, the metal return line change-over switch is stolen and mistakenly regarded as a grounding fault, and direct current is directly stopped.
Disclosure of Invention
Therefore, it is necessary to provide a method, an apparatus and a protection system for controlling a dc power transmission system under a metal return line, in order to solve the problem of dc outage caused by non-ground faults, such as the situation of sneak-in, occurring in a metal return line transfer switch.
A method for controlling a DC power transmission system under a metal return wire comprises the following steps: when the direct current transmission system is in a single-pole metal return wire working state, acquiring a current value of a metal return wire change-over switch of the direct current transmission system; judging whether the metal return line change-over switch is combined or not; when the metal return line change-over switch is combined, judging whether the current value meets a preset condition; and when the current value meets the preset condition, controlling the metal return line change-over switch to be in an open circuit.
In one embodiment, after the step of determining whether the current value satisfies the preset condition when the metallic return line change-over switch is combined, the method further includes: and when the current value does not meet the preset condition, controlling the metal return line change-over switch to maintain the current running state, and returning to the step of obtaining the current value of the metal return line change-over switch of the direct current transmission system.
In one embodiment, the step of determining whether the current value satisfies a preset condition includes: and judging whether the duration time of the current value greater than the preset current threshold reaches a preset duration.
In one embodiment, the step of determining whether the duration that the current value is greater than the preset current threshold reaches the preset duration includes: judging whether the current value is larger than a preset current threshold value or not; when the current value is larger than the preset current threshold value, timing by a preset time length; and in the process of judging whether the timing reaches the preset duration, whether the current value is continuously greater than the preset current threshold value or not is judged, and the fact that the current value is continuously greater than the preset current threshold value means that the duration of the current value greater than the preset current threshold value reaches the preset duration.
In one embodiment, after the step of determining whether the current value is greater than the preset current threshold, the method further includes: and when the current value is smaller than or equal to a preset current threshold value, controlling the metal return line change-over switch to maintain the current running state, and returning to the step of obtaining the current value of the metal return line change-over switch of the direct current transmission system.
In an embodiment, after the step of determining whether the current value is continuously greater than the preset current threshold value in the process of determining that the timing reaches the preset duration, the method further includes: and when the current value is not continuously larger than the preset current threshold value, controlling the metal return line change-over switch to maintain the current running state, and returning to the step of obtaining the current value of the metal return line change-over switch of the direct current transmission system.
In one embodiment, the preset time period is 100 milliseconds to 500 milliseconds.
In one embodiment, before the step of obtaining the current value of the metal return line changeover switch of the dc power transmission system when the dc power transmission system is in the single-pole metal return line operating state, the method further includes: acquiring operation parameters of a direct current transmission system; and analyzing whether the direct current power transmission system is in a single-pole metal return wire working state or not according to the operation parameters.
A DC power transmission system control device under metal return includes: the current value acquisition module is used for acquiring the current value of a metal return wire change-over switch of the direct current transmission system when the direct current transmission system is in a single-pole metal return wire working state; the combining analysis module is used for judging whether the metal return line change-over switch is combined or not; the current analysis module is used for judging whether the current value meets a preset condition or not when the metal return line change-over switch is combined; and the circuit breaking control module is used for controlling the metal return line change-over switch to be in circuit breaking when the current value meets the preset condition.
A protection system of a direct current power transmission system under a metal return wire comprises a current collector and a processor, wherein the current collector is arranged on a metal return wire change-over switch and connected with the processor, the current collector is used for collecting a current value corresponding to the metal return wire change-over switch and sending the current value to the processor, and the processor is used for performing direct current power transmission control according to the direct current power transmission system control method.
According to the control method, the control device and the protection system for the direct current power transmission system under the metal return wire, when the direct current power transmission system operates in a single-pole metal return wire connection mode, analysis can be carried out by obtaining the state of the metal return wire change-over switch of the direct current power transmission system at the moment, and if the metal return wire change-over switch is combined and the current value flowing through the metal return wire change-over switch meets the preset condition, the metal return wire change-over switch is directly controlled to be in an open circuit state. Through the scheme, the metal return line change-over switch can be cut off only under the condition that the metal return line change-over switch is similar to be stolen, so that the fault is eliminated on the premise of not stopping the direct current power transmission system, and the direct current utilization rate is effectively improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for controlling a dc power transmission system under a metal return line in an embodiment;
fig. 2 is a schematic structural diagram of a dc power transmission system under a metal return line in an embodiment;
fig. 3 is a schematic diagram illustrating a current flow when an internal network of a dc power transmission system is grounded under a metal return line in an embodiment;
fig. 4 is a schematic structural diagram of a dc power transmission system under a metal return line in another embodiment;
fig. 5 is a schematic diagram illustrating a current flow when an internal network of a dc power transmission system is grounded under a metal return line in another embodiment;
fig. 6 is a schematic diagram illustrating a current flow when an internal network of a dc power transmission system is grounded under a metal return line in another embodiment;
fig. 7 is a schematic flow chart of a method for controlling a dc power transmission system under a metal return line in another embodiment;
fig. 8 is a schematic flow chart illustrating a method for controlling a dc power transmission system under a metal return line according to yet another embodiment;
FIG. 9 is a schematic diagram illustrating a process of analyzing predetermined conditions according to an embodiment;
fig. 10 is a schematic flow chart of a method for controlling a dc power transmission system under a metal return line according to yet another embodiment;
fig. 11 is a schematic structural diagram of a dc power transmission system control apparatus under a metal return line in an embodiment;
fig. 12 is a schematic structural diagram of a dc power transmission system control apparatus under a metal return line in another embodiment;
fig. 13 is a schematic structural diagram of a protection system of a dc power transmission system under a metal return line in an embodiment.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are illustrated in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Referring to fig. 1, a method for controlling a dc power transmission system under a metallic return line includes step S100, step S200, step S300, and step S400.
And step S100, when the direct current transmission system is in a single-pole metal loop working state, acquiring a current value of a metal loop change-over switch of the direct current transmission system.
Specifically, in the operation process of the direct current transmission system, besides the occurrence of the ground fault, an overcurrent occurs in the in-station grounding grid due to other special conditions. When the traditional direct current protection system detects that the in-station grounding grid has overcurrent, direct current can be directly stopped, so that the direct current utilization rate of a direct current transmission system is low. And for the in-station grounding network overcurrent caused by the stealing connection of the metal return line change-over switch in the direct current transmission system, the overcurrent phenomenon can be eliminated by processing the opening and closing state of the metal return line change-over switch. According to the scheme of the embodiment, the stealing-connection state of the metal loop transfer switch is detected, and after the stealing-connection state is detected, the metal loop transfer switch is directly controlled to be opened so as to eliminate the overcurrent phenomenon of the grounding network in the station, so that the outage rate of direct current is reduced.
It can be understood that the dc power transmission system in which the phenomenon of overcurrent of the in-station grounding grid due to the stealing engagement of the metallic return line transfer switch is not unique, and for the convenience of understanding the embodiments of the present application, the following explanation is made in combination with two common dc power transmission systems.
Referring to fig. 2, a two-terminal dc power transmission system is shown, wherein Q1-Q6, Q71, and Q8-Q9 all represent isolation switches, the two-terminal dc power transmission system includes two stations, station 1 and station 2, wherein station 1 is a rectifier station, and station 2 is an inverter station, for the two-terminal dc power transmission system, MRTB (metal loop transfer switch) and MRS (metal loop switch) are configured only at station 1, and high-speed ground switch (HSGS) is configured only at station 2. Under the metal return wire, an intra-station high-speed grounding switch (HSGS) of the inverter station is generally closed, an intra-station grounding grid of the inverter station is used as a clamping point of the direct-current transmission system, the station 2 is a grounding station under the metal return wire, and the station 1 is a non-grounding station under the metal return wire. In this case, if two isolating switches (i.e., shown in fig. Q4 and Q6) at two ends of the non-ground station metal loop transfer switch MRTB cannot be pulled apart due to a fault, at this time, the MRTB is mistakenly closed due to misoperation, two-point grounding of the low-voltage dc system, series current and the like, so that the grounding electrode is connected by isolation; or the grounding electrode of the non-grounding station is converted from isolation to connection due to misoperation of an operator. At this time, the earth current flows to the station 2 grounding grid as shown in fig. 3, so that the station 2 grounding grid has an overcurrent phenomenon.
Referring to fig. 4, two of the three-terminal hybrid dc power transmission systems are shown, arrows indicate current flow under three-terminal metal loops (taking pole 1 as an example), and Q1-Q6, Q71, and Q8-Q9 all represent isolation switches. Wherein, the station 1 is a rectifying station, and the stations 2 and 3 are inverter stations. For this three-terminal dc power transmission system, MRTB (metal return line changeover switch) and MRS (metal return line switch) are arranged only in station 2 (inverter station) and station 3 (inverter station), and high-speed ground switch (HSGS) is arranged only in station 1 (rectifier station). For a three-terminal direct-current transmission system, an in-station grounding switch (HSGS) of a station 1 is closed under a metal return wire, an in-station grounding grid of the station 1 is used as a clamp point of the direct-current transmission system, the station 1 (a rectifying station) is a grounding station under the metal return wire, and a station 2 (an inverting station) and a station 3 (an inverting station) are non-grounding stations under the metal return wire.
In a three-terminal hybrid direct-current transmission system, the following three situations occur: (1) two isolating switches (Q4, Q6) of the metal loop change-over switch MRTB of the non-grounding station cannot be pulled open due to faults, and at the moment, the MRTB is mistakenly closed due to misoperation, two-point grounding of a low-voltage direct-current system, series electricity and the like, so that a grounding electrode is connected in a switching mode from isolation to isolation; (2) due to misoperation of an operator, the grounding electrode of the non-grounding station is converted from isolation to connection; (3) when the station 2 performs maintenance work or other operations, the bus bar isolating switch (Q2), the metal connecting wire isolating switch (Q71), the metal loop transfer switch (MRS) on the conversion bus bar and the isolating switches (Q1, Q3), the MRTB and the isolating switches (Q4, Q6), and the grounding electrode circuit isolating switch (Q8 or Q9) are simultaneously in the on position, which is equivalent to grounding the bus bar, and current enters the ground from the station 2 through the metal connecting wire, the conversion bus bar and the grounding electrode, and flows into the station 1 grounding grid through the ground. In this case, the current flows corresponding to (1) and (2) can be combined with fig. 5, and the current flow corresponding to (3) can be combined with fig. 6, and in all three cases, the in-station grounding grid of the metal return wire three-terminal hybrid dc power transmission system grounding station can be caused to overflow.
In the two types of direct current transmission systems, when the in-station grounding grid is in an overcurrent state due to the reasons, the overcurrent state can be eliminated without stopping direct current operation by disconnecting the metal loop change-over switch. The processor can intuitively obtain whether the current direct current power transmission system adopts the wiring mode of the single-pole metal return wire or not only by combining the wiring mode according to the specific wiring mode controlled by the current direct current power transmission system. And then the processor acquires the current value of the metal return line change-over switch of the direct current transmission system and carries out the next analysis.
The mode of acquiring the current value of the metal return line change-over switch by the processor is not unique, and in one embodiment, the current value can be acquired by arranging a corresponding current collector at the metal return line change-over switch for detection, and the processor only needs to receive the current value acquired or sent by the current collector in real time or actively access the current collector to acquire the corresponding current value. It is to be understood that the specific type of current collector is not exclusive, and in one embodiment, a dc shunt may be used as the current collector to measure the dc current, and then the measured dc current is transmitted to the processor through an optical fiber or the like.
It should be noted that the number and arrangement of the corresponding current collectors may be different for different types of dc transmission systems. For example, in one embodiment, one current collector is provided for each metal loop transfer switch to perform the current collection operation. That is, in the two-terminal dc power transmission system, only the current collector needs to be arranged at the metal return line change-over switch of the station 1, while the three-terminal hybrid dc power transmission system needs to be arranged at the metal return line change-over switches of the stations 2 and 3.
And step S200, judging whether the metal loop change-over switch is combined or not.
Specifically, when the processor analyzes that the dc power transmission system is in the single-pole metallic return line operating state, the dc power transmission system control method of this embodiment is triggered, and after the processor acquires the current value of the metallic return line change-over switch of the dc power transmission system, it is analyzed whether the metallic return line change-over switch is combined, and only when the metallic return line change-over switch is combined, the subsequent analysis operation is continuously performed, otherwise, the necessity of maintaining the dc operation by controlling the open circuit of the metallic return line change-over switch is not present.
It can be understood that the manner of determining whether the metal loop switches are combined is not unique, for example, in an embodiment, since the two different states of the metal loop switches, namely, the combined state and the open state, the electrical signals at the two ends of the metal loop switches are also different, and therefore, the method can be implemented by analyzing the voltage or the current at the two ends of the metal loop switches.
Further, in an embodiment, since two isolation switches are generally disposed at two ends of the metal loop transfer switch in the dc power transmission system, it can be understood that whether the metal loop transfer switch and the two isolation switches at the two ends of the metal loop transfer switch are combined may be determined, and the determination may be specifically distinguished according to different structures of the actual dc power transmission system.
Step S300, when the metal loop change-over switch is combined, whether the current value meets a preset condition is judged.
Specifically, the preset condition is a condition that a current value of the metal return line change-over switch reaches when an in-station grounding grid of the direct current transmission system is over-current due to the fact that the metal return line change-over switch is combined. Specifically, the test can be performed when the in-station grounding grid of the direct current transmission system is overcurrent by combining the metal return line change-over switch, and the test result is prestored in the processor, and the preset condition is directly called during subsequent analysis. When the processor analyzes in combination with the electric signals at the two ends of the metal return line change-over switch to obtain that the metal return line change-over switch is combined, the processor analyzes the current value obtained in real time and a preset condition to judge whether the current value meets the preset condition.
It can be understood that the specific type of the preset condition is not unique, as long as the current state flowing through the metal return line change-over switch when the in-station grounding grid of the direct current transmission system is overcurrent due to the combination of the metal return line change-over switch can be reasonably represented. For example, in one embodiment, the determination may be made as to whether the duration of the current flowing through the metallic return change-over switch is greater than a preset current threshold for a preset duration.
And step S400, controlling the metal loop change-over switch to be disconnected when the current value meets a preset condition.
Specifically, when the processor analyzes that the current value flowing through the metal return line change-over switch at this time meets the preset condition, it is indicated that the in-station grounding grid in the direct current transmission system is overcurrent due to the combination of the metal return line change-over switch at this time. In order to eliminate the overcurrent phenomenon and ensure that the direct current does not stop running, the processor only needs to open the metal return line change-over switch in the corresponding station. The processor is connected with the metal return wire change-over switch, and sends a disconnection control signal to the metal return wire change-over switch after detecting that the current value of the metal return wire change-over switch meets a preset condition, so that the metal return wire change-over switch is disconnected.
Referring to fig. 7, in an embodiment, after the step S300, the method further includes a step S500.
And step S500, when the current value does not meet the preset condition, controlling the metal return line change-over switch to maintain the current running state. And returning to the step of obtaining the current value of the metal return line change-over switch of the direct current transmission system.
Specifically, when the processor analyzes according to the acquired current value of the metal return line change-over switch, a situation that the current value does not meet a preset condition also occurs, which indicates that no combining of the metal return line change-over switch occurs at this time, so that an in-station grounding grid of the direct current transmission system is over-current, and at this time, there is no need to open the metal return line change-over switch, and the direct current transmission system only needs to maintain the current state to operate. Further, in order to ensure that the subsequent combining of the metal return line change-over switch occurs, so that the direct current transmission system can be detected in time when the station internal grounding grid of the direct current transmission system is in an overcurrent condition, the operation of obtaining the current value of the metal return line change-over switch of the direct current transmission system is returned at the moment, and the next round of analysis and judgment is executed.
Referring to fig. 8, in one embodiment, step S300 includes step S310. Step S310, determining whether the duration time of the current value greater than the preset current threshold reaches a preset duration time.
Specifically, the specific type of the preset condition is not unique, in this embodiment, when the preset condition is that the duration of the current value greater than the preset current threshold reaches the preset time, it is determined whether the duration of the current value greater than the preset current threshold reaches the preset time period, and when the duration of the current value greater than the preset current threshold reaches the preset time period, it is determined that the preset condition is met.
Further, referring to fig. 9 in combination, in an embodiment, the step S310 includes a step S311, a step S312, and a step S313.
Step S311, judging whether the current value is larger than a preset current threshold value; step S312, when the current value is greater than the preset current threshold value, timing is started with a preset time length; step 313, judging whether the current value is continuously greater than a preset current threshold value in the process of timing to reach the preset duration.
Specifically, the current value continuously being greater than the preset current threshold indicates that the duration of the current value being greater than the preset current threshold reaches the preset duration. When the current value meets the preset condition, firstly, whether the current value is larger than a preset current threshold value is judged, timing is started after the current value is larger than the preset current value, and whether the current value is still larger than the preset current threshold value is analyzed in the timing process until the timing reaches the preset duration. It is understood that, in the process, the obtaining operation of the current value is performed in real time, so as to realize the duration statistical operation that the current value is greater than the preset current threshold value. It should be noted that the preset duration is not unique in size as long as it is guaranteed that no false action will occur, and may be, for example, 100 ms to 500 ms in one embodiment.
Referring to fig. 9, in an embodiment, after the step S311, the method further includes a step S314.
In step S314, when the current value is less than or equal to the preset current threshold, the metal loop change-over switch is controlled to maintain the current operation state. And returns to the step of obtaining the current value of the metallic return line change-over switch of the dc transmission system (not shown).
Similarly, when the processor compares and analyzes the acquired current value with the preset current threshold, a situation that the current value is smaller than or equal to the preset current threshold also occurs, that is, a state that the current value does not meet the preset condition occurs, and at this time, the direct-current power transmission system only needs to maintain the current state to operate. Further, in order to ensure that the subsequent combining of the metal return line change-over switch occurs, so that the direct current transmission system can be detected in time when the station internal grounding grid of the direct current transmission system is in an overcurrent condition, the operation of obtaining the current value of the metal return line change-over switch of the direct current transmission system is returned at the moment, and the next round of analysis and judgment is executed.
Referring to fig. 9, in an embodiment, after the step S313, the method further includes a step S315.
And step S315, when the current value is not continuously larger than the preset current threshold value, controlling the metal return line change-over switch to maintain the current running state. And returns to the step of obtaining the current value of the metallic return line change-over switch of the dc transmission system (not shown).
Similarly, when the processor times a state in which the current value is greater than the preset current threshold, a situation may occur in which the current value is not continuously greater than the preset current threshold within a preset time period, and at this time, a state in which the current value does not satisfy the preset condition occurs, and the dc power transmission system only needs to maintain the current state to operate. Further, in order to ensure that the subsequent combining of the metal return line change-over switch occurs, so that the direct current transmission system can be detected in time when the station internal grounding grid of the direct current transmission system is in an overcurrent condition, the operation of obtaining the current value of the metal return line change-over switch of the direct current transmission system is returned at the moment, and the next round of analysis and judgment is executed.
Further, referring to fig. 10 in combination, in an embodiment, before the step S100, the method further includes a step S110 and a step S120.
Step S110, acquiring operation parameters of the direct current transmission system; and step S120, analyzing whether the direct current transmission system is in a single-pole metal loop working state or not according to the operation parameters.
Specifically, the scheme of this embodiment triggers execution only when the dc power transmission system operates in a single-pole metallic return wire connection mode. Therefore, before the operation is started, the processor firstly analyzes the operation parameters of the direct current transmission system to obtain whether the direct current transmission system operates in the wiring mode of the single-pole metal return wire. And if the direct current transmission system operates in the wiring mode of the single-pole metal return wire, executing subsequent control operation, and if the direct current transmission system does not operate in the wiring mode of the single-pole metal return wire, directly ending the control flow without executing the subsequent operation.
It should be noted that the operating parameters are not exclusive, as long as the wiring mode of the dc transmission system can be reasonably characterized, for example, in one embodiment, the current wiring mode can be obtained by collecting the position and current value of the relevant switch and the disconnecting switch of each station and analyzing the current value.
According to the method for controlling the direct current power transmission system under the metal return wire, when the direct current power transmission system operates in a single-pole metal return wire connection mode, analysis can be carried out by obtaining the state of the metal return wire change-over switch of the direct current power transmission system at the moment, and if the metal return wire change-over switch is combined and the current value flowing through the metal return wire change-over switch meets the preset condition, the metal return wire change-over switch is directly controlled to be open-circuited. Through the scheme, the metal return line change-over switch can be cut off only under the condition that the metal return line change-over switch is similar to be stolen, so that the fault is eliminated on the premise of not stopping the direct current power transmission system, and the direct current utilization rate is effectively improved.
Referring to fig. 11, a device for controlling a dc power transmission system under a metal return line includes a current value obtaining module 200, a combining analysis module 300, a current analysis module 400, and a circuit breaking control module 500.
The current value obtaining module 200 is configured to obtain a current value of a metal return line change-over switch of the dc power transmission system when the dc power transmission system is in a single-pole metal return line working state; the combining analysis module 300 is configured to determine whether a combining occurs in the metal return line switch; the current analysis module 400 is configured to determine whether the current value meets a preset condition when the metal return line change-over switch is combined; the open circuit control module 500 is used for controlling the metal loop change-over switch to open circuit when the current value satisfies a preset condition.
In one embodiment, the disconnection control module 500 is further configured to control the metallic return line switcher to maintain the current operation state when the current value does not satisfy the preset condition. And controls the current value obtaining module 200 to perform an operation of obtaining the current value of the metal return line changeover switch of the dc power transmission system.
In one embodiment, the current analysis module 400 is further configured to determine whether the duration that the current value is greater than the preset current threshold reaches a preset duration.
In one embodiment, the current analysis module 400 is further configured to determine whether the current value is greater than a preset current threshold; when the current value is greater than the preset current threshold value, timing by a preset time length; and judging whether the current value is continuously greater than a preset current threshold value or not in the process of timing to reach the preset duration.
In one embodiment, the current analysis module 400 is further configured to control the metallic loop switcher to maintain the current operation state when the current value is less than or equal to the preset current threshold value. And controls the current value obtaining module 200 to obtain the current value of the metal return line change-over switch of the dc power transmission system.
In one embodiment, the current analysis module 400 is further configured to control the metallic loop switch to maintain the current operation state when the current value is not continuously greater than the preset current threshold. And controls the current value obtaining module 200 to obtain the current value of the metal return line change-over switch of the dc power transmission system.
Referring to fig. 12, in an embodiment, the apparatus further includes a wiring analysis module 100 before the current value obtaining module 200. The wiring analysis module 100 is configured to obtain an operation parameter of the dc power transmission system; and analyzing whether the direct current transmission system is in a single-pole metal return wire working state or not according to the operation parameters.
For specific limitations of the dc power transmission system control apparatus under the metallic return wire, reference may be made to the above limitations on the dc power transmission system control method under the metallic return wire, and details are not described here again. All or part of each module in the direct current transmission system control device under the metal return wire can be realized by software, hardware and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.
When the direct current power transmission system operates in a single-pole metal return wire connection mode, the control device for the direct current power transmission system under the metal return wire can analyze the state of the metal return wire change-over switch of the direct current power transmission system at the moment by obtaining the state of the metal return wire change-over switch of the direct current power transmission system, and directly control the metal return wire change-over switch to be in an open circuit state if the metal return wire change-over switch is combined and the current value flowing through the metal return wire change-over switch meets the preset condition. Through the scheme, the metal return line change-over switch can be cut off only under the condition that the metal return line change-over switch is similar to be stolen, so that the fault is eliminated on the premise of not stopping the direct current power transmission system, and the direct current utilization rate is effectively improved.
Referring to fig. 13, a protection system for a dc power transmission system under a metal return line includes a current collector 10 and a processor 20, the current collector 10 is disposed on a metal return line change-over switch, the current collector 10 is connected to the processor 20, the current collector 10 is configured to collect a current value corresponding to the metal return line change-over switch and send the current value to the processor 20, and the processor 20 is configured to perform dc power transmission control according to the above-mentioned control method for the dc power transmission system.
Specifically, in this embodiment, the corresponding current collector 10 may be arranged at the metal loop change-over switch to perform detection to obtain the current value, and the processor 20 only needs to receive the current value collected or sent by the current collector 10 in real time, or actively access the current collector 10 to obtain the corresponding current value. It is to be understood that the specific type of the current collector 10 is not exclusive, and in one embodiment, a dc shunt may be used as the current collector 10 to measure the dc current, and then the measured dc current is transmitted to the processor 20 through an optical fiber or the like.
When the processor 20 analyzes that the dc power transmission system is in the single-pole metallic return line working state, the control method of the dc power transmission system is triggered, and after the processor 20 obtains the current value of the metallic return line change-over switch of the dc power transmission system, it is analyzed whether the metallic return line change-over switch is combined or not, only when the metallic return line change-over switch is combined, the subsequent analysis operation is continuously performed, otherwise, the necessity of maintaining the dc operation by controlling the open circuit of the metallic return line change-over switch is not present.
And when the metal loop change-over switch is combined, judging whether the current value meets a preset condition. The preset condition is a condition for representing that the current value of the metal return line change-over switch reaches when an in-station grounding network of the direct current transmission system is over-current due to the combination of the metal return line change-over switch. Specifically, the test result may be obtained by performing a test when the in-station grounding grid of the dc power transmission system is overcurrent by combining the metal return line transfer switches, and the test result is pre-stored in the processor 20, and the preset condition may be directly called during subsequent analysis. When the processor 20 analyzes the electrical signals at the two ends of the metallic return line change-over switch in combination to obtain that the metallic return line change-over switch has been combined, the processor 20 analyzes the current value obtained in real time and a preset condition to determine whether the current value meets the preset condition.
When the processor 20 analyzes that the current value flowing through the metallic return line change-over switch at this time meets the preset condition, it indicates that the in-station grounding grid in the direct current transmission system is overcurrent due to the combination of the metallic return line change-over switch at this time. To eliminate this overcurrent and at the same time ensure that the dc current is not turned off, the processor 20 only needs to turn off the metallic return line switch in the corresponding station. The processor 20 is connected to the metallic return line changeover switch, and sends a disconnection control signal to the metallic return line changeover switch after detecting that the current value of the metallic return line changeover switch satisfies a preset condition, so that the metallic return line changeover switch is disconnected.
According to the protection system for the direct current power transmission system under the metal return wire, when the direct current power transmission system operates in a single-pole metal return wire connection mode, analysis can be carried out by obtaining the state of the metal return wire change-over switch of the direct current power transmission system at the moment, and if the metal return wire change-over switch is combined and the current value flowing through the metal return wire change-over switch meets the preset condition, the metal return wire change-over switch is directly controlled to be opened. Through the scheme, the metal return line change-over switch can be cut off only under the condition that the metal return line change-over switch is similar to be stolen, so that the fault is eliminated on the premise of not stopping the direct current power transmission system, and the direct current utilization rate is effectively improved.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the claims. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A method for controlling a DC power transmission system under a metal return wire is characterized by comprising the following steps:
when the direct current transmission system is in a single-pole metal return wire working state, acquiring a current value of a metal return wire change-over switch of the direct current transmission system;
judging whether the metal return line change-over switch is combined or not;
when the metal return line change-over switch is combined, judging whether the current value meets a preset condition;
and when the current value meets the preset condition, controlling the metal return line change-over switch to be in an open circuit.
2. The method of claim 1, wherein after the step of determining whether the current value satisfies a predetermined condition when the metal return switch is combined, the method further comprises:
and when the current value does not meet the preset condition, controlling the metal return line change-over switch to maintain the current running state, and returning to the step of obtaining the current value of the metal return line change-over switch of the direct current transmission system.
3. The method of claim 1, wherein said step of determining whether said current value satisfies a predetermined condition comprises:
and judging whether the duration time of the current value greater than the preset current threshold reaches a preset duration.
4. A method according to claim 3, wherein said step of determining whether the duration of time that the current value is greater than a predetermined current threshold value reaches a predetermined duration comprises:
judging whether the current value is larger than a preset current threshold value or not;
when the current value is larger than the preset current threshold value, timing by a preset time length;
and in the process of judging whether the timing reaches the preset duration, whether the current value is continuously greater than the preset current threshold value or not is judged, and the fact that the current value is continuously greater than the preset current threshold value means that the duration of the current value greater than the preset current threshold value reaches the preset duration.
5. A method according to claim 4, wherein said step of determining whether said current value is greater than a predetermined current threshold value is followed by the step of:
and when the current value is smaller than or equal to a preset current threshold value, controlling the metal return line change-over switch to maintain the current running state, and returning to the step of obtaining the current value of the metal return line change-over switch of the direct current transmission system.
6. The method of claim 4, wherein after the step of determining whether the current value is continuously greater than a predetermined current threshold value during the time period of the determination reaching the predetermined duration, the method further comprises:
and when the current value is not continuously larger than the preset current threshold value, controlling the metal return line change-over switch to maintain the current running state, and returning to the step of obtaining the current value of the metal return line change-over switch of the direct current transmission system.
7. A method of transmitting DC power over a metallic return according to any one of claims 3 to 6, wherein the predetermined period is in the range of 100 to 500 milliseconds.
8. The method of claim 1, wherein said step of obtaining a current value for a metallic return line switcher of said dc power transmission system while said dc power transmission system is in a single pole metallic return line mode of operation further comprises:
acquiring operation parameters of a direct current transmission system;
and analyzing whether the direct current power transmission system is in a single-pole metal return wire working state or not according to the operation parameters.
9. A device for controlling a DC power transmission system under a metal return wire is characterized by comprising:
the current value acquisition module is used for acquiring the current value of a metal return wire change-over switch of the direct current transmission system when the direct current transmission system is in a single-pole metal return wire working state;
the combining analysis module is used for judging whether the metal return line change-over switch is combined or not;
the current analysis module is used for judging whether the current value meets a preset condition or not when the metal return line change-over switch is combined;
and the circuit breaking control module is used for controlling the metal return line change-over switch to be in circuit breaking when the current value meets the preset condition.
10. A protection system of a metal return line down direct current transmission system is characterized by comprising a current collector and a processor, wherein the current collector is arranged on a metal return line change-over switch and connected with the processor, the current collector is used for collecting a current value corresponding to the metal return line change-over switch and sending the current value to the processor, and the processor is used for carrying out direct current transmission control according to the control method of the metal return line down direct current transmission system of any one of claims 1-8.
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