CN115051331A - Direct-current line single-end-measurement stage type protection method independent of line boundary - Google Patents

Direct-current line single-end-measurement stage type protection method independent of line boundary Download PDF

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CN115051331A
CN115051331A CN202210810571.6A CN202210810571A CN115051331A CN 115051331 A CN115051331 A CN 115051331A CN 202210810571 A CN202210810571 A CN 202210810571A CN 115051331 A CN115051331 A CN 115051331A
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line
fault
protection
range
action
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CN115051331B (en
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何佳伟
李斌
谢仲润
周博昊
王文博
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Tianjin University
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Tianjin University
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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
    • 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
    • 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
    • H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
    • H02J3/00125—Transmission line or load transient problems, e.g. overvoltage, resonance or self-excitation of inductive loads
    • 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
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

The invention discloses a direct current line single-end quantity stage type protection method independent of line boundaries, which designs transient voltage energy
Figure 100004_DEST_PATH_IMAGE001
、
Figure 104556DEST_PATH_IMAGE002
Section action criterion, wherein the section I action fixed value is set according to an under-range, so that short-distance fault instantaneous action is realized;
Figure 483585DEST_PATH_IMAGE002
the section fixed value is set according to the over-range and is matched with the action fixed value of the I section of the next line protection, so that the reliable action of the long-distance fault of the protected line is realizedDoing and serving as far back-up protection of the next line; in addition, the method judges the protection by introducing the tripping transient overvoltage criterion of the circuit breaker
Figure 939974DEST_PATH_IMAGE002
And whether the section should be exported or not is judged, so that a trip signal is sent to a local circuit breaker to remove the fault when the protected line has a long-distance fault or the next line has a fault but the corresponding circuit breaker does not trip. The invention is suitable for a scene that no reactor is arranged at two ends of the line, and overcomes the defect that the existing direct current single-ended protection depends on line boundaries.

Description

Direct-current line single-end-measurement stage type protection method independent of line boundary
Technical Field
The invention relates to the field of relay protection of new energy and power systems, in particular to a protection method suitable for a large-scale new energy flexible direct transmission line.
Background
The construction of a novel power system mainly based on new energy is an important technical approach for realizing the strategic goal of 'double carbon'. The flexible direct-current power grid has outstanding advantages in aspects of large-scale new energy transmission, passive network power supply, regional power grid interconnection and the like, and becomes one of important trends of development of novel power systems. The fast and accurate direct current fault identification and isolation are core key technologies for guaranteeing safe and reliable operation of the flexible direct current power grid. Considering the requirement of action speed, the flexible direct-current power grid direct-current line is generally protected mainly by single-ended protection and backed by pilot protection.
The single-end protection of the direct-current line of the flexible direct-current power grid mainly refers to the protection of a conventional direct-current transmission line. For example, traveling wave protection based on the amount of change in polar wave and the rate of change in polar wave proposed by ABB, and traveling wave protection based on the rate of change in voltage proposed by SIEMENS achieve reliable identification of faults inside and outside the area by the absorption action of a dc filter on a fault traveling wave. Considering that the current-limiting reactors are generally additionally arranged at two ends of a direct-current line in the existing flexible direct-current power grid to limit fault current and also can form obvious retardation effect on the out-of-range fault traveling wave, the method can be also suitable for the flexible direct-current power grid. In addition, the document A novel single-ended-voltage-based protection scheme for flexible DC grid proposes to design flexible linear single-ended protection by using high-frequency transient components, and the document Non-unit traveling protection of HVDC grid using Levenberg-Marquarryoptimal adaptation designs the internal and external fault identification criteria by using the difference of current-limiting reactors and transition resistors on the distortion action of fault traveling waves, so that the transition resistance tolerance of protection can be obviously improved by the method.
However, it should be noted that the conventional single-ended protection of the dc transmission line and the single-ended protection of the flexible dc transmission line are both highly dependent on boundary elements installed at two ends of the line. With continuous scale promotion of the flexible direct-current power grid, complexity of a topological structure and diversification of application scenes, the condition that the current-limiting reactors are installed at two ends of the line cannot be guaranteed. For example, in the three-terminal flexible direct power transmission project of the nlilon of the southern power grid company, the current-limiting reactor is only installed at the outlet of the converter station in the northwest of the nlilon, and no reactor is installed on the outlet; when deep and far sea wind power is sent out and connected to the grid through flexible direct transmission, the method is limited by the size and weight constraints of an offshore platform, and a current-limiting reactor is not generally installed in an offshore converter station. In the above scenario, the protection method using the line boundary cannot be applied, and a new protection method for the dc line that does not depend on the line boundary needs to be researched.
Disclosure of Invention
Aiming at the problem that the protection of the single-end quantity of the direct-current line at present highly depends on line boundary elements, the invention provides a novel method for the stage protection of the single-end quantity of the direct-current line which does not depend on line boundaries, the reliable identification and upstream and downstream protection coordination of a fault line are realized through the design of a stage criterion and a transient overvoltage criterion, and the method can be applied to a flexible direct-current power grid scene without boundary elements at two ends of the line.
The invention is realized by the following technical scheme:
a single-end-amount stage type protection method of a direct current line independent of line boundaries comprises the following specific steps:
step 1, measuring the positive and negative voltage of the direct current lineU dcp 、U dcn And positive and negative electrode currentsI dcp 、I dcn Calculating the line mode voltageU lm Line mode currentI lm ；
Step 2, time setting windowT 1 The inner line mode voltage and the line mode current are respectively subjected to wavelet transformationAnd acquiring the detail coefficient of the layer 1 of the wavelet transformU lm_d_T1 (k 1 )、I lm_d_T1 (k 1 ) Representing the high frequency transient component of the line mode voltage and the high frequency transient component of the line mode current, respectively, wherein,k 1 =1, 2, 3, …, (T 1_ upper limit -T 1_ lower limit )/T s +1，T 1_ upper limit 、T 1_ lower limit Respectively represent time windowsT 1 The upper limit value and the lower limit value of (c),T s is the sampling period of the protection device;
step 3, fault direction judgment:
when max +U lm_d_T1 (k 1 )+I lm_d_T1 (k 1 )×Z Chf |/max|U lm_d_T1 (k 1 )-I lm_d_T1 (k 1 )×Z Chf |≥k set Judging that the fault is a back side fault, not sending a trip signal to a local breaker, and exiting the process;
when max +U lm_d_T1 (k 1 )+I lm_d_T1 (k 1 )×Z Chf |/max|U lm_d_T1 (k 1 )-I lm_d_T1 (k 1 )×Z Chf |<k set If the positive direction fault is judged, the subsequent process is continued;
wherein the content of the first and second substances,k set for the threshold value to be used as a criterion,Z Chf is the high frequency wave impedance of the direct current line;
step 4, designing transient voltage energy
Figure DEST_PATH_IMAGE001
、
Figure 725220DEST_PATH_IMAGE002
Section action criterion:
step 4.1, judging whether the fault occurs in
Figure 645640DEST_PATH_IMAGE001
Within the range of the segment:
when max +U lm_d_T1 (k 1 )| 2 ≥E hf_set1 If the fault is judged to be in the I section range, a tripping signal is sent to the local circuit breaker, and the process is exited, wherein,E hf_set1 criterion for transient voltage energy
Figure 881450DEST_PATH_IMAGE001
Setting a segment action value;
when max +U lm_d_T1 (k 1 )| 2 <E hf_set1 If the fault is not in the range of the section I, continuing to execute the step 4.2;
step 4.2, judging whether the fault is in
Figure 705180DEST_PATH_IMAGE002
Within the range of the segment:
when max +U lm_d_T1 (k 1 )| 2 <E hf_set2 The fault is not in I,
Figure 527598DEST_PATH_IMAGE002
Within the range of the section, no tripping signal is sent to the local circuit breaker, and the process is exited, wherein,E hf_set2 criterion for transient voltage energy
Figure 686047DEST_PATH_IMAGE001
I-section action setting value;
when max +U lm_d_T1 (k 1 )| 2 ≥E hf_set2 Is judged as
Figure 928809DEST_PATH_IMAGE002
If the fault is in the segment range, continuing to execute the step 5;
step 5, starting timing to judge whether the requirements are mett<t set : if it satisfiest<t set Continuously judging whether the conditions are metU dcp ≥U dc_set OrU dcn ≤-U dc_set ，U dc_set The threshold value is a value of a threshold value,t set for time delay: if it satisfiesU dcp ≥U dc_set OrU dcn ≤-U dc_set Then go on to step 6, if not, continue to executeU dcp ≥U dc_set OrU dcn ≤-U dc_set Whether or not the return satisfiest<t set Judging; if not satisfied witht<t set Judging that the fault is in the range of the section II and the circuit breaker at the next line outlet is not tripped, sending a tripping signal to a local circuit breaker, and exiting the process;
step 6, time setting windowT 2 Wavelet transformation is respectively carried out on the line mode voltage data and the line mode current data in the layer 1 to obtain detail coefficientsU lm_d_T2 (k 2 )、I lm_d_T2 (k 2 ) Respectively representing the high-frequency transient component of the line mode voltage and the high-frequency transient component of the line mode current; wherein the content of the first and second substances,k 2 =1, 2, 3, …, (T 2_ upper limit -T 2_ lower limit )/T s +1，T 2_ upper limit 、T 2_ lower limit Respectively represent time windowsT 2 The upper limit value and the lower limit value of (c),T s is the sampling period of the protection device;
step 7, judging the direction of the transient overvoltage source:
when max +U lm_d_T2 (k 2 )+I lm_d_T2 (k 2 )×Z Chf |/max|U lm_d_T2 (k 2 )-I lm_d_T2 (k 2 )×Z Chf |<k set If the transient overvoltage is transmitted from the positive direction, the fault is determined to be in the II section range, and the next circuit outlet breaker is tripped, no tripping signal is sent to the local breaker, and the process is exited;
when max +U lm_d_T2 (k 2 )+I lm_d_T2 (k 2 )×Z Chf |/max|U lm_d_T2 (k 2 )-I lm_d_T2 (k 2 )×Z Chf |≥k set And the judgment result shows that the transient overvoltage is propagated from the back side, the fault is judged to be in the range of the II section, the opposite-end circuit breaker is tripped, a tripping signal is sent to the local circuit breaker, and the process is exited.
Compared with the prior art, the method realizes reliable identification of the fault line and coordination of upstream and downstream protection through the design of the transient voltage energy stage type action criterion and the transient overvoltage criterion, is suitable for a scene without reactors at two ends of the line, and overcomes the defect that single-end protection of the existing direct current line depends on line boundaries.
Drawings
Fig. 1 is a schematic diagram of the propagation path of a transient overvoltage when a fault occurs at the near end of the next line (for protection M) in a four-terminal flexible dc power grid and the corresponding breaker has tripped.
Fig. 2 is a schematic diagram of the propagation path of transient overvoltage when a fault occurs at the far end of the line (for protection M) and the opposite-end breaker is tripped in the four-end flexible direct-current power grid.
Fig. 3 is a flowchart of a method for protecting a single-ended magnitude of a dc link in a step-wise manner without depending on a link boundary according to the present invention.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The embodiment is implemented according to the technical scheme of the invention, and a detailed specific implementation mode and an operation process are given, but the application scope of the invention is not limited to the following embodiment.
The invention designs the transient voltage energy
Figure 75888DEST_PATH_IMAGE001
、
Figure 277062DEST_PATH_IMAGE002
Section action criterion, wherein the section I action setting value is set according to an under-range, so that short-range fault instantaneous action is realized;
Figure 172075DEST_PATH_IMAGE002
setting the section setting value according to the over-range and finishing the action of the next line protection I sectionAnd the fixed values are matched, so that the long-distance fault reliable action of the protected line is realized, and the protected line is used as the long-distance backup protection of the next line. In addition, the method judges the protection by introducing the tripping transient overvoltage criterion of the circuit breaker
Figure 952949DEST_PATH_IMAGE002
And whether the section should be exported or not is judged, so that a trip signal is sent to a local circuit breaker to remove the fault when the protected line has a long-distance fault or the next line has a fault but the corresponding circuit breaker does not trip.
Fig. 1 is a schematic diagram showing the propagation path of transient overvoltage when a fault occurs at the near end of the next line (for protection M) in a four-terminal flexible dc power grid and the corresponding breaker has tripped. In the figure, Line 1 ~Line 4 For direct current transmission lines, S 1 ~S 4 Is a dc converter station. M, N are respectively Line 1 Protection of both sides. For protection M, transient voltage energy criterion
Figure 539DEST_PATH_IMAGE001
Setting the section according to 60-80% of the length of the protection line; transient voltage energy criterion
Figure 123347DEST_PATH_IMAGE002
Segment is then connected with Line 2 The protection P of the outlet is matched, and the action setting value is set to be slightly larger than the transient voltage energy of the protection P
Figure 256388DEST_PATH_IMAGE001
And (4) segment setting value. In this configuration, when the Line 1 When a fault occurs in the near zone, the transient voltage energy measured by the protection M is larger than
Figure 621380DEST_PATH_IMAGE001
Segment setting value and instantaneous action.
Line 1 Protecting the transient voltage energy of M when the near end of the far end or the next line outlet is in fault
Figure 461160DEST_PATH_IMAGE002
Section-by-section action, but delayt set And (7) an outlet. Wherein the content of the first and second substances,t set =(t relay +t DCCB )×K rel2 ，K rel2 a reliability factor slightly greater than 1. In a time delay periodt set In the interior, the protection M continuously monitors the transient overvoltage condition of the dc voltage. When the fault occurs in the Line 2 Line of 2 Will instantaneously exit and trip the corresponding dc breaker (DCCB) 23 ). In this case, it is known from the working principle of the dc circuit breaker that after the dc circuit breaker is tripped, the fault energy charges the snubber circuit rapidly, generating a transient overvoltage (the magnitude depends on the residual voltage parameter of the arrester). The parameters of the lightning arrester configured by the direct current breaker in the current practical engineering are combined, and the transient overvoltage is generally 1.5-2 times of the rated voltage of a direct current system. It should also be noted that in Line 2 Tripping circuit breaker (DCCB) in case of fault 23 ) And a complete power transmission Line (Line) is arranged between the protection M and the power transmission Line 1 ) So that the transient overvoltage can be in the form of electromagnetic waves along the Line 1 Quickly propagates to the protection M as shown in fig. 1. In other words, the guard M can be set for a set delay periodt set Transient overvoltage is detected. Moreover, for the protection M, this transient overvoltage is determined by the Line 1 Propagate from, i.e., from the positive direction. At the moment, the transient overvoltage source direction criterion reliably judges that the transient overvoltage comes from the positive direction. Therefore, it is judged that the failure is in
Figure 4136DEST_PATH_IMAGE002
Within the range of the segment, but in the next line, and the corresponding breaker has tripped, the protection M returns quickly, no longer sending a trip signal to the local breaker.
When the fault occurs in the Line 1 Far end (for protection M) it is clear that now the fault belongs to near end fault for protection N. Thus, the I-phase action instantaneous outlet of protection N trips the DC breaker (DCCB) at protection N 21 ) Transient overvoltage is generated. But need toIt is to be noted that this transient overvoltage occurs in the circuit breaker DCCB 21 Near one side of the bus, the circuit breaker cannot be along the Line due to the blocking effect of the circuit breaker and the short circuit point 1 Propagation, and therefore protection M in most cases is delayedt set The overvoltage cannot be detected. When protection M is in delayt set When the overvoltage can not be detected, the fault is determined to be
Figure 109627DEST_PATH_IMAGE002
In-range, and next line outlet circuit breaker (DCCB) 23 ) Not tripped, to local circuit breaker (DCCB) 12 ) And sending a trip signal and exiting the process. Only on Line 2 ~Line 4 Sum of length ofl line2 +l line3 +l line4 Is less thanl line1 +2X
Figure DEST_PATH_IMAGE003
+（K rel2 -1）×(t relay +t DCCB )×vIn the case of (A), (B)l line1 、l line2 、l line3 、l line4 Respectively represent Line 1 ~Line 4 The length of (a) of (b),K rel2 is a reliability factor that is slightly greater than 1,X
Figure 29041DEST_PATH_IMAGE003
for protecting M transient voltage energy
Figure 34912DEST_PATH_IMAGE002
The distance from the end of the protection range of the section criterion to the protection P,t relay for the action time of the relay in the DC protection device,t DCCB is the action time of the direct current breaker,vthe propagation speed of electromagnetic waves on the transmission Line), transient overvoltage follows the rest Line of the ring-shaped power grid 2 、Line 3 、Line 4 And will propagate to the guard M during the delay period. In this case, M can be protected in time delayt set Internal detection of transient overvoltagesAnd (6) pressing. However, as shown in fig. 2, in this case, the transient overvoltage propagates from the backside for protection M, and the transient overvoltage source criterion is determined to be the reverse direction source. Therefore, it is determined that the failure is
Figure 30681DEST_PATH_IMAGE002
And in the section range, the opposite-end circuit breaker is tripped, a tripping signal is sent to the local circuit breaker, and the process is exited.
The core principle of the invention is as above.
According to the principle, the invention provides a single-end-amount stage type protection method of a direct current line, which does not depend on line boundaries. As shown in fig. 3, a flowchart of a method for protecting a single-ended magnitude of a dc line in a stepwise manner without depending on a line boundary is provided, and the method includes the following specific steps:
step 1, measuring the positive and negative voltage of the direct current lineU dcp 、U dcn And positive and negative electrode currentsI dcp 、I dcn Calculating the line mode voltageU lm Line mode currentI lm The calculation formulas are respectively
Figure 138315DEST_PATH_IMAGE004
，
Figure DEST_PATH_IMAGE005
；
Step 2, time setting windowT 1 Wavelet transformation is respectively carried out on the line mode voltage and the line mode current in the wavelet transformation, and the detail coefficient of the 1 st layer of the wavelet transformation is obtainedU lm_d_T1 (k 1 )、I lm_d_T1 (k 1 ) Representing the high frequency transient component of the line mode voltage and the high frequency transient component of the line mode current, respectively, wherein,k 1 =1, 2, 3, …, (T 1_ upper limit -T 1_ lower limit )/T s +1，T 1_ upper limit 、T 1_ lower limit Respectively represent time windowsT 1 The upper limit value and the lower limit value of (c),T s is the sampling period of the protection device;
step 3, fault direction judgment:
when max +U lm_d_T1 (k 1 )+I lm_d_T1 (k 1 )×Z Chf |/max|U lm_d_T1 (k 1 )-I lm_d_T1 (k 1 )×Z Chf |≥k set Judging that the fault is a back side fault, not sending a trip signal to a local breaker, and exiting the process;
when max +U lm_d_T1 (k 1 )+I lm_d_T1 (k 1 )×Z Chf |/max|U lm_d_T1 (k 1 )-I lm_d_T1 (k 1 )×Z Chf |<k set If the positive direction fault is judged, the subsequent process is continued;
wherein the content of the first and second substances,k set setting value larger than 1, generally 1-2,Z Chf is the high frequency wave impedance of the direct current line;
step 4, designing transient voltage energy
Figure 845108DEST_PATH_IMAGE001
、
Figure 925060DEST_PATH_IMAGE002
Section action criterion:
step 4.1, judging whether the fault occurs in
Figure 75418DEST_PATH_IMAGE001
Within the range of the segment:
when max +U lm_d_T1 (k 1 )| 2 ≥E hf_set1 If the fault is judged to be in the I section range, a tripping signal is sent to the local circuit breaker, and the process is exited, wherein,E hf_set1 criterion for transient voltage energy
Figure 155501DEST_PATH_IMAGE001
Setting a segment action value;
when max +U lm_d_T1 (k 1 )| 2 <E hf_set1 If the fault is not in the range of the section I, continuing to execute the step 4.2;
step 4.2, judging whether the fault is in
Figure 416718DEST_PATH_IMAGE002
Within a range of sections
When max +U lm_d_T1 (k 1 )| 2 <E hf_set2 The fault is not in I,
Figure 600444DEST_PATH_IMAGE002
Within the range of the section, no tripping signal is sent to the local circuit breaker, and the process is exited, wherein,E hf_set2 criterion for transient voltage energy
Figure 390545DEST_PATH_IMAGE001
I-section action setting value;
when max +U lm_d_T1 (k 1 )| 2 ≥E hf_set2 Is judged as
Figure 207191DEST_PATH_IMAGE002
If the fault is in the segment range, continuing to execute the step 5;
step 5, starting timing to judge whether the requirements are mett<t set : if it satisfiest<t set Continuously judging whether the conditions are metU dcp ≥U dc_set OrU dcn ≤-U dc_set ，U dc_set The threshold value is a value of a threshold value,t set for time delay: if it satisfiesU dcp ≥U dc_set OrU dcn ≤-U dc_set Then go on to step 6, if not, continue to executeU dcp ≥U dc_set OrU dcn ≤-U dc_set Whether or not the return satisfiest<t set Judging; if not satisfied witht<t set Judging that the fault is in the range of the section II and the circuit breaker at the next line outlet is not tripped, sending a tripping signal to a local circuit breaker, and exiting the process;
step 6, time setting windowT 2 Wavelet transformation is respectively carried out on the line mode voltage data and the line mode current data in the layer 1 to obtain detail coefficientsU lm_d_T2 (k 2 )、I lm_d_T2 (k 2 ) Respectively representing the high-frequency transient component of the line mode voltage and the high-frequency transient component of the line mode current; wherein the content of the first and second substances,k 2 =1, 2, 3, …, (T 2_ upper limit -T 2_ lower limit )/T s +1，T 2_ upper limit 、T 2_ lower limit Respectively represent time windowsT 2 The upper limit value and the lower limit value of (c),T s is the sampling period of the protection device;
step 7, judging the direction of the transient overvoltage source:
when max +U lm_d_T2 (k 2 )+I lm_d_T2 (k 2 )×Z Chf |/max|U lm_d_T2 (k 2 )-I lm_d_T2 (k 2 )×Z Chf |<k set If the fault is in the section II range, the next circuit outlet breaker is tripped, and a tripping signal is not sent to the local breaker, and the process is exited;
when max +U lm_d_T2 (k 2 )+I lm_d_T2 (k 2 )×Z Chf |/max|U lm_d_T2 (k 2 )-I lm_d_T2 (k 2 )×Z Chf |≥k set And the judgment result shows that the transient overvoltage is propagated from the back side, namely the tripping transient overvoltage of the opposite side circuit breaker is propagated through the annular power grid, the fault is judged to be in the II section range, the opposite side circuit breaker is tripped, a tripping signal is sent to the local circuit breaker, and the process is exited.
In the above flow, specifically: .
The time window selection principle is as follows: setting the time window T 1 Setting a time window T for 1ms before the protection starting time and 2ms after the protection starting time 2 To be judged as
Figure 226094DEST_PATH_IMAGE002
Judging 1ms before the time of the fault in the segment range
Figure 280638DEST_PATH_IMAGE002
2ms after the moment of the segment-wide fault.
Transient voltage energy I,
Figure 772799DEST_PATH_IMAGE002
The section criterion setting value setting principle is as follows: the transient voltage energy criterion I-section action setting value is set according to an under-range, so that a short-range fault instantaneous action and an action setting value are realizedE hf_set1 Setting according to transient voltage energy when 60% -80% of the line has faults; transient voltage energy criterion
Figure 529271DEST_PATH_IMAGE002
The segment setting value is set according to the over-range and is matched with the action setting value of the I segment of the next line protection, so that the reliable action of the far-distance fault of the protected line is realized, and the segment setting value is used as the far back-up protection of the next line,E hf_set2 =K rel1 ×E hf _ set1_ next line protection ，K rel1 The reliability coefficient is slightly larger than 1, and is generally 1.1-1.2;
time delayt set =(t relay +t DCCB )·K rel2 ，t relay The relay action time of the direct current protection device,t DCCB the time for the action of the direct-current breaker,K rel2 the reliability coefficient is slightly larger than 1, and is generally 1.1-1.2.
Threshold valueU dc_set =K rel3 ×k residual ·U dcN /2。k residual The residual voltage ratio of an arrester in the direct current breaker (which can be obtained according to the parameters of the arrester) is generally 1.5-1.7;K rel3 for the reliability coefficient, the attenuation in the transmission process of the line is mainly considered, 0.8-0.85 is recommended,U dcN a dc voltage rating.

Claims (6)

1. A single-end-amount stage type protection method of a direct current line independent of line boundaries is characterized by comprising the following specific steps:
step 1, measuring the positive and negative voltage of the direct current lineU dcp 、U dcn And positive and negative electrode currentsI dcp 、I dcn Calculating the line mode voltageU lm Line mode currentI lm ；
Step 2, time setting windowT 1 Wavelet transformation is respectively carried out on the line mode voltage and the line mode current in the wavelet transformation, and the detail coefficient of the 1 st layer of the wavelet transformation is obtainedU lm_d_T1 (k 1 )、I lm_d_T1 (k 1 ) Representing the high frequency transient component of the line mode voltage and the high frequency transient component of the line mode current, respectively, wherein,k 1 =1, 2, 3, …, (T 1_ upper limit -T 1_ lower limit )/T s +1，T 1_ upper limit 、T 1_ lower limit Respectively represent time windowsT 1 The upper limit value and the lower limit value of (c),T s is the sampling period of the protection device;
step 3, fault direction judgment:
when max +U lm_d_T1 (k 1 )+I lm_d_T1 (k 1 )×Z Chf |/max|U lm_d_T1 (k 1 )-I lm_d_T1 (k 1 )×Z Chf |≥k set Judging that the fault is a back side fault, not sending a trip signal to a local breaker, and exiting the process;
when max +U lm_d_T1 (k 1 )+I lm_d_T1 (k 1 )×Z Chf |/max|U lm_d_T1 (k 1 )-I lm_d_T1 (k 1 )×Z Chf |<k set If the positive direction fault is judged, the subsequent process is continued;
wherein the content of the first and second substances,k set for the threshold value to be used as a criterion,Z Chf is the high frequency wave impedance of the direct current line;
step 4, designing transient voltage energy
Figure 872495DEST_PATH_IMAGE001
、
Figure 47124DEST_PATH_IMAGE002
Section action criterion:
step 4.1, judging whether the fault occurs in
Figure 913449DEST_PATH_IMAGE001
Within the range of the segment:
when max +U lm_d_T1 (k 1 )| 2 ≥E hf_set1 If the fault is judged to be in the I section range, a tripping signal is sent to the local circuit breaker, and the process is exited, wherein,E hf_set1 criterion for transient voltage energy
Figure 953955DEST_PATH_IMAGE001
Setting a segment action value;
when max +U lm_d_T1 (k 1 )| 2 <E hf_set1 If the fault is not in the range of the section I, continuing to execute the step 4.2;
step 4.2, judging whether the fault is in
Figure 563928DEST_PATH_IMAGE002
Within the range of the segment:
when max +U lm_d_T1 (k 1 )| 2 <E hf_set2 The fault is not in I,
Figure 593064DEST_PATH_IMAGE002
Within the range of the section, no tripping signal is sent to the local circuit breaker, and the process is exited, wherein,E hf_set2 criterion for transient voltage energy
Figure 381022DEST_PATH_IMAGE001
I section action setting value;
when max +U lm_d_T1 (k 1 )| 2 ≥E hf_set2 Is judged as
Figure 128398DEST_PATH_IMAGE002
If the fault is in the segment range, continuing to execute the step 5;
step 5, starting timing to judge whether the requirements are mett<t set : if it satisfiest<t set Continuously judging whether the conditions are metU dcp ≥U dc_set OrU dcn ≤-U dc_set ，U dc_set The threshold value is a value of a threshold value,t set for time delay: if it satisfiesU dcp ≥U dc_set OrU dcn ≤-U dc_set Then go on to step 6, if not, continue to executeU dcp ≥U dc_set OrU dcn ≤-U dc_set Whether or not the return satisfiest<t set Judging; if not satisfied witht<t set Judging that the fault is in the range of the section II and the circuit breaker at the outlet of the next line is not tripped, sending a tripping signal to a local circuit breaker, and exiting the process;
step 6, time setting windowT 2 Wavelet transformation is respectively carried out on the line mode voltage data and the line mode current data in the layer 1 to obtain detail coefficientsU lm_d_T2 (k 2 )、I lm_d_T2 (k 2 ) Respectively representing the high-frequency transient component of the line mode voltage and the high-frequency transient component of the line mode current; wherein the content of the first and second substances,k 2 =1, 2, 3, …, (T 2_ upper limit -T 2_ lower limit )/T s +1，T 2_ upper limit 、T 2_ lower limit Respectively represent time windowsT 2 The upper limit value and the lower limit value of (c),T s is the sampling period of the protection device;
step 7, judging the direction of the transient overvoltage source:
when max +U lm_d_T2 (k 2 )+I lm_d_T2 (k 2 )×Z Chf |/max|U lm_d_T2 (k 2 )-I lm_d_T2 (k 2 )×Z Chf |<k set If the transient overvoltage is transmitted from the positive direction, the fault is determined to be in the II section range, and the next circuit outlet breaker is tripped, no tripping signal is sent to the local breaker, and the process is exited;
when max +U lm_d_T2 (k 2 )+I lm_d_T2 (k 2 )×Z Chf |/max|U lm_d_T2 (k 2 )-I lm_d_T2 (k 2 )×Z Chf |≥k set And the transient overvoltage is propagated from the back side, the fault is judged to be in the II section range, the opposite-end circuit breaker is tripped, a tripping signal is sent to the local circuit breaker, and the process is exited.
2. The line boundary independent single-ended-quantity step-type protection method for the direct-current line according to claim 1, wherein in the step 4, the transient voltage energy criterion I-step action setting value is set according to an under-range, so that a short-range fault instantaneous action is realized, and the action setting value is setE hf_set1 Setting according to transient voltage energy when 60% -80% of lines have faults; transient voltage energy criterion
Figure 542062DEST_PATH_IMAGE002
The segment setting value is set according to the over-range and is matched with the action setting value of the I segment of the next line protection, so that the reliable action of the long-distance fault of the protected line is realized and the protected line is used as the long-distance backup protection of the next line,E hf_set2 =K rel1 ×E hf _ set1_ next line protection ，K rel1 Is a reliability factor.
3. The method of claim 1, wherein the step-wise protection of the single-ended magnitude of the DC link is independent of the link boundaryThe time window selection principle is as follows: setting the time window T 1 Setting the time window T for 1ms before the protection starting time and 2ms after the protection starting time 2 To be judged as
Figure 425705DEST_PATH_IMAGE002
Judging 1ms before the time of the fault in the segment range
Figure 679837DEST_PATH_IMAGE002
2ms after the moment of the segment-wide fault.
4. The method of claim 1, wherein the delay time is a single-ended magnitude step protection method for a DC line independent of line boundariest set =(t relay +t DCCB )×K rel2 ，t relay The relay action time of the direct current protection device,t DCCB the time for the action of the direct-current breaker,K rel2 is a reliability factor.
5. The method of claim 1, wherein the threshold value is set to a value that is independent of a line boundaryU dc_set =K rel3 ×k residual ·U dcN /2，k residual Is the residual voltage ratio of the lightning arrester in the direct current breaker,K rel3 in order to be a reliable factor,U dcN a dc voltage rating.
6. The method of claim 1, wherein the line mode voltage is a single-ended magnitude step protection of a DC line independent of line boundariesU lm The line mode currentI lm Are respectively calculated as
Figure 648930DEST_PATH_IMAGE003
，
Figure 600706DEST_PATH_IMAGE004
。
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