CN110071475B - Reclosing method and reclosing device - Google Patents
Reclosing method and reclosing device Download PDFInfo
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- CN110071475B CN110071475B CN201910233284.1A CN201910233284A CN110071475B CN 110071475 B CN110071475 B CN 110071475B CN 201910233284 A CN201910233284 A CN 201910233284A CN 110071475 B CN110071475 B CN 110071475B
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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
- H02H3/02—Details
- H02H3/06—Details with automatic reconnection
- H02H3/066—Reconnection being a consequence of eliminating the fault which caused disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
- H02H7/268—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured for dc systems
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
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- Direct Current Feeding And Distribution (AREA)
- Driving Mechanisms And Operating Circuits Of Arc-Extinguishing High-Tension Switches (AREA)
Abstract
The invention provides a reclosing method and a reclosing device, wherein the reclosing method comprises the following steps: and after the breaker trips, judging whether a fault line suffers from transient faults, if so, carrying out reclosing operation, and if not, not carrying out reclosing operation. The reclosing method provided by the invention judges whether the fault line suffers from transient faults or not, does not perform switching-on operation on non-transient faults (permanent faults), and avoids blind reclosing after the circuit breaker trips.
Description
Technical Field
The invention relates to the technical field of direct current transmission, in particular to a reclosing method and a reclosing device for a circuit breaker of a direct current transmission system with a receiving end of an LCC-VSC series-parallel connection type.
Background
The power distribution network is an important component of a power system, and faults of a power distribution line frequently occur due to the fact that the power distribution network is complex in structure, wide in distribution and low in insulation level and has many defects in technical management and operation maintenance. The faults of the distribution line mainly comprise two types of transient faults and permanent faults, wherein most faults are transient, and in order to reduce power failure accidents of the line caused by transient faults and the like and improve power supply reliability, an automatic reclosing device is generally adopted in a power distribution system.
The automatic reclosing device plays an important role in ensuring safe power supply and stable operation of an electric power system, however, the automatic reclosing device in the prior art is used for reclosing blindly after a breaker trips, and when the automatic reclosing device is superposed on a permanent fault, the automatic reclosing device often causes greater harm to the electric power system and electrical equipment.
Therefore, how to avoid the automatic reclosing device from performing blind reclosing after the circuit breaker trips and reduce the fault loss while ensuring the power supply continuity is a problem to be solved by those skilled in the art.
Disclosure of Invention
The invention aims to provide a reclosing method and a reclosing device, which can avoid blind reclosing after a breaker trips.
In order to solve the above technical problems, the present invention provides a reclosing method for performing a reclosing operation after a circuit breaker is tripped, the circuit breaker being installed in a direct current transmission system of which a receiving end is of an LCC-VSC series-parallel type, wherein,
the receiving end of the direct current transmission system with the receiving end of the LCC-VSC hybrid type comprises an LCC converter station and a plurality of VSC converter stations electrically connected with the LCC converter station;
the circuit breaker includes: the direct current transmission system comprises a plurality of connection points, a first line and a second line which are in one-to-one correspondence with the connection points, a third line and a fourth line, wherein one of the connection points is used for being electrically connected with the LCC converter station, the other connection points are used for being electrically connected with the VSC converter station, each connection point is respectively connected to two ends of the third line through the first line and the second line, the fourth line is connected to two ends of the third line in parallel, the first line is used for conducting load current when the direct current transmission system normally operates, the second line is used for isolating current and voltage among the connection points, the third line is used for breaking fault current when the direct current transmission system fails, and the fourth line is used for breaking overvoltage when the direct current transmission system fails and absorbing energy stored by an inductive element, the first line comprises a first fast mechanical switch and a first power electronic switch which are connected in series, the second line comprises a second fast mechanical switch and a diode which are connected in series, the anode of the diode is connected with the third line, the third line comprises a plurality of second power electronic switches which are connected in series, and the fourth line comprises a non-linear resistor or an arrester;
the tripping method of the circuit breaker comprises the following steps:
a1, determining a fault line;
a2, opening a first rapid mechanical switch corresponding to a fault line and a second rapid mechanical switch corresponding to a non-fault line, and simultaneously, turning off the first power electronic switch and turning on the second power electronic switch;
a3, turning off the second power electronic switch after the distance between the moving contact and the static contact of the first quick mechanical switch corresponding to the fault line and the second quick mechanical switch corresponding to the non-fault line reaches a preset value;
a4, after the fault current is absorbed by the fourth line, opening a second quick mechanical switch corresponding to the fault line and closing the second quick mechanical switch corresponding to the non-fault line;
according to the reclosing method, after the breaker trips, whether a fault line suffers from transient faults or not is judged, if yes, reclosing operation is carried out, and if not, reclosing operation is not carried out.
Further, judging whether the fault line encounters a transient fault specifically comprises the following steps:
b1: after the fault line is dissociated, closing the second quick mechanical switch corresponding to the fault line;
b2: detecting a fault line voltage;
b3: judging whether the fault line encounters transient faults or not according to the voltage of the fault line: if the voltage of the fault line rises to the direct current voltage of the system rapidly, the fault line suffers from transient faults, and if the voltage of the fault line is maintained to be close to 0, the fault line suffers from non-transient faults.
Further, in the step B1, the method for freeing the fault line includes: the second fast mechanical switch corresponding to the faulty line is maintained in an open state for a first period of time.
Further, the reclosing operation is: and closing the first quick mechanical switch corresponding to the fault line.
Further, if the faulty line suffers from a non-transient fault, a warning message is issued.
The invention also provides a reclosing device for reclosing operation after tripping of a circuit breaker, wherein the circuit breaker is arranged in a direct current transmission system with a receiving end of an LCC-VSC series-parallel connection type, wherein,
the receiving end of the direct current transmission system with the receiving end of the LCC-VSC hybrid type comprises an LCC converter station and a plurality of VSC converter stations electrically connected with the LCC converter station;
the circuit breaker includes: the direct current transmission system comprises a plurality of connection points, a first line and a second line which are in one-to-one correspondence with the connection points, a third line and a fourth line, wherein one of the connection points is used for being electrically connected with the LCC converter station, the other connection points are used for being electrically connected with the VSC converter station, each connection point is respectively connected to two ends of the third line through the first line and the second line, the fourth line is connected to two ends of the third line in parallel, the first line is used for conducting load current when the direct current transmission system normally operates, the second line is used for isolating current and voltage among the connection points, the third line is used for breaking fault current when the direct current transmission system fails, and the fourth line is used for breaking overvoltage when the direct current transmission system fails and absorbing energy stored by an inductive element, the first line comprises a first fast mechanical switch and a first power electronic switch which are connected in series, the second line comprises a second fast mechanical switch and a diode which are connected in series, the anode of the diode is connected with the third line, the third line comprises a plurality of second power electronic switches which are connected in series, and the fourth line comprises a non-linear resistor or an arrester;
the tripping method of the circuit breaker comprises the following steps:
a1, determining a fault line;
a2, opening a first fast mechanical switch corresponding to a fault line and a second fast mechanical switch corresponding to a non-fault line, and simultaneously turning off the first power electronic switch and turning on the second power electronic switch;
a3, turning off the second power electronic switch after the distance between the moving contact and the static contact of the first quick mechanical switch corresponding to the fault line and the second quick mechanical switch corresponding to the non-fault line reaches a preset value;
a4, after the fault current is absorbed by the fourth line, opening a second quick mechanical switch corresponding to the fault line and closing the second quick mechanical switch corresponding to the non-fault line;
the reclosing device includes:
the fault judging unit is used for judging whether a fault line suffers from transient faults or not after the breaker trips;
and the reclosing operation unit is used for carrying out reclosing operation when the fault line encounters transient fault and not carrying out reclosing operation when the fault line encounters non-transient fault.
Further, the failure determination unit includes:
the first driving module is used for closing the second quick mechanical switch corresponding to the fault line after the fault line is dissociated;
the detection module is used for detecting the voltage of the fault line;
the judging module is used for judging whether the fault line suffers from transient faults or not according to the voltage of the fault line: if the voltage of the fault line rises to the direct current voltage of the system rapidly, the fault line suffers from transient faults, and if the voltage of the fault line is maintained to be close to 0, the fault line suffers from non-transient faults.
Further, in the first driving module, the method for freeing the fault line includes: the second fast mechanical switch corresponding to the faulty line is maintained in an open state for a first period of time.
Further, the reclosing operation unit is used for: and closing the first quick mechanical switch corresponding to the fault line.
Further, the system also comprises a warning unit which is used for sending out warning information when the fault line encounters non-transient faults.
The reclosing method provided by the invention judges whether a fault line suffers from transient faults or not, and does not carry out switching-on operation on non-transient faults (permanent faults), thereby avoiding blind reclosing after the circuit breaker trips.
Drawings
Fig. 1 is a schematic structural diagram of a direct-current transmission system with a receiving end of an LCC-VSC series-parallel connection type;
fig. 2 is a schematic structural diagram of a direct-current transmission system with a circuit breaker installed at a receiving end and of an LCC-VSC series-parallel type;
fig. 3 is a schematic structural diagram of the circuit breaker;
fig. 4 is a schematic view of the current flow path when the circuit breaker is in the first mode of operation;
fig. 5 is a schematic view of the current flow path when the circuit breaker is in a second mode of operation;
fig. 6 is a timing diagram of the circuit breaker switching from the first mode of operation to the second mode of operation;
fig. 7 is a schematic diagram of the current flow path after a fault occurs during switching of the circuit breaker from the first mode of operation to the second mode of operation;
fig. 8 is a schematic diagram of the current flow path during the transfer of fault current during switching of the circuit breaker from the first mode of operation to the second mode of operation;
fig. 9 is a schematic diagram of the current flow path after the third circuit is opened during the switching of the circuit breaker from the first operation mode to the second operation mode;
fig. 10 is a schematic view of the current flow path after fault isolation during switching of the circuit breaker from the first mode of operation to the second mode of operation;
FIG. 11 is a schematic diagram of a line voltage equivalent circuit during a transient fault;
FIG. 12 is a schematic diagram of the equivalent circuit of line voltage in case of permanent metal ground fault;
fig. 13 is a schematic diagram of the equivalent circuit of the line voltage in case of permanent high-resistance ground fault.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
The first embodiment is as follows:
the reclosing method provided by the invention is used for reclosing operation after the circuit breaker trips, so that the circuit breaker is introduced firstly in the embodiment.
A circuit breaker is installed in a direct-current transmission system with a receiving end in a LCC-VSC (liquid crystal control-Voltage Converter) series-parallel connection mode, the structure of the direct-current transmission system with the receiving end in the LCC-VSC series-parallel connection mode is shown in figure 1, a sending end adopts the LCC (Line Committed Converter), and a receiving end adopts the direct-current transmission system with the LCC and the VSC (Voltage Source Converter) series-parallel connection mode. As shown in fig. 2 and 3, the receiving end of the dc transmission system with an LCC-VSC series-parallel receiving end includes: an LCC converter station and a plurality of VSC converter stations electrically connected to said LCC converter station, the circuit breaker comprising: the direct current transmission system comprises a plurality of connection points 100, a first line 200 and a second line 300 which are in one-to-one correspondence with the connection points 100, a third line 400 and a fourth line 500, wherein one connection point 100 in the plurality of connection points 100 is used for being electrically connected with an LCC converter station, the rest connection points 100 are used for being electrically connected with a VSC converter station, each connection point 100 is respectively connected to two ends of the third line 400 through the first line 200 and the second line 300, the fourth line 500 is connected to two ends of the third line 400 in parallel, the first line 200 is used for conducting load current when the direct current transmission system normally operates, the second line 300 is used for isolating current and voltage among the plurality of connection points 100, the third line 400 is used for isolating fault current when the direct current transmission system fails, and the fourth line 500 is used for isolating overvoltage and absorbing energy stored by inductive elements when the direct current transmission system fails.
Specifically, the first line 200 comprises a first fast mechanical switch and a first power electronic switch connected in series, the first fast mechanical switch functioning as: when the breaker normally operates, the breaker is ensured to operate in a low-loss state; during the fault breaking process, the first quick mechanical switch is opened to ensure the establishment of the breaking voltage, so that the fault current is forced to drop to zero. The first power electronic switch functions as: when the device is in normal operation, the load current is conducted; in the fault breaking process, the first power electronic switch is turned off, and the current is forced to be transferred from the first line 200 to the third line 400, so that the first fast mechanical switch can realize arc-free opening. The second circuit 300 comprises a second fast mechanical switch and a diode connected in series, the anode of the diode being connected to the third circuit 400, the diode functioning as: when switching the circuit breaker to the second mode of operation in the following, need not go to control the switching on or off of diode, simplified the flow, simultaneously, can reduce cost using the diode, in addition, because the reverse blocking effect of diode, when breaking down on the circuit, the second circuit 300 that non-fault circuit corresponds can not stay the fault current, can not the arcing when jumping off the quick mechanical switch of second that non-fault circuit corresponds. The third circuit 400 comprises a plurality of second power electronic switches in series, the third circuit 400 enabling a final shut-off of the fault current. The fourth line 500 comprises a non-linear resistor or arrester for breaking the overvoltage and absorbing the energy stored by the inductive element in case of a fault in the dc transmission system. The action speed of the circuit breaker mainly depends on the medium strength recovery speed of the first quick mechanical switch and the second quick mechanical switch after opening, and the first power electronic switch and the diode can ensure that the first quick mechanical switch and the second quick mechanical switch realize arc-free opening, so that the medium strength can be quickly recovered after the first quick mechanical switch and the second quick mechanical switch are opened. The first and second power electronic switches may be insulated gate bipolar transistors.
The method of tripping the circuit breaker is described below, and for convenience of the following description, the various components of the circuit breaker are named: as shown in fig. 2 and 3, the circuit breaker includes:
the system comprises m wiring points, namely a wiring point LCC, a wiring point VSC _1, a wiring point VSC _2, a wiring point … … and a wiring point VSC _ m-1, wherein the wiring point LCC is electrically connected with a converter station LCC, and the wiring points VSC _1, VSC _2, … … and VSC _ m-1 are electrically connected with the converter stations VSC1, VSC2, … … and VSCm-1 respectively;
the first quick mechanical switches CB _1, CB _2, … … and CB _ m are in one-to-one correspondence with the m wiring points respectively;
the first power electronic switches LSC _1, LSC _2, … … and LSC _ m are in one-to-one correspondence with the m wiring points respectively;
the second quick mechanical switches K _1, K _2, … … and K _ m are in one-to-one correspondence with the m wiring points respectively;
diodes D _1, D _2, … … and D _ m which are respectively in one-to-one correspondence with the m wiring points;
a third line 400;
and a fourth line 500.
Assuming that a line where a wiring point VSC _1 is located has a fault, the tripping method comprises the following steps: when the direct current transmission system normally operates, the circuit breaker is kept in a first working mode; when a line fault occurs in the direct current transmission system, the circuit breaker is switched from the first working mode to the second working mode. When the circuit breaker is in the first operating mode, the first fast mechanical switches CB _1, CB _2, … …, CB _ m and the second fast mechanical switches K _1, K _2, … …, K _ m are all in a closed state, the first power electronic switches LSC _1, LSC _2, … …, LSC _ m are all in a conductive state, the second power electronic switches in the third line 400 are in a latched state, current cannot flow between the respective second lines 300, current flows from the converter station LCC through the respective first lines 200 into the converter stations VSC1, VSC2, … …, VSCm-1, and the current flow path in the first operating mode is as shown in fig. 4 (the segment with arrows in the figure represents the current path). Since the conduction voltage drop of the first line 200 is usually 2-3V, the operation loss of the circuit breaker is only several kW.
When the circuit breaker is in the second working mode, the first fast mechanical switch and the second fast mechanical switch corresponding to the non-fault line are both in a closed state, the first power electronic switch is both in a conducting state, namely, the first fast mechanical switches CB _1, CB _3, … …, CB _ m and the second fast mechanical switches K _1, K _3, … …, K _ m are all in a closed state, the first power electronic switches LSC _1, LSC _3, … …, LSC _ m are all in a conductive state, the second power electronic switch in the third circuit 400 is in a latched state, the first quick mechanical switch and the second quick mechanical switch corresponding to the fault line are in an open state, that is, the first fast mechanical switch CB _2 is in the disconnecting state, the second fast mechanical switch K _2 is in the disconnecting state, and the current flow path in the second operation mode is as shown in fig. 5 (the line segment with the arrow in the figure indicates the current path).
Fig. 6 is a timing chart of switching the circuit breaker from the first operating mode to the second operating mode, where the abscissa is time and the ordinate is current, and fig. 7 to 10 are schematic diagrams of current paths during switching the circuit breaker from the first operating mode to the second operating mode, and the method for specifically switching the circuit breaker to the second operating mode includes the following steps:
at the time t1, a fault occurs, and after the fault is detected, the direct-current protection sends a circuit command of tripping the wiring point VSC _1 to the circuit breaker;
at time t2, the dc breaker controller first sends an open command to the first fast mechanical switch CB _2 corresponding to the faulty line and the second fast mechanical switches K _1, K _3, … …, and K _ m corresponding to the non-faulty line, and at the same time sends a turn-on command to the second power electronic switch in the third line 400, and sends a lock-off command to the first power electronic switch LCS _2, and under the action of turn-off overvoltage at both ends of the first power electronic switch LCS _2, the fault current is transferred from the first line 200 corresponding to the faulty line to the second line 300 corresponding to the third line 400 and the faulty line, as shown in fig. 8, the current can be transferred within hundreds of microseconds, and due to the existence of contact inertia and contact over-travel, the fast mechanical switch contacts are really separated 1ms after receiving the open command, and at this time, the current transfer is completed;
at the time of t3, the arc-free opening is realized by the first quick mechanical switch CB _2 of the fault line and the second quick mechanical switches K _1, K _3, … … and K _ m of the non-fault line;
at time t4, when the distances between the moving contacts of the first fast mechanical switch CB _2 and the second fast mechanical switches K _1, K _3, … …, K _ m reach a predetermined value, a lock command is sent to the second power electronic switch in the third circuit 400, a trip command is sent to the second fast mechanical switch K _2, and the current is transferred from the third circuit 400 to the fourth circuit 500, see fig. 9, at which time the first fast mechanical switch CB _2 and the second fast mechanical switches K _1, K _3, … …, K _ m need to bear the residual voltage of the fourth circuit 500, generally 1.5 p.u, and when the residual energy stored in the dc system is almost absorbed by the fourth circuit 500, the current is transferred from the fourth circuit 500 back to the buffer absorption circuit of the second power electronic switch in the third circuit 400, so as to generate residual current due to the second fast mechanical switches K _1, K _3, … …, K _ m is already open, so that no overvoltage will occur across the diode when the second power electronic switch in the third line 400 is locked, reducing the requirements for the diode;
at time t5, the second fast mechanical switch K _2 has implemented the opening, the residual current is cut off, and a closing command is sent to the second fast mechanical switches K _1, K _3, … …, K _ m to restore the system to normal operation.
As shown in fig. 7, after a fault occurs, the LCC converter station and the remaining VSC converter stations feed fault current to the fault point through the first power electronic switch LCS _2, the fault current only flows through each first line 200, the current direction of the fault current is shown in fig. 7, after receiving a switching-off command, the first power electronic switch LCS _2 is locked, the fault current is transferred from the first power electronic switch LCS _2 to the third line 400, the current direction of the fault current is shown in fig. 8, the third line 400 is disconnected, the fault current is isolated, the current is transferred from the third line 400 to another connection point, the current direction of the fault current is shown in fig. 9, the second fast mechanical switch K _2 is switched off, the system resumes normal operation, and the current flowing through the connection point VSC _1 is distributed to the remaining connection points, and the current direction is shown in fig. 10.
When a plurality of direct current lines have faults, the isolation of the fault lines can be realized according to the switching-off sequence.
According to the reclosing method provided by the invention, after the breaker trips, whether a fault line suffers from transient faults or not is judged, if yes, reclosing operation is carried out, and if not, reclosing operation is not carried out. In this embodiment, a specific method for determining whether the faulty line encounters the transient fault is not limited, and any method may be used as long as it can determine whether the faulty line encounters the transient fault.
In an optional implementation manner of this embodiment, the determining whether the faulty line encounters a transient fault specifically includes the following steps:
b1: after the fault line is dissociated, closing the second quick mechanical switch corresponding to the fault line;
when transient faults occur, the circuit breaker is tripped quickly, a second quick mechanical switch corresponding to a fault line is opened in the tripping process, direct-current voltage is applied to two ends of the second quick mechanical switch corresponding to the fault line, a fault point begins to be dissociated, if the second quick mechanical switch corresponding to the fault line is closed in the dissociating period, the direct-current voltage is immediately applied to the fault point, the fault point can be caused to be re-ignited, and therefore the second quick mechanical switch corresponding to the fault line is closed after the fault point is dissociated;
b2: detecting a fault line voltage;
b3: judging whether the fault line encounters transient faults or not according to the voltage of the fault line: if the voltage of the fault line rises to the direct current voltage of the system rapidly, the fault line suffers from transient faults, and if the voltage of the fault line is maintained to be close to 0, the fault line suffers from non-transient faults.
Theoretical analysis on the effectiveness of this embodiment:
the equivalent circuit of the direct current system voltage during transient fault is shown in fig. 11, the circuit breaker is equivalent to a capacitor C1 of the uF level, the fault point is equivalent to a capacitor C2 of the nF level, according to the circuit principle, the total voltage across the series circuit of capacitors is equal to the sum of the divided voltages across each capacitor, the voltage that each capacitor bears when the capacitors are connected in series is inversely proportional to its capacitance (since the amount of charge carried by each capacitor is equal in a capacitor series circuit, the higher the capacitance the lower the voltage that the capacitor bears, the higher the voltage that the capacitance the smaller the capacitance the higher the voltage that the capacitor bears), thus, after closing the second fast mechanical switch corresponding to the faulty line, both the LCC converter station and the VSC converter station charge both of these equivalent capacitances, because the equivalent capacitance of the circuit breaker is far greater than that of a fault point, the circuit breaker bears less voltage after charging, and most of the voltage is borne by the fault point.
Similarly, when a permanent metal ground fault occurs, after the fault line is dissociated, the second fast mechanical switch corresponding to the fault line is closed, the direct-current system voltage equivalent loop is shown in fig. 12, since the voltage at the fault point is 0, the voltages of the LCC converter station and the VSC converter station are all borne by the circuit breaker, and at this time, the third line 400 in the circuit breaker is not triggered, so that the fault point cannot reignite.
When a permanent high-resistance grounding fault occurs, after the fault line is dissociated, the second quick mechanical switch corresponding to the fault line is closed, a direct-current system voltage equivalent loop is shown in fig. 13, as the current in the loop is small, the voltage at the fault point is close to 0, the voltages of the LCC converter station and the VSC converter station are all born by the circuit breakers, and at the moment, the third line 400 in the circuit breakers is not triggered, so that the fault point cannot be reignited.
According to the analysis, after the fault line is dissociated, the second quick mechanical switch corresponding to the fault line is closed, the voltage of the fault line is measured, if the voltage of the fault line is quickly increased to the direct current voltage of the system, the fault line is judged to be a transient fault, and if the voltage of the fault line is kept near 0, the fault line is judged to be a permanent fault.
The above embodiment has the following beneficial effects:
the method can reliably identify the fault property by judging the line voltage, and is convenient to operate;
the reclosing time can be adaptively adjusted according to the voltage values at the two ends of the main breaker;
the method has better adaptability to permanent high-resistance ground faults;
since the third line 400 is not turned on in the reclosing process, the overcurrent of the third line 400 is not caused.
In an optional implementation manner of this embodiment, in step B1, the method for dissociating the faulty line includes: the second fast mechanical switch corresponding to the faulty line is caused to remain in the open state for a first period of time, which may be 200 ms.
In an optional implementation manner of this embodiment, the reclosing operation is: and closing the first quick mechanical switch corresponding to the fault line.
In an optional implementation manner of this embodiment, if the faulty line suffers from a non-transient fault, a warning message is issued to notify the maintenance personnel of the coming process.
Example two:
the embodiment provides a reclosing device, which is used for reclosing operation after a breaker trips, wherein the structure and the tripping method of the breaker are the same as those of the first embodiment, and are not described again here.
The working principle of the present embodiment is the same as that of the first embodiment, and can be understood by referring to the first embodiment.
Reclosing device includes:
the fault judging unit is used for judging whether a fault line suffers from transient faults or not after the breaker trips;
and the reclosing operation unit is used for carrying out reclosing operation when the fault line encounters transient fault and not carrying out reclosing operation when the fault line encounters non-transient fault.
In an optional implementation manner of this embodiment, the fault determining unit includes:
the first driving module is used for closing the second quick mechanical switch corresponding to the fault line after the fault line is dissociated;
the detection module is used for detecting the voltage of the fault line;
the judging module is used for judging whether the fault line suffers from transient faults or not according to the voltage of the fault line: if the voltage of the fault line rises to the direct current voltage of the system rapidly, the fault line suffers from transient faults, and if the voltage of the fault line is maintained to be close to 0, the fault line suffers from non-transient faults.
In an optional implementation manner of this embodiment, in the first driving module, a method for dissociating a fault line includes: the second fast mechanical switch corresponding to the faulty line is maintained in an open state for a first period of time.
In an optional implementation manner of this embodiment, the reclosure operation unit performs a reclosure operation by: and closing the first quick mechanical switch corresponding to the fault line.
In an optional implementation manner of this embodiment, the system further includes a warning unit, configured to issue a warning message when the faulty line encounters a non-transient fault.
The scope of the invention is not limited thereto. The equivalent substitutions or changes made by the person skilled in the art on the basis of the present invention are all within the protection scope of the present invention. The protection scope of the invention is subject to the claims.
Claims (10)
1. A reclosing method is used for reclosing operation after tripping of a circuit breaker, the circuit breaker is installed in a direct current transmission system of which the receiving end is of an LCC-VSC series-parallel connection type, wherein,
the receiving end of the direct current transmission system with the receiving end being an LCC-VSC series-parallel type comprises an LCC converter station and a plurality of VSC converter stations electrically connected with the LCC converter station;
the circuit breaker includes: the direct current transmission system comprises a plurality of connection points, a first line and a second line which are in one-to-one correspondence with the connection points, a third line and a fourth line, wherein one of the connection points is used for being electrically connected with the LCC converter station, the other connection points are used for being electrically connected with the VSC converter station, each connection point is respectively connected to two ends of the third line through the first line and the second line, the fourth line is connected to two ends of the third line in parallel, the first line is used for conducting load current when the direct current transmission system normally operates, the second line is used for isolating current and voltage among the connection points, the third line is used for breaking fault current when the direct current transmission system fails, and the fourth line is used for breaking overvoltage when the direct current transmission system fails and absorbing energy stored by an inductive element, the first line comprises a first fast mechanical switch and a first power electronic switch which are connected in series, the second line comprises a second fast mechanical switch and a diode which are connected in series, the anode of the diode is connected with the third line, the third line comprises a plurality of second power electronic switches which are connected in series, and the fourth line comprises a non-linear resistor or an arrester;
the tripping method of the circuit breaker comprises the following steps:
a1, determining a fault line;
a2, opening a first fast mechanical switch corresponding to a fault line and a second fast mechanical switch corresponding to a non-fault line, and simultaneously turning off the first power electronic switch and turning on the second power electronic switch;
a3, turning off the second power electronic switch after the distance between the moving contact and the static contact of the first quick mechanical switch corresponding to the fault line and the second quick mechanical switch corresponding to the non-fault line reaches a preset value;
a4, after the fault current is absorbed by the fourth line, opening a second quick mechanical switch corresponding to the fault line and closing the second quick mechanical switch corresponding to the non-fault line;
the reclosing method is characterized in that after the breaker trips, whether a fault line suffers from transient faults or not is judged, if yes, reclosing operation is carried out, and if not, reclosing operation is not carried out.
2. The reclosing method according to claim 1, wherein whether the fault line encounters a transient fault is determined, specifically comprising the steps of:
b1: after the fault line is dissociated, closing the second quick mechanical switch corresponding to the fault line;
b2: detecting a fault line voltage;
b3: judging whether the fault line encounters transient faults or not according to the voltage of the fault line: if the voltage of the fault line rises to the direct current voltage of the system rapidly, the fault line suffers from transient faults, and if the voltage of the fault line is maintained to be close to 0, the fault line suffers from non-transient faults.
3. The reclosing method according to claim 2, wherein in the step B1, the method for freeing the fault line is as follows: the second fast mechanical switch corresponding to the faulty line is maintained in an open state for a first period of time.
4. The reclosing method of claim 1, wherein the reclosing operation is: and closing the first quick mechanical switch corresponding to the fault line.
5. The reclosing method of claim 1, wherein a warning message is issued if the faulted line experiences a non-transient fault.
6. A reclosing device is used for reclosing operation after tripping of a circuit breaker, the circuit breaker is installed in a direct current transmission system of which the receiving end is of an LCC-VSC series-parallel connection type, wherein,
the receiving end of the direct current transmission system with the receiving end of the LCC-VSC hybrid type comprises an LCC converter station and a plurality of VSC converter stations electrically connected with the LCC converter station;
the circuit breaker includes: the direct current transmission system comprises a plurality of connection points, a first line and a second line which are in one-to-one correspondence with the connection points, a third line and a fourth line, wherein one of the connection points is used for being electrically connected with the LCC converter station, the other connection points are used for being electrically connected with the VSC converter station, each connection point is respectively connected to two ends of the third line through the first line and the second line, the fourth line is connected to two ends of the third line in parallel, the first line is used for conducting load current when the direct current transmission system normally operates, the second line is used for isolating current and voltage among the connection points, the third line is used for breaking fault current when the direct current transmission system fails, and the fourth line is used for breaking overvoltage when the direct current transmission system fails and absorbing energy stored by an inductive element, the first line comprises a first fast mechanical switch and a first power electronic switch which are connected in series, the second line comprises a second fast mechanical switch and a diode which are connected in series, the cathode of the diode is connected with the third line, the third line comprises a plurality of second power electronic switches which are connected in series, and the fourth line comprises a non-linear resistor or an arrester;
the tripping method of the circuit breaker comprises the following steps:
a1, determining a fault line;
a2, opening a first fast mechanical switch corresponding to a fault line and a second fast mechanical switch corresponding to a non-fault line, and simultaneously turning off the first power electronic switch and turning on the second power electronic switch;
a3, turning off the second power electronic switch after the distance between the moving contact and the static contact of the first quick mechanical switch corresponding to the fault line and the second quick mechanical switch corresponding to the non-fault line reaches a preset value;
a4, after the fault current is absorbed by the fourth line, opening a second quick mechanical switch corresponding to the fault line and closing the second quick mechanical switch corresponding to the non-fault line;
the reclosing device is characterized by comprising:
the fault judging unit is used for judging whether a fault line suffers from transient faults or not after the breaker trips;
and the reclosing operation unit is used for carrying out reclosing operation when the fault line encounters transient fault and not carrying out reclosing operation when the fault line encounters non-transient fault.
7. The reclosing device of claim 6, wherein the fault determination unit comprises:
the first driving module is used for closing the second quick mechanical switch corresponding to the fault line after the fault line is dissociated;
the detection module is used for detecting the voltage of the fault line;
the judging module is used for judging whether the fault line suffers from transient faults or not according to the voltage of the fault line: if the voltage of the fault line rises to the direct current voltage of the system rapidly, the fault line suffers from transient faults, and if the voltage of the fault line is maintained to be close to 0, the fault line suffers from non-transient faults.
8. The reclosure device of claim 7, wherein in the first drive module, the fault line is dissociated by: the second fast mechanical switch corresponding to the faulty line is maintained in an open state for a first period of time.
9. The reclosing device of claim 6, wherein the reclosing operation unit, reclosing operation is: and closing the first quick mechanical switch corresponding to the fault line.
10. The reclosure device of claim 6 further comprising a warning unit for issuing a warning message if a fault line encounters a non-transient fault.
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| CN111884171B (en) * | 2020-07-15 | 2021-05-28 | 华北电力大学 | Single-phase fault line reclosing method and system of alternating current-direct current system |
| CN113625122A (en) * | 2021-08-23 | 2021-11-09 | 全球能源互联网研究院有限公司 | Fault property identification method for pseudo-bipolar flexible direct current system |
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| CN107359588B (en) * | 2016-09-22 | 2019-05-31 | 天津大学 | The very bipolar adaptive reclosing method of MMC-HVDC transmission system monopolar grounding fault |
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| CN107919648A (en) * | 2017-12-20 | 2018-04-17 | 国家电网公司 | A kind of anti-self-adapting automatic recloser and method for overlapping impact |
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