CN110797848A - Line longitudinal differential protection method suitable for three-terminal conventional direct-current power transmission system - Google Patents
Line longitudinal differential protection method suitable for three-terminal conventional direct-current power transmission system Download PDFInfo
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- CN110797848A CN110797848A CN201911166947.9A CN201911166947A CN110797848A CN 110797848 A CN110797848 A CN 110797848A CN 201911166947 A CN201911166947 A CN 201911166947A CN 110797848 A CN110797848 A CN 110797848A
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- longitudinal differential
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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
Abstract
The invention discloses a line longitudinal differential protection method suitable for a three-terminal conventional direct-current power transmission system, which relates to the technical field of emergency protection circuit devices and comprises the following steps: step 1: reading the running state of the converter station B, and judging whether the converter station B is in a rectification mode or an inversion mode; step 2: judging the input condition of each pole of each station in the three-terminal conventional direct-current power transmission system; and step 3: judging longitudinal differential protection of the same direct-current line of each pole of each station in the three-terminal conventional direct-current power transmission system, and outputting protection actions by a protection device of the three-terminal conventional direct-current power transmission system when the longitudinal differential protection input current of the two ends of the same direct-current line meets the following criteria and meets set delay conditions.
Description
Technical Field
The invention relates to the technical field of emergency protection circuit devices, in particular to a line longitudinal differential protection method suitable for a three-terminal conventional direct-current power transmission system.
Background
Longitudinal differential protection, i.e. longitudinal differential protection of a power transmission line, is to use some kind of communication channel to longitudinally connect protection devices at two ends of the power transmission line, to transmit the electrical quantities at each end, such as the direction of current and power, to the opposite end, and to compare the electrical quantities at the two ends to judge whether the fault is in the range of the line or out of the range of the line, thereby determining whether to cut off the protected line. The conventional direct-current transmission projects in operation at present are direct currents at two ends, and bipolar connection is adopted, as shown in fig. 1. In a conventional direct-current power transmission system with two ends, the direct-current line longitudinal differential protection of the pole compares the current at the two ends of the direct-current line of the pole,
with the development of dc technology, three-terminal conventional dc transmission systems are receiving attention. A typical topology of a three-terminal conventional dc transmission system is shown in fig. 2. In fig. 2, the three-terminal dc transmission system includes 3 stations, i.e., converter station a, converter station B, and converter station C. The converter station A, the converter station B and the converter station C can operate at three ends or two ends as required. When the converter station B is put into and operates in the rectification mode, the first pole valve group of the converter station B is connected with the first pole line, the second pole valve group of the converter station B is connected with the second pole line, and when the converter station B is put into and operates in the inversion mode, the first pole valve group of the converter station B is connected with the second pole line, and the second pole valve group of the converter station B is connected with the first pole line.
In a three-terminal dc system, if the longitudinal differential protection of the dc line still adopts the strategy of comparing the currents at the two ends of the local dc line in the two-terminal dc system, the longitudinal differential protection of the dc line may not work in some operation modes, for example
1) When the converter station B operates in an inversion mode, the second pole protection of the converter station B compares the currents at two ends of the second pole line, but the actual second pole is connected with the first pole line, and the second pole of the converter station B loses the protection of the first pole line.
2) The direct-current line longitudinal differential protection of the converter station A is compared with the current at two ends of the line 1 between the converter station A and the converter station B, and when the converter station B exits and the two ends of the converter station A and the converter station C operate, the converter station A loses the protection of the line 2 between the converter station B and the converter station C.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a line longitudinal differential protection method suitable for a three-terminal conventional direct-current transmission system, and the direct-current line longitudinal differential protection can effectively play a role in various operation modes of the three-terminal direct-current transmission system by judging the input operation states of all converter stations.
In order to achieve the purpose, the technical scheme of the invention is as follows:
a line longitudinal differential protection method suitable for a three-terminal conventional direct-current transmission system is carried out based on the three-terminal conventional direct-current transmission system, the three-terminal conventional direct-current transmission system comprises a converter station A, a converter station B and a converter station C, a first pole and a second pole of the converter station A are respectively connected with a first pole and a second pole of the converter station C, the first pole of the converter station B is connected with the converter station A and the first pole or the second pole of the converter station C, and the second pole of the converter station B is connected with the other pole of the converter station A and the other pole of the converter station C; which comprises the following steps:
step 1: reading the running state of the converter station B, and judging whether the converter station B is in a rectification mode or an inversion mode;
step 2: judging the input condition of each pole of each station in the three-terminal conventional direct-current power transmission system;
and step 3: judging the longitudinal differential protection condition of the same direct current line of each pole of each station in the three-terminal conventional direct current transmission system, outputting protection action by the protection device of the three-terminal conventional direct current transmission system when the longitudinal differential protection input current of the two ends of the same direct current line meets the following criterion and meets the set delay condition,
|Idl-Idl_os|>max(I_set,k_set*Idl)
in the formula, Idl is a line longitudinal differential protection input current of a local pole, and Idl _ os is a line longitudinal differential protection input current of a local pole; i _ set and k _ set are set parameters of the protection criterion; wherein:
a. when the converter station B is in a rectification mode, and the first poles of the converter station A, the converter station B and the converter station C are all switched in, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the line 1 of the first pole of the converter station B are respectively Idl _ A1 and Idl _ B1a, and the line longitudinal differential protection input quantity of the first pole of the converter station C and the line longitudinal differential protection input current of the line 2 of the first pole of the converter station B are respectively Idl _ C1 and Idl _ B1C;
b. when the converter station B is in the rectifying mode, and the first poles of the converter stations a and C are both put in and the first pole of the converter station B is withdrawn, the line longitudinal differential protection input current of the first pole of the converter station a and the line longitudinal differential protection input current of the first pole of the converter station C are both Idl _ a1 and Idl _ C1.
c. When the converter station B is in an inversion mode, the first pole of the converter station A is put into operation, the second pole of the converter station B is put into operation, and the first pole of the converter station C is put into operation, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the line 1 of the second pole of the converter station B are Idl _ A1 and Idl _ B1a, and the line longitudinal differential protection input current of the first pole of the converter station C and the line longitudinal differential protection input current of the line 2 of the second pole of the converter station B are Idl _ C1 and Idl _ B1C.
d. When the converter station B is in an inversion mode, the first pole of the converter station A is put in, the second pole of the converter station B is withdrawn, and the first pole of the converter station C is put in, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the first pole of the converter station C are Idl _ A1 and Idl _ C1.
The line longitudinal differential protection method suitable for the three-terminal conventional direct-current transmission system further comprises, in step 2: the three-terminal conventional direct-current transmission system controls the first poles of the converter station A, the converter station B and the converter station C to be switched in or switched out through switches QB1a, QB1B and QB1C respectively, and controls the second poles of the converter station A, the converter station B and the converter station C to be switched in or switched out through switches QB2a, QB2B and QB2C respectively;
a. judging whether the switch QB1a is separated or not, if so, exiting the first pole of the converter station A; if not, the first pole of the converter station A is put into; judging whether the switch QB2a is separated, if so, withdrawing the second pole of the converter station A, and if not, putting the second pole of the converter station A into operation;
b. if the converter station B is in a rectification mode, judging whether the switch QB1B is separated, if so, exiting the first pole of the converter station B; if not, the first pole of the converter station B is put into; judging whether the switch QB2B is separated, if so, withdrawing the second pole of the converter station B, and if not, putting the second pole of the converter station B into operation; if the converter station B is in an inversion mode, judging whether the switch QB1B is separated, if so, withdrawing the second pole of the converter station B, and if not, putting the second pole of the converter station B into operation; judging whether the switch QB2B is separated, if so, withdrawing the first pole of the converter station B, otherwise, putting the first pole of the converter station B into operation;
c. judging whether the switch QB1C is separated, if so, withdrawing the first pole of the converter station C, and if not, putting the first pole of the converter station C into operation; and judging whether the switch QB2C is separated, if so, exiting the second pole of the converter station C, and if not, putting the second pole of the converter station C into operation.
Compared with the prior art, the invention has the beneficial effects that: the invention can consider the input condition of each pole of each station of the three-terminal direct-current system, judge the protection range of the longitudinal differential protection of each direct-current line of each station according to the input condition of the converter station, and can effectively play a role in various operation modes of the three-terminal direct-current system, thereby ensuring the reliability of the direct-current system.
Drawings
FIG. 1 is a topology diagram of a two-terminal conventional DC power transmission system of the present invention;
fig. 2 is a topology diagram of a three-terminal conventional dc transmission system of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and detailed description.
Example (b):
a line longitudinal differential protection method suitable for a three-terminal conventional direct-current transmission system is carried out based on the three-terminal conventional direct-current transmission system, the three-terminal conventional direct-current transmission system comprises a converter station A, a converter station B and a converter station C, a first pole and a second pole of the converter station A are respectively connected with a first pole and a second pole of the converter station C, the first pole of the converter station B is connected with the converter station A and the first pole or the second pole of the converter station C, and the second pole of the converter station B is connected with the other pole of the converter station A and the other pole of the converter station C; which comprises the following steps:
step 1: reading the running state of the converter station B, and judging whether the converter station B is in a rectification mode or an inversion mode
Step 2: and judging the input condition of each pole of each station in the three-terminal conventional direct-current power transmission system.
In step 2: the three-terminal conventional direct-current transmission system controls the first poles of the converter station A, the converter station B and the converter station C to be switched in or switched out through switches QB1a, QB1B and QB1C respectively, and controls the second poles of the converter station A, the converter station B and the converter station C to be switched in or switched out through switches QB2a, QB2B and QB2C respectively;
a. judging whether the switch QB1a is separated or not, if so, exiting the first pole of the converter station A; if not, the first pole of the converter station A is put into; judging whether the switch QB2a is separated, if so, withdrawing the second pole of the converter station A, and if not, putting the second pole of the converter station A into operation;
b. if the converter station B is in a rectification mode, judging whether the switch QB1B is separated, if so, exiting the first pole of the converter station B; if not, the first pole of the converter station B is put into; judging whether the switch QB2B is separated, if so, withdrawing the second pole of the converter station B, and if not, putting the second pole of the converter station B into operation; if the converter station B is in an inversion mode, judging whether the switch QB1B is separated, if so, withdrawing the second pole of the converter station B, and if not, putting the second pole of the converter station B into operation; judging whether the switch QB2B is separated, if so, withdrawing the first pole of the converter station B, otherwise, putting the first pole of the converter station B into operation;
c. judging whether the switch QB1C is separated, if so, withdrawing the first pole of the converter station C, and if not, putting the first pole of the converter station C into operation; and judging whether the switch QB2C is separated, if so, exiting the second pole of the converter station C, and if not, putting the second pole of the converter station C into operation.
And step 3: judging the longitudinal differential protection of the same DC line of each pole of each station in the three-terminal conventional DC power transmission system, outputting protection action by the protection device of the three-terminal conventional DC power transmission system when the longitudinal differential protection input current of the two ends of the same DC line meets the following criterion and meets the set delay condition,
|Idl-Idl_os|>max(I_set,k_set*Idl)
in the formula, Idl is a line longitudinal differential protection input current of a local pole, Idl _ os is a line longitudinal differential protection input current of a local pole, and the line longitudinal differential protection input current of the local pole is transmitted to the local pole from a local pole protection system through inter-station communication; i _ set and k _ set are set parameters of the protection criterion.
Wherein:
a. when the converter station B is in a rectification mode, and the first poles of the converter station A, the converter station B and the converter station C are all switched in, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the line 1 of the first pole of the converter station B are respectively Idl _ A1 and Idl _ B1a, and the line longitudinal differential protection input quantity of the first pole of the converter station C and the line longitudinal differential protection input current of the line 2 of the first pole of the converter station B are respectively Idl _ C1 and Idl _ B1C;
b. when the converter station B is in the rectifying mode, and the first poles of the converter stations a and C are both put in and the first pole of the converter station B is withdrawn, the line longitudinal differential protection input current of the first pole of the converter station a and the line longitudinal differential protection input current of the first pole of the converter station C are both Idl _ a1 and Idl _ C1.
c. When the converter station B is in an inversion mode, the first pole of the converter station A is put into operation, the second pole of the converter station B is put into operation, and the first pole of the converter station C is put into operation, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the line 1 of the second pole of the converter station B are Idl _ A1 and Idl _ B1a, and the line longitudinal differential protection input current of the first pole of the converter station C and the line longitudinal differential protection input current of the line 2 of the second pole of the converter station B are Idl _ C1 and Idl _ B1C.
d. When the converter station B is in an inversion mode, the first pole of the converter station A is put in, the second pole of the converter station B is withdrawn, and the first pole of the converter station C is put in, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the first pole of the converter station C are Idl _ A1 and Idl _ C1.
The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention accordingly, and not to limit the protection scope of the present invention accordingly. All equivalent changes or modifications made in accordance with the spirit of the present disclosure are intended to be covered by the scope of the present disclosure.
Claims (2)
1. A line longitudinal differential protection method suitable for a three-terminal conventional direct-current transmission system is carried out based on the three-terminal conventional direct-current transmission system, the three-terminal conventional direct-current transmission system comprises a converter station A, a converter station B and a converter station C, a first pole and a second pole of the converter station A are respectively connected with a first pole and a second pole of the converter station C, the first pole of the converter station B is connected with the converter station A and the first pole or the second pole of the converter station C, and the second pole of the converter station B is connected with the other pole of the converter station A and the other pole of the converter station C; the method is characterized by comprising the following steps:
step 1: reading the running state of the converter station B, and judging whether the converter station B is in a rectification mode or an inversion mode;
step 2: judging the input condition of each pole of each station in the three-terminal conventional direct-current power transmission system;
and step 3: judging the longitudinal differential protection condition of the same direct current line of each pole of each station in the three-terminal conventional direct current transmission system, outputting protection action by the protection device of the three-terminal conventional direct current transmission system when the longitudinal differential protection input current of the two ends of the same direct current line meets the following criterion and meets the set delay condition,
|Idl-Idl_os|>max(I_set,k_set*Idl)
in the formula, Idl is a line longitudinal differential protection input current of a local pole, and Idl _ os is a line longitudinal differential protection input current of a local pole; i _ set and k _ set are set parameters of the protection criterion; wherein:
a. when the converter station B is in a rectification mode, and the first poles of the converter station A, the converter station B and the converter station C are all switched in, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the line 1 of the first pole of the converter station B are respectively Idl _ A1 and Idl _ B1a, and the line longitudinal differential protection input quantity of the first pole of the converter station C and the line longitudinal differential protection input current of the line 2 of the first pole of the converter station B are respectively Idl _ C1 and Idl _ B1C;
b. when the converter station B is in a rectification mode, the first poles of the converter station A and the converter station C are both put in, and the first pole of the converter station B is withdrawn, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the first pole of the converter station C are both Idl _ A1 and Idl _ C1;
c. when the converter station B is in an inversion mode, the first pole of the converter station A is put into, the second pole of the converter station B is put into, and the first pole of the converter station C is put into, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the line 1 of the second pole of the converter station B are respectively Idl _ A1 and Idl _ B1a, and the line longitudinal differential protection input current of the first pole of the converter station C and the line longitudinal differential protection input current of the line 2 of the second pole of the converter station B are respectively Idl _ C1 and Idl _ B1C;
d. when the converter station B is in an inversion mode, the first pole of the converter station A is put in, the second pole of the converter station B is withdrawn, and the first pole of the converter station C is put in, the line longitudinal differential protection input current of the first pole of the converter station A and the line longitudinal differential protection input current of the first pole of the converter station C are Idl _ A1 and Idl _ C1.
2. The line longitudinal differential protection method suitable for the three-terminal conventional direct-current transmission system according to claim 1, wherein in step 2: the three-terminal conventional direct-current transmission system controls the first poles of the converter station A, the converter station B and the converter station C to be switched in or switched out through switches QB1a, QB1B and QB1C respectively, and controls the second poles of the converter station A, the converter station B and the converter station C to be switched in or switched out through switches QB2a, QB2B and QB2C respectively;
a. judging whether the switch QB1a is separated or not, if so, exiting the first pole of the converter station A; if not, the first pole of the converter station A is put into; judging whether the switch QB2a is separated, if so, withdrawing the second pole of the converter station A, and if not, putting the second pole of the converter station A into operation;
b. if the converter station B is in a rectification mode, judging whether the switch QB1B is separated, if so, exiting the first pole of the converter station B; if not, the first pole of the converter station B is put into; judging whether the switch QB2B is separated, if so, withdrawing the second pole of the converter station B, and if not, putting the second pole of the converter station B into operation; if the converter station B is in an inversion mode, judging whether the switch QB1B is separated, if so, withdrawing the second pole of the converter station B, and if not, putting the second pole of the converter station B into operation; judging whether the switch QB2B is separated, if so, withdrawing the first pole of the converter station B, otherwise, putting the first pole of the converter station B into operation;
c. judging whether the switch QB1C is separated, if so, withdrawing the first pole of the converter station C, and if not, putting the first pole of the converter station C into operation; and judging whether the switch QB2C is separated, if so, exiting the second pole of the converter station C, and if not, putting the second pole of the converter station C into operation.
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