CN113241745A - Method for protecting grounding distance II section of electric power system line - Google Patents

Method for protecting grounding distance II section of electric power system line Download PDF

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CN113241745A
CN113241745A CN202110701515.4A CN202110701515A CN113241745A CN 113241745 A CN113241745 A CN 113241745A CN 202110701515 A CN202110701515 A CN 202110701515A CN 113241745 A CN113241745 A CN 113241745A
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section
distance
grounding
timer
grounding distance
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CN113241745B (en
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张安龙
黄福全
刘子俊
马帅
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Shenzhen Power Supply Bureau Co Ltd
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Shenzhen Power Supply Bureau Co Ltd
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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

Abstract

The invention discloses a method for protecting a line grounding distance II section of an electric power system, which comprises the following steps: when a fault occurs, t0Starting the protection of the moment grounding distance II section, setting the first timer, the second timer and the third timer to be 0, setting the first zone bit and the second zone bit to be 0, and starting timing by the first timer; judging whether the criterion of the grounding distance II section is met, if so, entering a self-holding state of the grounding distance II section, setting the first flag position to be 1, and starting timing by the second timer; the first zone bit is a self-holding zone bit of a grounding distance II section, and the second zone bit is a zero sequence criterion starting zone bit; after entering the self-holding state of the grounding distance II section, if the criterion of the grounding distance II section is still met, the timing result t of the second timer is obtained2To reach t2maxAnd during time limit, the grounding distance II section protection acts to send a tripping instruction to a circuit breaker of the circuit, so that the reliability of the grounding distance II section protection is improved.

Description

Method for protecting grounding distance II section of electric power system line
Technical Field
The invention relates to the technical field of relay protection of a power system, in particular to a method for protecting a grounding distance II section of a power system circuit.
Background
The relay protection is used as a first defense line for guaranteeing the safe operation of the power system, and has important significance for maintaining the reliability of actions under various fault working conditions; under the condition that wind power is connected to the low-voltage side of a transformer in a system, when the existing transformer is in gap grounding, the technical problem that the protection function of the line grounding distance section II cannot be reliably realized when the gap of a neutral point of the transformer is broken down exists.
Disclosure of Invention
The invention aims to provide a method for protecting a line grounding distance II section of an electric power system, which aims to solve the technical problem that the line grounding distance II section protection function cannot be reliably realized when the gap of a neutral point of a transformer containing wind power access breaks down at present.
In order to achieve the above object, an embodiment of the present invention provides a method for protecting a line grounding distance of a power system in a second section, where the power system includes a transformer, a wind power is connected to a low-voltage side of the transformer, a neutral point of the transformer is grounded via a gap, and a line relay protection device on an outgoing line on a high-voltage side of the transformer is configured with a grounding distance in the second section, where the method includes the following steps:
when a fault occurs, t0Starting the protection of the moment grounding distance II section, setting the first timer, the second timer and the third timer to be 0, setting the first zone bit and the second zone bit to be 0, and starting timing by the first timer; judging whether the criterion of the grounding distance II section is met, if so, entering a self-holding state of the grounding distance II section, setting the first flag position to be 1, and starting timing by the second timer; the first zone bit is a self-holding zone bit of a grounding distance II section, and the second zone bit is a zero sequence criterion starting zone bit;
after entering the self-holding state of the grounding distance II section, if the criterion of the grounding distance II section is still met, the timing result t of the second timer is obtained2To reach t2maxDuring time limit, the grounding distance II section protects action and sends a tripping instruction to a circuit breaker of the circuit;
after entering the self-holding state of the grounding distance II section, if the criterion of the grounding distance II section is not longerIf yes, the third timer starts to time, and when the time counting result t of the third timer is reached3To reach t3maxAfter time limit, judging whether the zero sequence current and voltage criterion is satisfied, if so, judging the result t of the second timer2To reach t2maxAnd during time limit, the grounding distance II section protects and acts, and a tripping instruction is sent to a circuit breaker of the circuit.
Optionally, the method further comprises:
when a fault occurs, if the timing result t of the first timer is t1To reach t1maxAnd (4) time limit, if the criterion of the grounding distance II section is not met, exiting the grounding distance II section protection.
Optionally, the method further comprises:
and after entering a self-holding state of the grounding distance II section, if the zero-sequence current and voltage criteria are not met, exiting the protection of the grounding distance II section.
Optionally, the grounding distance ii section protection criterion is:
Figure BDA0003129912250000021
wherein Z ismMeasuring impedance for ground distance protection, ZsetSetting impedance for the distance II section.
Optionally, the t1maxThe time limit is less than the action time limit t of the grounding distance II2max。
Optionally, the t2maxAnd setting the time limit according to the action time limit of the grounding distance II.
Optionally, the t3maxAnd setting the time limit according to a data window for avoiding gap breakdown and detecting the zero sequence current.
Optionally, the zero-sequence current and voltage criterion is as follows:
I0.m>I0.set
U0.m>U0.set
wherein, I0.mAs zero sequence current measurement value, U0.mIs zero sequence voltageMeasured value, I0.setIs a zero sequence current setting value, U0.setAnd setting a zero sequence voltage value.
The embodiment of the invention has the following beneficial effects:
the method has the advantages that the measured impedance and the zero sequence current are calculated by utilizing the measurement information and the setting value of the installation position of the line protection device after the fault, when the fault cannot be reliably identified by the grounding distance protection criterion due to the breakdown of the neutral point gap of the transformer with the wind power access, the zero sequence current criterion is used for assisting the judgment, the problem that the function of protecting the line grounding distance in the second section cannot be reliably realized when the neutral point gap of the transformer with the wind power access breaks down is solved, and the relay protection reliability is improved.
Additional features and advantages of the invention will be set forth in the description which follows.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flowchart of a method for protecting a section ii of a line grounding distance of an electrical power system according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of an electrical power system to which a method for protecting a line grounding distance ii of the electrical power system is applied according to an embodiment of the present invention.
Detailed Description
Various exemplary embodiments, features and aspects of the present disclosure will be described in detail below with reference to the accompanying drawings. In addition, in the following detailed description, numerous specific details are set forth in order to provide a better understanding of the present invention. It will be understood by those skilled in the art that the present invention may be practiced without some of these specific details. In some instances, well known means have not been described in detail so as not to obscure the present invention.
Referring to fig. 1-2, an embodiment of the present invention provides a method for protecting a line grounding distance section ii of a power system, in view of the problem that the protection action of the grounding distance section ii is unreliable when a main transformer gap of the wind power access system breaks down, as shown in fig. 2, the power system includes a transformer, a wind power access is provided on a low-voltage side of the transformer, a neutral point of the transformer is grounded through a gap, and a line relay protection device on a high-voltage side outgoing line of the transformer is configured with a grounding distance section ii protection;
as shown in fig. 1, the method of the present embodiment includes the following steps:
when a fault occurs, t0Starting the protection of the moment grounding distance II section, setting the first timer, the second timer and the third timer to be 0, setting the first zone bit 1 and the second zone bit 2 to be 0, and starting the timing of the first timer; judging whether the criterion of the grounding distance II section is met, if so, entering a self-holding state of the grounding distance II section, setting the position of the first mark 1 as 1, and starting timing by the second timer; if the timing result t of the first timer is1To reach t1maxTime limit, if the criterion of the grounding distance II section is not met, the grounding distance II section protection is quitted; the first zone bit 1 is a self-holding zone bit of a grounding distance II section, and the second zone bit 2 is a zero-sequence criterion starting zone bit;
after entering the self-holding state of the grounding distance II section, if the criterion of the grounding distance II section is still met, the timing result t of the second timer is obtained2To reach t2maxDuring time limit, the grounding distance II section protects action and sends a tripping instruction to a circuit breaker of the circuit;
after entering a self-holding state of the grounding distance II section, if the criterion of the grounding distance II section is not met any more, the third timer starts to time, and when the time-keeping result t of the third timer is up3To reach t3maxAfter time limit, judging whether the zero sequence current and voltage criterion is satisfied, if so, judging the result t of the second timer2To reach t2maxDuring time limit, the grounding distance II section protects action and sends a tripping instruction to a circuit breaker of the circuit; if not, the grounding distance II section protection is quitted.
Optionally, the grounding distance ii section protection criterion is:
Figure BDA0003129912250000051
wherein Z ismMeasuring impedance for ground distance protection, ZsetSetting impedance for the distance II section.
Optionally, the t1maxThe time limit is less than the action time limit t of the grounding distance II2max(ii) a In the present embodiment, t is preferred but not limited1max＝200ms。
Optionally, the t2maxSetting the time limit according to the action time limit of the grounding distance II; in the present embodiment, t is preferred but not limited2max＝300ms。
Optionally, the t3maxSetting time limit according to a data window for avoiding gap breakdown and detecting zero sequence current; in the present embodiment, t is preferred but not limited3max＝30ms。
Optionally, after the wind power access system enters a self-holding state of the grounding distance II section, due to the influence of the transient state and the steady state process of the clearance breakdown of the main transformer of the wind power access system on the impedance of the grounding distance measurement, the criterion of the grounding distance II section cannot be continuously met, and at the moment, the criterion is passed through a timer t3Time delay t of3maxAvoiding a data window for gap breakdown and zero-sequence current detection, and detecting zero-sequence current and voltage as protection criteria; the zero-sequence current and voltage criterion is as follows:
I0.m>I0.set
U0.m>U0.set
wherein, I0.mAs zero sequence current measurement value, U0.mAs zero sequence voltage measurement value, I0.setIs a zero sequence current setting value, U0.setAnd setting a zero sequence voltage value.
According to the method, the measured impedance and the zero sequence current are calculated by using the measurement information and the setting value of the installation position of the line protection device after the fault, when the fault cannot be reliably identified by the grounding distance protection criterion due to the breakdown of the neutral point gap of the transformer with the wind power access, the zero sequence current criterion is used for assisting the judgment, the problem that the line grounding distance II section protection function cannot be reliably realized when the neutral point gap of the transformer with the wind power access is broken down is solved, and the relay protection reliability is improved.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen in order to best explain the principles of the embodiments, the practical application, or improvements made to the technology in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

Claims (8)

1. A line grounding distance II-stage protection method for an electric power system, wherein the electric power system comprises a transformer, a wind and electricity access is provided on the low-voltage side of the transformer, the neutral point of the transformer is grounded through a gap, and a line relay protection device on the high-voltage side outgoing line of the transformer is provided with grounding distance II-stage protection, and is characterized by comprising the following steps:
when a fault occurs, t0Starting the protection of the moment grounding distance II section, setting the first timer, the second timer and the third timer to be 0, setting the first zone bit and the second zone bit to be 0, and starting timing by the first timer; judging whether the criterion of the grounding distance II section is met, if so, entering a self-holding state of the grounding distance II section, setting the first flag position to be 1, and starting timing by the second timer; the first zone bit is a self-holding zone bit of a grounding distance II section, and the second zone bit is a zero sequence criterion starting zone bit;
after entering the self-holding state of the grounding distance II section, if the criterion of the grounding distance II section is still met, the timing result t of the second timer is obtained2To reach t2maxDuring time limit, the grounding distance II section protects action and sends a tripping instruction to a circuit breaker of the circuit;
after entering a self-holding state of the grounding distance II section, if the criterion of the grounding distance II section is not met any more, the third timer starts to time, and when the time-keeping result t of the third timer is up3To reach t3maxAfter time limit, judging whether the zero sequence current and voltage criterion is satisfied, if so, judging the result t of the second timer2To reach t2maxAnd during time limit, the grounding distance II section protects and acts, and a tripping instruction is sent to a circuit breaker of the circuit.
2. The method of claim 1, wherein the method further comprises:
when a fault occurs, if the timing result t of the first timer is t1To reach t1maxAnd (4) time limit, if the criterion of the grounding distance II section is not met, exiting the grounding distance II section protection.
3. The method of claim 1, wherein the method further comprises:
and after entering a self-holding state of the grounding distance II section, if the zero-sequence current and voltage criteria are not met, exiting the protection of the grounding distance II section.
4. The method for protecting the II sections of the grounding distances of the lines of the electric power system according to claim 1, wherein the criterion for protecting the II sections of the grounding distances is as follows:
Figure FDA0003129912240000021
wherein Z ismMeasuring impedance for ground distance protection, ZsetSetting impedance for the distance II section.
5. The method as claimed in claim 1, wherein t is the distance between ground and the ground1maxTime limit less than grounding distanceTime limit t2max。
6. The method as claimed in claim 1, wherein t is the distance between ground and the ground2maxAnd setting the time limit according to the action time limit of the grounding distance II.
7. The method as claimed in claim 1, wherein t is the distance between ground and the ground3maxAnd setting the time limit according to a data window for avoiding gap breakdown and detecting the zero sequence current.
8. The method for protecting the II-section grounding distance of the power system circuit according to claim 1, wherein the zero-sequence current and voltage criteria are as follows:
I0.m>I0.set
U0.m>U0.set
wherein, I0.mAs zero sequence current measurement value, U0.mAs zero sequence voltage measurement value, I0.setIs a zero sequence current setting value, U0.setAnd setting a zero sequence voltage value.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105207185A (en) * 2015-10-15 2015-12-30 华北电力大学（保定） Wide-area backup protecting method capable of preventing cascading trip of line
CN105655992A (en) * 2016-01-26 2016-06-08 华北电力大学 T line protection scheme fit for distributed electrical connection
CN109888750A (en) * 2019-03-25 2019-06-14 国电南瑞科技股份有限公司 A kind of shortening site failure protection time delay of action method and system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105207185A (en) * 2015-10-15 2015-12-30 华北电力大学（保定） Wide-area backup protecting method capable of preventing cascading trip of line
CN105655992A (en) * 2016-01-26 2016-06-08 华北电力大学 T line protection scheme fit for distributed electrical connection
CN109888750A (en) * 2019-03-25 2019-06-14 国电南瑞科技股份有限公司 A kind of shortening site failure protection time delay of action method and system

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