CN111725778B - Line protection CT disconnection locking method, system and medium under condition of reversed trend - Google Patents
Line protection CT disconnection locking method, system and medium under condition of reversed trend Download PDFInfo
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- CN111725778B CN111725778B CN202010461472.2A CN202010461472A CN111725778B CN 111725778 B CN111725778 B CN 111725778B CN 202010461472 A CN202010461472 A CN 202010461472A CN 111725778 B CN111725778 B CN 111725778B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/04—Arrangements for preventing response to transient abnormal conditions, e.g. to lightning or to short duration over voltage or oscillations; Damping the influence of dc component by short circuits in ac networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0092—Details of emergency protective circuit arrangements concerning the data processing means, e.g. expert systems, neural networks
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Abstract
The invention discloses a circuit protection CT disconnection locking method, a system and a medium under the condition of flow reversal, wherein the method comprises the steps of carrying out fault judgment according to the flow reversal of A, B, C three-phase circuits to obtain a fault judgment result; and carrying out OR logic operation on the fault judgment result, the monitoring result of the first zero sequence current monitoring logic and the output fault state self-holding logic judgment result, widening the output fault state self-holding logic judgment result to obtain the output fault state self-holding logic judgment result, carrying out AND logic operation on the output fault state self-holding logic judgment result and the monitoring result of the second zero sequence current monitoring logic after negating the output fault state self-holding logic judgment result, and using the operation result as a control signal of CT disconnection after delaying. The invention contains self-holding logic of zero sequence current compensation, can realize that the whole fault period after the power flow is reversed has locking function, and avoids the circuit protection from being locked by the CT when the zero sequence current is between the CT line breaking action value and the zero sequence overcurrent protection action value under the high resistance grounding fault.
Description
Technical Field
The invention relates to the field of Transformer substation relay protection, in particular to a method, a system and a medium for locking a circuit protection CT (Current Transformer) in a power flow reverse condition in a disconnection manner.
Background
In recent years, several high-resistance grounding faults of 110kV lines occur in the Hunan power grid, so that corresponding 220kV main transformer override trip accidents are caused, and certain power load loss and negative effects are caused. When a high-resistance grounding fault occurs to a line, a system can generate zero-sequence current, but the amplitude is small and may be between a zero-sequence overcurrent protection action value and a CT (computed tomography) line breaking action value, so that the CT line breaking is locked to protect the line, and further, the main transformer zero-sequence overcurrent protection override trip is caused when the subsequent fault characteristics are aggravated.
The investigation result of the line protection equipment of various domestic relay protection manufacturers shows that most of the line protection CT disconnection criterion is mainly realized by detecting zero-sequence current. The zero sequence current is equal to the algebraic sum of the three-phase current. When the system normally operates, the zero sequence current of the system is very small and is mainly caused by three-phase load unbalance. When a CT one-phase disconnection occurs, a CT secondary phase loss will generate a zero-sequence current associated with the load current. Generally, the load current is smaller than the fault current, so that the normal state, the fault state and the CT disconnection can be identified by detecting the zero sequence current of the system through a long time window. However, under the condition of high-resistance grounding fault, the fault current is small, and the zero-sequence overcurrent protection action condition reflecting the fault state cannot be achieved, so that the CT broken line is mistakenly locked to protect the circuit.
The improvement of the line CT disconnection criterion is an effective measure for avoiding the occurrence of the events, namely, the CT disconnection criterion is more strict by adding the criterion, and the CT disconnection is prevented from being mistakenly reported under the high-resistance grounding fault.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: the invention provides a circuit protection CT (current transformer) line breaking locking method, a system and a medium under the condition of load flow reversal, aiming at the problems in the prior art, wherein the circuit protection CT line breaking locking method, the system and the medium comprise self-holding logic of zero sequence current compensation, can realize that the whole fault period after the load flow reversal has the locking effect, and avoid that the circuit protection is locked by the CT when the zero sequence current is between a CT line breaking action value and a zero sequence overcurrent protection action value under the condition of high-resistance grounding fault.
In order to solve the technical problems, the invention adopts the technical scheme that:
a circuit protection CT disconnection locking method under a tidal current reverse condition comprises the following implementation steps:
1) carrying out fault judgment according to the power flow reversal of the A, B, C three-phase line to obtain a fault judgment result;
2) the fault judgment result, the monitoring result of the first zero sequence current monitoring logic and the output fault state self-holding logic judgment result are subjected to OR logic operation and then are expanded to obtain the output fault state self-holding logic judgment result, and the criterion of the first zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT wire breakage return value Iset2；
3) The output fault state self-holding logic judgment result is inverted and then is subjected to AND logic operation with the monitoring result of the second zero sequence current monitoring logic, the AND logic operation result is delayed to be used as a control signal of CT disconnection, and the criterion of the second zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT disconnection action value Iset1。
Optionally, the detailed steps of step 1) include:
1.1) respectively carrying out power flow reversal judgment on A, B, C three-phase lines to obtain a single-phase power flow reversal judgment result;
1.2) obtaining a three-phase power flow reversal judgment result by carrying out OR logical operation on each single-phase power flow reversal judgment result;
and 1.3) carrying out AND logic operation on the three-phase power flow reverse judgment result and the monitoring result of the second zero sequence current monitoring logic to obtain a fault judgment result.
Optionally, when the power flow reversal judgment is performed on A, B, C three-phase lines in step 1.1), the judgment condition of each phase is that the angles of the phase voltage and the current are in the positive direction and the negative direction at the same time within the first specified time.
Alternatively, the positive direction refers to the angle of the voltage and the current being between (-90 °,90 °), and the negative direction refers to the angle of the voltage and the current being between (90 °,270 °).
Optionally, the first specified time is 100 ms.
Optionally, the stretching time in step 2) is 1 s.
Optionally, the time delay in step 3) is 12 s.
In addition, the invention also provides a circuit protection CT disconnection locking system under the condition of reversed power flow, which comprises:
the power flow reverse judging unit comprises a first OR gate with three inputs, the three inputs of the first OR gate correspond to a power flow reverse judging module of A, B, C three-phase lines respectively, the power flow reverse judging module comprises a first AND gate with two inputs, one input of the first AND gate is a result obtained by broadening a broadening element by a judging logic of which the angle of the voltage and the current of the corresponding phase is between (-90 degrees and 90 degrees, and the other input of the first AND gate is a result obtained by broadening a broadening element by a judging logic of which the angle of the voltage and the current of the corresponding phase is between (90 degrees and 270 degrees);
the second zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT line break action value Iset1；
The fault state self-holding unit comprises a second AND gate, a second OR gate, a first zero sequence current monitoring logic and a widening element, wherein the criterion of the first zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT disconnection return value Iset2The input end of the second and-gate is respectively connected with the input end of the power flow reversal judging unit and the output end of the second zero sequence current monitoring logic, the input end of the second or-gate is respectively connected with the output end of the second and-gate, the output end of the first zero sequence current monitoring logic and the output end of the widening element, the output end of the second or-gate is connected with the input end of the widening element, and the output end of the widening element is used as the output end of the fault state self-holding unit;
the inverting input end of the inverting operation unit is connected with the output end of the fault state self-holding unit, and the conventional input end of the inverting operation unit is connected with the output end of the second zero sequence current monitoring logic;
and the input end of the time delay element is connected with the arithmetic unit, and the output end of the time delay element is used as a control signal output terminal for CT disconnection.
Furthermore, the present invention also provides a line protection CT line break blocking system under a load flow reversal condition, which includes a computer device programmed or configured to execute the steps of the line protection CT line break blocking method under the load flow reversal condition, or a computer program programmed or configured to execute the line protection CT line break blocking method under the load flow reversal condition is stored on a memory of the computer device.
Furthermore, the present invention also provides a computer readable storage medium having stored thereon a computer program programmed or configured to execute the method of line protection CT outage lockout under a load flow reversal condition.
Compared with the prior art, the invention has the following advantages:
1. the invention can realize the locking of the CT disconnection function by combining the zero sequence current monitoring result when the line tide is reversed. Because the power flow reversal is a transient phenomenon, the self-holding logic of zero sequence current compensation is included in the invention, the locking effect can be realized in the whole fault period after the power flow reversal, and the circuit protection is locked by the CT when the zero sequence current is between the CT disconnection action value and the zero sequence overcurrent protection action value under the high-resistance grounding fault is avoided.
2. The electric quantity adopted by the method is the basic electric quantity, the judgment electric quantity does not need to be added, and the method is easy to realize.
Drawings
FIG. 1 is a schematic diagram of a basic flow of a method according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of a logic implementation principle of the method according to the embodiment of the present invention.
Detailed Description
As shown in fig. 1, the implementation steps of the method for locking the circuit protection CT under the reverse power flow condition in this embodiment include:
1) carrying out fault judgment according to the power flow reversal of the A, B, C three-phase line to obtain a fault judgment result;
2) the fault judgment result, the monitoring result of the first zero sequence current monitoring logic and the output fault state self-holding logic judgment result are subjected to OR logic operation and then are expanded to obtain the output fault state self-holding logic judgment result, and the criterion of the first zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT wire breakage return value Iset2；
3) The output fault state self-holding logic judgment result is inverted and then is subjected to AND logic operation with the monitoring result of the second zero sequence current monitoring logic, the AND logic operation result is delayed to be used as a control signal of CT disconnection, and the criterion of the second zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT disconnection action value Iset1(generally, the value is 0.9 times of the zero sequence IV protection action value of the line).
In this embodiment, the detailed steps of step 1) include:
1.1) respectively carrying out power flow reversal judgment on A, B, C three-phase lines to obtain a single-phase power flow reversal judgment result;
1.2) obtaining a three-phase power flow reversal judgment result by carrying out OR logical operation on each single-phase power flow reversal judgment result; the relation that the reverse judgment results of all single-phase power flows are equal, and the locking effect can be generated on the CT disconnection criterion as long as any one single-phase power flow reverse judgment result is that power flow transfer occurs;
and 1.3) carrying out AND logic operation on the three-phase power flow reverse judgment result and the monitoring result of the second zero sequence current monitoring logic to obtain a fault judgment result. When the circuit power flow is reversed and the zero sequence current of the circuit is larger than the conventional CT line breaking action value Iset1When the system fails, the fault judgment result can be output to be true.
In this embodiment, when the power flow reversal determination is performed on A, B, C three-phase lines in step 1.1), the determination condition of each phase is that the angles of the phase voltage and the current appear in the positive direction and the negative direction at the same time within the first specified time, and when the angles of a certain phase voltage and a certain current appear in the positive direction and the negative direction at the same time within the first specified time, it is determined that the power flow transfer occurs in the phase. In the present embodiment, the first specified time is 100 ms.
In the present embodiment, the positive direction means that the angle of the voltage and the current is between (-90 °,90 °), and the negative direction means that the angle of the voltage and the current is between (90 °,270 °). In addition, the two boundary positions of 90 °,270 ° (-90 °) can be divided into positive direction or negative direction according to the requirement, for example, the angles of voltage and current between (-90 °,90 ° ] are positive directions, the angles of voltage and current between (90 °,270 ° ] are negative directions, etc.
In this embodiment, the stretching time in step 2) is 1 s. And taking an OR from the fault judgment result and the monitoring result of the first zero sequence current monitoring logic, and returning an output result to an OR gate for input after the output result is widened for 1s, so that the self-maintenance of the fault state is realized.
In this embodiment, the time delay in step 3) is 12 s. The flow reversal is a transient phenomenon. The fault state self-holding logic can lock the CT disconnection function in the whole fault period after the power flow is reversed once, and the circuit protection is prevented from being locked by the CT disconnection when the fault current is between the CT disconnection action value and the zero-sequence overcurrent protection action value; in the embodiment, the output result of the self-holding logic is inverted, namely the CT disconnection function is locked continuously when a fault occurs; and performing AND operation on the self-holding logic output result and the zero-sequence current monitoring element, and judging that the CT is disconnected after the output result is delayed for 12 s.
Double faults, namely two or more faults occurring at the same time, are not considered when judging the abnormity and the faults of the power system. When the normal tide reversal occurs, the three phases are still balanced, and no obvious zero sequence current appears. Therefore, if the power flow of the line is reversed and the zero sequence current is accompanied, the system can be judged to have a fault. If CT disconnection occurs, the system is required to simultaneously meet the grounding or non-grounding fault, namely, two conditions are required to be simultaneously met, and the probability is too low to consider. Therefore, in the line protection CT disconnection locking method under the condition of the reversed flow, the reversed flow mutation criterion is introduced as the CT disconnection criterion locking condition aiming at the condition that the reversed flow can occur after the line fault, and the accuracy of the CT disconnection logic is improved.
As shown in fig. 2, the present embodiment further provides a line protection CT disconnection locking system under a reverse power flow condition, including:
the power flow reversal judging unit (as shown in a in fig. 2) comprises a first or gate with three inputs, the three inputs of the first or gate respectively correspond to A, B, C power flow reversal judging modules of three-phase lines, each power flow reversal judging module comprises a first and gate with two inputs, one input of the first and gate is a result obtained after the widening of a widening element by a judging logic of which the angle of the voltage and the current of the corresponding phase is between (-90 degrees and 90 degrees, and the other input of the first and gate is a result obtained after the widening of a widening element by a judging logic of which the angle of the voltage and the current of the corresponding phase is between (90 degrees and 270 degrees);
a second zero-sequence current monitoring logic (shown as b in FIG. 2) for determining that the zero-sequence current is larger than the conventional CT open-circuit action value Iset1；
The fault state self-holding unit (as shown in c in FIG. 2) comprises a second AND gate, a second OR gate, a first zero sequence current monitoring logic and a widening element, wherein the criterion of the first zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT disconnection return value Iset2The input end of the second and-gate is connected with the input end of the power flow reversal judging unit and the output end of the second zero sequence current monitoring logic respectively, the input end of the second or-gate is connected with the output end of the second and-gate, the output end of the first zero sequence current monitoring logic and the output end of the widening element respectively, the output end of the second or-gate is connected with the input end of the widening element, and the output end of the widening element is used as the output end of the fault state self-holding unit;
the operation unit (shown as d in fig. 2) comprises an inverting input end and a normal input end, wherein the inverting input end is connected with the output end of the fault state self-holding unit, and the normal input end is connected with the output end of the second zero sequence current monitoring logic;
and the input end of the time delay element (shown as e in fig. 2) is connected with the arithmetic unit, and the output end of the time delay element is used as a control signal output terminal for CT disconnection.
It should be noted that the power flow reversal determination unit, the second zero sequence current monitoring logic, the fault state self-holding unit, the and operation unit, and the delay element are all simple logic operations, and when the power flow reversal determination unit, the second zero sequence current monitoring logic, the fault state self-holding unit, the and operation unit, and the delay element are used for the circuit protection CT disconnection lockout control, the power flow reversal determination unit can be implemented in a program mode (at this time, the above components are program units), or can be implemented in a simple digital logic circuit (at this time, the above components are circuit units), and details are not repeated herein.
In addition, the present embodiment also provides a line protection CT disconnection locking system under a power flow reversal condition, which includes a computer device programmed or configured to execute the steps of the line protection CT disconnection locking method under the power flow reversal condition, or a computer program programmed or configured to execute the line protection CT disconnection locking method under the power flow reversal condition is stored in a memory of the computer device.
Furthermore, the present embodiment also provides a computer readable storage medium, which stores thereon a computer program programmed or configured to execute the line protection CT disconnection lockout method under the aforementioned power flow reversal condition.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The present application is directed to methods, apparatus (systems), and computer program products according to embodiments of the application wherein instructions, which execute via a flowchart and/or a processor of the computer program product, create means for implementing functions specified in the flowchart and/or block diagram block or blocks. These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks. These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.
Claims (9)
1. A circuit protection CT disconnection locking method under a tidal current reverse condition is characterized by comprising the following implementation steps:
1) carrying out fault judgment according to the power flow reversal of the A, B, C three-phase line to obtain a fault judgment result;
2) the fault judgment result, the monitoring result of the first zero sequence current monitoring logic and the output fault state self-holding logic judgment result are subjected to OR logic operation and then are expanded to obtain the output fault state self-holding logic judgment result, and the criterion of the first zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT wire breakage return value Iset2；
3) The output fault state self-holding logic judgment result is inverted and then is subjected to AND logic operation with the monitoring result of the second zero sequence current monitoring logic, the AND logic operation result is delayed to be used as a control signal of CT disconnection, and the criterion of the second zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT disconnection action value Iset1；
The detailed steps of the step 1) comprise:
1.1) respectively carrying out power flow reversal judgment on A, B, C three-phase lines to obtain a single-phase power flow reversal judgment result;
1.2) obtaining a three-phase power flow reversal judgment result by carrying out OR logical operation on each single-phase power flow reversal judgment result;
and 1.3) carrying out AND logic operation on the three-phase power flow reverse judgment result and the monitoring result of the second zero sequence current monitoring logic to obtain a fault judgment result.
2. The method for locking the circuit protection CT disconnection under the power flow reversal condition as claimed in claim 1, wherein, when the power flow reversal judgment is respectively carried out on A, B, C three-phase circuits in the step 1.1), the judgment condition of each phase is that the angles of the phase voltage and the current are in the positive direction and the negative direction at the same time within the first specified time.
3. The line protection CT line break lockout method of claim 2, wherein the forward direction is at an angle of voltage and current between (-90 °,90 °), and the reverse direction is at an angle of voltage and current between (90 °,270 °).
4. The line protection CT outage lockout method of claim 2, wherein the first specified time is 100 ms.
5. The line protection CT line break lockout method under reverse power flow conditions of claim 1, wherein the time of the broadening in step 2) is 1 s.
6. The method for locking the CT disconnection in the line protection under the reverse power flow condition as claimed in claim 1, wherein the time delay in the step 3) is 12 s.
7. A line protection CT disconnection locking system under a reverse trend condition is characterized by comprising:
the power flow reverse judging unit comprises a first OR gate with three inputs, the three inputs of the first OR gate correspond to a power flow reverse judging module of A, B, C three-phase lines respectively, the power flow reverse judging module comprises a first AND gate with two inputs, one input of the first AND gate is a result obtained by broadening a broadening element by a judging logic of which the angle of the voltage and the current of the corresponding phase is between (-90 degrees and 90 degrees, and the other input of the first AND gate is a result obtained by broadening a broadening element by a judging logic of which the angle of the voltage and the current of the corresponding phase is between (90 degrees and 270 degrees);
the second zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT line break action value Iset1；
The fault state self-holding unit comprises a second AND gate, a second OR gate, a first zero sequence current monitoring logic and a widening element, wherein the criterion of the first zero sequence current monitoring logic is that the zero sequence current is larger than the conventional CT disconnection return value Iset2The input end of the second and-gate is respectively connected with the input end of the power flow reversal judging unit and the output end of the second zero sequence current monitoring logic, the input end of the second or-gate is respectively connected with the output end of the second and-gate, the output end of the first zero sequence current monitoring logic and the output end of the widening element, the output end of the second or-gate is connected with the input end of the widening element, and the output end of the widening element is used as the output end of the fault state self-holding unit;
the inverting input end of the inverting operation unit is connected with the output end of the fault state self-holding unit, and the conventional input end of the inverting operation unit is connected with the output end of the second zero sequence current monitoring logic;
and the input end of the time delay element is connected with the arithmetic unit, and the output end of the time delay element is used as a control signal output terminal for CT disconnection.
8. A line protection CT outage lockout system under a load flow reversal condition, comprising a computer device, characterized in that the computer device is programmed or configured to perform the steps of the line protection CT outage lockout method under a load flow reversal condition as claimed in any of claims 1-6, or that the computer device has stored in its memory a computer program programmed or configured to perform the line protection CT outage lockout method under a load flow reversal condition as claimed in any of claims 1-6.
9. A computer readable storage medium having stored thereon a computer program programmed or configured to perform a method of line protection CT outage lockout under a reverse flow condition according to any of claims 1-6.
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| CN113922331B (en) * | 2021-12-14 | 2022-04-12 | 建投遵化热电有限责任公司 | Generator reverse power protection action method, protection terminal and storage medium |
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