CN114977134B - Differential protection method for active power distribution network and related device - Google Patents

Differential protection method for active power distribution network and related device Download PDF

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CN114977134B
CN114977134B CN202210918107.9A CN202210918107A CN114977134B CN 114977134 B CN114977134 B CN 114977134B CN 202210918107 A CN202210918107 A CN 202210918107A CN 114977134 B CN114977134 B CN 114977134B
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line
equation set
action
load
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CN114977134A (en
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向真
杨昆
黄珊
杨锐雄
刘超
蔡仲启
郭晓燕
江霖
赵紫辉
马玉坤
欧仲曦
赵晓燕
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Zhuhai Power Supply Bureau of Guangdong Power Grid 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
    • H02H7/28—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 meshed systems
    • 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
    • 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
    • Y04—INFORMATION OR COMMUNICATION TECHNOLOGIES HAVING AN IMPACT ON OTHER TECHNOLOGY AREAS
    • Y04S—SYSTEMS INTEGRATING TECHNOLOGIES RELATED TO POWER NETWORK OPERATION, COMMUNICATION OR INFORMATION TECHNOLOGIES FOR IMPROVING THE ELECTRICAL POWER GENERATION, TRANSMISSION, DISTRIBUTION, MANAGEMENT OR USAGE, i.e. SMART GRIDS
    • Y04S10/00—Systems supporting electrical power generation, transmission or distribution
    • Y04S10/20—Systems supporting electrical power generation, transmission or distribution using protection elements, arrangements or systems

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  • Artificial Intelligence (AREA)
  • Evolutionary Computation (AREA)
  • Emergency Protection Circuit Devices (AREA)

Abstract

The application discloses an active power distribution network differential protection method and a related device, comprising the following steps: s1, sending current and voltage information of a local terminal to an opposite terminal, judging whether the current and voltage information sent by the opposite terminal is received within preset time, if so, executing a step S2, otherwise, protecting the action; s2, constructing an equivalent regression model containing a circulating current circuit, establishing a first auxiliary criterion equation set and a second auxiliary criterion equation set for analyzing the equivalent regression model, and judging whether a preset main criterion equation is satisfied, if so, performing a protection action, otherwise, performing a step S3; s3, judging whether the equivalent regression model contains an undetectable branch, if so, executing the step S4, otherwise, executing the step S5; s4, judging whether the first auxiliary criterion equation set is met, if so, protecting the action, and otherwise, protecting the non-action; and S5, judging whether a second auxiliary criterion equation set is met, if so, protecting the action, and otherwise, protecting the non-action. The technical problems of low protection performance and poor reliability in the prior art are solved.

Description

Differential protection method for active power distribution network and related device
Technical Field
The present application relates to the field of power technologies, and in particular, to a differential protection method for an active power distribution network and a related device.
Background
Along with the research and development of low-cost voltage sensors, the development of application of microcomputer protection and communication technology, current differential protection with good selectivity and sensitivity is introduced into power distribution network protection to ensure safe and reliable operation of a power distribution network under the condition of distributed power supply access.
The existing technical scheme of current differential protection mainly utilizes double-end current information to construct a protection action criterion. The protection devices installed at both ends of the line receive the current information from the opposite end and subtract the current information from the local end to obtain the differential current. When the power element breaks down, the currents at the two ends are unequal, and the differential current is larger than zero. When the differential current is larger than the setting value of the protection device, the protection device sends an action signal to protect the action and disconnect the circuit breaker of the protected circuit. However, the existing current differential protection technical scheme depends on double-end current information and is easily influenced by current sampling and transmission reliability, on one hand, the power distribution network environment is complex, data is easy to generate large errors in the acquisition and transmission processes, and the protection reliability is reduced; on the other hand, when a line fails, a large fault current easily causes a saturation phenomenon of the current sensor, and often locks or delays related protection actions, so that selectivity and quick action are reduced.
Disclosure of Invention
The application provides a differential protection method and a related device for an active power distribution network, which are used for solving the technical problems of lower protection performance and poorer reliability in the prior art.
In view of this, a first aspect of the present application provides a differential protection method for an active power distribution network, where the method includes:
s1, respectively collecting current information and voltage information of a terminal where a protection device is located, sending the current information and the voltage information of the terminal to an opposite terminal, judging whether the current information and the voltage information sent by the opposite terminal are received within preset time, if so, executing a step S2, otherwise, performing a protection action;
s2, constructing an equivalent regression model containing a circulating current circuit, establishing a first auxiliary criterion equation set and a second auxiliary criterion equation set for analyzing the equivalent regression model, and judging whether a preset main criterion equation is satisfied, if so, performing a protection action, otherwise, performing a step S3;
s3, judging whether the equivalent reduction model contains an undetectable branch, if so, executing a step S4, otherwise, executing a step S5;
s4, judging whether the first auxiliary criterion equation set is met, if so, protecting the action, and otherwise, protecting the non-action;
and S5, judging whether the second auxiliary criterion equation set is met, if so, protecting the action, and otherwise, protecting the non-action.
Optionally, the constructing an equivalent regression model of the circuit containing the circulating current specifically includes:
constructing a first equation set containing a circulating current line and a second equation set between an m end and an n end in the circulating current line according to a kirchhoff voltage law and a current law;
the line current for each line cell in the line containing circulating current is represented as: the method comprises the steps that a first current formula is obtained by the sum of circulating current flowing to the tail end of a line and load distribution current flowing to each line branch, the circulating current is converted through line parameters to obtain a second current formula, and the load distribution current is converted through the line parameters to obtain a third program set;
and constructing the equivalent reduction model based on the first equation set, the second equation set, the first current formula, the second current formula and the third equation set.
Optionally, the first auxiliary criterion equation set is specifically:
Figure 146894DEST_PATH_IMAGE001
；
in the formula (I), the compound is shown in the specification,
Figure 790364DEST_PATH_IMAGE002
representing a set of measurable branches;
Figure 63214DEST_PATH_IMAGE003
and
Figure 729819DEST_PATH_IMAGE004
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure 808633DEST_PATH_IMAGE005
distributing current for load reduced to m side;
Figure 244294DEST_PATH_IMAGE006
distributing current for load reduction to the n side;
Figure 750361DEST_PATH_IMAGE007
for the circulating current to flow to the end of the line,
Figure 904262DEST_PATH_IMAGE008
distributing the current to the load flowing to the line branch.
Optionally, the second auxiliary criterion equation set specifically includes:
Figure 786767DEST_PATH_IMAGE009
；
wherein epsilon is a preset threshold value;
Figure 76935DEST_PATH_IMAGE003
and
Figure 957166DEST_PATH_IMAGE004
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure 395100DEST_PATH_IMAGE005
distributing current for load reduced to m side;
Figure 753401DEST_PATH_IMAGE006
distributing current for load reduction to the n side;
Figure 225970DEST_PATH_IMAGE007
is the circulating current flowing to the end of the line.
Optionally, the main criterion equation is specifically:
Figure 11524DEST_PATH_IMAGE010
；
in the formula (I), the compound is shown in the specification,
Figure 874437DEST_PATH_IMAGE003
and
Figure 98745DEST_PATH_IMAGE004
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure 363505DEST_PATH_IMAGE011
the minimum action current setting value is the minimum action current setting value of the current differential protection.
The second aspect of the present application provides an active power distribution network differential protection system, the apparatus includes:
the first judgment module is used for respectively acquiring current information and voltage information of the end where the protection device is located, sending the current information and the voltage information of the local end to the opposite end, judging whether the current information and the voltage information sent by the opposite end are received within preset time, if so, triggering the second judgment module, and otherwise, protecting the action;
the second judgment module is used for constructing an equivalent reduction model containing a circulating current circuit, establishing a first auxiliary criterion equation set and a second auxiliary criterion equation set for analyzing the equivalent reduction model, judging whether a preset main criterion equation is met, and if the preset main criterion equation is a protection action, triggering a third judgment module;
the third judging module is used for judging whether the equivalent regression model contains an undetectable branch or not, if so, the fourth judging module is triggered, and if not, the fifth judging module is triggered;
the fourth judgment module is used for judging whether the first auxiliary criterion equation set is met, if so, the protection is performed, and otherwise, the protection is not performed;
and the fifth judgment module is used for judging whether the second auxiliary criterion equation set is met, if so, the protection is performed, and otherwise, the protection is not performed.
Optionally, the constructing an equivalent regression model of the circuit containing the circulating current specifically includes:
constructing a first equation set containing a circulating current line and a second equation set between an m end and an n end in the circulating current line according to a kirchhoff voltage law and a current law;
the line current for each line cell in the line containing circulating current is represented as: the method comprises the steps that the sum of circulating current flowing to the tail end of a line and load distribution current flowing to each line branch is obtained to obtain a first current formula, the circulating current is converted through line parameters to obtain a second current formula, and the load distribution current is converted through the line parameters to obtain a third program set;
and constructing the equivalent reduction model based on the first equation set, the second equation set, the first current formula, the second current formula and the third equation set.
Optionally, the first auxiliary criterion equation set specifically includes:
Figure 647855DEST_PATH_IMAGE001
；
in the formula (I), the compound is shown in the specification,
Figure 998065DEST_PATH_IMAGE002
representing a set of measurable branches;
Figure 760485DEST_PATH_IMAGE003
and
Figure 873891DEST_PATH_IMAGE004
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure 266827DEST_PATH_IMAGE005
distributing current for load reduced to m side;
Figure 166649DEST_PATH_IMAGE006
distributing current for load reduction to the n side;
Figure 670443DEST_PATH_IMAGE007
for the circulating current to flow to the end of the line,
Figure 706532DEST_PATH_IMAGE008
distributing current to the load flowing to the line branch;
the second auxiliary criterion equation set specifically includes:
Figure 270369DEST_PATH_IMAGE009
；
wherein epsilon is a preset threshold value;
Figure 595171DEST_PATH_IMAGE003
and
Figure 699393DEST_PATH_IMAGE004
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure 793251DEST_PATH_IMAGE005
distributing current for load reduced to m side;
Figure 590306DEST_PATH_IMAGE006
distributing current for load reduction to the n side;
Figure 136825DEST_PATH_IMAGE007
is the circulating current flowing to the end of the line.
A third aspect of the present application provides an active power distribution network differential protection device, the device comprising a processor and a memory:
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the steps of the active power distribution network differential protection method according to the first aspect, according to instructions in the program code.
A fourth aspect of the present application provides a computer-readable storage medium for storing program code for performing the method of the first aspect.
According to the technical scheme, the method has the following advantages:
the application provides a differential protection method for an active power distribution network, which comprises the following steps: s1, respectively collecting current information and voltage information of a terminal where a protection device is located, sending the current information and the voltage information of a local terminal to an opposite terminal, judging whether the current information and the voltage information sent by the opposite terminal are received within preset time, if so, executing a step S2, otherwise, performing a protection action; s2, constructing an equivalent regression model containing a circulating current circuit, establishing a first auxiliary criterion equation set and a second auxiliary criterion equation set for analyzing the equivalent regression model, and judging whether a preset main criterion equation is satisfied, if so, performing a protection action, otherwise, performing a step S3; s3, judging whether the equivalent regression model contains an undetectable branch, if so, executing a step S4, otherwise, executing a step S5; s4, judging whether the first auxiliary criterion equation set is met, if so, protecting the action, otherwise, protecting the non-action; and S5, judging whether a second auxiliary criterion equation set is met, if so, protecting the action, and otherwise, protecting the non-action.
Compared with the prior art, the protection action auxiliary criterion based on voltage measurement is constructed, the power distribution network differential protection method combining the protection action auxiliary criterion is provided, the problem that the protection performance is reduced or fails due to abnormal current data in CT saturation, data sampling and transmission links and the like can be effectively solved, the reliability and the sensitivity of power distribution network differential protection are effectively improved, the safety and the reliability of a power distribution network under the condition of large-scale new energy access are enhanced, and the construction of a power system with new energy as a main body is supported. Therefore, the technical problems of lower protection performance and poorer reliability in the prior art are solved.
Drawings
Fig. 1 is a schematic flowchart of an embodiment of a differential protection method for an active power distribution network provided in an embodiment of the present application;
FIG. 2 is a schematic diagram of a circuit including a circulating current provided in an embodiment of the present application;
FIG. 3 is a schematic diagram of an equivalent regression with circulating current provided in an embodiment of the present application;
fig. 4 is a schematic structural diagram of an embodiment of an active power distribution network differential protection system provided in the embodiment of the present application.
Detailed Description
In order to make the technical solutions of the present application better understood, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, in an embodiment of the present application, a differential protection method for an active power distribution network includes:
step 101, respectively collecting current information and voltage information of a terminal where a protection device is located, sending the current information and the voltage information of the terminal to an opposite terminal, judging whether the current information and the voltage information sent by the opposite terminal are received within preset time, if so, executing step 102, otherwise, performing protection action;
it should be noted that the protection devices at the two ends of the power line respectively collect the current and voltage information of the end where the protection device is located and the current information of all measurable branch lines on the line (for subsequent step determination), and send the voltage and current information of the local end to the opposite end. When the protection device at one end can not receive the data sent by the opposite end within the time Tmax, the protection action is carried out, and the value of the Tmax depends on the communication condition of the site and the requirement on the protection fault removal time. Step 102 is executed when the protection device at one end can receive the data sent by the opposite end.
102, constructing an equivalent regression model containing a circulating current circuit, establishing a first auxiliary criterion equation set and a second auxiliary criterion equation set for analyzing the equivalent regression model, and judging whether a preset main criterion equation is satisfied, if so, performing a protection action, otherwise, performing a step 103;
it should be noted that, the process of constructing the equivalent regression model with the circulating current line in this embodiment is as follows:
1) Definition and solution of circulating current:
in the line shown in fig. 2, according to kirchhoff's voltage law and current law, the following equations hold:
Figure 310317DEST_PATH_IMAGE012
（1）
in the formula (I), the compound is shown in the specification,
Figure 258681DEST_PATH_IMAGE013
and
Figure 164321DEST_PATH_IMAGE014
respectively representing the voltages across the line mn;
Figure 260453DEST_PATH_IMAGE015
representing the current flowing in from the end m,
Figure 644161DEST_PATH_IMAGE016
representing the current flowing in from the n terminal.
Figure 712611DEST_PATH_IMAGE017
And
Figure 851468DEST_PATH_IMAGE018
representing the current of branch 1 and branch 2, respectively.
Figure 372579DEST_PATH_IMAGE019
Representing the current of the line mn between branch 1 and branch 2.
Figure 559978DEST_PATH_IMAGE020
Representing the impedance of the line mn between branch 1 and branch 2.
Figure 545252DEST_PATH_IMAGE021
Representing the impedance of the line between node m and branch 1.
Figure 792693DEST_PATH_IMAGE022
Representing the impedance of the line between node n and branch 2.
Then, the currents on both sides can be expressed as:
Figure 801101DEST_PATH_IMAGE023
（2）
for each line element, the current flowing through the line termination can be split into two parts, one being the circulating current flowing to the end of the line, denoted as
Figure 854507DEST_PATH_IMAGE007
The current of the part is independent of the load distribution and the load size connected with the circuit unit; the other part distributes the current for the load flowing to each line branch, denoted as
Figure 631970DEST_PATH_IMAGE024
The partial current is calculated by load current of each branch according to network parameters, and the conditions of all branches need to be considered. Thus, line current
Figure 112630DEST_PATH_IMAGE025
Can be expressed as:
Figure 336895DEST_PATH_IMAGE026
（3）
when the line terminal voltage is known, the circulating current can be calculated by line parameters, and then:
Figure 131676DEST_PATH_IMAGE027
（4）
in the formula (I), the compound is shown in the specification,
Figure 763645DEST_PATH_IMAGE028
is the impedance of the line mn.
The load distribution current is distributed according to the impedance value, and considering the multi-branch condition, the load distribution current comprises the following components:
Figure 352890DEST_PATH_IMAGE029
（5）
in the formula (I), the compound is shown in the specification,
Figure 398206DEST_PATH_IMAGE030
distributing the current to the load flowing to line branch i.
Figure 731098DEST_PATH_IMAGE031
Is the current reduced to branch i at the m terminal.
Figure 217575DEST_PATH_IMAGE032
Is the current reduced to branch i at the n terminal.
2) Equivalent reduction including circulating current:
after completing the circulating current calculation based on equations (1) - (5), the line model can be equivalently reduced by using the model shown in fig. 3. The equivalent regression model of the circulating current is the realization basis of a new protection principle.
After equivalent reduction of the circulating current, the branches of the line can be translated to the end points for analysis, as shown in fig. 3, and this process does not cause a change in the voltage current at the end points.
It should be noted that, the process of establishing the first auxiliary criterion equation set and the second auxiliary criterion equation set for analyzing the equivalent regression model in the present embodiment is as follows:
1) Protection principle under branch measurable condition:
as shown in fig. 3, in a normal case, the current magnitude of the end point is always equal to the sum of the magnitudes of the load distribution current equivalent to the end point and the circulating current, that is, equation (6) holds.
Figure 305616DEST_PATH_IMAGE033
（6）
In the formula (I), the compound is shown in the specification,
Figure 510333DEST_PATH_IMAGE003
and
Figure 381337DEST_PATH_IMAGE004
respectively a current flowing from the m terminal and a current flowing from the n terminal,
Figure 50215DEST_PATH_IMAGE005
distributing current for load reduced to m side;
Figure 246842DEST_PATH_IMAGE006
distributing the current for the reduction to the n-side load.
In the case of an external fault, the existence of the fault point does not affect the identity relationship between the circulating current and the load distribution current and the endpoint measurement current, and therefore, the inequality is still constant under the condition of the external fault.
When a fault occurs in a zone, the existence of a fault branch is considered, and at the moment, the relation between the terminal point measurement current and the circulating current and the load distribution current evolves as follows:
Figure 673275DEST_PATH_IMAGE034
（7）
in the formula (I), the compound is shown in the specification,
Figure 675866DEST_PATH_IMAGE035
to reduce the fault branch current to the m terminal.
Figure 136934DEST_PATH_IMAGE036
For the fault branch current to the n terminal;
combining the above considerations, and further considering the existence of measurement errors, etc., the protection criterion (second auxiliary criterion equation set) including the circulating current is set as follows:
Figure 238882DEST_PATH_IMAGE037
（8）
the fixed value epsilon on the right side of the protection criterion can be taken as a smaller fixed threshold value (namely epsilon is preset);
Figure 480508DEST_PATH_IMAGE003
and
Figure 958894DEST_PATH_IMAGE004
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure 336785DEST_PATH_IMAGE005
distributing current for load reduced to m side;
Figure 875214DEST_PATH_IMAGE038
distributing current for load reduction to the n side;
Figure 338557DEST_PATH_IMAGE007
is the circulating current flowing to the end of the line.
2) Protection principle with non-measurable branches:
due to the existence of the non-measurable branch, the left side of the inequality cannot be directly obtained through measurement and calculation, and the branch related to the non-measurable branch should be kept at the right side of the inequality. When the maximum possible occurrence attribution value of the non-measurable branch to each endpoint is considered in the setting of the fixed value, the protection criterion (the first auxiliary criterion equation set) can be expressed as follows:
Figure 620633DEST_PATH_IMAGE039
（9）
in the formula (I), the compound is shown in the specification,
Figure 118611DEST_PATH_IMAGE002
representing a set of measurable branches;
Figure 562362DEST_PATH_IMAGE003
and
Figure 710403DEST_PATH_IMAGE004
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure 592908DEST_PATH_IMAGE005
distributing current for load reduced to m side;
Figure 883075DEST_PATH_IMAGE006
distributing current for load reduction to the n side;
Figure 497728DEST_PATH_IMAGE007
for the circulating current to flow to the end of the line,
Figure 935662DEST_PATH_IMAGE008
distributing the current to the load flowing to the line branch.
For normal situations and situations where external faults occur: the measured current at the endpoint, minus the circulating current and the measurable branch load distribution current, will equal the non-measurable branch load distribution current value attributed to the endpoint measurement. Normally and in the case of an external fault, this current value will always be less than the maximum load current distribution of the non-measurable branch, and therefore the above criterion is not active.
On the contrary, when a fault occurs on the line, the fault branch generates additional distributed current for both end points, which is represented as the increase of the value of the current measured by the end points, so that the calculation result on the left side of the criterion is raised, and once the raising effect exceeds the return value of the maximum load current on the right side, the protection action is carried out.
It should be noted that, in this embodiment, the selection of the main criterion is not specifically limited, and the main criterion is constructed according to equation (10):
Figure 559541DEST_PATH_IMAGE040
（10）
in the formula (I), the compound is shown in the specification,
Figure 704215DEST_PATH_IMAGE003
and
Figure 817665DEST_PATH_IMAGE004
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively; iop is the minimum action current setting value of the current differential protection.
It will be appreciated that when the main criterion is met, then a protection action is taken; and when the main criterion is not satisfied, judging the auxiliary criterion, if the auxiliary criterion is satisfied, protecting the action, otherwise, protecting the non-action.
Step 103, judging whether the equivalent regression model contains an undetectable branch, if so, executing step 104, otherwise, executing step 105;
step 104, judging whether the first auxiliary criterion equation set is met, if so, protecting the action, otherwise, protecting the non-action;
and 105, judging whether the second auxiliary criterion equation set is met, if so, protecting the action, and otherwise, protecting the non-action.
The foregoing is an embodiment of a differential protection method for an active power distribution network provided in the embodiment of the present application, and the following is an embodiment of a differential protection system for an active power distribution network provided in the embodiment of the present application.
Referring to fig. 4, an active power distribution network differential protection system provided in an embodiment of the present application includes:
the first judgment module 201 is configured to collect current information and voltage information of an end where the protection device is located, send the current information and voltage information of the local end to the opposite end, judge whether the current information and voltage information sent by the opposite end are received within a preset time, trigger the second judgment module if the current information and voltage information are received, and otherwise, perform a protection action;
the second judgment module 202 is used for constructing an equivalent reduction model containing a circulating current circuit, establishing a first auxiliary criterion equation set and a second auxiliary criterion equation set for analyzing the equivalent reduction model, judging whether a preset main criterion equation is met, and if the preset main criterion equation is a protection action, triggering a third judgment module;
the third judging module 203 is used for judging whether the equivalent reduction model contains an undetectable branch, if so, triggering the fourth judging module, and otherwise, triggering the fifth judging module;
a fourth judging module 204, configured to judge whether the first auxiliary criterion equation set is satisfied, if so, protect the action, and otherwise, protect the non-action;
a fifth determining module 205, configured to determine whether the second auxiliary criterion equation set is satisfied, if so, the protection is performed, and otherwise, the protection is not performed.
Further, the embodiment of the present application also provides an active power distribution network differential protection device, where the device includes a processor and a memory:
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the steps of the active power distribution network differential protection method according to the first aspect, according to instructions in the program code.
Further, a computer-readable storage medium is provided in an embodiment of the present application, and the computer-readable storage medium is used for storing a program code, and the program code is used for executing the method according to the first aspect.
It can be clearly understood by those skilled in the art that, for convenience and brevity of description, the specific working processes of the system and the module described above may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The terms "first," "second," "third," "fourth," and the like in the description of the present application and in the above-described drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those illustrated or otherwise described herein. Moreover, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
It should be understood that, in this application, "at least one" means one or more, "a plurality" means two or more. "and/or" for describing an association relationship of associated objects, indicating that there may be three relationships, e.g., "a and/or B" may indicate: only A, only B and both A and B are present, wherein A and B may be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single item(s) or plural items. For example, at least one (one) of a, b, or c, may represent: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", wherein a, b, c may be single or plural.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or contributed to by the prior art, or all or part of the technical solution may be embodied in a software product, which is stored in a storage medium and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present application. And the aforementioned storage medium includes: a U disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk.
The above embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.

Claims (6)

1. A differential protection method for an active power distribution network is characterized by comprising the following steps:
s1, respectively collecting current information and voltage information of a terminal where a protection device is located, sending the current information and the voltage information of the terminal to an opposite terminal, judging whether the current information and the voltage information sent by the opposite terminal are received within preset time, if so, executing a step S2, otherwise, performing a protection action;
s2, constructing an equivalent regression model containing a circulating current circuit, establishing a first auxiliary criterion equation set and a second auxiliary criterion equation set for analyzing the equivalent regression model, and judging whether a preset main criterion equation is satisfied, if so, performing a protection action, otherwise, performing a step S3;
s3, judging whether the equivalent regression model contains an undetectable branch, if so, executing a step S4, otherwise, executing a step S5;
s4, judging whether the first auxiliary criterion equation set is met, if so, protecting the action, and otherwise, protecting the non-action;
s5, judging whether the second auxiliary criterion equation set is met, if so, protecting the action, otherwise, protecting the non-action;
the first auxiliary criterion equation set specifically includes:
Figure QLYQS_1
；
in the formula (I), the compound is shown in the specification,
Figure QLYQS_2
representing a set of measurable branches;irepresenting a branch in all the branch sets;
Figure QLYQS_7
and
Figure QLYQS_12
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure QLYQS_4
distributing current for load reduced to m side;
Figure QLYQS_8
distributing current for load reduction to the n side;
Figure QLYQS_10
distributing the sum of the currents for the load on the m side;
Figure QLYQS_14
distributing the sum of the currents for the load on the n side;
Figure QLYQS_3
for the circulating current to flow to the end of the line,
Figure QLYQS_6
distributing current to the load flowing to the line branch;
Figure QLYQS_11
the sum of the load distribution currents of all measurable branches to the m end is calculated;
Figure QLYQS_13
summing the load distribution currents to the n-terminal for all measurable branches;
Figure QLYQS_5
the sum of the maximum load distribution currents which can occur is reduced to the m end for all the unmeasurable branches;
Figure QLYQS_9
the sum of the maximum load distribution currents which can occur is reduced to the n end for all the unmeasurable branches;
the second auxiliary criterion equation set specifically includes:
Figure QLYQS_15
；
in the formula (I), the compound is shown in the specification,
Figure QLYQS_16
is a preset threshold value;
the main criterion equation is specifically as follows:
Figure QLYQS_17
；
in the formula (I), the compound is shown in the specification,I op the minimum action current setting value is the minimum action current setting value of the current differential protection.
2. The differential protection method for the active power distribution network according to claim 1, wherein the constructing of the equivalent regression model of the circuit containing the circulating current specifically comprises:
constructing a first equation set containing a circulating current line and a second equation set between an m end and an n end in the circulating current line according to a kirchhoff voltage law and a current law;
the line current for each line cell in the line containing circulating current is represented as: the method comprises the steps that a first current formula is obtained by the sum of circulating current flowing to the tail end of a line and load distribution current flowing to each line branch, the circulating current is converted through line parameters to obtain a second current formula, and the load distribution current is converted through the line parameters to obtain a third program set;
and constructing the equivalent reduction model based on the first equation set, the second equation set, the first current formula, the second current formula and the third equation set.
3. An active power distribution network differential protection system, comprising:
the first judgment module is used for respectively acquiring current information and voltage information of the end where the protection device is located, sending the current information and the voltage information of the local end to the opposite end, judging whether the current information and the voltage information sent by the opposite end are received within preset time, if so, triggering the second judgment module, and otherwise, protecting the action;
the second judgment module is used for constructing an equivalent reduction model containing a circulating current circuit, establishing a first auxiliary criterion equation set and a second auxiliary criterion equation set which are used for analyzing the equivalent reduction model, judging whether a preset main criterion equation is met, and if the preset main criterion equation is a protection action, triggering a third judgment module;
the third judging module is used for judging whether the equivalent regression model contains an undetectable branch or not, if so, the fourth judging module is triggered, and if not, the fifth judging module is triggered;
the fourth judgment module is used for judging whether the first auxiliary criterion equation set is met, if so, the protection is performed, and otherwise, the protection is not performed;
a fifth judging module, configured to judge whether the second auxiliary criterion equation set is satisfied, if so, protect the action, and otherwise, protect the non-action;
the first auxiliary criterion equation set specifically includes:
Figure QLYQS_18
；
in the formula (I), the compound is shown in the specification,
Figure QLYQS_20
representing a set of measurable branches;irepresenting a branch in all the branch sets;
Figure QLYQS_25
and
Figure QLYQS_28
the current flowing from the end m of the current line and the current flowing from the end n of the current line are respectively;
Figure QLYQS_21
distributing current for load reduced to m side;
Figure QLYQS_23
distributing current for load reduction to the n side;
Figure QLYQS_29
distributing the sum of the currents for the load on the m side;
Figure QLYQS_31
distributing the sum of the currents for the load on the n side;
Figure QLYQS_19
for the circulating current to flow to the end of the line,
Figure QLYQS_26
distributing current to the load flowing to the line branch;
Figure QLYQS_27
the sum of the load distribution currents of all measurable branches to the m end is calculated;
Figure QLYQS_30
the sum of the load distribution currents to the n end is reduced for all the measurable branches;
Figure QLYQS_22
the sum of the maximum load distribution currents which can occur is reduced to the m end for all the unmeasurable branches;
Figure QLYQS_24
the sum of the maximum load distribution currents which can occur is reduced to the n end for all the unmeasurable branches;
the second auxiliary criterion equation set specifically includes:
Figure QLYQS_32
；
in the formula (I), the compound is shown in the specification,
Figure QLYQS_33
is a preset threshold value;
the main criterion equation is specifically as follows:
Figure QLYQS_34
；
in the formula (I), the compound is shown in the specification,I op the minimum action current setting value is the minimum action current setting value of the current differential protection.
4. The active power distribution network differential protection system according to claim 3, wherein the constructing of the equivalent regression model including the circulating current line specifically includes:
constructing a first equation set containing a circulating current line and a second equation set between an m end and an n end in the circulating current line according to a kirchhoff voltage law and a current law;
the line current for each line cell in the line containing circulating current is represented as: the method comprises the steps that the sum of circulating current flowing to the tail end of a line and load distribution current flowing to each line branch is obtained to obtain a first current formula, the circulating current is converted through line parameters to obtain a second current formula, and the load distribution current is converted through the line parameters to obtain a third program set;
and constructing the equivalent reduction model based on the first equation set, the second equation set, the first current formula, the second current formula and the third equation set.
5. An active power distribution network differential protection device, comprising a processor and a memory:
the memory is used for storing program codes and transmitting the program codes to the processor;
the processor is configured to execute the active power distribution network differential protection method according to any one of claims 1-2 according to instructions in the program code.
6. A computer-readable storage medium, characterized in that the computer-readable storage medium is used for storing program code for performing the active power distribution network differential protection method according to any of claims 1-2.
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CN102629754B (en) * 2012-03-31 2014-03-19 积成电子股份有限公司 Substation area back-up protecting method based on current differential principle
CN103427405B (en) * 2013-08-16 2016-08-10 华南理工大学 The differential guard method of transmission line of electricity based on Higher Order Cumulants
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