CN108155645B - Closed loop judgment method and device for factory and mine power distribution network - Google Patents

Closed loop judgment method and device for factory and mine power distribution network Download PDF

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CN108155645B
CN108155645B CN201711446493.1A CN201711446493A CN108155645B CN 108155645 B CN108155645 B CN 108155645B CN 201711446493 A CN201711446493 A CN 201711446493A CN 108155645 B CN108155645 B CN 108155645B
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孙妍
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Ceristar Electric Co ltd
Capital Engineering & Research Inc Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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Abstract

The invention provides a loop closing judgment method and a loop closing judgment device for a factory and mine power distribution network, wherein the method comprises the following steps: establishing an external network equivalent model of the closed-loop network according to boundary nodes between the closed-loop network and a superior network; calculating to obtain equivalent impedance of the loop closing network according to the external network equivalent model; calculating the steady-state current and the transient-state current of the loop closing network according to the voltage difference at the two sides of the interconnection switch and the equivalent impedance of the loop closing network; and when the steady-state current and the transient-state current of the loop closing network are determined to be smaller than the relay protection current threshold and the equipment rated through-current threshold, judging that the loop closing of the distribution network is possible. The invention can be generally suitable for loop closing operation of various plant and mine power distribution networks, has accurate judgment, reduces the risk of loop closing operation of plant and mine enterprises, avoids unnecessary power failure and improves the reliability of power supply.

Description

Closed loop judgment method and device for factory and mine power distribution network
Technical Field
The invention relates to the field of plant and mine power distribution, in particular to a loop closing judgment method and system for a plant and mine power distribution network.
Background
When a power distribution system of a factory and mine enterprise is planned, in order to improve the power supply reliability, a dual-power supply or multi-power supply structure is generally adopted, and the principle of closed-loop design and open-loop operation is followed. When a certain bus, switch or feeder needs to be overhauled or has a fault, the load of multi-power supply on the bus, switch or feeder needs to be transferred, and the loop closing operation is carried out by operating the interconnection switch, so that the power failure time can be reduced, and the power supply continuity can be improved. The loop closing operation is an operation of switching two or more distribution lines of the same voltage class from a radiation-shaped wiring to a ring-shaped wiring by closing the interconnection switch under the condition of ensuring no power outage. If the direct ring closing operation that closes, because the contact switch both sides voltage phase difference is great, feeder initial load is heavier, leads to closing the ring after the electric current too big, arouses the protection tripping operation, equipment overload, influences safety in production. Therefore, the loop closing judgment is needed before the loop closing.
At present, during loop closing operation, voltage amplitude difference at two sides of a tie switch is generally determined through a voltage transformer, a voltage phase difference is determined through a nuclear phase instrument, and then test analysis is carried out according to the voltage phase difference and a voltage vector angle to judge whether loop closing can be carried out or not. For example, the enterprise recommends to control the difference between effective values of the voltages on both sides of the tie switch before loop closing to be within 0.3kV and to control the voltage phase angle to be within 3 degrees. The technology has the defects that a reasonable power distribution network closed loop analysis model and theoretical derivation are lacked, qualitative analysis and quantitative analysis are obtained by a test method, the judgment result is not accurate and is limited by a test area, the empirical value obtained by the test analysis is not universal, and the technology cannot be applied to closed loop operation of power distribution networks of other factory and mining enterprises.
Disclosure of Invention
The embodiment of the invention provides a loop closing judgment method for a factory and mine power distribution network, which is used for improving the accuracy of loop closing judgment and improving the reliability of power supply and comprises the following steps:
establishing an external network equivalent model of the closed-loop network according to boundary nodes between the closed-loop network and a superior network;
calculating to obtain equivalent impedance of the loop closing network according to the external network equivalent model;
calculating the steady-state current and the transient-state current of the loop closing network according to the voltage difference at the two sides of the interconnection switch and the equivalent impedance of the loop closing network;
when it is determined that the steady-state current and the transient-state current of the loop closing network are smaller than the relay protection current threshold and the equipment rated through-current threshold, judging that the loop closing of the distribution network is possible;
the calculating and obtaining the equivalent impedance of the loop closing network according to the external network equivalent model comprises the following steps:
calculating to obtain the external network injection power according to the external network equivalent model of the closed-loop network;
obtaining equivalent impedance of a loop closing network according to the injected power of an external network;
the external network injection power is obtained by calculation according to the external network equivalent model of the closed-loop network, and the calculation is carried out according to the following formula:
Figure GDA0002843835320000021
wherein EYEQInjecting power for an external network; u shapeBIs the voltage of the boundary node; u shapeAIs the voltage of the loop closing network; u shapeCIs the voltage of the external network; sBIs the power of the border node; sAIs the power of the loop closing network; sCPower for an external network; y isBCIs the mutual admittance between the external network and the boundary node; y isCCSelf-admittance to an external network;
the equivalent impedance of the loop closing network is obtained according to the injected power of the external network, and the equivalent impedance is calculated according to the following formula:
Figure GDA0002843835320000022
Figure GDA0002843835320000023
wherein, yiThe admittance of the ith branch of the loop closing network; i is 1,2, y1For admittance, y, of the 1 st branch of the loop-closing network2Is the admittance of the 2 nd branch of the loop closing network; zeqIs the equivalent impedance of the loop closing network; siIs the power of the border node; u shapeiIs the voltage of the boundary node.
The embodiment of the invention also provides a loop closing judgment device of the plant and mine power distribution network, which is used for improving the accuracy of loop closing judgment and improving the reliability of power supply and comprises the following steps:
the model establishing module is used for establishing an external network equivalent model of the closed-loop network according to boundary nodes between the closed-loop network and a superior network;
the equivalent impedance obtaining module is used for calculating and obtaining equivalent impedance of the closed loop network according to the external network equivalent model;
the current calculation module is used for calculating the steady-state current and the transient-state current of the loop closing network according to the voltage difference at the two sides of the interconnection switch and the equivalent impedance of the loop closing network;
the loop closing judgment module is used for judging that the distribution network can close the loop when determining that the steady-state current and the transient-state current of the loop closing network are smaller than the relay protection current threshold and the equipment rated through-flow threshold;
the equivalent impedance obtaining module further comprises:
the injection power acquisition submodule is used for calculating and acquiring the injection power of the external network according to the external network equivalent model of the closed-loop network;
the impedance obtaining submodule is used for obtaining equivalent impedance of the loop closing network according to the external network injection power;
the injection power acquisition submodule is calculated according to the following formula:
Figure GDA0002843835320000031
wherein EYEQInjecting power for an external network; u shapeBIs the voltage of the boundary node; u shapeAIs the voltage of the loop closing network; u shapeCIs the voltage of the external network; sBIs the power of the border node; sAIs the power of the loop closing network; sCPower for an external network; y isBCIs the mutual admittance between the external network and the boundary node; y isCCSelf-admittance to an external network;
the impedance obtaining submodule is used for calculating according to the following formula:
Figure GDA0002843835320000032
Figure GDA0002843835320000033
wherein, yiIs a loop closing networkAdmittance of the i branches; i is 1,2, y1For admittance, y, of the 1 st branch of the loop-closing network2Is the admittance of the 2 nd branch of the loop closing network; zeqIs the equivalent impedance of the loop closing network; siIs the power of the border node; u shapeiIs the voltage of the boundary node.
The embodiment of the invention also provides computer equipment which comprises a memory, a processor and a computer program which is stored on the memory and can be run on the processor, wherein the processor executes the computer program to realize the loop closing judgment method of the power distribution network of the factory and the mine.
The embodiment of the invention also provides a computer readable storage medium, and the computer readable storage medium stores a computer program for executing the loop closing judgment method of the factory and mine power distribution network.
According to the closed-loop judging method of the factory and mine power distribution network, firstly, an external network equivalent model of the closed-loop network needs to be established, external network equivalent impedance is obtained, and then transient current and steady-state current of the closed-loop network are obtained according to voltage difference on two sides of a contact switch; and finally, judging whether loop closing operation can be carried out or not according to the steady-state current and the transient-state current of the loop closing network. The loop closing judgment method of the factory and mine power distribution network provided by the embodiment of the invention judges based on the current of the loop closing network, has accurate judgment result and universality, can be suitable for loop closing operation of various factory and mine enterprise power distribution networks, reduces the risk of loop closing operation of the factory and mine enterprises, avoids unnecessary power failure and improves the power supply reliability.
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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. In the drawings:
FIG. 1 is a schematic flow chart of a loop closing judgment method for a power distribution network of a plant and a mine according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of loop closing judgment in an embodiment of the present invention;
FIG. 3 is a schematic diagram illustrating the division of an internal network and an external network according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a balancing node in an embodiment of the invention;
fig. 5a and 5b are schematic diagrams for determining the steady-state current of the loop closing network in the embodiment of the invention;
FIG. 6 is a schematic diagram of an equivalent circuit for loop closing network transient current calculation according to an embodiment of the present invention;
FIG. 7 is a schematic structural diagram of a loop closing judgment device of a factory and mine power distribution network according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of an equivalent impedance obtaining module in the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. The exemplary embodiments and descriptions of the present invention are provided to explain the present invention, but not to limit the present invention.
When the loop closing operation is carried out in an enterprise, the failure reason is mainly that a certain incoming line breaker trips because of the action of a relay protection device, and all loads carried by two sections of buses of the loop closing lose power. The relay protection action is mainly caused by the fact that a large loop closing current is generated by loop closing operation, and therefore the protection action is caused. This large loop closing current is often accompanied by overload of the main transformer and the current-carrying conductor while causing a protective action, and poses a great threat to system safety. Therefore, the inventors considered that, in order to determine whether or not the loop closing operation is successful, it is necessary to calculate the loop closing current first and determine whether or not the loop closing operation is possible based on the loop closing current.
Based on the above reasons, an embodiment of the present invention provides a loop closing judgment method for a plant and mine power distribution network, so as to improve accuracy of loop closing judgment and improve reliability of power supply, as shown in fig. 1, the method includes:
101: establishing an external network equivalent model of the closed-loop network according to boundary nodes between the closed-loop network and a superior network;
102: calculating to obtain equivalent impedance of the loop closing network according to the external network equivalent model;
103: calculating the steady-state current and the transient-state current of the loop closing network according to the voltage difference at the two sides of the interconnection switch and the equivalent impedance of the loop closing network;
104: and when the steady-state current and the transient-state current of the loop closing network are determined to be smaller than the relay protection current threshold and the equipment rated through-current threshold, judging that the loop closing of the distribution network is possible.
In an embodiment, when it is determined that the steady-state current and the transient-state current of the loop closing network are smaller than the relay protection current threshold and the device rated current threshold, the power distribution network is determined to be capable of closing the loop, and various embodiments are possible, for example, as shown in fig. 2, when the steady-state current and the transient-state current of the loop closing network satisfy the following conditions, it is determined that the power distribution network is capable of closing the loop:
I＞dz＞Ic；
I≥dz＞Iim；
ITR.e＞Ic；
wherein, I >dzIndicating overcurrent constant value of relay protection device, I ≧dzIndicating the quick-break constant of the protective relaying device, ITR.eIndicating the overload capability of the transformer, IcRepresents the steady-state current, IimRepresenting a transient current.
In one embodiment, as shown in fig. 2, if the loop closing cannot be performed directly, the parameters of the loop closing network may be adjusted until the loop closing operation is performed. For example, when it is determined that the steady-state current and the transient current of the loop closing network are not less than the relay protection current threshold and the device rated through-current threshold, the voltage difference between the two sides of the interconnection switch is adjusted, the steady-state current and the transient current of the loop closing network are recalculated according to the adjusted voltage difference until the steady-state current and the transient current of the loop closing network are less than the relay protection current threshold and the device rated through-current threshold, and it is determined that the distribution network can close the loop. After the loop closing is judged to be possible, a loop closing permission instruction can be sent out. If the loop closing is still not allowed after the parameters are adjusted, an instruction that the loop closing is not allowed can be issued.
In one embodiment, the loop-closing network equivalent impedance obtained by calculation according to the external network equivalent model can be obtained in various real-time modes, for example, the external network injection power can be obtained by calculation according to the external network equivalent model of the loop-closing network; and obtaining equivalent impedance of the loop closing network according to the injected power of the external network. In the implementation, because the external network is relatively complex and may change, the electrical room performing the loop closing operation is difficult to obtain the parameters of the external network, and for this problem, the external network may be equalized by using an improved Ward equivalence method, which includes the following specific steps:
as shown in fig. 3, for a factory and mine enterprise, only one or two boundary nodes exist between a 10kV loop closing network and a superior network, in order to meet the requirement of calculation, a bus to be loop closed is used as a boundary bus, a boundary bus and an internal network (system) are used as research systems, and an external network is used outside the boundary bus. The connection branch of the internal network (system) and the boundary bus becomes a tie line. Subset a represents the internal network, subset B is the set of boundary nodes (boundary busbars), subset C is the set of external nodes, and the electrical connection of the system can be represented by the following linear equation:
Figure GDA0002843835320000061
wherein, Y represents the self-admittance of each node and the mutual admittance among the nodes, U represents the voltage of each node, I represents the injection current of each node, C represents an external node, B represents a boundary node, and A represents an internal node;
removing external nodes from the above formula, i.e. removing UCThe following equation can be obtained:
Figure GDA0002843835320000062
in practical applications, power may be used instead of current, and the equation is transformed into:
Figure GDA0002843835320000063
if it is not
Figure GDA0002843835320000064
Will be defined as:
Figure GDA0002843835320000065
equation (2) can be written as:
Figure GDA0002843835320000066
wherein EYEQInjecting power for an external network; u shapeBIs the voltage of the boundary node; u shapeAIs the voltage of the loop closing network; u shapeCIs the voltage of the external network; sBIs the power of the border node; sAIs the power of the loop closing network; sCPower for an external network; y isBCIs the mutual admittance between the external network and the boundary node; y isCCSelf-admittance to an external network;
external network injected power is distributed to injected power delta values on boundary nodes if node voltage is known
Figure GDA0002843835320000071
Comprises the following steps:
Figure GDA0002843835320000072
the external network injection power may be calculated by:
Figure GDA0002843835320000073
Figure GDA0002843835320000074
wherein S is1、S2、SRRepresents node injected power, y1、y2、yRDenotes admittance of a branch, YB12The admittance value of an equivalent branch between nodes on two sides of the equivalent network is obtained; seq1、Seq2Injection power, S, calculated for two boundary nodes in the base state using equation (5) aboveB12Is the power, S, of equivalent branch between two boundary nodes of Ward equivalentt1、St2And obtaining the power of the connecting line to be closed for real-time measurement.
As shown in fig. 4, the equivalent impedance of the loop closing network is looked at from the loop closing port, and is traced back to the power supply point from the loop closing point, i.e. the sum of the impedances of the balanced nodes, and R is the balanced node.
In the graph, B1 and B2 represent two boundary nodes, and the power of the balanced node is as follows:
Figure GDA0002843835320000075
the voltages of the two boundary nodes are respectively U1And U2Can be obtained by actual measurement data of the closed loop system, so that the voltage U of the balance node can be obtainedR：
Figure GDA0002843835320000076
Then, the admittance y of the balance node is obtainedRAdmittance y of loop-closing network branchi：
Figure GDA0002843835320000077
Figure GDA0002843835320000078
Finally, the equivalent impedance Z of the loop closing network is obtained by calculation according to the following formulaeq：
Figure GDA0002843835320000081
Wherein Z iseqIs the equivalent impedance of the loop closing network; siIs the power of the border node; y is1、y2、yiIs admittance of a loop closing network branch; u shapeiIs the voltage of the boundary node.
In one embodiment, since the magnitude of the loop closing current is related to the voltage difference between the two sides of the interconnection switch and the equivalent impedance of the loop closing network, after the voltage difference between the two sides of the interconnection switch is measured and the equivalent impedance of the loop closing network is obtained through calculation, the steady-state current and the transient current of the loop closing network can be obtained through calculation. The steady-state current and the transient-state current of the loop closing network can be calculated according to the voltage difference between the two sides of the interconnection switch and the equivalent impedance of the external network, and the calculation can be implemented in various ways, for example, the calculation can include:
as shown in fig. 5a and 5b, the network in the figure can be decomposed into two networks, one is a radial network (fig. 5a) and the other is a ring network (fig. 5b), the network formed by the two boundaries can be calculated, and the calculated results are superposed to obtain the steady-state current of the whole network. There are various embodiments for obtaining the steady-state current, for example, the steady-state current can be calculated according to the following formula:
Figure GDA0002843835320000082
wherein, IcIs the steady-state current of the loop closing network; u shapeocTo communicate the voltage difference across the switch; zeqIs the equivalent impedance of the loop closing network;
there are various embodiments for determining the transient current of the loop closing network, for example, as shown in fig. 6, the differential equation of the loop closing network after loop closing is as follows:
Figure GDA0002843835320000083
wherein E ismRepresents an electric potential; r represents the resistance of the equivalent impedance of the loop closing network, and L represents the inductance of the equivalent impedance of the loop closing network;
after solving the differential equation, the transient current is calculated according to the following formula:
Figure GDA0002843835320000084
wherein, IimTransient current of loop closing network; t isaIs a time constant; i isctIs the steady-state current of the loop closing network.
Based on the same inventive concept, the embodiment of the present invention further provides a loop closing determination apparatus for a factory and mine power distribution network, as described in the following embodiments. Because the principle of solving the problems of the loop closing judgment device of the factory and mine power distribution network is similar to the loop closing judgment method of the factory and mine power distribution network, the implementation of the loop closing judgment device of the factory and mine power distribution network can refer to the implementation of the loop closing judgment method of the factory and mine power distribution network, and repeated parts are not repeated.
Fig. 7 is a loop closing judgment device of a factory and mine power distribution network according to an embodiment of the present invention. As shown in fig. 7, the loop closing judgment device for a factory and mine power distribution network according to the embodiment of the present invention includes:
a model establishing module 701 for establishing an external network equivalent model of the closed-loop network according to a boundary node between the closed-loop network and a superior network;
an equivalent impedance obtaining module 702, configured to calculate and obtain an equivalent impedance of the closed-loop network according to an external network equivalent model;
the current calculation module 703 is used for calculating the steady-state current and the transient-state current of the loop closing network according to the voltage difference at the two sides of the interconnection switch and the equivalent impedance of the loop closing network;
and the loop closing judgment module 704 is configured to judge that the distribution network can close the loop when it is determined that the steady-state current and the transient-state current of the loop closing network are smaller than the relay protection current threshold and the device rated through-current threshold.
In one embodiment, the closed-loop determining module is further configured to:
and when the steady-state current and the transient-state current of the closed-loop network are determined to be not less than the relay protection current threshold and the equipment rated through-flow threshold, adjusting the voltage difference at two sides of the interconnection switch, recalculating the steady-state current and the transient-state current of the closed-loop network according to the adjusted voltage difference until the steady-state current and the transient-state current of the closed-loop network are less than the relay protection current threshold and the equipment rated through-flow threshold, and judging that the power distribution network can be closed.
In an embodiment, as shown in fig. 8, the equivalent impedance obtaining module further includes:
the injection power obtaining sub-module 801 is used for calculating and obtaining external network injection power according to an external network equivalent model of the closed-loop network;
and the impedance obtaining submodule 802 is configured to obtain an equivalent impedance of the loop closing network according to the injected power of the external network.
In one embodiment, the injection power obtaining sub-module performs calculation according to the following formula:
Figure GDA0002843835320000091
wherein EYEQInjecting power for an external network; u shapeBIs the voltage of the boundary node; u shapeAIs the voltage of the loop closing network; u shapeCIs the voltage of the external network; sBIs the power of the border node; sAIs the power of the loop closing network; sCPower for an external network; y isBCIs the mutual admittance between the external network and the boundary node; y isCCSelf-admittance to an external network;
the impedance obtaining submodule is used for calculating according to the following formula:
Figure GDA0002843835320000101
Figure GDA0002843835320000102
wherein Z iseqIs the equivalent impedance of the loop closing network; siIs the power of the border node; y is1、y2、yiIs admittance of a loop closing network branch; u shapeiIs the voltage of the boundary node.
In one embodiment, the current calculation module includes,
the method comprises the following steps:
the steady state current is calculated according to the following formula:
Figure GDA0002843835320000103
wherein, IcIs the steady-state current of the loop closing network; u shapeocTo communicate the voltage difference across the switch; zeqIs the equivalent impedance of the loop closing network;
the transient current is calculated according to the following formula:
Figure GDA0002843835320000104
wherein, IimTransient current of loop closing network; t isaIs a time constant; i isctIs the steady-state current of the loop closing network.
The embodiment of the invention also provides computer equipment which comprises a memory, a processor and a computer program which is stored on the memory and can be run on the processor, wherein the processor executes the computer program to realize the loop closing judgment method of the power distribution network of the factory and the mine.
The embodiment of the invention also provides a computer readable storage medium, and the computer readable storage medium stores a computer program for executing the loop closing judgment method of the factory and mine power distribution network.
In summary, in the loop closing judgment method for the power distribution network of the plant and the mine provided by the embodiment of the present invention, an external network equivalent model of the loop closing network needs to be established to obtain an external network equivalent impedance, and then the transient current and the steady-state current of the loop closing network are obtained according to the voltage difference between two sides of the interconnection switch; and finally, judging whether loop closing operation can be carried out or not according to the steady-state current and the transient-state current of the loop closing network. The loop closing judgment method of the factory and mine power distribution network provided by the embodiment of the invention judges based on the current of the loop closing network, has accurate judgment result and universality, can be suitable for loop closing operation of various factory and mine enterprise power distribution networks, reduces the risk of loop closing operation of the factory and mine enterprises, avoids unnecessary power failure and improves the power supply reliability.
As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention 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 invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows 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-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A loop closing judgment method for a factory and mine power distribution network is characterized by comprising the following steps:
establishing an external network equivalent model of the closed-loop network according to boundary nodes between the closed-loop network and a superior network;
calculating to obtain equivalent impedance of the loop closing network according to the external network equivalent model;
calculating the steady-state current and the transient-state current of the loop closing network according to the voltage difference at the two sides of the interconnection switch and the equivalent impedance of the loop closing network;
when it is determined that the steady-state current and the transient-state current of the loop closing network are smaller than the relay protection current threshold and the equipment rated through-current threshold, judging that the loop closing of the distribution network is possible;
the calculating and obtaining the equivalent impedance of the loop closing network according to the external network equivalent model comprises the following steps:
calculating to obtain the external network injection power according to the external network equivalent model of the closed-loop network;
obtaining equivalent impedance of a loop closing network according to the injected power of an external network;
the external network injection power is obtained by calculation according to the external network equivalent model of the closed-loop network, and the calculation is carried out according to the following formula:
Figure FDA0002843835310000011
wherein EYEQInjecting power for an external network; u shapeBIs the voltage of the boundary node; u shapeAIs the voltage of the loop closing network; u shapeCIs the voltage of the external network; sBIs the power of the border node; sAIs the power of the loop closing network; sCPower for an external network; y isBCIs the mutual admittance between the external network and the boundary node; y isCCSelf-admittance to an external network;
the equivalent impedance of the loop closing network is obtained according to the injected power of the external network, and the equivalent impedance is calculated according to the following formula:
Figure FDA0002843835310000012
Figure FDA0002843835310000013
wherein, yiThe admittance of the ith branch of the loop closing network; i is 1,2, y1For admittance, y, of the 1 st branch of the loop-closing network2Is the admittance of the 2 nd branch of the loop closing network; zeqIs the equivalent impedance of the loop closing network; siIs the power of the border node; u shapeiIs the voltage of the boundary node.
2. The loop closing judgment method for the factory and mine power distribution network according to claim 1, further comprising:
and when the steady-state current and the transient-state current of the closed-loop network are determined to be not less than the relay protection current threshold and the equipment rated through-flow threshold, adjusting the voltage difference at two sides of the interconnection switch, recalculating the steady-state current and the transient-state current of the closed-loop network according to the adjusted voltage difference until the steady-state current and the transient-state current of the closed-loop network are less than the relay protection current threshold and the equipment rated through-flow threshold, and judging that the power distribution network can be closed.
3. The method for loop closing judgment of the power distribution network of the plant and the mine according to claim 1, wherein the step of calculating the steady-state current and the transient-state current of the loop closing network according to the voltage difference between the two sides of the interconnection switch and the equivalent impedance of the external network comprises the following steps:
the steady state current is calculated according to the following formula:
Figure FDA0002843835310000021
wherein, IcIs the steady-state current of the loop closing network; u shapeocTo communicate the voltage difference across the switch; zeqIs the equivalent impedance of the loop closing network;
the transient current is calculated according to the following formula:
Figure FDA0002843835310000022
wherein, IimTransient current of loop closing network; t isaIs a time constant; i isctIs the steady-state current of the loop closing network.
4. A closed loop judgment device of a factory and mine power distribution network is characterized by comprising:
the model establishing module is used for establishing an external network equivalent model of the closed-loop network according to boundary nodes between the closed-loop network and a superior network;
the equivalent impedance obtaining module is used for calculating and obtaining equivalent impedance of the closed loop network according to the external network equivalent model;
the current calculation module is used for calculating the steady-state current and the transient-state current of the loop closing network according to the voltage difference at the two sides of the interconnection switch and the equivalent impedance of the loop closing network;
the loop closing judgment module is used for judging that the distribution network can close the loop when determining that the steady-state current and the transient-state current of the loop closing network are smaller than the relay protection current threshold and the equipment rated through-flow threshold;
the equivalent impedance obtaining module further comprises:
the injection power acquisition submodule is used for calculating and acquiring the injection power of the external network according to the external network equivalent model of the closed-loop network;
the impedance obtaining submodule is used for obtaining equivalent impedance of the loop closing network according to the external network injection power;
the injection power acquisition submodule is calculated according to the following formula:
Figure FDA0002843835310000031
wherein EYEQInjecting power for an external network; u shapeBIs the voltage of the boundary node; u shapeAIs the voltage of the loop closing network; u shapeCIs the voltage of the external network; sBIs the power of the border node; sAIs the power of the loop closing network; sCPower for an external network; y isBCIs the mutual admittance between the external network and the boundary node; y isCCSelf-admittance to an external network;
the impedance obtaining submodule is used for calculating according to the following formula:
Figure FDA0002843835310000032
Figure FDA0002843835310000033
wherein, yiThe admittance of the ith branch of the loop closing network; i is 1,2, y1For admittance, y, of the 1 st branch of the loop-closing network2Is the admittance of the 2 nd branch of the loop closing network; zeqIs the equivalent impedance of the loop closing network; siIs the power of the border node; u shapeiIs the voltage of the boundary node.
5. The loop closing judgment device of the factory and mine power distribution network as claimed in claim 4, wherein the loop closing judgment module is further configured to:
and when the steady-state current and the transient-state current of the closed-loop network are determined to be not less than the relay protection current threshold and the equipment rated through-flow threshold, adjusting the voltage difference at two sides of the interconnection switch, recalculating the steady-state current and the transient-state current of the closed-loop network according to the adjusted voltage difference until the steady-state current and the transient-state current of the closed-loop network are less than the relay protection current threshold and the equipment rated through-flow threshold, and judging that the power distribution network can be closed.
6. The loop closing judgment device of the factory and mine power distribution network as claimed in claim 4, wherein said current calculation module comprises:
the steady state current is calculated according to the following formula:
Figure FDA0002843835310000034
wherein, IcIs the steady-state current of the loop closing network; u shapeocTo communicate the voltage difference across the switch; zeqIs the equivalent impedance of the loop closing network;
the transient current is calculated according to the following formula:
Figure FDA0002843835310000041
wherein, IimTransient current of loop closing network; t isaIs a time constant; i isctIs the steady-state current of the loop closing network.
7. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the method of any one of claims 1 to 3 when executing the computer program.
8. A computer-readable storage medium, characterized in that the computer-readable storage medium stores a computer program for executing the method of any one of claims 1 to 3.
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CN103762594A (en) * 2014-01-28 2014-04-30 国家电网公司 Feeder line loop closing impact current calculation method based on clock synchronization data matrix
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CN103762594A (en) * 2014-01-28 2014-04-30 国家电网公司 Feeder line loop closing impact current calculation method based on clock synchronization data matrix
CN104466945A (en) * 2014-09-22 2015-03-25 珠海许继芝电网自动化有限公司 Method for analyzing loop closing risks based on interconnection switch in power distribution network

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