CN105486981A - Voltage-crossing fault current calculation method for crossing from single-phase to double-phase by mixed-voltage one tower four-parallel lines - Google Patents

Abstract

The invention discloses a voltage-crossing fault current calculation method for crossing from single-phase to double-phase by mixed-voltage one tower four-parallel lines, comprising steps of respectively calculating a positive sequence equivalent impedance and a negative sequence equivalent impedance of two systems having different voltage levels to obtain a positive sequence network and a negative sequence network by a strong current low intensity magnetic system, performing unified decoupling on zero sequence networks of two systems, performing unified reduction to obtain an unified zero sequence network, and performing a faulted current calculation when the voltage-crossing fault happens during the process of crossing from the single-phase to the double phase, dividing the strong current low intensity magnetic system into a low intensity current strong magnetic part and a current source formed by a transformer, and superposing the low intensity current strong magnetic part and the current source to obtain the faulted current when the electrically-connected strong current low intensity magnetic system is faulted in voltage crossing. The invention is applicable to the single-phase crossing to double-phase voltage crossing calculation, can effectively solve the complicated coupling between two systems when the voltage crossing is faulted and the large calculation amount of the super-high-order decoupling method, and can provide a solid theory foundation to the relay protection for the mixed-voltage one tower four parallel line voltage crossing fault.

Description

Mixed pressure with tower four loop line single-phase across two-phase across voltage failure current calculation method

Technical field

The invention belongs to circuit relay protection field, be specifically related to mixed pressure and occur single-phase across fault current computing method during phase to phase fault, for relay protection provides solid theoretical foundation with tower four loop line system.

Background technology

Existing failure analysis methods is aimed at single line down analysis more, analyze with electric pressure double line down and with the fault analysis of electric pressure four loop line, and only is all continue to use the six-sequence component of double loop to mixed pressure with tower four line down analytical approach.In current national line protection, employing method ignores mixed pressure with the mutual inductance between the different electric pressure of tower, and carry out rough equivalence to electrical link, then carries out independent configuration protection to two double loop systems.

When mixed pressure occurs across voltage failure with tower four loop line, due to the mutual inductance between different electric pressure, fault signature is complicated; Consider the electrical link between two electric pressures again, analytical approach is more complicated.Classical failure analysis methods, can be used for single loop line, the various ground connection of single line of double loop and phase-to phase fault, step calculates positive and negative, the zero-sequence network figure of reduction to short dot, calculates the boundary condition of trouble spot, obtain sequence network figure and carry out calculation of fault.To disregard electrical link between two systems the strong magnetic system of light current carry out calculation of fault across voltage failure time, two System Reductions easily obtain respectively to the positive and negative sequence impedance of short dot, but cause zero sequence impedance between two systems but can not independently obtain due to the mutual inductance between two electric pressures again; Boundary condition is also no longer independent simultaneously, but relevant with another one system, and the sequence network figure according to boundary condition also cannot draw.After considering the electrical link of two electric pressures, then not only zero-sequence network figure cannot independently calculate again, and the network chart of positive and negative sequence also cannot independently calculate.Therefore, what adopt in current national line protection is ignore mixed pressure with the mutual inductance between the different electric pressure of tower, and carries out rough equivalence to electrical link, then two double loop systems is carried out to the method for independent configuration protection.

Summary of the invention

For solving the above-mentioned problems in the prior art, the present invention proposes mixed pressure single-phase across fault current computing method during phase to phase fault with tower four loop line.Adopting technical scheme of the present invention, can realize accurately calculating fault current across during voltage failure, providing solid theoretical foundation for analyzing various principle relay protection.

In order to understand technical scheme of the present invention better, first the technical term occurred in the present invention is described as follows:

The same tower of mixed pressure: refer to the transmission line of electricity same transmission tower setting up different electric pressure; What need point out that the present invention studies is the same tower section of two different electric pressure transmission lines of electricity, and power supply tower section different from other does Dai Weinan equivalent process, is equivalent to power supply and outlet impedance manner by power supply and different tower section.

Light current strong magnetic transmission system: the electromagnetic connection between multiple-loop line transmission line of electricity is comparatively strong, electrical link is more weak, and the negligible transmission system of electrical link is called the strong magnetic system of light current compared with electromagnetic connection; Forceful electric power weak magnetic transmission system: there is transformer between different electric pressure and connect, make the electrical link between multiple-loop line transmission line of electricity comparatively strong, the transmission system of can not ignore is called the weak magnetic system of forceful electric power; Mixed pressure of the present invention comprises transmission line of electricity and both sides power-supply system with tower transmission system, between the power-supply system of side, there is transformer to connect, namely there is electrical link between different electric pressure, be " the weak magnetic transmission system of forceful electric power ", otherwise be " the strong magnetic transmission system of light current ".

Across voltage failure: the cross line fault between different electric pressure is called across voltage failure, can be divided into across voltage ground fault with across voltage phase to phase fault across voltage failure.

For reaching above object, the present invention by the following technical solutions:

A kind of mixed pressure with tower four loop line single-phase across two-phase across voltage failure current calculation method, described mixed pressure comprises the double loop transmission system of two different electric pressures with tower four loop line system, when not having transformer to connect between the double loop transmission system of two different electric pressures, described mixed pressure is the strong magnetic transmission system of light current with tower four loop line system, and described computing method comprise the following steps:

Step 1: when mixed pressure with tower four loop line system occur single-phase across two-phase voltage failure time, calculate reduction respectively to the electromotive force size of two different electric pressure transmission systems of fault point and positive and negative sequence impedance; Wherein, two different electric pressure transmission systems adopt I, II system to represent respectively, and the electromotive force size of I, II system is respectively positive sequence impedance is respectively Z _{1 Ψ}, negative sequence impedance is respectively Z _{2 Ψ}, subscript Ψ represents I system, represent II system, all can represent the A/B/C three-phase of two systems, 1,2 represents positive and negative sequence respectively;

Step 2: the zero-sequence network of two different electric pressure transmission systems in step 1 is carried out unifying decoupling zero, common bus between same electric pressure circuit, between I, II system line circuit altogether, double loop then deducts mutual inductance respectively on zero sequence impedance, obtains four loop line zero-sequence networks after unified decoupling zero by the method for parallel double loop;

Step 3: the zero-sequence network of the transmission system by two different electric pressures after the unified decoupling zero of step 2 is carried out unifying reduction, with the short dot of ground, two systems these 3 for node, other nodes of cancellation obtain the equivalent zero-sequence network of unified I, II system, represent with Y shape formula; Wherein I system short-circuit point Nodes zero sequence impedance is Z _{0 Ψ}, II system short-circuit point Nodes zero sequence impedance is ground node place zero sequence impedance is Z _0M, 0 in subscript represents zero sequence;

Step 4: calculate single-phase across the boundary condition of two-phase across voltage ground fault and phase to phase fault, wherein, I system generation single-phase fault, boundary condition is

$\left\{\begin{array}{c}{{\stackrel{\·}{I}}^{\′}}_{1.\mathrm{\Ψ}}={{\stackrel{\·}{I}}^{\′}}_{2.\mathrm{\Ψ}}={{\stackrel{\·}{I}}^{\′}}_{0.\mathrm{\Ψ}}\\ {{\stackrel{\·}{U}}^{\′}}_{1.\mathrm{\Ψ}}={{\stackrel{\·}{U}}^{\′}}_{2.\mathrm{\Ψ}}+{{\stackrel{\·}{U}}^{\′}}_{0.\mathrm{\Ψ}}={\stackrel{\·}{U}}_k\end{array}\right.;$

II system generation phase to phase fault, boundary condition is

In above two formulas, represent short dot voltage-to-ground, when wherein there is earth fault represent that I system failure electric current under the strong magnetic system of light current is positive and negative, zero-sequence component respectively; then represent the above-mentioned component of II system, represent that I system failure voltage under the strong magnetic system of light current is positive and negative, zero-sequence component respectively; then represent that II system failure voltage under the strong magnetic system of light current is positive and negative, zero-sequence component, lower target implication is identical with implication in step 1,3; By the electromotive force of I, II system, positive and negative sequence network, and be combined into unified compound sequence network according to the zero-sequence network after step 3 reduction;

Step 5: calculate according to the following formula on the compound sequence network chart basis that step 4 obtains the mixed pressure of light current strong magnetic with tower four loop line single-phase across two-phase across voltage failure electric current,

Fault current during earth fault is:

During phase to phase fault, fault current is

Wherein in formula be expressed as that I system failure electric current under the strong magnetic system of light current is positive and negative, zero-sequence component; then represent the above-mentioned component of II system.

The present invention also comprises following preferred version further:

When described mixed pressure is connected by transformer with the double loop transmission line of electricity of two different electric pressures in tower four loop line system, institute's mixed pressure belongs to the weak magnetic transmission system of forceful electric power with tower four loop transmission system, mixed pressure with tower four loop line single-phase across two-phase across in voltage failure Current calculation, needing the mixed pressure under weak for forceful electric power magnetic system with tower four loop line system divides is disregard the light current strong magnetic transmission system part of transformer, with the current source portion that transformer is formed, the superposition of two-part fault current component can be obtained single-phase under the weak magnetic system of forceful electric power across two-phase across voltage failure electric current.

Therefore, single-phase further comprising the steps of across voltage failure current calculation method across two-phase under the weak magnetic system of forceful electric power under the weak magnetic system of this forceful electric power:

Step 6: it is single-phase across the fault current under phase to phase fault that the current source that calculating transformer is formed is formed, according to the single-phase fault current across surveying transformer portion under phase to phase fault type, the current source that transformer is formed is decomposed into current source that is positive and negative, zero sequence; During the current source independent role formed according to transformer, mixed pressure, zero-sequence network positive and negative with tower transmission line of electricity, calculates the fault current component that I, II system failure point place is provided as current source by transformer wherein represent when only having transformer as current source respectively, I system failure electric current be positive and negative, positive and negative, the zero-sequence component of zero-sequence component and II system;

Step 7: two parts fault current that step 5,6 is calculated respectively superposition calculation can to obtain the mixed pressure of forceful electric power weak magnetic single-phase across phase to phase fault current sequence components with tower four loop line wherein, synthesize under being respectively the weak magnetic system of the forceful electric power taking into account transformer mixed pressure with the single-phase fault current positive sequence across I, II system during phase to phase fault, negative phase-sequence, the zero sequence value fault current of tower four loop line forceful electric power weak magnetic transmission system.

The invention has the beneficial effects as follows: phase-selecting method of the present invention can accurately calculate mixed pressure with tower single-phase across two-phase across fault current during voltage failure, give fault characteristic during this kind of fault, for the analysis of various principle relay protection provides theoretical foundation.Further, failure analysis methods of the present invention calculates simple, calculates, eliminate the complicated calculations of the decoupling method of other various high-orders by positive and negative, zero-sequence component.

Accompanying drawing explanation

Fig. 1 be have the mixed pressure of electrical connection with tower four loop line across voltage failure model;

Fig. 2 is the fault model of electromotive force of source independent role;

Fig. 3 is the fault model of transformer source independent role;

Fig. 4 is light current strong magnetic system parallel double loop zero-sequence network equivalent circuit schematic diagram;

Fig. 5 is that the strong magnetic system of light current is with tower four loop line zero sequence equivalent circuit diagram;

Fig. 6 is that the strong magnetic system of light current is with tower four loop line zero sequence equivalent circuit reduction model schematic;

Fig. 7 is the single-phase compound sequence network figure across double earthfault C-bc-g fault of the strong magnetic system of light current;

Fig. 8 is the single-phase compound sequence network figure across two-phase phase to phase fault C-bc fault of the strong magnetic system of light current.

Embodiment

Technical scheme of the present invention is further illustrated by embodiment below in conjunction with accompanying drawing.

The invention discloses a kind of mixed pressure with tower four loop line single-phase across two-phase across voltage failure current calculation method, described mixed pressure comprises the double loop transmission system of two different electric pressures with tower four loop line system, when not having transformer to connect between the double loop transmission system of described two different electric pressures, mixed pressure belongs to the strong magnetic transmission system of light current wherein with tower four loop line system.Mixed pressure under the strong magnetic system of light current comprises the following steps across calculating across voltage failure current failure of two-phase with tower four loop line is single-phase:

Step 1: calculate reduction to the electromotive force size of two different electric pressure transmission systems of fault point and positive and negative sequence impedance.For the bc phase of the C phase of I system across II system, wherein the special emf phase size of I, II system is respectively positive sequence impedance is respectively Z _{1 Ψ}, negative sequence impedance is respectively Z _{2 Ψ}, subscript Ψ represents I system, represent II system, capital C represents the C phase of I system, and lowercase a represents a phase of II system, and 1,2 represents positive and negative sequence respectively.

Step 2: use decoupling method to be carried out unifying decoupling zero by the zero-sequence network of two transmission systems.Common bus between same electric pressure circuit, then decoupling zero is identical as shown in Figure 4 with general parallel double loop decoupling zero, bus place connects mutual inductance, double loop then deducts mutual inductance respectively on zero sequence impedance, each node voltage electric current after decoupling zero is identical, is all the decoupling zeros between identical electric pressure in the dotted line frame in accompanying drawing 5.Between different electric pressure circuit altogether, the method for decoupling method parallel double loop can obtain four loop lines after decoupling zero equally, as shown in the solid box in accompanying drawing 5.

Step 3: the zero-sequence network of two different transmission systems is carried out unifying reduction, as shown in Figure 5.With the short dot of ground, two systems etc. 3 for node, use Y/ △ conversion respectively, other nodes of equivalent method cancellation such as connection in series-parallel obtain the equivalent zero-sequence network of system one or two system, as shown in Figure 6.Represent with Y shape formula.Wherein I system short-circuit point Nodes zero sequence impedance is Z _{0 Ψ}, II system short-circuit point Nodes zero sequence impedance is point node place zero sequence impedance is Z _0M, 0 in subscript represents zero sequence.

Step 4: single-phase across the boundary condition of two-phase across voltage ground fault and phase to phase fault, I system generation single-phase fault is (according to step 1, it is the bc phase across II system, the boundary condition of II system should use bc phase to represent, and the present invention adopts the order components of fault electric parameters to carry out expressing and calculating, fault electric parameters can be decomposed into the order components of any phase, the most applicable special phase decomposed in three-phase in calculating, under bc fault, a phase is special phase), boundary condition is $\left\{\begin{array}{c}{{\stackrel{\·}{I}}^{\′}}_{1.C}={{\stackrel{\·}{I}}^{\′}}_{2.C}={{\stackrel{\·}{I}}^{\′}}_{0.C}\\ {{\stackrel{\·}{U}}^{\′}}_{1.C}={{\stackrel{\·}{U}}^{\′}}_{2.C}+{{\stackrel{\·}{U}}^{\′}}_{0.C}={\stackrel{\·}{U}}_k\end{array}\right.;$ II system generation phase to phase fault, boundary condition is $\left\{\begin{array}{c}{{\stackrel{\·}{I}}^{\′}}_{1.a}+{{\stackrel{\·}{I}}^{\′}}_{2.a}+{{\stackrel{\·}{I}}^{\′}}_{0.a}=0\\ {{\stackrel{\·}{U}}^{\′}}_{1.a}={{\stackrel{\·}{U}}^{\′}}_{2.a}={{\stackrel{\·}{U}}^{\′}}_{0.a}-{\stackrel{\·}{U}}_k\end{array}\right.,$ represent that I system C phase fault electric current under the strong magnetic system of light current is positive and negative, zero-sequence component respectively; ${{\stackrel{\·}{I}}^{\′}}_{1.a},{{\stackrel{\·}{I}}^{\′}}_{2.a},{{\stackrel{\·}{I}}^{\′}}_{0.a}$ Then represent that II system failure electric current under the strong magnetic system of light current is positive and negative, zero-sequence component, represent that I system C phase fault voltage under the strong magnetic system of light current is positive and negative, zero-sequence component respectively; then represent that II system a phase fault voltage under the strong magnetic system of light current is positive and negative, zero-sequence component, subscript is identical with implication in step 1,3. represent short dot voltage-to-ground, when wherein there is earth fault according to above-mentioned, the electromotive force of two different transmission systems after unified reduction and positive and negative, zero sequence impedance group of networks are synthesized unified compound sequence network, respectively as shown in FIG. 7 and 8, Fig. 7 represents earth fault, and Fig. 8 represents phase to phase fault.

Step 5: carry out on two compound sequence network chart bases that the mixed pressure of light current strong magnetic is single-phase with tower four loop line across fault current during double earthfault is respectively during phase to phase fault, fault current is

Wherein in formula represent that I system failure electric current is positive and negative, zero-sequence component respectively; then represent the above-mentioned component of II system.

Above step be the mixed pressure of described light current strong magnetic with tower four loop line single-phase across two-phase across voltage failure current calculation method.There is the weak magnetic mixed pressure of the forceful electric power of electrical connection with tower four loop line system, such as, when transmission line of electricity one end of different electric pressure is connected by transformer, across voltage failure model as shown in Figure 1; Method of superposition is used to the weak magnetic system of forceful electric power occurred across voltage failure, will the power supply of fault current be provided for trouble spot to be divided into the power unit of the strong magnetic system of the light current disregarding electrical connection, and the current source portion that transformer is formed, as Figure 1-3.Can solve according to above thinking the fault current that two parts power supply provides respectively, then the superposition of two parts electric current be obtained the result of fault current.The fault current of light current strong magnetic part calculates identical with above-mentioned steps, and electric current overlapping portion step is as follows:

Step 6: single-phase across fault current during phase to phase fault under the effect of calculating transformer section current source, according to the fault current of actual measurement transformer portion, is decomposed into current source that is positive and negative, zero sequence; Draw positive and negative, the zero-sequence network topological diagram of Fig. 3 network respectively, the fault current that this section current source easily obtaining two fault point respectively according to electric network theory in this topological structure provides respectively positive and negative, the zero-sequence component of positive and negative, the zero-sequence component of I system failure electric current and II system under the effect of indication transformer section current source.

Step 7: two parts fault current step 5,6 calculated superposes respectively, other parts can obtain by that analogy namely the single-phase fault current across I, II system during phase to phase fault of the weak magnetic system of the forceful electric power taking into account electrical connection is obtained.

The above; be only the present invention's preferably embodiment, but protection scope of the present invention is not limited thereto, any people being familiar with this technology is in the technical scope disclosed by the present invention; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection domain of claim.

Claims (3)

1. a mixed pressure with tower four loop line single-phase across two-phase across voltage failure current calculation method, described mixed pressure comprises the double loop transmission system of two different electric pressures with tower four loop line system, when not having transformer to connect between the double loop transmission system of two different electric pressures, described mixed pressure is the strong magnetic transmission system of light current with tower four loop line system, and described computing method comprise the following steps:

Step 1: when mixed pressure with tower four loop line system occur single-phase across two-phase voltage failure time, calculate reduction respectively to the electromotive force size of two different electric pressure transmission systems of fault point and positive and negative sequence impedance; Wherein, two different electric pressure transmission systems adopt I, II system to represent respectively, and the electromotive force size of I, II system is respectively positive sequence impedance is respectively Z _{1 Ψ}, negative sequence impedance is respectively Z _{2 Ψ}, subscript Ψ represents I system, represent II system, all can represent the A/B/C three-phase of two systems, 1,2 represents positive and negative sequence respectively;

Step 2: the zero-sequence network of two different electric pressure transmission systems in step 1 is carried out unifying decoupling zero, common bus between same electric pressure circuit, between I, II system line circuit altogether, double loop then deducts mutual inductance respectively on zero sequence impedance, obtains four loop line zero-sequence networks after unified decoupling zero by the method for parallel double loop;

Step 3: the zero-sequence network of the transmission system by two different electric pressures after the unified decoupling zero of step 2 is carried out unifying reduction, with the short dot of ground, two systems these 3 for node, other nodes of cancellation obtain the equivalent zero-sequence network of unified I, II system, represent with Y shape formula; Wherein I system short-circuit point Nodes zero sequence impedance is Z _{0 Ψ}, II system short-circuit point Nodes zero sequence impedance is ground node place zero sequence impedance is Z _0M, 0 in subscript represents zero sequence.

Step 4: calculate single-phase across the boundary condition of two-phase across voltage ground fault and phase to phase fault, wherein, I system generation single-phase fault, boundary condition is

$\left\{\begin{array}{c}{{\stackrel{\·}{I}}^{\′}}_{1.\mathrm{\Ψ}}={{\stackrel{\·}{I}}^{\′}}_{2.\mathrm{\Ψ}}={{\stackrel{\·}{I}}^{\′}}_{0.\mathrm{\Ψ}}\\ {{\stackrel{\·}{U}}^{\′}}_{1.\mathrm{\Ψ}}+{{\stackrel{\·}{U}}^{\′}}_{2.\mathrm{\Ψ}}+{{\stackrel{\·}{U}}^{\′}}_{0.\mathrm{\Ψ}}={\stackrel{\·}{U}}_k\end{array}\right.;$

II system generation phase to phase fault, boundary condition is

In above two formulas, represent short dot voltage-to-ground, when wherein there is earth fault represent that I system failure electric current under the strong magnetic system of light current is positive and negative, zero-sequence component respectively; then represent that II system failure electric current under the strong magnetic system of light current is positive and negative, zero-sequence component, represent that I system failure voltage under the strong magnetic system of light current is positive and negative, zero-sequence component respectively; then represent that II system failure voltage under the strong magnetic system of light current is positive and negative, zero-sequence component, lower target implication is identical with implication in step 1,3; By the electromotive force of I, II system, positive and negative sequence network, and be combined into unified compound sequence network according to the zero-sequence network after the unified reduction of step 3;

Step 5: calculate according to the following formula on the compound sequence network chart basis that step 4 obtains the mixed pressure of light current strong magnetic with tower four loop line single-phase across two-phase across voltage failure electric current,

Fault current during earth fault is:

During phase to phase fault, fault current is

Wherein in formula be expressed as that I system failure electric current under the strong magnetic system of light current is positive and negative, zero-sequence component; the fault current then representing II system is positive and negative, zero-sequence component.

2. mixed pressure according to claim 1 with tower four loop line single-phase across two-phase across voltage failure current calculation method, it is characterized in that:

When described mixed pressure is connected by transformer with the double loop transmission line of electricity of two different electric pressures in tower four loop line system, institute's mixed pressure belongs to the weak magnetic transmission system of forceful electric power with tower four loop transmission system, mixed pressure with tower four loop line single-phase across two-phase across in voltage failure Current calculation, needing the mixed pressure under weak for forceful electric power magnetic system with tower four loop line system divides is disregard the light current strong magnetic transmission system part of transformer, with the current source portion that transformer is formed, the superposition of two-part fault current component can be obtained single-phase under the weak magnetic system of forceful electric power across two-phase across voltage failure electric current.

3. mixed pressure according to claim 1 with tower four loop line single-phase across two-phase across voltage failure current calculation method, it is characterized in that:

When described mixed pressure is connected by transformer with the double loop transmission line of electricity of two different electric pressures in tower four loop line system, institute's mixed pressure belongs to the weak magnetic transmission system of forceful electric power with tower four loop transmission system, mixed pressure with tower four loop line single-phase across two-phase across in voltage failure Current calculation, needing the mixed pressure under weak for forceful electric power magnetic system with tower four loop line system divides is disregard the light current strong magnetic transmission system part of transformer, with the current source portion that transformer is formed, single-phase also further comprising the steps except the step in claim 1 across voltage failure current calculation method across two-phase under the weak magnetic system of forceful electric power: step 6: it is single-phase across the fault current under phase to phase fault that the current source that calculating transformer is formed is formed, according to the single-phase fault current across surveying transformer portion under phase to phase fault type, the current source that transformer is formed just is decomposed into, negative, the current source of zero sequence, during the current source independent role formed according to transformer, mixed pressure, zero-sequence network positive and negative with tower transmission line of electricity, calculates the fault current component that I, II system failure point place is provided as current source by transformer wherein represent when only having transformer as current source respectively, I system failure electric current be positive and negative, positive and negative, the zero-sequence component of zero-sequence component and II system,

Step 7: two parts fault current that step 5,6 is calculated respectively superposition calculation can to obtain the mixed pressure of forceful electric power weak magnetic single-phase across phase to phase fault current sequence components with tower four loop line wherein, synthesize under being respectively the weak magnetic system of the forceful electric power taking into account transformer mixed pressure with the single-phase fault current positive sequence across I, II system during phase to phase fault, negative phase-sequence, the zero sequence value fault current of tower four loop line forceful electric power weak magnetic transmission system.