CN105510771A - Hybrid-voltage common-tower four-loop two-phase-cross-three-phase cross voltage fault current calculation method - Google Patents

Abstract

The invention relates to a hybrid-voltage common-tower four-loop two-phase-cross-three-phase cross voltage fault current calculation method. A hybrid-voltage common-tower line is divided into a weak-electric and strong-magnetic system and a strong-electric and weak-magnetic system, in the weak-electric and strong-magnetic system, positive and negative-sequence equivalent impedance of two systems with different voltage levels at a fault point are calculated through reduction; the zero-sequence networks of the two systems are subjected to unified decoupling; the zero-sequence impedance of the two systems is subjected to unified reduction, so that the unified zero-sequence networks of the two systems can be obtained; fault current calculation in a two-phase-cross-three-phase cross voltage fault is carried out on the combined and unified compound-sequence network diagram of the two zero-sequence networks; and in the strong-electric and weak magnetic system, fault current caused by a weak-electric and strong-magnetic part and a power source formed by a transformer are superimposed. With the hybrid-voltage common-tower four-loop two-phase-cross-three-phase cross voltage fault current calculation method of the invention adopted, the problem of large amount of calculation of a decoupling method which has excessively high order and causes complicated coupling between two systems can be solved, and a solid theoretical foundation can be provided for the relay protection of a hybrid-voltage common-tower four-loop cross voltage fault.

Description

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

Technical field

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

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 with tower four loop line two-phase across fault current computing method during three-phase fault.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, power supply and different tower section is equivalent to power supply and outlet impedance manner.

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 two-phase across three-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, described mixed pressure belongs to the strong magnetic transmission system of light current with tower four loop line system; It is characterized in that, the mixed pressure under the strong magnetic transmission system of light current is with tower four loop line two-phase comprising the following steps across voltage failure current calculation method across three-phase:

Step 1: when mixed pressure with tower four loop line system generation two-phase across three-phase voltage fault 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, adopt I, II system to represent respectively two different electric pressure transmission systems, 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}, in the method, 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 two loop line road, between different electric pressure circuit altogether, four loop line zero-sequence networks after unified decoupling zero are obtained by the method for parallel double loop;

Step 3: undertaken unifying reduction by by the transmission system of two different electric pressures after the unified decoupling zero of step 2 and the zero-sequence network of I, II system, with the short dot of ground, two systems these 3 for node, the equivalent zero-sequence network of unified I, II system is obtained after using Y/ △ conversion, other nodes of connection in series-parallel equivalent method cancellation respectively, 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: calculate two-phase across the boundary condition of three-phase across voltage ground fault and phase to phase fault, wherein I system generation phase to phase fault, boundary condition is $\left\{\begin{array}{c}{{\stackrel{\·}{I}}^{\′}}_{1.\mathrm{\ψ}}+{{\stackrel{\·}{I}}^{\′}}_{2.\mathrm{\ψ}}+{{\stackrel{\·}{I}}^{\′}}_{0.\mathrm{\ψ}}=0\\ {{\stackrel{\·}{U}}^{\′}}_{1.\mathrm{\ψ}}={{\stackrel{\·}{U}}^{\′}}_{2.\mathrm{\ψ}}={{\stackrel{\·}{U}}^{\′}}_{0.\mathrm{\ψ}}-{\stackrel{\·}{U}}_k\end{array}\right.;$

II system generation three-phase fault, boundary condition is positive and negative sequence voltage is zero, and residual voltage

In above formula, to represent in light current strong magnetic transmission system that I system failure electric current is positive and negative, zero-sequence component respectively, represent that I system failure voltage under the strong magnetic system of light current is positive and negative, zero-sequence component respectively, represent short dot voltage-to-ground, when wherein there is earth fault according to the electromotive force of I, II system, positive and negative sequence network, and be combined into unified compound sequence network by zero-sequence network after the unified reduction of step 3;

Step 5: carry out the strong magnetic mixed pressure of light current respectively with tower four loop line two-phase across three-phase fault Current calculation on the compound sequence network chart basis that step 4 obtains,

Fault current wherein during earth fault is

Fault current during phase to phase fault is

In formula represent, to represent in light current strong magnetic transmission system that I system failure electric current is positive and negative, zero-sequence component respectively; then represent that II system failure electric current is positive and negative, zero-sequence component.

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, described 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 two-phase across three-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 two-phase under the weak magnetic system of forceful electric power across three-phase across voltage failure electric current.

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, described 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 two-phase across three-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 two-phase under the weak magnetic system of forceful electric power across three-phase across voltage failure electric current, therefore the mixed pressure under the weak magnetic system of forceful electric power with tower four loop line system two-phase across three-phase across voltage failure current calculation method except comprising aforesaid step 1-5, further comprising the steps of:

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

Step 7: two parts fault current step 5,6 calculated superposes respectively, obtains the weak magnetic mixed pressure of forceful electric power with tower four loop line two-phase across three-phase fault current sequence components wherein synthesize be respectively the two-phase of the mixed pressure under the weak magnetic system of the forceful electric power taking into account transformer with tower four loop line system across fault current positive sequence, negative phase-sequence, the zero sequence value of I, II system during three-phase fault.

The invention has the beneficial effects as follows: phase-selecting method of the present invention can accurately calculate mixed pressure with tower two-phase across fault current during three-phase voltage fault, gives 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 compound sequence network figure of the strong magnetic system two-phase of light current across three-phase ground fault AB-abc-g fault;

Fig. 8 is the compound sequence network figure of the strong magnetic system two-phase of light current across three-phase phase to phase fault AB-abc fault.

Embodiment

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

The present invention disclose a kind of mixed pressure with tower four loop line two-phase across three-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 with tower four loop line system.Mixed pressure under the strong magnetic system of light current is with tower four loop line two-phase comprising the following steps across voltage failure current calculation method across three-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 abc phase of the AB phase of I system across II system, wherein the special emf phase size of I system is iI system is for a phase, and electromotive force size is 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 residual voltage after decoupling zero, zero-sequence current are identical, are 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: two-phase is across the boundary condition of three-phase across voltage ground fault and phase to phase fault, and I system generation phase to phase fault, boundary condition is $\left\{\begin{array}{c}{{\stackrel{\·}{I}}^{\′}}_{1.C}+{{\stackrel{\·}{I}}^{\′}}_{2.C}+{{\stackrel{\·}{I}}^{\′}}_{0.C}=0\\ {{\stackrel{\·}{U}}^{\′}}_{1.C}={{\stackrel{\·}{U}}^{\′}}_{2.C}={{\stackrel{\·}{U}}^{\′}}_{0.C}-{\stackrel{\·}{U}}_k\end{array}\right.;$ II system generation three-phase fault, boundary condition is positive and negative sequence voltage is zero, and represent short dot voltage-to-ground, when wherein there is earth fault all the other represent the fault current component of short-circuit point, represent the component of voltage of short-circuit point, lower target implication is identical with implication in step (1).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 the strong magnetic mixed pressure of light current respectively and calculate across fault current during three-phase fault with tower four loop line two-phase on two compound sequence network chart bases, topological structure according to Fig. 7 and Fig. 8 is easily obtained two-phase and is respectively, under earth fault across the fault current under three-phase two kinds of fault types

Under phase to phase fault

In formula represent that the fault current of I system C phase is positive and negative, zero-sequence component respectively; then represent the above-mentioned component of II system a phase; All the other meaning of parameters are identical with implication in step 1,3.

Above step be the strong magnetic mixed pressure of described light current with tower four loop line two-phase across three-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: the two-phase that the current source that calculating transformer is formed is formed, across the fault current under three-phase fault, 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 fault current of two-phase across I, II system during three-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 two-phase across three-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, described mixed pressure belongs to the strong magnetic transmission system of light current with tower four loop line system; It is characterized in that, the mixed pressure under the strong magnetic transmission system of light current is with tower four loop line two-phase comprising the following steps across voltage failure current calculation method across three-phase:

Step 1: when mixed pressure with tower four loop line system generation two-phase across three-phase voltage fault 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, adopt I, II system to represent respectively two different electric pressure transmission systems, the electromotive force size of I, II system is respectively positive sequence impedance is respectively negative sequence impedance is respectively in the method, 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 two loop line road, between different electric pressure circuit altogether, four loop line zero-sequence networks after unified decoupling zero are obtained by the method for parallel double loop;

Step 3: undertaken unifying reduction by by the transmission system of two different electric pressures after the unified decoupling zero of step 2 and the zero-sequence network of I, II system, with the short dot of ground, two systems these 3 for node, the equivalent zero-sequence network of unified I, II system is obtained after using Y/ △ conversion, other nodes of connection in series-parallel equivalent method cancellation respectively, 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: calculate two-phase across the boundary condition of three-phase across voltage ground fault and phase to phase fault, wherein I system generation phase to phase fault, boundary condition is $\left\{\begin{array}{c}{{\stackrel{\·}{I}}^{\′}}_{1.\mathrm{\ψ}}+{{\stackrel{\·}{I}}^{\′}}_{2.\mathrm{\ψ}}+{{\stackrel{\·}{I}}^{\′}}_{0.\mathrm{\ψ}}=0\\ {{\stackrel{\·}{U}}^{\′}}_{1.\mathrm{\ψ}}={{\stackrel{\·}{U}}^{\′}}_{2.\mathrm{\ψ}}={{\stackrel{\·}{U}}^{\′}}_{0.\mathrm{\ψ}}-{\stackrel{\·}{U}}_k\end{array}\right.;$

II system generation three-phase fault, boundary condition is positive and negative sequence voltage is zero, and residual voltage

In above formula, to represent in light current strong magnetic transmission system that I system failure electric current is positive and negative, zero-sequence component respectively, represent that I system failure voltage under the strong magnetic system of light current is positive and negative, zero-sequence component respectively, represent short dot voltage-to-ground, when wherein there is earth fault according to the electromotive force of I, II system, positive and negative sequence network, and be combined into unified compound sequence network by zero-sequence network after the unified reduction of step 3;

Step 5: carry out the strong magnetic mixed pressure of light current respectively with tower four loop line two-phase across three-phase fault Current calculation on the compound sequence network chart basis that step 4 obtains,

Fault current wherein during earth fault is

Fault current during phase to phase fault is

In formula represent, to represent in light current strong magnetic transmission system that I system failure electric current is positive and negative, zero-sequence component respectively; then represent that II system failure electric current is positive and negative, zero-sequence component.

2. mixed pressure according to claim 1 with tower four loop line two-phase across three-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, described 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 two-phase across three-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 two-phase under the weak magnetic system of forceful electric power across three-phase across voltage failure electric current.

3. mixed pressure according to claim 1 with tower four loop line two-phase across three-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, described 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 two-phase across three-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 two-phase under the weak magnetic system of forceful electric power across three-phase across voltage failure electric current, therefore the mixed pressure under the weak magnetic system of forceful electric power with tower four loop line system two-phase across three-phase across voltage failure current calculation method except comprising step 1-5 according to claim 1, further comprising the steps of:

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

Step 7: two parts fault current step 5,6 calculated superposes respectively, obtains the weak magnetic mixed pressure of forceful electric power with tower four loop line two-phase across three-phase fault current sequence components wherein synthesize be respectively the two-phase of the mixed pressure under the weak magnetic system of the forceful electric power taking into account transformer with tower four loop line system across fault current positive sequence, negative phase-sequence, the zero sequence value of I, II system during three-phase fault.