CN1627588A - Fault discrimination method based on virtual current phase comparison for protecting bus bar system - Google Patents

Abstract

The disclosed method includes following steps: according to fixed sampling interval, each branch is sampled. Sampled data are stored in relevant storage area. Processed result is as reference for determining positive or negative branch current. Virtual current and restraint coefficient K of virtual current are calculated. Based on result of calculating restraint coefficient of virtual current, running state of bus is determined. If the calculated result is larger than Kz, then it is indicated that bus system is in fault state; otherwise, the bus is in normal running state or fault occurs out of this region. The method eliminates high-frequency components effectively. The invention raises speed of protection action, suitable to calculate rapid catastrophe variables under ensuring sensitivity and interference killing feature of protection. The method is suitable to each bus system under 750 kV.

Description

A kind of bus-bar system protection is based on the fault distinguishing method of virtual current than phase

Technical field

The present invention relates to the technical field of relay protection of power system, relate in particular to the method for bus-bar system protection.

Background technology

Implementing " transferring electricity from the west to the east " is great strategy of China's electric power development, and Tenth Five-Year Plan Period, country accelerates emphasis to implement the power supply and the transmission line construction of " transferring electricity from the west to the east " southern line.At present, the development of China's electrical network forms two main trend: the first forms transferring electricity from the west to the east and NORTEL south send isometric distance, jumbo electric power to carry general layout.It two is to realize the intensive development of big regional power grid and interconnected.From the limiting short-circuit current level, the circuit corridor, transmission capacity, aspects such as network security are considered, can not meet the demands under the existing 500kV highest voltage level, China is just attempting utilizing the ultrahigh voltage alternating current transmission lines transmission of electricity of 750kV in the northwest.Extreme high voltage ac transmission is the most economical rational solution of big capacity power delivery He Da district networking, and the successful experience of this respect is abroad also arranged.

And long distance power delivery and the interconnected transformer station that needs to build large quantities of high pressure and superhigh pressure voltage grade of big regional power grid; this has proposed a new problem for the development of bus protection, and how bus protection adapts to the requirement of transient performance, quick acting, high reliability and the high noise immunity of the big system of 750kV bus.Existing bus protection or differentiate with differential current; differential with the braking of sampled value ratio; differential current is differentiated the size of utilizing differential current and is differentiated busbar fault, and the size of differential current is subjected to the influence of bus-bar system running status bigger, thereby sensitivity is not high.Adopt the method for Direct Sampling value ratio braking to differentiate busbar fault, if having high fdrequency component in the transient state failure process of protection, performance is had bigger influence, for 750kV ultra high voltage bus-bar system, the possibility of malfunction increases greatly.

Summary of the invention

At above-mentioned the deficiencies in the prior art, the objective of the invention is to propose a kind of bus-bar system protection based on the fault distinguishing method of virtual current than phase.Described a kind of bus-bar system protection realizes by the following technical solutions than the fault distinguishing method of phase that based on virtual current described bus-bar system is made up of a plurality of branch roads, and described method comprises step:

According to the actual scale situation of bus-bar system, the electric current in each branch road is sampled according to predetermined sampling number, and deposit the sampled value of each branch road in corresponding memory block;

Sampled value to each branch road is carried out data processing at each sampled point, and result is as the positive and negative distinguishing rule of branch current, declare positive and negative after, put accordingly for each loop and indicate;

After calculating each loop current positive and negative, calculate virtual current and virtual current restraint coefficient K, and according to the result of calculation of virtual current restraint coefficient, judge the running status of bus, if result of calculation is greater than Kz, represent that then bus-bar system is in malfunction, otherwise bus is normal operating condition or external area error.

Described calculating virtual current calculates according to following formula:

|∑I _ΦT+|＝IΦ _TP1+...+IΦ _TPn

|∑I _ΦT-|＝IΦ _TN1+...+IΦ _TNn

Wherein: I Φ _TPnRepresent that n T point current sampling data result is positive current element, I Φ _TNnRepresent that n T point current sampling data result is negative current element, Φ=A, B, C.

Described virtual current restraint coefficient K calculates according to following formula:

$\max [\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|},\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}]\≥\mathrm{Kz}$

∑ I wherein _Φ+Be all positive current branch current sums, ∑ I _Φ-Be all negative current branch current sums, Kz is according to the set virtual current restraint coefficient of bus-bar system, and it is worth generally between 2-10.

Described sampled value data processing comprises that multiple spot rolling integration or single-point sampled value handle.

Described multiple spot rolling integration is 3 rolling integrations, and described data processing step further comprises: for N bar branch road, when sampled point was the T point, the result of this point can be calculated with following formula:

INΦ _T＝(IN _T+IN _T-1+IN _T-2)

According to IN Φ _TN branch current of positive negative indication positive and negative at T point current value, each later sampled point is analogized calculating.

Through suitable data processing; can eliminate the high fdrequency component of sampled point effectively; improve the reliability that protection is moved in the transient state failure process; the differentiation of fault does not rely on the size of fault current itself yet in addition; the running status relation of sensitivity and bus is little, has greatly improved the sensitivity of protection.

Further describe the method for the present invention and the course of work below in conjunction with accompanying drawing, can more clearly understand essence of the present invention and advantage.

Description of drawings

Fig. 1 is the schematic diagram of electrical system bus of the present invention system;

Fig. 2 is the described virtual current bus-bar system of a inventive method schematic diagram;

Virtual current bus-bar system schematic diagram when Fig. 3 is the described bus-bar system fault of the inventive method.

Embodiment

Fig. 1 is the schematic diagram of electrical system bus of the present invention system.As shown in Figure 1, the electric current of any bus of electric power system can be divided into into electric current and go out electric current by polarity, and we are synthesized together advancing electric current, are called positive current; Be synthesized together going out electric current, be called negative current.Synthesizing after the sampled data process fast digital filter filtering of each element can virtually be two electric currents: positive current and negative current.Utilize virtual current proportionate relationship, can distinguish the running status of bus significantly, positive current equals negative current when bus protection operate as normal or external area error, and positive current and negative current balance no longer during internal fault.Virtual current than facies principle owing to adopted fast data to handle and digital filtering; can be under the prerequisite that does not influence the protection responsiveness; improve the sensitivity and the antijamming capability of protection, had natural anti-high-order harmonic ability, satisfied the demand of superhigh pressure bus-bar system.

Its criterion is as follows:

$\max [\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|},\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}]\≥\mathrm{Kz}$

∑ I wherein _Φ+Be all positive current branch current sums, ∑ I _Φ-Be all negative current branch current sums, Kz is not equal to 1 coefficient.

When normal operation or external area error, all branch roads of bus-bar system advance electric current and equal out electric current, thereby all branch currents satisfy $\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|}=1;$ And during troubles inside the sample space the inflow of branch current with flow out no longer equally, the proportionate relationship of reversal takes place to change greatly, therefore

Or Be one much larger than 1 value, utilize this feature can distinguish significantly in and external area error.

Suppose that bus-bar system forms (as Fig. 1) by N branch road; for each branch road; bus protection will be according to predetermined sampling interval (sampling number) sampling; the frequency of sampling and the performance of CPU and the design in loop have relation; formula that we are following and analysis are all so that 24 points/ripple is example (for the electric power system of 50HZ, a cycle is 20MS) weekly.After the protection sampling, the sampled value of each branch road is carried out data processing at each sampled point, puts greater than zero or minus sign, then the numerical value greater than zero is lumped together usefulness according to the result who handles | ∑ I _{Φ T+}| expression lumps together usefulness to minus data | ∑ I _{Φ T-}| the expression, the electric current of protection with regard to virtual be two electric currents, system becomes Fig. 2.Fig. 2 is the described virtual current bus-bar system of a inventive method schematic diagram.The fault distinguishing of bus protection changes the relation of judging two virtual currents into also by the relation of judging N branch road.Utilize the bus-bar system fault distinguishing formula of virtual current to be:

$\max [\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|},\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}]\≥\mathrm{Kz}$ (formula 1)

Wherein:

| ∑ I _{Φ T+}|=I Φ _TP1+ ...+I Φ _TPn(formula 2)

| ∑ I _{Φ T-}|=I Φ _TN1+ ...+I Φ _TNn(formula 3)

I Φ _TPnThe T point sampling Value Data result of n positive current element, I Φ _TNnThe T point sampling Value Data result of n negative current element, K is according to the set virtual current restraint coefficient of bus-bar system.

Virtual current bus-bar system schematic diagram when Fig. 3 is the described bus-bar system fault of the inventive method.When bus-bar system does not break down, according to Kirchhoff's theorem, | ∑ I _{Φ T+}|-| ∑ I _{Φ T-}|=0, just | ∑ I _{Φ T-}|/| ∑ I _{Φ T+}|=1.When the bus-bar system fault, as shown in Figure 3, at this moment, | ∑ I _{Φ T+}|-| ∑ I _{Φ T-}|-IK=0

Promptly | ∑ I _{Φ T+}|=| ∑ I _{Φ T-}|+IK.During owing to break down, can be divided into two kinds of situations and analyze:

1) if | ∑ I _{Φ T+}|＞| ∑ I _{Φ T-}|, IK approximates so | ∑ I _{Φ T+}|, therefore | ∑ I _{Φ T-}| be a very little value, much smaller than | ∑ I _{Φ T+}|.So | ∑ I _{Φ T+}|/| ∑ I _{Φ T-}| be a very big value.

2) if | ∑ I _{Φ T-}|＞| ∑ I _{Φ T+}|, IK approximates so | ∑ I _{Φ T-}|, therefore | ∑ I _{Φ T+}| be a very little value, much smaller than | ∑ I _{Φ T-}|.So | ∑ I _{Φ T-}|/| ∑ I _{Φ T+}| be a very big value.

Therefore | ∑ I _{Φ T-}|/| ∑ I _{Φ T+}| or | ∑ I _{Φ T+}|/| ∑ I _{Φ T-}| feature can be used in bus protection and differentiate fault.

Scale according to bus-bar system is provided with rational sampling circuit, and the sampled value of each branch road of bus-bar system must deposit corresponding memory block in, the sampled value I1 that article one branch road is ordered at T synchronously after the sampling _TExpression, the sampled value I1 of ordering at T-1 _T-1Expression, the sampled value I1 of ordering at T-2 _T-2Expression.The sampled value IN that N bar branch road is ordered at T _TExpression, the sampled value IN of ordering at T-1 _T-1Expression, the sampled value IN of ordering at T-2 _T-2Expression.

Sampling letter for every branch road all will carry out data processing at each sampled point, and several different methods is arranged, and comprises multiple spot rolling integration, single-point sampled value etc.Result of calculation is as the positive and negative distinguishing rule of branch current, declare positive and negative after, put accordingly for each loop and indicate.For N bar branch road, when sampled point is the T point, be example with 3 rolling integrations, the result of this point can be calculated with following formula:

INΦ _T＝(IN _T+IN _T-1+IN _T-2)

According to IN Φ _TN branch current of positive negative indication positive and negative at T point current value, each later sampled point is analogized calculating.

After calculating each loop current positive and negative, formula 2 and formula 3 calculate virtual current, calculate the virtual current restraint coefficient according to formula 1 then, again according to the result of calculation of virtual current restraint coefficient, judge the running status of bus, if result of calculation represents that greater than Kz bus-bar system is in malfunction, otherwise bus is normal operating condition or external area error.

Claims (5)

1, a kind of bus-bar system protection is based on the fault distinguishing method of virtual current than phase, and described bus-bar system is made up of a plurality of branch roads, and described method comprises step:

According to the actual scale situation of bus-bar system, the electric current in each branch road is sampled according to predetermined sampling number, and deposit the sampled value of each branch road in corresponding memory block;

Sampled value to each branch road is carried out data processing at each sampled point, and result is as the positive and negative distinguishing rule of branch current, declare positive and negative after, put accordingly for each loop and indicate;

After calculating each loop current positive and negative, calculate virtual current and virtual current restraint coefficient K, and according to the result of calculation of virtual current restraint coefficient, judge the running status of bus, if result of calculation is greater than according to the set virtual current restraint coefficient Kz of bus-bar system, represent that then bus-bar system is in malfunction, otherwise bus is normal operating condition or external area error.

2, method according to claim 1 is characterized in that described virtual current calculates according to following formula:

|∑I _ΦT+|＝IΦ _TP1+...+IΦ _TPn

|∑I _ΦT-|＝IΦ _TN1+...+IΦ _TNn

Wherein: I Φ _TPnRepresent that n T point current sampling data result is positive current element, I Φ _TNnRepresent that n T point current sampling data result is negative current element, Φ=A, B, C.

3, method according to claim 2 is characterized in that described virtual current restraint coefficient K satisfies following formula:

$\max \[\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|},\frac{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}-}\right|}{\left|\mathrm{\Σ}{I}_{\mathrm{\Φ}+}\right|}\]\≥\mathrm{Kz}$

∑ I wherein _Φ+Be all positive current branch current sums, ∑ I _Φ-Be all negative current branch current sums, Kz is according to the set virtual current restraint coefficient of bus-bar system, and it is worth generally between 2-10.

4, method according to claim 3 is characterized in that described sampled value data processing comprises that multiple spot rolling integration or single-point sampled value handle.

5, method according to claim 4, it is characterized in that described multiple spot rolling integration is 3 rolling integrations, described data processing step further comprises: for N bar branch road, when sampled point was the T point, the result of this point can be calculated with following formula:

INΦ _T＝(IN _T+IN _T-1+IN _T-2)

According to IN _{Φ T}N branch current of positive negative indication positive and negative at T point current value, each later sampled point is analogized calculating.

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