CN106505523A - A kind of excitation flow recognition method suitable for Traction networks transformer - Google Patents

Abstract

The invention discloses a kind of excitation flow recognition method suitable for Traction networks transformer, including：Step 1：Collection tractive transformer winding three-phase electric current, and difference processing is carried out to each phase current；Step 2：Calculate the three-phase current rate of change in power frequency period T；Step 3：T/2 cycle data windows are arbitrarily read, and pointwise sequentially elapses the difference and and value for calculating that three-phase current rate of change is adjacent the three-phase current rate of change absolute value corresponding to the sampling number of half period backward；Step 4：Using N/2 difference accumulated value Δ i '_{diff‑φ‑1}, N/2 and value accumulated value Δ i '_{diff‑φ‑2}, shove and internal fault according to the identification of further criterion.The method that a kind of utilization interval angle of the present invention and asymmetry compound characteristics recognize excitation surge current, reduces the impact of DC component, and the method principle is simple, and amount of calculation is little, and recognition accuracy is higher, is easily applied in engineering practice.

Description

A kind of excitation flow recognition method suitable for Traction networks transformer

【Technical field】

The invention belongs to tractive power supply system tractive transformer technical field of relay protection, and in particular to a kind of being applied to is led Draw the excitation flow recognition method of net transformer.

【Background technology】

Used as most important part in tractive power supply system, its reliable, safe operation is supplied tractive transformer to whole traction The safe operation important in inhibiting of electric system.Excitation surge current is the principal element for causing transformer main protection differential protection malfunction One of.How transformer excitation flow and internal fault is rapidly and accurately recognized, contribute to lifting Traction networks tranformer protection work The reliability of work.

In recent years, Chinese scholars propose a lot of methods to transformer identification excitation surge current problem, according to utilizing electric parameters Can be divided into：1) current characteristic method；2) voltage characteristic method；3) Current Voltage compound characteristics method.

1st, the excitation flow recognition method of current characteristic：Mainly include the method for quadratic harmonics, interruption horn cupping, waveform symmetry method Deng.The characteristics of there is the method for quadratic harmonics principle to be simply easily achieved, but affected by transient current characteristic and transformer magnetization characteristic Larger, and secondary harmonic brake threshold adjusts difficulty.Interruption horn cupping mainly produces the excitation surge current time difference according to tractive transformer Streaming current has significantly interruption corner characteristics, and difference current is then without significantly interruption corner characteristics during failure.Waveform symmetry for The foundation for choosing neither one determination of threshold value, is simply chosen by engineering experience.

2nd, the excitation flow recognition method of voltage characteristic：Mainly include that magnetic flux method, difference have works, transformer equivalent circuit method Deng.Magnetic flux method can preferably reflect the transient process of transformer, but stronger to the characteristic and parameter dependence of transformer itself. Difference has the voltage and current information that works take full advantage of transformer to be identified the state of transformer, but threshold value is adjusted More difficult.Although transformer equivalent circuit do not need transformer magnetization curve, the winding parameter of transformer is had compared with High requirement.

3rd, the excitation flow recognition method of voltage x current compound characteristics：Mainly include magnetic flux characteristic, power differential principle etc.. As transformer remanent magnetism obtains difficult, the ψ-i obtained in the case of excitation surge current_dCurve will deviate from magnetization curve, so as to cause magnetic The erroneous judgement of logical Characterization method, while the complexity that has that subregion is difficult and restraint coefficient threshold value is adjusted.Power differential method needs to avoid gushing The charging process in the 1st cycle of transformer during stream, causes to differentiate time delay；Copper loss accurate dyscalculia during excitation surge current, therefore utilize When the principle identification is shoved, threshold value is adjusted more difficult.

Additionally, also there is scholar to carry out excitation surge current identification with reference to intellectual technologies such as fuzzy logic, wavelet transformation, neutral nets Method, but intelligent algorithm recognizes to shove there is larger uncertainty and realize that algorithm is complicated, computationally intensive, has been difficult in a short time Effect is used for Practical Project.

【Content of the invention】

For the deficiency of existing trailer system transformer excitation flow identification, it is an object of the invention to provide one kind is applied to The excitation flow recognition method of Traction networks transformer, solves asking for transformer differential protection misoperation present in prior art Topic.

The present invention seeks to be achieved through the following technical solutions：

A kind of excitation flow recognition method suitable for Traction networks transformer, comprises the following steps：

Step 1：Collection transformer A, B, C three-phase current i_φ(k), wherein, φ=A, B, C, and poor to each phase current Manage office；

Step 2：Calculate the three-phase current rate of change i ' in a power frequency period T_diff-φ(k)；

Step 3：T/2 cycle data windows are arbitrarily read, and pointwise is sequentially elapsed backward and calculates three-phase current rate of change i '_diff-φ(k) And the three-phase current rate of change corresponding to the sampling number of adjacent integers times half periodRate of change is calculated respectively Absolute value differencesAnd rate of change absolute value and value Wherein k be sampling number, the sampling number that N is a power frequency calculating cycle, n=1,2 ...；

Step 4：The three-phase electricity rheology calculated by the sampling number that half period is adjacent according to three-phase current rate of change The difference accumulated value Δ i ' of rate_diff-φ-1With with value accumulated value Δ i '_diff-φ-2, shove according to the identification of following inrush current distinguishing criterion And internal fault,

Wherein, K_resFor braking threshold；N is integer value；In a cycle, as long as A, B, C three-phase current has one mutually to meet Above-mentioned inrush current distinguishing criterion, then be judged to shove, transformer differential protection locking；Internal fault is otherwise judged to.

Step 1 is specially：Three-phase current i to transformer_A(k)、i_B(k)、i_CK () is acquired, calculate each phase differential electrical Stream i_diff-A(k)=i_A(k)-i_A(k-1)、i_diff-B(k)=i_B(k)-i_B(k-1)、i_diff-C(k)=i_C(k)-i_C(k-1), wherein, K=2,3,4 ....

Step 2 is specially：Calculate each phase difference current i_diff-A(k)、i_diff-B(k)、i_diff-CK () is calculated in a power frequency Current changing rate i ' in cycle T_diff-φ(k)：

Current changing rate：

Wherein, k is sampling number, T_sFor the sampling period.

Step 3 is specially：Step 2 is adjacent half week in the three-phase current rate of change that certain sampled point calculates gained Three-phase current rate of change absolute value corresponding to the sampling number of phase is poor, obtains Δ i ' by cumulative for N/2 calculated value_diff-φ-1, I.e.：

Then the three-phase current rate of change corresponding to this sampled point is adjacent corresponding to the sampling number of half period Three-phase current rate of change absolute value summation, by N/2 calculated value add up obtain Δ i '_diff-φ-2, i.e.,

K_resValue is that 0.2, n takes 1～3.

Relative to prior art, the present invention has advantages below：

A kind of utilization interval angle of the present invention and the excitation flow recognition method of asymmetry compound characteristics, take full advantage of and lead Wave character when drawing transformer excitation flow, is exaggerated the excitation surge current under weak current operating mode with inside using differential calculation process The interval angle of fault current and pinnacle waveform feature difference, are expected to the inrush current distinguishing for improving trailer system transformer differential protection Energy.The excitation flow recognition method of the present invention, in view of the interval angle shoved when transformer excitation flow and internal fault and pinnacle Wave characteristic difference, realizes shoving and internal fault is accurately identified.Fault current waveform internally during failure, after differential process In significant periodic sinusoidal wave characteristic in any half power frequency calculating cycle, at least exist a curent change extreme point and Electric current has symmetric characteristics；When transformer during no-load closing produces excitation surge current, due to the interval angle that shoves and pinnacle wave characteristic, Electric current after differential only there is curent change extreme point in peaked wave region and electric current does not have symmetric characteristics.Therefore, profit The reliability differentiation that can be realized shoving with internal fault with this curent change feature, reduces the impact of DC component, and The method principle is simple, and amount of calculation is little, and recognition accuracy is higher, is easily applied in engineering practice.With other excitation surge current identifications Principle is compared, and the present invention has following remarkable advantage：

(1) using the interval angle and the compound characteristics on pinnacle of transformer excitation flow electric current, improve special using the magnitude of current Levy the applicability of identification excitation surge current；

(2) whether the electric current after being gone out using differential still has whether interval angle and curent change extreme point have symmetry, Excitation surge current can rapidly and accurately be recognized.

【Description of the drawings】

Fig. 1 is the flow process of the excitation flow recognition method of a kind of utilization interval angle of the invention and asymmetry compound characteristics Figure.

【Specific embodiment】

Below in conjunction with the accompanying drawings, the specific embodiment of the present invention is described in detail, but the invention is not restricted to the enforcement Example.In order that the public has to the present invention thoroughly understanding, detailed description concrete details in example is preferably applied in present invention below.

The present invention principle be：Work as transformer equivalent to the fault branch of power transformer interior fault in static exciter loop During core sataration, very big excitation surge current can be produced and flowed in differential relay, cause differential protection misoperation.Due to excitation Electric current is very big, if escape which with action current affecting, differential protection sensitivity in power transformer interior fault will reduce.Mirror In this, the present invention is recognized excitation surge current using excitation surge current and then prevents excitation from gushing with internal fault current wave character difference Stream causes the misoperation of differential protection.During due to internally failure, through differential process after fault current in any half power frequency In calculating cycle, at least there is a curent change extreme point and electric current has symmetric characteristics；During transformer during no-load closing, warp Electric current after differential process is with interruption corner characteristics, and only there is curent change extreme point and electric current in peaked wave region not There are symmetric characteristics.Therefore, the reliability differentiation that shoves with internal fault can be realized using this curent change feature.

The method that a kind of utilization interval angle of the present invention and asymmetry compound characteristics recognize excitation surge current, specific flow process is such as Shown in Fig. 1, implement according to following steps：

Step 1：Collection Three-Phase Transformer electric current i_φK (), wherein, φ=A, B, C represent Three-Phase Transformer circuit respectively Wherein a phase, i.e. i_A(k)、i_B(k)、i_CK (), calculates each phase difference current i_diff-A(k)=i_A(k)-i_A(k-1)、i_diff-B(k)- i_B(k)-i_B(k-1)、i_diff-C(k)=i_C(k)-i_C(k-1), wherein, k=2,3,4 ...；

As Transformer Winding is in inductive, excitation surge current contains part aperiodic component with internal fault current, sharp With difference processing reducing the impact of aperiodic component.

Step 2：Calculate the three-phase current rate of change i ' in power frequency period T_diff-φ(k), specially：

Calculate each phase difference current i_diff-A(k)、i_diff-B(k)、i_diff-CThe electric current of (k) in power frequency calculating cycle T Rate of change i '_diff-φK () is

Current changing rate：

Wherein, k is sampling number, T_sFor the sampling period；

Step 3：Shoved and internal fault using criterion identification：

The sampling number that step 2 is adjacent half period in the three-phase current rate of change that certain sampled point calculates gained Corresponding three-phase current rate of change absolute value is poor, obtains Δ i ' by cumulative for N/2 calculated value_diff-φ-1I.e.

Then the three-phase current rate of change corresponding to this sampled point is adjacent corresponding to the sampling number of half period Three-phase current rate of change absolute value summation, by N/2 calculated value add up obtain Δ i '_diff-φ-2I.e.

Step 4 is specially：

Three-phase current rate of change according to step 3 is adjacent the three-phase electricity rheology calculated by the sampling number of half period The difference accumulated value Δ i ' of rate_diff-φ-1With with value accumulated value Δ i '_diff-φ-2, shove according to the identification of following inrush current distinguishing criterion And internal fault：

Wherein, K_resFor braking threshold, it is considered to the measure error and calculation error of current transformer, K_resValue is 0.2；n Round numbers, according to the reliability value for differentiating, can use 1～3.

In a cycle, due to excitation surge current through differential process after electric current only exist in peaked wave region electric current change Change extreme point and electric current and there are no symmetric characteristics, and internal fault through differential process after fault current at least there is an electricity Rheology extreme point and extreme point possesses symmetry feature.As long as therefore three-phase current has one mutually to meet above-mentioned inrush current distinguishing and sentences According to, then it is judged to shove, transformer differential protection locking；Internal fault is otherwise judged to.

The inventive method is using tractive transformer excitation surge current and internal fault current feature difference, it is proposed that a kind of utilization The excitation surge current of interval angle and asymmetry feature and internal fault recognition methods.The method produces excitation using tractive transformer When shoving, difference current has significantly interruption corner characteristics and curent change extreme point that not there is symmetry feature, and differential during failure Significantly interruption corner characteristics and at least there is an extreme point and extreme point and possess symmetric feature and distinguish in electric current Excitation surge current and fault current angle characteristic, the method principle are simple, and amount of calculation is little, with engineering application value.

More than, only presently preferred embodiments of the present invention is not limited only to the practical range of the present invention, all according to patent of the present invention Equivalence changes and modification that the content of scope is done, all should be the technology category of the present invention.

Claims (5)

1. a kind of excitation flow recognition method suitable for Traction networks transformer, it is characterised in that comprise the following steps：

Step 1：Collection transformer A, B, C three-phase current i_φ(k), wherein, φ=A, B, C, and each phase current is carried out at difference Reason；

Step 2：Calculate the three-phase current rate of change i ' in a power frequency period T_diff-φ(k)；

Step 3：T/2 cycle data windows are arbitrarily read, and pointwise is sequentially elapsed backward and calculates three-phase current rate of change i '_diff-φ(k) and phase Three-phase current rate of change corresponding to the sampling number of adjacent integral multiple half periodIt is exhausted that rate of change is calculated respectively To value difference valueAnd rate of change absolute value and value Wherein k is sampling number, the sampling number that N is a power frequency calculating cycle, and n is positive integer；

Step 4：The three-phase current rate of change calculated by the sampling number that half period is adjacent according to three-phase current rate of change Difference accumulated value Δ i '_diff-φ-1With with value accumulated value Δ i '_diff-φ-2, according to following inrush current distinguishing criterion identification shove with interior Portion's failure,

$\frac{{\mathrm{\Δi}}_{diff-\mathrm{\φ}-1}^{\′}}{{\mathrm{\Δi}}_{diff-\mathrm{\φ}-2}^{\′}}>K_{res};$

Wherein, K_resFor braking threshold；N is integer value；In a cycle, if A, B, C three-phase current have one mutually meet above-mentioned Inrush current distinguishing criterion, then be judged to shove, transformer differential protection locking；Internal fault is otherwise judged to.

2. a kind of excitation flow recognition method suitable for Traction networks transformer according to claim 1, it is characterised in that Step 1 is specially：Three-phase current i to transformer_A(k)、i_B(k)、i_CK () is acquired, calculate each phase difference current i_diff-A (k)=i_A(k)-i_A(k-1)、i_diff-B(k)=i_B(k)-i_B(k-1)、i_diff-C(k)=i_C(k)-i_C(k-1), wherein, k=2,3, 4….

3. a kind of excitation flow recognition method suitable for Traction networks transformer according to claim 1, it is characterised in that Step 2 is specially：Calculate each phase difference current i_diff-A(k)、i_diff-B(k)、i_diff-CK () is in power frequency calculating cycle T Current changing rate i '_diff-φ(k)：

Current changing rate：

Wherein, k is sampling number, T_sFor the sampling period.

4. a kind of excitation flow recognition method suitable for Traction networks transformer according to claim 1, it is characterised in that Step 3 is specially：The sampling that step 2 is adjacent half period in the three-phase current rate of change that certain sampled point calculates gained The corresponding three-phase current rate of change absolute value of points is poor, obtains Δ i ' by cumulative for N/2 calculated value_diff-φ-1, i.e.,：

${\mathrm{\Δi}}_{diff-\mathrm{\φ}-1}^{\′}=\underset{k=k_0}{\overset{k_0+\frac{N}{2}-1}{\mathrm{\Σ}}}\left|\right|i_{diff-\mathrm{\φ}}^{\′}\left(k\right)|-|i_{diff-\mathrm{\φ}}^{\′}(k-n\·\frac{N}{2})\left|\right|;$

Then the three three-phase current rate of change corresponding to this sampled point is adjacent corresponding to the sampling number of half period Phase current rate of change absolute value is sued for peace, and obtains Δ i ' by cumulative for N/2 calculated value_diff-φ-2, i.e.,

${\mathrm{\Δi}}_{diff-\mathrm{\φ}-2}^{\′}=\underset{k=k_0}{\overset{k_0+\frac{N}{2}-1}{\mathrm{\Σ}}}\left|\right|i_{diff-\mathrm{\φ}}^{\′}\left(k\right)|+|i_{diff-\mathrm{\φ}}^{\′}(k-n\·\frac{N}{2})\left|\right|.$

5. a kind of excitation flow recognition method suitable for Traction networks transformer according to claim 1, it is characterised in that K_resValue is that 0.2, n takes 1～3.