CN101593972B - Fault line selection method for resonant grounded power distribution system by pattern spectrum - Google Patents

Abstract

The invention provides a fault line selection method for a resonant grounded power distribution system by pattern spectrum. When the resonant grounded power distribution system has a single phase fault, the zero sequence current of each line can be increased suddenly; and at the instant of the fault, the direction of the zero sequence current of a fault line is opposite to that of a perfect line; therefore, the zero sequence current of each line is subjected to multi-scale morphological operation firstly, and then the pattern spectrum of the zero sequence current is derived; after the fault line has a fault, the pattern spectrum of the first-half wave zero sequence current is mainly distributed in the positive scale, while after the perfect line has a fault, the pattern spectrum of the first-half wave zero sequence current is mainly distributed in the negative scale; therefore, positive scale spectral values and negative scale spectral values of the pattern spectrum of the zero sequence current of each line are respectively summed, and then a ratio of the sum of the positive scale spectral values to the sum of the negative scale spectral values of the zero sequence current of each line is respectively calculated; and a line with the maximum ratio is the fault line, otherwise, the bus fault is judged. The method has strong antijamming capacity, is not influenced by fault close angle and transition resistance, has low requirement on sampling frequency of signals, and has the advantages of convenient realization and low cost.

Description

Utilize the resonance grounding electric network fault selection method of form spectrum

Technical field

The present invention relates to the relay protection of power system technical field, specifically utilize the resonance grounding electric network fault selection method of form spectrum.

Background technology

During resonance grounding electrical network generation single phase ground fault, line voltage still symmetry and fault current is less, can continue to move 1～2h, helps improving the reliability of power supply.But be that non-fault phase-to-ground voltage raises, long-play causes fault to expand as or multiple spot short circuit easily at 2; Arc grounding also can cause the total system overvoltage, and therefore the insulation of harm equipment and the safe operation of system must in time determine faulty line, fix a breakdown as early as possible.Yet resonance grounding electrical network grounding phenomenon is very complicated, and when single phase ground fault took place, because the compensating action of arc suppression coil, faulty line was approaching in amplitude with the fault current that perfects circuit, and the paraphase phenomenon often occurs.

For addressing this problem, many scholars have carried out a large amount of research, have proposed the selection method based on steady-state quantity, based on the selection method and the signal injection method of transient state amount.Be subject to the influence of transition resistance and unstable arc based on the selection method of steady-state quantity, sensitivity is low, judges by accident easily.The method that the utilization of signal injection method is injected external signal to system is carried out route selection, but has following significant disadvantages: 1. when high resistance ground, inject weak output signal and difficult the detection; 2. arc grounding time-harmonic wave content is abundant, injects pickup electrode and is vulnerable to disturb; 3. the electric pressure of Shi Yonging lower (normally 10kV), operation and maintenance workload are bigger, during resonance grounding electrical network generation single-phase earthing, fault phase capacitor discharge, the charging of non-fault phase electric capacity, the generation amplitude transient current bigger several times to tens times than steady-state value.Highly sensitive and influenced by arc suppression coil little based on the selection method of transient state amount, but the route selection effect mostly can not be satisfactory, the protectiveness degree that mainly shows as route selection is little, and accuracy and reliability are lower.

Summary of the invention

The object of the present invention is to provide a kind of form spectrum of utilizing to the method that resonance grounding electric network fault circuit carries out route selection,, fix a breakdown as early as possible, ensure the safety of power consumption equipment and electric power system in time to determine faulty line.

The principle of institute of the present invention foundation is:

1, form spectrum principle

The form spectrum is the important method that shape is represented in the graphical analysis, is the quantitative description of shape, is derived by form value distribution curve.Suppose that pending signal f (n) is the one-dimensional signal that sampling obtains, its domain of definition is D _f, wherein, n is a sampled point, n=0, and 1,2 ..., N; N is the sequence length of f (n).G (k) is the one-dimentional structure element sequence, and its domain of definition is D _g, k is a sampled point, k=0, and 1,2 ..., P; Wherein, P is the sequence length of g (k), and P and N are integers, N 〉=P.F (n) is designated as f in following formula, g (k) all is designated as g in following formula.Then f (n) ash value expands (n) be defined as respectively with ash value corrosion (f Θ g):

(f Θ g) (n)=min{f (n+x)-g (x) | (n+x) ∈ D _fAnd x ∈ D _g(2)

In formula (1) and the formula (2),

The expression dilation operation, Θ represents erosion operation, max represent the set f (n-x)+g (x) | (n-x) ∈ D _fAnd x ∈ D _gIn greatest member, min represent the set f (n+x)-g (x) | (n+x) ∈ D _fAnd x ∈ D _gIn least member, x is the translation variable.It is irreversible operation that corrosion of ash value and ash value expand, and corroding earlier afterwards expands is called ash value opening operation, and first expansion post-etching is called the closed operation of ash value.Sequence f (n) is defined as respectively about opening operation f ο g and the closed operation fg of g (k):

$f\·g=f\⊕\mathrm{g\Θg}---\left(4\right)$

The domain of definition of supposing structural element g (k) is about former point symmetry, and its radius length is r.The size that changes r can construct the shape likeness in form, but the structural element that varies in size is used g _r(k) expression.Adopt the structural element g of different sizes _r(k) signal f (n) is carried out morphology operations and be called the multi-scale morphology operations.According to formula (3) and formula (4), sequence f (n) is about g _r(k) opening operation and closed operation is designated as (f ο g) respectively _r, (fg) _rThen the form of f (n) spectrum is defined as:

r≥0(5)

${\mathrm{PS}}_f(-r,g)=\frac{\mathrm{dA}{(f\·g)}_r}{\mathrm{dr}},$ r＞0(6)

In the formula, PS _f(+r, g) the form spectrum of definition f (n) under positive scale, PS _f(r g) is defined as the form spectrum of f (n) under negative scale, A (f ο g) _rWhen expression structural element radius length was r, sequence f (n) was about g _r(k) each element sum among the opening operation result, promptly A (fg) _rWhen expression structural element g (k) radius length was r, sequence f (n) was about g _r(k) each element sum among the closed operation result, $A{(f\·g)}_r=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{(f\·g)}_r\left(n\right).$ The essence of form spectrum is to have described the variation of signal under different scales.

The present invention utilizes the principle of above-mentioned form spectrum just, and resonance grounding electrical network that single phase ground fault takes place is carried out failure line selection.That is: when resonance grounding electrical network generation single phase ground fault, each circuit zero-sequence current can increase suddenly, and moment takes place in fault, faulty line is opposite with the zero-sequence current direction that perfects circuit, can take out the zero sequence current signal of each bar circuit in view of the above, by formula (3), formula (4) zero-sequence current of each bar circuit is carried out opening operation, closed operation under the multi-scale, right back-pushed-type (5), formula (6) differentiate obtain each corresponding form spectrum, and the form spectrum of each circuit zero-sequence current can be good at reacting faulty line and the zero-sequence current that perfects circuit this feature that changes in the opposite direction.Because after the faulty line fault, the form of first half-wave zero-sequence current spectrum mainly is distributed in positive scale, and after perfecting line fault, the form spectrum of first half-wave zero-sequence current mainly is distributed in negative scale, wherein, after each line fault that obtains, the form of first half-wave zero-sequence current is composed as shown in Figure 3.To the positive scale spectrum value of each circuit zero-sequence current form spectrum and bear scale spectrum value and sue for peace respectively, ask for the ratio of each circuit zero-sequence current positive scale spectrum value sum and negative scale spectrum value sum then respectively in view of the above, select three ratios of maximum, be made as ρ successively _k, ρ _m, ρ _n, if satisfy ρ _k＞ρ _m+ ρ _n, the circuit of the ratio maximum of promptly positive and negative scale spectrum value sum then is judged as faulty line, otherwise is judged as busbar fault.

The present invention finishes by following technical proposal: a kind of resonance grounding electric network fault selection method that utilizes the form spectrum is characterized in that comprising the following steps:

(1) as bus residual voltage instantaneous value u _n(t) greater than K _uU _n, fault line selection device starts, and notes before the fault zero-sequence current of 10 each circuits of ms behind the 2ms and fault, wherein, and K _uValue is 0.15, U _nExpression bus rated voltage;

(2) according to following formula the sample sequence of the first half-wave of each line fault zero-sequence current is carried out the expansion of ash value (n) calculate with ash value corrosion (f Θ g);

(f Θ g) (n)=min{f (n+x)-g (x) | (n+x) ∈ D _fAnd x ∈ D _g}

In the formula, f is the one-dimensional signal sequence that sampling obtains, and its domain of definition is D _f, wherein, n is a sampled point, n=0, and 1,2 ..., N; N is the sequence length of f; G is the one-dimentional structure element sequence, and its domain of definition is D _g, The expression dilation operation, Θ represents erosion operation, max represent the set f (n-x)+g (x) | (n-x) ∈ D _fAnd x ∈ D _gIn greatest member, min represent the set f (n+x)-g (x) | (n+x) ∈ D _fAnd x ∈ D _gIn least member, x is the translation variable,

For f is worth the expansion result calculated about the g ash, (f Θ g) is that f is about g ash value corrosion result calculated (n);

(3) on the basis of step (2), the sample sequence of each line fault zero-sequence current is carried out opening operation and closed operation is calculated according to following formula;

$f\·g=f\⊕\mathrm{g\Θg}$

In the formula, f ο g be f about g opening operation result, fg be f about g closed operation result,

Ash value corrosion calculating is carried out in expression earlier, and the result who obtains carries out the expansion of ash value again and calculates,

Ash value expansion calculating is carried out in expression earlier, and the result who obtains carries out the corrosion of ash value again and calculates;

(4) calculate the form spectrum of the sample sequence of the first half-wave of each line fault zero-sequence current according to following formula;

r≥0

${\mathrm{PS}}_f(-r,g)=\frac{\mathrm{dA}{(f\·g)}_r}{\mathrm{dr}},$ r＞0

In the formula, r is the element radius length, PS _f(+r, g) form that is defined as under the positive scale of f (n) is composed PS _f(r, g) form that is defined as under the negative scale of f (n) is composed A (f ο g) _rThe expression structure, sequence f (n) is about g _r(k) each element sum among the opening operation result,

A (fg) _rWhen expression structural element g (k) radius length was r, sequence f (n) was about g _r(k) each element sum among the closed operation result, $A{(f\·g)}_r=\underset{n=1}{\overset{N}{\mathrm{\Σ}}}{(f\·g)}_r\left(n\right);$

(5) to the positive scale spectrum value of each circuit zero-sequence current form spectrum with bear scale spectrum value and sue for peace respectively, ask for the ratio of each circuit zero-sequence current positive scale spectrum value sum and negative scale spectrum value sum then respectively, select three ratios of maximum, be made as ρ successively _k, ρ _m, ρ _n, if satisfy ρ _k＞ρ _m+ ρ _n, the circuit of the ratio maximum of promptly positive and negative scale spectrum value sum then is judged as faulty line, otherwise is judged as busbar fault.

The present invention compared with prior art has following advantage:

1, adopts the multi-scale morphology operations to extract fault zero-sequence current wave character, have stronger antijamming capability, and be not subjected to the influence of fault switching angle, transition resistance size.

2, the present invention is based on the time domain waveform feature identification of fault zero-sequence current, therefore lower to the signals sampling frequency requirement, have be convenient to realize, advantage that cost is low.

3, mathematical morphology computational process is simple, is mainly plus and minus calculation, do not relate to multiplication and division and calculate, so computational speed is very fast.

Description of drawings

Fig. 1 is the schematic diagram of resonance grounding electric network single-phase earth fault network.

Fig. 2 is the fault zero-sequence current oscillogram of each circuit, among the figure, (a) is faulty line L ₁Fault zero-sequence current oscillogram; (b) for perfecting circuit L ₂Fault zero-sequence current oscillogram; (c) for perfecting circuit L ₃Fault zero-sequence current oscillogram; (d) for perfecting circuit L ₄Fault zero-sequence current oscillogram; (e) for perfecting circuit L ₅Fault zero-sequence current oscillogram; (f) for perfecting circuit L ₆Fault zero-sequence current oscillogram.I among the figure ₀₁, i ₀₂, i ₀₃, i ₀₄, i ₀₅, i ₀₆Represent circuit L respectively ₁, L ₂, L ₃, L ₄, L ₅, L ₆Corresponding zero-sequence current, A represents ampere, t/ms express time/millisecond.

Fig. 3 is each circuit zero-sequence current form spectrum schematic diagram.

Fig. 4 is circuit L ₁The multi-scale opening operation result schematic diagram of fault zero-sequence current.I among the figure ₀₁Expression circuit L ₁Zero-sequence current, A represents ampere, t/ms express time/millisecond.

Each circuit zero-sequence current form spectrum schematic diagram when Fig. 5 fault switching angle is 90 °.

Embodiment

Adopt resonance grounding electric network single-phase earth fault network as shown in Figure 1, its circuit L ₁Apart from first section 2km place single phase ground fault takes place, the fault switching angle is 90 °, and sample frequency is 10kHz.Figure 1 shows that a schematic diagram that the 110kV/35kV resonance grounding electrical network phase earth fault network of 6 circuits is arranged, Z font transformer neutral point adopts LSJC-35 type current transformer by arc suppression coil series resistance ground connection.Circuit adopts overhead transmission line (L ₁, L ₃, L ₅), line-cable joint line (L ₄) and cable line (L ₂, L ₆), wherein, overhead transmission line adopts JS ₁The bar type, LGJ-70 type lead, span are 80m, cable line adopts YJV23-35/95 type cable.Among Fig. 1, T is a step-down transformer, and Tz is a Z font transformer, and K is a switch, and L is the arc suppression coil inductance, and R is the arc suppression coil series resistance, R _fBe earth fault transition resistance, i ₀₁, i ₀₄, i ₀₆Be respectively circuit L ₁, L ₄, L ₆Zero-sequence current.

Resonance grounding electric network single-phase earth fault network shown in Figure 1, the arc suppression coil compensation degree is 10%, circuit L ₁Apart from bus 5km place single phase ground fault takes place, the fault switching angle is 30 °, and when transition resistance was 20 Ω, the zero-sequence current after each bar line fault as shown in Figure 2.

Concrete steps are as follows:

(1) because bus residual voltage instantaneous value u _n(t) when t=252ms, u _n(t)=5.3kV is greater than K _uU _n=5.25kV, wherein, K _uValue is 0.15, U _nBe the bus rated voltage, its value is for 35kV, and fault line selection device starts immediately, notes before the fault zero-sequence current of each circuit of 10ms behind the 2ms and fault, and sample frequency is 10kHz, and then the zero-sequence current of every circuit has 150 sampled points, circuit L ₁The waveform that constitutes of 120 sampled points of zero-sequence current shown in Fig. 4 solid line;

(2) according to following formula each line fault zero-sequence current sample sequence is carried out 5 open and close computings under the scale, each line fault zero-sequence current sample sequence is calculated as the sequence f in the following formula, obtain circuit L ₁The formed waveform of opening operation result under each scale of zero-sequence current as shown in phantom in Figure 4, promptly dotted line is opening operation result under its each scale among Fig. 4, is the direction that the form scale increases from top to bottom, promptly the structural element radius increases successively;

$f\·g=f\⊕\mathrm{g\Θg}$

(3) calculate the form spectrum of each line fault zero-sequence current sample sequence according to following formula, its result of calculation as shown in Figure 5,

r≥0

${\mathrm{PS}}_f(-r,g)=\frac{\mathrm{dA}{(f\·g)}_r}{\mathrm{dr}},$ r＞0

(4) the positive and negative scale form of each line fault zero-sequence current spectrum value is sued for peace respectively after, ask for the ratio of each circuit zero-sequence current positive scale spectrum value sum and negative scale spectrum value sum then respectively, then circuit L ₁～L ₆The ratio of positive and negative scale spectrum value sum is followed successively by: 2.04,0.36,0.48,0.47,0.66,0.51.

(5) according to route selection criterion ρ _k＞ρ _m+ ρ _n, selecting faulty line is L ₁

Theory analysis and simulation results show that the present invention is effective.

Claims (1)

1. a resonance grounding electric network fault selection method that utilizes the form spectrum is characterized in that comprising the following steps:

(1) as bus residual voltage instantaneous value u _n(t) greater than K _uU _n, fault line selection device starts, and notes before the fault zero-sequence current of 10 each circuits of ms behind the 2ms and fault, wherein, and K _uValue is 0.15, U _nExpression bus rated voltage;

(2) according to following formula the sample sequence of the first half-wave of each line fault zero-sequence current is carried out the expansion of ash value

(n) calculate with ash value corrosion (f Θ g);

In the formula, f is the one-dimensional signal sequence that sampling obtains, and its domain of definition is D _f, wherein, n is a sampled point, n=0, and 1,2 ..., N; N is the sequence length of f; G is the one-dimentional structure element sequence, and its domain of definition is D _g,

The expression dilation operation, Θ represents erosion operation, max represent the set f (n-x)+g (x) | (n-x) ∈ D _fAnd x ∈ D _gIn greatest member, min represent the set f (n+x)-g (x) | (n+x) ∈ D _fAnd x ∈ D _gIn least member, x is the translation variable,

For f is worth the expansion result calculated about the g ash, (f Θ g) is that f is about g ash value corrosion result calculated (n);

(3) on the basis of step (2), the sample sequence of each line fault zero-sequence current is carried out opening operation and closed operation is calculated according to following formula;

In the formula, f ο g be f about g opening operation result, fg be f about g closed operation result,

Ash value corrosion calculating is carried out in expression earlier, and the result who obtains carries out the expansion of ash value again and calculates,

Ash value expansion calculating is carried out in expression earlier, and the result who obtains carries out the corrosion of ash value again and calculates;

(4) calculate the form spectrum of the sample sequence of the first half-wave of each line fault zero-sequence current according to following formula;

In the formula, r is the element radius length, PS _f(+r, g) form that is defined as under the positive scale of f (n) is composed PS _f(r, g) form that is defined as under the negative scale of f (n) is composed A (f ο g) _rWhen expression structural element radius length was r, sequence f (n) was about g _r(k) each element sum among the opening operation result,

A (fg) _rWhen expression structural element g (k) radius length was r, sequence f (n) was about g _r(k) each element sum among the closed operation result,

(5) to the positive scale spectrum value of each circuit zero-sequence current form spectrum with bear scale spectrum value and sue for peace respectively, ask for the ratio of each circuit zero-sequence current positive scale spectrum value sum and negative scale spectrum value sum then respectively, select three ratios of maximum, be made as ρ successively _k, ρ _m, ρ _n, if satisfy ρ _k＞ρ _m+ ρ _n, judge that then positive and negative scale spectrum value is a faulty line than maximum circuit, otherwise be judged as busbar fault.

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