CN103323728A - Method for identifying single-phase earth fault and visional grounding based on whole cyclic wave energy ratio - Google Patents
Method for identifying single-phase earth fault and visional grounding based on whole cyclic wave energy ratio Download PDFInfo
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Abstract
The invention relates to a method for identifying a single-phase earth fault and visional grounding based on a whole cyclic wave energy ratio and belongs to the technical field of electric power system relay protection. Zero sequence voltage data of two cyclic waves are extracted after the fault, wavelet transformation is respectively conducted on the zero sequence voltage data, and summation is conducted on the square number of each wavelet reconstruction coefficient in each dimension after transformation, so that the highest frequency energy value is obtained. The highest frequency energy value of a first cyclic wave is compared with the highest frequency energy value of a second cyclic wave, so that identification of the single-phase earth fault and visional grounding of a power distribution network is reliably achieved according to the value relationship of the highest frequency energy values and a set threshold value. The method for identifying the single-phase earth fault and visional grounding based on the whole cyclic wave energy ratio has the advantages of being simple in principle, capable of identifying visional grounding in short time, good in robustness, free of influence by an arc fault, non-linear load and the like, capable of greatly reducing the requirements for a hardware sampling rate and high in practicality.
Description
Technical field
The present invention relates to a kind of singlephase earth fault based on the whole wave energy Ratios and illusory ground recognition method, belong to the Relay Protection Technology in Power System field.
Background technology
Under the normal operation, usually the neutral by arc extinction coil grounding power distribution network is in the over-compensation state, the feeder line that puts into operation when bus increases or the factor such as system operation mode change when causing capacity current to increase, automatic tuning apparatus can be regulated the arc suppression coil input from the variation of motion tracking capacitance current, at this moment system may enter into full compensating coefficient, thereby generation resonance overvoltage, resonance overvoltage may approach even the neutral point displacement voltage when surpassing singlephase earth fault, and this phenomenon is referred to as illusory ground connection.When the rising of neutral point voltage owing to singlephase earth fault causes, should regulate arc suppression coil and make and take off humorous degree and reduce, regulate to full compensation direction; If illusory grounding phenomenon then should be regulated arc suppression coil and make it take off humorous degree increase, regulate to the direction that over-compensation increases, to eliminate series resonance, system is recovered normally.
Relatively neutral point displacement voltage when single-phase earthing and illusory ground connection can see that the two is as broad as long on stable state numerical value, and the size that is difficult to the steady-state value by neutral point displacement voltage is distinguished these two kinds of methods of operation.Show by practical operating experiences, existing two kinds of methods are effective to identifying illusory ground connection.A kind of is after the neutral point voltage rising occurring, to regulate the arc suppression coil gear change, distinguishes the two by the variation of monitoring the neutral point voltage that causes thus.Another kind method is to distinguish singlephase earth fault and illusory ground connection by the rate of rise of monitoring residual voltage.But above-mentioned two kinds of windows that method takes are all longer, are unfavorable in time finding singlephase earth fault.
Summary of the invention
The technical problem to be solved in the present invention be overcome existing identification singlephase earth fault and window that illusory earthing method takes longer, be unfavorable in time finding the weak point of singlephase earth fault.
Technical scheme of the present invention is: a kind of singlephase earth fault and illusory ground recognition method based on the whole wave energy Ratios, extract the residual voltage data of latter two cycle of fault, respectively it is carried out wavelet transformation, square summation with the wavelet reconstruction coefficient under each yardstick after the conversion, get its energy value, with the high-frequency energy value of first cycle high-frequency energy value than second cycle, obtain
Value is according to itself and setting threshold
Magnitude relationship reliably realize the identification of one-phase earthing failure in electric distribution network and illusory ground connection.
One-phase earthing failure in electric distribution network and illusory ground recognition method specifically carry out according to following step:
(1) behind the power distribution network generation singlephase earth fault, starting element starts immediately, and the three-phase voltage that records according to the protection installation place can get the fault residual voltage
:
In the formula:
,
,
Be respectively faulty line A, B, C three-phase voltage;
k=1,2,3
N,
NBe sample sequence length;
(2) the residual voltage data of latter two cycle of extraction one-phase earthing failure in electric distribution network utilize wavelet transformation technique that it is decomposed, and extract each frequency band energy, establish discrete signal
x(
n), the wavelet coefficient under each decomposition scale carried out single reconstruct after, the frequency band range of the component of signal institute inclusion information that obtains is suc as formula shown in (B):
In the formula,
D j (
n) be the wavelet reconstruction coefficient of signal high fdrequency component;
A j (
n) be the wavelet reconstruction coefficient of signal low frequency component;
f s Sample frequency for signal;
j=1,2,3 ... J, J are maximum decomposition scale, original signal sequence
x(
n) can be expressed as each component and, namely
x(
n)=
(C)
Order
D m+ 1
(
n)=
A m (
n), then have
x(
n)=
(D)
In the formula, m is wavelet transform dimension;
(3) for orthogonal wavelet transformation, after the conversion energy of each yardstick can be directly by square the obtaining of the wavelet reconstruction coefficient after its single reconstruct, namely
Here choose the db4 small echo two cycles of selected residual voltage signal are carried out respectively 6 layers of wavelet decomposition, namely herein
Obtain the energy value of each layer frequency band according to formula (E);
(4) establishing the high-frequency energy value that first cycle obtains after the fault behind wavelet transformation is
E 11, the high-frequency energy value of second cycle is
E 12, remember the two ratio
ρFor:
(F)
(5) after illusory ground connection occurs power distribution network, obtain the residual voltage data of two cycle, utilize step in the said method (1) to step (4) to try to achieve respectively the high-frequency energy value of two cycles, and get its ratio
(6) according to ratio
With set threshold value
Between relationship distinguish singlephase earth fault and illusory ground connection:
When
ρ〉=
ρ SetThe time, be judged to be singlephase earth fault;
When
ρ＜
ρ SetThe time, be judged to be illusory ground connection.
Principle of work of the present invention is:
Along with feeder line in the distribution be on the increase, system line capacitance current over the ground also increases day by day, so that the power distribution network of neutral by arc extinction coil grounding enters into full compensating coefficient possibly, thereby cause resonance overvoltage, its value may approach even the neutral point displacement voltage when surpassing singlephase earth fault, produces illusory grounding phenomenon.Because illusory ground connection is the industrial frequency resonance superpotential, do not contain in theory the HF voltage composition, and the neutral excursion voltage that singlephase earth fault causes contains abundant HF voltage composition.
Therefore the present invention finishes identification to singlephase earth fault and illusory ground connection by analyzing the high-frequency energy feature that comprises in the feeder line residual voltage information.By extracting the residual voltage data of latter two cycle of fault, respectively it is carried out wavelet transformation, square summation with the wavelet reconstruction coefficient under each yardstick after the conversion gets its energy value, chooses the high-frequency energy value E of first cycle
11High-frequency energy value E than second cycle
12 
, obtain
After the value, according to itself and set threshold value
Between the reliable identification that realizes singlephase earth fault and illusory ground connection of relation:
When
ρ〉=ρ
SetThe time, be judged to be singlephase earth fault;
When
ρ＜ρ
SetThe time, be judged to be illusory ground connection.
The invention has the beneficial effects as follows:
1, this method principle is comparatively simple, and is ageing good, can realize the identification of illusory ground connection within the time of two cycles.
2, this method is utilized energy approach, and its robustness is good, not affected by electric arc fault, nonlinear-load etc.
3, lower to the requirement of hardware sampling rate, stronger practicality is arranged.
Description of drawings
Fig. 1 is the distribution network system structural drawing that is used for emulation among the embodiment: figure,
L 1,
L 3,
L 5Overhead feeder,
L 4Xian – cable mixing feeder line,
L 2,
L 6Cable feeder line, G are infinitely great power supply, and T is main-transformer, T
ZBe the zigzag transformer, L is arc suppression coil, and R is the damping resistance of arc suppression coil;
Fig. 2 is the fault angle of embodiment 1 feeder line when being 5 °
L 1The residual voltage oscillogram;
Fig. 3 is the fault angle of embodiment 2 feeder line when being 90 °
L 1The residual voltage oscillogram;
Fig. 4 is feeder line during illusory ground connection among the embodiment
L 1The residual voltage oscillogram.
Embodiment
Embodiment 1: as shown in Figure 1: 110kV/35kV one-phase earthing failure in electric distribution network realistic model, supply voltage is 110kV among the figure, be delivered to load side after transformer becomes 35kV, it has 6 feeder lines, and the Z-shaped transformer neutral point is by arc suppression coil resistance in series ground connection.Overhead feeder
L 1=15km,
L 3=18km,
L 5=30km ， Xian – cable mixing feeder line
L 4=17km, its overhead feeder 12km, cable 5km, cable feeder line
L 2=6km,
L 6=8km.Wherein, overhead feeder is JS1 bar type, and LGJ-70 type wire, span 80m, cable feeder line are YJV23-35/95 type cable.G in this electrical network is infinitely great power supply; T is main-transformer, and no-load voltage ratio is 110 kV/35kV, and connection set is Y
N/ d11; T
ZIt is the zigzag transformer; L is arc suppression coil; R is the damping resistance of arc suppression coil.Feeder line adopts overhead transmission line, overhead line-cable hybrid line and three kinds of circuits of cable line.Load is selected the firm power load model.Apart from feeder line
L 1Singlephase earth fault occurs in 5 km places, top, stake resistance 20 Ω, and the fault angle is 5 °, sample frequency is 10kHz.
(1) after power distribution network broke down, starting element started immediately, feeder line
L 1The residual voltage waveform as shown in Figure 2, after the time window data of choosing latter two cycle of fault were carried out wavelet transformation respectively, square summation with the wavelet reconstruction coefficient under each yardstick after the conversion got its energy value;
(2) try to achieve the high-frequency energy value of first cycle
E 11=35339, second high-frequency energy value of cycle
E 12=5079.6, threshold value
The reliability of set basis recognition methods get 1.5,
=35339/5079.6=6.957＞
ρ Set=1.5, so can judge feeder line
L 1Be fault feeder.
Embodiment 2:110kV/35kV one-phase earthing failure in electric distribution network realistic model is identical with embodiment 1, apart from feeder line
L 1Singlephase earth fault occurs in 5 km places, top, stake resistance 20 Ω, and the fault angle is 90 °, sample frequency is 10kHz.
Press the identical method of embodiment 1, feeder line
L 1The residual voltage waveform and is tried to achieve the high-frequency energy value ratio of first cycle and second cycle as shown in Figure 3
=13198＞
ρ Set=1.5, so can judge feeder line
L 1Be the singlephase earth fault feeder line.
Embodiment 3:110kV/35kV distribution network system realistic model after magnitude of voltage is out-of-limit, obtains two cycle residual voltage data with embodiment 1.
Should be based on the step of the singlephase earth fault of whole wave energy Ratios and illusory ground recognition method with embodiment 1.
The residual voltage waveform that obtains by emulation experiment and is tried to achieve the high-frequency energy value ratio of first cycle and second cycle as shown in Figure 4
=1.2943
=1.5, so can illusory grounding phenomenon occur the judgement system.
In addition, under different faults angle and the illusory Grounding after the fault first cycle and the high-frequency energy of second cycle than as shown in table 1.This ratio in the singlephase earth fault situation much larger than 1, and during illusory ground connection near 1, by as seen from Table 1, this method can be effectively, reliable recognition singlephase earth fault and illusory ground connection.
The above has done detailed description to the specific embodiment of the present invention by reference to the accompanying drawings, but the present invention is not limited to above-mentioned embodiment, in the ken that those of ordinary skills possess, can also under the prerequisite that does not break away from aim of the present invention, make a variety of changes.
Claims (2)
1. singlephase earth fault and illusory ground recognition method based on a whole wave energy Ratios, it is characterized in that: the residual voltage data of extracting latter two cycle of fault, respectively it is carried out wavelet transformation, square summation with the wavelet reconstruction coefficient under each yardstick after the conversion, get its energy value, with the high-frequency energy value of first cycle high-frequency energy value than second cycle, obtain
Value is according to itself and setting threshold
Magnitude relationship reliably realize the identification of one-phase earthing failure in electric distribution network and illusory ground connection.
2. singlephase earth fault and illusory ground recognition method based on the whole wave energy Ratios according to claim 1, it is characterized in that: one-phase earthing failure in electric distribution network and illusory ground recognition method specifically carry out according to following step:
(1) behind the power distribution network generation singlephase earth fault, starting element starts immediately, and the three-phase voltage that records according to the protection installation place can get the fault residual voltage
:
(A)
In the formula:
,
,
Be respectively faulty line A, B, C three-phase voltage;
k=1,2,3
N,
NBe sample sequence length;
(2) the residual voltage data of latter two cycle of extraction one-phase earthing failure in electric distribution network utilize wavelet transformation technique that it is decomposed, and extract each frequency band energy, establish discrete signal
x(
n), the wavelet coefficient under each decomposition scale carried out single reconstruct after, the frequency band range of the component of signal institute inclusion information that obtains is suc as formula shown in (B):
(B)
In the formula,
D j (
n) be the wavelet reconstruction coefficient of signal high fdrequency component;
A j (
n) be the wavelet reconstruction coefficient of signal low frequency component;
f s Sample frequency for signal;
j=1,2,3 ... J, J are maximum decomposition scale, original signal sequence
x(
n) can be expressed as each component and, namely
x(
n)=
(C)
Order
D m+ 1
(
n)=
A m (
n), then have
x(
n)=
(D)
In the formula, m is wavelet transform dimension;
(3) for orthogonal wavelet transformation, after the conversion energy of each yardstick can be directly by square the obtaining of the wavelet reconstruction coefficient after its single reconstruct, namely
Choose the db4 small echo two cycles of selected residual voltage signal are carried out respectively 6 layers of wavelet decomposition, namely herein
Obtain the energy value of each layer frequency band according to formula (E);
(4) establishing the high-frequency energy value that first cycle obtains after the fault behind wavelet transformation is
E 11, the high-frequency energy value of second cycle is
E 12, remember the two ratio
ρFor:
(5) after illusory ground connection occurs power distribution network, obtain the residual voltage data of two cycle, utilize step in the said method (1) to step (4) to try to achieve respectively the high-frequency energy value of two cycles, and get its ratio
(6) according to ratio
With set threshold value
Between relationship distinguish singlephase earth fault and illusory ground connection:
When
ρ〉=
ρ SetThe time, be judged to be singlephase earth fault;
When
ρ＜
ρ SetThe time, be judged to be illusory ground connection.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103675537A (en) * | 2013-12-03 | 2014-03-26 | 昆明理工大学 | Power distribution network virtual grounding identification method based on planar adjacent point distances formed by zero sequence voltage adjacent difference |
| CN104777404A (en) * | 2015-04-28 | 2015-07-15 | 上海交通大学 | Distribution network line fault section positioning method based on differential motion energy ratio |
| WO2016065959A1 (en) * | 2014-10-31 | 2016-05-06 | 江苏省电力公司泰州供电公司 | Diagnostic method for ferromagnetic resonance in 10 kv neutral ungrounded system |
| CN110007198A (en) * | 2019-05-16 | 2019-07-12 | 福州大学 | A kind of novel singlephase earth fault starting method |
| CN114879085A (en) * | 2022-07-12 | 2022-08-09 | 北京智芯半导体科技有限公司 | Single-phase earth fault identification method and device, electronic equipment and medium |
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103675537A (en) * | 2013-12-03 | 2014-03-26 | 昆明理工大学 | Power distribution network virtual grounding identification method based on planar adjacent point distances formed by zero sequence voltage adjacent difference |
| CN103675537B (en) * | 2013-12-03 | 2016-07-20 | 昆明理工大学 | A kind of based on the power distribution network Xuhanting oral solution recognition methods of consecutive points distance in the plane of adjacent difference composition of residual voltage |
| WO2016065959A1 (en) * | 2014-10-31 | 2016-05-06 | 江苏省电力公司泰州供电公司 | Diagnostic method for ferromagnetic resonance in 10 kv neutral ungrounded system |
| CN104777404A (en) * | 2015-04-28 | 2015-07-15 | 上海交通大学 | Distribution network line fault section positioning method based on differential motion energy ratio |
| CN104777404B (en) * | 2015-04-28 | 2018-01-12 | 上海交通大学 | Based on differential energy than distribution line fault section location method |
| CN110007198A (en) * | 2019-05-16 | 2019-07-12 | 福州大学 | A kind of novel singlephase earth fault starting method |
| CN110007198B (en) * | 2019-05-16 | 2021-03-02 | 福州大学 | Single-phase earth fault starting method |
| CN114879085A (en) * | 2022-07-12 | 2022-08-09 | 北京智芯半导体科技有限公司 | Single-phase earth fault identification method and device, electronic equipment and medium |
| CN114879085B (en) * | 2022-07-12 | 2022-10-04 | 北京智芯半导体科技有限公司 | Single-phase earth fault identification method and device, electronic equipment and medium |
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