CN111983507B - Arc light ground fault detection method based on volt-ampere characteristic dynamic track - Google Patents
Arc light ground fault detection method based on volt-ampere characteristic dynamic track Download PDFInfo
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Abstract
An arc light ground fault detection method based on a volt-ampere characteristic dynamic track comprises the following steps: (1) Zero mode current i at feeder outlet of power distribution system 0 (t) and zero mode voltage u 0 (t) continuous sampling is performed when at a certain time t s The instantaneous polarity of the zero mode voltage is opposite to that of the zero mode current, and the detection program is started; (2) obtaining a sequence of discrete values; (3) data for both sequences; carrying out per unit to obtain a 1/4 cycle discrete value sequence containing N points; (4) The initial reverse polarity characteristics of zero mode voltage and zero mode current and the clockwise characteristics of the dynamic track of volt-ampere characteristics in 1/4 cycle are used as the basis for arc grounding fault identification, so that the detection of arc grounding faults is realized; the invention is not affected by transition resistance and fault initial phase angle, can rapidly and reliably identify the occurrence of arc grounding fault of the neutral point through arc suppression coil grounding power distribution system, rapidly cuts off the fault, protects personnel life safety, and has wide engineering application prospect.
Description
Technical Field
The invention belongs to the technical field of relay protection of distribution lines of power systems, and particularly relates to an arc grounding fault detection method based on a dynamic track of volt-ampere characteristics.
Background
The distribution network utilizes distribution equipment to distribute the electric energy from a power transmission network and a power plant on site or distribute the electric energy to various users step by step according to voltage levels, and safe and stable operation is an important guarantee for reliable power supply of the users. The distribution network has a complex structure, the neutral point grounding modes are changeable, the fault probability is higher, wherein the proportion of single-phase grounding faults is the largest, and the proportion of single-phase grounding faults is about 80% of the total number of faults.
The distribution network can be divided into the following modes according to the neutral point grounding modes: neutral point active ground system and neutral point inactive ground system. The neutral point effective grounding system mainly uses neutral point grounding through small resistor belongs to large current grounding system, when single-phase grounding fault occurs, the amplitude value of fault current is relatively large, and detection is relatively easy. The neutral point non-effective grounding distribution network mainly comprising a neutral point grounding distribution system through an arc suppression coil belongs to a typical small-current grounding system, no obvious power frequency fault current loop exists when single-phase grounding faults occur, and the steady-state fault current amplitude is smaller; because of the compensation effect of the arc suppression coil, the fault power frequency current loses obvious direction characteristics, and the detection difficulty is high. In addition, when single-phase earth faults occur, the voltage difference between the line and the earth often causes breakdown of the air gap or solid dielectric insulation, resulting in the generation of an earth arc.
For a neutral point through arc suppression coil grounding distribution system, with the massive use of the existing fault detection technology based on traveling wave and transient state quantity, the positive rate of fault detection has been improved to a certain extent, especially for faults with metallic or lower transition resistance, the positive rate has reached more than 90%, but unfortunately, in recent years, serious accidents such as personal electric shock casualties and induced mountain fire caused by single-phase grounding faults still occur frequently, and the main reasons are as follows: when such faults occur, the circuit is grounded through nonlinear conductive media such as branches, sandy lands, turf and the like, and nonlinear arcs are generated under most conditions, and the existing fault detection method exposes obvious defects when coping with the nonlinear arc grounding faults, such as: the influence of nonlinear arc is not considered, weak electric quantity of arc grounding faults cannot be effectively dealt with, sensitivity is poor, and the like, so that faults exist for a long time and cannot be found timely, and the faults develop into more serious two-phase short-circuit faults, even three-phase short-circuit faults, even fire disasters, damage to power equipment, personnel electric shock casualties and the like are caused.
At present, most fault detection methods have insufficient attention to arc ground fault detection, and few methods which can be clearly used for arc ground fault detection are available. The existing fault detection method is divided into different types from the line selection point of view: steady state analysis, transient analysis, traveling wave, and artificial intelligence.
The steady-state analysis method is mostly only suitable for metallic ground faults, and the detection effect on arc ground faults is often poor, and the root of the steady-state analysis method is as follows: when an arc grounding fault occurs in the neutral point through the arc suppression coil grounding power distribution system, the content of steady-state electric quantity such as power frequency current, active component, single harmonic component and the like is low, the detection difficulty is high, misjudgment based on the direction, amplitude and the like of the electric quantity is easy to cause, and the reliability is poor. Most transient analysis methods have obvious fault characteristics when the transition resistance is not large, and have relatively reliable detection effects, but when the arc grounding fault is dealt with, the reliability of a detection algorithm is poor due to the nonlinearity of the grounding arc and the high grounding resistance. The traveling wave method has the greatest advantages that the traveling wave method is not influenced by a neutral point operation mode, the interference of an arc suppression coil can be eliminated, but the sensitive starting of the method is easily limited by a transition resistance. In an actual neutral point through arc suppression coil grounding distribution system, the defects of extremely few fault sample data, inconsistent sample selection standards and unclear physical meaning in arc grounding fault detection are fatal defects of an artificial intelligence method.
The existing arc grounding fault detection method takes zero sequence voltage, zero sequence current or amplitude out-of-limit of an initial traveling wave head as a starting mark of a detection algorithm, so that an accurate setting value is difficult to set in practice, and reliability and sensitivity cannot be considered.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide an arc grounding fault detection method based on a dynamic track with volt-ampere characteristics, which takes the instantaneous reverse polarity characteristics of zero-mode voltage and zero-mode current and the dynamic track with volt-ampere characteristics with clockwise characteristics in 1/4 cycle as the basis of arc grounding fault detection and has higher reliability and sensitivity.
In order to achieve the above purpose, the technical proposal of the invention is that
An arc light ground fault detection method based on a volt-ampere characteristic dynamic track comprises the following steps:
step (1),Zero mode current i at feeder outlet of power distribution system 0 (t) and zero mode voltage u 0 (t) continuous sampling is performed when at a certain time t s The instantaneous polarity of the zero-mode voltage is opposite to that of the zero-mode current, i.e.) 0 (t s )×u 0 (t s )<0, starting a detection program, and judging: suspected arc grounding faults occur, and the step (2) is carried out;
step (2), taking 5 kHz-20 kHz at a certain sampling rate f, extracting a zero sequence voltage and a zero sequence current sequence with the 1/4 cycle length of N at the outlet of the line, and respectively recording as f 0 (i)、f 1 (i) I=1, 2, … … N, and using chebyshev digital filter pair f 0 (i)、f 1 (i) Band-pass filtering, setting upper and lower limits of passband cut-off frequency to 140Hz and 1000Hz, setting upper and lower limits of stopband cut-off frequency to 100Hz and 1050Hz to obtain two discrete value sequences of 1/4 cycle of electric quantity, and respectively recording as f 0 (j)、f 1 (j)，j＝1,2,……N；
Step (3), pair f 0 (j)、f 1 (j) The data of the two sequences are respectively taken as the standard of the maximum value to carry out per unit, and a 1/4 cycle discrete value sequence i containing N points is obtained 0 (m)、u 0 (m)，m＝1,2,……N：
Step (4), i is carried out 0 (m)、u 0 (m) coordinate point sequences p= [ P ] combined to form a volt-ampere characteristic curve 1 (x 1 ,y 1 ),P 2 (x 2 ,y 2 ),P 3 (x 3 ,y 3 ),…P N (x N ,y N )]And calculate all the successive two vector spaces respectively by using the formula (2)
And->
The rotation angle θ= [ θ ] 1 ,θ 2 ,…θ N-1 ]；
θ＝atan2[(x m-1 y m -x m y m-1 )/(x m-1 x m +y m-1 y m )] (2)
Step (5), satisfy θ each time Front part ×θ Rear part (S) Counting for 1 time if the total count is less than or equal to 0, wherein the total count is represented by M, if the total count M is greater than a setting value P, noise or other external interference is judged, the step (1) is restarted, and if the total count M is less than or equal to P, the step (6) is started, and the setting value P is 1/4N;
step (6), calculating the sum sigma theta of all included angles by using a formula (3), if the sum sigma theta is more than or equal to 0, a counter-clockwise volt-ampere characteristic dynamic track is provided, and the step (1) is restarted; if Sigma theta is less than 0, the dynamic track with clockwise volt-ampere characteristic is judged as follows: an arc ground fault occurs;
∑θ＝θ 1 +θ 2 +…+θ n-1 (3)。
the invention has the advantages that: the detection algorithm provided by the invention takes the instantaneous reverse polarity characteristics of zero mode voltage and zero mode current as the starting criteria of the arc grounding fault detection algorithm, so that the high sensitivity of the algorithm is ensured; the reliable discrimination of arc grounding faults can be realized by using the dynamic track with the volt-ampere characteristic with the clockwise characteristic in 1/4 cycle, the high reliability of the algorithm is ensured, the detection algorithm is not influenced by external interference such as transition resistance, fault initial phase angle, noise and the like, the fault can be timely and effectively identified, the damage of the fault is reduced, and the method has important significance for quickly recovering the stable operation of a power system.
Drawings
Fig. 1 is a flow chart of arc ground fault detection for a neutral point through arc suppression coil grounding power distribution system in accordance with an embodiment of the present invention.
Fig. 2 is a schematic diagram of a 10kV distribution line model employed in the present invention.
Detailed Description
The invention provides an arc grounding fault detection method for a neutral point grounding distribution system through an arc suppression coil based on a volt-ampere characteristic dynamic track, which is characterized by comprising the following steps of:
the embodiment of the invention adopts a 10kV distribution line model, as shown in figure 2, and the system comprises F 1 -F 4 A total of 4 feeders: 1 branch line, 1 pure cable line, 1 cable hybrid line, 1 pure overhead line; is arranged at 0.165s at a feeder F 3 An arc grounding fault occurs at a distance of 10km from the bus bar, and the transition resistance at the fault point is regarded as an arc resistance R arc And a fixed resistor R con (200 ohms) series, arc resistance was determined by a nonlinear logarithmic arc model, set the arc suppression coil compensation to 8%, and the sampling frequency f=10khz of the simulation model.
According to the detection algorithm flow chart shown in fig. 1:
step (1), real-time monitoring is carried out on zero-mode voltage and zero-mode current at the outlet of a feeder line; at 0.165s, the product of the zero mode voltage instantaneous value (-82.18V) and the zero mode current instantaneous value (3.88A) is less than 0, and judging: suspected arc grounding faults occur, and a detection algorithm is started;
step (2), extracting zero-mode current and zero-mode voltage of 1/4 cycle, respectively denoted as f 0 (i)、f 1 (i)：
Using chebyshev digital filter pairs f 0 (i)、f 1 (i) Band-pass filtering, setting upper and lower limits of passband cut-off frequency to 140Hz and 1000Hz, setting upper and lower limits of stopband cut-off frequency to 100Hz and 1050Hz to obtain N-point-containing discrete value sequences of two electric quantity 1/4 cycle waves, and respectively recording as f 0 (j)、f 1 (j)，j＝1,2,……N；
Step (3), pair f 0 (j)、f 1 (j) The data of the two sequences are respectively subjected to per unit at the respective maximum value; obtaining a 1/4 cycle sequence i containing N point discrete values 0 (m)、u 0 (m)：
Step (4), i is carried out 0 (m)、u 0 (m) coordinate point sequences p= [ P ] combined to form a volt-ampere characteristic curve 1 (x 1 ,y 1 ),P 2 (x 2 ,y 2 ),P 3 (x 3 ,y 3 ),…P m (x m ,y m )]And calculate all the successive two vector spaces respectively by using the formula (2)
And (3) with
The rotation angle θ= [ θ ] 1 ,θ 2 ,…θ m-1 ]：/>
Step (5) of satisfying theta Front part ×θ Rear part (S) The total times M=0 less than or equal to 0 is less than the setting value P, and the setting value P is recommended to take 1/4N;
step (6), using the sum of all included angles sigma theta= -404.16 degrees <0 calculated by the formula (3), indicating the volt-ampere characteristic dynamic track with clockwise characteristic, judging: the feeder line experiences an arc ground fault.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (1)
1. The arc light ground fault detection method based on the volt-ampere characteristic dynamic track is characterized by comprising the following steps of:
step (1), zero mode current i at feeder outlet of distribution system 0 (t) and zero mode voltage u 0 (t) continuous sampling is performed when at a certain time t s The instantaneous polarity of the zero-mode voltage is opposite to that of the zero-mode current, i.e.) 0 (t s )×u 0 (t s )<0, starting a detection program, and judging: suspected arc grounding faults occur, and the step (2) is carried out;
step (2), taking 5 kHz-20 kHz at a certain sampling rate f, extracting a zero sequence voltage and a zero sequence current sequence with the 1/4 cycle length of N at the outlet of the line, and respectively recording as f 0 (i)、f 1 (i) I=1, 2, … … N, and using chebyshev digital filter pair f 0 (i)、f 1 (i) Band-pass filtering, setting upper and lower limits of passband cut-off frequency to 140Hz and 1000Hz, setting upper and lower limits of stopband cut-off frequency to 100Hz and 1050Hz to obtain two discrete value sequences of 1/4 cycle of electric quantity, and respectively recording as f 0 (j)、f 1 (j)，j＝1,2,……N；
Step (3), pair f 0 (j)、f 1 (j) The data of the two sequences are respectively taken as the standard of the maximum value to carry out per unit, and a 1/4 cycle discrete value sequence i containing N points is obtained 0 (m)、u 0 (m)，m＝1,2,……N：
Step (4), i is carried out 0 (m)、u 0 (m) coordinate point sequences p= [ P ] combined to form a volt-ampere characteristic curve 1 (x 1 ,y 1 ),P 2 (x 2 ,y 2 ),P 3 (x 3 ,y 3 ),…P N (x N ,y N )]And calculate all the successive two vector spaces respectively by using the formula (2)
And->
The rotation angle θ= [ θ ] 1 ,θ 2 ,…θ N-1 ]：
θ＝atan2[(x m-1 y m -x m y m-1 )/(x m-1 x m +y m-1 y m )] (2)
Step (5), satisfy θ each time Front part ×θ Rear part (S) Counting for 1 time if the total count is less than or equal to 0, wherein the total count is represented by M, if the total count M is greater than a setting value P, noise or other external interference is judged, the step (1) is restarted, and if the total count M is less than or equal to P, the step (6) is started, and the setting value P is 1/4N;
step (6), calculating the sum sigma theta of all included angles by using a formula (3), if the sum sigma theta is more than or equal to 0, a counter-clockwise volt-ampere characteristic dynamic track is provided, and the step (1) is restarted; if Sigma theta is less than 0, the dynamic track with clockwise volt-ampere characteristic is judged as follows: an arc ground fault occurs;
∑θ＝θ 1 +θ 2 +…+θ n-1 (3)。
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