CN110850229A - Power distribution network single-phase earth fault line selection method - Google Patents
Power distribution network single-phase earth fault line selection method Download PDFInfo
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- CN110850229A CN110850229A CN201911078084.XA CN201911078084A CN110850229A CN 110850229 A CN110850229 A CN 110850229A CN 201911078084 A CN201911078084 A CN 201911078084A CN 110850229 A CN110850229 A CN 110850229A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
Abstract
The invention relates to a single-phase earth fault line selection method for a power distribution network, which comprises the following steps: arc light detection; detecting the voltage of each phase to ground; fault line selection: the main control unit judges a line with a fault according to the results of arc detection and voltage detection relative to ground: for any distribution line, if arc light generated by a fault is detected by arc light protection arranged on the line switch cabinet, and the earth voltage effective value after the arc light protection detects that two phases of faults exist in three phases is increased by more than 1.5 times compared with the earth voltage effective value before the fault, the line is judged to be a fault line, and a single-phase earth fault occurs; otherwise, the line is judged not to be the line with the single-phase earth fault.
Description
Technical Field
The invention relates to the field of relay protection of a power system, in particular to a line selection scheme after a single-phase earth fault of a power distribution network.
Background
Most of power distribution networks of 35kV and below in China adopt a neutral point indirect grounding mode, and belong to low-current grounding power grids. When a single-phase earth fault occurs, the fault characteristics are not obvious because the fault current is small and the three-phase line voltage is still symmetrical, so that the difficulty of fault line selection is increased. However, the single-phase ground fault of the power distribution network accounts for more than 80% of the total number of faults of the power distribution line, and most of phase-to-phase faults are developed from the single-phase ground fault, so that the fault occurring line needs to be accurately judged after the single-phase ground fault occurs. At present, fault line selection methods of low-current grounded power grids are mainly divided into a steady-state signal method, a transient-state signal method and an injection signal method. In the aspect of fault line selection by using steady-state signals, documents [1] and [2] respectively provide a power frequency zero-sequence current amplitude comparison method and a phase comparison method, wherein the power frequency zero-sequence current amplitude comparison method is used for realizing fault line selection by using the characteristic that the zero-sequence current of a fault line is larger than the zero-sequence current of a non-fault line, and the phase comparison method is used for realizing fault line selection by using the characteristic that the zero-sequence current of the fault line is opposite to the zero-sequence current of the non-fault. Document [3] proposes that 5-order harmonic components of zero-sequence current are used to form a line selection criterion, but the magnitude of the 5-order harmonic components in fault current is closely related to system parameters, fault time and other factors, so that the line selection success rate is not high. In the aspect of selecting a line for a fault by using a transient signal, document [4] determines a characteristic frequency band in which transient capacitance current distribution of each line is most concentrated according to an energy maximization principle, and adaptively realizes the line selection for the fault by comparing polarities of wavelet packet decomposition coefficients of all lines in respective characteristic frequency bands according to a principle that polarities of transient capacitance currents of the fault lines are different from those of non-fault lines. Document [5] proposes that the frequency division characteristic and the reconstruction algorithm of the wavelet are utilized to respectively obtain the reconstruction signals of the direct current component and the fundamental frequency component in the zero-sequence current of each line, and the fault line is determined according to the difference of the energy ratio of the direct current component and the fundamental frequency component in the zero-sequence current of the fault line and the zero-sequence current of the non-fault line. Document [6] decomposes the zero sequence current by using a wavelet packet, and performs ground fault line selection by comparing the signs of the reconstructed current instantaneous values in a characteristic frequency band selected according to the energy maximum principle. Document [7] analyzes the fault transient characteristics at different fault moments and under transition resistance, introduces energy ratio factors for reflecting different frequency component ratios and transient factors for reflecting the magnitude of the transition resistance, combines the energy ratio factors and the transient factors to judge the phase position of phase voltage and the magnitude of the transition resistance at the fault moments, and adopts corresponding line selection criteria for different conditions. Document [8] proposes to implement fault line selection and location by detecting fault traveling waves, and the method puts high requirements on accurate identification of fault wave heads. In the aspect of fault line selection by using an active injection method, document [9] proposes that a high-frequency signal is injected into a system, the high-frequency signal is injected into the system from a grounding transformer and passes through a grounding fault point to form a loop, and fault line selection is realized by detecting whether the high-frequency signal exists in each line, wherein the main defect is that impact is caused on a primary system. From the above analysis, the existing power distribution network single-phase earth fault line selection method is not perfect, and the research on the single-phase earth fault line selection method has important theoretical value and practical value.
Reference to the literature
[1] Lugao, a fault line selection method [ J ] based on a zero-sequence current amplitude comparison method, university of North and Central university, school newspaper (Nature science edition), 2014,35(04): 473-plus 478.
[2] Lesen, Song nationality, Kangxianning, Xue Xiaoxiaohui, Wangui Lin, Sunnan Jiale.Small current ground fault line selection [ J ] based on time domain correlation analysis method power system protection and control, 2008(13):15-20.
[3] Wang Zuhuang, microcomputer small current grounding system grounding selection device [ J ] electric power system automation, 1993(06):48-51.
[4] Daifeng, Zhanxia, adaptive power distribution network fault line selection research based on multi-band analysis [ J ]. China Motor engineering reports, 2003(05):45-48.
[5] Application of Daifeng, Zhanxia, Houji wavelet reconstruction algorithm in distribution network grounding line selection [ J ] power grid technology, 2004(03):43-47.
[6] Study on grounding line selection device of power distribution network based on digital signal processor and wavelet packet reconstruction algorithm [ J ] power grid technology, 2005(04):50-54.
[7] Zhanyanxia, King Qing Liang, a new method for realizing fault line selection of a power distribution network by using fault transient characteristics [ J ]. power system automation, 2009,33(16):76-80.
[8]Ali-Reza Sedighi,Mahmood-Reza Haghifam,O.P.Malik,Mohammad-HassanGhassemian.High Impedance Fault Detection Based on Wavelet Transform andStatistical Pattern Recognition[J].IEEE TRANSACTIONS ON POWER DELIVERY,2005,20(4):2414-2421.
[9] Power automation equipment, 1999(03) 20-22, "S injection method" and line selection positioning "in wanhui, fangying, morus.
Disclosure of Invention
The invention provides a new method for single-phase earth fault line selection of a power distribution network. The fault line is accurately judged after the single-phase earth fault occurs in the power distribution network, the fault is timely eliminated to avoid further development of phase-to-phase fault, and the power supply is recovered as soon as possible to improve the power supply reliability of the power distribution network. The technical scheme is as follows:
a single-phase earth fault line selection method for a power distribution network comprises the following steps:
(1) arc light detection, namely arranging arc light protection on a switch cabinet of a distribution line, detecting whether arc light generated by faults exists in the line by using an arc light protection system, converting the result of the arc light detection into a digital signal and sending the digital signal to a main control unit.
(2) Detection of the voltages relative to the ground: measuring each relative earth voltage effective value of the circuit after the fault occurs by using a voltage transformer, comparing the value with each relative earth voltage effective value of the circuit before the fault, judging whether each relative earth voltage effective value after the fault is increased by more than 1.5 times relative to each relative earth voltage effective value of the circuit before the fault, and sending information of detection and judgment of each relative earth voltage to a main control unit;
(3) fault line selection: the main control unit judges a line with a fault according to the results of arc detection and voltage detection relative to ground: for any distribution line, if arc light generated by a fault is detected by arc light protection arranged on the line switch cabinet, and the earth voltage effective value after the arc light protection detects that two phases of faults exist in three phases is increased by more than 1.5 times compared with the earth voltage effective value before the fault, the line is judged to be a fault line, and a single-phase earth fault occurs; otherwise, the line is judged not to be the line with the single-phase earth fault.
The invention has the following beneficial effects:
1. the principle is clear. The invention is based on the non-fault phase voltage rise after the faultAnd arc light is generated at the fault point to judge the fault line.
2. And the implementation is easy. Only the installed arc protection device and the voltage transformer are needed to be utilized, and new equipment does not need to be additionally arranged.
Drawings
FIG. 1 is a diagram showing a distribution of a capacitance current when a single phase is grounded
FIG. 2A is a voltage-current phasor diagram with phase grounding
FIG. 3 is a schematic diagram of single-phase earth short circuit fault line selection
Detailed Description
In the distribution network shown in figure 1, the generator G is provided with two distribution lines, and the distributed capacitance to ground of the generator G, the line I and the line II is respectively concentrated by a capacitor C0G、C0IAnd C0IIAnd (4) showing. After single-phase earth fault occurs, if influence of voltage drop of three-phase symmetrical load current and capacitance current on line impedance is not considered, earth voltage of fault phase of whole system is equal to zero, and non-fault earth voltage is increased to line voltage, namely increasedAnd (4) doubling. Taking phase-a ground fault as an example, the voltages of each phase are listed in equation (1), the corresponding voltage phasors are shown in fig. 2,
and
is the three-phase potential of the generator.
After phase a is grounded, the capacitance-to-ground current distribution in the system is shown in fig. 1. On the non-fault line I, the A phase current is zero, and the B phase and the C phase have capacitance current flowing to the fault point
And
the expression of each phase current is
Having an effective value ofThe phase quantities of the individual phases are also indicated in fig. 2. Due to the distributed capacitance C to the ground of the distribution line0IVery small, so not faulty, lines IBIAnd ICIThe values are small and even smaller than the load current in case of short lines.
On the faulty line II, the earth point is returned to the sum of the B-phase and C-phase capacitive currents of the whole system, i.e.
Having an effective value of
IE＝3EAω(C0I+C0II+C0G) (4)
The current is to flow from the A phase back to the generator, so that the current flowing from the A phase is
The B phase and the C phase flow own capacitance current, and the expression of each phase current is
It can be seen that when phase A is grounded, the fault line is on phase II
The value of the capacitance current to ground of each phase is very small; the phase A current is the sum of the capacitance current of the whole system to the ground, and although the value is larger than that of the phase B and the phase C current, the value is smaller than that of the interphase short circuit current. The lack of significance of the fault signature presents difficulties in fault routing.
When a single-phase earth fault occurs in the power distribution network, a small gap exists between a line at a fault point and the ground, air in the gap is ionized due to thermionic emission caused by heating, so that the air has good conductivity, and an electric arc is generated between the line and the ground. Such arcs are usually unstable with alternating extinction and re-ignition, and intermittent arcs cause transient changes in the grid operating conditions, resulting in strong oscillations of electromagnetic energy. The ionization of air can produce a large amount of anion and cation and free electron, and they are constantly collided and compounded in the course of moving, release the energy and produce the dazzling arc light, its energy is mainly concentrated in ultraviolet light wave band and visible light wave band, the illumination intensity can reach thousands times of normal illumination intensity, utilize the arc light sensor to detect the production of arc light fast through the light intensity that detects the sudden increase.
Arc light protection is provided in medium and low voltage buses, distribution line switch cabinets and box-type substations at present. The arc sensor is used for detecting arc light generated by a fault and transmitting the information to the main control unit, and the main control unit judges whether the fault occurs according to the action information of the arc sensor and the current sudden change of each phase. When a single-phase earth fault occurs in the power distribution network, each phase of current is changed into capacitance current to ground from load current before the fault, and the current sudden change amount is too small, so the existing arc protection cannot reflect the single-phase earth fault.
Considering that two non-fault phase voltages can be increased after single-phase earth fault
The invention utilizes the characteristics of the two points that the over-voltage relay and the arc light sensor action information AND gate form single-phase earth fault line selection protection, and the functional block diagram of the invention is shown in figure 3. When a single-phase earth fault occurs to the A phase of one distribution line, the voltage transformer measures the voltage U between the B phase and the C phase relative to the earthB-EAnd UC-EIs raisedTriggering an AND logic 3 action, so that an OR logic 1 action is performed; the arc sensor on the distribution line detects the generation of arc light, and the corresponding relay L>"act; relay "L>The "action and" or logic 1 "action cause the and logic 4 action to select the line as the faulty line. The action process of phase B grounding and phase C grounding is similar.
Claims (1)
1. A single-phase earth fault line selection method for a power distribution network comprises the following steps:
(1) arc light detection, namely arranging arc light protection on a switch cabinet of a distribution line, detecting whether arc light generated by faults exists in the line by using an arc light protection system, converting the result of the arc light detection into a digital signal and sending the digital signal to a main control unit.
(2) Detection of the voltages relative to the ground: measuring each relative earth voltage effective value of the circuit after the fault occurs by using a voltage transformer, comparing the value with each relative earth voltage effective value of the circuit before the fault, judging whether each relative earth voltage effective value after the fault is increased by more than 1.5 times relative to each relative earth voltage effective value of the circuit before the fault, and sending information of detection and judgment of each relative earth voltage to a main control unit;
(3) fault line selection: the main control unit judges a line with a fault according to the results of arc detection and voltage detection relative to ground: for any distribution line, if arc light generated by a fault is detected by arc light protection arranged on the line switch cabinet, and the earth voltage effective value after the arc light protection detects that two phases of faults exist in three phases is increased by more than 1.5 times compared with the earth voltage effective value before the fault, the line is judged to be a fault line, and a single-phase earth fault occurs; otherwise, the line is judged not to be the line with the single-phase earth fault.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111624439A (en) * | 2020-05-18 | 2020-09-04 | 南方电网科学研究院有限责任公司 | Fault line selection method based on inverter injection characteristic signal |
| CN112993936A (en) * | 2020-12-14 | 2021-06-18 | 山东鲁圣电气设备有限公司 | Integrated protection method, system, terminal and storage medium for box-type substation |
| CN113093049A (en) * | 2021-03-19 | 2021-07-09 | 威胜集团有限公司 | Fault arc positioning diagnosis method and device and computer readable storage medium |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111624439A (en) * | 2020-05-18 | 2020-09-04 | 南方电网科学研究院有限责任公司 | Fault line selection method based on inverter injection characteristic signal |
| CN112993936A (en) * | 2020-12-14 | 2021-06-18 | 山东鲁圣电气设备有限公司 | Integrated protection method, system, terminal and storage medium for box-type substation |
| CN112993936B (en) * | 2020-12-14 | 2022-08-26 | 山东鲁圣电气设备有限公司 | Integrated protection method, system, terminal and storage medium for box-type substation |
| CN113093049A (en) * | 2021-03-19 | 2021-07-09 | 威胜集团有限公司 | Fault arc positioning diagnosis method and device and computer readable storage medium |
| CN113093049B (en) * | 2021-03-19 | 2023-10-03 | 威胜集团有限公司 | Fault arc location diagnosis method, device and computer readable storage medium |
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