Background technology
Power distribution network is directly connected with user, and its reliability determines the power supply quality of electric system to a great extent.The power supply reliability improving power distribution network improves the important research content of power system power supply reliability.Traditional distribution network line many employings radiation type electric supply mode, take-off point place is without isolating switch and opertaing device, and the required time that restores electricity is long, have impact on the reliability that power distribution network is powered.In recent years, along with the development of intelligent grid, " self-healing " will become the basic function of electrical network, and fault section location is as the basis of self-healing, is the important research content of intelligent grid.
China's power distribution network adopts neutral point small current neutral grounding mode mostly, and by the impact of the factors such as neutral grounding mode, power distribution network scale, transition resistance, failure line selection problem is never satisfactorily resolved, and does not more know where to begin in section location.Can produce larger short-circuit current during small current neutral grounding system generation phase-to phase fault, its section location is easy to realize.But when there is singlephase earth fault, short-circuit current is little, and the curent change flowing through fault and non-fault line is only the change of capacitive earth current.Special in system neutral is through grounding through arc, and when adopting over-compensation mode to work, utilize the change of power frequency amount to be difficult to distinguish faulty line and non-fault line.Therefore transient can only be adopted to carry out route selection for the system through grounding through arc, and during single-phase earthing, the transient state component of earthing capacitance current may be larger than steady-state value several times to tens times.
Selection method sensitivity based on transient signal is higher and not by the impact of arc suppression coil, but existing method is left to be desired mostly.Utilize in transient method existing, first half-wave method occurs in faulted phase voltage close to this assumed condition near maximal value based on singlephase earth fault, and when phase voltage zero cross near fault, transient is faint, is difficult to meet the demands.Although the extraction fault-signal that wavelet analysis method can be more accurate, also exists some problems, as the method is too responsive to micro-variable, poor anti jamming capability; When trouble spot is through great transition resistance eutral grounding, the method can not be carried out.Traveling wave method is difficult to accurate seizure due to wavefront after fault, and sample frequency requires high factor, is difficult to realize.Can find out based on above all factors, the route selection problem of small current neutral grounding system is the problem do not resolved always, and section Position Research achievement is not more known where to begin, so research fault section location method will bring important realistic meaning to the intellectuality of power distribution network.
Summary of the invention
The object of the present invention is to provide a kind of one-phase earthing failure in electric distribution network Section Location based on parameter identification.
For achieving the above object, present invention employs following technical scheme:
This localization method comprises the following steps: by selected first capacitive frequency band, every bar circuit is simplified to capacitor model in zero-sequence network, under the Voltage Reference direction of specifying and current reference direction, utilize the residual voltage at route survey point place and zero-sequence current to solve capacitance, according to the positive and negative failure judgement point of described capacitance whether on the rear circuit of measurement point corresponding to capacitance, thus realize the section location of trouble spot.
If the capacitance corresponding with certain measurement point Tp is negative, then judge that trouble spot is on the rear circuit of measurement point Tp.
Described Voltage Reference direction be measurement point relative to ground, current reference direction is to circuit by bus.
Described first capacitive frequency band is 150Hz ~ 600Hz.
The concrete steps of described localization method comprise:
Step one: after system generation singlephase earth fault, at route survey point, place carries out synchronized sampling to residual voltage and zero-sequence current, then by analog to digital converter, the sample residual voltage that obtains and zero-sequence current is converted into digital quantity;
Step 2: the bandpass filtering treatment that frequency band is 150Hz ~ 600Hz is carried out to described digital quantity, obtain the zero-sequence current component and zero sequence voltage component that correspond to frequency band, ask for the derivative value of zero sequence voltage component by two point value differential formulas, then utilize the ratio of zero-sequence current component and described derivative value and identify corresponding capacitance in conjunction with least-squares algorithm;
Step 3: select distance transformer station section farthest from capacitance is negative section, described distance transformer station section is farthest fault section.
Beneficial effect of the present invention is embodied in:
One-phase earthing failure in electric distribution network Section Location based on parameter identification of the present invention, utilize the first thought holding frequency range, by asking for the foundation of the capacitance corresponding to the capacitor model that simplified by circuit as fault section location, the method principle is simple, be easy to realize, quickly and reliably can carry out fault section location, the method both can be used for isolated neutral distribution system, also can be used for the distribution system of neutral by arc extinction coil grounding.
Embodiment
Below in conjunction with accompanying drawing, the present invention is further illustrated.
Based on an one-phase earthing failure in electric distribution network Section Location for parameter identification, be specifically described as follows:
During distribution generation singlephase earth fault, hold in frequency range at head, the zero sequence model perfecting circuit and rear, trouble spot circuit can be equivalent to an electric capacity, be now a scale-up factor between its zero-sequence current and derivative of residual voltage is positive direct proportion function; And for faulty line, its zero sequence model is made up of the circuit of system dorsal part, holds in frequency range at head and also can be equivalent to an electric capacity, but under appointment reference direction, be proportion function that scale-up factor is negative between its zero-sequence current and residual voltage derivative.
See Fig. 1, it is isolated neutral or through grounding through arc that K switch controls neutral grounding mode, R
_{0x}, L
_{0x}, C
_{0x}be respectively circuit x resistance, inductance, capacitance parameter, i
_{0x}represent the zero-sequence current (x=1 ~ n) of circuit x.When trouble spot is positioned on i-th circuit, the part of circuit on both sides, trouble spot respectively uses model representation, wherein a R
_{0f}, L
_{0f}, C
_{0f}for line parameter circuit value between front, trouble spot and bus.U
_{0f}represent the equivalent residual voltage source of fault point, 3L represents the inductance of arc suppression coil, R
_{f}represent transition resistance during earth fault, i
_{0f}represent the zero-sequence current on circuit between trouble spot and bus, i
_{0i}represent the zero-sequence current of rear, trouble spot circuit, i
_{l}represent the zero-sequence current on arc suppression coil, u
_{0}represent the residual voltage on bus.After the fault represented by Fig. 1 is occurred, the zero-sequence network of circuit can be reduced to simplified model as shown in Figure 2.
See Fig. 2, C
_{0k ∑}(k=1 ~ n) represents each zero sequence equivalent capacitance value perfecting circuit and faulty line trouble spot rear portion, R
_{0f}, L
_{0f}, C
_{0f}for line parameter circuit value between front, trouble spot and bus, u
_{0f}represent the equivalent residual voltage source of fault point, 3L represents the inductance of arc suppression coil, C
_{oi ∑}represent the zero sequence equivalent capacitance value of rear, trouble spot circuit.
Can simplify further on the basis of simplified model, see Fig. 3, K switch open and close respectively corresponding isolated neutral and through grounding through arc, R
_{0f}, L
_{0f}, C
_{0f}for line parameter circuit value between front, trouble spot and bus, C
_{h}for all total electric capacity perfecting line equivalent, u
_{0f}represent the equivalent residual voltage source of fault point, 3L represents the inductance of arc suppression coil.
For perfecting circuit and rear, trouble spot circuit has:
${i}_{0k}={C}_{0\mathrm{k\Σ}}\·\frac{{\mathrm{du}}_{0}}{\mathrm{dt}}---\left(1\right)$
C in formula (1)
_{0k ∑}for each zero sequence equivalent capacitance value perfecting circuit or faulty line trouble spot rear portion.
Circuit for front, trouble spot has:
${i}_{0f}=-{C}_{0}^{\text{'}}\·\frac{{\mathrm{du}}_{0}}{\mathrm{dt}}---\left(2\right)$
C ' in formula (2)
_{0}for the zero sequence equivalent capacitance value of faulty component line fault point forward portion.
Therefore, hold the thought (source: Automation of Electric Systems, 2003,27 (9): 48-53) of frequency range based on head, after system generation singlephase earth fault, the first frequency band that holds can be selected every bar circuit is simplified to a capacitor model in zero-sequence network.Utilize the residual voltage at route survey point place, zero-sequence current solves capacitance.Judge actual breaking down whether on the circuit of corresponding measurement point rear according to the capacitance that obtains positive and negative, judges that capacitance is for bear and from the most farther of bus (transformer station) as place, trouble spot section, thus the section realizing trouble spot is located.
Concrete steps are as follows:
Step one: utilize the ground fault detection device that each line outlet and bifurcation are installed, after system generation singlephase earth fault, at route survey point, place carries out synchronized sampling to residual voltage, zero-sequence current with predetermined sampling rate, then by analog to digital converter, residual voltage, the zero-sequence current obtained of sampling is converted into digital quantity;
Step 2: bandpass filtering treatment is carried out to the digital quantity obtained, frequency band is 150Hz ~ 600Hz, obtain the zero-sequence current component to this frequency band and zero sequence voltage component, its derivative value is asked for the two point value differential formulas of zero sequence voltage component now, then utilizes least-squares algorithm to identify corresponding capacitance.
Step 3: positive and negative by the capacitance of step 2 identification, carries out fault section location, the method for fault section location: chosen distance transformer station distance section (being fault section) farthest from the electric capacity identified is negative section.
The realistic model that the present invention adopts as shown in Figure 4; concrete parameter is shown in (protecting electrical power system and control; 2008; 36 (13): 15-20.) 1 ~ 6 trouble spot is provided with in emulation; position respectively at section 1., 5., 7., 2., 3. with section 8., sector number (1.-9.) is as shown in Figure 4.For the sake of simplicity, the singlephase earth fault of setting is all for A phase, and G represents the equivalent source of distribution network systems, and L represents arc suppression coil inductance, and S1-S6 represents the load of 6 feeder terminals respectively.
Isolated neutral distribution system section 1(faulty line) perfect circuit with section 2() get fault after 0.02s data through data window length be the oscillogram of 40 sampled points cunning window draw calculation electric capacity as shown in Figure 5; Distribution system section 1(faulty line through grounding through arc) perfect circuit with section 2() get fault after 0.02s data through data window length be the oscillogram of 40 sampled points cunning window draw calculation electric capacity as shown in Figure 6.As can be seen from Fig. 5, Fig. 6, in transient state situation, perfect the capacitance of line computation basicly stable on the occasion of, and fault wire has obvious fluctuation, but basicly stable be negative value, be so just easy to judge whether section is fault section.No matter can be further illustrated by the emulated data of table 1-table 4 is at arc suppression coil earthing system, or in isolated neutral system, can utilize and identify that the positive and negative of equivalent capacity carries out fault section location.
When table 1 is isolated neutral distribution system trouble spot generation Single Phase Metal ground connection, the capacitance that each section identification calculates, the trouble spot in table and the implication of section are with the statement in Fig. 4.
Table 1 isolated neutral system simulation result (one)
Table 2 crosses resistance 200 for isolated neutral distribution system trouble spot course of emergency
_{Ω}during single-phase earthing, the capacitance that each section identification calculates, the trouble spot in table and the implication of section are with the statement in Fig. 4.
Table 2 isolated neutral system simulation result (two)
When table 3 is neutral by arc extinction coil grounding distribution system trouble spot generation Single Phase Metal ground connection, the capacitance that each section identification calculates, the trouble spot in table and the implication of section are with the statement in Fig. 4.
Table 3 arc suppression coil earthing system simulation result (one)
Table 4 crosses resistance 200 for neutral by arc extinction coil grounding distribution system trouble spot course of emergency
_{Ω}during single-phase earthing, the capacitance that each section identification calculates, the trouble spot in table and the implication of section are with the statement in Fig. 4.
Table 4 arc coil earthed system simulation result (two)