Background technology
Power distribution network directly is connected with the user, and its reliability has determined the power supply quality of electric system to a great extent.The power supply reliability that improves power distribution network is to improve the important research content of power system power supply reliability.Traditional distribution network line adopts the radiation type electric supply mode more, and the take-off point place is without isolating switch and opertaing device, and the required time that restores electricity is long, has affected the reliability of power distribution network power supply.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 the important research content of intelligent grid as the basis of self-healing.
China's power distribution network adopts neutral point small current neutral grounding mode mostly, is subject to the impact of the factors such as neutral grounding mode, power distribution network scale, transition resistance, and the failure line selection problem is never satisfactorily resolved, and does not more know where to begin in the 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 singlephase earth fault occurs, short-circuit current is little, and the curent change that flows through fault and non-fault line is only the variation of capacitive earth current.Special when system neutral through grounding through arc, and while adopting the over-compensation mode to work, utilize the variation of power frequency amount to be difficult to distinguish faulty line and non-fault line.Therefore can only adopt transient 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 than steady-state value large several times to tens times.
Selection method sensitivity based on transient signal is higher and be not subject to the impact of arc suppression coil, but existing method is left to be desired mostly.Utilize the transient method existing, first half-wave method is based on singlephase earth fault and occurs in fault phase voltage and approach near this assumed condition maximal value, and when the phase voltage zero cross near fault, transient is faint, is difficult to meet the demands.Although, also there are some problems in the extraction fault-signal that wavelet analysis method can be more accurate, as too responsive to micro-variable as the method, poor anti jamming capability; When trouble spot, during through the great transition resistance eutral grounding, the method can not be carried out.Traveling wave method due to fault after wavefront be difficult to accurate seizure, and sample frequency requires high factor, is difficult to realize.Based on above all factors, can find out, the route selection problem of small current neutral grounding system is the problem of not resolving always, and section Position Research achievement is not more known where to begin, so research fault section location method will be brought to the intellectuality of power distribution network important realistic meaning.
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, the present invention has adopted following technical scheme:
This localization method comprises the following steps: by selected first capacitive frequency band, every circuit is simplified to capacitor model in zero-sequence network, under the Voltage Reference direction of appointment and current reference direction, utilize residual voltage and the zero-sequence current at route survey point place to solve capacitance, according to the positive and negative failure judgement point of described capacitance whether capacitance on the rear circuit of corresponding measurement point, thereby realize that the section of trouble spot locates.
If the capacitance corresponding with certain measurement point Tp, for negative, judges that trouble spot is on the circuit of the rear of measurement point Tp.
Described Voltage Reference direction be measurement point with respect to ground, the 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 1: after system generation singlephase earth fault, at the route survey point, place carries out synchronized sampling to residual voltage and zero-sequence current, and the residual voltage and the zero-sequence current that then by analog to digital converter, sampling are obtained are converted into digital quantity;
Step 2: described digital quantity is carried out to the bandpass filtering treatment that frequency band is 150Hz～600Hz, acquisition is corresponding to zero-sequence current component and the zero sequence voltage component of frequency band, ask for the derivative value of zero sequence voltage component by two point value differential formulas, then utilize zero-sequence current component with the ratio of described derivative value and identify corresponding capacitance in conjunction with least-squares algorithm;
Step 3: select apart from transformer station section farthest from capacitance is negative section, described apart from transformer station, section farthest is 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 of holding frequency range, by asking for the corresponding capacitance of capacitor model simplified by the circuit foundation as fault section location, the method principle is simple, be easy to realize, can quickly and reliably carry out fault section location, the method both can be used for the 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.
A kind of one-phase earthing failure in electric distribution network Section Location based on parameter identification is specifically described as follows:
During distribution generation singlephase earth fault, within head holds frequency range, the zero sequence model that perfects circuit and rear, trouble spot circuit can be equivalent to an electric capacity, between the derivative of its zero-sequence current and residual voltage, is now that a scale-up factor is positive direct proportion function; And, for faulty line, its zero sequence model consists of the circuit of system dorsal part, also can be equivalent to an electric capacity within head holds frequency range, but, under the designated reference direction, be negative proportion function for scale-up factor between its zero-sequence current and residual voltage derivative.
Referring to Fig. 1, it is isolated neutral or through grounding through arc that K switch is controlled neutral grounding mode, R
_{0x}, L
_{0x}, C
_{0x}be respectively circuit x resistance, inductance, capacitance parameter, i
_{0x}the zero-sequence current (x=1～n) that means circuit x.When trouble spot is positioned on i bar circuit, circuit the part on both sides, trouble spot each with model representation, wherein a R
_{0f}, L
_{0f}, C
_{0f}for circuit parameter between the place ahead, trouble spot and bus.U
_{0f}mean the equivalent residual voltage source at place, trouble spot, 3L means the inductance of arc suppression coil, R
_{f}transition resistance while meaning earth fault, i
_{0f}mean the zero-sequence current on circuit between trouble spot and bus, i
_{0i}the zero-sequence current that means rear, trouble spot circuit, i
_{l}mean the zero-sequence current on arc suppression coil, u
_{0}mean the residual voltage on bus.After the fault meaned by Fig. 1 occurs, the zero-sequence network of circuit can be reduced to simplified model as shown in Figure 2.
Referring to Fig. 2, C
_{the 0k ∑}(k=1～n) means that each perfects the zero sequence equivalent capacitance value of circuit and rear, faulty line trouble spot part, R
_{0f}, L
_{0f}, C
_{0f}for circuit parameter between the place ahead, trouble spot and bus, u
_{0f}mean the equivalent residual voltage source at place, trouble spot, 3L means the inductance of arc suppression coil, C
_{the oi ∑}the zero sequence equivalent capacitance value that means rear, trouble spot circuit.
Basis at simplified model can further be simplified, and referring to Fig. 3, the K switch open and close is corresponding isolated neutral and through grounding through arc respectively, R
_{0f}, L
_{0f}, C
_{0f}for circuit parameter between the place ahead, trouble spot and bus, C
_{h}for all total electric capacity that perfects the circuit equivalence, u
_{0f}mean the equivalent residual voltage source at place, trouble spot, 3L means 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)
_{the 0k ∑}for each perfects the zero sequence equivalent capacitance value of circuit or rear, faulty line trouble spot part.
Circuit for the place ahead, trouble spot has:
${i}_{0f}=-{C}_{0}^{\text{'}}\·\frac{{\mathrm{du}}_{0}}{\mathrm{dt}}---\left(2\right)$
C ' in formula (2)
_{0}zero sequence equivalent capacitance value for faulty component line fault point the place ahead part.
Therefore, the thought (source: Automation of Electric Systems, 2003,27 (9): 48-53), after system generation singlephase earth fault, can select the first frequency band that holds every circuit is simplified to a capacitor model in zero-sequence network that holds frequency range based on head.Utilize residual voltage, the zero-sequence current at route survey point place to solve capacitance.Judge actual whether breaking down on the circuit of corresponding measurement point rear according to the capacitance that obtains positive and negative, judges capacitance for bear and from bus (transformer station) farthest the person be place, trouble spot section, thereby realize that the section of trouble spot locates.
Concrete steps are as follows:
Step 1: the ground fault detection device that utilizes each line outlet and bifurcation to install, after system generation singlephase earth fault, at route survey point place, residual voltage, zero-sequence current are carried out to synchronized sampling to be scheduled to sampling rate, the residual voltage, the zero-sequence current that then by analog to digital converter, sampling are obtained are converted into digital quantity;
Step 2: the digital quantity obtained is carried out to bandpass filtering treatment, frequency band is 150Hz～600Hz, zero-sequence current component and the zero sequence voltage component of acquisition to this frequency band, zero sequence voltage component is now asked for to its derivative value by two point value differential formulas, then utilize least-squares algorithm to identify corresponding capacitance.
Step 3: the capacitance of identifying by step 2 positive and negative, carry out fault section location, the method for fault section location: be chosen distance transformer station distance section (being fault section) farthest negative section from the electric capacity identified.
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.) be provided with 1～6 trouble spot in emulation; position respectively section 1., 5., 7., 2., 3. with section 8., sector number (1.-9.) is as shown in Figure 4.For the sake of simplicity, it is example mutually that the singlephase earth fault of setting all be take A, and G means the equivalent source of distribution network systems, and L means the arc suppression coil inductance, and S1-S6 means respectively the load of 6 feeder terminals.
Isolated neutral distribution system section 1(faulty line) perfect circuit with section 2() get oscillogram that the data of 0.02s after fault are the sliding window draw calculation of 40 sampled points electric capacity through data window length as shown in Figure 5; Through the distribution system section 1(of grounding through arc faulty line) perfect circuit with section 2() get fault after the data of the 0.02s oscillogram that is the sliding window draw calculation of 40 sampled points electric capacity through data window length as shown in Figure 6.By Fig. 5, Fig. 6, can be found out, in the transient state situation, perfect the capacitance of line computation basicly stable on the occasion of, and fault wire has apparent in view fluctuation, but basicly stable be negative value, so just be easy to judge whether section is fault section.Emulated data by table 1-table 4 can further illustrate no matter be at arc suppression coil earthing system, or, in isolated neutral system, can utilize the positive and negative fault section location that carries out of identification equivalent capacity.
When table 1 is isolated neutral distribution system trouble spot generation Single Phase Metal ground connection, the capacitance that each section identification is calculated, 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 is calculated, 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 is calculated, 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 is calculated, 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)