CN100371724C - Earth fault line-selecting method for arc suppression coil earthing system - Google Patents
Earth fault line-selecting method for arc suppression coil earthing system Download PDFInfo
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- CN100371724C CN100371724C CNB2005100204279A CN200510020427A CN100371724C CN 100371724 C CN100371724 C CN 100371724C CN B2005100204279 A CNB2005100204279 A CN B2005100204279A CN 200510020427 A CN200510020427 A CN 200510020427A CN 100371724 C CN100371724 C CN 100371724C
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Abstract
The present invention relates to a fault line selecting method of an arc suppression coil grounding system, which comprises the steps that three-phase voltage v<A>, v<B> and v<C> of a bus, zero sequence voltage v0 thereof and zero sequence currents of each feed line loop are detected synchronously in real time; voltage signals and current signals are processed by lower-pass filtration and sampling to obtain voltage values and current values; zero sequence voltage V'0 are processed by self-adapting sine filtration to obtain fundamental wave e0 as fault starting criterion in normal operation; if the criterion is true, instantaneous amplitude are computed, and whether a grounding fault occurs is further confirmed; when the fault is confirmed, zero sequence current values of each line and the bus are locked, instantaneous phases of the lines and the bus are computed, and phase changes of each feed line before and after the fault occurs are solved; when a certain phase change exceeds the critical value, the line is considered to have a grounding fault, and is indicated. The present invention effectively overcomes the problems that transient process of a zero-crossing fault disappears, the amplitude of zero sequence currents is too small and is easy to affect by physical parameters of different systems, etc., and obviously improves the probability of mischoice and leakage of selection in line selection.
Description
Technical field
The present invention is a kind of arc suppression coil earthing system ground connection road fault-line selecting method, and the choosing that is suitable for little electric current single-phase grounding fault circuit is declared, and belongs to technical field of power systems.
Background technology
China 3,6,10,35, the overwhelming majority of 66KV system are small current neutral grounding systems.When system's generation single-phase earthing, because earthing capacitance current is more much smaller than load current, and system line voltage still remains unchanged, so but uninterrupted power supply.But because the voltage of non-fault phase is upgraded to line voltage, regular long-play might cause insulation breakdown, thereby needs to determine fast faulty line.
In China 3 ~ 66kV power distribution network, extensively adopt not solidly grounded system (NUGS) of neutral point, be small grounding current system, it comprises isolated neutral system (NUS), neutral by arc extinction coil grounding system (NES) and neutral point resistance grounded system (NRS).When wherein singlephase earth fault took place for NUS and NRS, the capacitive character reactive power direction of faulty line and non-fault line was opposite, so the failure line selection criterion is very simple.
Owing to when single-phase earthing takes place NES,, make line selection apparatus lose the route selection effect in some cases because the inductive current of arc suppression coil has compensated unbalanced earth fault capacitance current.Independently small grounding current line selection apparatus has progressively been used in small current neutral grounding electric system in recent years.The achievement in research that obtains on single-phase earthing of small current earthing system protection research both at home and abroad mainly can be divided into five classifications: the incorporate selection method of the automatic compensation of steady-state component method, transient state component method, harmonic component method, earthing wire-selecting and arc suppression coil at present.But overall rice is seen, these methods can not be got rid of the influence of mutual inductor, identifying is subject to the influence of factors such as line length, system operation mode and transition resistance size, open and system in may have the situation of the capacitance current of certain bar circuit greater than other all line capacitance electric current sums, malfunction easily takes place in device.The transient state component method need occur in phase voltage near the performance of maximal value moment better in fault, but loses efficacy during ground connection near voltage over zero, and its directivity can only keep the extremely short time, and poor anti jamming capability is unfavorable for implementing in concrete engineering.
In sum, how seeking the small current earthing wire-selecting method that is suitable for the engineering application is a gordian technique, to solve the erroneous judgement and the problem of failing to judge in the earth fault line selection.
Summary of the invention
The object of the present invention is to provide a kind of earth fault line-selecting method for arc suppression coil earthing system, the comprehensive zero-sequence current that adopts busbar voltage and residual voltage and each feeder line, carry out route selection by instantaneous amplitude and the phase place of asking for corresponding parameter, can overcome the method for operation, position of failure point and other such environmental effects, special fault moment does not influence correct route selection yet when near zero-crossing point, thereby has obvious superiority.
In the NES system, when arc suppression coil earthing system was unearthed, system did not have residual voltage, did not have the zero sequence ground current on its arc suppression coil.In arc suppression coil earthing system ground connection moment, because electric current can not saltus step on the arc suppression coil, the faulty line zero sequence ground current of its ground connection moment flows to bus.Along with the increase of electric current on the arc suppression coil, faulty line zero sequence ground current is little by little reverse, transfers to and flows to circuit from flowing to bus.Utilize the change of this zero sequence transient power direction just can realize the earthing wire-selecting of arc suppression coil earthing system.
This route selection principle is not subjected to the influence of earth fault moment phase voltage initial value, no matter the instant of failure phase voltage is at the peak value place or at the zero passage place, the zero sequence transient power all can be changed into and flows to line direction from flowing to generatrix direction, and this is the ubiquity feature of an arc suppression coil earthing system when earth fault occurring.Need only the feature that captures power inverted orientation at instant of failure (about 0.5ms), just can determine this road feeder line whether earth fault takes place.Therefore, the difficult point of earth fault line selection is how to find the method for calculating feeder line phase change process quickly and accurately.
The inventive method is by busbar voltage and circuit zero-sequence current, adopts the sinusoidal instantaneous amplitude that calculates voltage and the instantaneous phase of circuit zero-sequence current of approaching, and obtains the feature of swinging to of faulty line zero sequence transient power, and as the earth fault line selection criterion; This method may further comprise the steps:
By voltage, current transformation, in real time, the three-phase voltage v of synchronous detection bus
A, v
B, v
CAnd residual voltage v
0Zero-sequence current i with each feeder assembly
1, i
2..., i
n
The phase-locked A/D sampling of low-pass filtering (101,107), frequency locking (102,108) that voltage signal and current signal pass through hardware respectively obtains magnitude of voltage and current value;
Residual voltage v '
0Residual voltage first-harmonic e when after adaptive sine filtering (105), normally being moved
0, be used as the criterion that adaptive failure starts (106);
If criterion is set up, then calculate instantaneous amplitude (103), and be used for further affirmation whether earth fault (104) takes place;
After earth fault is confirmed, latch the zero-sequence current value (109) of each circuit and bus immediately, calculate its instantaneous phase (φ
1, φ
2..., φ
n, φ
v) (110), and then ask for the variation of phase place before and after each feeder fault;
Carry out faulty line identification (111), after certain phase tranformation surpasses critical value, promptly think this circuit generation earth fault, and indicate.
This method advantage
This method adopts the sinusoidal approach method of momentary signal to ask for the instantaneous phase of each feeder assembly zero-sequence current on each sampled point after the fault, thereby accurate response goes out the paraphase feature of the zero sequence transient power direction in the singlephase earth fault, overcome effectively that the zero crossing fault transient process disappears, the zero-sequence current amplitude is too small and be subject to problem such as different system physical parameters impact, will significantly improve the probability of falsely dropping in the route selection and leaking choosing.
Description of drawings
The block diagram that Fig. 1 realizes for the inventive method;
Fig. 2 is the block diagram of fault initiating process in this method;
Fig. 3 is the block diagram of fault recognition process in this method;
Fig. 4 is the computation process block diagram of instantaneous amplitude and phase place in this method;
Fig. 5 is the example according to the line selection apparatus of this method formation.
Specific embodiments
Describe specific implementation process of the present invention in detail below in conjunction with Fig. 1:
1, real-time sampling bus three-phase voltage v
A, v
B, v
CAnd residual voltage v
0And each feeder assembly zero-sequence current i
1, i
2..., i
n, take the frequency locking phase-lock mode to guarantee the synchronous of bus residual voltage, bus three-phase voltage and the sampling of each feeder assembly zero-sequence current.
2, voltage signal and current signal pass through the low-pass filtering (101,107) of hardware respectively, and the high order frequency content in the filtering sampled signal guarantees through only staying the fundamental frequency composition of sampled signal after the low-pass filter processing; Obtain magnitude of voltage and current value through the phase-locked A/D sampling of frequency locking (102,108) again.
3, residual voltage v '
0Residual voltage first-harmonic e during the normal operation that after adaptive sine filtering (105), obtains
0, be used as the criterion that adaptive failure starts (106), judge whether to exist earth fault.Only work as the bus residual voltage and satisfy e
0(t)＞e
Set1And ∑ | e
0(t
j) |＜e
Set2During condition, think earth fault may take place, carry out fault initiating, referring to Fig. 2.Wherein, e
Set1, e
Set2The compare threshold that expression is set, e
0(t) the residual voltage value of expression t moment bus, ∑ | e
0(t
j) | represent the accumulated value of the residual voltage of a plurality of continuous buses;
If instantaneous amplitude (103) is then calculated in 4 startups of breaking down, and be used for further affirmation whether earth fault (104) takes place, referring to Fig. 3.The bus residual voltage is by sinusoidal approach method (401), continuous calculating parameter A (t), and B (t) is as error e (the t)＞e that satisfies condition
Min(t) after, can calculate the instantaneous amplitude of bus residual voltage according to (404), referring to Fig. 4; Fault recognition adopts the busbar voltage instantaneous amplitude to realize, if three-phase bus voltage satisfies condition | and v
A(t)+v
B(t)+v
C(t) |＞V
Set, and bus residual voltage instantaneous amplitude satisfies condition simultaneously | v
0(t)-v
0(t+ Δ t) |＞v
Set1With | v
0(t+ Δ t) |＞e
Set2, then confirm to take place earth fault.In the formula, V
Set, V
Set1, V
Set2All represent the setting voltage threshold value, Δ t represents delay time length;
5, after earth fault was confirmed, the zero-sequence current value of carrying out each circuit immediately latched (109), and the circuit zero-sequence current is equally by sinusoidal approach method (401), continuous calculating parameter A (t), and B (t) is as error e (the t)＞e that satisfies condition
Min(t) after, can calculate each feeder assembly zero-sequence current and the instantaneous phase (110) of bus residual voltage on each sampled point after the fault according to (405).Wherein, e (t) represents sinusoidal approximate error, e
Min(t) corresponding permissible error constantly.Referring to Fig. 4;
6,, compare the situation of change of phase place between zero-sequence current and the residual voltage according to the instantaneous phase of each feeder assembly zero-sequence current of asking for and the instantaneous phase of residual voltage.If the variation of 90～180 degree scopes takes place a certain feeder assembly zero-sequence current phase place, then this circuit is exactly an earth fault line;
7, indicate faulty line.
This method can adopt the formation line selection apparatus of DSP digital signal processing module etc., and its basic structure as shown in Figure 5.
After detected object busbar voltage (501), bus residual voltage (502), feeder line zero-sequence current (503)～(505) process filtering etc. are handled, deliver to DSP and carry out synchronized sampling (506).Behind the voltage data process software filtering (507), judge whether to carry out fault initiating.If then carry out fault recognition (509) by calculating instantaneous amplitude (508).Earth fault according to feeder line zero-sequence current that latchs and bus residual voltage, is calculated the instantaneous phase (510) of each sampled point after confirming.Faulty line is determined according to feeder line zero-sequence current phase change situation in route selection unit (511), the concurrent indication (512) of being out of order.
Claims (5)
1. arc suppression coil earthing system faulty line system of selection, it is characterized in that: this method is by busbar voltage and circuit zero-sequence current, adopt the sinusoidal instantaneous amplitude that calculates voltage and the instantaneous phase of circuit zero-sequence current of approaching, obtain the feature of swinging to of faulty line zero sequence transient power, and as the earth fault line selection criterion; This method may further comprise the steps:
By voltage, current transformation, in real time, the three-phase voltage v of synchronous detection bus
A, v
B, v
CAnd residual voltage v
0Zero-sequence current i with each feeder assembly
1, i
2..., i
n
The phase-locked A/D sampling of low-pass filtering (101,107), frequency locking (102,108) that voltage signal and current signal pass through hardware respectively obtains magnitude of voltage and current value;
Residual voltage v '
0Residual voltage first-harmonic e when after adaptive sine filtering (105), normally being moved
0, be used as the criterion that adaptive failure starts (106);
If criterion is set up, then calculate instantaneous amplitude (103), and be used for further affirmation whether earth fault (104) takes place;
After earth fault was confirmed, the zero-sequence current value of carrying out each circuit immediately latched (109), asked for the variation of each feeder fault front and back phase place, calculated its instantaneous phase (110);
Carry out faulty line identification (111), after certain phase tranformation surpasses critical value, promptly think this circuit generation earth fault, and indicate.
2. earth fault line-selecting method according to claim 1 is characterized in that: fault initiating adopts the bus residual voltage first-harmonic e that obtains through sampling (102), adaptive sine filtering (105)
0As start-up criterion; Only work as the bus residual voltage and satisfy e
0(t)＞e
Set1And ∑ | e
0(t
j) |＞e
Set2During condition, think earth fault may take place, wherein, e
Set1, e
Set2The compare threshold that expression is set, e
0(t) the residual voltage value of expression t moment bus, ∑ | e
0(t
j) | represent the accumulated value of the residual voltage of a plurality of continuous buses.
3. earth fault line-selecting method according to claim 1 is characterized in that: fault recognition adopts the busbar voltage instantaneous amplitude to realize, if three-phase bus voltage satisfies condition | and v
A(t)+v
B(t)+v
C(t) |＞Vset, and bus residual voltage instantaneous amplitude satisfies condition simultaneously | v
0(t)-v
0(t+ Δ t) |＞V
Set1With | v
0(t+ Δ t) |＞V
Set2, then confirm to take place earth fault.In the formula, V
Set, V
Set1, V
Set2All represent the setting voltage threshold value, Δ t represents delay time length.
4. earth fault line-selecting method according to claim 3, it is characterized in that: the bus residual voltage is by adaptive sine filtering (105), if break down startup (106), then by sinusoidal approach method (401), constantly calculate corrected parameter A (t), B (t) (403); As error e (the t)＞e that satisfies condition
Min(t) after (402), can calculate the instantaneous amplitude of bus residual voltage according to (404); The circuit zero-sequence current is by after the low-pass filtering (107), synchronized sampling (108), if confirm to have taken place earth fault (104), and then by sinusoidal approach method (401), continuous calculating parameter A (t), B (t) (403) is as error e (the t)＞e that satisfies condition
Min(t) after (402), can calculate the instantaneous phase of all circuit zero-sequence currents according to (405); Wherein, e (t) represents sinusoidal approximate error, e
Min(t) corresponding permissible error constantly.
5. earth fault line-selecting method according to claim 1 is characterized in that: with the bus residual voltage is reference, and 90～120 degree that the phase change of circuit zero-sequence current surpasses before and after the fault can be thought this circuit generation earth fault.
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| CNB2005100204279A CN100371724C (en) | 2005-02-26 | 2005-02-26 | Earth fault line-selecting method for arc suppression coil earthing system |
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| CNB2005100204279A CN100371724C (en) | 2005-02-26 | 2005-02-26 | Earth fault line-selecting method for arc suppression coil earthing system |
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| CN100371724C true CN100371724C (en) | 2008-02-27 |
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