CN103094888B - Matching method of complex distribution network over-current protection timing sequence based on novel directional element - Google Patents

Matching method of complex distribution network over-current protection timing sequence based on novel directional element Download PDF

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CN103094888B
CN103094888B CN201310006066.7A CN201310006066A CN103094888B CN 103094888 B CN103094888 B CN 103094888B CN 201310006066 A CN201310006066 A CN 201310006066A CN 103094888 B CN103094888 B CN 103094888B
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protective device
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overcurrent protection
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戴志辉
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North China Electric Power University
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Abstract

The invention relates to the technical field of power system relay protection, in particular to a matching method of a complex distribution network over-current protection time sequence based on a novel directional element. The technical scheme includes the following steps: the matching method is divided into two conditions that feed lines are inserted with no distributed power supply distribution generation (DG) and the feed lines are inserted with a distributed power supply DG. When the feed lines are inserted with no distributed power supply DG, the directional elements are not additionally installed on each protective device, and setting values of each over-current protection time are matched according to a positive direction. When the feed lines are inserted with distributed power supply DG, the directional elements are not additionally installed on the protective device which is in the downstream of the distributed power supply DG, and the setting values of each over-current protection time are matched according to the positive direction. By means of the matching method of the complex distribution network over-current protection timing sequence based on the novel directional element, the existing primary equipment is utilized in a maximum mode, new circuit breakers and voltage transformers are not needed to be increased, additional input of system topology and the like are not needed to be changed, the influence on the feed line over-current protection caused by the distributed power supply DG is overcome to some extent, and a good selectivity and a protective function are provided.

Description

Based on the complicated distribution overcurrent protection time cooperation method of novel directional element
Technical field
The invention belongs to Relay Protection Technology in Power System field, particularly a kind of complicated distribution overcurrent protection time cooperation method based on novel directional element.
Background technology
In current superhigh pressure, high-voltage fence, widely used direction component generally make use of the reliability of voltage and magnitude of current raising direction component simultaneously.Use the direction component of electric current and voltage at voltage transformer (Potential Transformer simultaneously; PT) can be ineffective in broken string situation; if a kind of direction component of the magnitude of current and other direction component of only utilizing can be formed to be coordinated to use, be beneficial to the ability that improves protective relaying device discriminating direction in various situation and improve the ability of relaying protection system reliability service further.
On the other hand; along with distributed power source (Distributed Generator; DG) power distribution network is accessed; distribution becomes multiterminal power supply even looped network from single ended power supply radiation network, and originally in distribution, the widely used current protection not with discriminating direction may owing to differentiating and malfunction by travel direction when reverse direction failure.Increasing direction component is one of approach overcoming this problem, but in current distribution network, protection for feed line also not exclusively configures PT, utilizes the direction component of voltage and the magnitude of current to need to install a large amount of PT additional to distribution simultaneously, adds investment undoubtedly.And only utilize the magnitude of current to form discriminating direction element in the accurately Judging fault direction of energy under the prerequisite of additional investment, for some problems of distribution network protection after solution distributed power source (DG) access, there is great advantage.
Existing large quantity research is from restriction DG allowed capacity, improvement DG protecting control means at present, and the aspects such as the improvement of protection fixed value adjusting, protection philosophy or logic, the research of new protection scheme are analyzed, but few for the effective countermeasure of protection time cooperation.The discriminant information of direction component matches with the action sequence of overcurrent protection by the present invention further; propose the overcurrent protection time cooperation method in band direction; do not need to increase any primary equipment; only need to increasing direction component and a time definite value in the existing protective device of part; DG can be overcome and access the impact brought to feeder line overcurrent protection, make overcurrent protection possess good backup protection function.In the occasion that operate time is very not strict, even can as the main protection of feeder line.
Summary of the invention
For above-mentioned problem, the present invention proposes a kind of complicated distribution overcurrent protection time cooperation method based on novel directional element.
Technical scheme of the present invention is, a kind of complicated distribution overcurrent protection time cooperation method based on novel directional element, is characterized in that, described method is divided into distribution-free formula power supply DG to access feeder line and has distributed power source DG to access feeder line two kinds of situations;
Wherein, when described distribution-free formula power supply DG accesses feeder line, each protective device does not all install direction component additional, and the overcurrent protection time definite value of each protective device coordinates according to positive direction;
Described have distributed power source DG access feeder line time, the protective device in distributed power source DG downstream does not install direction component additional, and the time definite value of its overcurrent protection coordinates according to positive direction;
Described have distributed power source DG access feeder line time, the protective device of distributed power source DG upstream installs direction component additional, and press the time definite value of the judged result determination overcurrent protection of direction component, namely direction component failure judgement position is positioned at positive direction or the opposite direction of protective device, when direction component failure judgement position is positioned at the positive direction of protective device, the time definite value of overcurrent protection coordinates according to positive direction; When direction component failure judgement position is positioned at the opposite direction of protective device, the time definite value of overcurrent protection is according to coordinating in the other direction;
Described distributed power source DG downstream is the circuit away from system side from distributed power source DG access point;
Described distributed power source DG upstream is the circuit close to system side from distributed power source DG access point;
Direction component failure judgement position is positioned at the positive direction of protective device or reciprocal foundation is following formula:
Above-mentioned two formulas failure judgement position when continuous three sampling periods all set up is positioned at the positive direction of protective device, otherwise failure judgement position is positioned at the opposite direction of protective device, wherein for positive sequence memory electric current, for the forward-order current that overcurrent protective device detects, I nfor the effective value of the rated current of protection place circuit, ε be less than 0 fixed gate threshold value;
The time definite value of overcurrent protection coordinates according to positive direction and refers to and to adjust according to classical ladder principle from line end;
The time definite value of overcurrent protection refers to in adjacent feeders top all overcurrent protection time definite value maximum time definite value as starting point according to coordinating in the other direction, from system side, carry out time fixed value adjusting to line end according to classical ladder principle;
Described classical ladder principle refers to when single-side power, and from the protective device farthest away from power supply, the closer to system side, the time of protection act is longer, and is increase progressively step by step.
Beneficial effect of the present invention be following some:
1. the direction component proposed, based on positive sequence memory electric current and positive sequence fault current, has good discriminating direction ability under various fault ' conditions.
2. make use of the magnitude of current, do not need additional configuration PT, be applicable to current protection for feed line, greatly save the investment of relevant primary equipment.
3. based on the complicated distribution overcurrent protection time cooperation method of novel directional element; make use of existing primary equipment substantially; do not need to increase new circuit breaker and voltage transformer, do not need to change the extra inputs such as system topological; fitting method possesses good selectivity; overcome DG to a certain extent and access the impact brought to feeder line overcurrent protection, possess good defencive function.
Accompanying drawing explanation
Fig. 1 is bilateral source system line chart.
The positive sequence network figure of system when Fig. 2 is positive and negative direction fault.
Vectogram when Fig. 3 is positive direction fault.
Vectogram when Fig. 4 is reverse direction failure.
Fig. 5 is distribution system topology.
Fig. 6 is overcurrent protection time cooperation figure.
Embodiment
Below in conjunction with accompanying drawing and specific embodiment, the present invention is elaborated.It is emphasized that following explanation is only exemplary, instead of in order to limit the scope of the invention and apply.
Complicated voltage levels electric power system is translated into double power-supply system by equivalence method and carries out relaying protection case study.For power distribution network, the access due to DG makes original single-side power radiation network become multi-power system even looped network, can be translated into the analysis that bilateral source system carries out relaying protection direction component equally by equivalent method.Therefore, the present invention is with the equivalent electric power system of typical double sided for analytical model, and the analysis carrying out remembering based on positive sequence the novel directional element of electric current and positive sequence fault current amount is set up.
As shown in Figure 1, be bilateral source system, wherein, Z sand Z s' be respectively A, B two equivalent impedance of side system; First with protective device 1 for research object, F 1, F 2for two fault points of protective device 1 positive and negative direction, during positive and negative direction fault, the positive sequence network of system as shown in Figure 2.Each parameter is as follows: A side system positive sequence equivalent impedance Z s=(0.254+J1.2) Ω, in the other direction short-circuit impedance Z sA=(1.26+j1.5) Ω, the positive sequence impedance Z of circuit AB aB=(0.616+j1.2) Ω, and on AB circuit, be uniformly distributed 4 short dots, wherein first short dot is F1 point.R f1, R f2for transition resistance.B side system equivalent impedance Z s '=(2.6+j6.5) Ω.Electric current positive direction is defined as points to circuit by bus, with be respectively the forward-order current (the present invention all carries out positive sequence calculating with A phase for special mutually) that protection A experiences with protection B.
When system is normally run, take A phase as forward-order current and the positive sequence memory electric current of special phase for:
Wherein, for both sides electromotive force of source or system equivalent electromotive force; When protecting A positive direction F1 point to break down, following equation group can be listed according to Fig. 2:
Can be tried to achieve by upper two formulas:
Make coefficient entry (Z in formula (4) s '+ Z f1B+ R f1)/R f1=α, the denominator of formula (4) is X and carries out abbreviation to obtain:
X = ( Z SA + Z S + Z AF 1 + R F 1 ) ( Z S ′ + R F 1 ) R F 1 - R F 1 =
(5)
( Z SA + Z S + Z AF 1 ) ( Z S ′ + Z F 1 B ) R F 1 + Z S ′ + Z S + Z AB + Z SA
As transition resistance R f1during → ∞, α E A · / X → E · A / ( Z S + Z SA + Z SA + Z S ′ ) , E · B / X → E · B / ( Z S + Z SA + Z AB + Z S ′ ) , This up-to-date style (4) is identical with formula (1), and namely positive sequence fault current phasor now and positive sequence are remembered electric current phasor and is tending towards same-phase, are now most disadvantageous in protection act.But along with the reduction of transition resistance, all can rotate clockwise, and the former amplitude is greater than the amplitude of the latter, the phase property of delayed memory electric current can be further obvious.
In conjunction with above-mentioned analysis, make phasor diagram as shown in Figure 3.Wherein β is the phase place absolute value of denominator term in formula (1).Along with transition resistance reduces gradually from infinity, γ ( delayed angle) and θ ( delayed angle) can increase gradually from 0.Therefore with relative phase as shown in the figure and by these two forward-order currents protecting A to record after can obtaining positive direction fault the relative position relation of electric current is remembered with positive sequence.
In like manner, during reverse direction failure, the forward-order current that can obtain overcurrent protection A is:
The denominator of formula (6) is made to be Y, (Z s+ R f2)/R f2=a, protects A forward-order current and memory current phase relation as shown in Figure 4 when can obtain reverse direction failure.
As transition resistance R f2during → ∞, namely positive sequence fault current phasor now and positive sequence are remembered electric current phasor and are tending towards same-phase, are most disadvantageous in protection act during the two same-phase.
Work as R f2when → 0, formula (6) becomes:
Be not difficult to analyze from phasor diagram, now obviously advanced
The analysis of comprehensive above-mentioned positive direction fault and reverse direction failure situation, the positive direction criterion of the direction component of electric current and fault current can be remembered based on positive sequence as follows:
Wherein, ε is a fixed gate threshold value being less than 0.By the choosing method of instance analysis threshold in example.
The erroneous judgement of direction component under no-load condition, Practical Criteria also will in conjunction with electric current threshold criterion, i.e. positive sequence memory electric current with fault forward-order current all be greater than a fixing threshold, its criterion is such as formula shown in (9).
Wherein I nfor the rated current effective value of protection place circuit.
Therefore, formula (8) should be used simultaneously, formula (9) criterion completes discriminating direction, during use, be benchmark with fault moment, compare the forward-order current phase place before and after fault.Above-mentioned two formulas failure judgement position when continuous three sampling periods all set up is positioned at the positive direction of protective device, otherwise failure judgement position is positioned at the opposite direction of protective device.The judgement of fault moment is identical with widely used method in current Microcomputer Protection, is mark as adopted starting element or measuring component action.
Do below modeling checking, still with protective device in system shown in Figure 11 for research object is verified.Consider following situation respectively, positive direction fault considers the short trouble of AB circuit 1/4,1/2 place and the various situation of line end, and often kind of a fault considers 50 Ω and 0.1 Ω transition resistance.Reverse direction failure is considered at F2 point respectively through the various short-circuit conditions of 50 Ω and 0.1 Ω transition resistance.
Sample frequency 1000Hz, adopt full-wave fourier algorithm calculating current fundametal compoment, take fault moment as reference point, utilizing the forward and backward each cycle sampled value of fault to calculate the phase difference of the forward and backward forward-order current component of fault, counting (phase angular unit is radian) in table 1 when calculating average phase after continuous 3 establishments (now time reference pushes away 3 sampling periods before should be fault moment) of direction criterion.
The phase place of the advanced positive sequence fault current of positive sequence memory electric current under the various failure condition of table 1.
Circuit positive direction 1/4 place Positive direction circuit mid point Line end In the other direction
50Ω 0.1Ω 50Ω 0.1Ω 50Ω 0.1 Ω 50Ω 0.1Ω
AB -0.026 -0.63 -0.03 -0.63 -0.03 -0.64 0.001 0.46
BC -0.025 -0.63 -0.029 -0.63 -0.03 -0.635 0.0011 0.405
CA -0.02 -0.61 -0.022 -0.62 -0.02 -0.61 0.0009 0.39
ABC -0.7 -0.7 -0.707 -0.707 -0.717 -0.717 0.911 0.911
Be not difficult to find out from table, the direction component that the present invention proposes clearly can distinguish the directional information under the various failure condition of 10kV system.Generally do not need during phase-to phase fault to consider large transition resistance; therefore for the present invention's application; in positive direction criterion, the value of ε can need the maximum transition resistance born to determine according to protection; bear as maximum the alternate transition resistance of 30 Ω be then chosen for-0.9 (now, in all phase-to phase faults the phase difference of criterion two phasors minimum be-0.96).Checkout result and the phase-to phase fault of alternate earth fault are close.
There is the direction component only needing the magnitude of current; the present invention further considers the time cooperation method of itself and overcurrent protection; propose when not increasing primary equipment; with the complicated distribution overcurrent protection time cooperation method based on novel directional element that the present invention proposes; for solving the sequential coordination question of the rear feeder line overcurrent protection of DG access, reliably excise fault selectively.
When having DG to access feeder line, the protective device in DG downstream does not install direction component additional, and the time definite value of its overcurrent protection coordinates according to positive direction; The protective device of DG upstream installs direction component additional, and presses the time definite value of the judged result determination overcurrent protection of direction component.Illustrate for system shown in Figure 5, the parameter of circuit AB, BC, AE, EF is all identical with circuit AB in Fig. 1, the same Fig. 1 of both sides system parameters.The overcurrent protective device 4,5,6 of feeder line AE, EF does not all install direction component additional, and protective device 3 does not also install direction component additional.Overcurrent protective device 1,2 installs direction component additional, and on AE circuit, different faults position is when different transition resistance fault, and overcurrent protective device 1 all can correctly be judged in the other direction.As AE circuit mid point occurs when the BC phase fault of 50 Ω transition resistances clearly be judged in the other direction.
When having distributed power source DG to access feeder line, the protective device of distributed power source DG upstream installs direction component additional, and press the time definite value of the judged result determination overcurrent protection of direction component, namely direction component failure judgement position is positioned at positive direction or the opposite direction of protective device, when direction component failure judgement position is positioned at the positive direction of protective device, the time definite value of overcurrent protection coordinates according to positive direction; When direction component failure judgement position is positioned at the opposite direction of protective device, the time definite value of overcurrent protection is according to coordinating in the other direction.
For system shown in Figure 5, the time cooperation relation of its overcurrent protection as shown in Figure 6.
Wherein, represent the overcurrent protection time definite value that on dead-end feeder, overcurrent protective device 6 coordinates by positive direction, suppose that its value is t; Δ t represents that the time is differential; represent that overcurrent protective device 1 is according to the time definite value coordinated in the other direction, for protective device 1, owing to being in DG upstream, has installed direction component additional, its by the time definite value of adjusting with ladder principle in the other direction should the time higher than the time definite value of protective device 4 differential.Protective device 2 has also installed direction component additional, and it then should be differential compared with the opposite direction time definite value of the protective device 1 high time by the time that opposite direction ladder principle is adjusted.
For avoiding specified time overcurrent protective device in fault point the closer to the deficiency that its operation time limit during power supply is longer; overcurrent protective device often adopts anti-time limit characteristic, and the principle that above-mentioned direction component is coordinated to use with inverse-time overcurrent protection operation time limit matching principle is same applicable.
After carrying out time cooperation by this principle, on the feeder line accessed without DG without any impact.And to the feeder line having DG to access, then, when not increasing the investment of the primary equipment such as circuit breaker, instrument transformer, overcurrent protective device still can be made to play and possess very well optionally backup protection and isolate DG with the effect of disengagement failure electric current.Be analyzed as follows:
1) feeder line AE breaks down, if protective device 4 place is configured with fast tripping protection and now tripping, then overcurrent protective device 4 can with the time limit the circuit breaker of action tripping AE circuit, if the overcurrent protection of protective device 4 also tripping, what now protective device 1 was experienced is in the other direction, then protective device 1 can with the time limit as the circuit breaker of " standby far away " tripping AB circuit, to isolate the short circuit current that DG provides.
2) when AB line failure, positive direction experienced by protective device 1, by the definite value tripping operation of positive direction time.If now DG is tripped by itself protection act, then protective device 2 can not action.If DG cannot trip, still provide short circuit current to short dot, then protective device 2 can experience reverse direction failure, and with the time limit the circuit breaker of action tripping circuit BC is with isolated fault.
3) during the fault of A-bus behind, on protective device 3,4,5,6 without impact; All experience reverse direction failure for protective device 1,2, protective device 1 can with the time limit the short circuit current that theres is provided of circuit breaker isolation DG of tripping AB circuit.
If can choose reasonable current limiting reactor fault current limiting, then the time delay of overcurrent protective device also can not cause too large impact to system.

Claims (4)

1. based on a complicated distribution overcurrent protection time cooperation method for novel directional element, it is characterized in that, described method is divided into distribution-free formula power supply DG to access feeder line and has distributed power source DG to access feeder line two kinds of situations;
Wherein, when described distribution-free formula power supply DG accesses feeder line, each protective device does not all install direction component additional, and the overcurrent protection time definite value of each protective device coordinates according to positive direction;
Described have distributed power source DG access feeder line time, the protective device in distributed power source DG downstream does not install direction component additional, and the time definite value of its overcurrent protection coordinates according to positive direction;
Described have distributed power source DG access feeder line time, the protective device of distributed power source DG upstream installs direction component additional, and press the time definite value of the judged result determination overcurrent protection of direction component, namely direction component failure judgement position is positioned at positive direction or the opposite direction of protective device, when direction component failure judgement position is positioned at the positive direction of protective device, the time definite value of overcurrent protection coordinates according to positive direction; When direction component failure judgement position is positioned at the opposite direction of protective device, the time definite value of overcurrent protection is according to coordinating in the other direction;
Described distributed power source DG downstream is the circuit away from system side from distributed power source DG access point;
Described distributed power source DG upstream is the circuit close to system side from distributed power source DG access point;
Described direction component failure judgement position is positioned at the positive direction of protective device or reciprocal foundation is following formula:
( arg ( I . 1 A / I . 1 | 0 | ) &Element; ( - &pi; , &pi; ) ) < &epsiv;
| I . 1 | 0 | | > 0.2 I n | I . 1 A | > 0.2 I n
Above-mentioned two formulas failure judgement position when continuous three sampling periods all set up is positioned at the positive direction of protective device, otherwise failure judgement position is positioned at the opposite direction of protective device, wherein for positive sequence memory electric current, for the forward-order current that overcurrent protective device detects, I nfor the effective value of the rated current of protection place circuit, ε be less than 0 fixed gate threshold value.
2. a kind of complicated distribution overcurrent protection time cooperation method based on novel directional element according to claim 1; it is characterized in that, the time definite value of overcurrent protection coordinates according to positive direction and refers to and to adjust according to classical ladder principle from line end.
3. a kind of complicated distribution overcurrent protection time cooperation method based on novel directional element according to claim 1; it is characterized in that; the time definite value of overcurrent protection refers to in adjacent feeders top all overcurrent protection time definite value maximum time definite value as starting point according to coordinating in the other direction, from system side, carry out time fixed value adjusting to line end according to classical ladder principle.
4. a kind of complicated distribution overcurrent protection time cooperation method based on novel directional element according to Claims 2 or 3; it is characterized in that; described classical ladder principle refers to when single-side power; from the protective device farthest away from power supply; the closer to system side; the time of protection act is longer, and is increase progressively step by step.
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