A kind of distribution small current earthing wire-selecting method and wire selection systemTechnical field
The disclosure belongs to field of relay protection in power, in particular to a kind of distributed small current earthing wire-selecting method andWire selection system.
Background technique
Only there is provided background technical informations relevant to the disclosure for the statement of this part, it is not necessary to so constitute first skillArt.
Small current neutral grounding system includes isolated neutral system and neutral by arc extinction coil grounding system.According to inventorUnderstand, relay protection of power system is still without accurate, available distributed small current earthing wire-selecting method, existing low current at presentEarthing wire-selecting method and its system are all centralized, and the Little Current Ground Connection System of centralization needs handle to connect in same motherZero mould electric current of all routes in line segment all accesses same line-selected earthing device (earth protective device), in same bus section, busbar sectionPower supply line may up to more than 20 items, therefore, the lead-in of earth protective device need it is very much, in the bad peace in spatial positionRow, it is also inconvenient for the maintenance management of each earth protective device.
Summary of the invention
The disclosure to solve the above-mentioned problems, proposes a kind of distributed small current earthing wire-selecting method and wire selection system,The disclosure ensure that the position of lead-in convenient for arranging, facilitates the maintenance and management of earthing wire-selecting system.
According to some embodiments, the disclosure is adopted the following technical scheme that
A kind of distribution small current earthing wire-selecting method, distributed arrangement connects in each power supply line for connecting same busGround protective device, the earth protective device obtain each phase voltage of bus, the supply transformer for connecting bus electric current and byZero mould electric current of power supply line is protected, if bus residual voltage is greater than setting valve, executes following route selection step:
Judge that failure is separate；
Removal is by protection zero mould electric current i of power supply line0,iIn power current, remove all high of selected frequency SF or moreFrequency electric current obtains and goes power frequency to remove high frequency residual current i by protection zero mould of power supply line0,i,α；It removes in transformer fault phase currentPower current, remove all high-frequency currents of selected frequency SF or more, obtain transformer fault phase goes power frequency to go high frequency surplusAftercurrent ig,T,α；
Calculate it is each by protection zero mould of power supply line go power frequency to remove high frequency residual current i0,i,αEnergy in t1 and t2 periodIntegral Wi；The failure of calculating transformer mutually goes power frequency to remove high frequency residual current ig,T,αEnergy the period integral Wg,T,If there is route meets the following conditions simultaneously, then judge the route for faulty line；
Wi> Iset,7；
Iset,7、Iset,8、Iset,9Respectively setting valve；k4、k5It is proportionality coefficient.
It is limited as further, the time of t1 and t2 period being chosen for after protective device starts to full resettingIn preceding a period of time；
Or first hemiwave time section；
Or only include the transient current period；
Or only include the steady-state current period；
Or including transient current period and steady-state current period；
Or the combination of multistage interval time section.
As selectable embodiment, the earth protective device obtains the two-phase electricity of the supply transformer of connection busStream, when failure be mutually missing from it is separate when, failure phase goes power frequency that high frequency residual current is gone to go power frequency to remove height with known two-phaseThe opposite direction of the sum of frequency residual current replaces.
As selectable embodiment, the earth protective device obtains the phase electricity of the supply transformer of connection busStream, when failure be mutually missing from it is separate when, failure phase goes power frequency that high frequency residual current is gone to go power frequency to remove height with a known phaseThe opposite direction that frequency residual current multiplies two product replaces.
As selectable embodiment, the earth protective device obtains the three-phase electricity of the supply transformer of connection busStream or biphase current or a phase current.
A kind of distribution Little Current Ground Connection System, including power supply, transformer and multiple power supply lines, power supply is to transformationDevice power transmission, transformer give bus power transmission, and multiple power supply lines are all connected with same bus, transformer small current neutral grounding, each power supplyRoute is equipped with respective earth protective device, and the earth protective device carries out failure line selection according to above-mentioned selection method.
As selectable embodiment, the three-phase of transformer gives the correspondence phase power transmission of bus, each phase of transformer respectivelyThere is current transformer respectively, the secondary side current of each current transformer inputs the earth protective device of each power supply line respectively.
Compared with prior art, the disclosure has the beneficial effect that
(1) lead-in of every earth protective device of disclosure distribution Little Current Ground Connection System is less, convenientThe arrangement and spatial arrangement of device lead-in, device maintenance management are convenient.
(2) disclosure removes the power current in electric current, and removes all high-frequency currents of selected frequency SF or more, energyEnough reach precisely removal interference signal, and retains the purpose of useful information to greatest extent.
(3) waveform for going power frequency to remove high frequency residual current that the disclosure is constructed from electric current is more characteristic, utilizes oneEquidirectional similitude or opposite direction similitude to distinctive current waveform analyze faulty line, and judging result is more reliable,Sensitivity is very high.
Detailed description of the invention
The Figure of description for constituting a part of this disclosure is used to provide further understanding of the disclosure, and the disclosure is shownMeaning property embodiment and its explanation do not constitute the improper restriction to the disclosure for explaining the disclosure.
Fig. 1 is a kind of distributed Little Current Ground Connection System structural schematic diagram of embodiment；
Specific embodiment:
The disclosure is described further with embodiment with reference to the accompanying drawing.
It is noted that following detailed description is all illustrative, it is intended to provide further instruction to the disclosure.Unless anotherIt indicates, all technical and scientific terms used herein has usual with disclosure person of an ordinary skill in the technical fieldThe identical meanings of understanding.
It should be noted that term used herein above is merely to describe specific embodiment, and be not intended to restricted rootAccording to the illustrative embodiments of the disclosure.As used herein, unless the context clearly indicates otherwise, otherwise singularAlso it is intended to include plural form, additionally, it should be understood that, when in the present specification using term "comprising" and/or " packetInclude " when, indicate existing characteristics, step, operation, device, component and/or their combination.
Embodiment one:
A kind of exemplary embodiment, distributed Little Current Ground Connection System as shown in Figure 1.Power supply is sent to transformer TElectricity, transformer T give bus M power transmission, and transformer T neutral point is grounded through arc suppression coil L.Assuming that bus M is connected with N supply linesRoad, N=6.Six routes are L1, L2, L3, L4, L5, L6 respectively.Every route have respective earth protective device BH1,BH2, BH3, BH4, BH5, BH6, in order to draw conveniently, Fig. 1 only draws BH1.Current transformer TA1, TA2 of 6 power supply lines,The zero mould electric current i of TA3, TA4, TA5, TA60,i(i=1,2,3,4,5,6) inputs the earth protective device of each route respectivelyBH1, BH2, BH3, BH4, BH5, BH6, zero mould electric current i0,iReference direction and it is conventional be unanimously that bus is directed toward route.i0,iIt indicatesIt is instantaneous value,Expression is phasor.It is well known that the power frequency component of zero mould electric current is exactly zero-sequence current.Bus-bar potential transformerThe three-phase voltage of TVEarth protective device BH1, BH2, BH3, BH4, BH5, BH6 of each route are inputted respectively；A, B, C phase of transformer T respectively give bus M A, B, C phase power transmission, A, B, C phase of transformer T have respectively current transformer TAa,TAb,TAc.Current transformer TAa, TAb, TAc secondary side current input respectively each route earth protective device BH1, BH2,BH3,BH4,BH5,BH6.Current transformer TAa, TAb, TAc secondary side current reflect primary side current i respectivelya,T、ib,T、ic,T,Primary side current ia,T、ib,T、ic,TReference direction be bus be directed toward transformer.
The earth protective device of each route calculates separately bus residual voltageIf busResidual voltage is greater than setting valve, illustrates that ground fault occurs for electric system, the earth protective device of each route respectively starts to selectLine process.The route selection strategy and criterion of small current earthing wire-selecting, specifically:
(1) judge that failure is separate；Such as: Ua、Ub、UcIt is the smallest it is separate be failure phase；(2) zero mould electric current of this route is removedi0,iIn power current, remove all high-frequency currents of selected frequency SF or more, obtain zero mould of this route and power frequency is gone to go high frequency surplusAftercurrent i0,i,α；The power current in transformer T faulted phase current is removed, all high-frequency electricals of selected frequency SF or more are removedStream, obtain transformer T failure phase goes power frequency to remove high frequency residual current ig,T,α；Such as: a phase is failure phase, then has ig,T,α=ia,T,α(3) calculating zero mould of this route goes power frequency to remove high frequency residual current i0,i,αEnergy t1 and t2 period integral Wi, canWithIt calculates；Calculating transformer T failure mutually goes power frequency to remove high frequency residual current ig,T,αEnergy in t1 and when t2Between section integral Wg,T, can useIt calculates；(4) if Wi> Iset,7, andAndThen this routeIt is faulty line.
Wherein: 0≤t1, t1< t2< tset1；tset1It is the time after Interference Measures for Small Current Grounding Protection Equipment starts to full resetting.It is recommended that taking k4=0~0.5, k4=1~2；7th setting valve Iset,7, the 8th setting valve Iset,8, the 9th setting valve Iset,9It can be according to operationIt is empirically determined.
Certainly, in embodiments, electric current removal power frequency and the method for high-frequency current have very much, such as:
The method of zero mould electric current removal power current: (1) zero mould electric current passes through digital power frequency notch filter after A/D samplingIt obtains zero mould and removes power frequency residual current.(2) steady-state current for a frequency cycle for taking zero mould current temporary state current vanishes laterSample is made, carries out the conversion of power frequency fourier, converting expansion of the power current information of acquisition in the ground protection entire period is exactlyPower current.It is exactly that zero mould goes power frequency that the zero mould electric current, which all subtracts the power current expanded and come out in the ground protection entire period,Residual current.(3) steady-state current for a frequency cycle for taking zero mould current temporary state current vanishes later makees sample, which existsThe expansion of the entire working time section of ground protection is exactly power current.The zero mould electric current the entire working time section of ground protection allSubtracting the power current expanded and come out is exactly that zero mould removes power frequency residual current.Subsidiary effect is the idol having also been removed in zero mould electric currentSecondary higher harmonic components are exaggerated the higher harmonic components of the odd times in zero mould electric current.But not route selection judgement is generated notBenefit influences.(4) other methods.
The method of zero mould electric current removal high-frequency current: (1) zero mould electric current first passes through analogue low pass filtering before A/D samplingDevice (such as: capacitor).(2) zero mould electric currents pass through wave digital lowpass filter after A/D sampling.(3) other methods.
The working characteristics of lower surface analysis small current earthing wire-selecting criterion.
Whether before ground fault occurs for electric system, or later, all there is imbalance zero in each route of electric systemSequence electric current.Experience have shown that: uneven zero-sequence current is substantially power current.Small current earthing wire-selecting in high resistance earthing fault,It cannot be that fault-signal is very small and weak the main reason for correct route selection, the amplitude of out-of-balance current is already close to fault-signal size.The power current removal in zero mould electric current, and all high-frequency currents of selected frequency SF or more are removed, is gone with remaining zero mouldPower frequency goes high frequency residual current to make earthing wire-selecting criterion.In this way, not only precisely removing interference signal, but also retain useful letter to greatest extentNumber, it realizes and had not only eliminated main interference in zero mould electric current, but also highlight the useful fault-signal feature of zero mould electric current, it can be with weakGlitch signal judges the purpose of faulty line.
When ground fault occurs suddenly, the transient current amplitude of each zero mould electric current of route is greater than this route power frequency zero sequence electricityFlow amplitude several times or more than ten times；The transient current amplitude maximum of zero mould electric current of faulty line.In first hemiwave time, non-faulting lineThe equidirectional variation of transient current of zero mould electric current of road, the transient current of zero mould electric current of faulty line and the transient state electricity of non-fault lineFlow changing inversely.
A large amount of fault recorder datas show: ground fault, especially high resistance ground, the arc light resistance of grounding point occur for routeThe overwhelming majority is variation, and arcing ground can generate a large amount of high frequency attenuation electric currents, and arcing ground may be intermittently present.Such asFruit is quiet earth, zero mould go power frequency to remove high frequency residual current there are also quintuple harmonics and other higher hamonic waves.
Ground fault occurs for route, and zero mould of all non-fault lines goes power frequency that high frequency residual current is gone all to flow into from routeGreatly, and from the earth grounding point faulty line is flowed into, flows into failure phase bus from faulty line, then flow into and become from failure phase busDepressor failure phase coil, from the coil inflow transformer neutral point of transformer fault phase；Connect the arc blowout wire in transformer neutral pointCircle has very high reactance to transient current and its high-frequency current, and transformer coil only leaks transient current and its high-frequency currentIt is anti-, so, the another two-phase which goes power frequency to remove high frequency residual current from transformer neutral point inflow transformer non-faulting, then pressRatio flows into each route, and zero mould for forming each route goes power frequency to remove high frequency residual current.If zero mould goes power frequency to remove high frequencyThere is dc-decay electric current in residual current, then flows into the earth from neutral point arc suppression coil, and flow into faulty line from fault pointFailure phase.As it can be seen that transformer fault phase coil goes power frequency to remove high frequency residual current ig,T,αFault wire is flowed into equal to from fault pointZero mould of the failure phase on road goes power frequency to remove high frequency residual current.Zero mould of faulty line go power frequency go high frequency residual current be equal to fromZero mould that fault point flows into the failure phase of faulty line goes power frequency that high frequency residual current is gone to subtract this route and flows into the earth from routeZero mould go power frequency to go the difference of high frequency residual current.Therefore, if i-th line road is faulty line, transformer fault phasePower frequency is gone to remove high frequency residual current ig,T,αPower frequency is gone to remove high frequency residual current i with zero mould of faulty line0,i,αOpposite direction, and Wg,TGreater than Wi.If i-th line road is faulty line, haveAs it can be seen that if inequalityIt sets up, then the route is faulty line.
If i-th line road is not faulty line, haveAs it can be seen that inequalityIt will not set up, judge that the route is not faulty line.
Similarly, it is desirable that Wi> Iset,7, reliability is judged also for guarantee.If zero mould of route goes power frequency to go high frequency surplusAftercurrent i0,i,αEnergy it is too small, error is with regard to big, in fact it could happen that falsely drops line.It is therefore desirable to which zero mould of route goes power frequency to remove high frequencyResidual current i0,i,αEnergy be greater than the 7th setting valve.Further, power frequency can also be gone to remove high frequency residual current with zero mould of this routei0,i,αPeriod for concentrating of energy comparison define t1 and t2 period.Alternatively, going power frequency to go high frequency surplus with zero mould of this routeAftercurrent i0,i,αThe combination of multiple intermittent periods concentrated of energy comparison define t1 and t2 period.The periodSelection mode be in a period of time after protective device starting before time to full resetting；Or first hemiwave time section；Or only include the transient current period；Or only include the steady-state current period；Or including transient current period and steady-state currentPeriod；Or the combination of multistage interval time section.According to different actual motion power distribution network situations, the different time is chosenSection combination, flexible Application realize optimum efficiency.
Present widely applied transient method earthing wire-selecting only occurs in first hemiwave time in failure, more each zero mould of routeThe inceptive direction and amplitude size of the transient-wave of electric current.First hemiwave time is crossed, criterion just fails.The effective time of criterionSection is very short.The t of the present embodiment1With t2Long section can be taken.The present embodiment criterion algorithm may include meeting transient method ground connectionThe fault signature section of route selection can also include the fault signature section for not meeting transient method earthing wire-selecting.Criterion reliability withSensitivity is better than transient method selection method.
The main component of Three-Phase Transformer electric current is load current, and load current, which is far longer than in three-phase current, goes power frequencyRemove high frequency residual current.But the transformer fault as one of criterion mutually goes power frequency to go high frequency residual current when going power frequencyLoad current is eliminated, so, small current earthing wire-selecting criterion will not be interfered by load current.
Small current earthing wire-selecting criterion can be used in isolated neutral system, it is possible to use in neutral point through arc suppression coilEarthed system.
The lead-in of disclosure distribution earth protective device is less, and the arrangement of device lead-in and spatial position is facilitated to pacifyRow, device maintenance management are convenient.
A kind of grounding and line selection method for low current grounding system provided in this embodiment may be implemented completely.Before having wide applicationScape.
Embodiment two:
A, B, C phase of power distribution network as shown in Figure 1, transformer T have current transformer TAa, TAb, TAc respectively.Current Mutual InductanceDevice TAa, TAb, TAc reflect primary side current i respectivelya,T、ib,T、ic,T.But A, C phase of the transformer T of some power distribution networks is distinguishedThere is current transformer, B phase is without current transformer.
Live practical operating experiences show that ground fault, transformer neutral point arc suppression coil occur for small current neutral grounding systemAttenuating dc component very little, ignore on small current earthing wire-selecting criterion influence very little.So when B phase is failure phase,Enable transformer T failure phase goes power frequency to remove high frequency residual current ig,T,α=-(ia,T,α+ic,T,α), it still can use method of disclosureSelect faulty line.Only, sensitivity and reliability are slightly worse than embodiment one.The content being the same as example 1, herein no longerBurden.
Embodiment three:
A, B, C phase of power distribution network as shown in Figure 1, transformer T have current transformer TAa, TAb, TAc respectively.Current Mutual InductanceDevice TAa, TAb, TAc reflect primary side current i respectivelya,T、ib,T、ic,T.In order to be further reduced the introducing of earth protective deviceLine, earth protective device can only take a phase current, such as take A phase current.
It is not difficult to analyze, when B phase is failure phase, enable transformer T failure phase goes power frequency to remove high frequency residual current ig,T,α=-2ia,T,α, calculated, still can select faulty line with method of disclosure.When C phase is failure phase, transformer T failure is enabledPhase goes power frequency to remove high frequency residual current ig,T,α=-2ia,T,α, calculated, still can select fault wire with method of disclosureRoad.Only, sensitivity and reliability are slightly worse than embodiment one.The content being the same as example 1, it is no longer burdensome herein.
It should be understood by those skilled in the art that, embodiment of the disclosure can provide as method, system or computer programProduct.Therefore, complete hardware embodiment, complete software embodiment or reality combining software and hardware aspects can be used in the disclosureApply the form of example.Moreover, it wherein includes the computer of computer usable program code that the disclosure, which can be used in one or more,The computer program implemented in usable storage medium (including but not limited to magnetic disk storage, CD-ROM, optical memory etc.) producesThe form of product.
The disclosure is referring to method, the process of equipment (system) and computer program product according to the embodiment of the present disclosureFigure and/or block diagram describe.It should be understood that every one stream in flowchart and/or the block diagram can be realized by computer program instructionsThe combination of process and/or box in journey and/or box and flowchart and/or the block diagram.It can provide these computer programsInstruct the processor of general purpose computer, special purpose computer, Embedded Processor or other programmable data processing devices to produceA raw machine, so that being generated by the instruction that computer or the processor of other programmable data processing devices execute for realThe device for the function of being specified in present one or more flows of the flowchart and/or one or more blocks of the block diagram.
These computer program instructions, which may also be stored in, is able to guide computer or other programmable data processing devices with spyDetermine in the computer-readable memory that mode works, so that it includes referring to that instruction stored in the computer readable memory, which generates,Enable the manufacture of device, the command device realize in one box of one or more flows of the flowchart and/or block diagram orThe function of being specified in multiple boxes.
These computer program instructions also can be loaded onto a computer or other programmable data processing device, so that countingSeries of operation steps are executed on calculation machine or other programmable devices to generate computer implemented processing, thus in computer orThe instruction executed on other programmable devices is provided for realizing in one or more flows of the flowchart and/or block diagram oneThe step of function of being specified in a box or multiple boxes.
The foregoing is merely preferred embodiment of the present disclosure, are not limited to the disclosure, for the skill of this fieldFor art personnel, the disclosure can have various modifications and variations.It is all within the spirit and principle of the disclosure, it is made any to repairChange, equivalent replacement, improvement etc., should be included within the protection scope of the disclosure.
Although above-mentioned be described in conjunction with specific embodiment of the attached drawing to the disclosure, model not is protected to the disclosureThe limitation enclosed, those skilled in the art should understand that, on the basis of the technical solution of the disclosure, those skilled in the art are notNeed to make the creative labor the various modifications or changes that can be made still within the protection scope of the disclosure.