CN109490813A - A kind of current transformer characteristic appraisal procedure and system - Google Patents
A kind of current transformer characteristic appraisal procedure and system Download PDFInfo
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- CN109490813A CN109490813A CN201811486707.2A CN201811486707A CN109490813A CN 109490813 A CN109490813 A CN 109490813A CN 201811486707 A CN201811486707 A CN 201811486707A CN 109490813 A CN109490813 A CN 109490813A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R35/02—Testing or calibrating of apparatus covered by the other groups of this subclass of auxiliary devices, e.g. of instrument transformers according to prescribed transformation ratio, phase angle, or wattage rating
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Abstract
The invention discloses a kind of current transformer characteristic appraisal procedure and systems, comprising: the mathematical model for establishing description current transformer progress of disease performance obtains the steady-state characteristic energy and transient performance of current transformer；It obtains and flows through the fault current that differential protection respectively surveys mutual inductor under the conditions of different faults；It is inputted the simulation result of PSCAD as the primary side of current transformer, obtains the secondary side output electric current of current transformer；The Current Transformer Secondary side output actual design parameter of electric current combination current transformer is studied to the magnetic induction intensity and secondary side limit induced electromotive force situation of its iron core；The output result obtained to different inputs and different current transformer model emulations is saved respectively; and the input parameter as Microcomputer Protection; study influence of the current transformer Transfer characteristic to relay protection; the steady-state characteristic and transient characterisitics for considering current transformer simultaneously, study influence of the characteristic to protective relaying device of current transformer.
Description
Technical field
The present invention relates to power equipment measuring technology and evaluation areas, and in particular, to a kind of current transformer characteristic is commented
Estimate method and system.
Background technique
Current transformer is a kind of special transformer, is the most popular measuring device of electric system, is power plant
With the important electrical of transformer and distribution station.Divide from purposes and function, current transformer can be divided into Verification of Measuring Current Transformer and
Protective current transformer, two major classes.The former is mainly used for electric energy tariffing and monitoring and control under electric system normal operating condition
System measures the major parameter of its performance as the ratio difference and angular difference under rated frequency and rated current.The latter is mainly used for abnormal fortune
Signal is provided for relay protection device when capable and equipment fault, quickly and accurately to cut off faulty equipment as far as possible, reduces event
Hinder range；It is also possible to be used for fault monitoring and failure wave-recording.
The special application purpose of protective current transformer, determine measure its performance index cannot be only limitted to stable state and
Ratio difference and angular difference under rated condition, will more consider under fault condition under by attenuating dc component and major break down electric current synergy
Progress of disease performance.Existing current transformer characteristic assessment device use mostly standard current transformer, current lifting device, pressure regulator,
The testing equipment of current loading case, mutual-inductor tester, the achievement data of current transformer is obtained by in-site measurement, and operation is multiple
It is miscellaneous, and usually only it is conceived to the steady-state characteristic of current transformer, such as angular difference, measurement and analysis than difference index, and lack
Analysis to current transformer transient characterisitics.
It can thus be seen that improving the skill of protective relaying device to improve the measurement accuracy of protected level current transformer
Art ability is established TPY type mutual inductor mathematical model according to material object and is necessary.TPY type electric current can be carried out using model built
The research that instrument transformer transient characteristic influences breaker fail protection promotes the progress of protection technique ability, thus for optimization intelligence
It can transformer substation current transformer configuration scheme offer foundation.It will design intelligent substation is improved, play intelligent substation
Technical advantage, reduction intelligent station construction cost have direct significance.
Current transformer is that the operation for relay protection and electrometric important equipment in electric system, when being saturated is special
Property will make inject relay equipment electric current occur wave distortion, have to the safe and stable and economical operation of electric system important
It influences.At this stage other than lacking equipment fault analysis means, also it is short in understanding to the transient state Transfer characteristic of mutual inductor.From relay
The content of protection can be seen that in addition to reliability only has outside the Pass with the performance of protective device itself, other three kinds of characteristics (selections
Property, quick-action and sensitivity) it can all be influenced by mutual inductor progress of disease performance, therefore to the characteristic of mutual inductor, especially temporary
Transfer characteristic under the conditions of state carries out research and has important practical significance.By taking differential protection scheme as an example, Current Mutual Inductance is studied
Influence of the device error characteristics to differential relay acting characteristic, the malfunction of differential relay when solving external fault or operating normally
Problem is the key points and difficulties of differential protection research always.In order to guarantee the best performance of differential protection, generally requires and know difference
The error characteristics curve of dynamic protection, and correct relay protection constant value and acting characteristic curve are selected on this basis.However,
In different engineering practices, there is also many problems for the application of differential protection, specifically include that the out-of-balance current of 1, differential protection
Estimation is difficult: the out-of-balance current of differential circuit is to improve differential protection performance when accurate estimation normal operation and external fault
Premise and basis.The error characteristics and each current transformer for often neither considering current transformer monomer in engineering practice pass
The difference for becoming characteristic, does not consider the current transformer quantity that the actual fault characteristic of system and differential circuit are related to yet, but
Change of unbalance current rule is constructed according to engineering experience, and this result is used for the fixed value adjusting of differential protection, what is obtained is dynamic
It is neither scientific to make characteristic, it is also unreliable.2, differential protection error curve choose it is unreasonable: strictly speaking, when differential circuit not
When known to the change curve of balanced balanced current, the error curve of differential protection should become with the variation that stalling current defines
Change.But in engineering practice, the design of relay protection and operations staff often think that error curve is constant.3, differential
The formulation of protection act characteristic lacks foundation: the sensitivity in order to improve differential protection, general to require before meeting selectivity
Put makes the acting characteristic of differential protection close to error curve as far as possible.In engineering practice, different manufacturers often use different
Acting characteristic curve, such as the nonlinear curve of dual slope, tri linear and Cubic Spline Functions Fitting.But in error song
Under the premise of line is unknown, the operating status whether which can accurately match equipment can not judge.With with
Extra-high voltage is gradually forming for the bulk power grid of backbone, and main transformer investment capacity will reach 3000MVA, and excitation surge current will be increasingly
Greatly.Due to the limitation of equipment manufacturing technology, there is also bigger in practical projects for existing excitation surge current suppressing method
Defect.
Summary of the invention
The present invention propose the appraisal procedure that a kind of TPY type current transformer transient characterisitics influence breaker fail protection and
System, it is intended to solve the execute-in-place complexity of estimated current mutual inductor characteristic evaluation and usually only be conceived to the steady of current transformer
Step response and lack the problem of analysis to current transformer transient characterisitics.This method considers that the stable state of current transformer is special simultaneously
Property and transient characterisitics pass through the means of Digital Simulation in conjunction with different manufacturers, the protection philosophy of different product, study Current Mutual Inductance
Influence of the characteristic of device to protective relaying device.
Execute-in-place in order to solve estimated current mutual inductor characteristic evaluation is complicated and is usually only conceived to current transformer
Steady-state characteristic and lack the problem of analysis to current transformer transient characterisitics, propose a kind of TPY type current transformer transient state
The appraisal procedure that characteristic influences breaker fail protection.Magnetization characteristic of this method according to current transformer is considering that it is steady
In the case where step response, transient characterisitics, theory deduction goes out the mathematical model of current transformer；And it is built by way of Digital Simulation
A set of assessment system is found, in conjunction with current transformer and corresponding fault parameter, is considering that different manufacturers and different product principle are poor
In the case where different, the accurate influence for assessing current transformer characteristic to breaker fail protection.
It is compared according to experiment institute's measured data and emulation data, the magnetization characteristic of current transformer is coincide substantially, it was demonstrated that
This method can accurately simulate the operation characteristic of current transformer under various operating conditions, to assessment current transformer transient characterisitics pair
The influence of breaker fail protection has very important engineering practical value.
The research that TPY type current transformer transient characterisitics influence breaker fail protection can be carried out using model built,
The progress for promoting protection technique ability, to provide foundation for Intelligent Optimal transformer substation current transformer configuration scheme.It will
There is direct significance to improving intelligent substation design, performance intelligent substation technical advantage, reducing intelligent station construction cost.
The invention proposes a kind of assessment sides that TPY type current transformer transient characterisitics influence breaker fail protection
Method, which comprises
Based on current transformer mathematical model, the steady-state characteristic energy and transient performance of current transformer are obtained, wherein electric current
Mutual inductor mathematical model includes: current transformer steady-state model and current transformer transient Model；
Analogue system based on protected object, obtain different faults under the conditions of flow through the event that differential protection respectively surveys mutual inductor
Hinder electric current；
It is inputted the simulation result of PSCAD as the primary side of current transformer, show that the secondary side of current transformer is defeated
Electric current out；The Current Transformer Secondary side output actual design parameter of electric current combination current transformer is studied to the magnetic strength of its iron core
Answer intensity and secondary side limit induced electromotive force situation；Different inputs and different current transformer model emulations will be obtained defeated
Result saves respectively out, and the input parameter as Microcomputer Protection, shadow of the research current transformer Transfer characteristic to relay protection
It rings.
Further, the method also includes:
The electric parameter of measurement description current transformer Transfer characteristic, including secondary winding resistance, secondary winding leakage reactance, change
Than measurement, polarity check, excitation loss resistance, magnetization curve, remanence coefficient, secondary time constant, secondary load impedence and resistance
Anti- angle；
The parameter measured using gain of parameter module establishes the mathematical model for describing corresponding current transformer progress of disease performance.
In the application method preferably be carried out process the following steps are included:
Step 1 measures the electric parameter of description current transformer Transfer characteristic using special test equipment, including secondary
Winding resistance, secondary winding leakage reactance, no-load voltage ratio measurement, polarity check, excitation loss resistance, magnetization curve, remanence coefficient, it is secondary when
Between constant, secondary load impedence and impedance angle；
Step 2 establishes the mathematical model for describing corresponding current transformer progress of disease performance using the measurement parameter of step 1；
Step 3, the current transformer mathematical model established according to step 2, obtains current transformer by indirect method
Basic steady-state characteristic；
Step 4 establishes the analogue system of protected object using PSCAD, obtains and flows through differential guarantor under the conditions of different faults
Protect each fault current for surveying mutual inductor.Analogue system should be able to truly describe system condition locating for protected object, quilt substantially
Electric parameter and abort situation and condition (resistive short or metallic short circuit) of protected object itself etc., it is different in the hope of simulation
The distribution situation of differential protection out-of-balance current under fault condition；
Step 5, using the file importing of simulation software or opening function, using the simulation result of PSCAD as Current Mutual Inductance
The primary side of device inputs, and obtains the secondary side output electric current of current transformer.The current transformer unknown for system condition passes
Become the research of characteristic, system condition input function is set, the basic of description current transformer primary current is manually entered by user
Parameter: the virtual value of metastability exchange electric current, fault initial angle and primary system time constant.According to above-mentioned parameter, internal processes
Automatically the mathematic(al) representation of description primary current is provided, and discretization is carried out to the formula according to certain sampling interval, is then made
For input and current transformer mathematical model interface, system operational flow diagram is as shown in Figure 1；
The Current Transformer Secondary side output actual design parameter of electric current combination current transformer is studied its iron by step 6
Situations such as magnetic induction intensity and secondary side limit induced electromotive force of the heart；
Step 7 will protect respectively the output of system obtained from different inputs and different current transformer model emulations result
It deposits, in this, as the input parameter of Microcomputer Protection, and combines the protection philosophy of different manufacturers, different product, study Current Mutual Inductance
Influence of the device Transfer characteristic to relay protection: it both needs to consider difference existing for protection philosophy, it is also desirable to consider that protection is calculated
The influence of method and realization rate to assessment result.
Assessment system block diagram is as shown in Figure 2.
Further, the method for evaluating characteristic step 2 of the current transformer includes:
The first step, establishes steady-state model, and step includes:
Step 1, the electric parameter of special test equipment and test method measurement description current transformer Transfer characteristic is utilized:
(1), the survey of secondary winding in current transformer resistance and secondary circuit time constant is completed using DC test
Amount, calculates the secondary winding resistance of current transformer using the electric current and voltage that measure, secondary circuit discharge current byIt obtains, Least Square in Processing can be used to sampled point in recording waveform, required amount is fitted, to obtain
Secondary winding resistance RctWith the time constant T of secondary circuit20；
(2), the excitation resistance measurement of current transformer, magnetization curve measurement, no-load voltage ratio survey are completed using exchange no-load test
Examination, polarity verification and remanence coefficient measurement:
1) according to the sampled value in voltage and current a cycle, what the active power and winding resistance for calculating consumption consumed
Active loss, to obtain the active loss of excitation resistance consumption.Induced potential virtual value is calculated according to circuit, finally according to public affairs
FormulaObtain excitation resistance.EmIt is excitation potential, PmFor active power.
2) current transformer induced electromotive force is obtained according to circuit, Faraday's law of induction formula both sides is integrated simultaneously
To iron core magnetic linkage；By formulaObtain excitation current.Current transformer is established using magnetic linkage and excitation current
Magnetization curve.Due to the finiteness of test point quantity, it is bent that satisfactory magnetization should be fitted according to the principle of least square
Line.
(3), the recording of multiple frequency test points is tested using secondary load as a result, calculating separately out each test frequency condition
Then the impedance of lower secondary load and impedance angle are picked out according to load impedance with the variation relation of frequency electric in secondary load
It hinders, the size of inductance and distribution capacity.
Step 2, according to transformer working principle, as shown in figure 3, working as primary currentFlowing through mutual inductor the number of turns is N1One
When secondary winding, a magnetic potential will be establishedSimilarly, secondary currentWith secondary winding the number of turns N2Product constitute secondary magnetic potentialThe phasor of magnetic potential and secondary magnetic potential and as excitation magnetic potential, obtain magnetic potential balance equation:After converting secondary side, according to the secondary electric potential balancing equation of current transformerObtain the relationship of first winding end voltage and secondary impedanceMagnetic potential and electric potential balancing equation constitute the steady-state model of current transformer.
Second step, establishes transient Model, and acquiring method includes:
Step 1, transient process primary current models: when short trouble occurs for electric system, current transformer passes through short circuit
Electric current, if short-circuit network impedance angle φK=pi/2, running current is zero before short circuit, then calculates with primary current i1By sinusoidal cycles
Component is formed with the aperiodic component exponentially decayed, it may be assumed that
Step 2, exciting current models in transient process: formula 1, the i.e. loop equation of equivalent circuit can be written by Fig. 1:
Transient exciting current can be obtained by solving the differential equation, then is brought transient state primary current into and can be acquired transient state secondary current.
Step 3, electromagnetic coupling models in transient process: using minimum two at method high-precision analog TPY in the form of power function
Magnetic saturation characteristic, be based ultimately upon the accurate size that quadravalence discrete type runge kutta method accurately solves magnetic linkage, TPY type studied with this
Mathematical relationship between current transformer exciting current, former secondary current and magnetic flux and magnetic linkage.
Final functional relation can be obtained based on above three step is indicated by formula 2:
Step 4, the Transfer characteristic variation under high remanent magnetism or D.C. magnetic biasing environment:
When ground fault occurs for system, short-circuit current i that TPY first winding flows through1ForIRFor the DC current under remanent magnetism conversion.If TPY magnetic flux isThere is TPY
Secondary time constant: T2=Le/Rb.By primary current conversion to secondary side current i'1Are as follows: i'1=i1/Kn, KnFor the specified of TPY
Electric current ratio.The differential equation of TPY hasIt solves the differential equation and simultaneously brings initial value into, under the influence of can be obtained remanent magnetism
Magnetic flux size.The leakage reactance and core loss for disregarding secondary winding in current transformer have in TPY unsaturation
Substitute into primary current can abbreviation acquire exciting current size under the influence of remanent magnetism
Further, the transient state and steady-state performance of current transformer obtain in the current transformer characteristic appraisal procedure step 3
The method is taken to include:
Step 1, since field condition is extremely complex, it is necessary to according to aforementioned test data and according to domestic existing for assessment system
Capable current transformer standard infers its nameplate parameter:
(1) current transformer primary current rated value is inferred by testing resulting no-load voltage ratio, common are 1A 5A specification
Current transformer.
(2) judgement of CT type: according to the test result of aforementioned open-circuit test, judge the type of tested CT.With same change
The protection CT of ratio is compared, and the overload magnification or accurate limitation ratio that measurement CT allows are generally lower, and error is larger, general big
In 10%.
(3) nominal load is inferred: according to the test result of aforementioned secondary load loop test, judging that current transformer may
Rated output standard value.Basic step is exactly to pass through calculating or measurement when input current is the specified electricity of Current Transformer Secondary
When stream, test frequency are power frequency, the apparent energy in second trial circuit.Then, consider secondary winding in current transformer load
It influences, the test result of apparent energy is modified.
(4) deduction of accurate limitation ratio: according to the inferred results of nominal load, and the quadratic limit that reference test obtains
The measured value of voltage infers the possible accurate limitation ratio of current transformer.Carry out need and volume when the deduction of accurate limitation ratio
Fixed load infers that alternating iteration carries out, and strives keeping the deviation of inferred results deviation nominal load and accurate limitation ratio overall most
It is small.
Step 2, infer the steady-state performance of current transformer:
(1) basic step calculated than difference and angular difference: according to the loading condition of setting, total resistance in secondary load circuit is calculated
Anti- and each component value；The electric current of rated current percentage is inputted from the primary side of current transformer and is converted to secondary side；Before calculating
Current Transformer Secondary electric current under the conditions of two；According to final secondary current data and primary current data, calculating current
The ratio difference and angular difference of mutual inductor；The percentage for changing primary current, re-executes second and the 4th step, until reaching regulation
Rated current percentage；Change the load impedance of secondary circuit, returns to first step, re-execute the steps the 2nd~4
Step, until terminating.
(2) combination misalignment: for each test point, when exciting current stable state waveform determine after, need according toThe combination misalignment of calculating current mutual inductor.
(3) reflection of V-A characteristic is current transformer under the premise of primary side open circuit, secondary port voltage and secondary excitation
Relationship between electric current root-mean-square valve.Carrying out processing to the data in exchange no-load test can be obtained by the V- of current transformer
A characteristic curve.For each test point, to the sampled data of voltage, electric current, need to calculate separately its side according to the following formula
Equal root:
The conitnuous forms that V-A curve is obtained by the way of curve matching are generally required in practice.Matched curve is general
Be selected as polynomial curve, highest number be should be for 5 times it is enough, the principle of fitting is exactly least square method.
(4) 10% error characteristics curves: the precondition of calculating is the monodrome magnetization curve and excitation electricity of current transformer
Resistance with induced potential change curve oneself know.
1) load characteristic: namely load impedance angle is set, representative value is 0 ° and 37 ° desirable, can also be manually entered other
Value.
2) input current of obtaining current mutual inductor is 2 times of rated current, which is accurate under current design conditions
It is big to calculate allowable load impedance for limit value coefficient under the conditions of the task of next step is exactly known to the excitation characteristic and error limit
Small (impedance angle uses assumed condition).
3) size of secondary load impedence is tentatively set.
4) secondary current under the conditions of (1)~(3) is calculated.
5) combination misalignment of the current transformer under above-mentioned condition is calculated；
6) according to calculated result, the size of secondary load impedence is corrected: if combination misalignment is greater than 10%, secondary load
Impedance value reduces certain numerical value；If combination misalignment, less than 10%, secondary load impedence increases certain numerical value.
7) (4)~(6) are re-execute the steps, until convergence；
8) size or overcurrent multiple for changing input current, recalculate step (3)~(7).Last cycle calculations
Secondary load impedence can be used as the initial value of circulation secondary load impedance next time (according to this computation overload multiple and last computation
The relationship of overload magnification uses after carrying out inverse proportion amendment).
Step 3, infer the transient performance of current transformer:
(1) extraction of system failure parameters: these parameters generally require power supply department offer, but in most cases all without
Method is directly accurately known, needs to calculate rule of thumb or from other parameters:
1) short circuit current IpacBy formulaCalculating is got；
2) the time constant T of primary system1It is determined by the ratio between the inductance of the short circuit branch and resistance, i.e.,
3) short-circuit initial angle: statistical result shows that short trouble readily occurs near peak value, has 95% failure often
Occur within 40 ° before voltage peak.Therefore, it is that comparison is reasonable that the initial angle of short trouble, which is thought of as 50 °,.
4) short-circuit impedance angle φ is by formulaIt determines；
5) working cycles and elapsed-time standards of current transformer: the working cycles of current transformer can be divided into single cycle (C-
TI- O) and Two-way Cycle (C-TI-O-Tfr-C-T2- O) two classes.The former is suitable for general failure process, and the latter, which corresponds to, has list
The failure process of secondary reclosing.Intermediate T1And T2The actuation time of protective relaying device is represented, most of equipment is fast at present
For the sum of intrinsic opening time of fast operating time of protection and breaker generally within 40ms~100ms, this is also that failure may
Lasting maximum duration.TfrThe main blocking time for considering reclosing, most systems are maintained at 500ms or so.For superelevation
For pressure system, due to needing to consider the influence of secondary arc current, the blocking time of reclosing is about in 800ms or so.
(2) transient characterisitics simulation calculation: this process is exactly to meet the fault current of system features as input quantity, with test
The output parameter of equipment is model parameter, by solving the differential equation, obtains the circuit and magnetic circuit of description current transformer state
Parameter, comprising: exciting current i0(t), electric current i is exporteds(t), iron core magnetic linkage ψm(t) and secondary side induced electromotive force em(t).?
On the basis of this, it can be deduced that the magnetic induction density B (t) and these parameters of magnetic field strength H (t) of current transformer.
Further, operating condition is simulated in the current transformer characteristic appraisal procedure step 4 includes:
Increase line current under non-failure conditions, is more under the Transfer characteristic of current transformer and fault condition under fault condition
The Transfer characteristic of current transformer after secondary reclosing.Fault condition contains all failure classes common in route operational process
Type.The output of system obtained from different inputs and different current transformer model emulations result will be saved respectively, in this, as
The input parameter of Microcomputer Protection, and the protection philosophy of different manufacturers, different product is combined, study current transformer Transfer characteristic pair
The influence of relay protection.
Further, the approximating method of magnetization curve includes: in the current transformer characteristic appraisal procedure step 5
Using the Polynomial expression of power function approximating method of odd-times widely applied in engineering.Magnetization characteristic is fitted process as schemed
Shown in 4.
It can specifically indicate are as follows: i0=k1Ψ+k2Ψ3+k3Ψ5.COEFFICIENT K in above formula is solved using least square method1、K2、
K3.Y=f (Ψ)=i to be found a function is determined first0=k1Ψ+k2Ψ3+k3Ψ5, magnetization curve is enable most preferably to be fitted experiment
Observe data (Ii,Ui) (i=1,2 ... ... N), i.e., so that formulaObtain minimum value.Write as matrix form
Have:
I=[I1 I2 … IN]T (5)
K=[K1 K2 K3]T (6)
Objective function are as follows:
minδ2=(I-GK)T(I-GK) (8)
K is that the sufficient and necessary condition of least square solution is to meet normal equation group:
GTGK=GTI (9)
Due to f (Ψ)=i0=k1Ψ+k2Ψ3+k3Ψ5, basic function f1(Ψ)=Ψ, f2(Ψ)=Ψ3, f3(Ψ)=Ψ5,
Therefore available:
K can be acquired by above formula1、k2、k3Value, and fitting magnetization curve is acquired by fitting function.
Further, in the current transformer characteristic appraisal procedure step 5 magnetic linkage differential equation method for solving packet
It includes:
Flux linkage equations are nonlinear equations, wherein containing exponential function and trigonometric function, can not find out the display of the equation
Solution, it is therefore necessary to be solved using the principle that numerical value calculates.In order to improve computational accuracy, the discrete Runge Kutta of 4 ranks will be used
Method is solved.To the differential equationGeneral solution may be expressed as: Yn+1=Yn+h×D(tn,Yn).Wherein D
(tn,Yn) be a little in (tn,tn+1) in average speed.If YnIt is accurately, then to have:
So obtaining:
Due to right function higher derivative or can not directly obtain or calculate too complex, actual way is: use
[tn,tn+1] in section the linear combination of some known point functional values of solution curve neighborhood replace the derivative of F (t, Y), thus
To the single step method formula of high-order.
The differential equation can be obtained by bringing equation into this method are as follows:
Solve the above-mentioned differential equation:
The part can acquire the solution of magnetic linkage Ψ using programming.The fitting expression that the solution of magnetic linkage brings magnetic linkage into can be asked
The i of exciting current out0, then bring result into equation 1 and can find out secondary side current size.
Further, in the current transformer characteristic appraisal procedure step 6 remanent magnetism reduced current translation method packet
It includes:
The frequency range of remanent magnetism reduced current in 0.001~0.1Hz, numerical value up to peaces (A) up to a hundred, for reflect its amplitude and
The time variation and frequecy characteristic in direction, approximation simulate remanent magnetism reduced current with macrocyclic cosine function.Since remanent magnetism is converted
The time scale of curent change is much larger than the time scale of power current variation, i.e., can be by remanent magnetism reduced current in power frequency period
It is regarded as collimation stream.
Further, the current transformer magnetization curve related data is needed according to " electric current is used in GB16847-1997 protection
The transformer transient characteristic requirements " in illustrate to be obtained about what iron core excitation characteristic determined.Test uses alternating current method, two
Applying practical sinusoidal wave alternating voltage on secondary terminal, measures corresponding exciting current, test can carry out under reduced frequency,
Unacceptable voltage is born to avoid winding and secondary terminals.It applies alive virtual value on record secondary terminals and accordingly encourages
Magnetoelectricity stream i0Virtual value.Secondary linkage flux value Ψ can press formula by the alive root-mean-square valve U' of actual measurement institute under frequency f'It obtains, exciting current i can be obtained in this way0Corresponding relationship between magnetic linkage Ψ one by one.
Further, the current transformer characteristic appraisal procedure is packaged into assessment system, entire estimation flow such as Fig. 5 institute
Show.
Present invention also provides a kind of current transformer characteristic assessment system, the system comprises:
First obtain module, for be based on current transformer mathematical model, obtain current transformer steady-state characteristic can and
Transient performance, wherein current transformer mathematical model includes: current transformer steady-state model and current transformer transient Model；
Second obtains module, for the analogue system based on protected object, flows through under the conditions of acquisition different faults differential
Protect each fault current for surveying mutual inductor；
Evaluation module obtains Current Mutual Inductance for inputting the simulation result of PSCAD as the primary side of current transformer
The secondary side of device exports electric current；By the actual design parameter research of Current Transformer Secondary side output electric current combination current transformer
The magnetic induction intensity and secondary side limit induced electromotive force situation of its iron core；It will be to different inputs and different current transformer models
Emulate input parameter of the obtained output result as Microcomputer Protection, shadow of the research current transformer Transfer characteristic to relay protection
It rings.
Wherein, step 6 and step 7 need to carry out relay protection assessment, phase to current transformer in aforementioned execution process
Ying Di, the preferred embodiment of the system of the invention further include:
Basic parameter setup module: related with the evaluated power equipment differential protection input parameter of regulation, calculating parameter,
Calculating process, parameter definition etc. make assessment result have specific aim.The function of this module is exactly to establish to set different manufacturers protection
Standby or principle basic description.
Combined error personality modnies: the major function of the module is exactly to be closed according to the variation of difference current and stalling current
System, supplements the relational database of (imbalance) electric current and stalling current differential under various external fault conditions, obtaining can be complete
The mathematic(al) representation or data and curves of description protection CT combined error characteristic.
Analysis of operative action module: the major function of this module be by the acting characteristic curve of differential protection with measure
CT combined error characteristic curve drawn out under same coordinate, and by adjusting protection definite value and compare matching between the two
Conjunction relationship obtains different protection schemes and definite value to the safety coefficient of different faults.In addition, if live oscillograph can be obtained
The measurement result of offer, and position of the fault point in error curve plane is obtained by emulation, calculating and protection philosophy simulation
It sets, the movement locus protected when can also judge whether the acting characteristic of protection is reasonable, and reproduce failure.
Combined characteristic error module: the major function of this module is exactly using actual simulation calculation data as foundation, with tool
The protection calculation method of body is means, studies the combined error characteristic of differential protecting CT under the conditions of various relaying configuration schemes, and
It is according to come the adaptive setting that improves differential protection with this characteristic.The main task of this module is exactly to show various protection schemes
Under, the out-of-balance current of differential circuit changes with time relationship when power equipment external area error, and using these data as drawing
The foundation of differential protection error characteristics curve processed.Since error characteristics generally only study the variation of virtual value (or equivalent virtual value)
Influence to acting characteristic, therefore waveform should be difference current and stalling current under various protection schemes and change with time, with
And corresponding relationship between the two.
Processing for error curve, it is also contemplated that the description of operation equation, main purpose is exactly to study differential protection
Actual operation equation and the characteristic relationship of CT combined error.In failure process, if cooperation nargin between the two
Smaller, then the probability of relay protection generation malfunction is then higher.On the contrary, relay is protected if cooperation nargin between the two is larger
The tripping probability protected when minor failure occurs is then higher.The actual operation equation of relay protection and CT combined error characteristic are existed
Drawn out in the same coordinate system, and by vernier point-by-point comparison difference between the two, then can be to the anti-area of relay protection outside
The ability of failure malfunction is quantitatively evaluated.
According to the development status of domestic protective relaying device, acting characteristic generally requires at least consideration tri linear form.
The research object of this combined error personality modnies is for the former, and is emulated every time as far as possible according to a kind of fault point or event
Hinder type, it is therefore necessary to each simulation result is all stored in specific data file, and constantly expands source data,
Enhance the ubiquity meaning of curve.
One or more technical solution provided by the present application, has at least the following technical effects or advantages:
The special application purpose of protective current transformer, determine measure its performance index cannot be only limitted to stable state and
Ratio difference and angular difference under rated condition, will more consider under fault condition under by attenuating dc component and major break down electric current synergy
Progress of disease performance.Existing current transformer characteristic assessment device use mostly standard current transformer, current lifting device, pressure regulator,
The testing equipment of current loading case, mutual-inductor tester, the achievement data of current transformer is obtained by in-site measurement, and operation is multiple
It is miscellaneous, and usually only it is conceived to the steady-state characteristic of current transformer, such as angular difference, measurement and analysis than difference index, and lack
Analysis to current transformer transient characterisitics.
The present invention proposes a kind of assessment side that TPY type current transformer transient characterisitics influence breaker fail protection thus
Method.This method saves the output of system obtained from different inputs and different current transformer model emulations result respectively, with this
As the input parameter of Microcomputer Protection, and the protection philosophy of different manufacturers, different product is combined, can quickly provided accurate
Current transformer performance evaluation result, to improve the measurement accuracy of protected level current transformer, improving the skill of protective relaying device
Art ability provides foundation.Current transformer transient characterisitics can be carried out using model built to grind on what breaker fail protection influenced
Study carefully, the progress of protection technique ability is promoted, to provide basis for Intelligent Optimal transformer substation current transformer configuration scheme.
The present invention will have directly to improving intelligent substation design, performance intelligent substation technical advantage, reducing intelligent station construction cost
Meaning.
Detailed description of the invention
Attached drawing described herein is used to provide to further understand the embodiment of the present invention, constitutes one of the application
Point, do not constitute the restriction to the embodiment of the present invention；
Fig. 1 is current transformer characteristic assessment system overall operation flow diagram；
Fig. 2 is each module frame chart of current transformer characteristic assessment system；
Fig. 3 is transformer working principle schematic diagram；
Fig. 4 is magnetization characteristic fitting flow diagram；
Fig. 5 is current transformer characteristic assessment system estimation flow schematic diagram；
Fig. 6 is that TPY type current transformer excitation voltage and magnetizing current curve describe schematic diagram；
Fig. 7 is that p-type current transformer excitation voltage and magnetizing current curve describe schematic diagram；
Fig. 8 is TPY type current transformer BH curve fitting schematic diagram；
Fig. 9 is p-type current transformer BH curve fitting schematic diagram；
Figure 10 is current transformer test circuit diagram.
Specific embodiment
To better understand the objects, features and advantages of the present invention, with reference to the accompanying drawing and specific real
Applying mode, the present invention is further described in detail.It should be noted that in the case where not conflicting mutually, the application's
Feature in embodiment and embodiment can be combined with each other.
In the following description, numerous specific details are set forth in order to facilitate a full understanding of the present invention, still, the present invention may be used also
Implemented with being different from the other modes being described herein in range using other, therefore, protection scope of the present invention is not by under
The limitation of specific embodiment disclosed in face.
There is nonlinear magnetization characteristic, therefore the magnetization to current transformer by the iron core of aforementioned known current transformer
The reasonable description of process is the key that system modelling.Present case completes P grades and two kinds of current transformers of TPY grade in PSCAD
Model buildings, subsequent simulation will for two kinds of mutual inductors in a variety of works such as different size of current, different secondary lateral load characteristics
It is carried out under condition.
The fitting of magnetization curve:
500kVTPY type current transformer V-I characteristic is surveyed as shown in table 1 and Fig. 6, wherein excitation voltage numerical value is mutually to have
Valid value, exciting current numerical value are phase peak value.
Table 1 surveys TPY type current transformer excitation curve data
| Exciting current (A) | Excitation voltage (V) | Exciting current (A) | Excitation voltage (V) |
| 0.786105 | 22502.7 | 0.016825 | 955.9891 |
| 0.597427 | 22088.86 | 0.012793 | 718.9678 |
| 0.45358 | 21269.38 | 0.009725 | 543.749 |
| 0.344526 | 19147.19 | 0.007389 | 393.5753 |
| 0.261691 | 15592.67 | 0.005617 | 295.0777 |
| 0.198933 | 12108.68 | 0.004266 | 220.147 |
| 0.151203 | 9301.59 | 0.003244 | 162.8779 |
| 0.114945 | 7093.929 | 0.002471 | 119.4868 |
| 0.087317 | 5252.696 | 0.001874 | 87.6184 |
| 0.066365 | 3960.217 | 0.001425 | 63.8335 |
| 0.050495 | 2979.856 | 0.001082 | 46.7329 |
| 0.038326 | 2239.148 | 0.000823 | 34.5246 |
| 0.029138 | 1684.717 | 0.000627 | 24.6746 |
| 0.022144 | 1269.333 | 0.000476 | 14.3853 |
500kV p-type current transformer V-I characteristic is surveyed as shown in table 2 and Fig. 7,
Table 2 surveys p-type current transformer excitation curve data
According to minimum two at the method for method high-precision analog in the form of power function, based on 1 data of table and TPY type electricity can be obtained
The fitting coefficient of current transformer are as follows:
The fitting coefficient of p-type current transformer can be obtained in data based on table 2 are as follows:
Fitting magnetization curve and the actual curve comparison of TPY and P grades of current transformer are as shown in Figure 8 and Figure 9.It can be seen by figure
Actual curve and simulation curve coincide substantially out.For TPY type current transformer, the keen current converted to secondary side is about
0.32A, magnetic linkage are about 80Wb；Keen current for p-type current transformer, conversion to secondary side is about 0.01A, and magnetic linkage is about
5.5Wb。
Based on the functional relation expression formula formula 2 that current transformer mathematical modeling is final, convention is emulated referring to PSCAD, it is secondary
Current measurement value conversion in side as mode input and exports current unit to primary side, and using kA.But in order to real with secondary side
It surveys result to correspond to, the inside output duration set that model provides is reduction to secondary side as a result, it is A that electric current, which corresponds to unit,.It is imitative
True operating condition one: under fault-free, increase line current periodic component amplitude, no aperiodic component:
When simulation parameter is arranged, secondary side load rating impedance is set as 15 Ω, and turn ratio reference is actually given as 4000 circles.
For 500kV route, transmission capacity is drafted as 2000MW, and calculating and obtaining specified operation phase current peak value is about 3kA.
Ball bearing made as shown in Figure 10 is built, ideal voltage source impedance loop (internal resistance of source and line resistance) amounts to 2
Ω, TPY type and p-type Current Transformer Secondary side band hinder inductive load, and size is 15 Ω, and impedance angle is 50 °, and corresponding resistance is
9.6 Ω, inductance 0.0366H.Apply specified primary side current 3kA (peak value), is emulated.
By simulation result it is found that in input rated current, under conditions of band rated impedance: TPY type current transformer excitation
Current peak is only about 0.14mA, and magnetic linkage peak value is only about 0.035Wb, far smaller than inflection point exciting current (0.32A) and inflection point
Magnetic linkage (80Wb) size, also unsaturated, exporting error between electric current and input current is only about 2/10000ths；P-type Current Mutual Inductance
Device exciting current peak value is only about 0.09mA, and magnetic linkage peak value is only about 0.035Wb, far smaller than inflection point exciting current (0.01A)
It with inflection point magnetic linkage (5.5Wb) size, is also just saturated far away, exporting error between electric current and input current is only about a ten thousandth.
It follows that under normal operation, P grades of current transformers and TPY current transformer measurement error are negligible.
In view of 500KV line switching rupturing capacity is 63kA, corresponding phase current peak value is 89.10kA, therefore is kept secondary
Lateral load is rated impedance, further increases line current to 63kA, emulates to TPY type and p-type current transformer.
Under conditions of input rupturing capacity corresponding current, secondary side band rated impedance: TPY type current transformer excitation electricity
Stream peak value is only about 0.0045A, and magnetic linkage peak value is only about 1.05Wb, is much smaller than inflection point exciting current (0.32A) and inflection point magnetic linkage
(80Wb) size, still operates in non-saturated region, and measurement error is less than a ten thousandth；P-type current transformer exciting current peak value
Only about 0.0025A, magnetic linkage peak value is only about 1.1Wb, again smaller than inflection point exciting current (0.01A) and inflection point magnetic linkage (5.5Wb)
Size, measurement error are less than one thousandth.
Under rated impedance, to make p-type CT saturation, it is necessary to continue to increase primary current, as shown in Table 2 inflection point magnetic
Chain is about 5.5Wb, and it is 1200V (virtual value) that corresponding secondary side, which calculates voltage,.Secondary side at this time can be obtained with secondary side impedance computation
Electric current is about 80A (virtual value), and conversion to primary side is 320kA (virtual value), to observe apparent saturated phenomenon, one
Secondary side injection 600kA (virtual value) electric current observes p-type Simulation of current transformer.It is mutual to TPY type electric current under same Injection Current
Sensor is emulated.
By simulation result it is found that p-type current transformer exciting current peak value has reached 0.15A, magnetic linkage peak value is about 10Wb,
Mutual inductor has passed over inflection point and enters saturation workspace, and obvious distortion occurs in exciting current；For TPY type current transformer, encourage
Magnetic current peak just reaches 0.04A, and magnetic linkage peak value is about 10Wb, and still less than inflection point respective value, TPY works in non-saturated region.
To be saturated TPY, it is necessary to apply great primary current.Inflection point magnetic linkage is about 80Wb as shown in Table 1, and correspondence is secondary
It is 19991V (virtual value) that side, which calculates voltage,.It is about 1185A (effective that secondary side current at this time, which can be obtained, with secondary side impedance computation
Value), conversion is 4739kA (virtual value) to primary side, to observe apparent saturated phenomenon, will be injected in primary side
6000kA (virtual value) electric current, is emulated.Under same Injection Current, p-type current transformer is emulated.
By simulation result it is found that TPY type current transformer is after primary side current reaches 6000kA, exciting current peak value can
Reach 0.52A, magnetic linkage peak value is about 100Wb, crosses inflection point and enters saturation workspace, obvious distortion occurs in electric current.However, real
In be generally not in such big electric current.Therefore, it is possible to determine that, the almost impossible saturation of TPY type current transformer.Identical work
Under condition, p-type current transformer exciting current peak value has reached 1200A, and magnetic linkage peak value is about 58Wb, and secondary side current waveform is sent out
Raw Severe distortion.
Emulate operating condition two: under fault condition, line current contains periodic component and without aperiodic component
Due to the presence of DC component, core sataration process is accelerated rapidly, and the excitation impedance after saturation substantially reduces, secondary
Time constant will become smaller, and magnetic field energy in excitation winding can not effectively quickly after this disconnects current transformer primary side
Release causes secondary side current decaying slack-off, so as to form smearing.From this, hangover immediate cause still by
In the magnetic saturation effect of iron core, degree of saturation is higher, and trailing phenomenon is more obvious.Mutual inductor occurs obviously after fault current cutting
Trailing phenomenon.
Assuming that fault current considers according to switch rupturing capacity 63kA, primary side time constant is 0.08s, is given below by needle
Simulating, verifying is carried out to secondary side different load size, load type.Load impedance size is 15 Ω of rated value, resistance 9.6
Ω, inductance 0.0366H, setting 0s break down, and the emulation of fault trip after 200ms, emulation duration is set as 0.8s, right
TPY type and p-type current transformer are emulated.
The single fault trip under specified resistance sense loading condition: TPY type current transformer exciting current peak value is about
0.06A, magnetic linkage peak value are about 16.5Wb, are not up to saturated, and maximum current measurement error is about 3/1000ths in failure process.By
In the presence of DC component, one direction offset occurs for excitation, still there are small tail currents phenomenon, primary side tail currents
Virtual value is about 0.22kA.P-type current transformer exciting current peak value is about 1.7A, and magnetic linkage peak value is about 16Wb, has been entered deep
Degree saturation, primary side tail currents virtual value is about 5kA, and maximum current measurement error is about 6% in failure process.Thus may be used
See, TPY type current transformer performance is substantially better than p-type current transformer under fault condition.
Pure resistance is changed into load, resistance is 15 Ω, inductance 0.0001H, remaining emulation operating condition is constant, to TPY type
It is emulated with p-type current transformer.
TPY type current transformer exciting current peak value is about under the conditions of purely resistive load it can be seen from simulation result
0.095A, magnetic linkage peak value are about 25Wb, and measurement error increases to 5/1000ths.Though being not up to saturated, tail currents are primary
Side virtual value increases to 0.38kA.It can therefore be concluded that tail currents are affected by secondary side time constant, resistance is bigger,
Time constant is smaller, and tail currents are bigger, decays slower.P-type current transformer exciting current peak value is about 5.4A, magnetic linkage peak value
It is about 20Wb, has entered depth saturation, tail currents primary side virtual value is up to 11kA, and maximum current measurement misses in failure process
Difference is about 15%.
Pure inductance is changed into load, resistance is 0.001 Ω, inductance 0.0478H, remaining emulation operating condition is constant, to TPY
Type and p-type current transformer are emulated.
Pure inductive load condition TPY type current transformer exciting current peak value is about 0.008A, and magnetic linkage peak value is about 2Wb,
It is not up to saturated, tail currents virtual value initial value is 0.005kA, and maximum error of measuring is about 2/10000ths in failure process.It can
See, loads as after pure inductance, secondary side time constant is very big, and tail currents are decayed soon.P-type current transformer excitation electricity
Stream peak value is about 0.0045A, and magnetic linkage peak value is about 2Wb, does not enter saturation, and tail currents virtual value initial value is only 0.003kA, therefore
Maximum current measurement error is about 3/10000ths during barrier.
It is as shown in Table 3 and Table 4 to summarize above-mentioned simulation result, it will thus be seen that no matter how secondary lateral load is arranged, TPY type
Current transformer is able to maintain good measurement performance in the transient process that rupturing capacity corresponds to short circuit current, has good
Workload-adaptability.P-type current transformer is easily saturated in transient process, causes the sharp increase of current measurement errors, even
More than in " requirement of 1997 protective current transformer, transient characterisitics of GB16847-" about current transformer peak-peak instantaneous value
Error should regulation less than 10%.
Influence of the load impedance characteristic to TPY type current transformer under 3 fault condition of table
Influence of the load impedance characteristic to p-type current transformer under 4 fault condition of table
Emulate operating condition three: C-O-C-O
Under the conditions of rated impedance (R2=9.6 Ω, L2=0.0336H), C1=0.1s, O1=0.1s, C2=0.1s are set,
O2=0.1s carries out the emulation of the multiple cyclic processes of failure reclosing (5), and emulation duration is set as 2s, to TPY type and p-type electricity
Current transformer is emulated.
Multiple failure reclosing (rated impedance) under fault condition, magnetic linkage will not reduce after route cutting, i.e. remanent magnetism
It is retained in the level of cutting.After reclosing, newly-established magnetic flux is identical as remanent magnetism polarity, and iron core can more tend to be full after superposition
With, exciting current also increases sharply, the process it is continuous repeat magnetic linkage and exciting current can be made constantly to be superimposed.
For TPY type current transformer, last magnetic linkage peak value is up to 120Wb, and exciting current peak value is up to 0.92A, hence it is evident that
More than inflection point respective value, constantly expand into depth saturation state, therefore by the measurement error that exciting current reflects, first logical
Electric period worst error is up to 0.4%, and has reached to a last power cycles (amounting to 5 COCO circulations) worst error
To 3.3%.During recycling COCO, direct current magnetic linkage is constantly accumulated, and exciting current is more and more big, and trailing phenomenon is also more and more brighter
Aobvious, tail currents virtual value initial value is 0.22kA after first time separating brake, by multiple COCO processes, to the end a separating brake hangover
It is 3.7kA that current effective value initial value, which increases,.
For p-type current transformer, last magnetic linkage peak value is up to 23Wb, and exciting current peak value is up to 12A, considerably beyond turning
Point respective value, into depth saturation state, first power cycles worst error is up to 25%, and all to a last energization
Phase (amounting to 5 COCO circulations) worst error has reached 37.5%.Tail currents virtual value initial value is after first time separating brake
20kA, by multiple COCO processes, it is 30kA that a separating brake tail currents virtual value initial value, which increases, to the end.Simultaneously, by
Depth saturation is progressed into iron core, the trailing phenomenon of two kinds of mutual inductors is also gradually obvious.
It can be seen that by above-mentioned case, method provided by the present invention can accurately assess the characteristic of current transformer, and energy
Judge influence of its transient performance for breaker fail protection.
Although preferred embodiments of the present invention have been described, it is created once a person skilled in the art knows basic
Property concept, then additional changes and modifications may be made to these embodiments.So it includes excellent that the following claims are intended to be interpreted as
It selects embodiment and falls into all change and modification of the scope of the invention.
Obviously, various changes and modifications can be made to the invention without departing from essence of the invention by those skilled in the art
Mind and range.In this way, if these modifications and changes of the present invention belongs to the range of the claims in the present invention and its equivalent technologies
Within, then the present invention is also intended to include these modifications and variations.
Claims (10)
1. a kind of current transformer characteristic appraisal procedure, which is characterized in that the described method includes:
Based on current transformer mathematical model, the steady-state characteristic energy and transient performance of current transformer are obtained, wherein Current Mutual Inductance
Device mathematical model includes: current transformer steady-state model and current transformer transient Model；
Analogue system based on protected object, obtain different faults under the conditions of flow through differential protection respectively survey mutual inductor failure electricity
Stream；
It is inputted the simulation result of PSCAD as the primary side of current transformer, obtains the secondary side output electricity of current transformer
Stream；
The Current Transformer Secondary side output actual design parameter of electric current combination current transformer is studied to the magnetic induction of its iron core
Intensity and secondary side limit induced electromotive force situation；
Using to different inputs and the obtained output result of different current transformer model emulations as the input parameter of Microcomputer Protection,
Study influence of the current transformer Transfer characteristic to relay protection.
2. current transformer characteristic appraisal procedure according to claim 1, which is characterized in that the method also includes:
The electric parameter of measurement description current transformer Transfer characteristic, including secondary winding resistance, secondary winding leakage reactance, no-load voltage ratio are surveyed
Amount, polarity check, excitation loss resistance, magnetization curve, remanence coefficient, secondary time constant, secondary load impedence and impedance angle；
The parameter measured using gain of parameter module establishes the mathematical model for describing corresponding current transformer progress of disease performance.
3. current transformer characteristic appraisal procedure according to claim 1, which is characterized in that current transformer steady-state model
It include: magnetic potential balance equation and electric potential balancing equation, wherein magnetic potential balance equation are as follows:Wherein,For
Exciting current；For primary current；N1For first winding the number of turns；For a magnetic potential；For secondary current；N2For secondary winding
The number of turns；For secondary magnetic potential；
Electric potential balancing equationWherein,For secondary potential,For secondary circuit voltage,It is two
Minor loop electric current, R'2For secondary circuit resistance, j is vector imaginary-part operator, X'2For secondary circuit reactance；First winding end voltage
Relationship with secondary impedance isWherein,For primary circuit voltage, R'zFor load
Resistance, X'zFor load reactance.
4. current transformer characteristic appraisal procedure according to claim 1, which is characterized in that current transformer transient Model
Are as follows:
Wherein, k1,k2,k3For fitting coefficient, ψ is magnetic linkage, L2For secondary inductance, i1For primary current, i2For secondary current, R2For
Secondary resistance, t are the time.
5. current transformer characteristic appraisal procedure according to claim 1, which is characterized in that the method also includes:
The steady-state characteristic for obtaining current transformer can judge the nameplate parameter of current transformer, specifically include with before transient performance:
Current transformer primary current rated value is judged by testing resulting no-load voltage ratio；
The judgement of CT type: according to the test result of open-circuit test, judge the type of tested CT；
Nominal load judgement: according to the test result of secondary load loop test, judge current transformer rated output standard value；
The judgement of accurate limitation ratio: according to the inferred results of nominal load, and the quadratic limit voltage that obtains of reference test
Measured value judges the possible accurate limitation ratio of current transformer.
6. current transformer characteristic appraisal procedure according to claim 1, which is characterized in that obtain the steady of current transformer
State property energy, specifically includes: the ratio difference and angular difference of calculating current mutual inductor；The combination misalignment of calculating current mutual inductor；Calculating current
The V-A characteristic of mutual inductor；10% error characteristics curve of calculating current mutual inductor.
7. current transformer characteristic appraisal procedure according to claim 1, which is characterized in that obtain the temporary of current transformer
State property energy, specifically includes:
Extract the fault parameter of current transformer transient characterisitics analogue system；
Current transformer transient characterisitics simulation calculation: to meet the fault current of transient characterisitics analogue system feature as input quantity,
Using the output parameter of test equipment as model parameter, by solving the differential equation, the circuit of description current transformer state is obtained
And magnetic circuit parameters, comprising: exciting current i0(t), electric current i is exporteds(t), iron core magnetic linkage ψm(t) and secondary side induced electromotive force em
(t), the magnetic induction density B (t) and magnetic field strength H (t) of current transformer are obtained.
8. current transformer characteristic appraisal procedure according to claim 1, which is characterized in that imitative based on protected object
True system obtains and flows through the approximating method that differential protection respectively surveys magnetization curve in the fault current of mutual inductor under the conditions of different faults
Include:
i0=k1Ψ+k2Ψ3+k3Ψ5, Ψ is magnetic linkage, solves coefficient k in above formula using least square method1,k2,k3；It determines first
Y=f (Ψ)=i to be found a function0=k1Ψ+k2Ψ3+k3Ψ5, magnetization curve is enable most preferably to be fitted experimental observed data (Ii,
Ui) (i=1,2 ... ... N), i.e., so that formulaObtain minimum value；Being write as matrix form has:
I=[I1 I2…IN]T (5)
K=[K1 K2 K3]T (6)
Wherein, INFor n-th of extraction of values of electric current；
Objective function are as follows:
minδ2=(I-GK)T(I-GK) (8)
K is that the sufficient and necessary condition of least square solution is to meet normal equation group:
GTGK=GTI (9)
Due to f (Ψ)=i0=k1Ψ+k2Ψ3+k3Ψ5, basic function f1(Ψ)=Ψ, f2(Ψ)=Ψ3, f3(Ψ)=Ψ5, therefore
It is available:
K can be acquired by above formula1、k2、k3Value, and fitting magnetization curve is acquired by fitting function.
9. current transformer characteristic appraisal procedure according to claim 1, which is characterized in that by the simulation result of PSCAD
Primary side as current transformer inputs, and obtains the solution of the magnetic linkage differential equation in the secondary side output electric current of current transformer
Method includes:
To the differential equationYn+1=Yn+h×D(tn,Yn), wherein D (tn,Yn) be a little in (tn,tn+1) in
Average speed, h are step-length, YnFor n-th of functional value, then have:
It obtains:
The differential equation can be obtained are as follows:
Solve the above-mentioned differential equation:
The fitting expression that the solution of magnetic linkage brings magnetic linkage into can be found out the i of exciting current by the solution that can acquire magnetic linkage Ψ0, based on encouraging
Magnetoelectricity stream i0Find out secondary side current size.
10. a kind of current transformer characteristic assessment system, which is characterized in that the system comprises:
First obtains module, for being based on current transformer mathematical model, obtains the steady-state characteristic energy and transient state of current transformer
Performance, wherein current transformer mathematical model includes: current transformer steady-state model and current transformer transient Model；
Second obtains module, for the analogue system based on protected object, flows through differential protection under the conditions of acquisition different faults
Each fault current for surveying mutual inductor；
Evaluation module obtains current transformer for inputting the simulation result of PSCAD as the primary side of current transformer
Secondary side exports electric current；The Current Transformer Secondary side output actual design parameter of electric current combination current transformer is studied into its iron
The magnetic induction intensity and secondary side limit induced electromotive force situation of the heart；It will be to different inputs and different current transformer model emulations
Input parameter of the obtained output result as Microcomputer Protection studies influence of the current transformer Transfer characteristic to relay protection.
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