CN105891738A - Frequency conversion measurement circuit for over-excitation protection and over-excitation protection method - Google Patents

Frequency conversion measurement circuit for over-excitation protection and over-excitation protection method Download PDF

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CN105891738A
CN105891738A CN201610368898.7A CN201610368898A CN105891738A CN 105891738 A CN105891738 A CN 105891738A CN 201610368898 A CN201610368898 A CN 201610368898A CN 105891738 A CN105891738 A CN 105891738A
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lsqb
resistance
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over
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CN105891738B (en
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包明磊
徐业荣
桑建斌
李明
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Nanjing SAC Automation Co Ltd
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Nanjing SAC Automation Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/007—Environmental aspects, e.g. temperature variations, radiation, stray fields
    • G01R33/0082—Compensation, e.g. compensating for temperature changes

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Abstract

The present invention provides a frequency conversion measurement circuit for over-excitation protection and an over-excitation protection method. The circuit can measure the multiples of over-excitation in real time, has high conversion speed and high precision, and is just slightly affected by frequency with appropriate circuit parameters provided. Since judgment on a zero crossing point is not required, the inherent delay of the protection is short, and therefore, requirements of the over-excitation protection for action time and return time can be satisfied; and a temperature compensation circuit is adopted, so that accuracy error caused by temperature variation can be effectively prevented. According to the over-excitation protection method, the frequency conversion measurement circuit is adopted to convert signals to be tested into direct current voltage signals, and the direct current voltage signals are outputted; modes for judging whether the protection acts are flexible, hardware can be used to directly judge whether the protection acts, and software can be also used to indirectly judge whether the protection acts; a plurality of parabolas are adopted to fit an inverse-time curve, so that the problem of unsmooth time variation on fitting points can be solved; and a heat effect accumulation discrimination algorithm is adopted, so that the cumulative effect of historical values in an over-excitation value dynamic variation process can be reflected.

Description

Commutation frequency measuring circuit and over-excitation protection method for over-excitation protection
Technical field
The present invention relates to a kind of commutation frequency measuring circuit for over-excitation protection and over-excitation protection method, belong to electricity Force system Main Equipment Protection Technology field.
Background technology
In the large and medium-sized electromotor of power system or tranformer protection, when inverse time lag over-excitation protection is to prevent overexcitation The protection causing iron core overheated and must join.Conventional inverse time lag over-excitation protection generally uses computed in software method to realize overexcitation The measurement of multiple, generally uses following method and realizes: introducing voltage by voltage transformer, sampled voltage signal obtains voltage transient Value, respectively numerical calculation voltage U value and frequency quantity f value, resynthesis calculates U/f value；Or the zero crossing of first measured waveform, meter Calculate the integral of pulse shape value between two zero crossings, be converted into U/f value further.
Above two algorithm is used to there is problems in that
(1) due to will the zero crossing of measured waveform, so the size of time of calculating of protection and frequency has relation, frequency The least, data window is the longest, calculates speed the slowest, and inherent delay is the longest, and protection act and time of return are the longest；
(2), measuring zero crossing when, when being non-sampled point for zero crossing, need to simulate, frequently by interpolation method There is error in rate measurement；
(3) being generally adopted by the algorithm of trapezoidal matching when calculating integral of pulse shape value, there is error in result of calculation.
Inverse-time curve used by over-excitation protection is electromotor or the actual overexcitation limit of transformer manufacturing producer offer Curve, different electromotors or the corresponding different inverse-time curve of transformator, be difficult to accurately describe instead with a kind of mathematic(al) representation Time limit relation, carrys out matching inverse-time curve frequently with many broken lines, calculates moving under different overexcitation multiple value according to these broken lines Make time limit ts, then compare with timer tj value, as tj >=ts, over-excitation protection action.
Above-mentioned algorithm is used to there is problems in that
(1) polygometry calculating operation time limit ts changes unsmooth near match point, when overexcitation value produces less rocking When, calculated ts error is relatively big, often cannot meet time precision requirement；
(2) time criterion be built upon entering the too drastic magnetic value of inverse-time curve static constant under conditions of, and actual mistake Excitatory value is dynamically change, without the impact of the consideration too drastic magnetic value of history, can bring uncertain time deviation.
It is proposed that one can transient measurement overexcitation multiple, calculate iron core heat accumulation situation special overexcitation algorithm By necessary.
Summary of the invention
The present invention is to solve drawbacks described above and deficiency present in prior art, it is provided that a kind of for over-excitation protection Commutation frequency measuring circuit and over-excitation protection method.
For solving above-mentioned technical problem, the present invention provides a kind of commutation frequency measuring circuit for over-excitation protection, bag Include power vd D, ground GND, operational amplifier A 1, operational amplifier A 2, diode V1, diode V2, sampling resistor R1, sampling electricity Hold C1, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, filter resistance R8 and filter capacitor C2；Letter to be measured Number Vi connects one end of sampling resistor R1, and the other end of R1 is respectively by sampling capacitance C1 ground connection GND, be connected to by resistance R3 The positive input terminal of operational amplifier A 1, by resistance R6 and the positive input terminal that connects end operational amplifier A 2；Operational amplifier A 1 Negative input end be connected with the negative pole of diode V1 and one end of resistance R4 respectively, and by resistance R2 ground connection GND, operation amplifier The outfan of device A1 is connected with the positive pole of diode V1 and the negative pole of diode V2 respectively；The positive pole of diode V2 and resistance R4's The other end is connected, and is connected to the negative input end of operational amplifier A 2 by resistance R5, resistance R7 bearing operational amplifier A 2 The outfan of input and operational amplifier A 2 links together；The outfan of operational amplifier A 2 passes through filter resistance R8 with defeated Going out signal Vo to be connected, output signal Vo passes through filter capacitor C2 ground connection GND.
Further, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, the resistance of resistance R7 meet following relationship: R2=R3=R4=R5=R6, R7=2R2.
Further, described measuring circuit also includes that protection circuit, described protection circuit include stabilivolt VD1 and stabilivolt The negative pole of VD2, the positive pole of stabilivolt VD1 and stabilivolt VD2 all junctions with sampling resistor R1 and sampling capacitance C1 are connected, surely The negative pole of pressure pipe VD1 connects power vd D, plus earth GND of stabilivolt VD2.
Further, described measuring circuit also includes that temperature-compensation circuit, described temperature-compensation circuit include anti-temperature coefficient Electric capacity C3, anti-temperature coefficient electric capacity C4, anti-temperature coefficient electric capacity C3 is connected in parallel with sampling capacitance C1, anti-temperature coefficient electric capacity C4 With filter capacitor C2 is connected in parallel.
Over-excitation protection method, comprises the following steps:
Step 1, accesses the commutation frequency measuring circuit described in any one of claim 1-4, described frequency by measured signal The size of measured signal frequency is converted in the amplitude of alternating voltage by conversion measuring circuit so that the amplitude of output voltage and frequency Rate is inversely proportional to, and meanwhile, described commutation frequency measuring circuit carries out fine all wave rectification to the waveform of output voltage, exports after filtering D. c. voltage signal, makes DC voltage value become with overexcitation multiple value by adjusting resistance value corresponding in circuit with capacitance Direct ratio；
Step 2, uses and directly judges and indirectly judge that two kinds of methods determine and protect whether action.
Wherein, direct determination methods is, uses comparator DC voltage value and setting voltage value to be compared, works as direct current When magnitude of voltage is more than setting voltage value, protection transmits and trips.
Indirectly determination methods specifically includes following steps:
Step 2.1, the direct current signal sampling producing step 1 obtains overexcitation instantaneous value Uf；
Step 2.2, discrete actual overexcitation inverse-time curve, obtain one group of definite value (Uf0,t0), (Uf1,t1) ... (Ufn, tn) ..., (Ufm,tm), and realize curve matching with multistage curve-parabola-fitting method, specific algorithm is as follows:
Work as Uf＜ Uf0Time, time definite value ts=t0；
Work as Ufn-1≤Uf＜ Ufn＜ Ufn+1, and during 1≤n ＜ m, time definite value tsComputing formula be:
t s = [ U f - Uf n ] * [ U f - Uf n + 1 ] [ Uf n - 1 - Uf n ] * [ Uf n - 1 - Uf n + 1 ] t n - 1 + [ U f - Uf n - 1 ] * [ U f - uf n + 1 ] [ Uf n - Uf n - 1 ] * [ Uf n - Uf n + 1 ] t n + [ U f - Uf n ] * [ U f - Uf n - 1 ] [ Uf n + 1 - Uf n ] * [ Uf n + 1 - Uf n - 1 ] t n + 1
Work as Ufm-1≤Uf＜ UfmTime, time definite value tsComputing formula be:
t s = [ U f - Uf m - 1 ] * [ U f - Uf m ] [ Uf m - 2 - Uf m - 1 ] * [ Uf m - 2 - Uf m ] t m - 2 + [ U f - Uf m - 2 ] * [ U f - Uf m ] [ Uf m - 1 - Uf m - 2 ] * [ Uf m - 1 - Uf m ] t m - 1 + [ U f - Uf m - 2 ] * [ U f - Uf m - 1 ] [ Uf m - Uf m - 2 ] * [ Uf m - Uf m - 1 ] t m
Work as Uf≥UfmTime, time definite value ts=tm；
Step 2.3, carries out heat effect accumulation computing, obtains heat accumulation value M；
Step 2.4, judges to protect whether action according to heat accumulation value M: when M >=1, protection transmits and trips；As M < 1 Time, protection returns.
Described step 2.3 particularly as follows:
For the K moment, overexcitation instantaneous value is Uf(k): when overexcitation instantaneous value UfK () is less than inverse-time curve minima Time, heat accumulation value M resets；When overexcitation instantaneous value UfWhen () is more than inverse-time curve minima k, in conjunction with Uf(k) and step 2.2 The computing formula of the fitting of parabola curve obtained, is calculated instantaneous time definite value ts(k)；
Measuring △ t interval time (k)=t (the k)-t (k-1) calculated away from the last time, t (k) is the absolute time of current time Mark, t (k-1) is a upper absolute time mark calculating the moment；
Calculate heat accumulation value M: work as Uf(k) ＜ Uf0Time, M=0；Work as Uf(k)≥Uf0Time,Wherein, Uf0 First match point for inverse-time curve.
The Advantageous Effects that the present invention is reached:
The commutation frequency measuring circuit for over-excitation protection that the present invention provides, this circuit can measure overexcitation in real time Multiple, conversion speed is fast, and precision is high, little by frequency influence under suitable circuit parameter, and owing to need not differentiate zero crossing, protects Protect inherent delay short, effectively meet over-excitation protection to movement time and the demand of time of return；Use temperature-compensation circuit, Can effectively prevent the trueness error that variations in temperature is brought.
The present invention also provides for a kind of over-excitation protection method, and the method converts measuring circuit by letter to be measured by said frequencies Number it is converted into d. c. voltage signal output, it is judged that the mode protecting whether action is flexible, hardware both can be used directly and judged, it is possible to Indirectly being judged by software sampling, when indirectly judging, amount of calculation is few, and real-time is good；Use the multistage fitting of parabola inverse time lag Curve, can solve the rough problem of time change, enhancing action time precision in match point；Heat effect accumulation is used to sentence Other algorithm can overcome in conventional comparison expression time, algorithm inverse time lag cannot accurately reflect too drastic magnetic value dynamic changing process Defect, truly reflects the cumulative effect of history value in too drastic magnetic value dynamic changing process, and operating time of protection precision is higher, thing Reason implication is definitely, it determines more science is accurate.
Accompanying drawing explanation
The commutation frequency measuring circuit schematic diagram of Fig. 1 present invention；
The protection circuit of Fig. 2 present invention and commutation frequency measuring circuit connection diagram；
The temperature-compensation circuit of Fig. 3 present invention and commutation frequency measuring circuit connection diagram；
Fig. 4 embodiments of the present invention medium frequency conversion measuring circuit figure；
The over-excitation protection method flow schematic diagram of Fig. 5 present invention；
The multistage curve-parabola-fitting method schematic diagram of Fig. 6 present invention.
Detailed description of the invention
The invention will be further described below in conjunction with the accompanying drawings.Following example are only used for clearly illustrating the present invention Technical scheme, and can not limit the scope of the invention with this.
As it is shown in figure 1, the commutation frequency measuring circuit for over-excitation protection that the present invention provides, including power vd D, ground GND, operational amplifier A 1, operational amplifier A 2, diode V1, diode V2, sampling resistor R1, sampling capacitance C1, resistance R2, Resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, filter resistance R8 and filter capacitor C2；Measured signal Vi connects sampling One end of resistance R1, the other end of R1 is respectively by sampling capacitance C1 ground connection GND, be connected to operational amplifier A 1 by resistance R3 Positive input terminal, by resistance R6 and connect end operational amplifier A 2 positive input terminal；The negative input end of operational amplifier A 1 divides It is not connected with the negative pole of diode V1 and one end of resistance R4, and by resistance R2 ground connection GND, the outfan of operational amplifier A 1 It is connected with the positive pole of diode V1 and the negative pole of diode V2 respectively；The positive pole of diode V2 is connected with the other end of resistance R4, And the negative input end of operational amplifier A 2 it is connected to by resistance R5, resistance R7 is by the negative input end of operational amplifier A 2 and computing The outfan of amplifier A2 links together；The outfan of operational amplifier A 2 passes through filter resistance R8 and output signal Vo phase Even, output signal Vo passes through filter capacitor C2 ground connection GND.In use, in order to preferably ensure the voltage of output signal Value is directly proportional to overexcitation multiple value, under resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, the resistance of resistance R7 meet Row relational expression: R2=R3=R4=R5=R6, R7=2R2.
In order to protect operational amplifier A 1, operational amplifier A 2 and follow-up circuit not to damage, described measuring circuit also includes Protection circuit, described protection circuit includes stabilivolt VD1 and stabilivolt VD2, the positive pole of stabilivolt VD1 and bearing of stabilivolt VD2 The most all junctions with sampling resistor R1 and sampling capacitance C1 are connected, and the negative pole of stabilivolt VD1 meets power vd D, stabilivolt VD2's Plus earth GND, as shown in Figure 2.
Described measuring circuit also includes temperature-compensation circuit, it is possible to reduce the temperature drift impact on circuit measuring precision, described Temperature-compensation circuit includes anti-temperature coefficient electric capacity C3, anti-temperature coefficient electric capacity C4, and anti-temperature coefficient electric capacity C3 is with sampling capacitance C1 is connected in parallel, and anti-temperature coefficient electric capacity C4 is connected in parallel, as shown in Figure 3 with filter capacitor C2.
As the detailed description of the invention of the present invention, as shown in Figure 4, in circuit, the design parameter of required electronic devices and components is: R1=220K, R2=R3=R4=R5=R6=10K, R7=20K, R8=120K, C1=0.1u, C2=0.047u, diode The model of V1 and diode V2 is 1SS355, and the frequency for over-excitation protection that can better illustrate the present invention provides is rolled over Calculate the technique effect of measuring circuit.
The size of measured signal frequency can be converted in the amplitude of alternating voltage by this circuit so that the amplitude of output voltage It is inversely proportional to frequency, figure 4, it is seen that output voltage Wherein f is the frequency of input signal, therefore, it can be seen that output voltage VjAmplitude be directly proportional to overexcitation multiple, and conversion Speed is fast.
Output voltage VjSignal V is obtained after operational amplifier A 1 processing of circuitz, computing formula is:Signal VzOutput signal is obtained after operational amplifier A 2 processing of circuit Vo, computing formula is:
V O - V z 20 K = V j - V z 10 K &DoubleRightArrow; V O = 3 V j - 2 V z
By VzResult of calculation bring above formula into, can obtain:
To sum up, commutation frequency measuring circuit can measure overexcitation multiple in real time, and its result conversion speed is fast, and precision is high, Little by frequency influence, and owing to need not differentiate zero crossing, protection inherent delay is short, when effectively meeting over-excitation protection to action Between and the demand of time of return.
As it is shown in figure 5, the present invention provides a kind of over-excitation protection method, comprise the following steps:
Step 1, accesses the commutation frequency measuring circuit described in any one of claim 1-4, described frequency by measured signal The size of measured signal frequency is converted in the amplitude of alternating voltage by conversion measuring circuit so that the amplitude of output voltage and frequency Rate is inversely proportional to, and meanwhile, described commutation frequency measuring circuit carries out fine all wave rectification to the waveform of output voltage, exports after filtering D. c. voltage signal, makes DC voltage value become with overexcitation multiple value by adjusting resistance value corresponding in circuit with capacitance Direct ratio；
Step 2, uses and directly judges and indirectly judge that two kinds of methods determine and protect whether action.
Wherein, direct determination methods is, uses comparator DC voltage value and setting voltage value to be compared, works as direct current When magnitude of voltage is more than setting voltage value, protection transmits and trips.
Indirectly determination methods specifically includes following steps:
Step 2.1, the direct current signal sampling producing step 1 obtains overexcitation instantaneous value Uf；
Step 2.2, discrete actual overexcitation inverse-time curve, and realize curve matching with multistage curve-parabola-fitting method.Existing Having general algorithm in technology to use polygometry matched curve, error is relatively big, and changes unsmooth near definite value point, and slope occurs Sudden change, when overexcitation value produces less rocking when, calculated time error is the biggest.As shown in Figure 6, multistage is used Curve-parabola-fitting method carries out curve fitting, and matched curve error is little, closer to actual curve and the most flat near definite value point Sliding, that slope sudden change will not be produced problem, fitting algorithm is as follows:
Discrete actual overexcitation inverse-time curve, obtains one group of definite value (Uf0,t0), (Uf1,t1) ... (Ufn,tn) ..., (Ufm,tm), and realize curve matching with multistage curve-parabola-fitting method, specific algorithm is as follows:
Work as Uf＜ Uf0Time, time definite value ts=t0；
Work as Ufn-1≤Uf＜ Ufn＜ Ufn+1, and during 1≤n ＜ m, time definite value tsComputing formula be:
t s = &lsqb; U f - Uf n &rsqb; * &lsqb; U f - Uf n + 1 &rsqb; &lsqb; Uf n - 1 - Uf n &rsqb; * &lsqb; Uf n - 1 - Uf n + 1 &rsqb; t n - 1 + &lsqb; U f - Uf n - 1 &rsqb; * &lsqb; U f - uf n + 1 &rsqb; &lsqb; Uf n - Uf n - 1 &rsqb; * &lsqb; Uf n - Uf n + 1 &rsqb; t n + &lsqb; U f - Uf n &rsqb; * &lsqb; U f - Uf n - 1 &rsqb; &lsqb; Uf n + 1 - Uf n &rsqb; * &lsqb; Uf n + 1 - Uf n - 1 &rsqb; t n + 1
Work as Ufm-1≤Uf＜ UfmTime, time definite value tsComputing formula be:
t s = &lsqb; U f - Uf m - 1 &rsqb; * &lsqb; U f - Uf m &rsqb; &lsqb; Uf m - 2 - Uf m - 1 &rsqb; * &lsqb; Uf m - 2 - Uf m &rsqb; t m - 2 + &lsqb; U f - Uf m - 2 &rsqb; * &lsqb; U f - Uf m &rsqb; &lsqb; Uf m - 1 - Uf m - 2 &rsqb; * &lsqb; Uf m - 1 - Uf m &rsqb; t m - 1 + &lsqb; U f - Uf m - 2 &rsqb; * &lsqb; U f - Uf m - 1 &rsqb; &lsqb; Uf m - Uf m - 2 &rsqb; * &lsqb; Uf m - Uf m - 1 &rsqb; t m
Work as Uf≥UfmTime, time definite value ts=tm；
Step 2.3, carries out heat effect accumulation computing, obtains heat accumulation value M；
For the K moment, overexcitation instantaneous value is Uf(k): when overexcitation instantaneous value UfK () is less than inverse-time curve minima Time, heat accumulation value M resets；When overexcitation instantaneous value UfWhen () is more than inverse-time curve minima k, in conjunction with Uf(k) and step 2.2 The computing formula of the fitting of parabola curve obtained, is calculated instantaneous time definite value ts(k)；
Measuring △ t interval time (k)=t (the k)-t (k-1) calculated away from the last time, t (k) is the absolute time of current time Mark, t (k-1) is a upper absolute time mark calculating the moment；
Calculate heat accumulation value M: work as Uf(k) ＜ Uf0Time, M=0；Work as Uf(k)≥Uf0Time,Wherein, Uf0 First match point for inverse-time curve.
Step 2.4, judges to protect whether action according to heat accumulation value M: when M >=1, protection transmits and trips；As M < 1 Time, protection returns.
Using heat effect accumulation distinguished number to overcome cannot be the most anti-in comparison expression time, algorithm inverse time lag of routine Reflect the defect of too drastic magnetic value dynamic changing process, truly reflect the cumulative effect of history value in overexcitation dynamic changing process.
The above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art For Yuan, on the premise of without departing from the technology of the present invention principle, it is also possible to make some improvement and deformation, these improve and deformation Also should be regarded as protection scope of the present invention.

Claims (8)

1. for the commutation frequency measuring circuit of over-excitation protection, it is characterised in that: include power vd D, ground GND, operation amplifier Device A1, operational amplifier A 2, diode V1, diode V2, sampling resistor R1, sampling capacitance C1, resistance R2, resistance R3, resistance R4, resistance R5, resistance R6, resistance R7, filter resistance R8 and filter capacitor C2；Measured signal Vi connects the one of sampling resistor R1 End, the other end of R1 is respectively by sampling capacitance C1 ground connection GND, the positive input that is connected to operational amplifier A 1 by resistance R3 Hold, by resistance R6 and the positive input terminal of connection end operational amplifier A 2；The negative input end of operational amplifier A 1 respectively with two poles The negative pole of pipe V1 is connected with one end of resistance R4, and by resistance R2 ground connection GND, the outfan of operational amplifier A 1 is respectively with two The positive pole of pole pipe V1 is connected with the negative pole of diode V2；The positive pole of diode V2 is connected with the other end of resistance R4, and by electricity Resistance R5 is connected to the negative input end of operational amplifier A 2, and resistance R7 is by the negative input end of operational amplifier A 2 and operational amplifier A 2 Outfan link together；The outfan of operational amplifier A 2 is connected with output signal Vo by filter resistance R8, output letter Number Vo is by filter capacitor C2 ground connection GND.
Commutation frequency measuring circuit for over-excitation protection the most according to claim 1, it is characterised in that: resistance R2, Resistance R3, resistance R4, resistance R5, resistance R6, the resistance of resistance R7 meet following relationship: R2=R3=R4=R5=R6, R7 =2R2.
Commutation frequency measuring circuit for over-excitation protection the most according to claim 1, it is characterised in that: described measurement Circuit also includes that protection circuit, described protection circuit include stabilivolt VD1 and stabilivolt VD2, the positive pole of stabilivolt VD1 and voltage stabilizing The negative pole of pipe VD2 all junctions with sampling resistor R1 and sampling capacitance C1 are connected, and the negative pole of stabilivolt VD1 meets power vd D, surely Plus earth GND of pressure pipe VD2.
Commutation frequency measuring circuit for over-excitation protection the most according to claim 1, it is characterised in that: described measurement Circuit also includes that temperature-compensation circuit, described temperature-compensation circuit include anti-temperature coefficient electric capacity C3, anti-temperature coefficient electric capacity C4, Anti-temperature coefficient electric capacity C3 is connected in parallel with sampling capacitance C1, and anti-temperature coefficient electric capacity C4 is connected in parallel with filter capacitor C2.
5. over-excitation protection method, it is characterised in that comprise the following steps:
Step 1, accesses the commutation frequency measuring circuit described in any one of claim 1-4, described commutation frequency by measured signal The size of measured signal frequency is converted in the amplitude of alternating voltage by measuring circuit so that the amplitude of output voltage becomes with frequency Inverse ratio, meanwhile, described commutation frequency measuring circuit carries out fine all wave rectification to the waveform of output voltage, exports direct current after filtering Voltage signal, makes DC voltage value just become with overexcitation multiple value by adjusting resistance value corresponding in circuit with capacitance Ratio；
Step 2, uses and directly judges and indirectly judge that two kinds of methods determine and protect whether action.
Over-excitation protection method the most according to claim 5, it is characterised in that: directly determination methods is, uses comparator DC voltage value and setting voltage value being compared, when DC voltage value is more than setting voltage value, protection transmits and trips.
Over-excitation protection method the most according to claim 5, it is characterised in that: determination methods specifically includes following step indirectly Rapid:
Step 2.1, the direct current signal sampling producing step 1 obtains overexcitation instantaneous value Uf；
Step 2.2, discrete actual overexcitation inverse-time curve, obtain one group of definite value (Uf0,t0), (Uf1,t1) ... (Ufn, tn) ..., (Ufm,tm), and realize curve matching with multistage curve-parabola-fitting method, specific algorithm is as follows:
Work as Uf＜ Uf0Time, time definite value ts=t0；
Work as Ufn-1≤Uf＜ Ufn＜ Ufn+1, and during 1≤n ＜ m, time definite value tsComputing formula be:
t s = &lsqb; U f - Uf n &rsqb; * &lsqb; U f - Uf n + 1 &rsqb; &lsqb; Uf n - 1 - Uf n &rsqb; * &lsqb; Uf n - 1 - Uf n + 1 &rsqb; t n - 1 + &lsqb; U f - Uf n - 1 &rsqb; * &lsqb; U f - Uf n + 1 &rsqb; &lsqb; Uf n - Uf n - 1 &rsqb; * &lsqb; Uf n - Uf n + 1 &rsqb; t n + &lsqb; U f - Uf n &rsqb; * &lsqb; U f - Uf n - 1 &rsqb; &lsqb; Uf n + 1 - Uf n &rsqb; * &lsqb; Uf n + 1 - Uf n - 1 &rsqb; t n + 1
Work as Ufm-1≤Uf＜ UfmTime, time definite value tsComputing formula be:
t s = &lsqb; U f - Uf m - 1 &rsqb; * &lsqb; U f - Uf m &rsqb; &lsqb; Uf m - 2 - Uf m - 1 &rsqb; * &lsqb; Uf m - 2 - Uf m &rsqb; t m - 2 + &lsqb; U f - Uf m - 2 &rsqb; * &lsqb; U f - Uf m &rsqb; &lsqb; Uf m - 1 - Uf m - 2 &rsqb; * &lsqb; Uf m - 1 - Uf m &rsqb; t m - 1 + &lsqb; U f - Uf m - 2 &rsqb; * &lsqb; U f - Uf m - 1 &rsqb; &lsqb; Uf m - Uf m - 2 &rsqb; * &lsqb; Uf m - Uf m - 1 &rsqb; t m
Work as Uf≥UfmTime, time definite value ts=tm；
Step 2.3, carries out heat effect accumulation computing, obtains heat accumulation value M；
Step 2.4, judges to protect whether action according to heat accumulation value M: when M >=1, protection transmits and trips；When M < when 1, protects Protect return.
Over-excitation protection method the most according to claim 7, it is characterised in that described step 2.3 particularly as follows:
For the K moment, overexcitation instantaneous value is Uf(k): when overexcitation instantaneous value UfWhen () is less than inverse-time curve minima k, heat Accumulating value M resets；When overexcitation instantaneous value UfWhen () is more than inverse-time curve minima k, in conjunction with UfK () and step 2.2 obtain The computing formula of fitting of parabola curve, is calculated instantaneous time definite value ts(k)；
Measuring △ t interval time (k)=t (the k)-t (k-1) calculated away from the last time, t (k) is the absolute time mark of current time, t (k-1) it is a upper absolute time mark calculating the moment；
Calculate heat accumulation value M: work as Uf(k) ＜ Uf0Time, M=0；Work as Uf(k)≥Uf0Time,Wherein, Uf0For inverse time First match point of limit curve.
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