CN103245820A - Stator-side out-of-balance current monitoring method for turn-to-turn short circuit in hydraulic generator rotor - Google Patents

Abstract

The invention relates to a stator-side out-of-balance current monitoring method for turn-to-turn short circuit in a hydraulic generator rotor. The method adopts a super-long data window technology, and data window length is automatically regulated according to the number of pole-pairs of a generator so as to realize accurate computation of fractional harmonics of different generator sets. According to the invention, a brand-new algorithm is adopted to accurately compute effective value of fault circulating current, which effectively filters out first harmonics, third harmonics and fifth harmonics of out-of-balance current in normal operation and greatly improves sensitivity in monitoring turn-to-turn short circuit fault in the rotor winding of the generator.

Description

Hydraulic generator rotor turn-to-turn short circuit stator side out-of-balance current monitoring method

Technical field

The present invention relates to a kind of hydraulic generator rotor turn-to-turn short circuit stator side out-of-balance current monitoring method.

Background technology

The scholar of domestic colleges and universities makes many theoretic researchs to the generator rotor interturn short-circuit fault, but at present aspect the motor rotor winding interturn short-circuit fault, only aspect offline inspection, there is relevant standard to use for reference, a technical manual formation is not clearly also arranged aspect on-line monitoring.The on-line monitoring of generator rotor interturn short-circuit fault, early prevention and diagnosis are very necessary, but generator amature shorted-turn fault monitoring device does not all have the mature and reliable Related product at present both at home and abroad, generator amature shorted-turn fault monitoring device is all thought because the signals collecting difficulty is bigger in most of generating plant, and the possibility of making the practicality product is little.

Behind the hydraulic generator rotor winding generation shorted-turn fault; each branch current of stator neutral point can produce the out-of-balance current based on the mark subharmonic; split the out-of-balance current of phase transverse differential protection and zero-sequence current type transverse differential protection fully in theory mainly based on the mark subharmonic, do not contain fundametal compoment.The mark subharmonic that produces is mainly relevant with the number of pole-pairs P of generator, and 1/P, 2/P......N/P(N can occur is natural number) etc. the harmonic wave of number of times.

Detecting the out-of-balance current based on the mark subharmonic exactly, is the necessary guarantee that realizes the monitoring of generator rotor interturn short-circuit On-line Fault.Be example with every power frequency cycle N=32 point sampling, power generator electrode logarithm P=30; simulating the partial fraction subharmonic that comprises in the tested electric current has: 5Hz, 10Hz, 20Hz, 30Hz, 40Hz; integral frequency harmonizing wave has: 50Hz, 150Hz, 250Hz; each harmonic current peak value is 10mA; Fig. 1 is that the employing power frequency is that the master data window calculates and emulation the fault current effective value that contains above-mentioned harmonic wave; as can be seen, Chang Gui Microcomputer Protection sampled data window length can't accurate Calculation based on the out-of-balance current of mark subharmonic.

In order more accurately to calculate the out-of-balance current effective value based on the mark subharmonic, it is master data window length that Fig. 2 adopts N * P, equally with every power frequency cycle N=32 point sampling, power generator electrode logarithm P=30 is example, the fault current effective value is calculated and emulation, as can be seen from Figure 2, this method can calculate the total effective value that comprises each harmonic out-of-balance currents such as first-harmonic exactly, and (the total effective value theoretical value of out-of-balance current that comprises each harmonic is 20mA, mark subharmonic non-equilibrium flow effective value theoretical value is 15.81mA), but the first-harmonic in can't the filtering out-of-balance current, third harmonic, quintuple harmonicss etc. cause the sensitivity that realizes the generator rotor interturn short-circuit malfunction monitoring to seriously influence.

Summary of the invention

The purpose of this invention is to provide a kind of hydraulic generator rotor turn-to-turn short circuit stator side out-of-balance current detection method, in order to solving first-harmonic, third harmonic and the quintuple harmonics of prior art in can't the filtering out-of-balance current, thus the problem that the sensitivity of malfunction monitoring is impacted.

For achieving the above object, the solution of the present invention is: a kind of hydraulic generator rotor turn-to-turn short circuit stator side out-of-balance current detection method, and step is as follows:

(1) according to the power generator electrode logarithm, by formula

Determine master data window length, and by formula M=N * P determines master data window sampling number, wherein, T is data window length, and P is number of pole-pairs, and M is master data window sampling number, and N is ripple sampling number weekly;

(2) according to described data window length T, calculate the total effective value of out-of-balance current that comprises first-harmonic, each integral frequency harmonizing wave and each mark subharmonic;

(3) carry out analog quantity sampling and data preservation according to master data window sampling number M, and according to sampled data the total effective value of out-of-balance current is carried out discretize and handle, calculate the out-of-balance current effective value of each mark subharmonic and first-harmonic, third harmonic, quintuple harmonics;

(4) the total effective value of the out-of-balance current of discretize is deducted first-harmonic, third harmonic and quintuple harmonics out-of-balance current effective value, draw the total effective value of mark subharmonic out-of-balance current;

(5) according to the total effective value of mark subharmonic out-of-balance current, each mark subharmonic out-of-balance current effective value of calculating the hydraulic generator rotor shorted-turn fault is monitored.

Further, step (2) adopts the root-mean-square value method to calculate the total effective value of out-of-balance current that comprises each harmonic, that is: With its discrete turning to:

Wherein, I _kBe out-of-balance current discrete sampling value, i _tBe the out-of-balance current instantaneous value.

Further, adopt in the step (3) fourier algorithm based on the master data window to calculate the out-of-balance current effective value of each mark subharmonic and first-harmonic, third harmonic, quintuple harmonics, that is:

Wherein, $I_{n.\mathrm{real}}=\frac{2}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}[i_k\·\cos (n\·k\frac{2\mathrm{\π}}{M})],$ $I_{n.\mathrm{imag}}=\frac{2}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}[i_k\·\sin (n\·k\frac{2\mathrm{\π}}{M})],$ N is natural number, I _N.realBe the real part of n/P subharmonic, I _N.imagImaginary part for the n/P subharmonic.

Further, the method for the total effective value of calculating mark subharmonic out-of-balance current is:

Wherein, I _{Fault circulation}Be the total effective value of mark subharmonic out-of-balance current, I _{Σ '}Be the total effective value that comprises each harmonic out-of-balance currents such as first-harmonic of discretize, I _P/PBe first-harmonic, I _3P/PBe third harmonic, I _5P/PBe quintuple harmonics.

The beneficial effect that the present invention reaches: the present invention adopts the ultra-long data window setting technique, according to the power generator electrode logarithm, automatically adjust data window length, realize the accurate calculating of each mark subharmonic of different units and fault circulation effective value, and first-harmonic, third harmonic, the quintuple harmonics of effective normal out-of-balance current in service of filtering, measure the out-of-balance current based on the mark subharmonic exactly, greatly improved the sensitivity of generator rotor interturn short-circuit malfunction monitoring.

Description of drawings

Fig. 1 is to be the fault circulation effective value calculating analogous diagram of master data window with the power frequency;

Fig. 2 is to be the fault circulation effective value calculating analogous diagram of master data window with N * P;

Fig. 3 adopts method of the present invention to the effective value calculating analogous diagram of fault circulation.

Embodiment

The present invention will be further described in detail below in conjunction with accompanying drawing.

The present invention adopts brand-new monitoring based on the method for the out-of-balance current of mark subharmonic, first-harmonic, third harmonic, quintuple harmonics in the filtering out-of-balance current fully, measure the out-of-balance current based on the mark subharmonic exactly, concrete steps are as follows:

At first, according to power generator electrode logarithm P specified data window length, that is:

$T=\frac{1}{(\frac{1}{P}\×50)}=\frac{P}{50}=0.02P$ And system determines master data window sampling number M=N * P according to the definite value of the power generator electrode logarithm P that sets and the sample frequency of system itself, wherein, N is the sampling number of every power frequency period, and P is the power generator electrode logarithm, M is master data window sampling number, and T is master data window length.

Secondly, carry out analog quantity sampling and data preservation according to master data window sampling number M, use the root-mean-square value method to calculate the total effective value of out-of-balance current:

And utilize sampled data, the total effective value of the out-of-balance current that calculates is carried out discretize, that is: Wherein, I _tBe out-of-balance current instantaneous value, I _kBe out-of-balance current discrete sampling value, the total effective value of out-of-balance current that calculates this moment comprises the mark subharmonic out-of-balance current effective value of failure message, the out-of-balance current effective value of the first-harmonic when also comprising normal operation the, third harmonic, quintuple harmonics.

The 3rd, calculate the coefficient of a series of fourier algorithms corresponding to k according to the master data window sampling number M of power generator electrode logarithm correspondence, that is:

Wherein, k is natural number, and the value of k is to carry out determining behind the l-G simulation test according to the wiring of generator unit stator winding.

The 4th, utilize fourier algorithm to calculate real part and the imaginary values of the needed mark subharmonic of analog quantity out-of-balance current successively, that is:

$I_{n.\mathrm{imag}}=\frac{2}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}[i_k\·\sin (n\·k\·\frac{2\mathrm{\π}}{M})],$

$I_{n/P}=\sqrt{I_{n.\mathrm{real}}^2+I_{n.\mathrm{imag}}^2}$

Thereby calculate the out-of-balance current effective value of n/P subharmonic, that is:

$I_{n/p}=\sqrt{I_{n.\mathrm{real}}^2+I_{n.\mathrm{imag}}^2}$

Wherein, I _N.realBe the real part of n/P subharmonic out-of-balance current, I _N.imagBe the imaginary part of n/P subharmonic out-of-balance current, n is natural number.

Computing method according to n/P subharmonic out-of-balance current effective value, when n gets different values, calculating 1/P, 2/P......n/P(n respectively is natural number) the out-of-balance current effective value of subharmonic, calculate the P/P(first-harmonic simultaneously), the 3P/P(third harmonic), the 5P/P(quintuple harmonics) subharmonic out-of-balance current effective value.

The 5th, because $I_{{\mathrm{\Σ}}^{\′}}=\sqrt{\frac{1}{M}\underset{k=0}{\overset{M-1}{\mathrm{\Σ}}}{i}_k^2}=\sqrt{I_{I/P}^2+I_{2/P}^2+I_{3/P}^2+\·\·\·+I_{P/P}^2+I_{3/P}^2+I_{5P/P}^2+\·\·\·},$ The computing method of total mark subharmonic out-of-balance current effective value are as can be known:

Wherein, I _{Fault circulation}Be the total effective value of mark subharmonic out-of-balance current, I _{Σ '}For comprising total effective value of each harmonic out-of-balance currents such as first-harmonic, I _P/PBe first-harmonic, I _3P/PBe third harmonic, I _5P/PBe quintuple harmonics.

At last, according to the total effective value of mark subharmonic out-of-balance current and each mark subharmonic out-of-balance current effective value the generator amature shorted-turn fault is monitored.

As Fig. 3, it is the analogous diagram that adopts method of the present invention that the effective value of fault circulation is calculated, the total effective value theoretical value of out-of-balance current that comprises each harmonic is 20mA, the total effective value theoretical value of mark subharmonic out-of-balance current is 15.81mA, as can be seen from Figure 3, first-harmonic, third harmonic and the quintuple harmonics of method of the present invention in can the filtering out-of-balance current, calculate the total effective value of mark subharmonic current in the out-of-balance current exactly, improved the sensitivity of generator amature shorted-turn fault monitoring greatly.

Claims (4)

1. hydraulic generator rotor turn-to-turn short circuit stator side out-of-balance current monitoring method is characterized in that step is as follows:

(1) according to the power generator electrode logarithm, by formula

Determine master data window length, and by formula M=N * P determines master data window sampling number, wherein, T is data window length, and P is number of pole-pairs, and M is master data window sampling number, and N is ripple sampling number weekly;

(2) according to described data window length T, calculate the total effective value of out-of-balance current that comprises first-harmonic, each integral frequency harmonizing wave and each mark subharmonic;

(3) carry out analog quantity sampling and data preservation according to master data window sampling number M, and according to sampled data the total effective value of out-of-balance current is carried out discretize and handle, calculate the out-of-balance current effective value of each mark subharmonic and first-harmonic, third harmonic, quintuple harmonics;

(4) the total effective value of the out-of-balance current of discretize is deducted first-harmonic, third harmonic and quintuple harmonics out-of-balance current effective value, draw the total effective value of mark subharmonic out-of-balance current;

(5) according to the total effective value of mark subharmonic out-of-balance current, each mark subharmonic out-of-balance current effective value of calculating the hydraulic generator rotor shorted-turn fault is monitored.

2. hydraulic generator rotor turn-to-turn short circuit stator side out-of-balance current monitoring method according to claim 1 is characterized in that, step (2) adopts the root-mean-square value method to calculate the total effective value of out-of-balance current that comprises each harmonic, that is:

With its discrete turning to:

Wherein, I _kBe out-of-balance current discrete sampling value, i _tBe the out-of-balance current instantaneous value.

3. hydraulic generator rotor turn-to-turn short circuit stator side out-of-balance current monitoring method according to claim 2, it is characterized in that, adopt in the step (3) fourier algorithm based on the master data window to calculate the out-of-balance current effective value of each mark subharmonic and first-harmonic, third harmonic, quintuple harmonics, that is:

Wherein, $I_{n.\mathrm{real}}=\frac{2}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}[i_k\·\cos (n\·k\frac{2\mathrm{\π}}{M})],$ $I_{n.\mathrm{imag}}=\frac{2}{M}\underset{k=1}{\overset{M}{\mathrm{\Σ}}}[i_k\·\sin (n\·k\·\frac{2\mathrm{\π}}{M})],$ N is natural number, I _N.realBe the real part of n/P subharmonic, I _N.imagImaginary part for the n/P subharmonic.

4. hydraulic generator rotor turn-to-turn short circuit stator side out-of-balance current monitoring method according to claim 3 is characterized in that, the method for calculating the total effective value of mark subharmonic out-of-balance current is:

Wherein, I _{Fault circulation}Be the total effective value of mark subharmonic out-of-balance current, I _{Σ '}Be the total effective value that comprises each harmonic out-of-balance currents such as first-harmonic of discretize, I _P/PBe first-harmonic, I _3P/PBe third harmonic, I _5P/PBe quintuple harmonics.

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