CN102841291A - Synchronous generator rotor turn-to-turn short circuit monitoring method based on excitation magnetic potential calculation - Google Patents

Abstract

The invention provides a synchronous generator rotor turn-to-turn short circuit monitoring method based on excitation magnetic potential calculation and belongs to the field of primary device relaying protection and online monitoring technology in an electric power system. The synchronous generator rotor turn-to-turn short circuit monitoring method is characterized in that first, phase voltage, phase current and stator leakage impedance of a generator are used to work out excitation magnetic potential in actual operation; second, according to exciting current on the same operating condition, excitation magnetomotive force which a normal exciting winding should generate can be calculated; and in normal operation, calculating results of two excitation magnetomotive force should be identical, but the actual excitation magnetomotive force can be smaller than the calculating result obtained according to the normal exciting winding when rotor turn-to-turn short circuit happens, and therefore a breakdown criterion is formed. An experiment that the rotor turn-to-turn short circuit happens to a typical synchronous generator in load operation condition indicates that the synchronous generator rotor turn-to-turn short circuit monitoring method can be used to achieve monitoring to rotor turn-to-turn short circuit faults and can be applied to synchronous generators which are not provided with the condition of installing branch current transformers.

Description

Synchronous generator rotor turn-to-turn short circuit monitoring method based on excitation magnetic potential calculating

Technical field

The invention belongs to power system main equipment relay protection and on-line monitoring technique field, relate in particular to a kind of synchronous generator rotor shorted-turn fault monitoring method of calculating based on excitation magnetic potential.

Background technology

Along with the fast development of electrical network and the continuous increase of generator single-machine capacity, people have proposed increasingly high requirement to the safe and reliable operation of generator.Rotor inter-turn short circuit is the frequent electric fault of generator; Slight turn-to-turn short circuit can not produce generator operation and have a strong impact on; If but fault continues development, can cause exciter current of generator to increase, output is idle reduces, vibrates harmful effect such as aggravation.It is the rotor ground fault fault that the short-circuit point local overheating also possibly make failure evolution, and stable operation brings grave danger to unit safety.

Field copper is born centrifugal force to cause mutual extrusion and the displacement distortion between winding, the thermal deformation of field copper, the local overheating that improper ventilation causes etc. is the major reason that causes generator rotor interturn short-circuit in the rotor rotation, and the fault that these reasons cause only just manifests when the generator actual condition moves usually to some extent.Therefore, realize the on-line monitoring and the protection of rotor interturn short-circuit fault are seemed particularly necessary.

Utilize the electric parameters in the generator operation to realize the real time on-line monitoring of rotor interturn short-circuit fault is not needed attachment device with protection, also do not need generator is transformed.The fault signature method for distilling of hydraulic generator rotor winding interturn short-circuit (publication number: CN102087329A) with the decision method of rotor of steam turbo generator shorted-turn fault position and the short circuit number of turn (publication number: promptly be that the stator branch out-of-balance current that produces during according to fault carries out malfunction monitoring and the short circuit number of turn and position judgment CN102044862A).

But because the neutral point of Chinese most large turbo-type generators is only drawn three terminals; The mounting condition that does not possess the branch current mutual inductor, feasible rotor interturn short-circuit fault monitoring method based on branch's out-of-balance current is restricted when being applied to large turbo-type generator.In order to improve the safe reliability of large turbo-type generator operation, should make great efforts to seek under the existence conditions on-line monitoring to the rotor inter-turn short circuit fault.

Summary of the invention

The objective of the invention is to provide a kind of on-line monitoring method of rotor interturn short-circuit, especially for the large turbo-type generator that does not possess branch current mutual inductor mounting condition for synchronous generator.

In order to improve the safe reliability of generator operation, the present invention proposes a kind of synchronous generator rotor turn-to-turn short circuit monitoring method of calculating based on excitation magnetic potential.The invention is characterized in that said method is carried out successively according to the following steps:

Step (1), calculating generator air gap electromotive force E _δ:

${\stackrel{\·}{E}}_{\mathrm{\δ}}=\stackrel{\·}{U}+\stackrel{\·}{I}(R+j{X}_{\mathrm{\σ}})$

Wherein:

With

Be respectively A phase voltage and electric current phasor, R and X _σBe respectively the resistance and the leakage reactance of the every phase of stator;

Step (2), calculating air-gap electromotive force E _δCorresponding air gap first-harmonic mmf F _δ:

At first look into the no-load characteristic table of generator, obtain E _δCorresponding staircase waveform rotor mmf amplitude F _f, because no-load characteristic is just often to record at rotor, E at this moment _δCorresponding air gap first-harmonic mmf size does

F _δ=k _fF _f

Wherein: k _fBe the magnetomotive waveform factor of rotor, its value is for the ratio of magnetomotive first-harmonic effective value with amplitude, and is relevant in epitrochanterian distribution situation with field coil, is the intrinsic parameter of generator,

The time Kongxiang vow on the figure F _δIn advance

90 °;

Step (3) is calculated stator three and is combined to armature magnetomotive force F _a:

$F_a=1.35\frac{{\mathrm{IN}}_1}{\mathrm{<figure-callout\; id="1"\; label="p\; k\; dp"\; filenames="2012103102690100003DEST\_PATH\_IMAGE001.png,2012103102690100003DEST\_PATH\_IMAGE002.png"\; state="\{\{state\}\}">p</figure-callout>}}{k}_{\mathrm{dp}}{1}_{}$

Wherein: N ₁Be the stator winding number of turn that whenever is in series, k _Dp1Be stator first-harmonic winding coefficient, p is a number of pole-pairs,

The time Kongxiang vow on the figure F _aWith A phase current phasor

Direction is identical;

Step (4) obtains generator space-time phasor diagram as shown in Figure 1, and then the size of the excitation mmf fundametal compoment when trying to achieve generator actual motion F _F1':

${\mathrm{<figure-callout\; id="1"\; label="F\; f"\; filenames="2012103102690100003DEST\_PATH\_IMAGE001.png,2012103102690100003DEST\_PATH\_IMAGE002.png"\; state="\{\{state\}\}">F</figure-callout>}}_f^1=|F_{\mathrm{\&delta;}}-F_a|$

Step (5), the rotor first-harmonic excitation mmf when calculating generator and normally move according to the exciting current DC component of actual measurement:

${\mathrm{<figure-callout\; id="1"\; label="F\; f"\; filenames="2012103102690100003DEST\_PATH\_IMAGE001.png,2012103102690100003DEST\_PATH\_IMAGE002.png"\; state="\{\{state\}\}">F</figure-callout>}}_f=\frac{1}{2}{k}_f{N}_f{I}_f$

Wherein: N _fBe the total number of turns of field copper, I _fExciting current DC component for actual measurement;

Step (6), carry out fault judgement:

if

; Think that then there is shorted-turn fault in the generator amature winding, the alert signal of transmitting messages;

Wherein: σ>0 is error coefficient; Should adjust to it according to the normal operating condition of actual generator, when guaranteeing normally to move under the various operating modes .

Synchronized sampling three-phase voltage, electric current and exciting current data were carried out real-time judgement when above-mentioned steps can be based on the generator actual motion, the off-line analysis after the above-mentioned data that also can be applicable to sample, and theory diagram of the present invention is as shown in Figure 2.

The experiment of the rotor inter-turn short circuit that takes place through to the operation of representative synchronization generator loading the time shows that the method that the present invention proposes can the sensitive rotor inter-turn short circuit that reaction took place.Use this method and can realize effective monitoring synchronous generator rotor winding interturn short-circuit fault.

Description of drawings

Fig. 1 is the space-time phasor diagram of generator.

Fig. 2 is a theory diagram of the present invention.

Fig. 3 is the magnetomotive variation of excitation before and after the implicit pole synchronous motor rotor inter-turn short circuit.

The field copper of Fig. 3 (a) implicit pole synchronous motor.

The excitation mmf of the normal operation of Fig. 3 (b) implicit pole synchronous motor.

Excitation mmf during Fig. 3 (c) implicit pole synchronous motor rotor inter-turn short circuit.

Fig. 4 is each tap position of A1552 model machine rotor and the number of turn.

Embodiment

At first briefly introduce ultimate principle of the present invention.

Implicit pole synchronous motor with shown in Fig. 3 (a) is an example, and the field copper of this motor is to be in series by 11', 22', 33', four groups of coils of 44'.Field copper just often, the magnetomotive waveform of excitation shown in Fig. 3 (b), the amplitude F of staircase waveform _f=N _fI _f/ 2, N wherein _fBe field copper total number of turns, I _fBe exciting current.This staircase waveform magnetic potential is carried out Fourier decomposition, can obtain the magnetomotive amplitude F of first-harmonic _F1=k _fF _f

Suppose that the part turn-to-turn short circuit takes place winding 11', the excitation mmf after the short circuit distributes shown in Fig. 3 (c), since the minimizing of field copper effective turn, the magnetomotive amplitude F of first-harmonic excitation after the short circuit _F1' with inevitable F less than the normal field copper calculating of basis _F1If the exciting current after the short circuit is I _f, then

${\mathrm{<figure-callout\; id="1"\; label="F\; f"\; filenames="2012103102690100003DEST\_PATH\_IMAGE001.png,2012103102690100003DEST\_PATH\_IMAGE002.png"\; state="\{\{state\}\}">F</figure-callout>}}_f^1<{\mathrm{<figure-callout\; id="1"\; label="F\; f"\; filenames="2012103102690100003DEST\_PATH\_IMAGE001.png,2012103102690100003DEST\_PATH\_IMAGE002.png"\; state="\{\{state\}\}">F</figure-callout>}}_f=\frac{1}{2}{k}_f{N}_f{I}_f$

F ＇ when therefore, normally moving in theory _F1Should equal F _F1, and the relation of following formula will be arranged during rotor inter-turn short circuit, can realize the rotor inter-turn short circuit failure judgment thus.

For verifying validity of the present invention, typical A 1552 model machines have been carried out the field copper turn-to-turn short circuit experiment of the different numbers of turn.The A1552 model machine is 1 pair of utmost point, 12kW synchronous generator; This model machine field copper is except that first, terminal 2 the tap; 5 taps have also been drawn in addition in inside; These 7 taps link to each other with 7 slip rings respectively, and slip ring is linked on the external cabling terminal through brush again, and the position of each tap and the corresponding number of turn are as shown in Figure 4.

Experimental data when table 1 is networked load for this model machine before and after field copper 4-6 (short circuit 135 circles), 2-4 (short circuit 231 circles) the tap generation shorted-turn fault,

in the table is the power-factor angle between phase voltage and the phase current.

Experimental data before and after the table 1 A1552 model machine rotor inter-turn short circuit fault

According to summary of the invention, to the first-harmonic excitation mmf F during the generator actual motion before and after two kinds of short troubles _F1' calculate, and the rotor first-harmonic excitation mmf F when normally moving with generator that Distribution calculation according to exciting current DC component and the rotor winding of actual measurement goes out _F1Compare, result of calculation is seen table 2.

The comparison of excitation magnetic potential before and after the table 2 A1552 model machine rotor inter-turn short circuit fault

Experimental data when table 3 is this model machine strip resistance load before and after field copper 4-6, the 2-4 tap generation shorted-turn fault.

Experimental data before and after the table 3 A1552 model machine strip resistance load rotor inter-turn short circuit fault

Equally, to the first-harmonic excitation mmf F during the generator actual motion before and after two kinds of short troubles _F1' and the rotor first-harmonic excitation mmf F of hypothesis generator when normally moving _F1Compare, see table 4.

The comparison of excitation magnetic potential before and after the rotor inter-turn short circuit fault during load of table 4 A1552 model machine strip resistance

Visible from table 2 and table 4, as to calculate when normally moving before fault F _F1And F _F1' not exclusively equate that 3% the error of having an appointment can be taken as 0.05 with error coefficient σ.The F that calculates after the fault _F1And F _F1' deviation all enlarges markedly, and can realize effective monitoring.

Through top calculating and analysis, explained that the method that the present invention proposes can realize the monitoring to the synchronous generator rotor shorted-turn fault, and only need use in the computation model and receive the method for operation to influence very little stator leakage reactance parameter, guaranteed the reliability of monitoring; And only need gather three-phase current, three-phase voltage and exciting current in the actual motion, be applicable to the generator of no branch (group) current transformer mounting condition.

Claims (1)

1. the synchronous generator rotor turn-to-turn short circuit monitoring method of calculating based on excitation magnetic potential is characterized in that said method is carried out successively according to the following steps:

Step (1), calculating generator air gap electromotive force E _δ:

${\stackrel{\&CenterDot;}{E}}_{\mathrm{\&delta;}}=\stackrel{\&CenterDot;}{U}+\stackrel{\&CenterDot;}{I}(R+j{X}_{\mathrm{\&sigma;}})$

Wherein:

With

Be respectively A phase voltage and electric current phasor, R and X _σBe respectively the resistance and the leakage reactance of the every phase of stator;

Step (2), calculating air-gap electromotive force E _δCorresponding air gap first-harmonic mmf F _δ:

At first look into the no-load characteristic table of generator, obtain E _δCorresponding staircase waveform rotor mmf amplitude F _f, because no-load characteristic is just often to record at rotor, E at this moment _δCorresponding air gap first-harmonic mmf size does

F _δ=k _fF _f

Wherein: k _fBe the magnetomotive waveform factor of rotor, its value is for the ratio of magnetomotive first-harmonic effective value with amplitude, and is relevant in epitrochanterian distribution situation with field coil, is the intrinsic parameter of generator,

The time Kongxiang vow on the figure F _δIn advance

90 °;

Step (3) is calculated stator three and is combined to armature magnetomotive force F _a:

$F_a=1.35\frac{{\mathrm{IN}}_1}{p}{k}_{\mathrm{dp}1}$

Wherein: N ₁Be the stator winding number of turn that whenever is in series, k _Dp1Be stator first-harmonic winding coefficient, p is a number of pole-pairs,

The time Kongxiang vow on the figure F _aWith A phase current phasor

Direction is identical;

Step (4) obtains generator space-time phasor diagram as shown in Figure 1, and then the size of the excitation mmf fundametal compoment when trying to achieve generator actual motion F _F1':

$F_{f1}^{\&prime;}=|F_{\mathrm{\&delta;}}-F_a|$ ；

Step (5), the rotor first-harmonic excitation mmf when calculating generator and normally move according to the exciting current DC component of actual measurement:

$F_{f1}=\frac{1}{2}{k}_f{N}_f{I}_f$

Wherein: N _fBe the total number of turns of field copper, I _fExciting current DC component for actual measurement;

Step (6), carry out fault judgement:

if

; Think that then there is shorted-turn fault in the generator amature winding, the alert signal of transmitting messages;

Wherein: σ>0 is error coefficient; Should adjust to it according to the normal operating condition of actual generator, when guaranteeing normally to move under the various operating modes .

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