Flux Probe

Experience of a Flux Probe User

Relu Ilie The Israel Electric Corporation Ltd.,

Email [email protected].

Abstract - The flux probe periodic on-line testing is a widely recognized method for rotor shorted turns detection in turbo-generators and it is justified by field winding insulation failures, mostly experienced in older peak regime machines.

The drawback of the flux probe test is that, for sensitivity reasons, it should be performed at various unusual or unpredictable loads that do not fit optimal unit loading. Consequently, this test is not easily accepted by load dispatcher or operation personnel.

The main goal of this paper is to propose a simple computational method, based on minimum input data, intended to determine in advance the generator loads suitable for flux probe readings. The paper originally explains the flux probe operation starting from synchronous machine principles and specifies the calculation mode. The accuracy of presented solution is then estimated versus field data for different generators.

The proposed method has been thoroughly verified and proves promising results. It can be very easily implemented, leading to better test preparation, faster flux probe readings and minimum impact on normal unit operating conditions.

Additionally, the paper presents further useful aspects concerning installing and using flux probe equipment.

All the described issues have been experienced and successfully implemented at Israel Electric Corporation (IECo).

I. INTRODUCTION HE shorted turns (turn-to-turn short-circuits) in turbo-generator field windings are generally the result of rotor insulation failures due to various causes [1]. As units age, shorted turn problems become more probable. The stresses involved in each start / stop cycle contribute to shorted turns development, especially for machines activated daily in two-shift mode.

Shorted turns cause higher field currents and temperatures than previously experienced. Common effects of field shorted turns are excessive vibrations due to rotor thermal unbalance, which in severe conditions may impose generator reactive load restrictions.

Several shorted turn detection methods have been proposed and tested over the years [2]. The flux probe method main advantage is that it monitors the on-line generator, the rotor components being stressed at speed and load by real forces and

temperatures. Moreover, the flux probe indicates the slots

containing inter-turn defects and allows an approximation of the number of short-circuited turns.

II. SYNCHRONOUS MACHINE BASICS At any steady-state load, the cylindrical-rotor synchronous

generator is described by the phasors diagram from Fig. 1 (armature winding resistance neglected). Magnetic flux density rotating spatial phasors are shown beside voltage phasors and considered initially sinusoidal in time.

The terminal phase voltage V is assumed to be at zero angle for reference. The rotating field flux BF induces in the stator winding an excitation voltage E proportional to dBF/dt (phasor E lags BF by 90). The armature reaction flux BI is in phase with the load current I. The resultant air-gap flux density BR is the vectorial sum of BF and BI. BR induces the total air-gap magnetizing voltage EM, proportional to dBR/dt (phasor EM lags BR by 90).

The synchronous reactance X is composed of the armature leakage reactance XL and the armature self reactance XS.

The power-factor angle was noted with , positive for over-excited operation and negative in under-excited regime.

E leads V by the internal electrical load angle , intensively used in stability studies. However, this paper deals meanly with the angular displacement ' by which E leads EM. By the same spatial angle ' the field pole longitudinal axis (BF phasor) leads the resultant air-gap flux axis (BR). The technical literature often neglects the difference between and ', but for the present paper purpose this distinction is important.

According to Fig. 1 and assuming that base quantities are generator rated phase voltage V and current I, the load angle can be calculated from (1) using per-unit quantities:

tan = XIcos / (V + XIsin). (1)

The angular displacement ' is smaller than by a

decrement (- ') due to leakage reactance, resulting from:

tan(-') = XLIcos / (V + XLIsin). (2) In actual quantities, (1) becomes:

tan = XP / (V2 + XQ), (3)

T

Iris Rotating Machine Conference 1 June 2007, San Antonio, TX

E

IV

'

'jX I

B F

B I

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E M jX L I

jX S I


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40 85 130 175 220 265 310 355 400 445 490

Degrees

pu

Fig. 1. Phasors diagram for 133.75MVA, 11.5kV, 2 poles, 50Hz generator, loaded @ 70MW, 30MVAR.

X being the synchronous reactance in , P and Q the active respectively reactive three-phase generator load in MW and MVAR, V the generator line voltage in kV.

The cylindrical-rotor flux BF has actually a trapezoidal form due to its winding distribution in slots, the maximum being located in the centerline of rotor pole and the zero value in the quadrature axis (midline between the two largest coils). Obviously, this flux rotates with the rotating field. For a two-pole 50Hz machine, one complete rotor rotation lasts 20ms and covers 360 electrical degrees.

For the particular case of no-load and excitation applied, Fig. 2 shows the BR curve, identical to BF because there is no armature reaction. The zero BF value coincides with zero BR, i.e. the angular displacement ' is null. At whatever load as in Fig. 3, the armature reaction flux BI (assumed sinusoidal like the current) is summed point-by-point to BF in order to obtain the resultant air-gap flux. BR zero value is now shifted behind the rotor quadrature axis (BF zero value) by an angle equal to the angular displacement '.

Resultant air-gap flux density Total air-gap magnetizing voltage

-2.45

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40 85 130 175 220 265 310 355 400 445 490

Degrees

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Rotating field flux density Armature reaction flux density Resultant air-gap flux density Total air-gap magnetizing voltage

Fig. 2. Calculated flux density and magnetizing voltage curves for 133.75MVA, 11.5kV, 2 poles, 50Hz generator, @ no-load.

Fig. 2 and Fig. 3 show also the total magnetizing voltage

EM, obtained by graphical derivation of resultant flux BR. This data will be used in the context of flux probe explanations.

III. FLUX PROBE PRINCIPLES The flux probe is in fact a small search coil located in the

generator air-gap. The voltage induced in this coil (flux probe data) depends by the rate-of-change of magnetic flux radial components detailed below.

Primarily, the flux probe is sensitive to the rate-of-change of main air-gap flux BR, similar to the armature winding as explained before. The voltage induced in the flux probe (similar to EM induced in the stator winding) is proportional to dBR/dt. Consequently, the integration of the flux probe data by suitable software permits to obtain the total flux BR curve and zero BR angle [3], [4].

Secondarily, the flux probe is located close enough to rotor surface to be sensitive also to the rate-of-change of its teeth tip leakage flux. Fig. 4 shows two adjacent rotor slots, with normal non-magnetic wedges, and their leakage flux paths. The radial fundamental component of this leakage flux alternates around the rotor surface, and a voltage proportional to its negative derivative is induced in the flux probe. Then, the flux probe data exhibit voltage peaks in front of rotor slot centerlines and valleys corresponding to rotor teeth, as shown in Fig. 5 and Fig. 6. The midline between the two largest coils peaks (coils #7 in Fig. 5 and Fig. 6) represents the location of rotor quadrature axis, i.e. zero BF angle.

Showing both angles were BF and BR are null, the flux probe permits an estimation of their difference, i.e. the angular displacement ', although this is not its declared purpose.

Fig. 3. Calculated flux density and magnetizing voltage curves for 133.75MVA, 11.5kV, 2 poles, 50Hz generator, loaded @ 70MW, 30MVAR.

Radial component of tooth tip leakage flux

Flux probe data induced by leakage flux

Fig. 4. Rotor tooth tip leakage flux and flux probe data component.

The main goal of the flux probe is achieved by the fact that

the voltage induced in front of each slot by the rotor leakage flux is proportional to the ampere-turns of the embedded coil. Consequently, a reduced voltage is observed when shorts occur in that coil. This principle permits comparing adjacent slots of the same pole and diametrically opposite slots of different poles, leading to shorted turn detection.

The generator air-gap main flux is in fact an undesired noise for flux probe readings that alters the useful slot leakage flux data (mainly by teeth saturation) [3]. The shorted turns detection sensitivity is highest when the background main flux is negligible, i.e. when the slot centerline of any particular tested coil is located at zero BR angle. Fig. 7 shows zooms of flux probe data exemplifying this fact: the shorted turns in slots #2, #4 of one pole and #3 of opposite pole are very prominent in the upper reading for zero BR line close to slot #3, but almost invisible when zero BR is aligned with slot #6 (bottom curves). (Fig.7 shows flux probe data conveniently inverted and aligned to facilitate peak magnitude comparison between poles.)

Fig. 5. Actual measured flux probe data (GeneratorTech, Inc. software) for 133.75MVA, 11.5kV, 2 poles, 50Hz generator, @ no-load.

One solution to this drawback is obvious but difficult to

implement: performing the shorted turn test when the generator is short-circuited and the field fundamental flux is essentially cancelled by the armature reaction [5].

A more practical solution results from the above explanation of generator basics: monitoring of each field winding coil by slot alignment with zero flux means shifting BF angle relatively to BR, i.e. changing the angular displacement '. According to (3), this can be performed easily by choosing different MW and MVAR loads during generator operation. Larger angles can be obtained increasing the generator active load or decreasing its reactive load. Highest angle values can be usually achieved at full MW and under-excited (negative) reactive loads.

Ignoring slot leakage flux harmonics, Fig. 2 vs. Fig. 5 and Fig. 3 vs. Fig. 6 show good EM and BR waveform correlation between calculated curves and actual measured flux probe data. This is a promising conclusion that will be quantitatively verified below.

IV. FLUX PROBE PRACTICAL CONSIDERATIONS In order to shift the zero flux line, the manufacturers

recommend performing 5 to 12 incremental tests from zero to full MW load, mostly at unity power-factor [6], [7], [8].

For peak machines like two-shift operated gas turbines, the flux probe data can be easily accumulated during the daily normal starting and loading. Testing large base load generators is more difficult: some low load data can be obtained at synchronization, but generally the testing sequence is likely contradictious to optimized generation and requires lengthy coordination between the test performer and the load dispatcher. In addition, the recommended equal load increments do not exactly meet the zero flux requirements and extreme minimum / maximum loads may be unavailable due to operational reasons.

Fig. 6. Actual measured flux probe data (GeneratorTech, Inc. software) for 133.75MVA, 11.5kV, 2 poles, 50Hz generator, @ 70MW, 30MVAR.


Fig. 7. Actual measured flux probe data zoom (GeneratorTech, Inc. software)

for 647MVA, 22kV, 2 poles, 50Hz generator, @ two different loads. Solutions to these disadvantages appear in literature in the

form of sophisticated flux measurements systems performing some degree of automated testing and continuous collection of data [9], including even an algorithm to detect changes in zero flux points [10]. There are still problems that these systems do not solve, like testing at unusual loads e.g. negative MVAR; in fact, readings in under-excited regimes are especially important allowing accurate testing of the smallest coils (that have maximum impact to thermal sensitivity).

This paper goal is to establish a synchronous machine model able to anticipate with sufficient accuracy the MW/MVAR loads required for a given angular displacement (i.e. for test sensitivity in a given slot). If feasible, the solution will permit selecting for tests those specific loads that are enough close to the optimal regime and easily accepted by operation personnel.

V. ANGULAR DISPLACEMENT CALCULATION As a first step, the author looked for a model to calculate the

angular displacement '. An imposed requirement was to use a simple model based only on a few easy to obtain machine rated data (like MVA, terminal voltage, synchronous reactance). The operational values read during flux probe measurements (active and reactive loads, actual voltage) were

input to the calculation routine. The calculated angular displacement ' was thus compared with the measured one in order to verify the correctness of the used algorithm.

The calculation of the internal angle can be a laborious process, some aspects of which being described below.

In addition to generator loads dependence as stated above, (3) shows that angle also changes with the generator terminal voltage. The author preferred to use the actual voltage on main transformer high voltage side, because the system voltage profile is easier to predict for the testing schedule. According to [11], the generator voltage results solving (4) in actual complex quantities (transformer resistance neglected):

VS = V / kT jkTXT (P jQ) / V, (4)

VS being the system line voltage in kV, kT the main transformer ratio at the actual tap and XT the transformer reactance in calculated at high voltage side. (The accurate power values in (4) should be P and Q diminished by unit auxiliaries loads, but this precision is not considered.)

According to (3), also depends on generator synchronous reactance. The main difficulty of the model is the representation of steady-state saturation, which decreases the reactance depending on the generator magnetization curve and leads to lower internal angle value. An additional complication is that references usually deal with load angle calculation, whereas the flux probe indicates the angular displacement ' (which differs from by the amount done by (2)).

Various saturation representation methods have been proposed by numerous papers, the more accurate ones unfortunately needing extensive computations and not commonly available generator information. The simplest "standard" method described in [12] considers that XS value is affected by machine saturation while XL remains roughly constant, uses one (direct axis) saturation factor and requires the knowledge of the generator magnetization curve and leakage reactance. A more accurate method from [12] requires to know also the quadrature axis unsaturated reactance and its own magnetization curve (normally different than d-axis one). Further, other methods take into consideration the cross-coupling reactance between d and q axes. The required input data for these calculations are not usually available from manufacturers and can be determined only by special tests.

The author intensively tried to use different calculation methods looking for accuracy, computation simplicity and input data availability. The various methods described in literature led to large internal angle discrepancies against measured values. Moreover, the error values and their sign differ from one machine to the other. The calculation methods applied to certain large generators (especially under leading power-factors) overestimate the angular displacement by as much as 10. In other cases of unsaturated machines, the calculated angle resulted smaller than the measured one.

For these reasons, this paper proposes an extremely simple but relative accurate model, corrected according to a



WITHOUT CORRECTION

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Actual measured angular displacement '

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WITH CORRECTION

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Actual measured angular displacement '

Calcu

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preliminary flux probe test. The model is still based on [12] but assumes initially that the generator has no leakage reactance (XL = 0) and that it is not saturated at all. The angular displacement ' is firstly calculated according to (1) and (2) based on unsaturated synchronous reactance. Then, ' is linearly adjusted by one unique saturation-correction factor k to match the actual measured angle. k is a number greater than unity, higher for machines that work more saturated (for analyzed generators k resulted in the range of 1.0 to 1.3). The angular displacement corrected value 'C will be:

'C = ' / k . (5)

The unique generator saturation-correction factor k can be

easily determined by a normal load preliminary flux probe test, once per generator type life.

Undoubtedly, a further advantage of this method is that the leakage reactance value and magnetization curve / air-gap line are no longer required for the computation.

The results from Table I indicate that in the majority of cases this calculation gives acceptable angular displacement absolute errors versus measured data, inside 4 range. Fig. 8 displays the uncorrected and corrected errors using the factor k, for different generators.

The proposed method may have significant intrinsic errors, a part of them mentioned already due to the simple used model and other due to data and calculus uncertainties (like power and voltage measurements). Considering these limitations, the total angular errors obtained in Table I seem reasonable. In addition, for most generators the error margin of 4 does not exceed half of adjacent rotor slot centerlines distance, i.e. it is completely adequate for test sensitivity.

2

Fig. 8. Uncorrected and corrected errors using the saturation-correction factor k, for different generators.

In comparison with conventional generator models, the proposed solution attains good internal angle errors. For instance [13] mentions internal angle errors as high as 10 using "standard" saturation representation.

VI. ANGULAR DISPLACEMENT PREDICTION As a second step, the author used the above mentioned

verified method to anticipate the required MW and MVAR values towards future flux probe detection in any rotor slot. Table I shows cases when the loads have been predicted before the tests and their results.

The angular displacement prediction stages are as following:

A. One Preliminary Flux Probe Test (at any normal high load, once per each generator type life; coordination with operation or dispatcher personnel is not needed for this preliminary test). Test Input: Generator actual MW, MVAR; System actual kV. Test Output: Saturation-correction factor k, rotor slots centerline angles. - Calculate the angular displacement ' according to (2) and (3). For this purpose we use a simple spreadsheet (Table I). - Establish the saturation-correction factor k according to (5) looking for minimum absolute error between 'C and measured angle. We determine k in the same spreadsheet using the Excel "Goal Seek" function. - Read on flux probe data the rotor slots centerline angle values. In many generators the slots are equally distributed between poles. In other cases, the angle step differs around the rotor. For the analyzed generators having 7 or 8 coils per pole, the measured angle step is 8 to 10.

B. Computation before Flux Probe Periodical Tests (based on load dispatcher forecast regarding unit loads and system voltage profile; any predicted P and Q shall meet the unit limits: generator capability curve, maximum and minimum excitation limits settings, 5% generator terminal voltage limits, etc.) Test Input: Rotor slots centerline angles, saturation-correction factor k; System expected kV at plant location. Test Output: Generator predicted MW, MVAR. - Predict MVAR for small coils (e.g. slots #1 to #4), testing as long as possible at optimized or full MW required by dispatcher. Normally, it is much faster and cheaper for plant and tester to play with reactive than active loads. - Predict MVAR for larger coils (e.g. slots #5 to #7), testing at minimum operational MW. Normally these tests should be performed at a different time than the previous, like during the night (low system loads). - Predict MW and MVAR for largest coil (e.g. slot #8). Usually this test can be done only at very low MW (immediately after unit synchronization).

The above mentioned spreadsheet permits also goal seeking Q (or P) for any given ' and P (or Q).

Fig. 9 shows another way to present the suitable loads: constant ' lines on generator capability curve.

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u)

4.8 (slot 7)

14.5 (slot 6)

24.1 (slot 5)

33.8 (slot 4)

43.4 (slot 3)

53.0 (slot 2)

62.7 (slot 1)

Fig.9. Example of constant angular displacement curves per each rotor slot. To make the flux probe more practical for angular

displacement prediction, it is desirable to improve its monitoring software in order to display the time axis (ms) ruled also in electrical degrees ().

VII. OTHER ASPECTS Israel Electric (IECo) is gradually equipping its turbo-

generators with permanent flux probes, during major outage opportunities when the rotor is withdrawn. Some flux probes are furnished as a part of contractor's overhaul works; in other cases, IECo installs the probes by itself (Fig. 10). A dedicated IECo team performs the periodic flux probe tests in all units using mobile PC-based hardware / software package.

If the flux probe supplier is different than the generator OEM, the flux probe ordering involves knowledge of relevant machine internal dimensions. The restrictive outage schedules require obtaining these data from the OEM before rotor withdrawal, but this can be an impossible task. One European manufacturer still refuses to provide us the pertinent data.

IECo implemented some alternative installation solutions to those recommended by the flux probe manufacturer. For instance, in just re-winded generators the dedicated flux probe penetration gland is not used; its wires are passed through spare holes in RTD / thermo-couplers gland, as in Fig. 11.

To date, IECo performed hundreds of flux probe readings. Several generators exhibit shorted turns problems.

VIII. CONCLUSIONS This paper presents some flux probe aspects of theoretical

and practical interest, including a simple method intended to predict the generator loads suitable for test.

The flux probe measurements can help understanding the synchronous machine theory and behavior.

Fig. 10. Block mount type flux probe (GeneratorTech, Inc. hardware) installed in a 133.75MVA, 11.5kV, 2 poles, 50Hz generator.

Fig.11. Passing flux probe wires through existing RTD / thermo-couplers

penetration gland (Doosan) in a 464.4MVA, 18kV, 2 poles, 50Hz generator

REFERENCES [1] D. J. Albright and D. R. Albright, GeneratorTech Inc., "Generator Field

Winding Shorted Turns: Observed Conditions and Causes". Available: http://www.generatortech.com

[2] G. Klempner, Kinectrics Inc., "Rotor Shorted Turns - Detection and Diagnostics", EPRI International Conference on Electric Generator Predictive Maintenance and Refurbishment, Orlando, 2003.

[3] D. R. Albright, D. J. Albright and J. D. Albright, GeneratorTech Inc., "Generator Field Winding Shorted Turn Detection Technology". Available: http://www.generatortech.com

[4] General Electric Company, "Generator Field Winding Shorted-Turn Detector", GET-6987, 1988.

[5] D. R. Albright, General Electric Company, "Interturn Short-Circuit Detector for Turbine-Generator Rotor Windings", GER-2668, IEEE Summer Power Meeting, Los Angeles, 1970.

[6] GeneratorTech, Inc., "Generator Field Winding Shorted Turn Detector", Information packet, 2005.

[7] GeneratorTech, Inc., "Two-Pole Rotor Winding Shorted Turn Detection System. Instruction Manual", 2004.

[8] General Electric Company, "Generator Field Winding Shorted Turn Detector (Flux Probe)", GET-6987B, 2001.

[9] J. Kapler, S. Campbell and M. Credland, Iris Power Engineering Inc., "Continuous Automated Flux Monitoring for Turbine Generator Rotor Condition Assessment", EPRI Workshop, Charlotte, 2004.

[10] K. K. Rao, G. J. Goodrich, "Online Detection of Shorted Turns in a Generator Field Winding", US Patent US 6911838 B2, 2005.

[11] IEEE C57.116-1989, "IEEE Guide for Transformers Directly Connected to Generators".

[12] IEEE Std 1110-2002, "IEEE Guide for Synchronous Generator Modeling Practices and Applications in Power System Stability Analyses".

[13] Prabha Kundur, "Power System Stability and Control", McGraw-Hill, 1994, pp. 117-118.


TABLE I ANGULAR DISPLACEMENT CALCULATION AND PREDICTION

RATED INPUT SATURATION FIELD ACTUAL INPUT OUTPUT FLUX PROBE DATACORRECTION SLOT ANGULAR DISPLACEMENT 'FACTOR

MVA kV pu MVA kV kV pu # MW MVAR kV deg () deg () deg () deg () # d/m/y h:mMD1464.4 18 2.1 450 18 169.05 0.137 1.15 8 22 38 165.2 4.9 4.3 4.6 -0.3 10 17/05/2006 19:41464.4 18 2.1 450 18 169.05 0.137 1.15 7 75 100 164.5 13.1 11.4 13.4 -2.0 31 23/05/2006 00:11464.4 18 2.1 450 18 169.05 0.137 1.15 6 130 107 164.0 21.6 18.8 21.8 -3.1 39 23/05/2006 00:36464.4 18 2.1 450 18 169.05 0.137 1.15 5 150 33 164.2 31.4 27.3 29.8 -2.5 17 22/05/2006 08:57464.4 18 2.1 450 18 169.05 0.137 1.15 4 350 120 165.0 45.5 39.6 39.9 -0.3 60 28/06/2006 23:52464.4 18 2.1 450 18 169.05 0.137 1.15 3 350 40 164.8 54.1 47.1 44.9 2.2 59 28/06/2006 23:51464.4 18 2.1 450 18 169.05 0.137 1.15 2 350 -30 164.0 63.9 55.6 53.7 1.9 58 28/06/2006 23:49464.4 18 2.1 450 18 169.05 0.137 1.15 1AT2

133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 7 10 0 163.0 8.7 8.1 6.7 1.4 5 20/03/2006 16:29133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 6 20 25 163.5 12.0 11.2 14.7 -3.4 7 20/03/2006 16:31133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 5 40 30 164.3 21.8 20.4 24.3 -4.0 10 20/03/2006 16:33133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 4 70 30 164.3 35.0 32.7 34.6 -1.9 15 20/03/2006 16:36133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 3 110 30 165.0 47.7 44.6 43.8 0.8 21 20/03/2006 16:40133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 2 110 10 164.7 54.9 51.4 52.2 -0.9 26 20/03/2006 16:52133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 1 110 -10 164.5 63.7 59.5 55.2 4.4 29 20/03/2006 16:55AT2

133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 7 6 0 163.5 5.2 4.9 5.9 -1.0 3 23/10/2006 08:56133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 6 19 0 163.2 16.2 15.1 16.4 -1.3 6 23/10/2006 09:01133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 5 32 0 162.8 26.2 24.5 26.7 -2.2 11 23/10/2006 09:14133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 4 100 60 165.5 36.7 34.3 34.7 -0.4 12 23/10/2006 09:53133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 3 100 27 164.6 46.1 43.0 43.0 0.1 16 23/10/2006 10:04133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 2 100 4 163.4 55.2 51.6 49.5 2.1 17 23/10/2006 10:07133.75 11.5 1.905 140 11.5 169.05 0.13 1.07 1 100 -10 162.8 62.0 58.0 54.0 4.0 20 23/10/2006 10:09HG6

148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 7 12 0 399.6 10.0 9.6 8.4 1.2 8 07/03/2006 14:50148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 6 20 0 399.6 16.3 15.7 13.8 1.9 10 07/03/2006 14:51148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 5 60 40 408.4 27.4 26.3 29.4 -3.0 102 10/05/2006 16:01148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 4 80 40 408.4 34.7 33.3 33.1 0.2 104 10/05/2006 16:04148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 3 90 20 408.4 44.0 42.3 43.2 -0.9 109 10/05/2006 16:08148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 2 90 5 408.4 49.7 47.7 47.8 -0.1 112 10/05/2006 16:10148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 1HG6

148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 7 7 0 403.4 5.7 5.5 6.5 -0.9 6 08/01/2007 08:35148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 6 21 0 403.4 16.8 16.2 17.2 -1.0 8 08/01/2007 08:37148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 5 37 0 403.4 28.0 27.0 29.1 -2.2 12 08/01/2007 08:40148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 4 100 52 404.4 38.1 36.6 37.8 -1.2 19 08/01/2007 08:49148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 3 100 20 404.6 47.4 45.6 45.1 0.5 23 08/01/2007 08:51148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 2 100 -6 404.0 58.0 55.8 52.6 3.1 26 08/01/2007 08:54148.5 11.5 1.959 150 11.5 421.23 0.12 1.04 1 100 -13 404.0 61.4 59.0 54.7 4.3 28 08/01/2007 08:55RH2

133.75 11.5 1.905 140 11.5 165.03 0.13 1.06 7 4 15 160.4 2.8 2.6 5.5 -2.9 8 25/09/2006 12:03133.75 11.5 1.905 140 11.5 165.03 0.13 1.06 6 19 14 160.4 13.0 12.3 14.5 -2.2 10 25/09/2006 12:05133.75 11.5 1.905 140 11.5 165.03 0.13 1.06 5 35 13 160.5 23.4 22.0 23.5 -1.5 13 25/09/2006 12:07133.75 11.5 1.905 140 11.5 165.03 0.13 1.06 4 55 13 160.5 34.2 32.3 34.0 -1.7 19 25/09/2006 12:09133.75 11.5 1.905 140 11.5 165.03 0.13 1.06 3 74 13 160.6 42.5 40.1 43.0 -2.9 23 25/09/2006 12:12133.75 11.5 1.905 140 11.5 165.03 0.13 1.06 2 95 0 160.2 55.4 52.2 52.9 -0.6 29 25/09/2006 12:18133.75 11.5 1.905 140 11.5 165.03 0.13 1ZA3295 15.75 2.07 350 15.75 425.25 0.166 1.21 8 11 25 408.2 3.9 3.3 3.8 -0.5 4 28/11/2006 14:56295 15.75 2.07 350 15.75 425.25 0.166 1.21 7 70 128 410.2 14.2 11.7 13.0 -1.3 13 28/11/2006 15:18295 15.75 2.07 350 15.75 425.25 0.166 1.21 6 70 29 408.2 23.1 19.1 21.7 -2.6 8 28/11/2006 15:05295 15.75 2.07 350 15.75 425.25 0.166 1.21 5 70 -20 407.4 33.0 27.2 29.5 -2.2 20 28/11/2006 15:29295 15.75 2.07 350 15.75 425.25 0.166 1.21 4 230 116 405.6 41.6 34.4 34.8 -0.4 43 28/11/2006 18:03295 15.75 2.07 350 15.75 425.25 0.166 1.21 3 230 60 404.7 49.7 41.0 41.2 -0.2 39 28/11/2006 17:56295 15.75 2.07 350 15.75 425.25 0.166 1.21 2 230 14 407.4 57.8 47.8 47.1 0.7 34 28/11/2006 17:45295 15.75 2.07 350 15.75 425.25 0.166 1.21 1 230 -25 403.7 66.9 55.3 51.0 4.3 36 28/11/2006 17:49RT1647 22 1.74 651 22 409.5 0.17 1.28 8 30 10 401.9 4.6 3.6 3.8 -0.2 7 26/04/2006 12:51647 22 1.74 651 22 409.5 0.17 1.28 7 120 100 403.0 14.1 11.0 10.5 0.5 14 26/04/2006 14:05647 22 1.74 651 22 409.5 0.17 1.28 6 204 70 402.8 24.8 19.3 19.3 0.0 22 26/04/2006 15:41647 22 1.74 651 22 409.5 0.17 1.28 5 240 0 402.8 33.8 26.4 26.6 -0.2 24 26/04/2006 15:52647 22 1.74 651 22 409.5 0.17 1.28 4 390 28 404.7 44.8 35.0 34.8 0.2 30 23/05/2006 00:05647 22 1.74 651 22 409.5 0.17 1.28 3 450 -70 405.6 58.5 45.7 42.2 3.6 38 23/05/2006 00:39647 22 1.74 651 22 409.5 0.17 1.28 2 500 -70 403.7 61.6 48.1 46.2 1.9 42 23/05/2006 00:52647 22 1.74 651 22 409.5 0.17 1.28 1RT2647 22 1.74 651 22 409.5 0.17 1.28 8647 22 1.74 651 22 409.5 0.17 1.28 7647 22 1.74 651 22 409.5 0.17 1.28 6 219 109 411.8 23.5 18.3 18.6 -0.3 20 21/01/2007 01:45647 22 1.74 651 22 409.5 0.17 1.28 5 240 3 411.6 32.4 25.3 26.6 -1.3 15 21/01/2007 01:29647 22 1.74 651 22 409.5 0.17 1.28 4 390 36 410.8 43.3 33.9 34.2 -0.4 9 21/01/2007 00:24647 22 1.74 651 22 409.5 0.17 1.28 3 575 100 407.4 50.2 39.2 37.6 1.6 1 02/01/2007 12:29647 22 1.74 651 22 409.5 0.17 1.28 2647 22 1.74 651 22 409.5 0.17 1.28 1

GENERATOR MAIN TRANSFORMERRated output

Rated voltage

Unsaturated reactance

Rated power

Rated low

Rated high Reactance Test time

Active power

Reactive power

System voltage

Load pointCalculated Corrected Measured Error

The highlighted values are for predicted MW and MVAR loads.


IntroductionSynchronous Machine BasicsFlux Probe PrinciplesFlux Probe Practical ConsiderationsAngular Displacement CalculationAngular Displacement PredictionOne Preliminary Flux Probe Test (at any normal high load, on- Calculate the angular displacement ' according to (2) and- Establish the saturation-correction factor k according to - Read on flux probe data the rotor slots centerline angle v

Computation before Flux Probe Periodical Tests (based on loa- Predict MVAR for small coils (e.g. slots #1 to #4), testin- Predict MVAR for larger coils (e.g. slots #5 to #7), testi- Predict MW and MVAR for largest coil (e.g. slot #8). Usual

Other AspectsConclusions

Documents

Flux Probe