Several alternative methods available: Enhanced sudden short circuit tests: Improvement over IEEE Standard 115-1983; uses rotor current measurements to identify field circuit data Does not provide accurate q-axis data Stator decrement tests: Unit tripped with only d-axis armature current (P=0, iq=0); terminal voltage and field current time responses used to estimate d-axis data Similar test with only q-axis armature current (id=0) gives q-axis data; load angle equal to power factor angle, a condition difficult to determine when parameters not known accurately Difficulty in maintaining constant field voltage with bus-fed exciters Currently, fairly widely used. References 1, 2 and 3 describe this approach

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GENERATING UNIT TESTING AND
MODEL VALIDATION
Copyright © P. Kundur
This material should not be used without the author's consent

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The Process
 Review plant documents and existing models
 Prepare test plan
 Perform pre-field-test simulation
 Field tests for:
 Parameter estimation
 Verification of models
 Parameter estimation
 Model validation
 Overall assessment

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Identification of Generator
Parameters/Characteristics
 Open Circuit Saturation
 Reactive Power Capability
 D-axis Parameters
 Q-axis Parameters

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Determination of Generator D- and
Q-axis Parameters
Several alternative methods available:
a) Enhanced sudden short circuit tests:
 Improvement over IEEE Standard 115-1983; uses
rotor current measurements to identify field circuit
data
 Does not provide accurate q-axis data
b) Stator decrement tests:
 Unit tripped with only d-axis armature current (P=0,
iq=0); terminal voltage and field current time
responses used to estimate d-axis data
 Similar test with only q-axis armature current (id=0)
gives q-axis data; load angle equal to power factor
angle, a condition difficult to determine when
parameters not known accurately
 Difficulty in maintaining constant field voltage with
bus-fed exciters
 Currently, fairly widely used.
References 1, 2 and 3 describe this approach

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Determination of General parameters (cont'd)
c) Standstill frequency response (SSFR) tests:
 Rotor stationary, disconnected from the system, and
aligned to two particular positions
 Stator excited by a low level (±60A, ±80V) source over
frequency range 1 mHz to 1 kHz
 Operational parameters measured:
Ld(s): d-axis operational inductance
Lq(s): q-axis operational inductance
G(s): stator to field transfer function
 Parameters of d- and q-axis equivalent circuits
obtained using transfer function approximations
 Where damper windings are used, they are often just
overlapped; may not form good connection at
standstill (rotational effects significant)
 At low and high frequencies, data good,
At mid-frequency range data may not be accurate for
machines with specific type of dampers
References 4, 5 and 8 present this approach

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Determination of General Parameters (cont'd)
d) Open-circuit frequency response tests:
 Unit operated on open-circuit at reduced voltage
 Field excited at various frequencies and field-to-
stator frequency response measured
 Allows confirmation of data in mid-frequency
range; gives indication of rotational effects
The measured operational parameters for a 500 MW, 3800
RPM generator at Lambton GS in Ontario is shown in
Figures 4.7, 4.8, 4.9. The second- and third-order transfer
function approximations to measured characteristics are
also shown.

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Relationship Between Operational and
Standard Parameters
Figure 4.5: Variation of magnitude of Ld(s)
Copyright © P. Kundur, 1994
    
  
   
  
 
  
  0q0q
qq
qq
0d0d
kd
0
0d0d
dd
dd
Ts1Ts1
Ts1Ts1
LsL
Ts1Ts1
sT1
GsG
Ts1Ts1
Ts1Ts1
LsL










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e) On-line Frequency Response (OLFR) tests:
 Machine operated near rated (or at any desired)
output
 Excitation modulated by either sinusoidal signal or
random noise
 Components are resolved on the two axes and
operational parameters similar to those of SSFR
tests are used to derive a model
 Rotational effects are captured; could be
significant depending on rotor construction
References 6, 7 and 8 present this approach
Model Validation
In Reference 10,
 Models for three large generators based on SSFR
and OLFR tests are validated by comparing results
of simulations with measured dynamic responses
involving line switching
 For one generator, models derived from stator
decrement tests and short-circuit tests are also
validated

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Excitation System Testing and Model
Validation
1. Obtain circuit diagrams, block diagrams, nominal
settings and setting ranges
 Construct a detailed block diagram
2. With generator shut down, perform frequency response
and/or transient response tests on individual elements
 Identify transfer functions, nonlinearities, and ceiling
limits
 Validate as much of detailed block diagram as
possible; modify diagram as necessary
3. (a) With generator running open-circuit at rated speed
and rated voltage, perform frequency response
and time-response tests
 Measure overall linear response and responses at
various points to a step change in AVR reference
(b) Perform additional tests with generator at rated
output
(c) Validate detailed model of complete system
4. Reduce detailed model to fit standard model for the
specific type excitation system
 Validate by comparison against measured response
Nature of tests required depends on type of excitation
system. A general procedure is as follows:
Techniques for field testing, model development and validation
are described in References 11, 12 and 13.

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References
Generator Testing
(a) Stator Decrement Tests:
[1] G. Shackshaft and A. T. Poray, "Implementation of New Approach to
Determination of Synchronous Machine Parameters from Tests", Proc.
IEE (London), Vol. 124, No. 12, pp. 1170-1178, 1977.
[2] F. P. deMello and J.R. Ribeiro, "Derivation of Synchronous Machine
Parameters from Tests", IEEE Trans., Vol. PAS-96, pp. 1211-1218,
July/August 1977.
[3] F.P. deMello and L.N. Hannett, "Validation of Synchronous Machine
Models and Determination of Model Parameters from Tests", IEEE
Trans., Vol. PAS-100, pp. 662-672, February 1981.
(b) Frequency Response Tests:
[4] M.E. Coultes and W. Watson, "Synchronous Machine Models by
Standstill Frequency Response Tests", IEEE Trans., Vol. PAS-100, pp.
1480-1489, April 1981.
[5] P.L. Dandeno and A.T. Poray, "Development of Detailed
Turbogenerator Equivalent Circuits from Standstill Frequency
Response Measurements", IEEE Trans., Vol. PAS-100, pp. 1646-1653,
April 1981.
[6] M.E. Coultes, P. Kundur and G.J. Rogers, "On-Line Frequency
Response Tests and Identification of Generator Models," IEEE Trans.,
Vol. EC-2, pp. 38-42, September 1987.
[7] P.L. Dandeno, P. Kundur, A.T. Poray, and H.M. Zein El-Din, "Adaptation
and Validation of Turbogenerator Model Parameters through On-Line
Frequency Response Measurements", IEEE Trans., Vol. EC-2, pp.
16546-1661, September 1987.
[8] IEEE Std. 1110-2002, "IEEE Guide for Synchronous Generator
Modelling Practices and Applications in Power System Stability
Analyses".
[9] IEEE Std. 115-1995, "IEEE Guide: Test Procedures for Synchronous
Machines".

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References (cont'd)
(c) Model Validation:
[10] P.L. Dandeno, P. Kundur, A.T. Poray, and M.E. Coultes, "Validation of
Turbogenerator Stability Models by Comparison with Power system
Tests", IEEE Trans., Vol. EC-2, pp. 1637-1645, September 1987.
Excitation System Testing
[11] IEEE Committee Report, "Excitation System Dynamic Characteristics",
IEEE Trans., Vol. PAS-92, pp. 64-75, January/February 1973.
[12] IEEE Guide for identification, Testing and Evaluation of the Dynamic
Performance of Excitation Control Systems, IEEE Standard 421.1-
1990 (revision to IEEE Standard 421A-1978).
[13] IEEE Tutorial Course Text, "Power system Stabilization via Excitation
Control - Chapter IV: Field Testing Techniques", Publication 81 EHO
175-0 PWR.