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ISBN: 978-1-4799-8903-4 2015 IEEE 11th International Conference on the Properties and Applications of Dielectric Materials (ICPADM)

FEM Simulation and Analysis on Stator Winding
Inter-turn Fault in DFIG
Yu Chen*, Lulu Wang,
Zihao Wang, Attiq Ur Rehman,
Yonghong Cheng
State Key Laboratory of Electrical
Insulation and Power Equipment,
Xi’an Jiaotong University
Xi’an, Shaanxi, China
*E-mail: chenyu@mail.xjtu.edu.cn

Toshikatsu Tanaka

Yong Zhao

IPS Research Center
Waseda University
Fukuoka, Japan

Xi’an TPRI Co., Ltd
Xi’an, Shaanxi, China

Abstract—With the development of renewable energy
technology, Doubly-Fed Induction Generators (DFIG) are widely
used on wind farms. Faults of machines have a direct influence
on the safety and effectiveness of the power grid. In order to
explore failure mechanism, it is of great importance to study the
DFIG fault simulation models and features. In this paper, a
Finite Element Method (FEM) simulation model of stator
winding inter-turn fault in DFIG is presented by the software of
ANSYS Maxwell. Different stator inter-turn short circuit fault
conditions are achieved by changing the stator winding
connection and the values of end leakage-inductance and
resistance. Under normal condition, different branches’ currents
are the same in each phase and different phase currents are
balanced. So the Total Harmonic Distortions (THD) of threephase stator currents are low and phase differences of stator
currents are all about 120°. Additionally, Park’s vector trajectory
is a circle and its eccentricity is approximately zero. However, as
the fault degree enlarges, both the current of faulty-branch and
the eccentricity of Park’s vector trajectory increase. The phase
differences related to faulty-phase and THD of faulty-phase
become larger. Therefore, THD, phase differences and the
eccentricity can be regarded as three fault features to diagnose
fault phase and fault degree.

changing the number of shorted turns and the value of shortcircuit resistance. However, this simulation method cannot
reflect the real condition of fault. Because when an inter-turn
short circuit fault occurs, a new loop emerges between the
faulty turns and the loop current will be much larger than phase
currents. And then temperature rises in the faulty winding,
affecting the insulation materials near the fault location. It may
lead to more turns shorted and even phase to phase or phase to
ground short circuit fault. So the new loop cannot be ignored.

Keywords—DFIG; stator winding inter-turn fault; FEM
simulation; fault features

FEM is a numerical calculation method based on
variational principle. It transforms a variational problem into an
extremum problem of multivariate function by the subdivision,
interpolation and discretization of field.

In this paper, a DFIG model with stator inter-turn short
circuit fault is built in Maxwell 2D. Based on the finite element
method, different shorted turns are simulated by changing the
phase winding connection and the values of end leakageinductance and resistance. The detail procedure is discussed for
inter-turn short circuit fault in the same branch and we analyze
the simulation results to validate this model. The faulty-branch
current, phase differences related to faulty-phase, THD of
faulty-phase and the eccentricity of Park’s vector trajectory of
stator currents are extracted as features under the premise to
ensure that no other damages to the machine.
II.

I.
INTRODUCTION
DFIG is widely used in the wind energy industry. It is an
important system component and is often exposed to complex
environment conditions. According to the survey, 40% of
DFIG failures are related to bearings, while 38% to the stator
and 10% to the rotor [1]. Faults would cause such features as: 1)
unbalanced air-gap voltages and line currents; 2) increased
torque pulsation; 3) excessive heating; 4) disturbances in the
current, voltage or flux waveform [2]. In order to find features
to indicate different kinds of faults in DFIG, researchers have
done a lot of work in modeling, simulating and experimenting.
In general, there are two main approaches to model DFIG
faults. From the view of “circuit” analysis, simulation model
can be built in MATLAB/Simulink according to the Multi-loop
Theory [3] and machine mathematical equations [4]. Another
method is from the view of “electromagnetic field” analysis
called FEM. It uses the electro-magnetic software
ANSYS/Maxwell 2D to build the DFIG simulation model.
Models presented in [5-8] for a stator winding inter-turn short
circuit fault are based on Maxwell 2D and achieved by

FEM ANALYSIS OF ELECTRICAL MACHINES

A whole machine is considered as the calculation field for
the aim of analyzing the stator winding inter-turn fault. With
the vector magnetic potential being the solving variable, a twodimensional electromagnetic field model for electrical
machines can be established by the vector magnetic potential
Az. Therefore the expression of electrical machines in
electromagnetic field is shown in equation (1).

⎧∂

⎪ ⎛⎜ μ ∂AZ ⎞⎟ + ∂ ⎜ μ ∂AZ
⎪ ∂x ⎝ ∂x ⎠ ∂y ⎝ ∂y

⎨ AZ Γ1 = AZ 0

⎪ 1 ∂AZ
⎪ μ ∂n = − H t
Γ2



∂AZ
∂A
+ vxσ Z
⎟ = −JZ + σ
t

∂x

(1 )

In (1), vx is the x component of the rotation speed; JZ is the
z component of the source current; μ is the permeability; σ is

978-1-4799-8903-4/15/$31.00 ©2015 IEEE

244

ISBN: 978-1-4799-8903-4 2015 IEEE 11th International Conference on the Properties and Applications of Dielectric Materials (ICPADM)

TABLE I.

the conductivity; AZ0 is the given value of AZ on the boundary
of Γ1 ; Γ2 is the Neumann Boundary Condition.
III.

Number of poles
Number of slots
Circuit type
Outer Diameter

520/350 mm

Inner Diameter
The number of
turns per phase
Rated output
power
Rated speed

346.4/110 mm

Parameter

MODELING OF DFIG IN ANSYS/MAXWELL

A. Machine Parameters
A 110 kW three-phase doubly-fed induction generator is
used for simulation. The parameters of this machine are given
in TABLE I.
B. Modeling Method
In general, there are three ways to draw Doubly-Fed
Induction Machine geometry model. The simplest and the
most accurate method is to model in ANSYS/RMxprt, then
import it to Maxwell 2D. In order to facilitate the fault set, a
complete model should be imported from RMxprt to Maxwell
2D automatically, seen in Fig.1.

MACHINE OPERATION PARAMETERS
Value
(Stator/Rotor)
4/4
72/60
△/Y

228/100

Parameter
Length
Winding layers
Parallel branches
Conductors per
slot
Coil pitch
Rated power
factor

Value
(Stator/Rotor)
290 mm
2/2
4/1
19/10
15/13
1

110 kW

Rated voltage

380 V

1800 rpm

Frequency

50 Hzh

A zero Vector Potential is added to the outer stator surface.
Three-phase AC current source is given to rotor windings,
while the stator winding excitations are set in external circuit
which has taken stator end leakage-inductances into
consideration.
C. Stator Winding Inter-turn Short Circuit Model
Due to four branches paralleled in per phase of stator
winding, the stator winding inter-turn short circuit fault
consists of two types: 1) inter-turn short circuit in the same
branch; 2) inter-turn short circuit in two different branches.
For the inter-turn short circuit fault in the same branch
(taking phase A for example, phase A consists of four
branches). If the fault is located in the third slot, then this
branch can be divided into one shorted winding (A1_sc) and
two non-shorted windings (A1_1 and A1_3), which can be
seen in Fig.2. The geometry model for stator inter-turn fault in
phase A is seen in Fig.3. The method of field-circuit coupling
is chosen to model the inter-turn short circuit, so the external
circuit should be introduced which is shown in Fig.4.
Additionally, in order to consider the machine end-effect, the
terminal resistance R and end leakage-inductance L for
different shorted turns are calculated and used.

Fig. 2.

The schematic diagram of phase A on stator winding

Fig. 3.

Geometry model for stator inter-turn fault in phase A

IV.

Similar method can be used for modeling inter-turn fault in
different branches. For the inter-turn short circuit in two
different branches, both of them should be divided and the
settings should be made in external circuit.

SIMULATION AND RESULTS ANALYSIS

A. Simulation of Machine under Different Conditions
Machine under healthy condition is simulated in ANSYS
Maxwell at the speed of 1800 rpm. Three phase currents on
stator winding are shown in Fig.5.
For a 7-turn short circuit fault in branch A1, the faultybranch current IA1_1 and the new loop current IA1_sc are starting
to increase from the short-circuit moment. Before t = 0.8 s,
IA1_1 and IA1_sc are equal because their windings are in a series.
At t = 0.8 s, the winding A1_sc is shorted and a large current
is induced in the new loop. The equivalent impedance of
branch A1 decreases and therefore IA1_1 increases. The
waveform of four branches (A1_1 、 A2 、 A3 、 A4) and the
new loop current (A1_sc) under 7-turn short circuit fault is
shown in Fig.6.

Fig. 1.

In order to study the relationship between fault features
and fault degrees, more simulations for different shorted turns
are required. So ten different conditions are simulated and the
simulation results are analyzed below.

Geometry model for normal condition

245

ISBN: 978-1-4799-8903-4 2015 IEEE 11th International Conference on the Properties and Applications of Dielectric Materials (ICPADM)

Fig. 4.

The external circuit for inter-turn short circuit fault

B. Analysis of Simulations Results
1) Analysis of branch currents
In the same slot of branch A1, ten simulations have been
carried out under healthy condition (0-turn short circuit) and
1~9 turns short-circuit fault. Simulation results of branch
current IA1_1 under healthy and fault conditions (3-turn, 6-turn,
9-turn short-circuit fault) are presented in Fig.7. These results
corroborate that the magnitude of faulty-branch becomes
bigger with the increase of fault degree.

Fig. 5.

2) Analysis of three phase currents
In a DFIG online monitoring system, three phase currents
on stator winding are generally collected. And therefore the
analysis of three-phase current is necessary. The phase
differences and THD [9] of stator currents under different
stator inter-turn fault conditions are presented in TABLE II.
For phase A inter-turn short circuit fault, φAB and φCA deviate
120° more and more from 1 to 9 turns shorted, while φBC has
almost no change (about 120°). THD of phase A is bigger
and bigger with the increase of the number of shorted turns,
while THD of phase B and C have little change. In other
words, the phase differences related to faulty-phase deviate
from 120 ° and more deviation means more serious fault.
THD of faulty-phase is bigger than the others. The bigger of
the THD, the more serious the fault is. So it has been
suggested that the fault phase is related to both the phase
difference and THD, which are regarded as two features for
fault degree and fault phase.

Stator three phase currents under healthy condition

Fig. 6.
Branch currents of phase A under 7-turn short circuit fault
condition

According to the principle of magnetic potential balance,
three phase currents can be transformed from three-phase axis
coordinate to two-phase axis. Therefore, the vector I = iα + jiβ
is named as Park’s Vector. Ideally, the Park’s vector trajectory
is a circle centered on the origin. For stator winding inter-turn
fault, it turns out to be an ellipse. The Park’s vector
trajectories of different conditions are shown in Fig.8.
Additionally, the length of semi-major axis, the length of
semi-minor axis and the eccentricity of ellipse for different
conditions are shown in TABLE II. As fault degree enlarges,
the length of semi-major axis lengthens and the length of
semi-minor axis shows in an opposite trend. However, they
are not appropriate to be features of fault. Given eccentricity is
the comprehensive index of them and it increases with the
fault degree, we appreciate it a proper index for fault feature.

Fig. 7.
Current of branch A1 under different stator winding fault
conditions

246

ISBN: 978-1-4799-8903-4 2015 IEEE 11th International Conference on the Properties and Applications of Dielectric Materials (ICPADM)

TABLE II.
The number of
shorted turns

FAULT FEATURES FOR STATOR WINDING FAULT UNDER DIFFERENT CONDITIONS

Phase difference

THD

Parks’ vector trajectory

AB

BC

CA

A

B

C

Length of semimajor axis

Length of semiminor axis

Eccentricity

0

120.011

120.063

119.926

3.39%

3.54%

3.22%

141.835

141.825

0.012

1

122.747

120.071

117.182

3.62%

3.57%

3.22%

143.404

138.809

0.251

2

125.536

120.061

114.404

3.92%

3.54%

3.17%

144.924

135.855

0.348

3

128.357

120.039

111.604

4.39%

3.57%

3.19%

146.517

133.128

0.418

4

131.233

120.017

108.749

4.95%

3.57%

3.21%

148.073

130.495

0.473

5

134.147

119.993

105.860

5.59%

3.55%

3.24%

149.633

127.978

0.518

6

137.102

119.962

102.937

6.29%

3.52%

3.28%

151.194

125.566

0.557

7

140.097

119.925

99.978

7.02%

3.49%

3.33%

152.759

123.253

0.591

8

143.108

119.854

97.038

7.94%

3.48%

3.39%

154.253

121.072

0.620

9

146.127

119.769

94.104

8.75%

3.48%

3.45%

155.810

118.931

0.646

0.646). Therefore, they can be used as fault features to provide
references for fault diagnosis.

(a) Healthy condition

However, this paper only discusses and simulates the interturn short circuit in the same slot of one branch. Although
different numbers of shorted turns are simulated, it cannot
include all the conditions of inter-turn fault. In addition, other
kinds of fault may also induce thus features, so inter-turn short
circuit in different slots and rotor winding inter-turn fault
should be simulated and analyzed in the near feature.

(b) 3-turn short-circuit

ACKNOWLEDGMENT
This work is supported by the Headquarters Science and
Technology Projects of China Huaneng Group, under project
number “HNKJ13-H20-05”.
REFERENCES
(c) 6-turn short-circuit

[1]

(d) 9-turn short-circuit

Fig. 8.
Park’s vector trajectory under different stator winding fault
conditions

[2]

V. CONCLUSIONS
This paper discusses how to build a FEM model for DFIG
with stator winding inter-turn short circuit fault in detail. The
simulation model is implemented in ANSYS Maxwell. Ten
simulations of different conditions have been carried out by
changing the phase winding connection and the value of end
leakage-inductance and resistance in external circuit. Branch
currents of faulty-phase and three phase currents on stator
winding are analyzed. Some features are calculated, i.e.,
branch currents, phase currents, phase differences, THD of
three stator phase currents and the eccentricity of Park’s vector
trajectory of stator currents.

[3]

[4]

[5]

[6]

[7]

The simulation results show that the increase of fault
degree from healthy condition to 9 turns shorted causes the
increasingly growth of the faulty-branch current, the phase
differences related to faulty-phase (φAB: from 120.011 to
146.127, φCA: from 119.926 to 94.104), the THD of faultyphase (THDA: from 3.39% to 8.75%), and the eccentricity of
Park’s vector trajectory of stator currents (from 0.012 to

[8]

[9]

247

N. Goudarzi, D. Zhu W, “A review on the development of wind turbine
generators across the world”, International Journal of Dynamics and
Control, vol. 1, pp. 192-202, 2013.
L.M. Popa, B. Jensen, E. Ritchie, “Condition monitoring of wind
generators”, Industry Applications Conference, Ias Annual Meeting,
Conference Record of the. IEEE, vol.3, pp.1839-1846, 2003.
J.Q. Li, Y.Z Ren, D. Wang, “Multi-loop Mathematical Model and
Calculation of Inductances in Doubly Fed Induction Generation”, Large
Electric Machine and Hydraulic Turbine, vol. 6, pp. 5-10, 2013.
L.L. Wang, Y. Zhao, W. Jia, B. Han, Y. Chen, “Fault diagnosis based on
current signature analysis for stator winding of Doubly Fed Induction
Generator in wind turbine”, Electrical Insulating Materials (ISEIM),
Proceedings of 2014 International Conference on, pp. 233 – 236. 2014.
S.Y. Wei, Y. Fu, H.Z. Ma. “Stator winding inter-turn short-circuit
diagnosis and experimental research on doubly-fed induction generator”,
Power System Protection and Control, vol. 38, pp. 25-28, 2010.
J.Q. Li, M. Li, D.Y. Wang. “Influence of stator turn-to-turn short-circuit
on magnetic field of DFIG”, Electrical Machines and Systems (ICEMS),
2011 International Conference on, pp.1 – 5, IEEE, 2011.
S. Seman, Transient performance analysis of wind-power induction
generators. Helsinki University of Technology, 2006.
M. Hacene, K.E. Hemsas, “Design and simulation analysis of outer
stator inner rotor DFIG by 2D and 3D finite element methods”,
International Journal of Electrical Engineering & Technology, vol. 2,
2012.
L. Fan, S. Yuvarajan, R. Kavasseri, “Harmonic analysis of a dfig for a
wind energy conversion system”, IEEE Transactions on Energy
Conversion, vol. 25(1), pp. 181 – 190, 2010.


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