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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 1 (12)
ISSN 1843-6188
THE USE OF ELECTROMAGNETIC FIELD IN MODELING
AND MONITORING ELECTRICAL EQUIPMENT
Monica ROTARIU, Adrian BARABOI, Maricel ADAM, Catalin PANCU
Faculty of Electric Engineering, Department of Energetic „Gh. Asachi”
Technical University of Iaşi, Bd. D. Mangeron, nr. 51-53, 700050
E-mail: [email protected]
process of other electricity applications thereby, nor to
exersize biological effects over living organisms
including the human factor. This is the reason we
consider as a very important aspect to take into account
the electomagnetic pollution effects generated by
electrical installations.
Abstract: Electricity is more than energy: it is a vital
component of our lives, playing an important role in the
economy of many countries. Wherever electricity is
generated, electromagnetic fields are created.
The strong development of information technology had
provided new possibilities in monitoring and diagnose of
electrical equipment and devices. The purpose of this paper is
to highlight the posibility of using the electromagnetic map of
electrical equipment in the process of monitoring, diagnosing,
controling and commanding them.
The mathematical
modelling and simulation of different operating status of the
electrical equipment and devices, was accomplished by using
the EMTP – ATP software. The paper also presents
experimental results of the monitoring and diagnose of the
electrical equipment using the information contained in their
electric and magnetic field. The data is processed with the
6024 E National Instruments acquisition board.
2. ELECTRICAL EQUIPMENT AND DEVICES.
MONITORING AND DIAGNOSE TECHNIQUES
The electromagnetic field is generated by each
electrical equipment and installation, which can lead to
different kind of perturbations in the equipment
functioning or can cause the malfunctioning of the
equipment and devices nearby (over voltage, over
currents, excessive heating of high voltage power line
conductors).
Taking into account the facts mentioned above, in
this paper we have focused on developing modern
monitoring and diagnose techniques that with the use of
the information contained in the electromagnetic
radiation field of each electrical equipment and devices
can give us information about the different states the
equipment or devices are facing while on service.
In the chapters below are described some of the
equipment that make part of our study, highlighting the
parameters that are being analyzed using their own
electromagnetic radiation field.
Keywords: electromagnetic map, electrical equipment and
devices, electromagnetic field, acquisition board.
1. INTRODUCTION
The technological progress concerning data
transmission and the development and expansion of the
power systems worldwide was an important factor in
increasing the electromagnetic field level as well as the
bio-organism and human body exposure to the
electromagnetic radiation.
2.1 Electric motors. Star – delta starting
All indirect starting methods are used to reduce the
starting current. In the case of a star – delta starting the
network voltage is applied directly to the star connected
to a three phase winding coil.[4] When the motor reaches
a rotation speed of 90 % of its nominal speed, the phase
winding coils commute from star to delta with the help
of a switch. The commutation can be made manually or
automatic.
Effective line current for a steady state on a star
connection is described by the next expression:
Because electricity is so much a part of our lives, there
are electromagnetic fields around us most of the time. All
electric flows have an associated electric field and magnetic
field. The intensity of both electric and magnetic fields
decreases with distance from the field source. Electric
fields are more easily shielded or blocked than magnetic
fields.
The main purpose of this paper is to highlight the
posibility of using the electromagnetic map of electrical
equipment in the process of monitoring, diagnosing,
controling and commanding them.
By the achievment of advanced software/hardware
structure intelligent devices can be realized, which
represent important components in the structure of the
electric power systems including both transportation and
distribution systems.
On the other side, these devices, equipment or system
must not influence in a negative way the operating
I lY  I fY  U fY / Z f  U l / 3Z f
(1)
The effective current expression for a delta
connection changes to:
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 1 (12)
ISSN 1843-6188
I l  3I f 
3U f
Zf

3U l
Zf

time – current characteristic t =f(I). t represent
the melting time of the fuse element + the
arcing time = the breaking time.
The shape of the characteristic differs depending on fuse
type. The main difference is due to the breaking time:
there are slow fuses, fast fuses, mix fuses and ultra- fast
fuses.
(2)
The absorbed current report for the two connections
has the next value:
I lY / I l  1 / 3
(3)
Due to a 3 time mitigation of the phase voltage while
in star connection, the starting torque is also 3 times lower
than the direct starting case; the electromagnetic torque is
proportional with the square stator phase voltage. This
inconvenient is limiting the application of the star – delta
starting only in the situation of an unloaded start of a motor
or a low resistant static torque.
The star – delta starting method is used for nonsynchronic short – circuit three phase motors, with a
nominal power between 5.5 – 14 kW/ 400 V. [2] This
method can be use only in the case of the motors that
have the nominal phase voltage equal to the three phase
network line voltage. The mechanical characteristic of
the star – delta starting is shown in the figure below:
Figure. 2. Time carachteristic
For a current 15 times bigger that In the breaking
time of the fuse is very short, the circuit being
disconnected before the short circuit current reaches its
maximum value.
III. MODELLING AND SIMULATION
ELECTRICAL EQUIPMENT
OF
Modelling and numeric simulation allows us to study
and evaluate the electromecanic systems behaviour in
the applications they were designed and realized for, but
also for other application, fact that leads to the
development of new types of systems and equipment.
The electromagnet (figure 3) is one of the most
important electromecanic systems. This quite simple
device plays a significant role in the interconnections of
two subsystems, where the first systems, with electric
output signal, controls the second one which has
mecanical input signal.
Figure. 1. Electric characteristic of star-delta motor
starting
1
The star- delta starting method is very efficient from
the technical and economical point of view, that’s why it
has a large application scale in power engineering.
2
2.2. Fuses
The fuses are designed to protect the circuit against
overload and short circuit. Depending on the current they
are able to break (<1 kA to >1 kA) there are different
types of fuses. The technical characteristic of a fuse are
listed below:
 nominal current (In);
 nominal voltage (Un);
 breaking capacity – the maximum short circuit
current that can be break according to standard
normative;
U
U
4

3
x
S
Fa
Ma
i

i
Mr
m
x
J
Fr
MS
MS
a
b
Figure.3. Air – gap zone: a-transition mobile armature; linear air- gap; x- motion; m-reduce weight; Fr-resistant
force; MS-mechanic subsystem; b- titling mobile armature;
-angular air - gap; J- inertia moment
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 1 (12)
In figure 3.a. the direct current electromagnet is
designed with a transition mobile armature, while in
figure 3.b. it has a mobile titling armature.
Dependind on the amature type (transition or titling) its
motion during the transient state is described by one of
the following equations [3]:
ISSN 1843-6188
circuit functioning. This is why for an electromagnet
with translation armature (fig. 3.a), the model is based on
the equations (41), (5) and (6), while for the
electromagnet with the titling armature (Fig.3.b), the
equation (41) is replaced with the equation (42). The
electromagnetic field is characterised, in a certain point
in space, by the superposition of an electric and magnetic
field, variable in time, which are mutual generating. The
state of the electric field is described by two vectors – E
– the intensity of the electric field and D – the electric
induction. The magnetic field state is described by B –
magnetic induction and H – magnetic field intensity [1].
The numerical simulation is performed with the EMTP ATP software and the graphical results are shown with
the help of the MC’s Plot XY, in figures 5 and 6.

d 2 x dx
 at  et x  Fa ( x )  Fr ( x ),

2
dt
dt

 (4)
2
d x
dx
dx 
J 2  ab  eb x  M a ( x )  M r ( x ),x( 0 )  x0 ,  0
dt
dt 0 
dt
m
where at, ab şi et, eb are the damping and elastic constants
of the electromagnet. The active force Fa and the active
moment Ma, are described in relation (5):
0.20
0.15
2
Fa  2 F   , M a  rF ,
 0 S
0.10
(5)
0.05
0.00
F - active force reported to the air gap, r – force arm, 
- magnetic flow of the air gap, S- polar surface.
The electric circuit single line diagram of the direct
current electromagnet is shown in the figure 4.
i
-0.05
-0.10
-0.15
-0.20
0.00
L
R
0.02
0.04
0.06
0.08
[s]
0.10
0.08
[s]
0.10
(f ile CA.pl4; x-v ar t) t: PSI
Figure 5. Magnetic flow
3
U
L
2
1
a
is
0
Ls
Rs
-1
-2
ucs
us
Cs
-3
0.00
0.02
(f ile CA.pl4; x-v ar t) c:CRT -CR
factors:
1
1
offsets:
0
0
0.04
0.06
t: X
100
0
Figure 6. Current absortion of the coil and armature
motion
b
Figure .4. Single line diagram: a-electromagnet: Rresistance; L-dispersion inductance, L-inductance of the
magnetic flow; b-simulation mode
Graphical results for an alternative
electromagnet are shown in figures7 and 8.
2.0
This circuit is described by the equation (6):
1.6
di
d 
N
, 

dt
dt
(6)

d 
  Ni   F , F   K
,
dt 

where F the solenation that coresponds to Foucault
currents, N-number of coil coilings and K- constant
coeficient.
U  Ri  L
1.2
0.8
0.4
0.0
0.00
0.04
0.08
0.12
(f ile CC.pl4; x-v ar t) t: PSI
Figure 7. Magnetic flow
3.1. Numerical simulation in EMTP - ATP
The mathematic model of the direct current
electromagnet functioning is based on a differential
equations system, from which one corespond to the
mobile armature motion and the others to the electric
40
0.16
[s]
0.20
current
Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 1 (12)
ISSN 1843-6188
0.10
0.08
0.06
0.04
0.02
0.00
0.00
0.04
(f ile CC.pl4; x-v ar t) c:CRT -CR
factors:
1
1
offsets:
0
0
0.08
0.12
0.16
[s]
0.20
t: X
10
0
Figure 8. Current absortion of the coil and armature
motion
Figure 11. Magnetic induction – fuse of 60 A
4. NUMERICAL RESULTS
4.1. Electromagnetic radiation field for different fuses
For this study we have used two fuses of 40 and 60 A.
Graphical results are shown in figures 9 – 12.
The data was captured with the help of an aquisition
board and process in a LabView application. [5]
In order to distinguish the way the electromagnetic field
is influencing the good functiong of the electrical
equipment and to see the impact that it has on the staff and
the environment, the monitoring and diagnose techniques
were applied for fuses and electric motors.
Figure 12. Magnetic induction captured at the starting of
the instalation SF 60 A
Figure 9. Magnetic induction – fuse of 40 A
For the 40 A fuse we observe that the functioning time of
the instalation is 0.588 ms and in case of the 60 A fuse, the
time the instalation is in use is reduce to 0.382 ms, as we can
see from the table below:
Table 1. Signal amplitude – Service time
SF 40 A
SF 60 A
Time[s]
Amplitude [V]
0,588
0,382
14,6
16,2
4.2. Electromagnetic radiation field at the motor star
– delta starting
The front panel of the instalation is shown in figure 13.
Figure 10. Magnetic induction captured at the starting of
the instalation SF 40 A
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 1 (12)
ISSN 1843-6188
Table 2. Signal amplitude – Service time
Star – delta starting
Contactor starting
Contactor stop
Time[s]
Amplitude [V]
4,989
0,261
0,283
15
15,8
7
All the data presented above was captured using
diferent electric and magnetic sensors (magnetic coil,
electric and magnetic sensor from MetraHit 28 s device)
connected to an aquisition board, National Instruments
6024 E.
Figure 13. Front panel – star – delta starting
The grafical results are presented in the figures 14, 15
and 16.
5. CONCLUSIONS
In this paper we have tried to study new possibilities
in the monitoring and diagnose of the electrical
equipment and instalations making use of the
information contained in their own electromagnetic
radiation field. In order to obtain a very good accuracy
of the registered data a National Instruments 6024 E
acquisition board was used. All the information thus
obtained was send on- line to an application specially
made in LabView software. For the equipment and
devices that were studied a mathematic model was build
in order to run a numerical simulation with the help of
EMTP– ATP software.
A special attention has been given to the electric and
magnetic radiation field of each equipment that has been
part of our study and on how its values are influencing
the equipment or the surrounding equipment behavior
while in service. The present study was based especially
on a successive functioning of the studied equipment
obtaining this way a very good accuracy of the registered
data. An example of successive functioning that has been
studied is the star – delta starting of an electric motor.
Knowing the values of the electromagnetic field is very
important for the exploring staff of the power systems,
from human body and environment exposure point of
view. That is why we consider analyzing the information
contained in the electromagnetic map of the electrical
equipment and devices an important step in the
monitoring and diagnose techniques.
Figure 14. Star – delta motor starting
Figure 15. Contactor starting
6. REFERENCES
[1] Valeriu David, Mihai Creţu – Measuring the magnetic field
intensity (Măsurarea intensităţii câmpului electromagnetic –
Teorie şi aplicaţii), Casa de Editură Venis, Iaşi, 2006
[2] G. Hortopan – Electric Aparatus (Aparate Electrice),
Editura Didactică şi Pedagogică, Bucureşti 1967
[3] A. Baraboi, M. Adam, I. Ciutea, E. Hnatiuc – Tehnici
moderne în comutaţia de putere, Editura A 92, Iaşi 1996
[4] Basics for practical operation, Motor starting, Traditional
motor starting, Soft starters, frequency inverters, Publication
WP Start, EN, January 1998
[5] Monica Rotariu - Experimental and theoretic basis of
electromagnetic radiation field used in monitoring and
diagnose electrical equipment and installation, PhD
Thessis Report, December 2009
Figure 16. Contactor stop
The time that coresponds for the star – delta starting,
the opening and closing of the contactor and also the
amplitude signal for each of these operations are shown
in the next table:
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Scientific Bulletin of the Electrical Engineering Faculty – Year 10 No. 1 (12)
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