2012 1st International Conference on Future Trends in Computing and Communication Technologies
Simulation Analysis of Harmonic Content of Transient
Current During Sympathetic Inrush Current
A.H Hana, N. S. Noorpi, M. Amirruddin, M.M. Nurhakimah
School of Electrical Systems Engineering
Universiti Malaysia Perlis (UniMAP)
Perlis, Malaysia
hanahalim@unimap.edu.my, nursabrina@unimap.edu.my, melaty@unimap.edu.my, nurhakimah@unimap.edu.my
Abstract— This project presents the harmonic analysis in
transient current during inrush sympathetic phenomena. The
objective is to investigate the harmonic content of transient
current during sympathetic inrush current in order to help the
system to supply power to the user without loss and increase
the capacity. IEEE test system used in this project as the basis
for the analysis of relevant circuit current transient, harmonic
and sympathetic inrush phenomenon. Electric power system
embarking test using a single power source that supplies the
two transformers connected in parallel are used to analyze the
ability of using PSCAD software. During sympathetic inrush,
the transformer differential relay may trip because of the maloperation. As to come out with analysis, the power system is
designed for operating voltage and current waves at a fixed
frequency. In inrush current, producing high waves did not
take long time to recover the original wave, but for
sympathetic inrush take a long time or forever. High current
produced from the sympathetic inrush causing the transformer
differential relay power cut off the supply. The result shows
the effectiveness harmonic analysis in transient current during
sympathetic analysis phenomenon modeling by PSCAD
software and analysis the harmonic in this project paper. All
the objectives are achieved in the completion of this project.
regulations [2]. Moreover, the mode of operations of the
system must comply with the conditions set by the
standards, including the process of designing,
manufacturing of equipment. Same as faults in the
equipment cannot completely be excluded because of
technical or human failure. The equipment and installation
cannot be designed to detain any offense and the degree of
damage should be limited.
B. Problem Statement
In any power system network, any forms of fault occur
should be avoided. The protection of the security becomes
the main thing that need to be considered. As in this project,
the content of harmonic analysis of currents during
sympathetic inrush transient phenomenon is being
investigated. Before this topic is studied in detail, what is
the sympathetic inrush? Sympathetic inrush happened when
a transformer inrush is already connected to a supply system
can experience unexpected saturation during the inrush
transient of an incoming transformer. This saturation, which
is established by an asymmetrical voltage drop across the
system resistance caused by the inrush current in the
incoming transformer magnetizing current offset demands
of high magnitude in the already connected transformer [3].
When both transformers arranged in parallel, transformer
that is switched to the network in which the transformer has
a load, the transient inrush currents not only flow through
the transformer at first but it passes through the second
transformer also. This partnership is called the transient
inrush current as sympathetic inrush phenomenon.
The second problem is how to avoid fault at the
transformer differential relay when transient current occurs
in parallel the transformer. The normal inrush current in the
transformers decay, usually, within a few cycles, but the
sympathetic inrush current persists in the circuit for a
relatively longer duration [3, 4]. Longer duration of the
sympathetic inrush current may mal-operate differential
relay. It may also prolong harmonic over-voltages and
causes the over-current harmonic in the system installed [5].
Other than that, noise level is increase in the already
Keywords- transient current; sympathetic; inrush current;
transformer differential relay; PSCAD
I.
INTRODUCTION
A. Background of Project
Modern power system consists of four main parts. These
are known as generation, transmission, distribution and
lastly loads part. The generation, transmission and
distribution parts works together in order to supply power to
the load or consumers. Power system engineering is the
central area of activity for power system planning, project
engineering, operation and rehabilitation of power systems
for electrical power supply [1].
The reliability of the supply is determined not only by the
quality of the equipment but also by carefully planning and
detailed knowledge of power systems, together with a
consistent use of relevant standards and norms, in particular
IEC standards, national standards as well as internal
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2012 1st International Conference on Future Trends in Computing and Communication Technologies
transformers can produce an abnormal flux of higher
magnetizing currents [6]. This can cause a tendency of
operation of the differential protection, that to be avoided
request to insensibility the same during the period of inrush
current duration, but keeping the protection. The capability
of distinguish between the short circuit wave current and the
inrush current. The inrush currents are characterized by
having higher harmonic components that are not present in
short circuit current and whose amplitude in fundamental
percent is shown in Table 1.
connected transformers. Harmonic analysis is an important
point observed in the study of this phenomenon sympathetic
inrush.
II.
HARMONIC IN SYMPATHETIC INRUSH PHENOMENA
It is very well known that a transformer will experience
magnetizing inrush current during energization. A
transformer exhibits an inrush phenomenon during initial
energization. Due to flux symmetry or temporary over
fluxing, this gives rise to high current at the initial
energization of a transformer core [6]. The saturation of one
or more cores results in high magnitude of current [6]. In
high magnitude of current, the transformer energizing current
is full of harmonics. Furthermore, both of the even and odd
harmonics occur during energization [6].
In inrush phenomenon, the transformer which is
connected to the supply system can undergo unexpected
saturation during the inrush transient. This saturation during
the inrush transient was established by the voltage drop
across the resistance and it is not symmetric due to the inrush
current in transformers. Thus, it claims the high magnitude
of magnetizing current balanced in the transformer which is
connected [3].
This partnership transient inrush current is called the
sympathetic inrush phenomenon. The usual inrush current in
transformers decay but only in the course of a continuous
which were sympathetic inrush current in the circuit for a
little longer than the inrush current [3, 4]. Longer period of
the sympathetic current may be mal-operate of the
differential relays [3]. It may also extend the higher of
harmonic over voltages in the system and enhance the level
of noise in the transformer is connected.
In the transformer, energizing a transient inrush current
appears produced by equipment’s core saturation. It has
higher magnitude and it decay after some period of time until
the value of magnetizing current due the normal operation
conditions [3]. Usually, the transformer inrush currents are
calculating as the transformers are connecting to a system
without other transformers on service. In industrial practice,
this equipment are energizing in series or parallel with others
transformers that are on services. This condition can cause a
transient interaction or a sympathetic interaction between the
energizing transformer and the other transformers on service,
which change the magnitude and duration of the inrush
currents. A similar situation can arise in system with higher
series resistances, like some with longer transmission lines.
The inrush current can be affected by different factors
such as the voltage wave point where is energizing the
transformers, the total system impedance through is flowing
the inrush current, the saturation or maximum magnetic flux
densities of ferromagnetic material from transformer core,
the residual flux into the transformer core and its polarities
respect to the first half cycle of alternative flux in steady
state and also the saturation level reach by other transformers
connected to the system.
Therefore, whatever the condition that impose an
instantaneous change on the induction fluxes of power
TABLE I. HARMONIC AMPLITUDE IN PERCENTAGE OF
INRUSH CURRENT FUNDAMENTAL [6]
Harmonic Component
Amplitude
Fundamental)
(%
2
63.0
3
26.8
4
5.1
5
4.1
6
3.7
7
2.4
III.
of
HARMONIC OVERVOLTAGE
A harmonic is a component of a periodic wave having a
frequency which is significant gain of the power line
frequency of 60 Hz base. Total Harmonic Distortion is the
contributed by all harmonics of the fundamental frequency
current [7].
The characteristic harmonics are based on the number of
rectifiers (pulse number) used in a circuit and can be
determined by the following equation:
h = (n x p) ± 1
(1.0)
where; n= an integer (1, 2, 3, 4, 5…)
p= number of pulses or rectifiers
The major cause of harmonics resonance overvoltage
problem is the switching of lightly transformers at the end of
transmission lines [8]. Thereby inrush currents with
significant harmonic content up to frequencies around 600Hz
are created. They can be represented by a harmonic current
source I (h) connected to the transformer bus. The relation
between nodal voltages, network matrix and current
injections can be represented by [9]:
V(h)=Z(h).I(h)
(2.0)
From these equation (2.0), where h represent the
harmonic frequencies f = 120, 180, 240,...Hz. The harmonic
current components of the same frequencies as the resonance
frequency empowered in the case of parallel resonance,
thereby creating a transformer terminal voltage is higher.
This leads to a higher level of saturation cause higher
harmonic components of inrush current, which again will
result in an increase in the voltage [9].
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2012 1st International Conference on Future Trends in Computing and Communication Technologies
IV.
APPROACH AND METHOD
VI.
Generally, this project is involves the development of
software to complete. In the simulation tools and equipment
must be identified. After all requirements sufficient, the
work can be done. The detail description and methodology
are discussed in this part.
The process of the project started from the beginning
part until it being completed. The beginning stage is started
with study the past researches and the data analysis of
previous related works. After it had been done, the next
stage is to understand and to dwell this project and the
simulation software. After all resource has been collected,
the next stage is designing circuit for the simulation result.
For the simulation purposes, the circuit is being designed
at first. Then, the result is simulated by PSCAD software. If
the results are not the same as per expected results, then the
simulation is being redone again and again in order to obtain
the desired results. If the simulation results in accordance
with project requirements, then it can go to the next step.
Comparison data should be made after the simulation is
correct and should be analyzed on the graph in order to
complete the project.
V.
SIMULATION RESULTS AND DATA VERIFICATION
The variation of the harmonic content of transformer
inrush current with time was firstly described. The
magnitude of each harmonic component from 1st harmonic
to 7th harmonic was obtained by doing simulation on
simulation tool. Fig. 2 shows the peak value as a time of the
main harmonic components of the transformer. The peak
value of any harmonic component during operation is totally
different from its peak at each every harmonic. So, these are
no sympathetic interaction and the second harmonic is by
far the dominant one [11].
Fig. 2 represents the value of each harmonic decreased
and returned to its original shape again after the fault occurs.
In this simulation, on the frequency scanner is set to N=7.
That means only seven type harmonic can be scanned by the
scanner for this simulation. The harmonic of order three and
higher show the discontinuities with their peak values going
down to zero and then it increase for oscillating until the
harmonic is lowest when the system is stable.
Fig. 3 shows that the value of at every harmonic has
been scanned during the phenomenon. These harmonics
change their phase shift from positive to negative as their
magnitude passes through to zero. Harmonic content of the
inrush current can cause temporary over-voltages in power
system transmission line.
SIMULATION TOOL
For this power systems protection modeling and
simulation, PSCAD software is used. PSCAD stands for
Power Systems Computer Aided Design. It is a powerful
and flexible graphical user interface to the world-renowned,
EMTDC solution engine. PSCAD enables the user to
schematically construct a circuit, run a simulation, analyze
the results, and manage the data in a completely integrated,
graphical environment [10]. Online plotting functions,
controls and meters are also included, so that the user can
alter system parameters during a simulation run, and view
the results directly [10]. Fig. 1 shows the GUI for PSCAD.
Fig. 2: Result Harmonic when Inrush Current
Fig. 3: The Poly-meter of Harmonic Inrush Current
Fig. 1: GUI for PSCAD Simulation
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2012 1st International Conference on Future Trends in Computing and Communication Technologies
Fig. 7: The Poly-Meter of Each Harmonic
For sympathetic inrush phenomenon harmonic analysis,
the even ordered harmonic component of the supply current
decay rather quickly, where the odd harmonics increase and
continue to be presented for a considerable period of time as
shown at Fig. 8. At the current supply, the amount are from
sympathetic inrush current and inrush current, so it
becoming more symmetric as transformer 1 goes saturated
[11]. Eventually, this current will have no DC neither even
harmonic components, as can be seen in Fig. 8.
This figure shows that these harmonics are negligible
after the 0.0949s. In this case, the peak values of the
harmonic components 2nd harmonic, 3rd harmonic and 5th
harmonic, at the 0.0797s, are respectively 14.05115A,
0.726575A and 1.21141A, showing a significant increase of
2nd harmonic, 3rd harmonic and 5th harmonic when
compared with the case without sympathetic interaction.
Harmonics will be reduced to 0.006 at the time of 0.098s,
and this makes the sympathetic inrush current take a long
time to become a zero.
Fig. 4: Result Total Harmonic Distortion (THD) of Inrush Current
Fig. 4 shows the results of Total Harmonic Distortion
when the system operates without any sympathetic inrush
current. Harmonic is the highest ranked at 0.0931s (X-axis)
is about 30.566 (Y-axis). Harmonics will be reduced to
0.001 at the time of 0.144s, and this makes the inrush
current take of 0.074s. Fig. 5 shows the value of Total
Harmonic Distortion for the inrush current condition. Total
Harmonic Distortion simulation graph for each harmonic
can be seen in Fig. 6 and Fig. 7. 1st harmonic until 7th
harmonic can be viewed the maximum value for each
harmonic type.
It should be noted that this current decays relatively fast,
with its fundamental and harmonic components reaching
relatively low values after 0.925s. At the 0.059, for
example, the three more predominant harmonic components
2nd harmonic, 3rd harmonic and 5th harmonic are
approximately 0.00563A, 8.8164xE-5A and 9.5935xE-5A,
respectively.
Fig. 5: The Poly-meter of THD (Inrush Current)
Fig. 8: Result Harmonic in Sympathetic Inrush Phenomenon
Fig. 6: Result of at Each Harmonic
Fig. 9: The Poly-meter of Harmonic Sympathetic Inrush Current
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2012 1st International Conference on Future Trends in Computing and Communication Technologies
Fig. 10: Result Total Harmonic Distortion (THD) of Sympathetic Inrush
Current
Fig. 12: Result of at Each Harmonic
Fig.9 shows that the value of at every harmonic has
been scanned during the phenomenon. These harmonics
change their phase shift from positive to negative as their
magnitude passes through to zero. Harmonic content of the
inrush current can cause temporary over-voltages in power
system transmission line. Fig. 10 shows the result of Total
Harmonic Distortion when the system operates with
sympathetic inrush current that occurs. Harmonic is the
highest ranked at 0.0954s (X-axis) is about 24.455 (Y-axis).
Harmonics will be reduced to 0 at the time of 0.1085ss, and
this makes the sympathetic inrush current take of 0.0385s.
Fig. 11 shows the value of Total Harmonic Distortion for
the inrush current condition. Total Harmonic Distortion
simulation graph for each harmonic can be seen in Fig. 6
and Fig. 7.
Fig.13: The Poly-Meter of Each Harmonic
Total Harmonic distortion simulation graph for each
harmonic for sympathetic inrush simulation can be seen in
Fig. 12 and Fig. 13. Inspection from Fig. 8, the fundamental
component of the supply current presents a high value and
decays at a relatively very slow rate. This can cause a
prolonged and appreciable transient demand of reactive
power, producing a sustained voltage drop in the system
which may cause load rejection.
VII. CONCLUSION AND RECOMMENDATION
Harmonic traditionally seen as high-frequency
interference not contribute to the dynamics of the system,
and therefore does not have to be considered in stability
analysis. Harmonics are usually regarded as a problem
condition is stable, leading to increasing losses, extreme
heat, and long life components decreased and damage to
sensitive loads. As the harmonic does not affect the stability
of the system, the operating point of a stable steady state is
often assumed in harmonic analysis. A popular method for
the harmonic analysis is a harmonic balance. Harmonic
analysis is a frequency domain method that can be used
repeatedly to find the steady state settlement of nonlinear
networks. Nonlinear loads are modeled as harmonic current
sources in the linear range. In each iteration, node voltages
are calculated by solving the system of linear equations, and
then the non-linear current source voltage node updated
according to the better.
Fig. 11: The Poly-meter of THD (Sympathetic Inrush)
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2012 1st International Conference on Future Trends in Computing and Communication Technologies
REFERENCES
These also demonstrated that the supply current is
greatly affected by of this interaction of the currents that
emerged within the sympathetic magnetism transformer is
connected to the system. The harmonic analysis of supply
current when sympathetic interaction has shown that even
harmonic is ordered this decay of time is quite fast but odd
ordered harmonics increase and remain for a long period of
time. This may evolve substantially temporarily harmonic
overvoltage which may occur in the system. Overvoltage of
this period depends on the essence of transformer saturation
level and pattern of energy losses in the system considered.
When the solution to the problem of harmonics in power
system is required, there are two approaches to this
settlement:
i.
Strengthen the distribution system that the
customer can tolerate the level of harmonic that were
present, while other tools to reduce of harmonic to
acceptable levels.
ii. Filtration current. The filter can be used in various
locations.
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[1]
ACKNOWLEDGMENT
The authors are grateful to thank Universiti Malaysia
Perlis (UniMAP) for providing the technical and financial
support for this research. The financial support through the
Short Term Grant (STG) is highly appreciated. Not to
forget, special thanks to all PPKSE’s staffs and our families
for the constant encouragement. To all of them, the success
of this project is partly due to your support and blessings.
Thank you.
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