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com Volume 5 Issue VI, June 2017
IC Value: 45.98 ISSN: 2321-9653
International Journal for Research in Applied Science & Engineering
Technology (IJRASET)
Differential Protection of Power Transformer
Using Simulink
Mandeep Singh1, Harjit Singh Kainth2
1
M. Tech Student, Arni University Kangra, India
2
Assistant Professor, Arni University Kangra, India
Abstract: In this research work we propose a simple and effective technique based on the Clark’s transformation. Which
avoiding the mal-operation of differential protection relays during inrush currents and trip signal generated during occurrence
of other internal faults. This paper presents a technology to simulate differential relay in Simulink based environment for
determining its behavior during various operating conditions. The results show that this simulation model works properly and it
gives satisfactory results.
Keywords: Transformer, Differential Protection, Simulink Model, Different Fault Conditions and Results.
I. INTRODUCTION
Transformer is the most important unit in an electrical transmission and distribution networks. The unexpected outage of a power
transformer is costly for utilities and consequently requires sufficient protection [1]. It is essential to study the different working
conditions of transformer to discover new protection method [2]. A power transformer functions as a node to connect two different
voltage levels. Therefore, the continuity of transformer operation is of vital importance for maintaining the reliability of power
supply. Any unscheduled repair work, especially replacement of faulty transformer is very expensive and time consuming. As a
result, their protection is of great importance to assure stable and reliable operation of the whole system. Power Transformer is one
of the most cost effective components in an electric power system. Any damage to it can cause irreparable damage resulting in
replacement or high cost for repairs if possible. Thus protection of transformers becomes a critical issue related to power system.
Thus it becomes very essential that the transformer is protected from various possible failures. Transformer protection has always
been a challenging problem for protection engineers. The faults occur in transformer are open-circuit faults, earth faults, phase to
phase faults, over heating faults and inter-turn faults. Inter phase short circuit are most frequent on leads of three phase transformer,
while the inter phase short circuit within the winding are less frequent. Earth fault and inter-turn fault have the highest probability
on the transformer. Winding short circuit also called as the internal faults, usually result from failure of insulation due to
temperature rise or deterioration of transformer. The conventional technique used for transformer protection is current differential
protection, which is used for protecting the transformer windings against internal faults [3].
II. DIFFERENTIAL PROTECTION
One of the most effective methods of protection to protect power transformers is the differential protection method by using
differential relay circuits. This scheme is based on the principle of that the power input to the transformer under normal conditions is
equal to the power out. By proper connection of the secondaries of current transformers, under normal conditions, no current will
flow into the relay coil. On every occasion when a fault take place the current balance will no longer exist and relay contacts will
close and release a trip signal to cause a certain circuit breakers to operate in order to disconnect the faulty equipment [4]. The
Power Transformer protection scheme would be such that it avoid and block the tripping of differential relay during magnetizing
inrush & over excitation and should speedily operate the relay tripping during internal faults. For this reason, it is required to choose
an appropriate identification scheme which can make a distinction and discriminate the magnetizing inrush over excitation and
internal fault current. Percentage restraint differential protective relays have been in service for many years [5]. Figure 1 shows the
digital differential protection of power transformer.
1952
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www.ijraset.com Volume 5 Issue VI, June 2017
IC Value: 45.98 ISSN: 2321-9653
International Journal for Research in Applied Science & Engineering
Technology (IJRASET)
Fig. 1 Differential Protection scheme [6]
III. SIMULINK MODEL
In this model three phase star-star connected transformer is protected. Figure shows the simulated power system built in
Matlab/Simulink environment.
Fig. 2 Simulink Model for differential protection of transformer
1953
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www.ijraset.com Volume 5 Issue VI, June 2017
IC Value: 45.98 ISSN: 2321-9653
International Journal for Research in Applied Science & Engineering
Technology (IJRASET)
IV. RESULTS
There are various cases are studied in my research work. Like magnetizing inrush current, each phase to ground, phase to phase and
three phase to ground. Here I discussed only three results.
A. For Phase to Ground Fault
Differential protection scheme when there is phase A to ground fault is occurred. It gives satisfactory results.
Fig. 3 Phase A to ground fault
Fig. 4 Trip signal for phase A to ground fault
1954
©IJRASET: All Rights are Reserved
www.ijraset.com Volume 5 Issue VI, June 2017
IC Value: 45.98 ISSN: 2321-9653
International Journal for Research in Applied Science & Engineering
Technology (IJRASET)
B. For Phase-Phase Faults
Differential protection scheme when there is phase A to phase B fault is occurred and it gives satisfactory results.
Fig. 5 Phase A to Phase B fault
Fig. 6 Trip signal for phase A to phase B fault
1955
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www.ijraset.com Volume 5 Issue VI, June 2017
IC Value: 45.98 ISSN: 2321-9653
International Journal for Research in Applied Science & Engineering
Technology (IJRASET)
C. For Three Phase to Ground Faults
Differential protection scheme when there is phase ABC to ground fault is occurred and it gives acceptable results.
Fig. 7 Phase ABC to ground fault
Fig 8. Trip signal of three phase to ground fault
V. CONCLUSION
This research paper presents a method for differential protection power transformer based on the application of Clarke’s
transformation which gives better performance over the conventional techniques. The obtained result shows that the proposed
differential protection method avoids the tripping of the circuit during magnetizing inrush current situation and trips the protection
scheme during the fault state. Thus the use of Clarke’s transform can make it possible to increase reliability and sensitivity of
differential relays for power transformer.
1956
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IC Value: 45.98 ISSN: 2321-9653
International Journal for Research in Applied Science & Engineering
Technology (IJRASET)
A. Summary for All tested cases
Cases Result
Inrush current No trip
Phase to ground fault Trip
Phase to phase fault Trip
REFERENCES
[1] S.V.Kulkarni,S.A.Khaparde, Transformer Engineering. Design and Practice, Marcel Dekker Inc., New York, Basel, 2004.
[2] Haihui Song, Fangming Zhao, Di He, “Simulation study on internal fault of Transformer ” Elsevier, sciverse science direct, 2012 international conference on
solid state devices and material science, Physics Procedia 25 (2012) pp 459-46
[3] Moravej, Z., Vishvakarma D. N., and Singh S. P. “Digital filtering algorithms for the differential relaying of power transformer: an over view,” Electric
Machines and Power Systems, vol. 28, pp.485-500, 2000
[4] Adel Aktaibi and M. Azizur Rahman, “Digital differential protection of power transformer using MATLAB”, Chapter 10, Intech publications.
[5] A.Guzman, S. Zocholl, and H. Alturve “performance analysis of traditional and improved transformer differential protective relays”, SEL Paper, 2000.
[6] M. A. Rahman and B. Jeyasurya, “A state-of-the-art review of transformer protection algorithms”, IEEE Trans. Power Delivery, vol. 3, pp. 534–544, Apr.
2011.
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