Surge arresters constitute an indispensable aid to insulation coordination in electrical power systems. There the voltages which may appear in an electrical power system are given in per-unit of the peak value of the highest continuous line-to-earth voltage, depending on the duration of their appearance. The voltage or overvoltage which can be reached without the use of arresters is a value of several p.u. If instead, one considers the curve of the withstand voltage of equipment insulation (here equipment means electrical devices such as power transformers) one notices that starting in the range of switching overvoltages, and especially for lightning over voltages, the equipment insulation cannot withstand the occurring dielectric stresses. At this point, the arresters intervene. When in operation, it is certain that the voltage that occurs at the terminal of the device - while maintaining an adequate safety margin - will stay below the withstand voltage. Arresters’ effect, therefore, involves lightning and switching over voltages. The time axis is roughly divided into the range of lightning overvoltage (microseconds), switching overvoltages (milliseconds), temporary overvoltages (seconds) – which are commonly cited by the abbreviation "TOV" – and finally the temporally unlimited highest continuous system operation voltage.

1. Designing and testing of metal oxide
surge arrester for EHV line
MASTER
OF
ENGINEERING
IN
ELECTRICAL ENGINEERING
Specialization
in
(High voltage and power system)
Submitted by –ROHIT KHARE
Roll no-0201EE09ME32
Under the guidance
of
Dr. A.K SHARMA

2. Contents
 Abstract
 Introduction
 Arrester application in general
Considerations on protective characteristics
 Arrester design (Station arresters)
Porcelain housed
Polymer housed
 Configuring arrester
Electrical and Mechanical data
 Simulation results
 Conclusion

3. Abstract
 Surge arresters protect equipment of transmission and distribution
systems, worth several magnitudes more than the arresters themselves,
from the effects of lightning and switching overvoltages. If properly
designed and configured, they are extremely reliable devices, able to
offer decades of service without causing any problems. This thesis
presents information about the basic electrical characteristics and designs
of modern metal-oxide surge arresters with the help of model simulated
in MATLAB simulink software. In addition to the standard application –
protection of power transformers – examples are provided, in which
arresters help to reduce investment, repair and maintenance costs. This
benefit can be augmented when arresters are combined with other
equipment such as post insulators, disconnectors or earthing switches.

4. Introduction
Device used on power system above 1000V to protect other
equipment from lightning and switching surge.

5. Other device similar to arrester

72. Simulation results

73. Simulation model of MO arrester

75. The graph represents the change in voltage and current w.r.t
time. In this graph the propagation time duration between 0.02
to 0.04ns voltage varies between 0.5 to 1 105 kV but the current
is zero. After 0.04ns the current changes in phase with voltage
and when the voltage exceeds the limit of 1kV the peaks appears
in current between 5 kA and 10 kA. The discharging current
increases with increase in value of voltage which exceed the limit
of 1.5 105 kV. But after 0.1 ns graph shows that stable condition
will be achieved when discharging current becomes zero.

76. Conclusion

77. A model for metal-oxide surge arresters, derived from that one
recommended from the IEEE, is presented. The main innovation introduced by
the thesis lays in the simplicity of the criteria proposed for the model’s
parameter identification. Such criteria allow calculating the model parameters
directly from the standard data reported in the arrester data-sheets with a
simple and straightforward procedure. Although metal-oxide arresters (MOA)
were introduced on the market several years ago, their modeling is still a
problem. Several accurate models have been proposed to describe the arrester
behavior for different kinds of stress. The hard point is the identification of the
model parameters, and the need of field tests or of trial-and error procedures to
determine acceptable values. As a matter of fact, due to these difficulties only
arrester manufacturers or specialized laboratories have today the real
possibility of performing overvoltage co-ordination studies.

78. The goal of this thesis is to present a model for MOA, and to
propose a simplified and/or better procedure for its parameter
identification. The procedure to identify the model parameters
matches the following requirements:
I. All necessary data are reported on manufacturer’s catalogues
or data-sheets;
II. Model’s performances match the real device behavior for
surge arresters of different model and from various
manufacturers.

79. IEEE model
Fig (a) Frequency dependent model

80. Proposed model
Fig(b) Proposed model

81. By comparing the models in Fig.(a) and in Fig.(b), it can be
noted that:
• The capacitance is eliminated, since its effects on model
behavior negligible
• The two resistances in parallel with the inductances are
replaced by one resistance R (about 1 MΩ) between the input
terminals, with the only scope to avoid numerical troubles. The
operating principle is quite similar to that of the IEEE frequency-
dependent model.

82. Parameter identification
Fig (c). Static characteristics of the non-linear elements. The voltage is in p.u. referred to the Vr8/20.

83. Where:
Vn = is the arrester rated voltage
V r/T2 = residual voltage at 10 kA fast front current surge
(l/T2µs). The decrease time is not explicitly written because
different manufacturers may use different values. This fact does
not cause any trouble, since the peak value of the residual
voltage appears on the rising front of the impulse.
V 8/20µ s = residual voltage at 10 kA current surge with a 8/20µs
shape.
Parameter identification

84. The proposed criteria does not take into consideration any
physical characteristic of the arrester. Only electrical data are
needed. The above equations are based on the fact that parameters
Lo and L, are related to the roles that these elements have in the
model. In other words, since the function of the inductive elements
is to characterize the model behavior with respect to fast surges, it
seemed logical to define these elements by means of data related to
arrester behavior during fast surges.
Parameter identification

85. (1) Hileman, J. Roguin, K.H. Weck - Protection performance of metal
oxide surge arresters - Electra No. 133, pp.132 - 143, December 1990.
(2) IEEE W.G. 3.4.1 1 of Surge Protective Devices Committee – Modeling
of metal oxide surge arresters - IEEE Trans. on Power Delivery, Vol. 7,
NO. 1, pp. 301 - 309, January 1992.
(3) E. C. Sakshaug, J. S. Kresge, S. A. Miske“A new Concept in Station
Arrester Design” IEEE Transactions on Power Apparatus and
Systems, Vol. PAS-96, no. 2, pp. 647 – 656, March/April 1977.
References

86. (4) Ikmo Kim, Toshihisa Funabashi, ... - Study of ZnO arrester model for
steep front wave - IEEE Trans. on Power Delivery, Vol. 1 1 , No. 2, pp.
834 - 84 1, April 1996.
(5) CIGRÉ Working Group 33.06“Metal-oxide surge arresters in AC systems
ELECTRA 128, pp. 99-125, July 2000.
(6) CIGRÉ Working Group 33.06 Metal-oxide surge arresters in AC systems
ELECTRA 130, pp. 78-115 July 2000,
(7) CIGRÉ Working Group 33.06Metal-oxide surge arresters in AC systems
ELECTRA 133, pp. 133-165, July 2000.
References

87. Thank You