designing and testing of metal oxide surge arrester for ehv line

Designing and testing of metal Designing and testing of metal oxide surge arrester for EHV lineoxide 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

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

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.

IntroductionIntroduction

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

Other device similar to arresterOther device similar to arrester

Simulation results

Simulation model of MO arrester

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.

IEEE model

Fig (a) Frequency dependent model

Proposed model

Fig(b) Proposed model

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.

Parameter identification

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

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

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

(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

(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.