© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1467 Modeling and Analysis of a 3-Phase 132kv GasInsulated Substation Lalit Patil 1 , Jigisha Ahirrao 2 , Mangesh Mondhe 3 & Roshni Patil 4 ------------------------------------------------------------------------***------------------------------------------------------------------------ Abstract: -- This paper introduces Modeling of a 3- Phase 132kv Gas Insulated Substation. Such over voltages can cause mal functioning of protection circuits and control circuits and also initiates faults and influence on other components such as transformers. For designing a substation it is essential to know the maximum value of VFTO. Hence studies are carried out on estimation of the VFTO levels. For this purpose MATLAB 7.8 can be used. In MATLAB 7.8 simulation a suitable equivalent circuit is necessary for each component of the substation. Analysis of Very Fast Transient Overvoltage has been carried out using MATLAB7.8 for various switching conditions in a 3- phase 132kV gas insulated substation. Keywords— , MATLAB 7.8 software and Control circuitry,Gas Insulated Substation (GIS), Very Fast Transient overvoltages, Switching operations, 3 phase fault I. INTRODUCTION Gas Insulated Substations (GIS) have found a broad range of applications in power systems over the last three decades because of their high reliability, easy maintenance, small ground space requirement etc.. In our country also, a few GIS units have been in operation and a large number of units are under various stages of installation[1]. GIS is based on the principle of operation of complete enclosure of all energized or live parts in a metallic encapsulation, which shields them from the external environment[2]. Compressed SF6 gas, which has excellent electrical insulating properties, is employed as the insulating medium between the encapsulation and the energized parts. Gas Insulated Substations have a grounded outer sheath enclosing the high voltage inner conductor unlike conventional equipment whose closest ground is the earth surface[3][4]. The Basic Insulation Level (BIL) required for a Gas Insulated Substation (GIS) is different from that of the conventional substation because of certain unique properties of the former[5]. Gas insulated bus has a surge impedance (70 International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 09 Issue: 08 | Aug 2022 www.irjet.net p-ISSN: 2395-0072 Ohm) more than that of the conventional oil filled cables, but much less than that of a over head line (300 – 400 Ohms)[6]. In addition, the GIS is totally enclosed and therefore is free from any atmospheric contamination. Hence, in general the GIS permit lower BIL rating than the conventional one. A GIS requires less number of lightning arresters than a conventional one[7]. The representation of bushing is important for simulating the fast transients. Generally, the transit time through a bushing is comparable to or greater than the rise time of GIS generated transients. For this reason, bushings cannot be considered as a lumped element in estimating the VFTO level. The generation of fast transients can be classified into two types. They are due to the following: a) Dis-connector switch operation b) Faults between Bus bar and Enclosure In case of 3-phase fault, the voltage collapse at the fault location occurs in a similar way as in dis-connector gap during re-striking. By this event, step shape traveling surges are injected. For such a surge source inside GIS, two surges traveling in opposite directions are generated. However, if voltage collapse occurs at the open end of GIS, only single surge propagates on the bus[8]. During recent field tests on a 132KV substation, measurements were made of the trapped charge left when a DS was opened onto a floating section of switchgear. Numerous measurements led to the conclusion that for this switch, a potential of 0.1 – 0.2p.u is left on the floating section and that this result is consistent [9][10]. II. ESTIMATION OF 132KV GAS INSULATED SUBSTATION During the switching operation of the circuit, the transients are developed. By the calculated values of the circuit parameters in previous chapter, the equivalent circuits are constructed by using MATLAB 7.8 software. By using the circuits the transients are calculated for different lengths of Gas insulated substation. The transients are also calculated during the faults with and without load at different distances.