The 500KV substations are important for power system in Pakistan. They cover large area meeting the power requirement of whole power system. The ground grid system of substation has to be carefully analyzed in order to protect the grid, keep the system functional. A practical 500KV substation is chosen for this purpose i.e. RA WAT Grid Station. The grounding system of substation is studied in detail along with practical data collection for the purpose of analysis. It is important to mention about latest IEEE 81 2013 methods which have been adopted during data collection phase. The ETAP software version 12 is used for modeling and analysis of network. The Ground Grid System (GGS) module included in latest version of ETAP i.e. ETAP 12 is used for analysis. Firstly modeling is done in ETAP-12, afterwards analysis is performed on actual ground mesh using IEEE 80-2000 improved methods to evaluate step potential, ground potential rise, ground resistance, short term temperature rise of conductors Irods & touch potential. The shortcomings in existing grid mesh are highlighted and remedial actions are suggested to rectify the problems. The extension is planned in the substation regarding installation of new power transformer which will result to in rise of overall substation fault level. The increase in fault level is considered in one case study and possiblesolution is provided. A new ground mesh is also designed for this area which will serve as a model for future substations which will be designed in this particular area keeping in view essential parameters. A new ground mesh is also designed for 750KV substation, as it will be part of our national grid in near future as feasibility study is ongoing in NTDC Pakistan for the establishment of first 750KV substation in this area. The variation in ground grid resistance and various safety parameters with the change in ground grid mesh shape, depth and size is explained by the help of results obtained through Case studies.

An Air Insulated substation is chosen for the analysis located in

This paper gives comparative analysis between Synchronous Pulse Width Modulation (SPWM) and square wave output filtration based pure sine wave inverter. The paper also explains the detailed working of square wave output filtration based pure sine wave inverter. The SPWM based technique uses varying pulse at gate of power devices which can be generated through microcontroller according to requirement of output. The square wave output filtration based technique uses simple pulse which can be generated from multi-vibrator and output is filtered using Chebyshev's low pass filter to generate pure sine wave. The results of both types of techniques are tested using Simulink.

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