Design analysis and optimization of ground grid mesh of extra high voltage substation using an intelligent software

Abstract

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.

Review of Substation Grounding System Behavior Under High Frequency and Transient Faults in Uniform Soil

“…This section confers the impact of grid size on grounding grid impedance. Grid size is the total size of conductors covered by the grounding grid [81]- [83]. Fig.…”

“…Grid mesh density can vary uniformly across the grid or it may be enhanced locally within areas of the grid. Mesh density exerts a significant effect at an intermediate frequency, under which it is determined by soil resistivity [83], [86]- [89]. Fig.…”

Investigation of overvoltage on square, rectangular and L-shaped ground grids of high voltage substations by ATP/EMTP

“…Interestingly, the use of CDEGS program could help to create the 3D plots of power plant's grounding system that was struck by lightning current and illustrate that the scalar potentials and electric fields were seriously affected [13]. In addition, the electrical transient analyzer program (ETAP) was used to optimize the similar parameters, especially the conductors' types, lengths, depths, and sizes [14]- [16].…”

Reducing the Effect of Lightning on Step and Touch Voltages in a Grounding Grid Using a Nature-Inspired Genetic Algorithm With ATP-EMTP

“…In [11] and [12], TRAGSYS and ETAP software were used, respectively, to manage the safety of a human body against various dangers such as lightning striking the grounding grid.…”