Electricity Generating Authority of Thailand (EGAT) encountered problems voltage swell from the changes of power system configuration high-voltage 115 kV substation name Lopburi2 to radial. Control Center closed capacitor bank caused the steel industry electric power plants and renewable energy solar tripped themselves out. As a result EGAT loosed of power produced of solar power plants. It also affected confidence in the systems power consumption. EGAT’s necessary to learn from this event. This research was simulation power system modeling of “High Voltage Substation Lopburi2” and grid connection both the system EGAT and PEA with EMTDC-PSCAD for analysis of the voltage swell caused by close capacitor bank at “Lopburi2” substation compared with actual events then calculated the voltage swell occurred at high voltage station linkage. Finally this research presents a method of reduction of their impact of close capacitor bank at “Loburi2” to avoid the voltage swell in the future.

This research presents the studying of short circuit in distribution system that affect to critical equipment voltage sag and overvoltage while short circuit event. Lead into the quality of electric user. Effect on economics damaged Distribution system voltage level 22kV of The Provincial Electricity Authority. It is the analysis model by computer program. The event of short circuit set in a many distribution systems. The analysis result Magnitude of voltage while short circuit bring to assessment voltage sag and overvoltage from average voltage of the repeat event. Then set boundary of voltage at load point in a many. The experiment shows the problem of the quality of electric be affect to critical equipment less than load point close connection with substation.

The faults in a power distribution system do not only impact to power outage directly. They also cause voltage sag problem spread over the system. A single-line to ground fault is about 70% of the overhead system faults. The magnitude and duration of voltage sag causes the economic damage of the system. This paper presents an analysis of the different systems grounding to mitigate the voltage sag in a power distribution system by using the technical analysis system in case of one phase to ground fault. The objective is to minimize voltage drop for users using the simulation with single line to ground fault in distribution system voltage level at 22 kV PEA’s test system by the computer program. The results show that the grounding method can mitigate the voltage sag and reduce the damage of the economic system.

This Research purposes assessment of lightning performance on transmission system 69 kV in Metropolitan Electricity Authority (MEA). The case studies illustrated the lightning strike to direct top pole in order to guideline considering the critical flashover voltage value of insulator is able to withstand it and improvement lighting protection in the future. This solution analyzes using the Alternative Transient Program-Electromagnetic Transient Program (ATP-EMTP). The result found that voltage across insulator before and after improvement lightning protection by external ground wire. Factor effect to voltage across the insulators is the tower footing resistance wave of lightning current and interval between towers. It depends on relation with front time of wave. The analysis economics is very important. This Research is studying interruption cost of outage since back flashover so analysis the break even point of the installation external ground. The result found upon improvement lightning protection by installed external ground. The pay back period of that is 9 years installed ago. This result can conclusion is external ground able reduction interruption costs of outage.