HV power distribution system circuit breaker are important devices in substations. Such as Malfunction or deterioration of equipment with in the substation will directing impact on the stability of the power distribution system and affect the reliability of the system. In addition this means that it is necessary to assess the actual condition of the proper condition-based operation and maintenance. Thus this thesis presents condition assessment procedure for equipment by using technical information visual inspection by Weighted Scoring Method. Weighting technique is used to determine important weight testing methods of devices by using Analytic Hierarchy Process (AHP). Testing methods for circuit breaker are such as visual inspection contact timing test. Scoring technique is divided into 1-3 levels by classifying on actual evaluate equipment consisting of consisting of good moderate bad. This thesis proposes a software development in order to organize the database and calculate the analysis of the condition of equipment in 5 HV substations. The evaluation results will be divided into 3 levels good medium and bad condition. According to the evaluation level the maintenance types are separated into 1) regular maintenance 2) increase the frequency of maintenance and monitoring of the test 3) equipment must be improved urgently. Finally abnormal incidents of equipment and cost of HV equipment maintenance can be reduced in effective way.

This paper presents how to design and build electrical protection equipment to apply for a wind turbine generator system which is modeled on low voltage 3 phase 380 volts system. This electrical equipment acts as a switch to open-close an electrical circuit to prevent an electrical system as well as equipments or devices in the system. It will open the circuit quickly and decrease the contact arcing of a circuit breaker. The implementation of power electronic properties is used instead of mechanical parts which is called “Solid-State Beaker”. This article presents a method of solid-state breaker simulation on the mathematical analysis via MATLAB/ Simulink program in the cases of fault occurring in an electrical system. The simulation is used as a comparison when it is brought into the system. The fault voltage is detected by RMS Method which is implemented in LAB View program. The detection signal will be sent to the solid-state breaker and order it to cut off all three lines simultaneously to confirm the efficient running of solid- state breaker. But this paper has not yet considered the effect of Harmonic.