The stressful condition of power system and high transmission losses leads to voltage security and reliability problems of system operation. If the voltage stability is not assessed and the problems occurred are not mitigated properly, cascading events may occur and this may lead to voltage collapse or blackout events. Therefore, there is a need to assess the voltage stability in order to detect the voltage collapse point and mitigate it when it occurs. This paper aims to compare four existing voltage stability index performance towards reactive and real power load changes. The performances are analyzed theoretically, and using simulation on IEEE 30-bus test system. Total power loss is also observed for each case. The comparison shows that all indices are prone to either reactive or real load power changes only. None of the indices are sensitive towards both power loads changes. Meanwhile, the total power loss is mostly contributed by reactive power losses. Index Terms-Line Stability Index, Voltage stability analysis, Voltage Collapse, Maximum permissible load

A model-based system for fault diagnosis in power system is presented in this paper. It is based on fuzzy timing Petri net (FTPN). The ordinary Petri net (PN) tool is used to model the protective components, relays, and circuit breakers. In addition, fuzzy timing is associated with places (token)/transition to handle the uncertain information of relays and circuits breakers. The received delay time information of relays and breakers is mapped to fuzzy timestamps,π(τ), as initial marking of the backward FTPN. The diagnosis process starts by marking the backward sub-FTPNs. The final marking is found by going through the firing sequence,σ, of each sub-FTPN and updating fuzzy timestamp in each state ofσ. The final marking indicates the estimated fault section. This information is then in turn used in forward FTPN to evaluate the fault hypothesis. The FTPN will increase the speed of the inference engine because of the ability of Petri net to describe parallel processing, and the use of time-tag data will cause the inference procedure to be more accurate.

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This paper presents a designing piezoelectric harvesting energy device by having mechanical stressWhole system of the designing must be verified and validated through extensive experimental tests. The system structure consists of controller circuit that uses to simulate the system and show the amount of voltage. This generated electrical energy can be harvested using the principle of piezoelectric energy conversion. The propose design is divided into three categories, which are designing the prototype, electronic part and mechanical part. Designing proper mechanisms for exciting the piezoelectric device is necessary also proper electronic control circuits must be designed and modeled. It is used before implementing to the energy storage using a typical bettery. The project gives a new idea to develop a renewable energy as an electrical power system that can generate a power from having a lot of force from people moving so that they would not only depend on the hydro and coal power system.