**9. References**


into a computer for data processing. Waveforms data are divided in two groups. One group is used to estimate models whereas the other group to validate models. The developed programming determines various model waveforms and search for model waveforms of maximum accuracy compared with actual waveforms. This is achieved through selecting model structures and adjusting the model order of the linear terms and nonlinear estimators of nonlinear terms. The criteria for selection of a suitable model are the "Best Fits" as

After obtaining appropriate models, analysis and prediction of power quality are carried out. Modeled output waveforms relating to power quality analysis are determined from different scenarios. For example, irradiances and ambient temperature affecting DC PV outputs and nature of complex local load can be varied. From the model output waveforms, determination is made on power quality aspects such as voltage level, total harmonic distortion, complex power, power factor, power penetration and frequency deviation.

Such modelling techniques can be used for system planning, prevention of system failures and improvement of power quality of roof-top grid connected systems. Furthermore, they are not limited to PVGCS but also applicable to other distributed energy generators

The authors would like to express their appreciations to the technical staff of the CES Solar Cells Standards and Testing Center (CSSC) of King Mongkut's University of Technology Thonburi (KMUTT) for their assistance and valuable discussions. One of the authors, N. Patcharaprakiti receives a scholarship from Rajamangala University of Technology Lanna (RMUTL), a research grant from the Energy Policy and Planning Office (EPPO) and Office of Higher education commission, Ministry of Education, Thailand for enabling him to pursue his research of interests. He is appreciative of the scholarship and research grant

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**4** 

*1Petru Maior University,* 

*Romania* 

**Reliability Centered Maintenance Optimization** 

Dorin Sarchiz1, Mircea Dulau1, Daniel Bucur1 and Ovidiu Georgescu2

A basic component of the power quality generally and electricity supply in particular is the management of maintenance actions of electric transmission and distribution networks (EDS). Starting from this fact, the chapter develops a mathematical model of external interventions upon a system henceforth, called Renewal Processes. These are performed in order to establish system performance i.e. its availability, in technical and economic imposed constraints. At present, the application of preventive maintenance (PM) strategy for the electric distribution systems, in general and to overhead electric lines (OEL) in special, at fixed or variable time intervals, cannot be accepted without scientifically planning the analysis from a technical and economic the point of view. Thus, it is considered that these strategies PM should benefit from mathematical models which, at their turn, should be based, on the probabilistic interpretation of the actual state of transmission and distribution installations for electricity. The solutions to these mathematical models must lead to the establishment objective necessities, priorities, magnitude of preventive maintenance actions and to reduce the life cycle cost of the electrical installations (Anders

Based on the definition of IEC No: 60300-3-11 for RCM: "method to identify and select failure management policies to efficiently and effectively achieve the required safty, availability and economy of operation", it actually represents a conception of translating feedback information from the past time of the operation installations to the future time of

So, Reliability Based Maintenance (RCM) implies planning the future maintenance actions ( T<sup>+</sup> ) based on the technical state of the system, the state being assessed on the basis of the estimated reliability indices of the system at the planning moment ( <sup>0</sup> T ). At their turn, these reliability indices are mathematically estimated based on the *record of events*, that is, based on previously available information, related to the behaviour over period ( T<sup>−</sup> ), i.e. to the


**1. Introduction** 

et al., 2007).

**1.1 General considerations and study assumptions** 

their maintenance, grounding this action on:

( <sup>0</sup> T ) moment, concordant with Figure 1.

**of Electric Distribution Systems** 

*2Electrica Distribution and Supply Company* 

