دانلود رایگان مقاله گزینه طراحی برای تشخیص خطا امن و مسائل ایمنی در سیستم PV

abstract

Photovoltaic systems have played a key role over the last decade in the evolution of the electricity sector. In terms of safety design, it’s important to consider that a PV plant constitutes a special system of generation, where the Direct Current (DC) presence results in changes to the technical rules. Moreover, if certain electrical faults occur, the plant is a possible source of fire. Choices regarding the grounding of the generator and its protection devices are fundamental for a design that evaluates fire risk. The subject of the article is the analysis of the relation between electrical phenomena in PV systems and the fire risk related to ensuring appropriate fault detection by the electrical protection system. A description of a grid-connected PV system is followed firstly by a comparison of the design solutions provided by International Standards, and secondly by an analysis of electrical phenomena which may trigger a fire. A study of two existing PV systems, where electrical faults have resulted in fires, is then presented. The study highlights the importance of checking all possible failure modes in a PV system design phase, to assess fire risk in advance. Some guidelines for the mitigation of electrical faults that may result in a fire are finally provided.

Conclusions

A PV plant is a special generation system in which the presence of DC results in changes to the application of general technical rules. Moreover, if certain electrical faults occur, the system itself can become a possible source of fire. The layout of the system, the grounding of the negative pole of the DC side and the means of protection are all vital concerns affecting the design of a system that accounts for the risk of fire. In this paper, the design solutions provided by different International Standards have been studied and their safety performances compared. The effect of electrical faults in PV systems is significantly governed by these standards and an analysis of the relation between the faults and the related means of protection has been presented. The focus has then on two case studies of existing grounded PV systems in the USA, in which electrical faults have resulted in the development of fires. In both case studies, the analysis suggests that the fire was caused by a blind spot in the protection device used as ground-fault protection. This evidence emphasizes the importance of checking all possible failure modes in a PV system in its design phase, in order to prevent fire due to blind spots. The most reliable solution for the avoidance of blind spots is to install multiple small inverters and to combine two devices: an IMD device to monitor the insulation resistance of the system, and a RCM device sensitive to DC Although the Standards still do not clearly require the use of a RCM to protect grounded PV arrays, it is currently the only device able to detect small DC ground-fault currents.