Low voltage direct current switches and their standards in photovoltaic applications

Abstract

The increasing amount of PV installations has pushed the standard writers to clarify and add demands for the switches used in this application because of direct current, installa-tions and safety. These devices are manufactured at ABB Oy Vaasa, Breakers and Switches unit. The purpose of this thesis is to study the new PV application specific standards and to find trends in the changes made, and to consider performance requirements for future products. Additionally, the changes in demands to PV specific standards are compared and reasons for these are discussed. The background for this work is the literature concerning PV systems, the LV DC switch standards, and standards concerning PV installations and safety. Especially, the PV application specific LV DC switch standards are examined. This work was started by the proposal of an amendment to IEC 60947-3 and how it affects the LV DC switch products. In addition to the European IEC standards, this work studies the demands for LV DC switches set by the American standardising agency UL. The results of this thesis are the development trends found in the standardisation of switches used in PV applications. Additionally the reasons for changes are studied and presented. The demands and differences are considered in the text and compared with the help of the standards and comments given by products specialists. The compliance of present day products to current demands is considered, and also, properties the future products should have. It is observed that changes in all standards have taken into ac-count the temperatures in the environment.