In this study, typical cases are combined to analyze the technical requirements for the TN-S system to prioritize the use of short-circuit overcurrent protection over ground fault protection. The necessity of adopting residual current action protection as ground fault protection is elucidated, as well as the importance of auxiliary equipotential bonding in reducing contact voltage. Various protective measures are proposed along with their respective roles and applicable conditions. The analytical process and resulting conclusions hold significant importance for grounding fault protection in engineering design and application.

In this paper, a novel reconstruction design scheme is proposed to converter a solar water heating(SWH) system into a PV power generation system with the same annual savings as standard coal. The idea of this paper is based on a practical project in China. Differing from the traditional design of the PV power generation system, the design and performance of SWH systems are firstly analyzed, following the reconstruction of the PV power generation system. In order to guarantee the same production capacity of electric energy, the key issues concerning the installed capacity of the PV power generation system, the equipment choices of the PV modules, inverters, cables and grid-connected circuit breakers. Meanwhile, some key issues affecting the system's implementation and safety, such as the installation angle of PV arrays and lightning protection, have also been investigated. In order to validate this paper, comparative data concerning the generated power energy and income is estimated to show the effectiveness of the reconstruction design scheme.