1 FUNCTIONAL REQUIREMENTS OF SMART GRID PROTECTION Kimmo Kauhaniemi and Sampo Voima University of Vaasa kimmo.kauhaniemi@uwasa.fi Finland ABSTRACT – In this paper the functional requirements of the Smart Grid protection are discussed. These requirements arise from specific features of the Smart Grids. For example, Smart Grids include various types of distributed energy resources, which enable more flexible use of grid capacity. With the help of modern ICT technology it is also expected that the power supply reliability is shifted to some higher level. Especially in the distribution system level the changes will be relatively big. The traditional distribution systems are more or less passive while the Smart Grid technology brings in new active elements. The state of the system will be continuously changing and in order to set up suitable protection system some new requirements must be taken into account. The functional requirements of the protection future Smart Grids, especially for the smart distribution networks, are discussed in this paper by analyzing a fixed set of different types of basic protection zones. Keywords: Smart Grids, protection INTRODUCTION There are slightly varying definitions for Smart Grid, but the main characteristics are usually the same. One of the key features of Smart Grids is that it employs wide variety of distributed energy resources (DER). These include distributed generation (DG), energy storages (ES) and active customers. In practice active customers means primarily the demand response (DR). In this paper the focus is on distribution networks where the increasing local generation requires new type of approaches for the protection. But this is not the only thing that comes with the Smart Grid. With the help of modern ICT technology it is expected that the power supply reliability is shifted to some higher level. In distribution system this means increased automation deeper in the system. One way to achieve better reliability is the smart way of sectionalizing the network. With suitable design of the protection zones the self- healing functionality of distribution system can be enhanced. In practice the self-healing functionality means that the protection system first locates the fault accurately and then disconnects the faulted section after which the intelligent automation functions take care of restoring the power supply to the healthy parts of the network. In this paper the functional requirements of the Smart Grid protection are discussed considering different affecting aspects of the future Smart Grid. This paper is prepared as a part of a national Smart Grid project in Finland, the SGEM (Smart Grids and Energy Markets) project, and thus the present protection practices applied in Finland are used as starting point. The focus is on the distribution systems and especially in the medium voltage (MV) level where relay protection is applied. The analysis presented in this paper can also be applied at the low voltage (LV) level where the protection is still mainly based on fuses. At first the present protection system practice in Finland is reviewed and an introduction to the main features of Smart Grid is given. After that the main elements of the smart protection system are defined providing new possibilities in the system functionality. Before proceeding to the functional requirements of the protection system a generic set of different types of basic protection zones is introduced. These protection zone types are further applied when analysing and discussing the required functionalities. PRESENT PROTECTION PRACTICES IN FINLAND In this paper the Smart Grid requirements for the protection system are reviewed from the point of view of typical electricity distribution system in Finland. The Smart Grid technologies cover also the transmission and sub-transmission systems, but these are omitted here because the major changes will probably take place at the distribution system level. The distribution systems vary from country to country but the Finnish system is rather similar to the systems in many other European countries. Still there are some aspects that can be particularly found only in Finnish system or at least only in the systems used in the Nordic countries. Although the focus is in Finnish system, this paper tries to present globally valid issues in addition to those that are more system specific.