TABLE OF CONTENTS It is not the purpose of this chapter to discuss purposes, objectives and types of embedded generation (this is discussed in Chapter 1). However, it is pertinent to reflect on these issues in respect of their impact on reliability, its evaluation and the models used. The installation of relatively small-scale generation, including non-utility sources, within a distribution network imposes additional modelling requirements. In fact the distribution network, historically mainly a supplier of energy received from bulk supply points, is becoming a mini-composite system having characteristics previously associated only with HLII.
The sources of generation considered in this book are generally small scale and therefore it is technically inappropriate for them to be connected directly to the grid or transmission system. Instead they are generally connected to the distribution network with all the consequential technical problems that ensue. These are particularly the weak nature of the network in which they are embedded, and the fact that they exist much closer to actual consumers than large-scale global generation. All the reliability models and evaluation techniques must reflect this connection situation.
Furthermore, because these sources are dispersed around a weak network, they can frequently become disconnected from BSPs but still be connected to consumers. This leads to the question of whether they can be allowed to continue supplying load (much more preferable from a reliability point of view) or whether they must be tripped (preferable from a safety point of view). Both...
