What is reliable smart grid?

Reliability has been the central issue for power system planning and operation in the past several decades. According to North American Electric Reliability Corporation (NERC), reliability is defined by resource adequacy and operational security. The former ensures an adequate level of resources to meet the projected load. Such level is often measured by the Loss of Load Expectation (LOLE) with the typical criterion of 1 day in 10 years. The latter secures the operability of the system taking into account contingencies. The security is often measured by the N-1 criterion, i.e., the system can maintain balance and stability with the loss of any single element. Reliability is maintained by the system operator at the same level for the entire system, and is treated as a public good. Such reliability concept was developed for a centralized system with a manageable level of uncertainty.