IEEE Std 1547.6-2011 pdf download – IEEE Recommended Practice for Interconnecting Distributed Resources with Electric Power Systems Distribution Secondary Networks.
3. Definitions, acronyms, and abbreviations 3.1 Definitions For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary: Glossary of Terms & Definitions should be consulted for terms not defined in this clause. 4 cable limiter: See: network limiter. contingency (contingencies): The number of coincidental distribution system equipment outages (e.g., feeders) that can be tolerated without adversely affecting the character of customer service. Distribution systems can be categorized with respect to the allowable contingencies accommodated while still supplying customer load reliably. For instance, a radial distribution system is identified as a zero-contingency design because the loss of the primary feeder would result in a customer outage and thus seriously affect associated customers. Some area networks are designed and operated to a second-contingency criteria, and in these distribution systems, two primary feeders can be out of service without affecting customer service. cycling: Undesirable repetitive tripping and closing of a network protector (NP) because of variations in loading and other conditions. distribution secondary network: An ac distribution system where the secondaries of the distribution transformers are connected to a common network for supplying electricity directly to consumers. There are two types of secondary networks: grid networks (also referred to as area networks or street networks) and spot networks. Syn: secondary network. dynamically controlled inverter (DCI): An inverter with the capability to govern its power output based on an input control signal.
network protector (NP): An assembly composed of a circuit breaker and its complete control equipment for automatically disconnecting a transformer from a secondary network in response to predetermined electrical conditions on the primary feeder or transformer and for connecting a transformer to a secondary network through manual or automatic control responsive to predetermined electrical conditions on the feeder and the secondary network. The NP is usually arranged to automatically connect its associated transformer to the network when conditions are such that the transformer, when connected, will supply power to the network and to automatically disconnect the transformer from the network when power flows from the network to the transformer. network system: A collection of spot networks, secondary grid networks, or combinations of such networks and the primary feeders that supply them. network system reliability: A measure of the degree of certainty that the network system will perform its required functions under stated conditions for a stated time. Typical indices used to measure the reliability of a network system include the number of service interruptions (i.e., a complete loss of voltage), the frequency of service interruptions, and the duration of interruptions.