Facility Connection RequirementsMay 1, 2005
independent high-speed protection systems may be required for bus protection if backup clearing results in instability.
I. O. Protective Relaying
Utility grade, transmission level protective relays and fault clearing systems are to be provided on the interconnected power system. All protective relays should meet or exceed ANSI/IEEE Standard C37.90 and NPCC document A-5. Adjoining power systems may share a common zone of protection between two parties. Compatible relaying equipment must be used on each side of the point of ownership within a given zone of protection. The design must provide coordination for speed and sensitivity in order to maintain power system security and reliability.
All bulk transmission power systems are to have primary protective relaying that operates with no intentional time delay for 100% of the specified zone of coverage. On transmission circuits, this is accomplished through the use of a communication channel. A second high-speed protection system may be required on a line or bus.
Backup protective systems should provide additional coverage for breaker and relay failure outside the primary zone. Specific breaker failure protection schemes must always be applied at the bulk transmission level. Specific relay failure backup must also be provided. Backup systems should operate for failures on either side of an interconnection point. Time and sensitivity coordination must be maintained to prevent misoperations.
A power source for tripping and control must be provided at substations by a DC storage battery. The battery is to be sized with enough capacity to operate all tripping devices after eight hours without a charger. An undervoltage alarm must be provided for remote monitoring by the facilities owners who shall take immediate action to restore power to the protective equipment.
Mechanical and electrical logic and interlocking mechanisms are required between interconnected facilities to ensure safe and reliable operation. These include, but are not limited to, breaker and switch auxiliary contacts, undervoltage and synch-check relays, and physical locking devices.
A transfer trip is required for many installations. It is used for backup protection and islanding schemes. Fiber optics is the preferred means of communication. Power line carrier or microwave is also used. Audio tone over phone line is the least preferred method because it may not meet requirements for speed and reliability.
Entities connecting to the FPL-NED transmission system shall investigate and keep a log of all protective relay actions and misoperations as required by NPCC document B-21 required by the NRC, NERC Standards, and ISO-NE.
Entities connecting to the FPL-NED transmission system must have a maintenance program for their protection systems in accordance with NPCC document A-4. Documentation of the protection maintenance program shall be supplied to FPL-NED ISO-NE, NRC, NPCC