What is BS EN 60255-121 - Functional requirements for distance protection about?
BS EN 60255-121 is a British standard as a part of IEC 60255 series that specifies minimum requirements for functional and performance evaluation of distance protection function typically used in, but not limited to, line applications for effectively earthed, three-phase power systems. BS EN 60255-121 also defines how to document and publish performance tests. BS EN 60255-121 covers a distance protection function whose operating characteristics can be defined on an impedance plane and includes specification of the protection function, measurement characteristics, phase selection, directionality, and starting and time delay characteristics.
The test methodologies for verifying performance characteristics and accuracy are included in BS EN 60255-121. BS EN 60255-121 defines the influencing factors that affect the accuracy under steady state conditions and performance characteristics during dynamic conditions. BS EN 60255-121 also includes the instrument transformer requirements for the protection function. BS EN 60255-121 does not specify the functional description of additional features often associated with digital distance relays such as power swing blocking (PSB), out of step tripping (OST), voltage transformer (VT) supervision, switch onto fault (SOTF), trip on reclose (TOR), the logic for cross country faults in not effectively earthed networks, and trip conversion logic. Only their influence on the distance protection function is covered in BS EN 60255-121. The protection of series-compensated lines is beyond the scope of BS EN 60255-121.
Who is BS EN 60255-121 - Functional requirements for distance protection for?
BS EN 60255-121 on functional requirements for distance protection is useful for:
- The electrical industry
- The manufacturing industry
- Electrical equipment manufacturers
- Quality control personnel
- The health and safety department
Why should you use BS EN 60255-121 - Functional requirements for distance protection?
Distance Protection is a non-unit protection system that compares the Impedance between the Relay Location and the point where the fault occurs to the Set Value. The Relay runs and isolates the faulty section if the measured impedance is less than the Set Value. The main advantage of distance protection is that it virtually eliminates source impedance changes in fault coverage of the protected circuit.
BS EN 60255-121 provides you with guidelines for performance specifications, functional tests, and documentation requirements. Using BS EN 60255-121 guidelines ensures electrical safety, and accuracy in measuring relays and prevents leakage paths and other hazards.