UNE-EN IEC 60255-181:2019

This part of IEC 60255 specifies the minimum requirements for functional and performance evaluation of frequency protection. This standard also defines how to document and publish performance test results.

This standard covers the functions based on frequency measurement or rate of change of frequency measurements. The standard also covers frequency protection where additional blocking elements are used.

This standard defines the influencing factors that affect the accuracy under steady state conditions and performance characteristics during dynamic conditions. The test methodologies for verifying performance characteristics and accuracy are also included in this standard.

This functional standard is applicable to frequency functions embedded in a protection relay but also other physical devices which includes frequency protection in its functionality (for example, trip unit in a low voltage circuit breaker or inverters associated to photovoltaic or storage system).

This standard does not cover synchronizing or synchronism-check functions.

This standard does not specify the functional description of additional features often associated with frequency functions such as undervoltage blocking, df/dt or ”f/”t supervision, current supervision or power supervision (f/P function). Only their influence on the frequency protection function is covered in this standard.

Frequency and rate of change of frequency measurement outputs provided by protection devices are not in the scope of this standard.

Additionally, this standard does not explicitly cover the frequency relays based on current as the input energizing quantity but the principles covered by this standard may be extended to provide guidance for these applications.

The general requirements for measuring relays and protection equipment are defined in IEC 60255-1.