IEC 60255-26:2013 is applicable to measuring relays and protection equipment, taking into account combinations of devices to form schemes for power system protection including the control, monitoring, communication and process interface equipment used with those systems. This standard specifies the requirements for electromagnetic compatibility for measuring relays and protection equipment. The requirements specified in this standard are applicable to measuring relays and protection equipment in a new condition and all tests specified are type tests only. This new edition includes the following significant technical changes with respect to the previous edition: - definition of test specifications, test procedures and acceptance criteria per phenomena and port under test in one document; - extension of radiated emission measurement for frequencies above 1 GHz; - limitation of radiated emission measurement at 3 m distance for small equipment only; - addition of zone A and zone B test level on surge test; - extension of tests on the auxiliary power supply port by a.c. and d.c. voltage dips, a.c. component in d.c. (ripple) and gradual shut-down/start-up; - harmonization of acceptance criteria for immunity tests.