Standards Development

Scope

This part of IEC 60255 specifies the minimum requirements for functional and performance evaluation of an a.c. directional overcurrent protection (3.1.1) function. This document also defines how to document and publish performance test results.The directional overcurrent protection (3.1.1) function comprises an overcurrent element combined with a directional element. The directional element supervises the operation of the overcurrent element by enabling or blocking its operation based on the direction of the fault current. This document specifies the requirements that apply to the directional element, and refers to IEC 60255-151where relevant to the overcurrent element. This document defines factors that influence the accuracy and dynamic performance of the directional overcurrent protection (3.1.1) function. The test methods for verifying the declared performance are also included in this document.This document covers directional phase, positive-sequence, negative-sequence, zero-sequence(residual), and neutral overcurrent protection (3.1.12) functions, as listed in Table 1. Annex A provides commonly used operating characteristics of these functions.Table 1 – Directional overcurrent protection designationsProtection function IEEE/ANSI C37.2-2022 [1] Applicable Function Numbers IEC 61850-7-4:2010/AMD1:2020 Applicable Logical Nodes Directional phase overcurrent protection 67 PTOC a RDIR+PTOC a Directional positive-sequence overcurrent protection 67 Directional negative-sequence overcurrent protection 67 Directional zero-sequence overcurrent protection Directional residual overcurrent protection 67N PTOC a RDIR+PTOC a PSDE b Directional neutral overcurrent protection (3.1.12) 67G a The direction information of protection Logical Nodes can be available in Data Attribute 'dirGeneral' of its Data Object 'Str', 'Dir' or 'Op'. b The Logical Node PSDE can be used for directional earth fault protection in resonant earthed (neutral) system and isolated neutral system.Additional restraint or blocking elements may be part of the directional overcurrent protection (3.1.1) function. This document does not specify the functional description of these additional restraint or blocking elements.This document does not cover directional elements integrated into other protection functions, such as distance protection and power protection.The general requirements for measuring relays and protection equipment are defined in IEC 60255-1.