IEC 61557-7 Ed. 2.0 b:2007

This part of IEC 61557 specifies the requirements for measuring equipment applied to testing the phase sequence in three-phase distribution systems. Indication of the phase sequence may be mechanical, visual and/or audible. This part of IEC 61557 does not apply to ancillary measuring equipment for other quantities, for example voltage testers comprising an additional phase sequence indicator. It does not apply to monitoring relays. This second edition cancels and replaces the first edition published in 1997. This edition constitutes a minor revision.