Until now, the visual representation on RMU’s regarding the status for a three (3) positioned switch (CLOSED – ISOLATED – EARTHED) for an operator was limited to a “front of panel MIMIC” and accepted by industry as common practice. This was due to there being no other technology available prior the POWINS MSS Ring Main Unit which now enables viewing of internal 12kV circuit switch contacts. The traditional MIMIC indication is still present and operational however is recognised as not providing a failsafe method of switch contact status due to its absolute reliance on intricate linkages that move MIMIC indication flags or rotate MIMIC knobs dressed with stickers or lines, to aid in representation.
Addressing safe operation and best practice, MIMIC utilisation only in Secondary RMU switchgear is a step back from what industry would like to see, which is visual confirmation of the actual switch and device 12kV rated internal contacts.