RTUs are going IP

Tesla has carried out a very large number of RTU replacements, but one recent project stands out for its size. The project involved one of Transpower’s large substations, at Whakamaru. At this site, the existing early 1990’s RTU was out of manufacturer’s support and relied on serial data connections to 24 protection and control devices plus connected to over 470 control and information points through hardwire closing contacts. The project included re-programming all existing protection devices to gather as many points as possible electronically, then installing 23 new Ethernet-connected I/O devices to collect the remaining hardware points.

A dual-redundant Ethernet-based gateway was installed as a Substation Management Unit (“SMS”), connected to a total of 81 substation IP devices. The SMS gateways then have redundant paths upwards through an IP based network to the Transpower’s National SCADA system.

The project included designing a technique for running the old and new RTU systems simultaneously and defining a plan for all the individual outages needed for all primary equipment to re-programme protection and recommission control and indication.

The commissioning process for this large project requires outages for many items of primary plant. As this station is a key point within the New Zealand National Grid, scheduling of these extends over a long period. The outages and staged commissioning is currently proceeding, without surprises and with no unplanned breaks in service.

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