Riding through the additional load

– An SPS Story

Our client’s substation has two transformers that are loaded close to their n-1 load limit, however an industrial customer was planning to connect a large load that exceeds this limit.

The obvious solution of installing new transformers with higher ratings has a very high cost and long lead-time.

Tesla was engaged to carry out a detailed investigation, then design a Special Protection Scheme (SPS) that uses smart features of modern devices to allow the large load to be carried when both transformers are in service. The scheme provides automatic overload protection for the transformers through a feeder load shedding scheme involving communication between transformer and feeder protection.

The SPS design was encompassed within a scheduled transformer protection replacement project, and aligned with an RTU replacement, further widening the scope of the design works. 

The new scheme was comprehensively tested in a simulation facility to prove all the required scenarios were covered, and that safe operation was maintained through any failure mode of the equipment. 

The scheme passed its simulation tests, and was installed successfully. This has deferred significant immediate expenditure, and allows our client’s customer time to consider possible other ways to manage the load increase in this area.

Tesla’s project team was lead by David Collins, with Maik Ufferhardt and Bevan Cooper.  For further information contact David at david.collins@tesla.co.nz

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