Reviewing essential DC supplies

An essential requirement at a modern substation is a highly-availability DC supply for protection and communications devices. This supply requires the ability to support critical services over lengthy periods during a failure of the local AC supply, supporting remote control and allowing rapid restoration of network services when ready.
Tesla was engaged by a client with a large number of substations to review their communications power supplies for compliance with their recently updated black start expectations. The review parameters also included how close the batteries were to end-of-life, and which models of charger were no longer supported. Seismic restraint design considerations to allow survivability of the DC supply system during earthquake events was assessed and reported on too.

The review was carried out by our Communications Team, as they have extensive experience preparing design and maintenance standards for communications DC supplies, and have developed in-house software tools for calculating battery and charger capacity requirements against types of comms equipment. This model is complex, calculating battery sizing, then assessing redundant elements such as battery strings and charger modules. The model also ensures required recharge times are met by the overall installation. Communications load has very different characteristics from that of protection and primary plant DC supply, so must be analysed separately from the main substation DC supply.

The review project covered a large number of stations, and has been spread over two years to allow the recommended upgrades to be slotted into business planning.
For further information on our engagements in this area, contact garry.rodgers@tesla.co.nz

48Volt batteries

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