Reliability Assessment as Basis for New Transformer Substation Concepts

The presented study compares the reliability of typical configurations of transformer substations (S/S) for sub-transmission networks (72.5 - 170 kV) based on comprehensive probabilistic reliability calculations. The motivation for the study was to reduce the large variety of configurations of sub-transmission transformer S/S by defining typical functional requirements and by finding configurations, which fulfil these functional requirements at an economical and technical optimum. The outcome of this study was used for defining basic configurations within ABB's new transformer S/S concept. Within this contribution especially the results for gas-insulated (GIS) HV-switchgear will be discussed. The considered transformer SIS are connected to the sub-transmission network via one or two circuits They fulfil mainly local supply functions. They serve as in-feed to the distribution level and have typically one or two HV/MV transformers with rated power from 10 MVA up to 80 MVA. Depending on their network connection transformer S/S provide only a supply function (single-circuit and double-circuit radial connection) or a supply- and a transfer-function (loop connection). The transformer S/S (un) reliability is quantified by the interruption frequency and the unavailability of these functions. As a conclusion from the reliability assessment three transformer S/S configurations H1, H3L and P4 are recommended for standardized GIS transformer S/S.

Keywords:

Substation Concepts , Probabilistic Reliability , Transmission/Supply Functionality