Improvements in dependability and usability for a substation automation system with redundancy

Substation Automation Systems (SAS) are widely used for the purpose of control, protection, monitoring, communication etc. in substations to improve the reliability of the power supply. SASs adopting IT based solutions such as Ethernet LAN have recently become more common although hardwired control has been used in the past in earlier versions of SAS utilising simple communication methods. Moreover, IEC 61850 which is the international standard for communications within substations has been published, and the application of SAS based on IEC 61850 is increasing. It is necessary to select each component and the configuration of the SAS from the viewpoint of dependability so that the dependability of the SAS, i.e. reliability, availability, and serviceability may have a very big impact in the stability of the power supply in the electric power transmission and distribution systems. In this paper, we will describe the configuration policy of an IEC 61850 based SAS, its actual system configuration and the redundant configuration to improve dependability. In addition, we will explain some of the new functions not currently covered by IEC 61850 that we have developed to improve usability and availability. Following which we will present an evaluation of the dependability for MTTF (Mean Time To Failure), Availability, and FMEA (Failure Mode and Effects Analysis) for these configurations of SAS based on the dependability requirements for SAS. Furthermore, other measures have been adopted in the design to ensure fail-safe and fool-proof operation and thus improve system dependability in a much wider sense.

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