The rapid increase in electrical demand and supply reliability for both domestic and industrial use throughout the modern world provides a set of unique challenges for supply authorities. It is not only paramount that the ever increasing supply and reliability demands are met but also environmental and cost concerns are addressed.
It has been proven that single pole tripping and reclosure schemes implemented on EHV (Extra High Voltage) transmission lines greatly aid in both supply availability and reli- ability. However, it is obvious that such schemes will greatly increase the complexity to both the primary and secondary systems. Subsequently, it is clear that the behaviour of the primary network under single pole operation must be extensively modelled to enable adequate protection and control by secondary protection systems.
Throughout the following study a technique for determining the maximum fault duration on a transmission network that incorporates single pole tripping has been developed. Fur- ther to this, investigations into accurate modelling of the physical network particularly pertaining to the fault arc that will be seen inside an EHV circuit breaker when open- ing under faulted network conditions has been undertaken. These techniques have been utilised to produce a specific maximum fault duration of 57ms for an example case study; subsequent circuit breaker failure times were then developed for a number of protection devices
