Instantaneous protection scheme for backup protection at high voltage transmission line

Abstract

The protection scheme in this research is the typical protection system at high voltage system; such as 132kV, 27SkV and SOOkV. This research will analyse the existing protection scheme for transmission line that the power utility has implemented, and will propose a new protection scheme to improve the performance of existing scheme. Currently, existing protection scheme that implemented by power utility for backup protection operation has a higher fault clearing time, no restoration time and did not utilize support relays. This research will focus on backup protection operation of high voltage overhead transmission line, which has taken up the communication as the main protection failed to communicate or the relay fail due to loss of DC supply or the relay function itself has blocked. Other than that, all support relays will be utilized in order to improve the protection system. The improvement will consider three elements, which are fault clearing time, fast restoration time and relay utilization. Each improvement will have its own philosophy and concrete reason, which will give advantages or disadvantages to the transmission line of protection system. The effect of improvement schemes will also consider the outcome on other schemes to ensure time coordination did not overlap. Every possibility of fault will be analysed in order to have a clear understanding on the effect of the three elements. CAPE software will be used as a tool for simulation and to analyse its compatibility with real application. CAPE software is able to model the practical transmission line as well as relay logic. It is also able to perform fault in the tested area. The result from simulation has shown that the backup protection operation for fault clearing time and restoration time has been improved. It also intensifies the network system stability particularly during the occurrence of the maximum fault current.