A novel unit protective relaying concept based on sequential overlapping derivative transform: Interconnected network application

In interconnected network, the fault at any section may appear as a forward or a backward at more than one relaying station. This may deceive any protection system especially those which use the current signal only. This paper presents a solution for such problem. The proposed protection is based on extracting the transient components, initiated by faults, using the fourth sequential overlapping derivative (SOD) concept. SOD is applied to both current and voltage signals at both protected line terminals. The multiplier of the produced transient components is used as a novel relaying signal. The polarity of the initial change of this relaying signal is depending on the fault direction. Exchanging data between relaying stations using a suitable communication channel enable us to discriminate between internal and external faults and send a tripping signal to the prober circuit breakers. Simulation tests are carried out using ATP program while the relaying concept is established by using MATLAB program. Extensive number of simulation cases, including fault type, fault resistance, fault inception time and load switching effects are presented. Results showed a high sensitivity for internal faults, and high security and stability for external faults. Moreover, no need for samples synchronization and current transformer saturation compensation.