NUMERICAL DIRECTIONAL OVERCURRENT PROTECTION FOR POWER DISTRIBUTION NETWORK

The studypropose the use of symmetrical-phase-sequence which combine both fault
direction and inverse time response characteristics of overcurrent protection in
determiningfault direction with high sensitivity in parallel transmission lines. Nondirectional
overcurrent protection systemsfail to discriminate thefault for the relay
co-ordination whenfault current canflows in eitherforward or reverse directions. In
the other hands, analogue overcurrent protection system has many weaknessessuch
as very low reliability, inaccurate, inconsistence, and slow response which can be
encountered by using digital technique. Meanwhilefor the single transmission lines
models, there are still severalflaws that can befound, like if a fault occurred in the
middle of transmission line and in the same time one of the generator facing a
problem, certain busbar that supplied to the load will lost itsfunction. The scheme
used is basedon the symmetrical-phase-sequence components which consist ofzerophase
sequence, positive-phase sequence, andnegative-phase sequence. Some studies
have been made to identify several types offaults related to the systems proposed.
Every protection systems have three basic components: instrument transformers,
relays and circuit breakers. Generally, the currents and voltages of eachphase are
convertedfrom analogue to digital signal by data acquisition system (DAS), which
located inside digital directional overcurrent relay. The concept to be employed to
perform digital directional overcurrent protection system is discussed in this report.
The future work to be done is to do simulation in order toprove that the algorithm
proposed is applicable to perform the digital directional overcurrent protection for
theparallel-line distribution network.