الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Transmission line protection is an important protection area in power system.
Line protection system should be very secure, fast, dependable, sensitive and selective.
Several basic types of protection principles can be used for line protection relays such as
overcurrent, distance and differential protection. New Protection schemes of transmission
lines mainly concentrated on using current differential protection for handling many
problems of other relays such as power swing, high ground resistance, and multi-in feed,
besides impacts of open circuit of voltage transformer, parallel mutual inductance and
series compensated capacitors.
This thesis proposes adaptive methodology to improve sensitivity and speed of
the current differential protection scheme for transmission-lines without compromising
the system security by controlling the restrain region in the current differential plane. A
parallel overhead transmission lines with system voltage 220 KV model is the study
system used for applying the current differential protection schemes; conventional and
proposed. The PSCAD/EMTDC program is used for simulation and evaluation of the
performance of each scheme with different cases of fault types, fault locations, fault
resistances, fault inception angles and normal loading cases. Three current differential
protection schemes are studied: The percentage scheme, the current plane scheme and the
proposed smart differential scheme. Extensive simulation studies showed that the
proposed current differential protection scheme is secure, selective and more sensitive
and faster than other conventional schemes.