Design of Protection system based on post fault conditions obtained using symmetrical components method.

Modern power systems operate close to their security limits and require highspeed
fault clearing to preserve transient stability, reduce fault damage, minimize
outage duration, and improve power quality. To provide high speed tripping for faults
occurring at any point on a transmission line, there must be some form of accurate
protective relays which operate on the basis of post fault values.
Power systems are subjected to a wide range of small or larger disturbances
during operating conditions. Small changes in loading conditions occur continually.
The power system must adjust o these changing conditions and continue to operate
satisfactorily and within the desired bounds of voltage and frequency. The power
system should be designed to survive larger types of disturbances, such as faults,
loss of a large generator, or line switching. Certain system disturbances may cause
loss of synchronism between a generator and the rest of the utility system, or
between interconnected power systems of neighboring utilities. If such a loss of
synchronism occurs, it is imperative that the generator or system areas operating
asynchronously are separated immediately to avoid widespread outages and
equipment damage
A false trip of a distribution bus can cause outages to a large number of
customers as numerous feeders and/or sub transmission lines may get
disconnected. A false trip of a transmission bus bar may drastically change system
topology and jeopardize power system stability. Hence, the requirement of a
maximum security of busbar protection. On the other hand, bus faults generate large
fault currents. If not cleared promptly, they endanger the entire substation due to
both dynamic forces and thermal effects. Hence, the requirement of high-speed
operation of busbar protection.
In this project per we describe the philosophy and design fundamentals of
protection in a transmission system using the symmetrical component approach.

The symmetrical components method is a technique that allows unbalanced phase
quantities such as currents and voltages to be represented by balanced components.