The distance relay has come into wide use in the protection of long transmission linea because it offers good selectivity without the need for a pilot channel, yet can offer a high speed of operation. By its very nature it is often difficult for a student of protection to obtain a good understanding of the operation and characteristics of a distance relay.
This project develops an experiment for power students which deals with the basic operation of a distance relay, so that this understanding may be more readily obtained.
Only the essential theory relevant to this experiment is presented, as there are many good references already available on this subject.
The construction of the relay built for this experiment is dealt with, and important leatures of the design mentioned, such as the design of the summing transformers, rectifier bridge phase and amplitude comparators, and level detecting circuitry.
Finally a discussion of the goals, practical details, and procedure of the experiment is included, and limitations and fields of error mentioned.