Question

(a) State two disadvantages of Time Graded Protection Systems.

(b) State two advantages and a disadvantage of Differential Protection Systems.

(c) What is the preferred secondary current rating of a CT for a Differential Protection System? Why is this rating preferred?

(d) State the minimum time grading interval between two relays and give reasons for this interval.

(e) Complete the following:

1. Desired relay operating time = TMS × ....................

2. Saturation can be a feature of CTs and ....................

(f) State the two rules of successful time grading of relays.

Answer 1