No of disc required for 11 kV transmission line = 1 disc Since the transmission line is 3-phase, therefore, the number of discs required for a single-pole will be 3. Total no. of poles = 80 No of disc = 3 × 80 = 240
In the PMMC type instrument, the deflection is directly proportional to the current flowing through the instrument, we get a uniform scale for the instrument. It gives a uniform scale of upto 270° or more. Td ∝ I