Applied Electricity Paper 2 , Nov/Dec. 2011

Questions:		1	2	3	4	5	6		Main

General Comments
Weakness/Remedies
Strength

Question 3

State one difference between the voltages generated by a single-phase and a three-phase synchronous generator.
(b)     List four components of a high voltage overhead transmission system.
(c)     State one advantage each of overhead and underground transmission
          systems.

_____________________________________________________________________________________________________

Observation

The expected answers were:

Single-phase synchronous generator	Three-phase synchronous generator
Constant	Varies
230 V – series connection	Between 400 V and 230 V

Any four of the items listed below
Steel towers
Glass/porcelain insulators
Aluminium conductors
High voltage transformers

Overhead advantage	Underground advantage
Low investment costs Less expensive maintenance	Long life expectancy Reduced maintenance costs Service uninterrupted by storms Conserve valuable land Reduced fire-fighting hazards Prevention of accidents

The question was on Alternating Current Machines/Electrical Supply. It was unpopular with the candidates. The candidates that attempted the part (a) could not state the difference in the voltages generated by the two systems. They were not at home with the components of an overhead transmission system but rather stated overhead distribution system components.