1. (a) What is a Vector grouping?
(b) How does the knowledge of vector grouping assist in connecting transformers to operate in parallel?
(c) What additional information is needed to ensure that transformers are capable of parallel operation?
(d) What are the only phase displacements in degrees with which it i possible to parallel the secondaries of two transformers?
(e) Draw the phase relationships and connections for
(i) Dd0 connection
(ii) Yy6 connection.
2. (a) Name the types of on-load tap changer.
(b) Which is the most commonly used and why?
3. (a) What is the advantage of monitoring winding temperature as a method of overload protection?
(b)Name two other types of over current protection.4.
(a) What is a conservator?
(b) How does this device protect against pollution of the transformer oil?
5. List the symbols, and their meaning, used to classify the methods of cooling a transformer and state the types of cooling of an ONAF transformer.
