Section 13(1)(d) in The Assam State Electricity Board Engineering Service Regulations, 1973
(d)Period of probation may be extended by the Board for such period as it may deem fit in the case of a member whose (i) work and/or conduct has, in the opinion of the Board, not been satisfactory and/or (ii) who has not been able to pass the departmental examinations as may be prescribed by the Board: Provided that the total period of probation including extension, if any, shall not exceed 5 years in any case.