Occurrence of cable fault can not be avoided due to many factors. Long outage of a cable from service results in heavy loss of revenue to the power distribution company, production loss to industries as well as unpleasant condition to general public. This requires an efficient instrument capable of locating the fault in minimum possible time and restoring the supply. SWT 4 is a powerful instrument to pre-locate the fault distance and exactly locate the fault point in a short time. It offers 500J or 1000J energy on 2 and 4 KV ranges that allows its use on LT networks effectively.