Powergrid Corporation of India Limited
Online published on 19 August, 2015.
In the modern EHV Transmission network, system availability and reliability of each element is of utmost importance. In order to minimize outages due to equipment failures, modern Condition Based Maintenance Techniques are designed to predict deterioration of various components of Equipment in service.
Based on early warning, preventive and corrective actions can be initiated before any mal-operation/failures. Results of condition monitoring techniques need to be compared with pre-dispatch factory and pre-commissioning test results for proper trend analysis. In this paper, experience of POWERGRID on implementation of Dynamic Contact Resistance Measurement (DCRM) for condition monitoring of 765 kV Circuit Breakers is discussed in detail. There are two different case studies. In one case study, one double interrupter unit of 765 kV Circuit Breaker was taken up for internal inspection at manufacturers works on account of deviation observed in Dynamic Contact Resistance signature performed at site as a pre commissioning check. Problem was found in moving contact assembly during internal inspection & testingat manufacturer works, thus proving the effectiveness of DCRM technique. In another case study, DCRM of 765 kV CB interrupter units indicatedsignificant change with respect to DCRM carried outat pre-commissioning stage. In this case one pole of CB failed during service and DCRM was measured in other two phases to ascertain any problem in the remaining phases.
