External diagnosis of Gas Circuit Breaker contact wearing
The internal inspection for a GCB (gas circuit breaker) is regularly performed to check and change contact parts in the case that the number of times of fault current breaking reaches a specified number, because TBM (time based maintenance) criteria is generally applied. Our new system, however, can change maintenance criteria to CBM (condition based maintenance). Current interval for internal inspection may be, however, redundant compared with the actual amount of contact wearing, because it is difficult to estimate the actual amount of contact wearing correctly from the outside. Then, in order to evaluate the precise amount of contact wearing from the outside, we developed a sophisticated system which can presume the accurate amount of contact wearing by using real breaking current and arcing time. Furthermore, this new system can evaluate the precise amount of contact wearing even if CT (current transformer) is saturated by DC in fault current and regardless of the current phase at the breaking. Therefore, the internal inspection period to replace contact materials can be extended up to nearly three-fold length compared with the traditional way.
SF6 gas circuit breakers reliability estimation, considering likely wear points
This paper presents an estimation of SF6 gas circuit breakers reliability in the transmission substations, considering the likely wear points identified in this device. The aging physically affects the equipment, which can make it less robust and more prone to failure. The equipment reliability can not be defined by its age, because its real condition depends on the wear and the on maintenance it may have been subjected. This paper identifies the wear points, which indicate the need for specific maintenance actions, and presents their specified limits for SF6 gas circuit breakers. The main contribution of this method is to enable an assessment of the actual condition of a circuit breaker, analyzing the measurements of its various wear points, which enables the identification of critical equipment that should be prioritized in planning maintenance. A circuit breaker failure may result in the unavailability of an entire power system, causing major disruption and severe financial losses. The maintenance based on the circuit breakers reliability, allows the minimization of failures, reduces the unavailability and increases the power systems robustness.
Reliability-centred maintenance
Introduction to Reliability-centred Maintenance Functions Functional Failures Failure Modes and effects Analysis Failure Consequences Proactive Maintenance 1: Preventive Tasks Proactive Maintenance 2: Predictive Tasks Default Actions 1: Failure-finding Other Default Actions The RCM Decision Diagram Implementing RCM Recommendations Actuarial Analysis and Failure Data Applying the RCM Process What RCM Achieves A Brief History of RCM.