Time-delay concept-based approach to maintenance scheduling of HV cables

Abstract

The associated daily maintenance effort and cost has been increasing with the growing use of high-voltage (HV) cable circuits. This study proposes a time-delay concept-based approach to maintenance scheduling of individual HV cable components, to allow periodicity of inspection to be optimised with consideration of time-delay interval between the instant of defect inception and final failure. Here, the progress from a defect to its resultant final failure can be represented as a two-stage process, one being a stochastic process of defect arrival and the other being a delay-time interval from defect to failure. Then an optimisation model is established to schedule maintenance activities based on the two statistical processes, where the objective function is set as the minimal maintenance cost. Cable circuits are divided into five components in accordance with the objects of inspection and testing. The components within different service ages are considered individually in the statistical models, and their accumulate failure numbers during each service year are used to automatically formulate and update periodicity of inspection. To illustrate the feasibility of the approach proposed, theoretical analysis on thousands of cable circuits are carried out. Results show that the economic expenditure could be reduced by 22.2% after optimisation.

Keywords

• optimisation
• stochastic processes
• scheduling
• inspection
• maintenance engineering
• delays
• time-delay concept-based approach
• maintenance scheduling
• hv cables
• associated daily maintenance effort
• high-voltage cable circuits
• individual hv cable components
• time-delay interval
• defect inception
• resultant final failure
• defect arrival
• delay-time interval
• maintenance activities
• minimal maintenance cost
• accumulate failure numbers