Item:

• 11KV switchgear in a regional power distribution network
• 75,000+ items of plant
• 8 year “maintenance” cycle, costing approx. £1m per annum
• No method in place for predicting possible failures
• Difficult to incorporate into business planning

Objective:

• Optimisation of switchgear inspection and maintenance, to reduce costs and minimise engineering disruption

Approach:

• Analysis of failure incident reports by switch type, age, duty and failure mode – as data exist

Results:

• Quantification of failure rates and reliability measures, for switch types with sufficient populations, as a function of age
• Calculation of the effect on reliability of varying the maintenance interval
• Calculation of the effect on reliability of different sampling levels for inspection, recognising that intrusive inspection can initiate problems
• Insufficient data to identify any effects of duty or environment

Benefits:

• Specification of initial inspection and maintenance plans, with rules for their continued optimisation as results are accrued
• Considerable savings on inspection and maintenance costs
• Understanding and control of system reliability

Publication:

Brear, J.M., Dean, R.J., Johnson, T.D. and Jones, G.T.
“Increasing condition monitoring to reduce unplanned outages and equipment replacement”
ERA Conf ‘Engineering Asset Management for Utilities, Industry and Commerce’
London, October 1999