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De-energised maintenance works

The Metropolitan TEGG service department provides a highly-efficient de-energised maintenance service for multiple clients. The purpose of de-energised maintenance is to isolate, service and inspect the critical components within an electrical system to prevent potential critical failures and to preserve equipment lifespan. This is followed by a condition assessment report: allowing the client to understand practical equipment maintenance and the necessary measures needed to ensure functional longevity.

The Metropolitan TEGG service department recently developed a yearlong de-energised maintenance program for a long-standing client at a large data centre. The program required the isolation, service and inspection of six major switchboards that supplied the facility. The time allowed for each switchboard was a weekend period per switchboard. The following is a description of its successful implementation and the challenges faced along the way.

The Metropolitan Solution

A plan was put in place to perform the shutdowns over six separate weekends throughout the year. The de-energised works completed on each of the switchboard’s were:

  • Circuit breaker maintenance
  • Busbar maintenance
  • Visual inspection and clean
  • Earthing system survey
  • Fixed-wire testing on the final sub circuits

Metropolitan TEGG technical staff oversaw the whole operation of the de-energised works and carried out:

  • The torqueing and micro-Ohm testing of each busbar connection
  • A visual inspection and clean for each switchboard panel using free cloths and a vacuum cleaner
  • Earthing system surveys for each switchboard

Specialised sub-contractors were employed by Metropolitan TEGG to help carry out the rest of scheduled works. This included:

  • Circuit breaker maintenance: relay functionality tests, insulation resistance, micro-Ohm tests on the circuit breakers and the fixed-wire testing on the final sub circuits.


During the shutdown, various switchboard problems were found and quickly brought to the client’s attention. We provided immediate and long-term solutions for each issue:

  • Contact deterioration in some of the ACB’s: this will be monitored during subsequent shutdown works
  • Loose bolts on the busbar connections: these were torqued to manufacturers specifications and connections were integrity-tested using a micro-Ohm meter
  • Cables being supported by conductible materials: replaced with non-conductible cable supports
  • Missing main neutral earth links: the client was advised to install missing neutral earth links at the earliest convenience

The Metropolitan TEGG service department consequently developed a comprehensive plan for continued de-energised, and indeed energised maintenance, over the next five years with this client. This will not only ensure equipment longevity, but will also help to eliminate downtime from equipment failure in a mission critical environment.