CQUniversity Mackay City Fault Current Analysis

CQUniversity engaged BRS to complete a fault current calculation on Mackay City campus Building 1. The building was undergoing a renovation, with an imminent upgrade to the electrical LV distribution switchboards (and associated switch gear).

Building 1 had undergone minimal electrical upgrades over its’ many decades of use. Both the MIMS main riser cable, many of the switchboards and switch gear, were still original from when the building was constructed.


BRS Responsibilities

  • Electrical Engineering
As part of a broader building upgrade, the main floor distribution boards were being upgraded to modern standards along with modern switch gear. One issue with the existing hardware was that it was difficult to isolate a floor adequately to perform electrical work (such as installation of a new light) without having to isolate the entire building.

CQUniversity Mackay raised concerns that the new hardware would not be suitable to handle anticipated maximum fault current levels, given the existing Ergon transformer and rising mains cables. BRS attended site to take off details of the existing installation and discuss with CQUniversity staff what their intended new hardware was.

It is important to consider fault current levels when designing an electrical installation - it can be extremely dangerous under fault conditions if the distribution system is not setup or functioning correctly. One factor to consider is the "withstand rating" of a protection device; for instance, if a circuit breakers' withstand rating is less than the calculated fault current at that point on the system, the breaker could catastrophically fail and potentially destroy the asset.

To ensure the fault current levels and protection was safe and compliant, legislation & standards audited against included:
• QLD Electrical Safety Act 2002
• QLD Electrical Safety Regulation 2011
• AS/NZS 3000 Wiring Rules
• Distribution Network Standard for Electrical Design and Construction Requirements for Chamber Substation (Ergon Energy)

BRS used the Powerpac software package to model the new distribution system and calculate the fault current levels from the main incomer of the main switchboard to the top level of the building. BRS made recommendations to CQUniversity that included minimum fault level requirements and cascading requirements.

Thanks to the ongoing relationship with CQUniversity, BRS has since been engaged to complete more work across their nation-wide campuses.