Divergent Engineering recently had a high-profile client finalising its mine operation expansion with the addition of a new ROM. The client is scheduled to construct the project onsite within this year, which will require the installation of two new substations - each includes 33kV switchgear, a 33/6.9 kV transformer, 6.6kV MCC, 6.6kV VSDs, 33/0.415kV transformer and 400V MCC together with HV and LV cables.
The overland conveyors were designed for future integration with the existing mine. Divergent Engineering was engaged to perform power system studies to validate the design and performance of the new overland conveyors and the current mine network so that any issues could be identified before construction begins. Divergent Engineering also prepared an HV submission to the Department of Mine & Petroleum and the network operator.
Divergent Engineering performed the following tasks:
Review HV and LV design to ensure the design complies with Australian Standards
Upgrade existing DigSILENT PowerFactory
Analyse operation scenarios
Perform Power System studies, including:
Load Flow
We considered twelve operational scenarios for the load flow studies. The results show that the new substations and the existing 33kV distribution network are adequate for all operating scenarios.
Short Circuit
We considered five operational scenarios for short circuit studies. The key outcomes were that the new equipment's short circuit could hold up for all fault levels.
Harmonic Study
We referred to the Horizon Power technical rule and AS/NZS61000 Standard to determine the acceptable limits for the new overland conveyors when analysing the mine’s network performance. We suggested using a harmonic filter when the analysis results do not meet the permissible limits.
Protection settings and coordination
We recommended the protection settings for all MCCs and switchgears. Fully overcurrent and earth fault grading are achieved with the recommended settings.
Arc flash hazard assessment and calculation
We referred to the IEEE 1584 – 2018 standard to calculate the incident energy levels and arc flash boundaries for system voltage less than 15kV; and the Lee method for system voltages above 15kV. 400V MCCs have achieved compliance with AS/NZS 3000 clause 2.5.5, Protection Against Switchboard Internal Arcing Fault Currents. The arc flash hazard incident energy levels are calculated for all MCCs and switchgears.
Earthing design review and earthing study
The earthing study for the ROM OLC substations found that the design, earth grid resistance, calculated earth potential rise, and step and touch voltages have achieved compliance with the relevant Australian standards and locate technical rules.
HV submission to the Department of Mines and network operator.
We considered all the design aspects, including transformers, generators, loads, lines and cables, to name a few. We compared the system configuration with the voltage variations and offered recommendations to mitigate the substations’ actual performance.
Our study confirmed that the proposed design of the ROM overland conveyor substations conforms to all relevant legislation, including:
Mine Safety and Inspection Act 1994
Mine Safety and Inspection Regulations 1995
WA Electrical Requirement 2015, Occupational Safety and Health Act 1984
AS 2067-2016 Substations and High Voltage installations exceeding 1kVac