Feasibility Studies for New Mine Power Stations

Outline

PCE were engaged to assess the impacts of upgrading the power stations on two associated mine sites and interconnecting them with an overhead line. The aim was to identify if there were any major flaws in the proposed upgrade based on existing mine distribution and loads, and planned future loads.

Load Flow Studies

ETAP Load Flow Studies were carried out to establish generation capacity and spinning reserve required to run the mine sites and to start major loads such as the Ball Mills, Vent Fans and a future Mine Winder.

Redundancy of generation was also considered to plan for a generator failure.

Load ratings for proposed switchboards and inter-tie cable were established.

Black Start generation capacity was also established.

Harmonics Study

An ETAP Harmonic Study was carried out to establish indicative Harmonic levels on the new system emanating from existing mine VSD equipment.

Fault Level Study

An ETAP Fault Level Study to IEC60909 was carried out to establish the required fault rating of new switchboards and to identify if any existing mine equipment would be underrated. ETAP Equipment Evaluation module was used to evaluate equipment ratings in a structured way.

The existing mine 3.3kV and 11kV systems were Earth-Fault limited to 75A and 300A. The fault study was used to check compatibility with the proposed new generation and earthing transformers, and to check requirements for transitioning to the new system.

Stability Study

An ETAP Stability Study was carried out to check generation system stability in a number of motor starting and load rejection situations, and the suitability of the inter-tie cable to keep generation stations in synchronism.

Difficulties

Managing and assessment of data from numerous scenarios in all the studies was a challenge, as well as the modelling of generator AVR and Governor systems for the stability studies.