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INVESTIGATION INTO THE DESIGN OF A 6600V LONGWALL MINING SYSTEM

INVESTIGATION INTO THE DESIGN OF A 6600V LONGWALL MINING SYSTEM. Presented by Adrian Trevor. Overview. What is a Longwall? Why bother moving to 6600V? Predicted Future Power Requirements Cable size selection Power flow modeling of proposed system Future work. Overview.

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INVESTIGATION INTO THE DESIGN OF A 6600V LONGWALL MINING SYSTEM

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  1. INVESTIGATION INTO THE DESIGN OF A 6600V LONGWALL MINING SYSTEM Presented by Adrian Trevor

  2. Overview • What is a Longwall? • Why bother moving to 6600V? • Predicted Future Power Requirements • Cable size selection • Power flow modeling of proposed system • Future work

  3. Overview • Used because of efficiency ( Cutting and recovery rates) • Continuous process once started

  4. Electrical Overview • All Drives at 3300V • Shearer > 2MW • AFC (Armoured Face Conveyor) 2.55MW • BSL (Beam Stage Loader) 300kW • Crusher 300kW • Hydraulic Pumps 600kW • Shearer Water Pump 200kW

  5. Why 6600V? • Ultimate reason is to improve torque for motors • Also allows increase in installed power without extremely large cable sizes • Allows longer monorail hence less flits

  6. The torque of a motor is proportional to the voltage squared. At 3300V, ↑ currents are drawn which causes voltage drops in all supply cables At 6600V, ↓ currents, and any voltage drop is a ↓ % of rated voltage Ideally in new system we want torque to remain above 90% at all times. Motor Torque

  7. Increased Power • An increase in voltage allows power increases to be obtained without increases in conductor sizes • E.g Type 240.3 cable with 50sq mm conductor can carry 170A which at 3300V is approx 970kW compared to 1940kW at 6600V • However physical dimensions and mass of cable ↑ marginally due to extra insulation required • In most cases cable sizes will be reduced

  8. Longer Monorail • ↑ Voltage allows potential length of monorail to be increased by ↓ voltage drop • If monorail length is doubled this has the potential of reducing monorail flits from approx 8 per block to 4 • Each flit takes approx 8 hrs • 8hrs production = 14000 tonnes x 4 flits = 56000 tonnes • 56000 tonnes x $40 = $2.24 million!! per block

  9. Work Completed • Predicted future power requirements • Cable sizing calculations • Power flow study

  10. Future Power • Future power requirements can not simply be increased linearly. i.e. increase all items by 10% • Each piece of machinery requires it’s operation to be analysed to determine what, if any power increases are required. • Shearer • Increase in cutter motors to 1000kW each • Increase in traction motors to 165kW each • Total installed shearer power of 2.4MW

  11. Future Power • AFC • Considering increase in face width to 400m from 265m • Increase in power to 4 x 1000kW motors (2@tg,2@mg) • BSL • Increase in power to 2 x 300kW motors • Crusher • Increase in power to 1 x 300kW motor • Hyd Pumps and Shearer Water Pump • Increase hydraulic pumps to a total of 1000kW (Fat Face) • Determined that current SWP is suitable

  12. Future Power • This will result in a total installed power of 8.6MW, which is an ↑ of approx 50% on present

  13. Cable Selection • Cable selection is dependant on 2 main conditions • Current carrying capacity • Voltage drop • Current carrying capacity relates to the thermal limit of the cable • Heating effect of current in a cable (I2R losses) • Ability of insulation to dissipate this heat • Voltage drop is dependant on cable size, length and current • Must remain below 5% to keep torque above 90%

  14. Current Carrying Capacity • The heating effect on a cable occurs over a continuous time, and instantaneous values are not of a large concern. • FLC of motors NOT used to determine this. • Future average currents are used by projecting present averages to future Voltage and Power levels. • Present averages determined via Scada over a fixed period of time.

  15. Cable Selection • Example of Scada Data for TG AFC Motor with calculated average.

  16. Voltage Drop • Most important at motor startup • Full Operational Load (FOL) currents were determined by using the future FLC of the motor and allocating each motor a load factor. PF=0.85% and n=0.9% • Voltage drop calcs performed using FOL in that cable plus the starting current (6xFLC) of the largest motor.

  17. Cable Selection • Main Limiting factor was the voltage drop, most cables are significantly overrated in current carrying capacity to achieve acceptable voltage drop levels.

  18. Load Flow Simulation • A load flow simulation was completed at future levels using “EasyPower” simulation software. • Results confirmed calculated values • 3 scenarios were simulated • Full operational load • Full operational load with TG AFC Motor starting • Full operational load with 1 Shearer Cutter Motor starting

  19. Load Flow Simulation

  20. Future Work • Investigate issues that DMR has • Presently CMRA prohibits voltages >4kV • Investigate availability of equipment e.g motors, plugs, cables switching gear etc • Also sizing due to ↑ creepage and clearance values • Investigate issues with fault current energy, in relation to flame proof enclosures. • Investigate effects of EMI on control systems • Clearances inside enclosures • Effect on pilot core communication systems

  21. Questions??

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