1. Using the above diagram calculate the following

  1. The voltage V₂
  2. The current I₂
  3. The current I₁

2. Using the diagram below

Work out the following:

1. The voltage V2
2. The impedance (The resultant resistance) of the circuit on the V2 side of the circuit
3. The current I2
4. The Average Power on the low winding side of the transformer kW
5. The reactive power kVAR
6. The effective power kVA
7. The power factor
8. The Current I1

Design an electrical system for an underground coal mine:

1. The mine is to operate a single retreating long wall coalface at any one time. Whilst this face (panel 1 on the figure) is in production the next panel is under development. The physical dimensions of each airway in the system are as listed in Table 1. All airways excepting the drift and shaft are developed fully within the flat coal seam of 3m thickness. A ventilation fan is located at the top of the return ventilation shaft that can in emergency situations act as a second means of egress.

2. Coal clearance is undertaken by conveyor, conveyors are located in airways 1-2, 2-5, 5-7, 5-6, 7-10, 10-11, 11-12, 12-13 and 7-14 with an armoured face conveyor located on ht face 6-8. Development is undertaken using continuous miner. Table 2 lists the electrical machine requirements and location for the time frame under consideration.

3. Distribution voltage at the mine is 13.2 kV.

4. The purpose of the exercise is to devise an electrical distribution system to service the current and possible future requirements of the mine. Consider the following:
- Cables and cable couplings
- Switchgear
- Transformers
- Power centres
- Distribution and utilisation systems
- Electrical safety
- Control requirements
- Any other requirements
- Power factor correction (if required)

5. All assumptions need to be detailed and justified. The results should be presented as a report; no page limit is specified, with diagrams and other data as required. Note that there is no single answer to this design, marking will be based on the robustness of the system, the inherent safety of the system and the ability of the system to be expanded. In order to aid on the last criterion it is expected that the life of an individual panel is of the order of 6 months under the current production schedule, the extracted length of all panels in the mine is 1950m, i.e. a 50 m barrier pillar is required.

Dimensions of mine:

Underground electrical equipment: