2.1 State THREE advantages of a three-phase distribution system over a single-phase distribution system - NSC Electrical Technology Power Systems - Question 2 - 2017 - Paper 1

The diagram consists of three sinusoidal voltage waves that are phase-shifted by 120 degrees from each other. Label the lines corresponding to the phases (R, Y, B) and reference the line voltages (+Vm and -Vm) as well as the zero voltage line. Ensure to indicate the phase angles clearly.

One disadvantage of the two-wattmeter method is that its accuracy can reduce significantly if the power factor is either leading or lagging. This can lead to incorrect readings of power consumption.

To find the line voltage ( $V_L$), use the formula:

V_L = rac{S}{rac{ ext{√3}}{3} imes I_L} Substituting the values:

V_L = rac{25 imes 10^3}{rac{ ext{√3}}{3} imes 38} = 379.84 V

To calculate the phase voltage ( $V_{PH}$), use the formula:

V_{PH} = rac{V_L}{ ext{√3}} Substituting the line voltage:

V_{PH} = rac{379.84}{ ext{√3}} = 219.31 V

To calculate the impedance per phase ( $Z_{PH}$), use the formula:

Z_{PH} = rac{V_{PH}}{I_{PH}} Substituting values:

Z_{PH} = rac{219.31}{38} = 5.77 ext{ Ω}

Improving power factor can help Eskom reduce energy wastage, resulting in more efficient energy distribution. This means that more power will be available for consumers and could potentially decrease the generation costs, as better power factor reduces the burden on the generation capacity.