FIGURE 4.1 below is a block diagram of the national grid - NSC Electrical Technology Power Systems - Question 4 - 2021 - Paper 1

The voltage waveforms can be drawn as follows:

1. Three sinusoidal waveforms with equal amplitude and a phase difference of 120° between each.
2. The waveforms will be placed on the same time axis, showing the peaks and zero crossings distinctly.

Transformer 1 is a step-up transformer because it increases the voltage received from the generation process to a higher level for transmission. This is done to reduce current flow in the lines, thereby minimizing I²R losses during transmission.

The type of connection used is a star connection. This configuration allows for both three-phase and single-phase equipment to be served, making it versatile for varying load types.

The phase current can be calculated using the formula: $I_{ph} = \frac{I_L}{\sqrt{3}} \Rightarrow \frac{15}{\sqrt{3}} \approx 8.66 A$

The apparent power (S) can be calculated using: $S = \sqrt{3} \times V_L \times I_L \Rightarrow \sqrt{3} \times 380 \times 15 \approx 9872.69 VA \approx 9.87 kVA$

The phase angle (θ) can be calculated using: $\theta = \cos^{-1}(0.9) \approx 25.84^{\circ}$

The reactive power (Q) is calculated using: $Q = \sqrt{3} \times V_L \times I_L \times \sin\theta \Rightarrow \sqrt{3} \times 380 \times 15 \times \sin(25.84^{\circ}) \approx 4.3 kVA$

1. Reduced current drawn from the supply, leading to lower electricity bills.
2. Increased lifespan and reduced maintenance of equipment due to lower heat generation.

The meter shows a lagging power factor.

The connected load is predominantly inductive, which results in a lagging power factor.

By connecting capacitors in parallel with the load or using synchronous motors, we can improve the power factor and bring the meter reading closer to unity.

The total power of the load can be calculated as: $P_t = P_1 + P_2 = 250 W + 460 W = 710 W$

1. Power factor.
2. Phase angle.

The two-wattmeter method is simpler and easier to connect to the lines, and it is also a more economical method of load measurement.