Final answer:
The question pertains to the percentage change in secondary voltage when using a tap changer on a transformer. Steps such as 1.002 (0.2% increase) or 0.9980 (0.2% decrease) are typical adjustments for regulating voltage levels. Higher transmission voltages lead to lower losses and improved efficiency in power transmission systems.
Step-by-step explanation:
The question relates to the adjustment of voltage in electrical systems using a tap changer. When a tap raises or lowers the secondary voltage, it does so by a certain percentage to regulate the output voltage to a desired level. Typically, a transformer's tap can change the voltage in predefined steps, such as by 1.002, or a 0.2% increase, which would be 2.0 x 10-1 percent. Similarly, it could also result in a decrease by an equivalent percentage as represented by a value like 0.9980, or a 2.0 x 10-1 percent decrease. This regulation is crucial for maintaining appropriate power supply levels in electrical transmission systems. The efficiency of power transmission is significantly influenced by the voltage level: higher voltages result in lower currents and reduced power losses, which are expressed as a percentage. For instance, transmitting 100 MW at a high voltage, say 345 kV, would require less current than at 25 kV, resulting in lower losses. However, if the voltage were lower, more current would be needed, leading to greater losses, as indicated by the 16.0 MW loss. Therefore, the choice of voltage level is a balance between system efficiency and the practicality and cost of transmission equipment, like wires which could be made of larger, more expensive materials to reduce resistance or even use superconducting materials if economically viable to eliminate losses.