Which of the following is not a definition of a power plant?

The definition of a power plant typically involves the generation of steam or other vapor at significant pressures or temperatures, which are utilized to produce power or energy. The core requirement for most power plants is that they operate at certain thresholds of pressure and temperature that allow for efficient energy production.

The option that states "Any one or more boilers in which steam or other vapour is generated at less than 57 kPa (8 psi)" is not aligned with the typical definitions used in the industry for power plants. Operating at such low pressures falls below the threshold generally associated with power generation. Power plants usually function at higher pressures to ensure that the steam produced is capable of driving turbines and generating electricity effectively.

In contrast, the other options describe conditions that do meet the fundamental requirements for power plants, such as operating at higher pressures or temperatures. These conditions facilitate the efficient conversion of thermal energy into mechanical energy, which is crucial for the operation of a power plant. Thus, option D stands out as the one that does not conform to the recognized definitions of a power plant.