Which of the following is NOT a main component of a switchgear assembly?

The correct choice identifies transformers as not being a main component of a switchgear assembly. Switchgear primarily consists of components used for controlling, protecting, and isolating electrical equipment in power systems.

Circuit breakers are essential for interrupting fault currents and protecting the system from overloads. Busbars play a critical role in distributing electrical power within the switchgear, providing a common connection point for different circuits and facilitating the transfer of electricity. Isolators are vital for ensuring safety during maintenance by physically disconnecting sections of electrical networks.

While transformers are crucial in electrical distribution and power transfer, they do not form part of the switchgear assembly itself. Instead, they are separate equipment used to change voltage levels for transmission and distribution. Their function is more aligned with energy transformation rather than the protection and switching roles that define switchgear components.