What defines a solidly grounded electrical system?

A solidly grounded electrical system is characterized by having no intentional impedance between the system's grounding connection and the earth. This means that the electrical system is directly connected to the ground without any resistive or reactive components that would limit the current flow. This type of grounding provides a very low impedance path for fault currents, which helps to ensure protection during fault conditions by allowing circuit breakers and protective devices to operate effectively and promptly.

When faults occur, such as a short circuit, the low impedance path ensures that sufficient current flows through the ground connection, allowing protective devices to trip quickly and minimize the risk of electrical shock and fire hazards. In essence, a solid grounding system is crucial for safety and reliability, enabling equipment to perform optimally while providing a clear path for fault currents to return to the ground.

The other options suggest different forms of connection or grounding that either involve some level of impedance or utilize different methods, such as transformers, which do not meet the criteria for a solid grounding system. Therefore, the definition of a solidly grounded electrical system is accurately encapsulated by having no intentional impedance between the earth connection and the system.