During a system restoration, col load pick up can involve inrush currents that are how large?

During system restoration in the context of electric power systems, the phenomenon of cold load pickup refers to the process where a significant portion of the load is reconnected to the electrical grid after being disconnected during an outage. When this occurs, the inrush currents can indeed reach impressive magnitudes, as electrical devices such as motors and transformers draw higher initial currents when they are energized from a standstill condition.

The correct understanding is that inrush currents during such restorations can reach levels that are up to 10 times greater than the normal load currents. This increase is primarily due to the electrical characteristics of inductive loads, which can present a higher demand when the supply is first restored. Specifically, motors can experience inrush currents that, upon starting, can exceed their rated operational current significantly due to their inability to establish a steady-state condition immediately.

This characteristic of inrush currents is critical for system operators and engineers to consider during restoration planning and execution, as it impacts the stability and safety of the electrical system. It is essential to ensure that protections and system configurations account for this surge in demand to prevent equipment damage and maintain reliable service.