Definition
An electrical system arrangement in which two or more power sources, such as generators or alternators, are connected to a common bus and share the electrical load simultaneously. Each source must be matched in voltage (and, for AC systems, also in frequency and phase) before being brought online so that they contribute proportionally to the total load.
Plain English
Two or more generators feeding the same electrical system at the same time, sharing the workload between them.
Context Anchor
Seen in aircraft electrical system discussions, especially on airplanes with more than one generator or alternator.
Derivation
From Latin parallelus, meaning 'side by side.' In electrical use, it describes sources running side by side into the same bus, as opposed to running independently or in series.
Why Pilots Care
Provides enough power for all systems and keeps electricity flowing if one generator fails.
Analogy
It is like two people carrying one heavy bag together. The job is shared, but only if both people are connected to the same load and carrying their part correctly.
Intuition Check
Parallel operation does not just mean two things are near each other or running at the same time. In this context, it means electrical power sources are connected together and sharing the airplane’s electrical demand.
Example Sentence 1
The twin's two alternators are designed for parallel operation, so each one carries roughly half the electrical load in normal flight.
Example Sentence 2
During the electrical system check the mechanic verified that the two alternators entered parallel operation without voltage spikes.