Wide-area synchronous grid

An interconnected electricity network spanning a large region in which alternating-current generators operate in synchronism at a common frequency. Its connected machines share electrical disturbances across the network.

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Synchronous generator: An alternating-current generator whose rotor turns in step with the frequency of the electrical system. Its rotating magnetic field sets the phase and frequency relationship that synchronizes grid generation.
Alternating current: Electric current that periodically reverses direction, typically following a sinusoidal waveform. Its repeating waveform provides the frequency and phase that interconnected generators share.
Asynchronous interconnection: A connection between power systems that exchange electricity without operating at a common alternating-current phase and frequency. Unlike a synchronous tie, it permits neighboring grids to maintain independent frequencies.
Interconnection: The linking of electricity networks so they can exchange power and operate as a larger system. A synchronous grid’s defining reach comes from electrically joining regional networks.
Electrical frequency: The number of cycles per second in an alternating-current waveform, measured in hertz. A shared frequency is the clearest system-wide indicator of balance between generation and demand.
Electric power transmission: The bulk transfer of electrical energy from generating stations to distribution networks over high-voltage lines. Transmission lines physically connect distant parts of a synchronous area.
High-voltage direct current: A technology that transmits electric power using direct current at high voltage, often between alternating-current systems. HVDC can transfer power across regions without requiring their generators to remain synchronized.
Ancillary services: Services that support reliable power-system operation beyond the delivery of electrical energy itself. Synchronized areas can coordinate reserves and frequency support across a broad region.
Power system inertia: The resistance of a power system’s rotating masses to changes in frequency. Synchronized rotating machines slow frequency changes after sudden generation or load losses.
Transmission line: A conductor or set of conductors designed to carry electric power between points in a network. Line impedance shapes how power and synchronizing forces flow between regions.