A Synchronous Condenser is a device that control voltage on an electric utility’s transmission or distribution system. Voltage is the “pressure” needed to deliver electricity through such a system.
Another device that controls voltage is a capacitor. Capacitors have no moving parts. Their simple design keeps their cost and maintenance requirements low.
Synchronous Condensers have internal parts that spin a motor or generator. Their sophisticated design results in higher maintenance requirements and higher costs than those of capacitors.
This higher cost may be justified because Synchronous Condensers are more effective than capacitors at controlling and stabilizing voltage.
Synchronous Condensers are located in utility substations, inside buildings or protective enclosures. They tend to run for long periods, made significantly less noise than generators, and produce no smoke or emissions.
Synchronous Condensers do not make electric power like a generator, so they are not mechanically connected to a source of propulsion like an engine or water wheel
One type of Synchronous Condenser uses a special material in its windings (internal coil of wire). When are bathed in liquid nitrogen to cool them, they have no electrical resistance, a property know as super conduction. This lowers the already-minimal power requirements of the Synchronous Condensers, often making it even more cost effective than a conventional design, over the course of its life.