Generator Basics: Running in Parallel

Running in Parallel: The Basics

Reliability, Flexibility, and Expandability

Designing a backup power system for your facility can often be more complicated than simply choosing one large generator to serve all of your needs. Many times the paralleling of two or more small generators can offer much more flexibility and reliability than traditional single generator systems. A major benefit is Redundancy. If one unit fails in an emergency, the parallel unit instantly picks up where its partner faltered, ensuring uninterrupted power in critical situations. Parallel operating systems allow you to add or remove units from your system as your power needs fluctuate, with smaller units placed strategically around the facility instead of one mega site dedicated to a large generator and its associated switches. Varying power demands can also place a single large generator in a state of “under loading” (running at less than 30% capacity) which can cause several problems including overheating and wet-stacking.

Phase Number, Rotation, and Frequency

Paralleling two or more generators is expensive and very complex. To limit these added difficulties, professionals recommend that generators of similar make and rating be used and that you use the services of a qualified electrical professional.  Several factors have to match for paralleling to work, including the Phase Number and Rotation, which when matched avoid power surges and electro-mechanical stress. The generators Frequency ratings need to match exactly, as well (60 Hz in the US). The major advancements in digital control panel monitoring systems made recently allow for the exact synchronization of your system’s performance, with dedicated “paralleling switchgear” now available to check the several microcontrollers installed in the multiple generator systems.  Engine speed control, voltage regulation and load balance all need close monitoring to prevent damage to the system and failure.

There are many reasons to run generators in parallel; whether it is to seamlessly replace an old unit with a new without loss of power, or running parallel to the utility power source to feed surplus power back to the grid. Whatever the case is, the decision to build a multi-unit system running in parallel is best made after taking into consideration all of these factors and more.

How Can Woodstock Power Company Help?

We have many years in the generator business and have built relationships with professional electricians everywhere. We can guide you in making the best decisions in designing your backup power system. If you have any questions regarding generators or parallel operating systems, please give us a call.