Static Devices to Prevent Unnecessary Disconnections of Gas-Piston Units in Transients

This paper analyzes why relay protections (RP) disconnect generator sets (GS) at distributed generation (DG) facilities during transients, and what could such disconnection result in. Gas-piston unit (GPU) manufacturers configure the RPs in such a way that a short-term frequency deviation may cause an unnecessary disconnection. The worst scenario is when a microgrid that carries a DG facility becomes islanded with an active power imbalance, or when a microgrid is islanded while having to maintain an industrial load. How specifically a transient goes depends to a great extent on what comprises the load and on the resulting stability of AC motors within the microgrid. Simulations carried out as part of this research show that using static devices (an energy storage unit, ESU, and an active load, AL) is an effective solution that can prevent unnecessary GPU disconnections. The paper thus provides recommendations on how to calculate the electrical parameters to optimize ESU and AL configurations. Use of state-of-the-art static devices coupled with additional engineering helps prevent unnecessary GPU disconnections and ensure continued electricity delivery to industrial loads in case a transient causes a short-term frequency deviation.