Static Var Compensators: A Solution to the Big Motor/Weak System Problem?

STATIC VAR COMPENSATORS (SVCs) with reactive power capabilities of hundreds of both positive and negative MVAR have been used for years by utilities to control reactive power flow in transmission and distribution systems. Smaller systems have been applied to industrial applications, principally for varying load situations, such as mine hoists, rolling mills, and arc furnaces. In recent years, some SVCs have been used to stabilize the utility and plant voltages in electrically remote locations, such as pumping stations, where relatively large motors are a major portion of the load. As well as being practical ways of controlling voltages, they are also often faster to supply and install than other utility solutions, such as getting approvals and installing new or higher voltage lines. It was found that a 0- to 30-MVAR SVC could be purchased, installed, and started up in less than one year at less cost than any utility solutions that could achieve the same voltage stabilization SVCs use solid-state switching devices to control reactive and capacitive currents flowing from the SVC to the power system. The switching can usually be controlled on a cycle-by-cycle basis, with reactive current and system voltage being used to determine the magnitude and phasing of the correction.