A ±150 MVAr STATCOM for Northeast Utilities´ Glenbrook substation

Northeast Utilities (NU), located in Hartford, Connecticut, is preparing to install a new flexible AC transmission system (FACTS) voltage sourced controller at its Glenbrook 115 kV substation in Stamford, Connecticut. Glenbrook is located within the Norwalk-Stanford area of southwestern Connecticut. In the summer of 2000, a low voltage event occurred in the area. Voltage recovery took approximately 8 to 10 seconds. Transmission planning studies have confirmed that the Norwalk-Stamford area is susceptible to a possible voltage collapse during certain contingencies. To mitigate similar low voltage conditions, three possible solutions were investigated by NU; install fixed shunt capacitors, upgrade existing overhead lines to a higher voltage level, and install a FACTS device. Of the three alternatives investigated, NU concluded that a FACTS device was the only near term viable option. The function of the STATCOM and its location on the system are discussed. Reasons for the finally chosen configuration are give, the choice being made to maximize availability, even following a circuit breaker failure or bus fault. The overall design of the STATCOM and its layout are described, together with a description of the chain-link voltages sourced converter.