FEASIBILITY OF THYRISTOR CONTROLLED SERIES CAPACITOR FOR DISTRIBUTIONSUBSTATION ENHANCEMENTS

While Thyristor Controlled Series Capacitors (TCS(ls) are already bein g used for control of transmission system power flows, the dynamic adj ustment of transmission infeed impedances presents other system enhanc ement opportunities. In the case of the Con Edison system, distributio n substation upgrades are severely constrained by limits to existing c ircuit breaker interrupting capabilities. Because additional transmiss ion line infeeds cannot-be provided without increasing fault current l evels, a TCSC was investigated for use as a fault current limiter. In order to demonstrate proper operation in the current limiting mode, El ectromagnetic Transients Program (EMTP) simulations were conducted. Th ree TCSC configurations are presented to illustrate that additional po wer can be provided during normal operation without increasing fault c urrents at the substation: 1) series compensation of existing 138 kV i nfeeds (to allow higher substation MVA uprates), 2) series compensatio n of new 138 kV infeeds (without fault current increases), and 3) a 13 .8 kV TCSC compensated link between two substations (to allow regulate d power transfer between substation buses).