In electrical engineering, the Ferranti effect is an increase in voltage occurring at the receiving end of a long transmission line, above the voltage at the sending end. This occurs when the line is energized, but there is a very light load or the load is disconnected. The capacitive line charging current produces a voltage drop across the line inductance that is in-phase with the sending end voltages considering the line resistance as negligible. Therefore both line inductance and capacitance are responsible for this phenomenon.
The Ferranti effect is much more pronounced in underground cables, even in short lengths, because of their high capacitance.
- Ferranti Effect handout, Kathmandu University (internet archive)
- Line-Charging Current Interruption by HV and EHV Circuit Breakers, Carl-Ejnar Sölver, Ph. D. and Sérgio de A. Morais, M. Sc.
- A Knowledge Base for Switching Surge Transients, A. I. Ibrahim and H. W. Dommel
- J. F. Wilson, Ferranti and the British Electrical Industry, 1864-1930, Manchester University Press, 1988 ISBN 0-7190-2369-6 page 44