Aberrant amplification of torsional oscillating torques in turbine-generator shaft due to multiple EAF operation

Electric arc furnace (EAF) acts as a source of sub-synchronous frequencies (SSFs) in the electrical network. If these SSFs lead to resonance, respective matched torsional modes of turbine-generator (T-G) shaft are excited causing torsional oscillating torques (TOTs) amplification. This may lead to gear damage, shaft fatigue lifetime reduction, severe damages to T-G shaft. This paper presents an assessment of TOTs amplification due to multiple EAF operations at the same PCC. The EAFs have been modeled using mathematical model of the electric arc, where resistances of EAFs varied deterministically in frequency range of 1.2-45.5 Hz to comport with realistic EAF. TOTs have been measured with/without resonant excitation of torsional modes. Eigenvalue analysis and FFT technique have been used to analyse torsional torques.