765 kV power transformer losses upon energizations: A comparison between field test measurements and EMTP-RV simulations

• Power transformer high saturation was performed in Quebec substation.
• Saturation and hysteresis losses were calculated.
• An enhanced transformer model has been developed in EMTP-RV Software.
• The new model helps to predict adequately the risks of ferroresonance and generated over-voltages in power systems.

Transformer energization tests were performed in Hydro-Québec Chateauguay substation on a 300 MVA single-phase 765/125/12.5 kV Yg-Yg-Δ power transformer in order to improve power transformer modeling for harmonic over-voltage evaluations upon energizations and fault removals close to HVDC converters with associated filters and capacitor banks. From these results, an enhanced transformer model has been developed in EMTP-RV Software. Subsequent simulations show that accurate modeling of the power transformer losses does only have minor influences on harmonic over-voltages damping. It is shown however that the usage of the proposed model is essential to predict adequately the risks of ferroresonance and generated over-voltages in power systems.