Requirement
When a transformer is energised, two main phenomena occur; an inrush current and a resulting voltage drop at its primary side. The amplitudes of these two phenomena depend greatly on the remnant (or residual) magnetic flux, the transformer’s saturation curve and the instant of energisation. Before being commissioned, it should be checked whether the transformer is compliant or not with the local electrical grid standards.
For the case of the connection of a wind power station to the French RTE grid (90kV), the client wished to consider the different energisation (simultaneous or sequential energisation) strategies (at the 21kV level) of the wind turbine transformers which respect the transient voltage drop limit (5%) at the connection point.
The electrical network studied is presented below :
EMTP model of the studied network
Realization
For the case of the wind power station connection to the RTE grid, CAPSIM built a numerical model of the electrical network on EMTP-RV. The transformers models were validated via tests results performed by the manufacturer. The properties of the power transformer such as the saturation curve and the remnant magnetic flux were included. Four (4) various transformer energisation strategies were then simulated and studied.
Results
The modelling and simulations with EMTP-RV helped to determine the transformer energisation strategies which respected the RTE voltage limits at the connection point.
Evolution of the RMS voltage at the RTE connection point (90kV) during sequential energisation of each feeder with the 2nd strategy
