Calculation of Short-Circuit Currents of HVDC Installations for the Planning and Operation of Secure AC Networks

In principle, HVDC installations contribute to a short circuit in the AC network, so this short-circuit current must be taken into account when designing the installations. Because of the increased use of converter installations in three-phase networks (AC), it is necessary to consider their contribution to a short circuit in the network calculation. While self-commutated installations (VSC) are already taken into account by a suitable current source in the currently valid IEC Standard “Short-Circuit Calculation”, this standard misses the instruction how to proceed in case of a line- commutated installation (LCC). For this reason, this report presents a procedure to calculate the discharge process of the DC side of a line-commutated system as a voltage source. The results are compared with detailed simulations taking into account the control and commutation errors during a short circuit. This procedure can be adopted in a revision of the relevant IEC Standard.