Investigation of the Imbalance Current Compensation for Transformers Used in Electric Railways

Different transformer connections have different influences on the imbalance current introduced by the electric traction load. From transformers' symmetrical components matrices, the conditions under which there will be lest current injected into the primary windings of the transformer are studied. Capacitors or inductors can be installed to compensate the traction load to reach these conditions. Based on the deduced balance criteria, the compensation capacities for several specially connected transformers are researched. Analysis found out that for Scott transformer, Le-Blanc transformer and Modified Wood-bridge transformer, it is useful to install combination of inductors and capacitors on the secondary winding of transformers in order to reduce imbalance current.