ABSTRACT
Insulation co-ordination of winding system and plant design of system solutions with Powerformer™, the brand name of a cable wounded high-voltage generator that offer a direct connection to a high voltage network, is described. The paper deals briefly with parameters taken into account when designing the winding system of a high voltage generator. In comparison with a conventional generator, normally galvanic separated from the high voltage network via a step-up transformer, the winding system of a high voltage generator will be subjected to transient voltage levels that are distinctive characteristics of the principle of system earthing of the network concerned. The number and the duration of prospective single line to earth fault in non-effectively earthed network are also to be considered. Lightning stroke density, typical lightning parameters such as peak current, summer and winter conditions typical of the area concerned as well as the distance between the switchyard and the powerhouse are also essential parameters in the design work on the winding system concerned. The design of the insulation co-ordination of the winding system, herein the procedure of selection and location of surge arresters, selection of cables and the final decision making concerning a totally insulated winding system or not is described. The design of the winding system might have an essential impact on the physical size of Powerformer and the total space needed for the installation of the generation unit concerned. An example illustrating the technical benefits of a totally insulated cable winding system with incorporated surge arresters located close to Powerformer is elaborated.
