The appearance of the power frequency overvoltage in the transmission network

High voltage transmission network in Bosnia and Herzegovina registered significant values of power frequency overvoltages which lasted quite long. This paper identified levels of temporary overvoltages on the basis of measurement results in an annual period during 2010 in specific points of 220 kV and 400 kV network. Measurements were made that exceeded upper voltage limits in relation to referential voltages and their duration for the considered measurement time. In order to indicate the problem of overvoltages in the transmission network additional voltage measurements were made during 2011 in a specific point Mostar 4, on the 440 kV side and in a point Prijedor 2, on the 220 kV side. For specific 220 kV and 400 kV overhead lines overvoltage calculations were made by using ATP-EMTP. Comparison with the measured values indicated good correlation of the measurement results and the calculation. The paper indicates the need for new methods of implementation in order to reduce overvoltages since the existing methods are not sufficient.