Research on 1000kV series standard potential transformer

In order to meet the requirements of the traceability and transfer of the voltage value in the building of 1000 kV ultra-high voltage (UHV) power grid, this paper presents a principle of series standard potential transformer (SSPT) based on the theory of power frequency voltage summation method, in which the arrangement of primary windings are conventional, but the series circuits of secondary voltages need high voltage isolating transformers (HVIT). The principle provides a new method for the research and development of 1000 kV standard potential transformers (SPT) and establishes relevant equivalent circuit. However, in view of the accuracy of the HVIT that are greatly influenced by huge leakage reactance, this paper presents a method of compensating for the leakage reactance by connecting the capacitance in series with primary windings of HVIT. Experiments proved that the method can increase the accuracy of HVIT greatly and thus guarantee the whole accuracy of SSPT. The feasibility of the method has been proved through analyzing the circuit. Compared with the traditional electromagnetic SPT, the method can reduce the volume, weight and insulation requirements of single transformer greatly on the premise of meeting relative requirements of the withstand at power frequency voltage as well as the accuracy, and it also provides the prerequisite for conducting frequent on-site inspection.