LOSS MEASUREMENT IN HIGH-VOLTAGE THYRISTOR VALVES

No measuring method is presently available for direct and sufficiently accurate evaluation of power losses in thyristor valves used in HVDC converter stations and Static VAR controllers. This paper presents a m easuring method to be be used during the valve type tests with the int ention to verify the guaranteed loss characteristic. The method was va lidated under laboratory conditions by comparison to a sophisticated c alorimetric technique. An uncertainty of 1 % was achieved at condition s simulating full load operation. Voltage across and current through t he valve are recorded in discrete steps and digitized. The loss is the n calculated as their product. Special current and voltage sensors wer e developed to cover a very high dynamic range of the measured quantit ies. A high resolution, multichannel digital recorder was used for sim ultaneous registration of two voltage and two current signals. The met hod is of a general application, since the valve is treated as a two p ort circuit. Therefore, it can be used to measure loss in other non-li near components and apparatus, where large dynamic changes of the meas ured quantities preclude application of conventional techniques.