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 substations and static VAr controllers. This paper presents a measuring method to be be used during the valve type tests with the intention to verify the guaranteed loss characteristic. The method was validated under laboratory conditions by comparison to a sophisticated calorimetric technique. An uncertainty of 1% was achieved at conditions simulating full load operation. Voltage across and current through the valve are recorded in discrete steps and digitized. The loss is then calculated as their product. Special current and voltage sensors were developed to cover a very high dynamic range of the measured quantities. A high resolution, multichannel digital recorder was used for simultaneous registration of two voltage and two current signals. The method is of a general application, since the valve is treated as a two port circuit. Therefore, it can be used to measure loss in other nonlinear components and apparatus, where large dynamic changes of the measured quantities preclude application of conventional techniques