Compared with calculating the feed water flow through heat balance based on the condensate flow

measuring the feed water flow directly makes the steam turbine performance tests more simple and convenient. At present

some units in our country try to measure the feed water flow by the throat-tap nozzle with low β value. In order to verify the reliability of this method

according to the method and requirement of the ASME PTC6 heat rate tests

the comparison experiments were carried out of the water flow and the condensate flow at an ultra-supercritical 660 MW unit respectively. The results show that both of them have good repeatability. When the load is above 75% THA

the deviation is-0.5%-0.2%

the deviation of THA load is only about ±0.2%. And when the load is as low as 50% THA

the deviation is only about 1.2%. This results indicate that these two methods have good measurement accuracy

which can meet the turbine performance requirement of assessment tests

pre-overhaul tests and overhaul tests. Some nozzles appear poor consistency in the differential pressure measurement

which is because of the nonstandard installation and operation of differential pressure transmitter. And the nozzle surface fouling problems need long-term observation.