EXACT ZERO DETERMINATION AND INTEGRATION TERMINATION FOR PRESSURE – TIME METHOD

This paper presents engineering approach to exact pressure difference zero determination and termination of integration which is based on following physical facts: The person performing the flow measurement usually knows, which flow rate can be expected after unit shut down. The discharge can’t grow or drop, if the valve in front of turbine is closed and tight, because in this case the flow rate is zero. Similar situation occurs if small leakage through guide vanes or other closing apparatus remains after unit shut down. In this case the final leakage is almost constant and it can change with pressure / head oscillation. The mean value of leakage Q0 has to be determined other way than pressure – time procedure. But the water mass oscillation in penstock after guide vane closing is presented as small flow oscillations
with constant mean value Q0. Algorithm based on mentioned phenomenon evaluates the pressure difference part after guide vane or main intake valve closing.
KEYWORDS: turbine, valve, measurement.

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