Analytic calculation of active power error

Question

I have a component on a board which calculate the active power and reactive power. The component first mesure the voltage, the intensity and the phase then calculate the powers with:

P = U * I * cos(phy)

Q = U * I * sin(phy)

I know the whole chain of voltage measurement (filter, transformer, ADC) has an accuracy of 0,6%. I know the whole chain of intensity measurement (filter, transformer, ADC) has an accuracy of 0,9%. I know the whole chain of phase measurement (filter, transformer, ADC) has an accuracy of 5,9°.

I need to do it for a general measure, I mean i can't use the partial derivative method because I don't have the value of U,I and phy.

Is there any way to calculate it?

Answer 1

You know P and Q, hence you can determine phi and U*I. Now use actual maximum deviations to find the absolute errors and select +/- worst cases