The best solution is to model the voltage uncertainty with the probability distribution - normal distribution if you have the mean and the standard deviation of measurements. Then, you can apply Monte Carlo simulation   

In order to answer the question, we need to know what kind of info is in hand regarding the voltage values. 

Please have a look at the following references: 

Article Decision making under uncertainty in energy systems: State of the art

Data uncertainty modeling visualization

Dear Alireza Soroudi

   Many thanks for the papers.

Dear Aleksandar Janjic

Many thanks for your answer.