How we can make EVM practically effective for Large refinery projects?

EVM is basically a technique to forecast the time of completion and budget at completion against the planned values for any project, big or small.

For a large refinery project, the team has to provide with an accurate Critical Path Method schedule, which would be the basis for EVM. Much deeper understanding and time has to be given for forming the work breakdown structure, activities that can be carried out in series or parallel, duration based on resource and effort. After getting the closer picture of the project's day to day activities, one can control over the variances and over-runs.

EVM is just a tool to forecast, which can be effective in any scale of project, so far all the pre-requisites are properly worked out and accurate.