by David Monllaó.
Hi Pratim,
I understand that if you need to get the grades using gradereport_user_get_grades_table web service is because you are processing these grades in an external application; if that is the case you will need a library for converting these grades to an excel, it would depend on your client's language. If you could do it within Moodle you could use lib/phpexcel or lib/csvlib.class.php.