This is the structure for ACN's Management Consulting internship interviews for 2012:

Round 1: Initial CV/Resume Screening (after ~1 week of application)
Round 2: Human Resources Phone Interview; basic CV screening & English proficiency test (after ~1 week of Round 1)
Round 3: Interview with Manager; behavioural questions; career aspirations; understanding of role & ACN (after ~1.5 weeks of Round 2)

I would assume for Graduate roles there would be a Fourth Round which would involve group case study work, 1-1 Case study work & further psychometric tests.

All the best!