xiaobaiti and other experts, please help EB2 485 interview

My 485 was based on the my hu*****and's EB2. He is primary applicatant. My hu*****and and two kids 485 got approved three weeks ago. And TSC send me a letter said, my case is pending with security check a week ago. (our case was at TSC)
And today, I just got an email for USCIS, my 485 case was transfered to Lincon, NE local office for interview.
My question are:
1. My address is at California, why the case transfer to NE?
2. What the interview could be?

Any ideas are appreciated.