A typical household RCB will trip on a 60 or 100mA difference in supply
current surges up to 60A. That's pretty good common-mode rejection!
==========
Don't want to be pedantic but the RCDs in domestic switchboards in the UK
(at least here in Scotland ) trip at 30 mA .
I just had a look at my house's switch board made by SQUARE -D (England)
to British Standard BS5486 pt 13

In UK industry I have come across RCDs which trip at 100 mA

Frank GM0CSZ / KN6WH