RCCB and RCD is the same, just different naming convention in UK and USA.
RCCB/RCD is circuit breaker that function by comparing current going out and back in. It monitors the phase and neutral and if there is a difference it trips. It does not require earthing. It comes in both single phase (2 pole) and 3 phase (4 pole). They come in sensitivity rating of 10, 30, 100, and 300 mA. 30mA is commonly used in homes.
I have one Schneider 100 A - 30mA - 3 phase 4 pole RCCB installed in main DB to protect the whole house. If wiring is proper and there is no broken insulation or exposed wires it does not trip randomly. You can use 3 x 2 pole single phase RCCB one for each phase to isolate the tripping to individual phase if you have to.
RCCB is available here but general electric stores don't keep them. I had to go to a Schneider dealer in electric market (brandth road I think) in inner Lahore to get one.
In UK they have RCBO that they use instead of MCBs. RCBO is a combination of MCB and RCCB. RCBO is available here but they are expensive.
10mA or 30mA 2 pole RCCB is ideal if some one wants protection against unwanted electrocution from electric geyser etc while good electric geysers and bath tubs come with RCCBs in their plugs.
