CBF protection is a breaker backup protection and provided locally, hnece it is alco called as LBB (LOCAL BREAKER BACKUP PROTECTION). Generally in India we adopt a setting of 200mA (SECONDARY) for all feeders and transformers with a time delay of 200msec (This includes Breaker opening time, Protection reset time, Trip relay rest time, Arc deionisation time and margin). For generators, current setting will be lower in the range of 50mA, time delay will be 200msec. I thought 200 msec time delay should be good enough to ensure stability of CBF. In the new CBF protections, retrip function is available which trips its own breaker again before initiaing tripping of backup breakers. Retrip time delay is set between 50-70msec. What are the currents ettings and time delay settings adopted in your application?