Understanding a breaker scheme is important if you plan on designing a substation. Quite often, it is overwhelming to make sense of the entire scheme at a glance. The figure below depicting a circuit breaker scheme will be used to explain various elements of the PCB’s design and its control.
The DCUB Scheme, like POTT Scheme, uses two frequencies to maintain system protection. When the system is operating under normal condition, the transceiver emits the “Guard” frequency. When a fault appears in the system, the distance relays shift the carrier to “Trip” frequency. This is where the similarities between POTT and DCUB schemes end.
The maximum load in kVA the transformers can supply (combined) without overloading any one , is determined by the transformers impedance. They load up inversely proportional to their impedance.
POTT scheme works using the following logic:
Fault in Zone 2 AND permission-to-trip signal from remote end relay.
