NHP Terasaki TemBreak PRO P SE Series, User Manual

Page: 48 / 122

Protection Settings
Zone Selective Interlocking Function (ZSI)
48
TemBreak PRO
P_SE-UM-001-EN
– V1.2.0
ZSI example A
Fault example a):
A short circuit or ground fault occurs downstream of MCCB Q3. All upstream MCCBs Q1, Q2 and Q3 detect the fault at the same time. The ZSI signalling
cable between the circuit breakers produces a signal from Q3, which informs Q2 that the downstream circuit breaker has detected the fault. Q2, also detects
the same fault, produces its own ZSI signal, which informs Q1 and so on. As Q1 and Q2 have both received the ZSI signal, they maintain their respective
time delays so that Q3 can eliminate the fault instantly.
ZSI example B
Fault example b):
A short circuit or ground fault occurs downstream of MCCB Q2. Only upstream MCCBs Q1 and Q2 detect the fault. As per example a), the ZSI signalling
cable between the circuit breakers produces a signal from Q2, which informs Q1 that the downstream circuit breaker it has detected the fault. Q1 then
maintains its time delays whilst Q2 overrides its pre-set time delays to eliminate the fault instantly, thus reducing the overall clearance time of the fault whilst
maintaining selectivity.
Tier 1
Tier 2
Tier 3
Tier 1
Tier 2
Tier 3