GE Industrial Solutions Entellisys 4.0 System User Manual - Manual (Page 121)

Zone Selective Interlock 121
7
There are a couple of restrictions in place for this calculation. The newly calculated time delay
cannot exceed 400 ms. If new time delay is longer than 400 ms, the circuit breaker is assigned a
delay of 400 ms. The other restriction is if the newly calculated time delay is shorter than the
current time delay of the circuit breaker, no delay adjustment is performed. However, that
unchanged time delay becomes the basis for the calculation of the time delays of the rest of the
upstream circuit breakers.
Once the circuit breaker clears the fault, the algorithm begins the process of restoring the time
delays of all involved circuit breakers to their original values. As soon as a circuit breaker's
accumulator is cooled and the accumulators of all downstream circuit breakers are also cooled,
the time delay for the circuit breaker is restored to its original setting.
Each member circuit breaker can have up to 16 different tier values that correspond to 16
possible different topologies. The actual number of tier values that a circuit breaker needs to be
configured with depends on the system size and layout. ZSI reacts to dynamic changes in the
current topology by switching to corresponding pre-configured tier values for member circuit
breakers of affected zones.
NOTE: When a topology change occurs while ZSI is operating and before it is able to restore
time delays of member circuit breakers to their original values, ZSI postpones switching until the
zone is idle. Only after the accumulators of all member circuit breakers in the zone are cooled,
does the ZSI switch to the corresponding new topology tier set for member circuit breakers.
7.4.7 Setup
ZSI setup is done in three steps. Briefly, the steps are:
1. Set tiers for member circuit breakers
2. Enable zones
3. Set ZSI protection type
Each of these steps is described in greater detail below.
7.4.7.1 Configuring ZSI parameters
To perform the ZSI configuration, a user must be logged in with at least administrator privileges.
Before ZSI zones can function properly, electrical hierarchy of each zone must be configured.
This is done by assigning tier values for every member circuit breaker.
To set the tiers
1. On the Main Menu, click User Settings, and then click Advanced Protection.
2. On the Advanced Protection screen, click ZSI.