GE Industrial Solutions Entellisys System User Manual - Manual (Page 104)

Multipoint functions 104
7
7.4.4 Topologies
A topology is the state of the circuit breakers that control the system's power flow. Such circuit
breakers are also referred to as topology circuit breakers. Since the Entellisys system is for
main-tie-main (M-T-M) topologies and is limited to 4 buses, the total possible number of different
topologies is 16. The mathematical formula for the total number of topologies is 2
B
, where B is
the number of buses in the system. The number of topologies affects the number of tiers values
that each member circuit breaker needs to be configured with.
7.4.5 Tiers
In order for the ZSI to manage the hierarchy in a dynamic power system, it has to keep track of
the current topology that the system is in. Whenever the system changes topology, ZSI reacts
by using new tier settings for all member circuit breakers of the affected zones.
Each member circuit breaker can have up to 16 different tier values. The user is responsible for
providing tier information for the ZSI. Entellisys allows four different tier values from 0 through 3.
Tier 0 indicates that the circuit breaker is the highest in the hierarchy and Tier 3 indicates that it
is the lowest. Multiple circuit breakers within a zone may have the same tier values, if it makes
sense from the system hierarchy standpoint.
7.4.6 Algorithm
When enabled, the ZSI zone tracks all its member circuit breakers for any GF/MSGF or/and ST
fault conditions. If a member circuit breaker goes into pickup, ZSI reacts. Based on the current
topology's tier settings for member circuit breakers, ZSI adjusts the time delays of upstream
member circuit breakers. It starts from one tier higher than the circuit breaker in the detected
pickup condition. The time delay of the circuit breaker in pickup is not adjusted. However it is
used as the starting point for calculating new time delays for circuit breakers positioned higher
in the hierarchy. Upstream circuit breakers are updated with new time delays regardless of their
current state (whether they are open or closed or whether they are in pickup or not). The new
delay value is a function of the time delay of the member circuit breaker that is immediately
downstream and the difference between the current tier value of that circuit breaker and the
circuit breaker that new time delay is being calculated for. The mathematical formula for this is:
Equation 7-1 Mathematical formula for time delay calculation
d = d
d
+ (t – t
d
) * 100
where:
d = the new time delay of circuit breaker
d
d
= the current time delay of the immediately downstream circuit breaker
t = the current tier value of the circuit breaker that the time delay is calculated for
t
d
= the current tier value of the immediate downstream circuit breaker.
The new time delay is calculated in milliseconds.