GE B90 Instruction Manual page 236

5.6 CONTROL ELEMENTS
This element responds to both normally open and normally closed auxiliary contacts of an isolator or a tie-breaker in order
to assert the actual position of the isolator for the dynamic bus image. The element asserts two extra output operands indi-
cating "isolator alarm" (auxiliary contact discrepancy), and "block switching operations in the substation". The operation of
the element is summarized in the following table.
Table 5–18: ISOLATOR MONITORING LOGIC
ISOLATOR OPEN
AUXILIARY CONTACT
Off
Off
On
On
The position of an isolator is indicated by the ISOLATOR N POSITION FlexLogic™ operand (On = Closed, Off = Open).
This operand is used as a circuit connection status for the bus configuration. When "On", the related current is associated
with a given differential zone; when "Off", the current is excluded from differential calculations.
An isolator alarm FlexLogic™ operand, ISOLATOR 1 ALARM, is asserted after a settable time delay if the auxiliary contacts
of the isolator do not match (open-open, closed-closed instead of open-closed or closed-open), yielding an undefined isola-
tor position. The operand may be used to block user-selected protection functions and may be reset manually or remotely
via the resetting input operand.
The ISOLATOR 1 BLOCK operand is asserted as long as the isolator position is invalid. This operand may be used to block
switching operations in the substation. Typically, breakers and isolators that control currents flowing through a given isolator
shall be blocked from operation as long as isolator position is not resolved.
5
The element is effectively enabled only when
the Chapter 9: Application of Settings for more details on the usage of the Bus Replica element.
• ISOLATOR 1 OPEN: This setting specifies a FlexLogic™ operand that represents an auxiliary contact of the monitored
isolator. Typically this setting is a status of an appropriately wired input contact ("On" = isolator open).
• ISOLATOR 1 CLOSED: This setting indicates a FlexLogic™ operand that represents an auxiliary contact of the moni-
tored isolator. Typically this setting is a status of an appropriately wired input contact ("On" = isolator closed).
• ISOLATOR 1 ALARM DELAY: This setting specifies a time delay after which an isolator alarm is issued by asserting
the operand assigned to
the isolator.
5-116
ISOLATOR CLOSED ISOLATOR POSITION
AUXILIARY CONTACT
On
Off
On
Off
PRODUCT SETUP
+
F7a
F7c
F7b
–
Figure 5–56: TYPICAL ISOLATOR OPEN/CLOSED SETTINGS
. The delay shall be longer than the slowest operation (transition) time of
ISOLATOR 1 ALARM
B90 Low Impedance Bus Differential System
ALARM
CLOSED No
LAST VALID After time delay
until acknowledged
CLOSED
OPEN No
 
B90 FUNCTION B90 FUNCTION
ISOLATOR 1 OPEN setting =
Contact Input 7a On
B90
FLEXLOGIC OPERANDS
Contact Input F7a On
Contact Input F7c On
ISOLATOR 1 CLOSED setting =
Contact Input 7c On
5 SETTINGS
BLOCK SWITCHING
No
Until Isolator
Position is valid
No
is set to "Logic". Refer to
836743A1.vsd
GE Multilin