MC30-BC
Doc. N°
MO-0365-ING
Copyright 2008
FW 980.09.01.X
Date
15.06.2022
Rev.
1
Pag.
21
of
37
4. Logic Blocking of Functions
4.1 - Blocking outputs
The instantaneous element of each of the protection functions (1F50, 2F50, 3F50, 1F50N, 2F50N, 3F50N) can
be programmed to control one of the Output Relays.
This relay picks-up as soon as the input quantity exceeds the set trip level of the Protection Function
associated and it automatically resets when the input quantity drops below the function reset level (
95% of
the trip level) or, in any case as soon as the time delay (tBF) of the Breaker Failure function is expired.
This instantaneous output can be used to activate the Blocking Input of another Protection Relay to implement
a logic selectivity system. As above explained, in case of Breaker Failure, the blocking output is released, and
the back-up protection enabled.
4.2
–
Blocking Inputs
The time delayed tripping of any of the Protection functions (1F51, 2F51, 3F51, 1F51N, 2F51N, 3F51N) can
be controlled by the activation of the Digital Input D1 (BI=Enable): in this case the set trip time delay of the
function is increased by “2xtBF” so that other Protection Relays (set with the same trip time delay) that send
the activation signal to the blocking Input D2, can trip before open and the C/B nearest to the Fault.
Also in this case, however, another “2xtBF” seconds from the expiry of the set trip time delay, the blocking
input is disregarded so allowing the protection relay to trip in case of Failure to open of the upstream Circuit
Breaker.
5. Output Relays
Four users programmable Output Relays are normally available R1, R2, R3, R4.
Each of them can be programmed to be controlled by any element (instantaneous or time delayed) of any of the
Relay Functions including Breaker Failure and Internal Relay Fault.
Each output relay can also be programmed to control
“OPEN” and “CLOSE” the C/B either by the Relay Keyboard
or via the serial communication bus
Moreover, the operation of each of the output relays can be programmed to be either Normally Deenergized
(energized on tripping of the controlling Functional Element) or Normally Energized (Deenergized on tripping of
the controlling Functional Element).
As an option (to be required when ordering the relay), the output relay “R4” can be replaced by a
Field Bus output
(CANBUS) that controls additional I/O modules for increasing the number of user programmable Output Relays
and Digital Inputs controlled from the main relay.
