sepam 20 user manual - Schneider Electric

Control and monitoring
functions
Description
This function provides:
b full tripping discrimination
b a substantial reduction in delayed tripping of the
circuit breakers located nearest the source (drawback
of the classical time-based discrimination process).
The system applies to the definite time (DT) and IDMT
phase overcurrent and earth fault protection functions.
DE80349
DE80350
td: X+0.9s
td: X+0.6s
e.g.: Radial distribution with use of time-based discrimination
(td: tripping time definite time curves).
td: Xs
PCRED301005EN - 06/2008
td: X+0.3s
td: Xs
td: Xs
td: Xs
BI order
td: Xs
e.g.: radial distribution with use of the Sepam logic
discrimination system.
MT10195
Logic discrimination
ANSI code 68
With this type of system, time delays are set in accordance with the device to be
protected, without any concern for the discrimination aspect.
Operating principle
O3 output
other level
"n" Sepam
level "n+1"
Sepam
level "n"
Sepam
sending of BI
When a fault occurs in a radial network, the fault current flows through the circuit
between the source and the location of the fault:
b the protection units upstream from the fault are triggered
b the protection units downstream from the fault are not triggered
b only the first protection unit upstream from the fault should trip.
Each Sepam is capable of sending and receiving blocking input orders except for
motor Sepams (1) which can only send blocking input orders.
When a Sepam is triggered by a fault current:
b it sends a blocking input order to output O3 (2)
b it trips the associated circuit breaker if it does not receive a blocking input order on
the blocking input logic input (3) .
The sending of the blocking input lasts the time it takes to clear the fault.
It is interrupted after a time delay that takes into account the breaking device
operating time and protection unit reset time.
This system minimizes the duration of the fault, optimizes discrimination and
guarantees safety in downgraded situations (wiring or switchgear failure).
Pilote wire test
The pilot wire test may be performed using the output relay test function.
O3
(1) Motor Sepams are not affected by the receipt of a blocking input since they are designed for
loads only.
(2) Default parameter setting.
(3) According to parameter setting and presence of an additional MES114 module.
O3
receipt of BI
-
+
4/9
4