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NC20 - Manual - 01 - 2015
FUNCTION CHARACTERISTICS
Trip circuit supervision - 74TCS
Preface
The trip circuit can be monitored to signal possible anomalies that would lead to the missing opening
of circuit breaker when trip and/or operator command are issued.
Circuit interruption as well as missing of auxiliary voltage and/or coil faults are detected.
Supervision with one or two binary inputs can be select; depending on association of binary inputs,
the corresponding logic is automatically selected.
For this purpose the
TCS1
and
TCS2
(if two binary input are used) matching must be assigned to the
selected binary inputs inside the
Set \ Inputs \ Binary input IN1
and
Set \ Inputs \ Binary input INx
menus.
When a binary input is programmed for the TCS function, the
IN1 tON
,
INx tON
,
IN1 tOFF
and
INx tOFF
time delays must be reset to zero and the
Logic
parameter must be set to
Active-ON
inside the
Set \ Inputs \ Binary input IN1
and
Set \ Inputs \ Binary input INx
menus.
Operation and settings
The 74TCS element may be enabled or disabled; to enable it, the
74TCS Enable
parameter must be
set to
ON
inside the
Set \ Profi le A(B) \ Trip circuit supervision-74TCS
submenu.
A logic block can be set from une binary input.
[1]
If the
74TCS-BLK1
parameter is set to
ON
, and a binary input is designed for logical block (Block1),
the TCS supervision function is blocked off whenever the given input is active. The trip timer is held
in reset condition, so the operate time counting starts when the input block goes down. The
74TCS-
BLK1
parameter is available inside the
Set \ Profi le A(B) \ Trip circuit supervision-74TCS
submenu.
All the parameters can be set separately for
Profi le A
and
Profi le B
.
Two inputs supervision
With two binary input all malfunctions are detected (inclusive of mechanics faults).
The binary inputs are connected to the trip and to the 52b contacts.
The CB auxiliary voltage must be 36 V at least (twice the minimum threshold for every binary input).
The faulty condition is detected occurs if both the following conditions are fi lled:
The TRIP contact is closed (external protection relay tripped);
The circuit breaker is closed (52a closed and 52b open).
Because such conditions can arise with healthy circuit too (e.g. a trip command is issued by the
protection relay but the CB opening time is still in progress), to avoid untimely operations the previ-
ous condition are checked every 80 ms and the output is issued after a 2 s delay; outputs are reset
to zero if at least the A or B condition become false after 0.6 s delay.
[2]
Note 1 Since two binary inputs are just used (TCS1 and TCS2), an external I/O module is required for the logic block function. The exhaustive treatment
of the logic block (Block 1) function may be found in the “Logic Block” paragraph inside
CONTROL AND MONITORING
section
Note 2 Following assumption are considered for the framework:
Logic:
ON,
Timers
t
ON
and t
OFF:
reset to zero
TRIP contact of the protection: DE-energized, No latched
A)
B)
TCS2s.ai
TRIP
+
U
AUX
Trip circuit supervision with two binary inputs - 74TCS
-
U
AUX
52a
52b
52
Pro-N
Binary input IN1
Binary input IN2
TCS1
TCS2
Towards 74TCS logic
Towards 74TCS logic
