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126
NC20 - Manual - 01 - 2015
FUNCTION CHARACTERISTICS
Circuit breaker supervision
Preface
Several diagnostic metering and monitoring function are available:
By means 52a and 52b auxiliary contacts, the CB position is acquired. Depending on such information
the Open and/or Close commands can be safely issued by user.
An adjustable threshold can be set for a wear estimate of the breaker contacts; the current values
(
Σ
I or
Σ
I
2
) are summed and compared to a user-adjustable threshold. When the threshold or the
number of operations is exceeded the relay can activate an output relay. The function helps to
adjust maintenance planning.
By means 52a and 52b auxiliary contacts, the opening time is calculated and compared to a user-ad-
justable threshold. If the threshold is exceeded the relay can activate an output relay.
Operation and settings
According to the conventional contact position
52a is the auxiliary contact that is in the same position as the circuit breaker, (52a open = CB
open),
52b is the auxiliary contact that is in the opposite position as the circuit breaker, (52a open = CB
closed).
To acquire the CB position, the
52a
and
52b
function must be set inside the
Set \ Inputs \ Binary
input 1
and
Set \ Inputs \ Binary input x
menus
.
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.
CIRCUIT BREAKER COMMANDS
Two output relays can be set to command CB opening and closing; the
CBopen-K
and
CBclose-K
function must be set inside the
Set \ Circuit breaker supervision \ LEDs-relays allocation
menu; the
CB position can be visualized by means two LEDs (
CBopen-L
and
CBclosed-L
parameters).
All the parameters are common for
Profi le A
and
Profi le B
.
CIRCUIT BREAKER DIAGNOSTIC
Four different criteria can be select.
Number of CB trip mode (
ModeN.Open ON
). When the number of operations (
N.Open
) is ex-
ceeded, an output relay and/or LED can be activated.
Cumulative CB currents mode (
ModeSumI ON
). When the per-phase value exceeds the thresh-
old, an output relay and/or LED can be activated.
Cumulative CB I
2
t mode (
ModeSumI^2t ON
). The tripping energy I
2
t is calculated on the base of
current measure at the time of the open command on the base of the circuit breaker opening time
provided for I
2
t calculation (
tbreak
). When the per-phase value exceeds the threshold, an output
relay and/or LED can be activated.
CB operating time mode (
Mode-tOpen ON
). The time interval between the trip command and the
CB open acquisition is calculated on the base of a programmable relay (
Ktrig-break
). When the
time interval (
tbreak>
) is exceeded, an output relay and/or LED can be activated.
The four criteria can be contemporaneously or separately set.
All the named parameters are available inside the
Set \ Circuit Breaker supervision \ CB Diagnostic
menu.
•
•
•
•
•
1)
2)
3)
4)
Fun-CB-position.ai
Logic diagram concerning the circuit breaker diagnostic function
Towards CB diagnostic
TR
IP
P
ING
M
A
TR
IX
(
L
E
D
)
52a ON/OFF
t
mask
0
T
t
mask
CB monitoring
Opening transition
52b ON/OFF
52a
52
52b
+
U
AUX
-
U
AUX
IN-
IN+
52a
IN-
IN+
52b
Binary input INx
T
0
INx
t
ON
T
0
n.o.
n.c.
INx t O N
Logic
INx t O F F
INx
t
OFF
Binary input INx
T
0
INx
t
ON
T
0
n.o.
n.c.
INx t O N
Logic
INx t O F F
INx
t
OFF
=1
