If the pole discordance protection is enabled, then two different criteria can generate
a trip signal TRIP:
•
Pole discordance signaling from the circuit breaker.
•
Unsymmetrical current detection.
8.9.7.1
Pole discordance signaling from circuit breaker
If one or two poles of the circuit breaker have failed to open or to close the pole
discordance status, then the function input EXTPDIND is activated from the pole
discordance signal derived from the circuit breaker auxiliary contacts (one NO contact
for each phase connected in parallel, and in series with one NC contact for each phase
connected in parallel) and, after a settable time interval
tTrip
(0-60 s), a 150 ms trip
pulse command TRIP is generated by the Polediscordance function.
8.9.7.2
Unsymmetrical current detection
Unsymmetrical current indicated if:
•
any phase current is lower than
CurrUnsymLevel
of the highest current in the
three phases.
•
the highest phase current is greater than
CurrRelLevel
of
IBase
.
If these conditions are true, an unsymmetrical condition is detected and the internal
signal INPS is turned high. This detection is enabled to generate a trip after a set time
delay
tTrip
if the detection occurs in the next 200 ms after the circuit breaker has
received a command to open trip or close and if the unbalance persists. The 200 ms
limitation is for avoiding unwanted operation during unsymmetrical load conditions.
The pole discordance protection is informed that a trip or close command has been
given to the circuit breaker through the inputs CLOSECMD (for closing command
information) and OPENCMD (for opening command information). These inputs can
be connected to terminal binary inputs if the information are generated from the field
(that is from auxiliary contacts of the close and open push buttons) or may be software
connected to the outputs of other integrated functions (that is close command from a
control function or a general trip from integrated protections).
8.9.8
Technical data
Table 212:
CCPDSC technical data
Function
Range or value
Accuracy
Operate current
(0–100)% of
IBase
±1.0% of I
r
Independent time delay between
trip condition and trip signal
(0.000-60.000) s
±0.2% or ± 25 ms whichever is
greater
Section 8
1MRK502052-UEN B
Current protection
418
Technical manual
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