Function
Range or value
Accuracy
Impulse margin time,
overcurrent
15 ms typically
-
Operate value,
undervoltage
(2-150)% of VBase
± 0.5% of V
n
at V<V
n
± 0.5% of V at V>V
n
Critical impulse time,
undervoltage
10 ms typically at 2 to 0 x V
set
-
Impulse margin time,
undervoltage
15 ms typically
-
Operate value,
overvoltage
(2-200)% of VBase
± 0.5% of V
n
at V<V
n
± 0.5% of V at V>V
n
Timers
(0.000-60.000) s
± 0.5% ± 25 ms
8.9
Negative-sequence time overcurrent protection for
machines NS2PTOC (46I2)
8.9.1
Identification
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Negative sequence time overcurrent
protection for machines
NS2PTOC
2I2>
46I2
8.9.2
Functionality
Negative-sequence time overcurrent protection for machines NS2PTOC (46I2) is
intended primarily for the protection of generators against possible overheating of the
rotor caused by negative sequence current in the stator current.
The negative sequence currents in a generator may, among others, be caused by:
•
Unbalanced loads
•
Line to line faults
•
Line to ground faults
•
Broken conductors
•
Malfunction of one or more poles of a circuit breaker or a disconnector
NS2PTOC (46I2) can also be used as a backup protection, that is, to protect the generator
in case line protections or circuit breakers fail to clear unbalanced system faults.
1MRK 502 048-UUS A
Section 8
Current protection
265
Technical manual
