3.7.14 Negativ sequence time overcurrent protection for machines
NS2PTOC (46I2)
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Negative sequence time overcurrent
protection for machines
NS2PTOC 2I2> 46I2
3.7.14.1 Application
Negative sequence overcurrent protection for machines NS2PTOC (46I2) is intended
primarily for the protection of generators against possible overheating of the rotor
caused by negative sequence component 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 the event line protections or circuit breakers fail to perform for unbalanced
system faults.
To provide an effective protection for the generator for external unbalanced conditions,
NS2PTOC (46I2) is able to directly measure the negative sequence current. NS2PTOC
(46I2) also have a time delay characteristic which matches the heating characteristic of
the generator I
2
2
t = K as defined in standard.
where:
I
2
is negative sequence current expressed in per unit of the rated generator current
t is operating time in seconds
K is a constant which depends of the generators size and design
A wide range of I
2
2
t settings is available, which provide the sensitivity and capability
necessary to detect and trip for negative sequence currents down to the continuous
capability of a generator.
Section 3 1MRK504116-UUS C
IED application
502
Application manual
To Next Page
Loading...
