Voltage-restrained time overcurrent protection VRPVOC
GUID-935E1CE8-601F-40E2-8D22-2FF68420FADF v6
Voltage-restrained time overcurrent protection (VRPVOC)
function can be used as generator backup protection against
short-circuits.
The overcurrent protection feature has a settable current level
that can be used either with definite time or inverse time
characteristic. Additionally, it can be voltage controlled/
restrained.
One undervoltage step with definite time characteristic is also
available within the function in order to provide functionality
for overcurrent protection with undervoltage seal-in.
Negative sequence time overcurrent protection for machines
NS2PTOC
GUID-DBF3EC07-D947-4483-ABD1-4F7D29F48D61 v6
Negative-sequence time overcurrent protection for machines
NS2PTOC 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 earth faults
• Broken conductors
• Malfunction of one or more poles of a circuit breaker or a
disconnector
NS2PTOC 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.
To provide an effective protection for the generator for
external unbalanced conditions, NS2PTOC is able to directly
measure the negative sequence current. NS2PTOC also has a
time delay characteristic which matches the heating
characteristic of the generator
2
2
I t
K
=
as defined in
standard IEEE C50.13.
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
NS2PTOC has a wide range of
K
settings and the sensitivity
and capability of detecting and tripping for negative sequence
currents down to the continuous capability of a generator.
In order to match the heating characteristics of the generator
a reset time parameter can be set.
A separate definite time delayed output is available as an
alarm feature to warn the operator of a potentially dangerous
situation.
Accidental energizing protection for synchronous generator
AEGPVOC
GUID-02AA771D-2DFA-4BEE-92FD-CBF0E0448FBA v6
Inadvertent or accidental energizing of off-line generators has
occurred often enough due to operating errors, breaker head
flashovers, control circuit malfunctions, or a combination of
these causes. Inadvertently energized generator operates as
induction motor drawing a large current from the system. The
voltage supervised overcurrent protection is used to detect
the inadvertently energized generator.
Accidental energizing protection for synchronous generator
(AEGPVOC) takes the maximum phase current input and
maximum phase to phase voltage inputs from the terminal
side. AEGPVOC is enabled when the terminal voltage drops
below the specified voltage level for the preset time.
Stator overload protection GSPTTR
GUID-A416C856-E438-4ED4-A43D-D05F718D6A41 v5
The generator overload function, GSPTTR is used to protect
the stator winding against excessive temperature as a result
of overcurrents. The functions operating characteristic is
designed in accordance with the American standard IEEE-
C50.13.
If internal generator components exceed its design
temperature limit, damage can be the result. Damage to
generator insulation can range from minor loss of life to
complete failure, depending on the severity and duration of
the temperature excursion. Excess temperature can also
cause mechanical damage due to thermal expansion. Since
temperature increases with current, it is logical to apply
overcurrent elements with inverse time characteristics.
For its operation the function either measures the true RMS
current of the stator winding or waited sum of the positive
and negative sequence components in the stator winding.
The function is designed to work on 50/60 Hz systems.
Rotor overload protection GRPTTR
GUID-E3AE6200-DB8D-4C49-A740-09366A333B4F v4
The generator overload function, GRPTTR is used to protect
the rotor winding against excessive temperature as a result of
overcurrents. The functions operating characteristic is
designed in accordance with the American standard IEEE-
C50.13.
If internal generator components exceed its design
temperature limit, damage can be the result. Damage to
generator insulation can range from minor loss of life to
complete failure, depending on the severity and duration of
the temperature excursion. Excess temperature can also
cause mechanical damage due to thermal expansion. Rotor
components such as bars and end rings are vulnerable to this
damage. Since temperature increases with current, it is
logical to apply overcurrent elements with inverse time
characteristics.
1MRK 502 068-BEN D
Generator protection REG670 2.1 IEC
Product version: 2.1
ABB
23
