ABB REG670 Product Manual page 26

Generator protection REG670 2.2 and Injection equipment REX060,
REX061, REX062
Product version: 2.2.1
tripping of surrounding breakers at an incorrect initiation due
to mistakes during testing.
Pole discordance protection CCPDSC
An open phase can cause negative and zero sequence
currents which cause thermal stress on rotating machines
and can cause unwanted operation of zero sequence or
negative sequence current functions.
Normally the own breaker is tripped to correct such a
situation. If the situation persists the surrounding breakers
should be tripped to clear the unsymmetrical load situation.
The Pole discordance protection function (CCPDSC) operates
based on information from auxiliary contacts of the circuit
breaker for the three phases with additional criteria from
unsymmetrical phase currents when required.
Directional over/underpower protection GOPPDOP/
GUPPDUP
The directional over-/under-power protection (GOPPDOP/
GUPPDUP) can be used wherever a high/low active, reactive
or apparent power protection or alarming is required. The
functions can alternatively be used to check the direction of
active or reactive power flow in the power system. There are
a number of applications where such functionality is needed.
Some of them are:
• generator reverse power protection
• generator low forward power protection
• detection of over/under excited generator
• detection of reversed active power flow
• detection of high reactive power flow
• excessive line/cable loading with active or reactive
power
• generator reverse power protection
Each function has two steps with definite time delay.
By using optional metering class CT inputs accuracy of 0,5%
can be achieved for steam turbine applications.
Voltage-restrained time overcurrent protection VRPVOC
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
26
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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
standard IEEE C50.13.
where:
I is negative sequence current expressed in
2
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
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
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
1MRK 502 074-BEN A
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=
I t K
as defined in
2
K settings and the sensitivity
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