ABB REG670 Product Manual page 23

Generator protection REG670 2.2 and Injection equipment REX060,
REX061, REX062
Product version: 2.2.1
pole slipping. The main purpose of the pole slip protection
(PSPPPAM) is to detect, evaluate, and take the required
action for pole slipping occurrences in the power system.
Out-of-step protection OOSPPAM
The out-of-step protection (OOSPPAM ) function in the IED
can be used for both generator protection and as well for line
protection applications.
The main purpose of the OOSPPAM function is to detect,
evaluate, and take the required action during pole slipping
occurrences in the power system.
The OOSPPAM function detects pole slip conditions and trips
the generator as fast as possible, after the first pole-slip if the
center of oscillation is found to be in zone 1, which normally
includes the generator and its step-up power transformer. If
the center of oscillation is found to be further out in the power
system, in zone 2, more than one pole-slip is usually allowed
before the generator-transformer unit is disconnected. A
parameter setting is available to take into account the circuit
breaker opening time. If there are several out-of-step relays in
the power system, then the one which finds the center of
oscillation in its zone 1 should operate first.
Two current channels I3P1 and I3P2 are available in
OOSPPAM function to allow the direct connection of two
groups of three-phase currents; that may be needed for very
powerful generators, with stator windings split into two
groups per phase, when each group is equipped with current
transformers. The protection function performs a simple
summation of the currents of the two channels I3P1 and
I3P2.
Loss of excitation LEXPDIS
There are limits for the under-excited operation of a
synchronous machine. A reduction of the excitation current
weakens the coupling between the rotor and the stator. The
machine may lose the synchronism and start to operate like
an induction machine. Then, the reactive power consumption
will increase. Even if the machine does not loose synchronism
it may not be acceptable to operate in this state for a long
time. Reduction of excitation increases the generation of heat
in the end region of the synchronous machine. The local
heating may damage the insulation of the stator winding and
the iron core.
To prevent damages to the generator it should be tripped
when excitation is lost.
Sensitive rotor earth fault protection, injection based
ROTIPHIZ
The sensitive rotor earth fault protection (ROTIPHIZ) is used
to detect earth faults in the rotor windings of generators.
ROTIPHIZ is applicable for all types of synchronous
generators.
To implement the above concept, a separate injection box is
required. The injection box generates a square wave voltage
ABB
GUID-BF2F7D4C-F579-4EBD-9AFC-7C03296BD5D4 v8
SEMOD151269-4 v9
GUID-9D60105D-44C8-4FB1-AD63-C4D3631BC99E v2
signal at a certain preset frequency which is fed into the rotor
winding.
The magnitude of the injected voltage signal and the resulting
injected current is measured through a resistive shunt located
within the injection box. These two measured values are fed
to the IED. Based on these two measured quantities, the
protection IED determines the rotor winding resistance to
ground. The resistance value is then compared with the
preset fault resistance alarm and trip levels.
The protection function can detect earth faults in the entire
rotor winding and associated connections.
Requires injection unit REX060 and a coupling capacitor unit
REX061 for correct operation.
100% stator earth fault protection, injection based STTIPHIZ
The 100% stator earth-fault protection (STTIPHIZ ) is used to
detect earth faults in the stator windings of generators and
motors. STTIPHIZ is applicable for generators connected to
the power system through a unit transformer in a block
connection. An independent signal with a certain frequency
different from the generator rated frequency is injected into
the stator circuit. The responce of this injected signal is used
to detect stator earth faults.
To implement the above concept, a separate injection box is
required. The injection box generates a square wave voltage
signal which for example can be fed into the secondary
winding of the generator neutral point voltage transformer or
grounding transformer. This signal propagates through this
transformer into the stator circuit.
The magnitude of the injected voltage signal is measured on
the secondary side of the neutral point voltage transformer or
grounding transformer. In addition, the resulting injected
current is measured through a resistive shunt located within
the injection box. These two measured values are fed to the
IED. Based on these two measured quantities, the IED
determines the stator winding resistance to ground. The
resistance value is then compared with the preset fault
resistance alarm and trip levels.
When the synchronous machine is at standstill, the protection
function can not only detect the earth fault at the generator
star point, but also along the stator windings and at the
generator terminals, including the connected components
such as voltage transformers, circuit breakers, excitation
transformer and so on. The protection function is fully
operative in all operating conditions when stable
measurements are achieved. Both function STTIPHIZ and
ROV2PTOV shall be configured and shall operate in parallel in
the same REG670 in order to perform the 100% stator earth-
fault protection function. The function STTIPHIZ performs the
earth-fault protection based on the injection principle in order
to protect the section of the stator windings close to the
generator neutral point; the function ROV2PTOV performs the
1MRK 502 074-BEN A
GUID-A9BF9D69-2179-441C-A6C7-69EF0F55DD61 v3
23