ROV2PTOV has two voltage steps, where step 1 can be set as
inverse or definite time delayed. Step 2 is always definite time
delayed.
Overexcitation protection OEXPVPH
When the laminated core of a power transformer or generator is
subjected to a magnetic flux density beyond its design limits,
stray flux will flow into non-laminated components that are not
designed to carry flux. This will cause eddy currents to flow.
These eddy currents can cause excessive heating and severe
damage to insulation and adjacent parts in a relatively short
time. The function has settable inverse operating curves and
independent alarm stages.
8. Frequency protection
Underfrequency protection SAPTUF
Underfrequency occurs as a result of a lack of sufficient
generation in the network.
Underfrequency protection SAPTUF measures frequency with
high accuracy, and is used for load shedding systems, remedial
action schemes, gas turbine startup and so on. Separate
definite time delays are provided for operate and restore.
SAPTUF is provided with undervoltage blocking.
Overfrequency protection SAPTOF
Overfrequency protection function SAPTOF is applicable in all
situations, where reliable detection of high fundamental power
system frequency is needed.
Overfrequency occurs because of sudden load drops or shunt
faults in the power network. Close to the generating plant,
generator governor problems can also cause over frequency.
SAPTOF measures frequency with high accuracy, and is used
mainly for generation shedding and remedial action schemes. It
is also used as a frequency stage initiating load restoring. A
definite time delay is provided for operate.
SAPTOF is provided with an undervoltage blocking.
Rate-of-change frequency protection SAPFRC
The rate-of-change frequency protection function SAPFRC
gives an early indication of a main disturbance in the system.
SAPFRC measures frequency with high accuracy, and can be
used for generation shedding, load shedding and remedial
action schemes. SAPFRC can discriminate between a positive
or negative change of frequency. A definite time delay is
provided for operate.
SAPFRC is provided with an undervoltage blocking.
9. Secondary system supervision
Fuse failure supervision SDDRFUF
The aim of the fuse failure supervision function SDDRFUF is to
block voltage measuring functions at failures in the secondary
circuits between the voltage transformer and the IED in order to
avoid inadvertent operations that otherwise might occur.
The fuse failure supervision function basically has three different
detection methods, negative sequence and zero sequence
based detection and an additional delta voltage and delta
current detection.
The negative sequence detection is recommended for IEDs
used in isolated or high-impedance earthed networks. It is
based on the negative-sequence measuring quantities, a high
value of negative sequence voltage 3U
2
without the presence of
the negative-sequence current 3I
2
.
The zero sequence detection is recommended for IEDs used in
directly or low impedance earthed networks. It is based on the
zero sequence measuring quantities, a high value of zero
sequence voltage 3U
0
without the presence of the zero
sequence current 3I
0
.
For better adaptation to system requirements, an operation
mode setting has been introduced which makes it possible to
select the operating conditions for negative sequence and zero
sequence based function. The selection of different operation
modes makes it possible to choose different interaction
possibilities between the negative sequence and zero
sequence based detection.
A criterion based on delta current and delta voltage
measurements can be added to the fuse failure supervision
function in order to detect a three phase fuse failure, which in
practice is more associated with voltage transformer switching
during station operations.
Breaker close/trip circuit monitoring TCSSCBR
The trip circuit supervision function TCSSCBR is designed to
supervise the control circuit of the circuit breaker. The trip
circuit supervision generates a current of approximately 1 mA
through the supervised control circuit. The validity supervision
of a control circuit is provided for power output contacts T1, T2
and T3.
The trip circuit supervision operates after a settable definite
operating time and resets after a settable definite time when the
fault disappears.
10. Control
Apparatus control APC
The apparatus control function APC8 for up to 8 apparatuses is
used for control and supervision of circuit breakers,
disconnectors and earthing switches within a bay. Permission
Transformer protection RET650
1MRK 504 137-BEN B
Product version: 1.3
ABB
17
