ABB Relion 670 Series Product Manual page 33

Bay control REC670
Version 2.2
EF4PTOC also provides very fast and reliable faulty
phase identification for phase selective tripping and
subsequent reclosing during earth fault.
Four step directional negative phase sequence
overcurrent protection NS4PTOC
Four step directional negative phase sequence
overcurrent protection (NS4PTOC) has an inverse or
definite time delay independent for each step
separately.
All IEC and ANSI time delayed characteristics are
available together with an optional user defined
characteristic.
The directional function is voltage polarized.
NS4PTOC can be set directional or non-directional
independently for each of the steps.
NS4PTOC can be used as main protection for
unsymmetrical fault; phase-phase short circuits, phase-
phase-earth short circuits and single phase earth faults.
NS4PTOC can also be used to provide a system backup
for example, in the case of the primary protection being
out of service due to communication or voltage
transformer circuit failure.
Directional operation can be combined together with
corresponding communication logic in permissive or
blocking teleprotection scheme. The same logic as for
directional zero sequence current can be used. Current
reversal and weak-end infeed functionality are available.
Sensitive directional residual overcurrent and power
protection SDEPSDE
In isolated networks or in networks with high impedance
earthing, the earth fault current is significantly smaller
than the short circuit currents. In addition to this, the
magnitude of the fault current is almost independent on
the fault location in the network. The protection can be
selected to use either the residual current or residual
power component 3U0·3I0·cos j, for operating quantity
with maintained short circuit capacity. There is also
available one nondirectional 3I0 step and one 3U0
overvoltage tripping step.
No specific sensitive current input is needed. Sensitive
directional residual overcurrent and power protection
(SDEPSDE) can be set as low 0.25% of IBase.
Thermal overload protection, one time constant
LCPTTR/LFPTTR
The increasing utilization of the power system closer to
the thermal limits has generated a need of a thermal
overload protection for power lines.
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M12020-4 v14
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A thermal overload will often not be detected by other
protection functions and the introduction of the thermal
overload protection can allow the protected circuit to
operate closer to the thermal limits.
The three-phase current measuring protection has an I
characteristic with settable time constant and a thermal
memory. The temperature is displayed in either Celsius
or Fahrenheit, depending on whether the function used
is Thermal overload protection (LCPTTR) (Celsius) or
(LFPTTR) (Fahrenheit).
An alarm level gives early warning to allow operators to
take action well before the line is tripped.
Estimated time to trip before operation, and estimated
time to reclose after operation are presented.
Thermal overload protection, two time constants
TRPTTR
If a power transformer reaches very high temperatures
the equipment might be damaged. The insulation within
the transformer will experience forced ageing. As a
consequence of this the risk of internal phase-to-phase
or phase-to-earth faults will increase.
The thermal overload protection (TRPTTR) estimates the
internal heat content of the transformer (temperature)
continuously. This estimation is made by using a
thermal model of the transformer with two time
constants, which is based on current measurement.
Two warning levels are available. This enables actions in
the power system to be done before dangerous
temperatures are reached. If the temperature continues
to increase to the trip value, the protection initiates a
trip of the protected transformer.
The estimated time to trip before operation is
presented.
Breaker failure protection CCRBRF
Breaker failure protection (CCRBRF) ensures a fast
backup tripping of the surrounding breakers in case the
own breaker fails to open. CCRBRF measurement
criterion can be current based, CB position based or an
adaptive combination of these two conditions.
A current based check with extremely short reset time is
used as check criterion to achieve high security against
inadvertent operation.
CB position check criteria can be used where the fault
current through the breaker is small.
CCRBRF provides three different options to select how
t1 and t2 timers are run:
1MRK 511 404-BEN N
2
t
M13243-3 v12
M11550-6 v19
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