ABB Relion REL650 Series Product Manual page 22

Line distance protection REL650
Version 2.2
Instantaneous residual overcurrent protection
EFPIOC
The Instantaneous residual overcurrent protection
(EFPIOC) has a low transient overreach and short tripping
times to allow the use for instantaneous earth-fault
protection, with the reach limited to less than the typical
eighty percent of the line at minimum source impedance.
EFPIOC is configured to measure the residual current from
the three-phase current inputs and can be configured to
measure the current from a separate current input.
Directional residual overcurrent protection, four
steps EF4PTOC
Directional residual overcurrent protection, four steps
(EF4PTOC) can be used as main protection for phase-to-
earth faults. It can also be used to provide a system back-
up, for example, in the case of the primary protection being
out of service due to communication or voltage transformer
circuit failure.
EF4PTOC has an inverse or definite time delay independent
for each step.
All IEC and ANSI time-delayed characteristics are available
together with an optional user-defined characteristic.
EF4PTOC can be set to be directional or non-directional
independently for each step.
IDir, UPol and IPol can be independently selected to be
either zero sequence or negative sequence.
A second harmonic blocking can be set individually for each
step.
Directional operation can be combined together with the
corresponding communication logic in permissive or
blocking teleprotection scheme. The current reversal and
weak-end infeed functionality are available as well.
The residual current can be calculated by summing the
three-phase currents or taking the input from the neutral CT.
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.
The directional function is voltage polarized.
NS4PTOC can be set directional or non-directional
independently for each of the steps.
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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
The increasing utilization of the power system closer to the
thermal limits has generated a need of a thermal overload
protection for power lines.
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
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