ABB REC670 Product Manual page 7

ABB
Bay control REC670
Pre-configured
Product version: 1.1
EF4PTOC can be set directional or non-
directional independently for each of the steps.
A second harmonic blocking can be set
individually for each step.
EF4PTOC can be used as main protection for
phase-to-earth faults.
EF4PTOC 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.
Directional operation can be combined
together with corresponding communication
logic in permissive or blocking teleprotection
scheme. Current reversal and weak-end
infeed functionality are available as well.
EF4PTOC can be configured to measure the
residual current from the three-phase current
inputs or the current from a separate current
input.
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.
Thermal overload protection, one time
constant LPTTR
The increasing utilizing of the power system
closer to the thermal limits has generated a
need of a thermal overload protection also
for power lines.
A thermal overload will often not be detected
by other protection functions and the
introduction of the thermal overload
1MRK 511 192-BEN B
protection can allow the protected circuit to
operate closer to the thermal limits.
The three-phase current measuring protection
2
has an I t characteristic with settable time
constant and a thermal memory.
An alarm level gives early warning to allow
operators to take action well before the line
is tripped.
Thermal overload protection, two time
constant TRPTTR
If the temperature of a power transformer/
generator reaches very high values the
equipment might be damaged. The insulation
within the transformer/generator will have
forced ageing. As a consequence of this the
risk of internal phase-to-phase or phase-to-
earth faults will increase. High temperature
will degrade the quality of the transformer/
generator oil.
The thermal overload protection estimates
the internal heat content of the transformer/
generator (temperature) continuously. This
estimation is made by using a thermal model
of the transformer/generator 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 trip of the protected transformer/
generator.
Breaker failure protection CCRBRF
Breaker failure protection (CCRBRF) ensures
fast back-up tripping of surrounding breakers
in case of own breaker failure to open.
CCRBRF can be current based, contact based,
or adaptive combination between these two
principles.
A current check with extremely short reset
time is used as check criteria to achieve a
high security against unnecessary operation.
A contact check criteria can be used where
the fault current through the breaker is small.
Issued: June 2010
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