Operation Principle - ABB RELION REX640 Technical Manual

Section 4
Protection functions
4.2.3.5
446
in this document. The configuration can be written to the protection relay once the
mismatch is corrected.

Operation principle

The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of INTRPTEF can be described with a module diagram. All the
modules in the diagram are explained in the next sections.
Io
IRES
Transient
Uo
detector
URES
Level
detector
BLOCK
GUID-706FD637-16D1-4A36-B5EB-4B1B992B2BE4 V1 EN
Figure 240: Functional module diagram
Level detector
The Level detector module is used only when selected Operation mode is "Transient
EF". The module compares the measured residual voltage to the set Voltage start
value. If the measured value exceeds the set Voltage start value, the module reports the
exceeding of the value to the Fault indication logic.
Transient detector
The Transient detector module is used for detecting transients in the residual current
and residual voltage signals.
The transient detection is supervised with a settable current threshold. With a special
filtering technique, the setting Min operate current is based on the fundamental
frequency current. This setting should be set based on the value of the parallel resistor
of the coil, with security margin. For example, if the resistive current of the parallel
resistor is 10 A, then a value of 0.7×10 A = 7 A could be used. The same setting is also
applicable in case the coil is disconnected and the network becomes unearthed.
Generally, a smaller value should be used and it must never exceed the value of the
parallel resistor in order to allow operation of the faulted feeder.
Fault indication logic
Depending on the set Operation mode, INTRPTEF has two independent modes for
detecting earth faults. The "Transient EF" mode is intended to detect all kinds of earth
faults. The "Intermittent EF" mode is dedicated for detecting intermittent earth faults
in cable networks.
Timer 1
Fault
t
indication
logic
Timer 2
1MRS759142 C
OPERATE
START
BLK_EF
REX640
Technical Manual