ABB RELION Series Technical Manual page 323

1MRS758755 A
REC615 and RER615
Technical Manual
for Uo-channel is given in the global setting Configuration/Analog inputs/Voltage
(Uo,VT). If "Calculated Uo" is selected, the voltage ratio is obtained from phase-
voltage channels given in the global setting Configuration/Analog inputs/Voltage
(3U,VT).
Example 1: Uo is measured from open-delta connected VTs (20/sqrt(3) kV : 100/
sqrt(3) V : 100/3 V). In this case, "Measured Uo" is selected. The nominal values for
residual voltage is obtained from VT ratios entered in Residual voltage Uo:
Configuration/Analog inputs/Voltage (Uo,VT): 11.547 kV :100 V. The residual
voltage start value of 1.0 × Un corresponds to 1.0 × 11.547 kV = 11.547 kV in the
primary.
Example 2: Uo is calculated from phase quantities. The phase VT-ratio is 20/sqrt(3)
kV : 100/sqrt(3) V. In this case, "Calculated Uo" is selected. The nominal values for
residual current and residual voltage are obtained from VT ratios entered in Residual
voltage Uo: Configuration/Analog inputs/Voltage (3U,VT): 20.000 kV : 100 V.
The residual voltage start value of 1.0 × Un corresponds to 1.0 × 20.000 kV = 20.000
kV in the primary.
If "Calculated Uo" is selected, the residual voltage nominal value is
always phase-to-phase voltage. Thus, the valid maximum setting for
residual voltage start value is 0.577 × Un. Calculated Uo requires that
all three phase-to-earth voltages are connected to the protection relay.
Uo cannot be calculated from the phase-to-phase voltages.
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.
Section 4
Protection functions
317