ABB RED650 - Page 208

setting) the function will give a trip after a set delay tSOTF. This delay is normally
set to a short time (default 200 ms).
The under-time logic acts as a circuit breaker pole-discordance protection, but it is
only active immediately after breaker switching. The under-time logic can only be
used in solidly or low impedance grounded systems.
The under-time logic always uses the start signal from the step 4. The under-time
logic will normally be set to operate for a lower current level than the SOTF
function. The under-time logic can also be blocked by the 2
nd
harmonic restraint
feature. This enables high sensitivity even if power transformer inrush currents can
occur at breaker closing. This logic is typically used to detect asymmetry of CB
poles immediately after switching of the circuit breaker. The under-time logic is
activated either from change in circuit breaker position or from circuit breaker
close and open command pulses. This selection is done by setting parameter
ActUnderTime. In case of a start from step 4 this logic will give a trip after a set
delay tUnderTime. This delay is normally set to a relatively short time (default 300
ms).
UNDERTIME
HarmResSOFT
ActUnderTime
t4U
AND
t
tUnderTime
OR
Open
Closed
Close command
ActivationSOTF
t4U
StepForSOTF
STIN2
STIN3
AND
t
tSOTF
AND
BLOCK
2nd Harmonic
AND
Open
Close
Close command
STIN4
SOTF
SOTF or
UnderTime
TRIP
OFF
OR
UnderTime
SOTF
SOTF
IEC06000643-5-en.vsdx
IEC06000643 V5 EN-US
Figure 89: Simplified logic diagram for SOTF and under-time features
M13941-3 v6
Simplified logic diagram for the complete EF4PTOC function is shown in Figure
90:
Section 8 1MRK 505 394-UEN A
Current protection
202 Line differential protection RED650 2.2 IEC
Technical manual