ABB RELION REX640 Technical Manual page 901

1MRS759142 F
Table 852: Special conditions
Condition
U3P connected to real measurements
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings.
For troubleshooting, check the contents of this chapter and also the preprocessing
blocks in this document. The configuration can be written to the protection relay
once the mismatch is corrected.
4.5.8.5 Operation principle
The function can be enabled and disabled with the
corresponding parameter values are "On" and "Off".
The operation of LVRTPTUV is described using a module diagram. All modules in the
diagram are explained in the next sections.
Figure 503: Functional module diagram
LVRT curve monitoring
LVRT curve monitoring starts with detection of undervoltage. Undervoltage
detection depends on
on fundamental frequency components.
Function uses phase-to-earth voltages when
Ph-to-E" or "Lowest Ph-to-E" and phase-to-phase voltages when
set to "Highest Ph-to-Ph" or "Lowest Ph-to-Ph".
When the
"Highest Ph-to-Ph" or "Lowest Ph-to-Ph", the measured three-phase voltages are
compared phase-wise to the set
than the set
of start phases , the START output is activated.
The setting options available for
2 of 3", and "Exactly 3 of 3", which are different from conventional setting options
available in other functions. For example,
3", any two voltages should drop below
for the START output to activate. Even if more than two voltages drop below
start value , START output is not activated.
REX640
Technical Manual
U_AB
U_BC
U3P
U_CA
U_1
BLOCK
Voltage selection setting. All selectable options are based
Voltage selection setting is set to "Highest Ph-to-E", "Lowest Ph-to-E",
Voltage start value setting in number of phases equal to that set Num
Description
The function requires that at least two volt-
age channels are connected as the the third
channel can then be derived. However, it is
recommended that all three voltage channels
are connected.
Operation setting. The
LVRT
curve
monitoring
Voltage selection is set to "Highest
Voltage start value . If the measured value is lower
Num of start phases are "Exactly 1 of 3", "Exactly
Num of start phases is set to "Exactly 2 of
Voltage start value within one cycle network
Protection functions
OPERATE
START
Voltage selection is
Voltage
901