ABB RELION 620 Series Technical Manual page 648

Section 4
Protection functions
4.5.3.4
642
subjected to service under low voltage conditions. PHPTUV includes a settable value
for the detection of undervoltage either in a single phase, two phases or three phases.
The function contains a blocking functionality. It is possible to block function outputs,
timer or the function itself, if desired.
Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of PHPTUV can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
GUID-21DCE3FD-C5A0-471A-AB93-DDAB4AE93116 V1 EN
Figure 328: Functional module diagram
Level detector
The fundamental frequency component of the measured three phase voltages are
compared phase-wise to the set Start value. If the measured value is lower than the set
value of the Start value setting, the level detector enables the phase selection logic
module. The Relative hysteresis setting can be used for preventing unnecessary
oscillations if the input signal slightly varies above or below the Start value setting.
After leaving the hysteresis area, the start condition has to be fulfilled again and it is
not sufficient for the signal to only return back to the hysteresis area.
The Voltage selection setting is used for selecting the phase-to-earth or phase-to-
phase voltages for protection.
For the voltage IDMT mode of operation, the used IDMT curve equations contain
discontinuity characteristics. The Curve Sat relative setting is used for preventing
unwanted operation.
For more detailed description on IDMT curves and usage of Curve Sat
Relative setting, see the
section in this manual.
The level detector contains a low-level blocking functionality for cases where one of
the measured voltages is below the desired level. This feature is useful when
unnecessary starts and operates are wanted to avoid during, for example, an
IDMT curves for under voltage protection
1MRS757644 F
620 series
Technical Manual