4.5.7.4
Operation principle
The function can be enabled and disabled with the
Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of PSPTUV can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
Figure 348: Functional module diagram. U1 is used for representing positive phase
sequence voltage.
Level detector
The calculated positive-sequence voltage is compared to the set
Start value setting.
If the value drops below the set
Start value, the level detector enables the timer.
The
Relative hysteresis setting can be used for preventing unnecessary oscillations
if the input signal slightly varies from 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 to the hysteresis area.
Timer
Once activated, the timer activates the
START
output. The time characteristic is
according to DT. When the operation timer has reached the value set by
Operate
delay time, the
OPERATE
output is activated if the undervoltage condition persists.
If the positive-sequence voltage normalizes before the module operates, the reset
timer is activated. If the reset timer reaches the value set by
Reset delay time, the
operate timer resets and the
START
output is deactivated.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is
available in the monitored data view.
Blocking logic
There are three operation modes in the blocking function. The operation modes
are controlled by the
BLOCK
input and the global setting in Configuration >
System > Blocking mode which selects the blocking mode. The
BLOCK
input can be
controlled by a binary input, a horizontal communication input or an internal signal
of the protection relay's program. The influence of the
BLOCK
signal activation is
preselected with the global setting
Blocking mode.
The
Blocking mode setting has three blocking methods. In the "Freeze timers"
mode, the operation timer is frozen to the prevailing value, but the
OPERATE
output
is not deactivated when blocking is activated. In the "Block all" mode, the whole
function is blocked and the timers are reset. In the "Block OPERATE output" mode,
the function operates normally but the
OPERATE
output is not activated.
1MRS757644 H
Protection functions
620 series
Technical Manual
669
