Figure 220: 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.
4.4.5.5 Application
PSPTUV can be applied for protecting a power station used for embedded
generation when network faults like short circuits or phase-to-earth faults in a
transmission or a distribution line cause a potentially dangerous situations for the
power station. A network fault can be dangerous for the power station for various
1MRS758755 C
Protection functions
REC615 & RER615
Technical Manual
445
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