4.5.4.4 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of the negative-sequence overvoltage protection can be described
using a module diagram. All the modules in the diagram are explained in the next
sections.
GUID-0014077D-EEA8-4781-AAC7-AFDBAAF415F4 V1 EN
Figure 257: Functional module diagram. U
2
is used for representing negative
phase sequence voltage.
Level detector
The calculated negative-sequence voltage is compared to the set Start value setting.
If the value exceeds the set Start value, the level detector enables the timer.
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 overvoltage condition persists.
If the negative-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 functionality. The operation modes
are controlled by the BLOCK input and the global setting "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 IED 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. In the "Block all"
mode, the whole function is blocked and the timers are reset. In the "Block
Section 4 1YHT530004D05 D
Protection functions
486 615 series
Technical Manual
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