Arcteq Generator Commander, Instruction Manual

Page: 215 / 561

Events and registers
The underexcitation function (abbreviated "UEX" in event block names) generates events and registers
from the status changes in START, TRIP and BLOCKED. The user can select which event messages
are stored in the main event buffer: ON, OFF, or both.
The events triggered by the function are recorded with a time stamp and with process data values.
Table. 5.4.18 - 174. Event messages.
Event block name Event names
UEX1 Start ON
UEX1 Start OFF
UEX1 Trip ON
UEX1 Trip OFF
UEX1 Block ON
UEX1 Block OFF
The function registers its operation into the last twelve (12) time-stamped registers. The register of the
function records the ON event process data for START, TRIP or BLOCKED. The table below
presents the structure of the function's register content.
Table. 5.4.18 - 175. Register content.
Date and time Event
Pre-trigger
power (P&Q)
Fault power
(P&Q)
Pre-fault power
(P&Q)
Trip time
remaining
Used SG
dd.mm.yyyy
hh:mm:ss.mss
Event
name
Start/Trip -20ms
power
Start/Trip
power
Start -200ms
power
0 ms...1800s
Setting group
1...8 active
5.4.19 Underexcitation protection (X<; 40)
Synchronous machines require a certain amount of excitation to stay stable. If the excitation drops too
low a synchronous machine can drop out of step. One way for the relay to sense underexcitation is by
measuring the impedance. When the measured impedance enters the defined circle, the function will
trip.
The image below presents the basic principle of the function.
Genera Generattor Commander or Commander
Instruction manual
Version: 2.07
© Arcteq Relays Ltd
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