Arcteq Generator Commander, Instruction Manual

Page: 225 / 561

Event block name Event names
SEF1 Start OFF
SEF1 Trip ON
SEF1 Trip OFF
SEF1 Block ON
SEF1 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. 5.4.20 - 189. Register content.
Date and time Event
Pre-trigger
voltage
Fault
voltage
Pre-fault
voltage
Trip time
remaining
Used SG
dd.mm.yyyy
hh:mm:ss.mss
Event
name
Start/Trip -20ms
voltage
Start/Trip
voltage
Start -200ms
voltage
0 ms...1800s
Setting group 1...8
active
5.4.21 Voltage-restrained overcurrent protection (Iv>; 51V)
Short-circuits that occur close to the generator decrease the fault current which in turn inhibits the
operation of a high-set overcurrent stage. The decreasing voltage caused by these faults can be used
to decrease the current pick-up level and thus to improve sensitivity. This voltage-restrained
overcurrent protection function can be used as an alternative for the underimpedance function for
more sensitive short-circuit detection in generator protection applications.
When there is a short-circuit near the generator, the voltage decreases which in this function's case
decreases the overcurrent's pick-up level according to set parameters. The function can work as
voltage-controlled overcurrent protection or as voltage-restrained overcurrent protection. When the set
parameter value Ux2 is greater than Ux1, the protection function works as voltage-restrained
overcurrent protection. In this case the overcurrent pick-up value increases as the voltage increases
between the set values Ux1 and Ux2. The protection function uses positive sequence voltage to define
the pick-up level at that moment.
When the set value of Ux1 is equal to Ux2, the function works as voltage-controlled overcurrent
protection. Now the overcurrent protection doesn’t operate until a fault reduces the voltage below a set
value, usually about 80 % of the normal. A fixed pick-up level of voltage-controlled overcurrent
protection is easier to coordinate with other relays. However, the voltage-restrained overcurrent
protection function is less prone to making unwanted operations on motor starting currents and system
swings.
Genera Generattor Commander or Commander
Instruction manual
Version: 2.07
© Arcteq Relays Ltd
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