5-250
F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
GROUPED ELEMENTS
CHAPTER 5: SETTINGS
5
These protection elements can be used for a variety of applications, such as
•
Undervoltage protection
— For voltage sensitive loads, such as induction motors, a drop in voltage increases the
drawn current, which can cause dangerous overheating in the motor. The undervoltage protection feature can be
used to either cause a trip or generate an alarm when the voltage drops below a specified voltage setting for a
specified time delay.
•
Permissive functions
— The undervoltage feature can be used to block the functioning of external devices by
operating an output relay when the voltage falls below the specified voltage setting. The undervoltage feature can
also be used to block the functioning of other elements through the block feature of those elements.
•
Source transfer schemes
— In the event of an undervoltage, a transfer signal can be generated to transfer a load
from its normal source to a standby or emergency power source.
The undervoltage elements can be programmed to have a definite time delay characteristic. The definite time curve
operates when the voltage drops below the pickup level for a specified period of time. The time delay is adjustable from 0
to 600.00 seconds in steps of 0.01. The undervoltage elements can also be programmed to have an inverse time delay
characteristic.
The undervoltage delay setting defines the family of curves shown as follows.
Eq. 5-22
where
T = operating time
D = undervoltage delay setting (D = 0.00 operates instantaneously)
V = secondary voltage applied to the relay
V
pickup
= pickup level
NEUTRAL OV3
AUXILIARY UV1
AUXILIARY UV3
AUXILIARY OV1
AUXILIARY OV3
