GE UR Series C70, Инструкция по эксплуатации

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5-144 C70 Capacitor Bank Protection and Control System GE Multilin
5.6 GROUPED ELEMENTS 5 SETTINGS
5
• Undervoltage Protection: For voltage sensitive loads, such as induction motors, a drop in voltage increases the
drawn current which may 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 may be used to block the functioning of external devices by operat-
ing an output relay when the voltage falls below the specified voltage setting. The undervoltage feature may 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 may 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 oper-
ates 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 char-
acteristic.
The undervoltage delay setting defines the family of curves shown below.
(EQ 5.17)
where: T = operating time
D = undervoltage delay setting ( D = 0.00 operates instantaneously)
V = secondary voltage applied to the relay
V
pickup
= pickup level
Figure 5–66: INVERSE TIME UNDERVOLTAGE CURVES
At 0% of pickup, the operating time equals the
UNDERVOLTAGE DELAY
setting.
T
D
1
V
V
pickup
------------------ –
⎝ ⎠
⎛ ⎞
---------------------------------- =
842788A1.CDR
% of voltage pickup
T
ime
(seconds)
NOTE