Current Elements - GE B90 Instruction Manual

CHAPTER 5: SETTINGS
Application of the Undervoltage element is beneficial during CT trouble conditions. A low-voltage check prevents
maloperation of the main protection until the CT trouble element (differential current alarm) operates. The CT Trouble
element is user-configurable to block selected protection functions indefinitely. Voltage supervision alone does not
guarantee security because a CT trouble may be followed by an external fault causing a low-voltage condition.
Voltage pickup is set in per-unit values. The nominal voltage as entered in the
setting corresponds to 1 pu. The minimum voltage setting (
##  VT ## SECONDARY
specifies the minimum voltage required for element operation. This setting discriminates between undervoltage conditions
for energized and de-energized circuits. If the element is used for low-voltage supervision, set this value to 0.004.
The Undervoltage element is enabled only when
One element is available per each voltage input of the relay.

5.6.6 Current elements

5.6.6.1 Menu
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  CURRENT ELEMENTS
 CURRENT ELEMENTS

5.6.6.2 Inverse TOC curve characteristics
The inverse time overcurrent curves used by the time overcurrent elements are the IEEE, IEC, GE Type IAC, and I
curve shapes. This allows for simplified coordination with downstream devices.
B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
PRODUCT SETUP  B90 FUNCTION  B90 FUNCTION
Figure 5-90: Undervoltage logic
 INSTANTANEOUS

 OVERCURRENT 1

 INSTANTANEOUS

 OVERCURRENT 24
 TIME

 OVERCURRENT 1

 TIME

 OVERCURRENT 24
GROUPED ELEMENTS
SYSTEM SETUP  AC INPUTS  VOLTAGE BANK
UNDERVOLTAGE 1 MIN VOLTAGE
is set to "Protection".
See page 5-174
See page 5-175
)
5
2
t standard
5-169