Current Elements - GE B90 Instruction Manual

GROUPED ELEMENTS
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
##  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

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.
5-152
setting corresponds to 1 pu. The minimum voltage setting (
PRODUCT SETUP  B90 FUNCTION  B90 FUNCTION
Figure 5-80: Undervoltage logic
 INSTANTANEOUS

 OVERCURRENT 1
 INSTANTANEOUS

 OVERCURRENT 24
 TIME

 OVERCURRENT 1
 TIME

 OVERCURRENT 24
SYSTEM SETUP  AC INPUTS  VOLTAGE BANK
UNDERVOLTAGE 1 MIN VOLTAGE
See page 5-157

See page 5-158

B90 LOW IMPEDANCE BUS DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS
)
is set to "Protection".
2
t standard