GE C70 Instruction Manual page 306

GROUPED ELEMENTS
the proportionality factor. Quality of balancing the bank with a given value of this setting can be viewed under
menu. An automatic setting procedure is available under the
VALUES
factor automatically.
NTRL CUR UNBALCE 1 STG1 PKP
through 4 in per-units (pu) of the nominal current of the ground current channel of the bank source. A value of 1 pu is the
nominal secondary current, or the nominal primary current, respectively, as configured under the bank source of this
function.
NTRL CUR UNBALCE 1 STG1 SLOPE
4. The slope setting is applied if the phase CTs are configured under the bank source. The magnitude of the zero-sequence
current is applied as a restraining signal. Typically few percent of slope is enough to ensure security of the function. The
factor compensating for the inherent bank unbalance zeroes out the operating signal under relatively balanced bank
currents. If the said currents contain a significant zero sequence component, the quality of compensation is lower, hence
the need for the restraint, and this slope setting.
NTRL CUR UNBALCE 1 STG1 DEL
per each stage of alarming/tripping. The timers use a common drop out time delay specified by the next setting.
NTRL CUR UNBALCE 1 DPO DELAY
stages apply individually configurable pickup delays, but use this common drop out delay.
NTRL CUR 1 BLK STG1
required. At minimum this function shall be blocked when the two banks are not paralleled. Note that when unblocked, the
function becomes operational after five cycles of intentional delay. High-set instantaneous protection on energization can
be provided by a separate instantaneous overcurrent function.
5
5-182
to
NTRL CUR UNBALCE 1 STG4 PKP
to
NTRL CUR UNBALCE 1 STG4 SLOPE
to
NTRL CUR UNBALCE 1 STG4 DEL
— This setting controls a drop out delay for the operate FlexLogic operands. Individual
to — These settings are used to block the function on a per stage basis when
NTRL CUR 1 BLK STG4
Figure 5-87: Neutral current unbalance logic
C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL
menu to calculate the compensating
COMMANDS
— These settings specify pickup thresholds for stages 1
— These settings specify the slopes for stages 1 through
— This setting specifies the pickup time delay, individually
CHAPTER 5: SETTINGS
ACTUAL