GE C70 Instruction Manual page 421

7 COMMANDS AND TARGETS
c) NEUTRAL VOLTAGE UNBALANCE

PATH: COMMANDS CAPACITOR BANK AUTO...
 NEUTRAL VOLTAGE
 UNBALANCE 1
MESSAGE
MESSAGE
The auto-setting feature shall be used when the capacitor bank is on-line and the 59NU function is enabled. For security
reasons, it may be necessary to consider applying less sensitive settings during the auto-setting process. Switching tempo-
rarily to a different setting group with less sensitive pickup thresholds is a method to provide for this extra security.
This feature can be used with a manual acceptance of the auto-calculated coefficients (the
command switched to "Manual"), or with an automatic acceptance of the calculated factors (the
command switched to "Auto").
SET
The feature is used as follows.
MANUAL SUPERVISION OF AUTOMATICALLY CALCULATED FACTORS:
When the
NTRL VOL UNBAL 1 AUTO SET
factors) display values that best balance the function and prompt for permission to apply the calculated value as a new set-
ting. When confirmed, the auto-selected value is applied to all setting groups having same source as the active group dur-
ing auto-setting procedure. Both ratios (X
After consent to apply the calculated coefficient is received via the keypad, the
displayed for the duration of the flash message time. The time-out period is intended for field staff to make a note of the
newly applied coefficient. However, it is possible to immediately navigate from this screen. The new setting values can be
viewed in the menu at any time.
SETTING
After the process if finished, it is recommended to disable the auto-setting feature. If not manually disabled, the feature
automatically disables itself when user-initiated front panel interface activity ceases and the C70 display is dimmed.
Certain security conditions are checked during the auto-setting process, such as the frequency deviation from the nominal
frequency and the magnitude of the positive-sequence current above 0.1 pu. If any of these conditions are violated, the
message is displayed in the second line.
SUPV FAIL
If the neutral voltage unbalance function is disabled or blocked, the auto-setting process is not functional and the
message is displayed in the second line.
RUNNING
AUTOMATIC SUPERVISION OF AUTOMATICALLY CALCULATED FACTORS:
When the
NTRL VOL UNBAL 1 AUTO SET
ing coefficients is fully automatic. Typical applications require setting this function to "Auto" with the bank de-energized,
then energizing the capacitor bank. After the function is set to "Auto", it expects to read valid input signals as a result of
bank energization within the display flash message time duration to calculate and apply factors; otherwise, the function is
returned to "Disabled". When the bank is energized and the five-cycle timer of the 59NU function expires, the balancing
coefficients are calculated and automatically applied. When the new balancing factors are applied, the function switches
automatically from "Auto" to "Disabled" and the 59NU function becomes operational. In essence, the when in the "Auto"
mode, the confirmation command is automatically executed immediately after the balancing values are available. The C70
does not display the applied coefficients in the "Auto" mode; rather, they are be viewed in the
When the supervisory conditions are not satisfied in "Auto" mode, the
tion starts running with the pre-existing settings for the balancing factors.
GE Multilin

NEUTRAL VOLTAGE UNBALANCE
NTRL VOL UNBAL 1
AUTO SET: Disabled
XA/XB RATIO k=0.0000
APPLY? No
XA/XC RATIO k=0.0000
APPLY? No
command is switched to "Manual", the auto-setting screens (one for each of the two
/ X and X / X ) must be set correctly to clear the inherent bank unbalance.
A B A C
command is switched to "Auto", the process of calculating and applying the balanc-
C70 Capacitor Bank Protection and Control System

NEUTRAL VOLTAGE UNBALANCE 1(3)
Range: Disabled, Manual, Auto
Range: Yes, No
Range: Yes, No
NTRL VOL UNBAL 1 AUTO SET
NTRL VOL UNBAL 1 AUTO
confirmation message is
k =?.???? APPLIED
SETTINGS
message is displayed and the 59NU func-
AUTO FAIL
7.1 COMMANDS
59NU NOT
7
menu.
7-3