GE C70 Instruction Manual page 406

7.1 COMMANDS
b) VOLTAGE DIFFERENTIAL

PATH: COMMANDS CAPACITOR BANK AUTO SETTING
 VOLTAGE
 DIFFERENTIAL 1
The automatic setting feature shall be used when the capacitor bank is on-line and the 87V function is enabled. For security
reasons one may consider applying less sensitive settings during the auto-setting process. Switching temporarily to a differ-
ent setting group with less sensitive pickup thresholds is a way to provide for the extra security.
The 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").
TING
The feature is used as follows.
Application with Manual Supervision of the Automatically Calculated Factors:
When the
VOLTAGE DIF 1 AUTO SETTING
display the values that balance best the function in a given phase and prompt for permission to apply the calculated value
as a new setting. When confirmed, the auto-selected value gets applied to all setting groups configured with the same
source as the active group during the auto-setting procedure.
After consent to apply the calculated coefficient is received, the
the duration of the flash message time in the second line of the screen. The time-out period is provided for the field staff to
make a note of the newly applied coefficient. However, it is possible to navigate from this screen immediately. The new set-
ting values can be viewed under the setting menu at any time.
After the process if finished, it is recommended to disable the auto-setting feature. If not disabled by the user, the feature
disables itself when user-initiated front panel interface activity ceases and the C70 display dims itself.
Certain security conditions are checked during the auto-setting process. This includes deviation from the nominal fre-
quency and verifying that the magnitudes of all three bus voltages are between 0.85 and 1.15 pu. If these conditions are
violated. the
SUPV FAIL
7
If the voltage differential function is disabled or blocked, then the auto-setting process is not functional and the
message is displayed in the second line.
RUNNING
Application with Automatic Supervision of the Automatically Calculated Factors:
When the
VOLTAGE DIF 1 AUTO SETTING
ing coefficients is fully automatic. Typical applications require setting this function to "Auto" with the bank de-energized,
then energizing the capacitor bank. When the bank is energized and the five-cycle timer of the 87V function expires, the
balancing coefficients are calculated and automatically applied. After the new balancing factors are applied, the function
switches automatically from "Auto" to "Disabled" and 87V becomes operational. In essence, when in the "Auto" mode, the
user confirmation is processed immediately after the balancing values become available. The C70 does not display the
applied coefficients in "Auto" mode; rather, they are be viewed under in the
If the supervisory conditions are not satisfied in the "Auto" mode within the time specified by the
setting, the
AUTO FAIL
ancing factors.
The advantage of automatically calculating factors is that the bank is immediately protected after energization. However,
due to energization inrush and distortion of voltages, the factors may not be accurate enough for the most sensitive stages.
Therefore, it is a good practice to block the most sensitive stages on energization, manually adjust the factors to reduce the
differential signal, and then enable the most sensitive stages.
7-2
VOLTAGE DIF 1 AUTO
SETTING: Disabled
V DIF 1A k=####.####
MESSAGE
APPLY IN PHS A? No
V DIF 1A k=####.####
MESSAGE
APPLY IN PHS B? No
V DIF 1A k=####.####
MESSAGE
APPLY IN PHS C? No
command is switched to "Manual", the auto-setting screens, one for each phase,
message is displayed in the second line.
command is switched to "Auto", the process of calculating and applying the balanc-
message is displayed and the 87V function starts running with the pre-existing settings for the bal-
C70 Capacitor Bank Protection and Control System
 
VOLTAGE DIFFERENTIAL VOLTAGE DIFFERENTIAL 1(3)
Range: Disabled, Manual, Auto
Range: Yes, No
Range: Yes, No
Range: Yes, No
k =?.???? APPLIED
SETTINGS
7 COMMANDS AND TARGETS
VOLTAGE DIF 1 AUTO SETTING
VOLTAGE DIF 1 AUTO SET-
confirmation message is displayed for
menu.
DEFAULT MESSAGE TIMEOUT
GE Multilin
87V NOT