GE C70 Instruction Manual page 408

7.1 COMMANDS
d) PHASE CURRENT UNBALANCE

PATH: COMMANDS CAPACITOR BANK AUTO SETTINGS
 PHASE CURRENT
 UNBALANCE 1
The auto-setting feature shall be used when the capacitor bank is on-line and the 60P function is enabled. For security rea-
sons, it may be necessary to apply less sensitive settings during the auto-setting process. Switching temporarily to an alter-
nate setting group with less sensitive pickup thresholds is a method to provide for this extra security.
The feature can be used with by manual accepting the auto-calculated coefficients (the
command switched to "Manual") or by automatic acceptance of the calculated factors (the
command switched to "Auto").
The feature is used as follows.
Application with Manual Supervision of the Automatically Calculated Factors:
When the
CUR UNBALACE 1 AUTO SETTINGS
phase) display values that best balance 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 is applied to all setting groups having same source as
active group during the auto-setting procedure. Note that the balancing factors can be either positive or negative, depend-
ing on which of the two banks has a lower impedance, and on the polarity of the differential CTs connected to the relay.
After user consent to apply the calculated coefficient is received, the
for the duration of the flash message time. The timeout period is meant 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 is finished, it is recommended to disable the auto-setting feature. If not 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 frequency deviation from the nominal and
the magnitude of the phase currents above 0.25 pu. If any of these conditions are violated, the
7
played in the second line.
If the phase unbalance function is disabled or blocked, the auto-setting process is not functional and the
message is displayed in the second line.
Application with Automatic Supervision of the Automatically Calculated Factors:
When the
CUR UNBALACE 1 AUTO SETTINGS
balancing coefficients is fully automatic. Typical applications require setting this function to "Auto" with the bank de-ener-
gized, then subsequently energizing the capacitor bank. If the function is set to "Auto", it expects to read valid input signals
as a result of bank energization within the flash message duration time to calculate and apply factors. Otherwise, the value
is switched backed to "Disabled". When the bank is energized and the five-cycle timer of the 60P function expires, the bal-
ancing coefficients are calculated and automatically applied. After the new balancing factors are applied, the auto-setting
function switches "Auto" to "Disabled" and the 60P element becomes operational. When in the "Auto" mode, the automatic
confirmation command is executed immediately after the balancing values are available. The C70 does not display the
applied coefficients in "Auto" mode; rather, they can be viewed in the
If the supervisory conditions are not satisfied in the "Auto" mode within time defined by the
ting, the message is displayed and the 60P function starts running with the pre-existing settings for the balanc-
AUTO FAIL
ing factors.
7-4
CUR UNBALACE 1 AUTO
SETTINGS: Disabled
CUR UNB 1A k=0.0000
MESSAGE
APPLY IN PHS A? No
CUR UNB 1A k=0.0000
MESSAGE
APPLY IN PHS B? No
CUR UNB 1A k=0.0000
MESSAGE
APPLY IN PHS C? No
command is switched to "Manual", the auto-setting screens (one for each
command is switched to "Manual", the process of calculating and applying the
C70 Capacitor Bank Protection and Control System

PHASE CURRENT UNBALANCE
Range: Disabled, Manual, Auto
Range: Yes, No
Range: Yes, No
Range: Yes, No
k =?.???? APPLIED
menu.
SETTINGS
7 COMMANDS AND TARGETS

PHASE CURRENT UNBALANCE 1(3)
CUR UNBALACE 1 AUTO SETTINGS
CUR UNBALACE 1 AUTO SETTINGS
confirmation message is displayed
message is dis-
SUPV FAIL
60P NOT RUNNING
DEFAULT MESSAGE TIMEOUT
GE Multilin
set-