GE C70 Instruction Manual

Also see for C70: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

CHAPTER 7: COMMANDS AND TARGETS COMMANDS MENUC70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL 7-37If the voltage differential function is disabled or blocked, then the auto-setting process is not functional and the 87V NOTRUNNING message displays in the second line.Application with automatic supervision of the automatically calculated factorsWhen the VOLTAGE DIF 1 AUTO SETTING command is switched to “Auto,” the process of calculating and applying thebalancing 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 functionexpires, 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 doesnot display the applied coefficients in “Auto” mode; rather, they are be viewed in the SETTINGS menu.If the supervisory conditions are not satisfied in the “Auto” mode within the time specified by the DEFAULT MESSAGETIMEOUT setting, the AUTO FAIL message displays and the 87V function starts running with the pre-existing settings for thebalancing 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 sensitivestages. Therefore, it is good practice to block the most sensitive stages on energization, manually adjust the factors toreduce the differential signal, and then enable the most sensitive stages.7.1.1.3 Neutral voltage unbalanceCOMMANDS  CAPACITOR BANK AUTO SETTING  NEUTRAL VOLTAGE UNBALANCE  NEUTRAL VOLTAGEUNBALANCE 1(3)Use the auto-setting feature when the capacitor bank is online and the 59NU function is enabled. For security reasons,consider applying less sensitive settings during the auto-setting process. Switching temporarily to a different setting groupwith less sensitive pickup thresholds is a method to provide the extra security.This feature can be used with a manual acceptance of the auto-calculated coefficients (the NTRL VOL UNBAL 1 AUTO SETcommand switched to “Manual”), or with an automatic acceptance of the calculated factors (the NTRL VOL UNBAL 1 AUTOSET command switched to “Auto”).The feature is used as follows.Manual supervision of automatically calculated factorsWhen the NTRL VOL UNBAL 1 AUTO SET command is switched to “Manual,” the auto-setting screens (one for each of the twofactors) display values that best balance the function and prompt for permission to apply the calculated value as a newsetting. When confirmed, the auto-selected value is applied to all setting groups having same source as the active groupduring auto-setting procedure. Both ratios (XA / XB and XA / XC) must be set correctly to clear the inherent bank unbalance.After consent to apply the calculated coefficient is received via the keypad, the "k =?.???? APPLIED" confirmation messageidisplays for the duration of the flash message time. The time-out period is intended for field staff to make note of thenewly applied coefficient. However, it is possible to immediately navigate from this screen. The new setting values can beviewed in the SETTINGS menu at any time.After the process finishes, it is recommended to disable the auto-setting feature. If not manually disabled, the featureautomatically 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 nominalfrequency and the magnitude of the positive-sequence current above 0.1 pu. If any of these conditions are violated, theSUPV FAIL message displays in the second line. NEUTRAL VOLTAGE UNBALANCE 1  NTRL VOL UNBAL 1AUTO SET: DisabledRange: Disabled, Manual, Auto XA/XB RATIO k=0.0000APPLY? NoRange: Yes, No XA/XC RATIO k=0.0000APPLY? NoRange: Yes, No