        # Document Library

Conclusion for Unbalance Formulas

Delta connected banks This formula is for losing units between phase A-B. The "AMPS" are in the affected leg. If a unit is removed from A-C, or B-C, the formula can be modified to address these situations.

Ground WYE Connected Banks

For single series group the formulas are as follows:

Neutral to Ground Current: Voltage on Remaining Units: If VT = V, %VR will always be 100%.

For Multiple Series Groups the Formulas are as Follows

Neutral to Ground Current: Voltage on Remaining Units: Ungrounded WYE Connected Banks (Neutral to Ground Voltage Detection)

For single series group the formulas are as follows:

The Voltage on the Remaining Capacitors in the Affected Phase are: The Voltage in the Neutral are: The Percentage of Voltage Shift in the Affected Leg are: For MULTIPLE Series Groups the Formulas are as Follows:

The voltage on the remaining capacitors in the affected phase is: The Voltage Shift Due to Removal of F Units in One Series Section: The Neutral Shift When One Complete Series Section is Shorted: Ungrounded double (split) WYE with neutral CT

The calculations for split applications with even number of units in each WYE sections are as follows:

The amount of current flowing between neutrals of the two WYES sections. Current transformer is assumed to have zero impedance. Percent of rated total bank current The Voltage Remaining on Units in One Series Section with F Units Removed: Permissible number of units that can be removed from one series section to result in a given %VR on remaining units in that section. The Calculations for Split Applications with Uneven WYE Sections are as Follows, One Series Group

The Change in Voltage in the Phase with Units Removed: The Voltage on this Phase Will Be (Assume Units Removed From Phase "A"): The Change in Current in this Phase Will Be The New Current in this Leg is: (A phase KVAR will be the original KVAR)

To Determine the New Voltage on Phases "B" and "C": The Effective KVAR for These Phases Will Be The Current in These Phase Will Be The Neutral Current in the WYE Section is You will need to calculate the neutral current in the WYE section without any units removed.

The Phase A Voltage in the Section is the Same as Above: and The Current in this Phase Will Be Higher than the Affected WYE Section: The Current in These Phase Will Be The voltage on B and C phase will be the same as the affected section and the effective KVAR will be lower. The New Current Will Be The Neutral Current in the WYE Section is (normal WYE section-no units removed)

The Current on the Neutral Between the WYE Sections Will Be  LEGEND Vt Applied line to neutral voltage. V Rated voltage of the capacitor unit VR Voltage on remaining units in affected group with F units removed. △V change in phase to neutral voltage VB’N’ New voltage on B & C phases INC Current between neutrals of two banks halves. △I Current change in affected phase (A). IA’N’ New current in affected phase (A) IB’N’ New current in phase B & C. IN' (Unit removed) neutral current in WYE section with unit removed. IN’ (Normal section) neutral current in WYE section with unit removed. KVAREFF Effective KVAR KVARRATED rated KVAR S Number of series sections per phase. N Number of parallel units in one series section. F Number of units removed from one series section.