Phase Balancing Recommendation (Sezibwa)
Recommendation for re-assigning Sezibwa's single-phase customers across the three phases of the SRNE three-phase inverter, to fix a severe load imbalance. Uses meter IDs; the site operator maps these to customers.
Implementation status (2026-08-24)
The two minimal phase-balancing moves were completed on the morning of 2026-08-24:
- Completed: meter 003 moved from L1 to L2.
- Completed: meter 009 moved from L2 to L3.
- Outstanding (optional): meter 004 remains on L3; the optional move from L3 to L1 was not completed.
The expected post-change distribution is L1 5.9 / L2 7.3 / L3 7.6 kWh/day (28 / 35 / 37 percent), based on the historical load profile. Live measurements should be reviewed after sufficient post-change data has accumulated to confirm the achieved balance.
Baseline before the change (the problem)
Before the 2026-08-24 reconnections, meter_100's per-phase energy and per-customer voltage matching (all high-confidence), the current assignment and daily load is:
| Phase | Load (kWh/day) | Share | Customer meters (kWh/day) |
|---|---|---|---|
| L1 | 10.4 | 50 percent | 002 (5.7), 003 (4.5), 008 (0.1), 011 (0.1) |
| L2 | 5.1 | 25 percent | 009 (2.3), 007 (1.6), 010 (1.2) |
| L3 | 5.3 | 25 percent | 006 (2.7), 005 (2.1), 004 (0.5) |
Total site load about 20.7 kWh/day, so the ideal is about 6.9 kWh/day per phase. L1 carries half the site while L2 and L3 carry a quarter each.
Root cause: the two largest consumers, meter 002 (5.7) and meter 003 (4.5), are both on L1. Together they are 10.2 kWh/day, which already exceeds a balanced phase on its own.
Updated meter reference (after 2026-08-24 phase balancing)
This table records the wiring after the two completed moves. Initials only (no full names, per the customer-data rule). Modbus address is the meter's slave address; serial is the physical meter serial. Energy figures are historical averages used for the recommendation, not post-change measurements.
| Meter | Modbus addr | Serial | Customer (initials) | Previous phase | Current phase | Change status | Historical kWh/day |
|---|---|---|---|---|---|---|---|
| meter_002 | 2 | 200326019929 | NP | L1 | L1 | Unchanged | 5.7 |
| meter_003 | 3 | 200326020101 | KFH | L1 | L2 | Moved 2026-08-24 | 4.5 |
| meter_004 | 4 | 200326020199 | AB | L3 | L3 | Optional L3→L1 move outstanding | 0.5 |
| meter_005 | 5 | 200326020128 | KFH | L3 | L3 | Unchanged | 2.1 |
| meter_006 | 6 | 200326020209 | WS | L3 | L3 | Unchanged | 2.7 |
| meter_007 | 7 | 210302003356 | JN | L2 | L2 | Unchanged | 1.6 |
| meter_008 | 8 | 200326019807 | PO | L1 | L1 | Unchanged | 0.1 |
| meter_009 | 9 | 250902040373 | DK | L2 | L3 | Moved 2026-08-24 | 2.3 |
| meter_010 | 10 | 250902040216 | SN | L2 | L2 | Unchanged | 1.2 |
| meter_011 | 11 | 250902040311 | (unmapped) | L1 | L1 | Unchanged | 0.1 |
KFH holds two meters (003 and 005), now split across L2 and L3. Names are looked up live from the customer database by serial; the logical-to-service-ID map in the logger configuration had 009/010 transposed, so the physical serial remains authoritative.
Why phase balance matters
- Voltage quality. L1 carries roughly twice the current of L2/L3, so it has the largest voltage drop. Customers on L1 see the lowest voltage (dimmer lights, more appliance stress) while L2/L3 sit high. Balancing evens the voltage across customers.
- Backup capacity. The SRNE is a three-phase inverter with a per-phase output limit. During a grid outage (battery backup), an overloaded L1 can hit its per-phase limit and trip or brown out even though L2 and L3 have spare capacity and the total is within the inverter rating. Balancing maximises the backup the site can actually deliver.
- Losses. Imbalance drives neutral current and extra I2R losses in the distribution.
Note: this does not affect the battery arbitrage or solar economics. The three-phase inverter time-shifts the site's total energy across all phases, so the savings analysis is unchanged. Phase balancing is a separate power-quality and backup-reliability issue.
Implemented recommendation (minimal moves)
The following two reconnections were completed on 2026-08-24:
- Completed: meter 003 (4.5 kWh/day) moved from L1 to L2 — the key move, separating the two big loads (002 and 003).
- Completed: meter 009 (2.3 kWh/day) moved from L2 to L3 — rebalances L2 after taking on 003.
Expected result based on the historical load profile:
| Phase | Before | After 2 moves |
|---|---|---|
| L1 | 10.4 (50 percent) | 5.9 (28 percent) |
| L2 | 5.1 (25 percent) | 7.3 (35 percent) |
| L3 | 5.3 (25 percent) | 7.6 (37 percent) |
The max-minus-min spread drops from 5.3 to 1.7 kWh/day.
Outstanding optional third move for near-perfect balance: meter 004 (0.5) remains on L3. Moving it from L3 to L1 would give L1 6.4 / L2 7.3 / L3 7.1 (31 / 35 / 34 percent), spread 0.9.
The calculation
- Total daily energy about 20.7 kWh across three phases, so ideal is 20.7 / 3 = 6.9 kWh/day per phase.
- Current spread (heaviest minus lightest): 10.4 - 5.1 = 5.3 kWh/day.
- After the two moves: 7.6 - 5.9 = 1.7 kWh/day.
- After the optional third move: 7.3 - 6.4 = 0.9 kWh/day.
Loads are from the same meter data used across the Sezibwa economic analysis (meter_100 aggregate plus per-customer meters, over the March to August 2026 window). Note that meters 003 and 005 belong to the same customer (two service points); moving 003 to L2 leaves that customer with one meter on L2 and one on L3, which is fine.
Data provenance
Underlying data: the aggregate meter meter_100 plus the 10 customer sub-meters, over 2026-03-19 to 2026-08-10, from the modbus energy-logger archive (sources: pi-direct and nextcloud-import), i.e. the pre- and early-OpenEMS period. Load basis is a conservative 21.3 kWh/day.
Note (2026-08-20): the site has since migrated to OpenEMS, which is now the live source. OpenEMS-sourced daily figures from mid-August show inconsistencies (the aggregate roughly doubled exactly at the source switchover, and on some days the customer-meter sum exceeds the aggregate), so they are treated as a data-quality issue to resolve before use; this analysis stays on the validated archive. The baseline phase assignments reflect wiring observed up to about May 2026. The meter reference and implementation status above were updated for the reconnections completed on 2026-08-24; OpenEMS measurements should be used to verify the resulting live balance.