LT Load Flow: Unbalanced LV Load Flow Analysis for 400V/230V Three Phase and Single Phase Networks

What is LT Load Flow?

LT Load Flow is the analysis of voltage, current, power and losses in a low-tension (LT), also called low-voltage (LV), distribution network below the distribution transformer. Chief Consultant’s LT Load Flow software performs LV load flow analysis on LV 400V/230 V, 50 Hz networks, covering both three phase (400 V line-to-line) and single phase (230 V line-to-neutral) circuits, with the Red, Yellow and Blue phases and the neutral each modeled separately.

Because every phase is solved individually, LT Load Flow is an unbalanced load flow: it shows what a single balanced calculation hides, such as an overloaded phase, a weak single phase service or a voltage drop concentrated on one conductor. The solver is OpenDSS-compatible, and results are reported at system, section and phase level.

The global LV network problem that LT Load Flow solves

Every electricity utility in the world faces the same blind spot. Medium and high voltage networks are well modeled, but the LV network below the distribution transformer, where single phase homes, three phase commercial connections and rooftop solar all meet, is often documented only in fragments. Transformer loading and customer complaints drive decisions, while the electrical condition of individual LV spans and service connections stays invisible.

The result is a universal set of engineering problems in single phase and three phase LV networks:

• phase unbalance between single phase loads spread unevenly across R, Y and B;
• excessive voltage drop on long LV 400V/230 feeders and service drops;
• technical losses in LV conductors, transformers and service cables that are never measured directly;
• rooftop solar on single phase and three phase services causing reverse power flow and voltage rise;
• reinforcement decisions such as reconductoring, transformer upgrades and new transformers made without an LV load flow analysis.

LT Load Flow addresses these problems with one repeatable method. Wherever an LV network operates at 400V/230 V, three phase and single phase, the same survey-to-simulation workflow applies: capture the assets, build the phase-specific model, run the LV load flow analysis and test each proposed change before it reaches the field.

Who uses LT Load Flow

• Survey teams who capture transformers, poles, sections, conductors, single phase and three phase services and PV points.
• Operations engineers who check measured LV conditions against the LT Load Flow model.
• Planning engineers who test LV reinforcement options before committing to the field.
• DER engineers who review a solar applicant or the cumulative PV fleet on the LV network.
• Approving engineers who use the exported model and reports to document a decision.

Chapters 1 to 2: Survey the LV 400V/230 network and run the first LT Load Flow

An LV load flow analysis is only as good as its survey. The LT Load Flow study starts at the distribution transformer and follows the chain of LV main and branch, pole, service drop and meter, load or PV. The Chief Consultant LV Survey App records the from-node, conductor, phases, single phase and three phase connection quantities, loads and average service lengths, and shows GPS accuracy and span. Stable node identities, correct phase designation and verified lengths matter, because a wrongly phased or disconnected segment makes every later voltage and loss figure suspect.

On the web platform, the engineer uploads the CSV or XLSX survey export and selects one of two loading strategies. Strategy 1 uses an upstream kVA loading target. Strategy 2 uses synchronous Red, Yellow and Blue LV clamp-meter currents with optional measured power factor. A schematic (topology) or geographic (GPS) view is chosen, and Run Precision Analysis solves the three phase and single phase LV network.

Chapters 3 to 4: LT Load Flow results and section-level LV load flow analysis

The LT Load Flow dashboard summarizes one modeled transformer network: grid input in kVA, system efficiency, total technical losses in kW, and R, Y and B phase currents, plus a live topology render and asset counts. In the manual’s example the LV 400V/230 network shows 99.98 kVA input, 92.25% efficiency and 3.604 kW losses, with phase currents of 92.9 A, 182.2 A and 166.0 A. That gap between phases is an immediate sign of unbalance in the single phase load distribution.

The Export Engineering Data control produces an XLSX with a row for every LV line section: section ID, from and to nodes, length, cable type, and per-phase voltage, current, power factor, real and reactive input, losses and voltage drop. Engineers filter by worst voltage, current and loss, then trace each flagged section on the map. A DSS script export supports independent OpenDSS review of the LV load flow analysis.

Chapters 5 to 7: Solar impact on single phase and three phase LV networks

The Solar Value Analysis workspace runs LT Load Flow twice, once with existing rooftop PV and once with it removed, holding demand and topology constant so the change can be attributed to solar. In the worked example, removing PV raises transformer input from 99.98 to 174.16 kVA, raises real losses from 3.3983 to 7.8626 kW, and lowers minimum voltage from 0.922 to 0.878 pu.

The Connection Simulator tests a proposed PV system at a chosen node with its own rating, service cable type and route length. In the example, a 10 kW system at Node0 reduces input from 99.98 to 90.92 kVA, cuts losses by 0.3939 kW and improves minimum voltage from 0.922 to 0.932 pu. The manual stresses repeating each LV load flow analysis at both low-load, high-PV and peak-load, low-PV conditions before recommending an interconnection.

Chapters 8 to 15: The LT Load Flow Planning Suite

The Planning Suite opens from the Network Planning Tool. Proposed LV changes are staged in an Execution Stack on an interactive map and evaluated together with Run Simulation. The manual recommends starting from a named base case and adding one action at a time so cause and effect stay clear.

The suite also includes a phase configuration study, where a section can be re-phased and the resulting R, Y and B currents, losses and voltages compared, which is central to balancing single phase load across a three phase LV network.

Chapters 16 to 17: Export and comparison

After a solved proposal, the Download Modified Grid Report exports section-level LT Load Flow results for the changed network, to be kept beside the original base export. The Comparison Analysis Report opens a Synergy Analysis dialog where the engineer sets a load factor and a growth factor. The workbook then compares the existing base case, existing with growth, and each proposed transformer zone by rating, phase currents, line losses, voltage drop, annual energy loss and transformer loading.

The manual is careful about annual figures: a load factor is not automatically a loss factor, and growth changes I²R losses nonlinearly, so losses should be solved with LV load flow analysis rather than scaled.

Appendices: Method, benefits and field checklist

• Appendix A: the survey-to-network method, the two loading strategies, unbalanced LT Load Flow, scenario comparison discipline and incremental DER hosting studies.
• Appendix B: how to interpret technical and commercial benefits, and which design inputs each decision still needs.
• Appendix C: engineering definitions, pre-run data checks and a seven-point study completion checklist.
• Appendix D: support and next steps for utility teams.

LT Load Flow: frequently asked questions

What is LT Load Flow?

LT Load Flow is a load flow analysis of the low-tension distribution network below the transformer. It calculates voltage, current, power and losses for each phase and each section of an LV 400V/230 network.

Does LT Load Flow handle both single phase and three phase networks?

Yes. LT Load Flow models single phase and three phase connections in the same LV network, solving the R, Y and B phases and the neutral individually, so unbalance between single phase loads is visible.

What is LV load flow analysis used for?

LV load flow analysis is used to find voltage drop, phase unbalance and technical losses, to test new consumer and solar connections, and to compare reinforcement options such as reconductoring, transformer relocation, transformer upgrade or a second transformer.

Which network voltage does the manual cover?

The manual covers the 400/230 V, 50 Hz LV distribution system, meaning networks at or below 400 V, single phase and three phase, starting at the transformer secondary and ending at the consumer meter.

Can LT Load Flow assess rooftop solar on LV networks?

Yes. It compares a network with and without existing PV, and tests a proposed single phase or three phase PV connection at a chosen node, reporting the effect on transformer input, phase currents, voltage and losses.