IEC Electrical Engineering Calculators

Cable calculations

Current-carrying capacity, cross-section selection and voltage drop for low- and medium-voltage cables.

• #004 Cable Ampacity Calculator IEC 60287 · IEC 60228 · IEC 60949 Continuous current rating from the thermal model: conductor and dielectric losses, soil thermal resistivity, laying depth, grouping and a trench layout drawn to scale.
• #008 LV Cable Sizing Calculator, up to 1000 V IEC 60364-5-52 Cross-section selection against the Annex B reference methods A1 to G with the ambient, grouping and soil-resistivity correction factors applied to the tabulated value.
• #001 Voltage Drop Calculator, LV and MV to 33 kV IEC 60364-5-52 · IEC 60502-2 Multi-feeder, multi-segment voltage drop with conductor temperature, power factor and the permitted-drop check per circuit.
• #SDK Protective Conductor Sizing IEC 60364-5-54 Adiabatic check of the protective conductor against the fault energy the device lets through.

Short-circuit calculations

Fault currents to IEC 60909, split by voltage range so each tool carries the rules its range actually needs.

• #002 Short-Circuit Calculator — MV 1 to 33 kV IEC 60909-0 · IEC 60909-1 Positive, negative and zero sequence networks, several sources in parallel per busbar, and I″k3, I″k2, I″k1, peak current and κ at every busbar of the circuit.
• #012 Short-Circuit Calculator — LV up to 1 kV IEC 60909-0 · 100 V to 1 000 V One network table from feeder to fault, peak current by both method b and the equivalent-frequency method c, thermal equivalent current, the minimum currents protection has to see, and the device check. Validated against the worked example of IEC TR 60909-4 clause 3.

Protection and instrument transformers

• #015 LV Circuit Breaker Sizing and Verification — AC up to 1 kV IEC 60364-4-43:2023 · IEC 60947-2 Overload coordination, Icu and Ics, cable thermal withstand, minimum-fault clearing and making capacity, with breaker and compatible trip-unit selection from the common database.
• #006 Current Transformer Check IEC 61869-2 · IEEE C57.13 Secondary winding verification: connected burden, actual accuracy limit factor, knee-point voltage, transient dimensioning and the relay input withstand.

Transformers

• #010 Transformer Sizing and Selection IEC 60076 · IEC 60909 Rating selection against the load, the IEC 60076-5 impedance band, loss and efficiency check against the specification, and the short-circuit contribution the unit brings to the low-voltage side.

Motors and reactive power

• #009 Three-phase Motor Sizing, 0,12 to 1000 kW IEC 60034-30-1 · IEC 60072-1 Efficiency limits by class, pole count and frequency, site ambient by IEC 60034-1 Table 11, starting current, torque margin and the busbar voltage dip on starting.
• #005 Reactive Power Compensation Calculator IEC 60831 · IEC 61921 Capacitor bank sizing from load cases: required kvar, step bank, overcurrent duty by IEC 60831-1 clause 21, harmonic and overcompensation screening.

Earthing and lightning protection

• #003 Substation Grounding Grid Calculator IEEE Std 80-2013 Grid sizing where touch voltage decides rather than resistance: mesh and step voltage, conductor sizing, multi-grid layouts and a sketch editor.
• #013 Lightning Risk Assessment IEC 62305-2 Risk components R1 to R4 against the tolerable risk, from the structure, its contents, the incoming services and the local flash density.

Solar PV

• #011 PV String Calculator — modules per string IEC 62548 · IEC 61215 Maximum string voltage at the site minimum temperature against the system and inverter limits, minimum count against the MPPT window, and the string current against the inverter input.

Site design conditions

• #014 Engineering Climatology for a Site IEC 60721 · IEC 60826 · ERA5 · NASA POWER Design temperatures, humidity, wind and the IEC 60721 environmental classes for a coordinate, with extreme values by the Gumbel method of IEC 60826 Annex D.

Network models and reference data

The editors and libraries the calculators draw on.

• GRID Electrical network editor IEC 60909 · IEC 60364-5-52 Draw the single-line diagram once, set the parameters, and run the studies over the same model.
• DATA Equipment database CABLES · SWITCHGEAR · TRANSFORMERS Cable and overhead-line series with R′ and X′ per cross-section, transformers, machines and capacitor banks — the same records the calculators read.
• CAD Substations editor AIS 33 · 132 · 230 kV Substation layout in plan and section views.
• CAD Renewable stations editor PV · BESS Site layout for photovoltaic plants and battery storage.

Selection algorithms

• LV LV cable selection algorithm up to 1 kV · IEC 60364 Ampacity after every correction factor, coordination with the device, voltage drop by Annex G, k²S² and the earth-fault loop impedance — in the order a design review takes them.
• MV MV cable selection algorithm 1 to 36 kV · IEC 60502-2 The system earth-fault category that sets the rated voltage, the rating, and the screen checked separately from the conductor.
• HV HV cable system selection algorithm above 36 kV · IEC 60840 / 62067 Bonding settled before the rating, dielectric loss, soil drying-out, and the type-test evidence that has to exist behind the design.
• DC DC cable selection algorithm PV & battery · IEC 62548 Array voltage corrected to the lowest temperature, the Table 5 minimum currents, the +40 K module rise, and the fault current a battery can deliver.

How these calculations are built and checked

• CHECK Calculation validation 142 comparisons · 0 failing What every engine is compared against — the IEEE 80 Annex B earthing example, the worked 400 V network of IEC TR 60909-4 clause 3, IEC 60364-5-52 Annex E.52.2, the IEC 60034-30-1 efficiency tables, the IEC 62305-2 Annex E lightning cases.
• METHOD Calculation methodology CLAUSE FIRST The rules every engine follows: the clause before the code, tabulated values read from the standard, manufacturer data asked for rather than assumed, and the derivation printed with the result.
• IEC The standards behind the calculations 60909 · 60364-5-52 · 60287 · 60947-2 What each standard covers and which clause a calculation uses — the method in plain words, with the formula numbers for traceability.
• AUTHOR Who develops the calculations ELECTRICAL POWER ENGINEER The engineer behind the tools, and how to send a correction that lands.

Guides and worked examples

Every guide follows one calculation end to end on project numbers, then hands the case to the calculator.

• GUIDE Short-circuit, bus by bus: an 11/0.4 kV substation IEC 60909 Where the fault level comes from at each busbar, and why the minimum current is the one that decides whether protection operates.
• GUIDE Cable ampacity in a real trench IEC 60287 Why the tabulated rating does not apply to the trench as built, and what the thermal model does about it.
• GUIDE Voltage drop, end to end: a worked feeder IEC 60364 A feeder taken segment by segment to the permitted drop.
• GUIDE Earthing grid: touch voltage decides, not resistance IEEE 80 The criterion that actually governs a grounding grid, on a worked layout.
• ALL All guides, videos and presentations CONTENT LIBRARY The full library, including the engineering presentations.