Voltage Drop & Length

Voltage drop and loop impedance along a feeder from the transformer through main and sub-distribution to the load, with the remaining budget, maximum cable length and smallest suitable cross-section for every section

Sample values, replace with your own feeder data

Voltage drop along the feeder

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Voltage drop Transformer Permitted voltage drop Loop impedance Zs Zs,max of the protective device

Supply Source Voltage V, line-to-line Frequency Hz Rated power Sr kVA Short-circuit voltage uk % Load losses Pk kW, datasheet Loop impedance at origin Ω, Zs upstream

Limits & calculation Max. voltage drop % from the origin Conductor temperature for voltage drop Count transformer voltage drop in the limit Disconnection time

Feeder sections · from the origin to the load

#	Section	System	Ib A	cos φ	Length m	Cross-section	Conductor	Parallel	Protective device	In A

Each section carries the current of everything downstream. Single-phase sections are rated against U0. The protective conductor is taken equal to the line conductor.

Supply

Feeder total

Reference limits

Assessment

Sections

#	Section	Cable	R′ Ω/km	X′ Ω/km	ΔU V	ΔU %	Σ ΔU %	Zs Ω	Zs,max Ω	Max. length ΔU m	Max. length Zs m	Min. cross-section	Status

Method: voltage drop per section ΔU = k × Ib × L × (R′ cos φ + X′ sin φ) / n with k = √3 for three-phase and 2 for single-phase sections and n parallel cables; percentages refer to U (three-phase) or U0 (single-phase) and are added along the feeder. R′ from the conductor resistance of IEC 60228 at the selected conductor temperature with skin and proximity effect, X′ from the conductor spacing of a multi-core cable. Transformer: Z = uk × U² / Sr, R = Pk × U² / Sr², voltage drop at the load ΔU = S / Sr × (uR cos φ + uX sin φ), short-circuit current Ik3 = c × U / (√3 × Z) with c = 1.05; the medium-voltage network is neglected. Loop impedance Zs = Zs at the origin plus 2 × L × |Z′| / n per section, added as magnitudes (on the safe side), at a conductor temperature of at least 70 °C. Disconnection per VDE 0100-410: Zs ≤ 0.95 × U0 / Ia with Ia = 5 / 10 / 20 × In for MCB B / C / D, typical values of gG fuses and Ii = 10 × Ir for circuit breakers. Maximum length and smallest cross-section of a section keep all other sections unchanged; for disconnection every downstream protective device is checked as well. Reference limits: VDE 0100-520 Annex G (3 % lighting / 5 % other uses from a public LV supply, 6 % / 8 % from an own transformer), DIN 18015-1 (3 % from the meter in residential buildings). Current-carrying capacity is not checked here; use Cable Sizing. Disclaimer: this tool is a planning aid. Results are not a substitute for design by a qualified electrical engineer and must be checked against the applicable standards (DIN VDE 0100-410, -520, DIN 18015-1, technical connection conditions of the network operator) and the manufacturer data before installation. oxinon.com accepts no liability for damage resulting from the use of these results.

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