Maximum Value of Voltage Drop IEC 60364-5-52The voltage drop between the origin of an installation and any load point should not be greater than the values in
Table G.52.1, expressed with respect to the value of the nominal voltage of the installation.
Table G.52.1 – Voltage Drop| Type of Installation | Lighting (%) | Other Uses (%) |
| A – Low voltage installations supplied directly from a public low voltage distribution system | 3 | 5 |
| B – Low voltage installations supplied from private LV supply | 6 | 8 |
- As far as possible, it is recommended that voltage drop within the final circuits
does not exceed those indicated in installation
Type A.
- When the
main wiring systems of the installations are
longer than 100 m, these voltage drops
may be increased by
0.005% per meter of wiring system beyond
100 m, without this supplement being greater than
0.5%.
- Voltage drop is determined from the demand by the current-using equipment, applying diversity factors where applicable, from the values of the
design current of the circuits.
NOTE 1: A greater voltage drop may be accepted-
For motor starting periods.
-
For other equipment with high inrush current.
Provided that in both cases, it is ensured that the voltage variations remain within the limits specified in the relevant equipment standard.NOTE 2: The following temporary conditions are excluded- Voltage transients.
- Voltage variation due to abnormal operation.
Voltage Drop Calculation Formulau = b * ((P1 * L * cos(φ) + λ * L * sin(φ)) / S) * I_B
Where:-
u = Voltage drop (in volts).
-
b = Coefficient,
1 for three-phase circuits,
2 for single-phase circuits.
-
P₁ = Resistivity of conductors in normal service,
1.25 times the resistivity at
20°C:
-
0.0225 Ω mm²/m for copper.
-
0.036 Ω mm²/m for aluminum.
-
L = Straight length of the wiring system (in meters).
-
S = Cross-sectional area of conductors (in mm²).
-
cos φ = Power factor (default
0.8, if not specified).
-
λ = Reactance per unit length of conductors,
0.08 mΩ/m in absence of other data.
-
I_B = Design current (in amps).
The
voltage drop percentage can be calculated as:
Δu = 100 * (u / U0)
where:
-
U₀ = Voltage between
line and neutral (in volts).
NOTE 4:- In
extra-low voltage circuits, it is
not necessary to fulfill the voltage drop limits of
Table G.1 for
uses other than lighting (e.g.,
bell, control, door opening), provided that a check ensures that the equipment is
operating correctly.