EMC — separation of power and data cables (§444)

When power cables and sensitive data/signal cables (network, BMS, sensor wiring) run in the same cable route or the same cable tray, the magnetic field of the power cable can induce a disturbing voltage in the data cable — especially with high currents, switching loads (VFDs, switch-mode power supplies) or long parallel runs. §444 of NEN 1010 addresses measures against this electromagnetic interference.

Normative, no longer merely informative

In an earlier edition of the standard, the EMC provisions in §444 were largely informative (recommendations). In the current NEN 1010, the core measures from §444 are normative — that is, mandatory to apply, not optional.

§444.6 — separating circuits

§444.6 gives concrete separation distances between power cables and data cables, depending on the degree of shielding provided by the cable enclosure itself:

A closed metal enclosure reduces so-called common-mode coupling the most — hence a closed metal cable tray can reduce the separation distance to zero, while cables in open air without any shielding require the greatest distance. See also the cable tray systems guide for the mechanical/electrical requirements on the tray system itself.

Note: the table values apply to the generic situation of §444.6; for specific combinations (for example high-frequency VFD cables next to highly sensitive measurement signals) additional shielding or a greater distance may be required — when in doubt, consult the manufacturer's documentation of the connected equipment.

Practical relevance

In an industrial hall or horticultural business with climate computers, sensor wiring and variable frequency drives (VFDs) for pumps/fans, the risk of EMC interference is real: a disturbing voltage on a sensor cable can cause a climate computer to process incorrect measurements, with consequences for, for example, growing conditions. Combining power and data cables in a single closed metal cable tray is in practice often the most space-efficient solution that also complies with §444.6.

Common mistakes

1. Running power and data cables in the same open cable tray without respecting the separation distance from §444.6, particularly with VFD cables (high-frequency switching harmonics) next to sensitive signal wiring.
2. Assuming that any cable tray provides sufficient shielding — only a closed, conductive metal enclosure (with proper bonding) actually reduces the required distance to 0 mm.
3. Treating EMC measures as optional — the core provisions of §444 are normative in the current standard, not merely advisory.

Related

• Cable tray systems — cable trays and cable ladders
• Harmonics & THD