The Result
Your Router understands that the data packets arrived corrupted and requests that they be sent again. This causes "Packet Loss", extremely high Ping (Lag in games) and inexplicable disconnections.
Separation of Weak & Strong Currents: Safety distances and rules (EMI/RFI) to keep current from interfering with your network
Once you've chosen the right cable (eg Cat6a UTP) for your network, it's time to install. In construction, the logic of "convenience" often prevails: "Since the electrician has already dug the groove in the wall for the power socket cable, let's throw the internet cable into the same groove and be done with it."
This practice is one of the biggest (and most common) crimes in structured cabling. Mains cables (Weak Currents) and 230V voltage cables (Strong Currents) are "sworn enemies".
As engineers, we must separate these two worlds. Let's see why electricity can "kill" your internet speed, what are the minimum safety distances required by standards, and what do we do when cables are forced to cross.
1. The Invisible Enemy: Electromagnetic Interference (EMI)
To understand the rule, we need to look at some basic physics. When alternating current (AC 230V) flows through a wire (eg when you turn on the washing machine or vacuum cleaner), it creates an invisible electromagnetic field around it.
On the other hand, your network's UTP cable carries the "0s" and "1s" of the Internet using minimal voltage (a few millivolts).
If the two cables run parallel and very close to each other, the strong magnetic field of the current "invades" the network cable, altering the sensitive electrical data signals. This phenomenon is called Electromagnetic Interference (EMI).
2. The Basic Rule: Parallel Routes
How far apart should they be? The distance depends on the way the cables are routed (whether they are "bare", in plastic pipes or in metal racks).
Ban on the same pipe
It is expressly forbidden (and by the electrical safety regulations / ELOT HD 384) to pass a mains cable inside the same plastic tube (spiral) as a 230V cable. It's not just an internet issue, but a risk of fire or electric shock if the insulation melts.
The Safety Distance (Without Separators)
If the cables run parallel through a wall, in simple plastic pipes, the "golden rule" of international standards (such as EN 50174) mandates a minimum distance of 20 centimeters (20 cm) between them.
Cable Trays
In commercial spaces or suspended ceilings where metal gratings are used, the distance may be reduced to 5 centimeters (5 cm), only if there is a continuous, grounded metal divider (divider) between them.
3. The 90 Degree Rule (Vertical Crosses)
Many times, it is practically impossible not to meet the wires. For example, the network cable that comes down from the ceiling must pass over the power line that runs horizontally on the baseboard.
This is where The Rule of 90 Degrees (Perpendicular Crossing) applies.
When a cable of weak currents (Network) is crossed with a cable of strong currents (Current), the crossing must be made strictly at an angle of 90 degrees (vertical), like a cross.
Why
The physics of magnetic fields says that when two conductors are perpendicular to each other, inductive energy transfer (the "talking" of one wire to another) is practically zero. Never let them cross diagonally at a slight angle or run parallel for a few centimeters at the point of contact.
4. What about wall sockets?
The problem is not only found in the tracks (walls), but also at the termination point: the outlet where you plug your laptop.
In Greece it is customary to use common frames (eg a triple frame that accommodates 2 Schuko power sockets and 1 mains socket).
- To do this properly, the electrician must install in the wall flush boxes (boxes) that have an internal, plastic safety partition between the power section and the data section.
- The UTP cables must enter their own section of the box from a completely separate plastic tube, without wrapping or touching the thick power cables (phase/neutral) behind the switch.
Summarizing
Your data travels at infinitesimal voltages that are extremely vulnerable to the "noise" of everyday power supply. Structured Cabling requires not only good materials, but also strict routing discipline. By maintaining distances of at least 20cm on parallel runs and only crossing cables at right angles (90°), you ensure that your network will perform at 100% of its speed, free from inexplicable disconnections.
Related Articles
UTP, FTP, STP, S/FTP: What do the initials mean, what are the types of shielding and when do you really need shielded cable Cat5e vs. Cat6 vs. Cat6a vs. Cat7 vs. Cat8: The Ultimate Guide (2026) to Choosing the Right Ethernet Cable for Your Wall Star Wiring vs. Daisy Chain: Why in data networks we never branch from plug to plug (like on the phone) Network Certification (Fluke Testing): How Engineers Check Losses, Crosstalk, and Cable Length
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