A green-yellow wire is essential to connect touchable conductive parts to the safety Earth. It behaves as an inductor at higher frequencies, rendering it useless as equipotential connection. When you select a bad wire length, the wire can work as transmitting or receiving antenna. Equipotentiality only exists with respect to a frequency range (e.g. DC to low frequencies for the safety Earth connection). The type and length of the connection defines in which frequency range the systems can be considered as equipotential.

You can create a clean mechanical design by tying cables together, however it can also disrupt your product’s operation. There are multiple methods to provide interference between cables: resistive, capacitive and inductive coupling. The 2 last options depend on the distance between the cables. Communication and analog lines are often very susceptible and power cables can emit large EM-fields. So intelligent cable segregation is important to prevent self-disturbance within your product. In IEC TR 61000-5-2 multiple cable classes are described going from highly susceptible to highly emissive, together with minimal spacing to prevent EMC problems.

The origin of radiated emission is a signal source at a certain frequency combined with a radiating antenna. The amount of energy in a square wave is mainly defined by the amount of power in its fundamental frequency. However, the band – in which powerful harmonic frequencies are present – are mainly defined by the rise and fall times, which mainly depend on the driver technology used.

If you take into account that a trace of 3,75 cm is a possible quarter wavelength antenna at 1 GHz on FR4, it’s clear that even an 8-bit microcontroller can cause high frequency radiated emission. 

You can indeed self-certify your product in most applications. In the declaration of your product’s conformity, you need to state – on your sole responsibility – that your product complies with all applicable legislation (EMC, safety, RED …). It’s advisable to gather proof to support these claims.

Only an end-user can combine CE-compliant products into a system (such as a home cinema system) without needing to comply with CE. If however, you intend to sell a system, this needs to comply with all applicable legislation. This is harder to achieve than CE-compliance for each of its separate parts.

For example, you combine 4 ventilators into a ventilation system and bring it to the market as one entity. As the system performs the same functionality as a single ventilator, the legislation remains the same. This means that the limits for e.g. radiated emission are the same. In this example, the ventilators of the ventilation system can emit 4 times less than a single ventilator to meet the EMC-requirements.