T 4.88 Electrical power supply unsuitable for EMC

Modern IT systems are characterised, among other things, by the following three characteristics:

• extremely high networking
• extremely high clock rates
• very small signal levels

It is exactly these three characteristics which make modern IT networks increasingly susceptible to interferences from electrical power supply networks unsuitable for EMC, meaning networks which are not electromagnetically compatible. Major sources of interference to be mentioned are:

Design of the electrical power supply in the incorrect network form (no TN-S system)

All other network forms, except TN-S systems and TT systems with good continuous earth electrodes, promote the occurrence of currents in the PE system.

Inadmissible currents in the PE system and inadmissible inductive coupling due to a control cabinet design unsuitable for EMC

Currents in the PE system adversely affect the data transmission on copper-based data cables and result in preliminary failure of technical equipment.

Too high levels of interfering frequencies from 150Hz and above up to the 100kHz range

It is not only the usually considered harmonic frequencies up to 1kHz or 2kHz, but also the interfering frequencies far above these which can significantly impair the data transmission and the functionality of IT equipment.

Electromagnetic fields due to improper cable routing

Electromagnetic fields cause currents in electrically conductive systems which are actually not supposed to flow there and can thus cause damage in all areas relating to IT.

Incorrect adjustment to the actual active factor (short also "cos Phi" or "Cosinus Phi") of the supplied consumers

Many electrical power supply systems including existing emergency power systems (EPS) and UPS installations are still designed for supplying inductive loads while the vast majority of all IT devices cause a strongly capacitive load behaviour in the network. The result of such maladjustment is, in addition to a high power loss, unpredictable failures of power generators (EPS and UPS).

Lack of information on the current operating state of the electrical power supply system, in particular on whether the TN-S system is correct

Without sufficient knowledge of all operating states of the electrical power supply system in real time it is not possible to recognise potential problems. Without a record of this real-time data it is nearly impossible to determine and eliminate the actual cause in the event of damage.