2/2018 | MONITOR | 29 Following the entry into force of the new EMC guidelines 2014/30/EU, the stricter specifications have been bind- ing since 20 April 2016 at the latest. Using residual current monitoring to implement the guidelines Truly reliable statements as to what is happening in the power supply can only be made by permanently mon- itoring and analysing the power supply. Various values are thus measured in real time at essential nodes in the power supply and recorded for subsequent evaluation. When using these measured values, experts can draw additional important conclusions as to the operating condition of the TN-S system. Uncontrolled residual cur- rents (leakage currents and fault currents due to insula- tion faults) can impair the system and operational safety. What does the standard say? The relevant standards for electrical engineering (among others DIN VDE 0100 444: 2010-10) and also the new standard EN 50600-2-2: 2014 require that TN-S systems be used exclusively in data centres. In the publications on the standards and specifications as well as on the IT baseline protection developed by the BSI (Federal Office for Information Security), the importance of an EMC-compliant installation is always stressed in this context in order to avoid disturbances from stray cur- rents and damage to devices and conductive building components. The fundamental basis, without which all further measures are futile, is a power supply system designed as a TN-S system with a central earthing point. TN-S systems are of the essence With regards to TN-S systems, DIN VDE 100, part 4184.108.40.206 states: “Installations in new buildings must be set up as TN-S systems from the point of supply. In existing buildings which contain or will probably con- tain important IT 1) resources and which are supplied by the public low voltage distribution system, a TN-S system should be set up from the start of the installation system.” With older systems (TN-C, TN-C-S) 2) , conversion to a TN-S system is necessary (fire risk, protection of mate- rial assets, protection of people etc.). Furthermore, the orderly condition of the new installation must be main- tained on a permanent basis, as even an unintentional bridge between an N and PE conductor can result in unforeseen disturbances. New standards and regulations for data centres require that new approaches must be taken in many places. Steadily increasing performance requirements, the unrestrained increase in energy demand, but also economic aspects nowadays only allow the operation of a state-of-the-art data centre. The trouble-free power supply has become of crucial importance. When using continuous monitoring of the electrical installations, disturbances or even failures can be detected and avoided well ahead of time. The technical managers at the Regional Data Centre Erlangen (RRZE) have recognised the challenges and are therefore using technology provided by Bender. 1) IT stands for information technology and comprises all technologies relating to electronic data processing. 2) TN-C: The functions of the neutral conductors and the protective conductors are combined in a single conductor in the entire system. TN-C-S: The functions of the neutral conductor and the protective conductor are combined in a single conductor in one part of the system.