Does the data centre really need to be shut down?
Data centre availability of 100% is required and can be mapped and implemented by means of various redundancy concepts (e.g. Tier I-IV). Reliable operation is additionally guaranteed by regular maintenance of all system parts, i.e. individual components such as UPS and air conditioning systems are regularly inspected by qualified internal or external personnel. What about the low-voltage main distribution boards, sub-distribution boards and lines in between, though?
Retrospective surveys by property insurers have revealed that 30% of all fires in buildings were caused by faulty electrical installations. This led to the regular inclusion of the SK 3602 fire safety clause in building insurance contracts – although almost no-one is familiar with its content.
“(…) The insurance policy holder must have electrical installations inspected by an expert recognised by the certification body of VdS Schadenverhütung GmbH annually at their own cost and an inspection certificate (Befundschein VdS 2229) issued. (…)”
So the insurance contract even specifies an annual inspection, which begs the question of what is actually inspected and why a shutdown is necessary?
Once the system is set up and at the latest on the day of handover, Facility Management or the electrical manager, not to mention the company owner, is responsible for the proper condition of the system and the safety of their employees. The accident prevention regulation for electrical installations and equipment stipulates, among other, that fixed electrical installations and equipment satisfy the requirements pertaining to the inspection term and inspectors, if 4-yearly inspection terms are observed.
This means that after 4 years’ operation a fixed electrotechnical installation must be shut down for retesting, the reason being the insulation test, which is part of the retest. Insulation testing is conducted with a test voltage of 500V (250V) generated by a measuring instrument and thus requires the system to be disconnected from the power.
The test reports must be documented and presented to the insurance company at their request. Any defects described in the reports must be remedied immediately. Only in this way can insurance cover be preserved.
Interrupting the power supply in the data centre, regardless of whether it is for the function test of a RCD or retesting in line with EN50110-1 Regulation, is not acceptable on account of the necessary maximum 24/7 availability. This perceived conflict seems inevitable – and yet an option compliant with the standard is available that satisfies all normative provisions and availability requirements.
A derogation applies for both the use of RCDs and the insulation inspection (disconnected from the power) in the retest in line with EN50110-1 regulation. RCDs can be dispensed with if sockets are constantly monitored by electricians or electrically trained (instructed) person. Electrical installations and equipment are deemed to be constantly monitored if they are maintained by qualified electricians and if metrological measures are taken to ensure that any damage can be promptly discovered and repaired. Residual current monitoring via Type B RCM sensors (all current sensitive AC+DC) in accordance with DIN EN 62020 counts as such a metrological measure.
This means that residual current measurement reports conducted during a retest are submitted as proof of the insulation level. Other necessary partial tests can be conducted when the system is live, i.e. without having to shut down the data centre.
