The volume of digital data is increasing swiftly and continues to grow. One of the main causes are cryptocurrencies like Bitcoin (XBT), Ether (ETH), Litecoin (LTC) etc. or blockchain technology, which to a certain extent, is like a type of database which runs on several networked servers. The growing demand for data exchange is also spawning the growth in the number of data centres, and they are being planned, built and maintained at massive scale around the globe. However, data centres have to deal with complex challenges in terms of the supply of electric energy, which can have an effect on secure (and legally- compliant) 24/7 operation.
Various studies have shown that mains power quality problems generate costs that run into the billions each year. Already in 2007, the Pan-European LPQI Power Quality Survey 2007 estimated that the damage was equivalent to 150 billion Euros annually. Meanwhile, the challenges for everyone have continued to grow.
As described earlier, power quality problems can generate disturbances and system failures which inevitably result in additional cost, time and effort. Power supply noise represents a non-negligible risk (see figure 2) especially for data centres, which are equipped with capital-intensive redundancy (for example UPS systems, generators, multiple power sources) and which normally ought to prevent any downtime or potential damage. Ideally, all the installed equipment should be compliant with the harmonic distortion and noise immunity standards, so it is probable that they can operate trouble-free. However in an unfavourable operating context, for example a large number of similar consumers, asymmetrical net loading, etc., significantly excessive noise levels can occur. To be able to estimate the risks as well as limit them on a permanent basis, power quality monitoring is thus essential.
The above-mentioned standards give guidelines on how the mains power should behave at the monitoring point in normal operation. Exceptional situations which could lead to the energy supply being temporarily restricted are not covered. It is compulsory to record these types of disturbance, such as voltage dips or interruptions, however there is no specified limit to their number in order to be compliant with the standard (see figure 4). The function of UPS or backup power supply systems is to be able to compensate for any power supply constraints. These backup solutions are however limited to the most important resources, so it may be that other components operate with only reduced functionality. For this reason, it is critical that operating personnel are quickly informed when an IEC 61000–4‑30 type event occurs. This can be implemented by an automatic notification sent to the competent people by email for example.
A further aspect: RCM
To prevent operations being interrupted unexpectedly, data centres avoid using residual current monitoring devices (RCDs) with direct triggering. In the contrary, it is compulsory to monitor residual currents on a permanent basis (see figure 5). In this case, RCM (Residual Current Monitoring) is used, which as well as its essential function of protecting people’s safety, also protects the systems from damage and aids fire prevention. Furthermore, changes in residual currents can provide an early warning of any deterioration in the insulation and allow corrective measures to be undertaken. Errors occurring in the TN‑S system (for example illegal or additional PE‑N connections can also be in detected early and corrected as a result).
Correct measurement data through metrological traceability
An old locksmith’s saying is “centimetres are a clockmaker’s measurement”. Put another way, “he who measures, measures garbage”. Technicians and economists know this and they take heed of this well-known and still useful warning, making sure they use the right method for each type of measurement. However in spite of the fact that the required specifications of a power quality device are precisely defined in terms of measurement methodology (IEC 61000–4‑30), device characteristics (IEC 62586–1) and validation of compliance with the standards (IEC 62586–2), there are still differences between the manufacturers. Suppliers are often unable to prove why their analysis device meets the specifications and measures correctly. Proof of a truly correct measurement can only be obtained from an independent certification lab, ideally a metrological institute. Non-certified test labs, or even the manufacturers own statements cannot be a substitute for metrological certificate and thus should be viewed with a critical eye. This is especially true where sensitive activities such as data centres are concerned, which are associated with high costs and risks.
The benefits of metrologically-certified power quality monitoring
The main benefit of a professional and permanent power quality monitoring is the increased operational availability of data centres. Whereby power quality is defined as a key component of supply quality (see figure 6) and is naturally applicable for many other sensitive areas other than data centres (for example hospitals, sensitive industrial sites, in transport infrastructure such as airports, publicly-accessible building complexes such as shopping centres, etc.). The benefit is obtained by analysing the recorded long-term data to observe the changes and identify correlations. Compliance with the contractual supply guidelines is just one of the important aspects.
Drawing the correct conclusions from metrologically-certified power quality monitoring including RCM, results in the durable protection of investments, reduced operating costs, maximisation of data availability and very importantly, the satisfaction of all stakeholders. These include customers, employees, energy suppliers, operators, investors, service contractors, authorities, associations, etc. And lastly, it helps to lower CO2 emissions because it makes it possible to operate the data centre more efficiently and securely.
A further aspect to be considered is whether continuous and qualified monitoring of the mains power could also be used to prevent cyber attacks on the energy supply of data centres or other sensitive activities. This would be quasi-redundant to the existing monitoring systems which are already implemented as software solutions, but which are however subject to enormous dynamics. The purpose is to research whether a connection can be found between changes in power quality and cyber attacks on a data centre’s servers and infrastructure, and as a result be able to fend them off early.