ELECTRICAL INFRASTRUCTURE Harmonics
Power is also becoming more polluted. As a result, power quality is becoming harder to achieve and maintain. The power electronics present in digital devices generate harmonics, which occur when the electrical signal itself is distorted rather than displaced. Looking at the electrical signal, it can appear as if another, higher frequency, waveform has been superimposed on top of the signal. The cause of this can usually be traced to active electrical equipment containing variable speed drives and semiconductor technology, with X-ray and MRI systems being large contributors. In a hospital, the most common ways that harmonics will manifest are as transformer heating, humming, or as disturbances on an ultrasound machine. The issue, however, is not so much the effects they cause, but rather the potential safety and reliability impact. Harmonics will cause electrical systems to overheat, due to a larger current being drawn, which not only affects asset lifetime, but also greatly increases the risk of fire. Looking from a pure reliability perspective, 30-40 per cent of unscheduled asset downtime is related to power quality issues, so without rectifying the problem, you will see a significantly lower efficiency for the equipment you have installed.
Diagnosis
As a short-term means of diagnosis, a power quality survey can be carried out on site using a power quality analyser. These are left connected over the course of a week of normal operation to get an overview of any power quality issues over the seven-day period. This will look at harmonics, power factor, voltage spikes, sags, and swells, among others. However, as hospitals are very electro-intensive, a more common solution is to install a range of power meters. These are
X-ray and MRI units are significant contributors to harmonics issues with the electrical supply, Schneider says.
installed at various stages in the electrical distribution system, from the main incomer to the hospital, to various buildings, and on individual distribution boards. These meters vary in the depth of power quality analysis, with more high-end meters being able to provide directional analysis to determine whether any disturbances originated up or downstream of the meter. This allows for a fast and reliable means of finding the root cause of any disturbances. Having these meters provide data into an energy management system is the best means of performing analytics and monitoring alarms and trends. These options also ensure continuous monitoring of standards compliance, and can raise alarms if anything is out of the ordinary. A fully comprehensive energy management system can even help you utilise predictive analytics to preempt issues before they are a problem. Additionally, smart distribution boards are another advantage in measuring, at load level, the root cause of the disturbances. As a new or retrofit option
to existing sites, using small, circuit breaker level meters can be a low-cost way to ensure that individual assets or systems are performing in their most efficient state.
Solutions
Healthcare organisations need to investigate the types of equipment and digital applications that can help them mitigate these problems, and achieve and maintain high quality power throughout their electrical network. Luckily, the solution to most power quality issues is relatively simple. Installing power quality correction units on site will take care of the problems without manual intervention. As hospitals tend to experience a lot of harmonics on site due to active electrical equipment, the most fitting type of correction unit is active filtering. These units effectively take a signal which is experiencing harmonics, low power factor, or other issues, and ‘clean it up’, to output a smoother, more reliable signal. Alternatively, if the issue on a particular site is solely power factor- related, the installation of capacitor banks is a cheaper, and equally effective means of fixing the issue.
Hospitals and their staff require an extremely reliable electrical infrastructure, immune to power failures, and resilient against any issues.
54 Health Estate Journal April 2021
Digitisation and innovation are making it easier to take a more proactive approach to power reliability. To prepare for and preempt the kinds of power- related challenges their facilities are likely to encounter – to build resilience – healthcare providers and their healthcare engineering teams should consider evolving diagnostic and preventive technologies and innovations such as microgrids, power automation, power events analysis, and condition-based maintenance. Using such solutions will ensure that the Trust or private healthcare provider only pays for the energy it is using, and is getting the most out of it. Feeding better quality signals into the electrical equipment will allow it to perform at its best and prevent failures. With the need for hospitals to operate at
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