Electrical demand in the healthcare sector is typically growing at a rate of between 3% and 6% year on year. With the continued developments in the world of technology and innovation it’s easy to see why. Electricity powers the equipment that keeps our families healthy; helping to diagnose and cure conditions, find new forms of treatment, or when required to provide the medical intervention that keeps us alive. It supports the administrative and communications network, connecting devices and applications, cloud-based systems etc, fuels heating, lighting, security systems …. the list goes on.
The sustained growth in demand highlights just how much we continue to rely on this particular power source. Yet it is more than purely the energy that we need. To support the growing requirement, we also need a robust electrical infrastructure - one that is capable of supporting the increasing forms of technology and innovation whilst still being able to meet the rising demands and expectations of patients.
Unfortunately, the UK’s hospitals and healthcare facilities are not immune to power issues, such as supply failures and anomalies. Nor are they exempt from power disturbances within the electrical distribution system. It is a concerning statistic that 80% of power quality issues actually originate onsite, largely from the electrical equipment itself, with only the other 20% arising through the energy provider.
These issues normally arise due to a distortion of electrical signal, the components within the equipment having loads which are non-linear current and voltage changes, such as variable speed drives or semiconductor technology. They will manifest as flickering lights, network communication issues, loss of data, humming transformers, tripping circuit breakers or in some instances, the unexpected shutdown of equipment.
The resulting disruption to services can cause extensive problems to the daily operation of departments. Add to this the risk of potential cyber-attacks, data breaches and malfunction of critical equipment, that can be caused through external power anomalies and outages, and the need for additional levels of resilience in the electrical infrastructure becomes very evident.
With the correct power protection strategy in place however, it is possible to overcome these areas of weakness to create a robust and reliable electrical infrastructure capable of protecting staff, patients, the general public and facility alike.
Power Quality Issues within Healthcare Facilities
Harmonics are the result of nonlinear loads that convert AC line voltage to DC. Due to the larger electrical current that is being drawn, they will often cause electrical systems to overheat, increasing the potential risk of fire, whilst also affecting the lifetime of the equipment the load is supplying.
Within a hospital setting, harmonics can usually be traced to active electrical equipment that contains variable speed drives and/or semiconductor technology; such as X-ray machines or MRI scanners.
The installation of power quality correction units will help to take care of many internal electrical disturbance issues however additional harmonic resilience can also be provided through a UPS.
Whilst it is accepted the UPS solution will typically add harmonics to the wider system, it will protect specific loads from excessive harmonics. The small filters on the input and output of the UPS can be used to create a virtual neutral allowing common-mode harmonics to pass through to the inverter, which are then cancelled by the inverter’s output.
The UPS’s primary function however, is obviously to provide a ‘no-break’ instantaneous supply of electricity that will safeguard vital equipment and applications throughout the healthcare facility. In areas where this is critical to patient care or safety, additional levels of resilience can also be built in through the design and configuration of the UPS system.
Building resilience through UPS system configuration
The selection of any particular UPS configuration for the emergency protection of final outlets, circuits and equipment will be dependent on the specific factors of each individual design. This should be based on a risk analysis to determine the appropriate level of resilience required.
According to the Health Technical Memorandum, HTM 06-01, a UPS system should be to, but not limited to, the following design and manufacturing standards:
- BS EN 620040-1
- BS EN 60146-1-1
- BS EN 61439-6
- The Energy Networks Association’s G5/4-1
UPS system ratings range from 250 VA up to several hundred kVA; the smaller units may be single-phase units used to support a single circuit, with the larger UPS systems either single-phase or three-phase capable of supporting an entire department.
A central UPS system may be considered where the need covers several smaller areas however designers should be aware that providing a central UPS system may increase the risk of single points of failure that will then ultimately affect a larger area or potentially more departments. Risks for consideration include the routing, location and segregation of UPS distribution cabling and switchboard configuration designed to avoid a single fire or fault affecting the whole system.
There are several recognised UPS system configurations; all of which will depend on the application they are supporting. Any design must be able to demonstrate that it is the optimum solution to maintain both patient safety and the associated systems, where loss of power will have an effect on normal operation of the healthcare facility.
UPS Arrangements – What’s the Difference Between Parallel Capacity (N) and Parallel Redundancy (N+1)
Parallel Capacity (N)
UPS units that are operating in parallel capacity (N) refers to where the total load demand is met by a number of UPS units. In this configuration there is no provision for redundancy (ie spare capacity). As a result, this design will not increase system resilience.
Carrying out maintenance on a parallel capacity UPS installation will therefore mean bypassing the entire UPS system, so that one or more modules can be powered down for service. At this point the load will be left unprotected as it is then powered directly by the mains supply, leaving it vulnerable to power anomalies or complete outages.
Dual UPS (N+N)
An N+N UPS configuration allows for redundancy due to the ‘two of everything’ approach and should be considered for medical locations in Group 2 or where support systems are considered high risk.
Each UPS will be rated for 50% of the load required through two systems. For greater resilience each UPS may be rated at 100% load with interleaved auto changeover provided to support the full load to all medical IT requirements in the event of total power failure.
Parallel Redundancy (N+1)
Introducing redundancy into the power supply, where two or more UPS units are capable of powering the load, provides a further level of resilience. This is often expressed through the term N+1.
The Health Technical Memorandum (HTM) considers N+1 to mean the normal total requirement plus one resilient unit, each individual unit being able to fully support the load. Under normal operating conditions each of the UPS will share the load equally. Should a power failure occur, both units will instantaneously switch to battery mode and the load continue to be shared. If either of the UPS fails it will automatically disconnect from the output AC busbar leaving the remaining unit to fully power the load.
For example, where the electrical demand is 600 kVA, two UPS systems at 600 kVA carrying 50% of the load would satisfy the N+1 definition.
The configuration is often used to protect critical or sensitive equipment or applications as it creates a level of fault tolerance that cannot be achieved otherwise. In the event that one of the UPS units fail, the additional unit (or units) will seamlessly take over the full operation of supplying power to the critical load, ensuring that devices remain functioning regardless of the circumstances. The solution is suitable for supporting inter-process communications and information technology areas. It can also be used in areas where space is at a premium or conversely, where further growth is possible.
The N+1 configuration enables UPS maintenance and servicing to be conducted without any interruption to the load, one module being allowed to power down whilst the remaining unit continues to support the load.
N+2 Redundancy would refer to the next level up, where the system functionality would have two separate backups. This further increases the redundancy of the system, providing an additional level of resilience for users due to the configuration of having two separate backups. Should one of the backups become corrupted, there are still two further units to guarantee supply to the load.
If you are looking to build additional levels of power resilience to safeguard your healthcare facility, it is crucial you seek the advice of a specialist UPS provider.
Power Control has nearly three decades of experience working in the healthcare sector and maintains UPS systems for a plethora of NHS and private healthcare sites across the country. The UK’s largest privately owned and independent UPS and power protection specialist, the company has an extensive portfolio of systems to suit a wide range of needs. For more information, please visit powercontrol.co.uk, email info@powercontrol.co.uk or call the office on 01246 431431.