Category: Ideation

High-resistance grounding provides safer, more reliable electrical distribution for healthcare facilities

High-resistance grounding is relatively simple and easy to apply in radial distribution systems. It has been used in the healthcare industry for many years, considered to be “best practice” for hospitals. The concept is well-known, recognized by the Canadian Electrical Code, and driven by four basic factors: power is not interrupted in the event of a single ground fault; negligible damage at the point of fault, resulting in lower repair costs and faster return of equipment to service; negligible arc flash hazard in the event of a single ground fault; and negligible risk of a single ground fault escalating into a damaging line to line or three phase fault.

It is best practice to have the low voltage (600V) and high voltage (4,160V) systems equipped with high-resistance grounding. This has often taken the form of a neutral  grounding resistor applied between transformer neutral and ground. An alarm is raised on the occurrence of a ground fault in the distribution as required by the installation codes. In modern relays, the zero-sequence sensor signal causes a pick up; then the simultaneous presence of unbalanced voltage to ground is verified before an alarm is indicated. To avoid the possibility of nuisance alarms caused by inrush currents and non-inear loads, the zero-sequence current sensor output is filtered and only the fundamental signal is extracted. These measures have been effective in avoiding nuisance alarms and trips in sensitive ground fault relays.

The primary benefit of using high-resistance grounding is the faulted feeder does not need to be isolated on the occurrence of a phase to ground fault.

Vantage Point

The use of high-resistance grounding offers many benefits.

Arc flash and blast hazard for a line to ground fault is prevented. For systems up to 4,160V, where the resistor let-through current is 10A (amperage) or less, the arc blast is unlikely. Such systems can continue to operate with one ground fault. The fault does not escalate so the distribution system is safer. Accidents causing line to ground faults will not produce a hazardous blast or arc flash.

Fault damage at the point of fault is very low and can be easily repaired. It minimizes maintenance repair costs. Motor and generator laminations will not get burnt and winding repair costs will be small.

For systems up to 4,160V, where the resistor let-through current is 10A or less, the line to ground fault can be kept on the system continuously. No fault isolation needs to occur per Canadian Electrical Code 10-1100 through 1108.

Damaging voltage transients that can occur on ungrounded systems are avoided since the system is grounded.

On the other hand, four application concerns arise when resistance grounding is applied to distribution.

All cables need to have a line to ground voltage rating of line to line voltage for the maximum duration of the line to ground fault. This is not an issue at low voltage, such as 600V. The standard cables have adequate ratings.

Lightning arrestors and surge suppression devices that are connected line to ground also need to be adequately rated.

Voltage to ground impressed on capacitors will also increase to line to line value.

The circuit breakers and contractors employed in resistance grounded systems must be able to break L-L voltage across one pole of the device. For example, a three pole 600V breaker must be able to open fault current and withstand 600V across one pole, which most 600V breakers are capable of. However, some breakers only have a 347/600V rating. This  means they are able to interrupt only 347V across one pole, making them unsuitable. The same would apply to contractors.

In this scenario, a ground fault occurs in the switchboard downstream of a transfer switch.

Fault Scenario

In a typical hospital, there will be a 600V normal power system and a 600V generator power system. The most critical loads are fed from the emergency power distribution, which is downstream of one or more transfer switches. The transfer switches get power from both the normal power system and the generator power system. In this scenario, a ground fault occurs in the switchboard downstream of a transfer switch. This fault could have a number of causes.

In the solidly grounded system, the ground fault results in a large current flow creating significant damage within the switchboard, vapourizing components and coating the inside of the switchboard with semiconductive residue. The high fault current subjects the upstream transformer to high stresses and causes the upstream breaker to trip. All power to the critical loads is lost. The loss of power is sensed at the transfer switch, which starts the emergency generator and transfers the critical load over to the generator. Since the switchboard is contaminated with residue from the previous fault, another fault occurs and this further damages the switchboard. It also stresses the generator with a high magnitude fault current and causes the generator breaker for the transfer switch to trip. The critical loads, including the emergency department and intensive care unit, are shut down and remain so until their feeders can be cut away from the failed switchboard, spliced and extended to another source of power – a process that takes many hours and leaves the critical loads on normal power only. The hospital is forced into emergency mode and must transfer critical patients to other areas of the hospital, which were not designed for their care, and in some  cases to another hospital. Full restoration of the system requires replacement of the switchboard. This takes many months as switchgear is built to order.

In the resistance grounded system, the ground fault results in an alarm. There are no power interruptions, the main transformer is not subjected to the stresses of a fault, and the generator does not start, and is not exposed to a fault current. Most importantly, the damage to the switchboard is minimal, requiring the replacement of a single insulator, which is scheduled for a time when the hospital can accommodate the short shutdown necessary to perform the work.

Ground Current Detection

A major functional enhancement occurs when detection and alarm of ground faults is supplemented with monitoring of all the feeders to indicate which feeder is faulted and administer assistance for quickly locating the fault.

To provide assistance in locating a fault in highresistance grounded systems, the fault current is modulated by oscillating it between values such as 5A-10A, typically at one cycle per second. This is accomplished by changing the resistor value using a contactor, which has been called ‘pulsing’ in the industry. The  pulsing is manually started. A flexible zero-sequence sensor or a clamp on the current transformer encircling all phase conductors is used to provide an oscillating signal to a handheld multimeter. Readings are taken on the faulted feeder moving away from the switchboard. The signal will disappear once the fault location is passed. Often, two or three measurements are sufficient to point to the fault location. Readings are taken from the outside of the grounded raceways, conduits or busways, while the system is energized and running. This technique has been in use for many years. It is quite effective for voltages up to 4,160V.

Tripping Up

The primary benefit of using high-resistance grounding is the faulted feeder does not need to be isolated on the occurrence of a phase to ground fault. While the faulted system continues to operate, there is a possibility that another phase to ground fault may occur on a different phase in some other weak spot in the distribution system. With the presence of a second fault, the fault current is no longer limited by the resistor and will be a higher magnitude fault. The zero-sequence sensors continue to monitor the fault current and if a significantly higher current than that limited by the resistor is detected, then the system recognizes that a line to ground to line fault  exists and identifies the two feeders involved. Only one feeder breaker needs to be tripped to revert the rest of the system to a single fault condition. A level of priority can be assigned based on the relative importance of the feeders. The one feeder with lower priority is tripped. Fast operation provides protection and minimizes fault damage. Such systems have been in use for a long time and this first fault alarm and second fault trip is best applied to monitor specific loads.

Improving the System

On low voltage systems and systems up to 5 kilovolt (kV), high-resistance grounding  provides a safer and more reliable distribution system. The arc flash hazard in the event of a line to ground fault can be eliminated and power continuity maintained. The  performance of the distribution system can be enhanced by using high reliability neutral grounding resistors with low temperature coefficients, monitoring the neutral ground resistor continuously, using a pulsing system to find ground faults and using coordinated selective second fault tripping. In many applications, it is more beneficial to apply the neutral grounding resistor at the main bus. In such a case, the incoming supply feeders can be monitored for ground fault very cost-effectively by applying multi-circuit relays.

Authors

Ajit Bapat, P.Eng., Owner of Power Solutions
Nick Carter, P.Eng., Principal at HH Angus & Associates Ltd.
Sergio Panetta, P.Eng., Vice-president of engineering at I-Gard Corp.

Hospital redevelopment projects provide a unique opportunity to build for the future

The increasingly critical role of technology in patient care has resulted in a dramatic increase in demands on communications and information technology infrastructure in hospitals, but aging facilities pose significant challenges to the staff who support and maintain these systems. Many hospitals in Canada were constructed well before the emergence of modern information technology, which typically means telecommunications equipment is squeezed into undersized spaces without sufficient power or cooling to ensure these important systems stay operational.

IT spaces added as an afterthought to existing construction In older buildings, telecommunications spaces have gradually expanded as the systems grow, creating a
number of challenges:

  • Locations are often chosen based on what space is available, rather than what is appropriate, meaning that the size and shape of the rooms may not properly support the equipment, or the site may be adjacent to
    wet piping or sources of interference.
  • Addition and removal of equipment over many years often results in an inefficient layout and lack of appropriate cable management or identification, making maintenance more difficult.
  • Supporting services, including power and cooling, may not have the appropriate capacity or redundancy for IT loads, and equipment shutdown for maintenance and repairs can impact the availability of these services.
  • Limited ceiling space in older facilities can impact the ability to add services (i.e. chilled water loop) or new communications cables.

Limitations have a significant budget impact
All of these challenges can have a significant impact on operational and capital costs, and can add up to multiples of what is typical of a new installation with properly designed spaces and systems.

The greatest impact is seen in operational costs, where limitations make the systems more difficult to maintain, support and upgrade. From a user perspective, network performance can be affected by things such as heat or interference, which can create unnecessary delays in accessing information or even unplanned network downtime – a condition which critically impacts patient care across the entire facility. However, capital costs are not immune to these conditions either; overheating, dust and vibration can reduce the lifespan of equipment, meaning it must be replaced sooner.

Redevelopment with the future in mind
Hospital redevelopment provides the opportunity to build new IT systems that can withstand the test of time, and to address issues with existing systems in order to support expansion. While no one can predict the needs of technology decades from now, the following principles will help avoid creating similar challenges in the future:

  • Engage users early on in the planning process, and design IT systems to align with the technology vision for the hospital. This approach facilitates adoption later on and helps ensure IT systems can support the
    unique needs of the facility.
  • Consider the facility as a whole when implementing new IT systems and infrastructure; design decisions for new spaces can have a significant impact on existing IT infrastructure, and a gap analysis can help prevent unpleasant surprises later on.
  • Provide additional capacity and flexibility in infrastructure, spaces and supporting systems so they can be adapted as technology progresses.
  • Aim for consistency in services throughout the facility. Differences in system performance or user experience can impact adoption, staff satisfaction and, in the case of clinical life safety systems, even patient safety.

It is also worth investigating which challenges can be addressed in place and which would benefit from a “greenfield” solution. For example, building a new data centre in a newly constructed area of the building is often less complex and cheaper than mitigating issues with the existing location. Many redevelopment projects use this opportunity to create a space that is properly sized and designed to support critical IT systems for the entire facility. The practicality of options should be evaluated as part of the planning process.

Ultimately, redevelopment projects are a chance for hospitals to create efficient and cost-effective IT systems capable of supporting the critical nature of technology in healthcare, and support the highest standard of patient care.

Author:

Kim Osborne Rodriguez,P.Eng., RCDD
kim.osbornerodriguez@hhangus.com
Published June 2016 in the Canadian Healthcare Engineering Society website

On January 13, Toronto’s Emerging Leader Forum (ELF) hosted an engaging discussion on Digital Health focused on informing young leaders in healthcare. The event was led by Dr. Darren Larsen, Chief Medical Information Officer at OntarioMD, who facilitated the discussion with:

  • David Denov, Senior Manager, National Health Services at Deloitte
  • Dr. Trevor Jamieson, Virtual Care Lead, Women’s College Hospital
  • Laurie Poole, VP, Telemedicine Solutions at Ontario Telemedicine Network
    Throughout the discussion, key themes of patient-driven care, improved outcomes, reduced cost and better coordination of care emerged as central drivers for the adoption of digital health.

What is Digital Health ?

Digital health is empowering people to better track, manage, and improve their own and their family’s health, live better, more productive lives, and improve society. (Wikipedia)

 Despite having a relatively straightforward label, the concept of digital health encompasses a complex set of ideas that differ greatly between sectors and people. While many associate digital health with smartphone apps and telehealth, Dr. Trevor Jamieson is quick to differentiate between virtual health and digital health, noting that “how you use data to drive better decision making” forms the core of how digital health impacts how we care for patients. Many would agree that data has become critical in the delivery of healthcare across varying sectors from acute to primary care, and the ability to manage and apply data efficiently will likely become future differentiators for providers in the healthcare market. 

Unfortunately, one of the primary challenges of delivering on this definition of digital health is a lack of interoperability and integration both within and between healthcare organizations, which means that data cannot be leveraged to maximize its value. It’s not just enough to have astronomical amounts of data; it has to be delivered to the right person at the right time.

What’s holding back the adoption of digital health?

A combination of limited funding and a conservative approach to technology seem to be the biggest obstacles to the adoption of digital health in Ontario, but Laurie Poole is optimistic: “Technology used to be an afterthought, so there has been a big shift from even four years ago.”
However, funding models that reward physical presence rather than virtual care, and privacy legislation that limits how organizations store and share data are two big barriers noted by David Denov and Dr. Jamieson. “Hospitals and providers have convinced themselves that change has to be incremental, and that disruption is undesirable,” says Dr. Jamieson. “You will never have innovation without a bit of risk.” Clearly innovation needs to be balanced with the risk and potential consequences for patients and their data.

How can Canadian hospitals become leaders?

Looking to other health systems that have achieved widespread adoption of technology and digital health, it appears that that big changes have to be driven (or at least strongly supported) from the top down – and not just within the hospital, but from health systems or regional leadership in healthcare. Poole points out that integrated health systems in the US have leveraged their power as a closed system with a single HIS to drive mainstream adoption of virtual care, but that a lack of integration in Ontario has been a key challenge in achieving the same adoption. Many G8 countries are facing similar challenges of constricted spending, limited infrastructure and an aging population, and consolidating leadership at a regional or provincial level may help coordinate adoption. “Every [Ontario] hospital has an independent board of directors,” Dr. Jamieson adds, which may contribute to the challenges in achieving widespread adoption.
This might imply that Ontario hospitals are stuck in siloed information systems without a strong mandate from provincial leadership, but momentum is building and there are a number of initiatives which are working towards broader integration. Initiatives such as ConnectingGTA and the current [as of 2016] provincial hold on new Hospital Information System implementations may be the first step towards standardization.

Where do we go from here?

From the patient perspective, there is a growing expectation of digital health integration throughout their healthcare journey regardless of care location. Many of our Ontario hospitals have been able to leverage digital health effectively within their own organizations and work with healthcare partners on a community level, but growing pressure from patients will likely continue to push for provincial and even national initiatives which improve on inter-organizational integration. It is certainly clear that digital health has the opportunity to transform how care is delivered to the patient – from improved data analytics & big data to driving better patient outcomes through 360-degree healthcare coordination, digital health is becoming an essential part of effective healthcare.

 

Author: Kim Osborne Rodriguez, P.Eng., RCDD

The information technology needs of health care institutions are rapidly expanding, which makes it critical that the communications infrastructure is planned strategically.

Authors: Kim Osborne Rodriguez, P.Eng., RCDD | Megan Angus, RN, MBA, Lean, EDAC
Published September 2015 in the Canadian Consulting Engineer Magazine

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