Chronic repair spending is a known symptom of power quality issues
By Christopher Smith
Undesired operation” may sound nicer than “failure,” but in the healthcare industry, nobody’s looking to spare the equipment’s feelings. And failing medical equipment incurs costs that can be counted in multiple columns: the risk of diagnostic error, scheduling issues, lost billing, overtime, lost productivity, employee stress and turnover, and (of course) repair and replacement costs.
However, if you are experiencing constant failures in medical equipment, the problem may not be with the equipment itself. It might be your electricity. Medical technology is susceptible to power quality issues, and healthcare facilities have complex, variable power draws that can lead to power quality problems.
How Do I Know It’s Power Quality?
If your problem is persistent or abnormally frequent, that could mean something external to the equipment is hastening its failure. Start by checking the frequency and timing of equipment issues. If you can match your failures to changing demands on your power system, you could have a power quality problem.
There’s no “one-size-fits-all” troubleshooting method that will help you uncover power quality issues, and if you suspect them, you need to consult immediately with someone qualified to safely assess your system.
It’s important to think about the whole system, since it’s not just a question of power loads from large equipment like MRI machines and CT scanners. Computers and other equipment throughout your facility create nonlinear loads. Those nonlinear loads can create disturbances in power systems that affect both your electrical assets and the equipment they supply power to.
Why Are Power Quality Issues Destructive?
The term “power quality” doesn’t exactly convey the serious technical problem it describes, so let’s take a moment to explore what it means. Most of us think about electricity as just “on or off,” but there are really three states of operation: transient, steady state, and decay. Remember “an object at rest tends to stay at rest, and an object in motion tends to stay in motion?” It’s the same for electricity.
Whenever anything is energized or deenergized, there’s a transient state before the equilibrium you expect—the steady state—is achieved. Sometimes that equilibrium is harder to achieve than it should be. Meanwhile, the voltage is surging and sagging in the system, which can give a device more than it can safely handle or less than it needs to operate reliably. Both situations can damage equipment or cause it to fail, especially after repeated occurrences.
The other common power quality problem is harmonics. Alternating current is like a wave, and just like other kinds of waves, it can experience interference. There are many pieces of powered equipment in a healthcare setting—from medical devices to computers to operational needs like HVAC—each of which creates its own little ripple in that wave. There’s a real danger that all those ripples can add up and create enough distortion to damage equipment or cause failure.
One of the most dangerous causes of power quality issues is improper grounding. Proper grounding is key to the protective mechanisms in place to limit dangerously high voltage and the risk of shock and arc flash from electrical incidents. When power quality problems are ignored, it could mean improper grounding is being ignored—a clear safety risk.
Damages Like This
One hospital experiencing unexpected failures from a medical imaging system asked ABM Healthcare to investigate. An integral part of the machine, a solid-state card, had already been replaced multiple times. That meant multiple failures had been endured and the cost of parts and labor had multiplied.
ABM found that it wasn’t really a repair issue with the imaging equipment. The real cause of failure was the excessive harmonics in the electrical system powering the unit. Instead of just replacing the part again, the power quality issue was resolved with improvements to the hospital’s high-voltage cabling. That stopped the habitual failure of the imaging system and had the added benefit of alerting the hospital to harmonic problems throughout the facility that could now be addressed before further systemic damage occurred.
Let’s Look at Another Case
Here’s an example of the interdependency of equipment and power systems in a healthcare setting: the hospital in question was experiencing multiple trip conditions. In this case, variable-frequency drives (VFDs) for the HVAC system were tripping during normal operation. Underperforming ventilation was a concern for the hospital—and disabling the ground fault protection was a nonoptimal solution.
The tripping might have been caused by maintenance issues with the VFDs themselves, and so an HVAC tech could have been called, but the frequency and persistence of the issue pointed to power quality issues. Focusing just on fixing or replacing the drives might not solve the problem, and letting any underlying power quality issues continue could put other critical equipment in the hospital at risk. For instance, the possibility of higher ground currents in the system could create safety hazards and equipment failure risks.
Two main points about the evaluation should be made before we look at the results. First, the successful analysis depended on measuring real, dynamic load behavior in the facility during a routine operational day, which takes some expertise in testing—including accounting for the control systems of the VFDs. Second, a clear record of the failures the facility experienced helped the investigating power engineers to best pinpoint their testing strategy, so a clear preliminary investigation of the facts is always important, but on no account should unqualified persons ever attempt testing of trip conditions or power equipment.
ABM engineers took measurements on the load side of the VFD, looking at the ground currents, total harmonic distortion, and the phase-to-phase voltage. By graphing all the data throughout operations and testing while controlling other key variables, a clear cause of the problem was uncovered.
A current unbalance was detected, with a variation over that specified by the VFD manufacturer for power inputs. The study revealed that the rising ground current happened concurrently with the current unbalance. The key to avoiding the ground current problem and the tripping conditions was keeping the current unbalance from happening.
The recommendations for fixing that problem, however, had to take the whole system into account. To avoid increased costs and decreased efficiency, the electrical power distribution system had to have its load balancing verified and checked for small insulation breakdowns that could have been contributing to the high ground leakage currents.
For this system, the VFDs were part of the problem, but repairing or replacing them wasn’t the total solution. To truly fix the problem and mitigate the risk of failure for the hospital as a whole, the issues with the electrical power distribution had to be addressed before they caused damage to diagnostic equipment or otherwise interfered with patient treatments.
Is It Time for a Second Opinion?
Don’t let power quality problems go undiagnosed, causing damage not only to your medical equipment, but to the electrical assets of your facilities themselves. To keep safety hazards from developing and ensure compliance with Joint Commission, National Fire Protection Association, and Occupational Safety and Health Administration standards for healthcare facilities, it’s important to heed the advice healthcare providers give their patients: listen to the warning signs.
When medical devices, computer systems, or other equipment experiences failure, it might not just be that equipment. Talk to a facility solutions partner with expertise in both the equipment and the power assets your staff and patients rely on.
Christopher Smith is a general manager at ABM Electrical Power Solutions. Questions and comments can be directed to 24×7 Magazine chief editor Keri Forsythe-Stephens at [email protected].
So Power Quality is an old school problem that has been with us since the dawn of the medical electronics age.
Power quality monitoring and troubleshooting is one of the great skillsets BMETs should have IMHO. it can really pay big dividends.
Jude Russell from https://powerlines.com/about is the real subject matter expert on power quality issues in healthcare. I recommend her highly.
For me, where I once worked we had a 60+ bed installation of networked patient monitors and central stations. Each monitor and central and network node point was protected by an ONEAC 1:1 transformer or a UPS with an 1:1 isolation transformer on the output. Both line and ground was isolated off the grid. My Spacelabs rep was always amazed that I had almost zero electronics failures. I followed the Novell Network guidance white paper for power quality in distributed computing systems to the letter. as a result over time I more that paid back the costs of paying $300 per device for the ONEAC units. I did the same with my Gama Cameras and saw similar reductions in failures. look for articles and guidance published by Judith Russell from Powerlines. Also when a cord cap is present, never forget to give it a good shake and listen for rattles, I cant tell you how many times over the years I have found loose lugs disconnected grounds, broken and mis wired connections etc. There is a lot more to power quality than simply plugging stuff into a UPS.
learn how and why your hospitals power system works. at the very least a good Biomed shop will have an Ideal Outlet tester, A woodhead receptacle tester and a good clamp on ampmeter with a current shunt to test basic power quality issues. BMI/Dranetz makes a decent power line analyzer too.
Back in the early 80’s when I was learning to be a BMET, my Mentor always swore that power needs to be monitored. He would always demand a 1:1 transformers for all of the Central monitoring stations in all department that had the. We almost never had a down from a power supply issue. .
Since the advent or switch mode power supplies have in the late 50’s the basic power supply was going to be phased out. Hitting it strong in the late 70’s. There had been a noticeable harmonic noise causing a power imbalance for older LIM systems on the ground. “My understanding it was for removing the spark potential due to flammable anesthetics gas” because of no WAGD systems.
Seeing an imbalance we would get alarms for what seemed to be no reason. They would shut off the equipment and the alarm would clear. We would analyze all equipment in the room looking for the unit causing the problem and not find it. We were looking for high ground leakage not harmonic noise. The LIM systems had to be updated. We stopped finding tape on the alarm silence buttons.
Shaking the replaced ground cord caps plugs is one of the first thing I teach all of my people.