isolated power system hospital (LIM)
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- Опубліковано 23 вер 2018
- isolated power system hospital (LIM)
It sounds like you're referring to an isolated power system (IPS) in a hospital setting. An IPS is a critical component of hospital electrical infrastructure designed to minimize the risk of electric shock to patients and staff, as well as to ensure the continuous operation of essential medical equipment in the event of a fault in the electrical system.
An isolated power system typically consists of:
Isolation Transformer: This is the key component of the system. It electrically isolates the power supply from the grounding system, reducing the risk of electric shock. It also helps to minimize the spread of electrical faults.
Monitoring and Alarms: The system usually includes monitoring devices and alarms to alert staff in case of any faults or abnormalities in the electrical system.
Ground Fault Detection: This feature detects any leakage of current to ground, which could pose a risk to patients and staff, and it can quickly disconnect the power to prevent harm.
Backup Power: Many IPS setups include backup power sources, such as generators or uninterruptible power supplies (UPS), to ensure continuous power supply in case of a mains power failure.
Compliance with Standards: IPS setups need to comply with relevant electrical safety standards and regulations to ensure they provide the necessary level of protection.
In a hospital setting, IPS is particularly important because patients may be particularly vulnerable to electric shocks, and the continuous operation of medical equipment is critical for patient care. It helps to ensure that essential medical services can continue even in the event of electrical faults or power outages.
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I'm very sorry about the quiet audio. This was recorded during surgeries and I was being courteous.
I received a call that an EVS worker got shocked on a bed. They clearly reported on the work order the green wire broken on a side rail. Inspection found a broken ground wire on a Hill-rom bed. They pointed it out. It was static electricity cause we have a dry climate and static is frequent! A frequent call at my facility. Great video!
Many beds have a dangling chain which dissipates static buildup.
Very clear explanation. Thanks!
You're welcome.
Thank you for the simple, yet informative explanation. Got a really good idea about how LIM works and how it reduces the risk of electrocution without breaking the circuit.
Excellent explanation! Thanks very much..
Thank you.
I did not know this, Thanks
We opened an isolated electrical panel the other day after the alarm went off. Turned out that the lug-nut was loose and arcing inside the panel. Melted a bit of plastic.
We thought the lug-nut was some sort of hi-tech breaker at first, till we realized it was just a lug-nut.
Very informative video! Sounds like it is quite hard to ground one-self in this environment.
Its easy to ground yourself (remove your body's potential charge) but it's difficult for electricity to move from any outlet to you (ground potential).
Thanks for the video
Thanks for watching!
Nicely done.
Thanks. I think I should update this video to get a little better quality. This was the first video I recorded for this channel.
@@BetterBiomedChannel For a first attempt you did great. Could you add an explanation for how the transformer core ground which appears to be at the same potential as the main supply ground doesn't create pathway to a shock. This part had me wondering until I saw there was no return pathway to the isolated windings. Some folks may not see this so clearly. They also need to know that a regular transformer may have the core grounded to the supply side in some instances. From your experience would this create a shock risk?
I'm a little late to the game, but I just want to say great video from an electrician studying to become a biomed.
Thanks
I find strange that people can confuse static with an electric shock. Static is a short pulse and once it is done it is over. An electric shock would be constant current. A static shock can be several amperes so it fill feel - even painful but as it is so short it is not dangerous.
The general population has little idea about electricity or of static. Most people have never been zapped by AC mains. Any electrical sensation is automatically associated with AC mains because that's humans in a nutshell...
Nice diagram and explanation! But it looks like I need to learn more in order to understand how an isolated winding can be referenced to the ground!
There are 2 types of isolation transformers. One type (the cheaper version found in many equipment carts and eeg labs) is just a noise isolation transformer. The second type is a mains isolation transformer which I depict here. The mains iso transformer has no continuity from the secondary to the primary which is why you won't get shocked. The noise isolation type does have some continuity and you can get shocked. The easiest way to tell is unplug the transformer, put your multimeter on ohms or continuity mode and test between the primary and secondary
@@BetterBiomedChannel thanks a bunch 😊
Very good explanation, thanks! But there is still a query about if IES is good for device. I encountered many case that an operating microscope crashed from time to time. After skipping the IES, then put the device on primary side of transformer, problem was solved. I don't know why. I guess it depends on if the power supply module of device was designed to adapt IES.
This is an interesting situation.. I would have loved to document that failure. For most devices that run on DC regulated power supplies (which is most), it will never matter because the AC is converted to DC immediately after entering the chassis. A medical grade power supply tends to have chokes and filter caps on both Line and Neutral that comes into the power supply (which is why they usually cost more). If a microscope pc is crashing you should check the electrolytic caps on the motherboard next to the processor. Older microscopes have bulging and leaking capacitors which creates unstable power at the processor (causing random crashes).
This is an EMC problem. There is a well known rule. "Meeting a safety requirement" means violating good EMC practice. In your case, ESD was probably crashing the equipment because static charge may have had no way to drain off into "ground", especially if this microscope had only a two pronged plug.
What was the OR humidity level? 40%
Is there a type of external UPS device that would work in this system? One that could plug into a receptacle without alarming ?
A ups should work fine but most isolated power circuits are on emergency power or facility ups power
When we plug in a ups the current rises on the LIM panel and alarms out. There is a delay on our emergency power and we wanted to use the ups to fill in for that delay time.
what's happen to the electricity in the frame of the device when u get shock bc of changging magnetic field of ac? where does this current go? how circuit complete?
If I understand your question correctly, AC will induce a magnetic field into conductors - that field is also AC bidirectional current. Medical equipment is designed specifically to reduce emf leakage. There is chassis grounding, switch mode power supplies with extra shielding, and extra emf filters. All conductors should be as short of a length as possible (not coiled up), and devices with a common ground need to be plugged into a single power strip to prevent ground loop.
good morning.
amatuer electrician here. question. i'm confused.
abt each wire delivers 60v. but the appliance you plug in expects 120v from hot wire and a zero volts neutral in the male plug.
or is this situation changed via the transformer.
Tia.
It's AC not DC. The current is alternating back and forth so the device is just looking for a difference of potential between the two points. Which is 120V AC
A nurse just broke down an ungrounded system better than every journeyman electrician you know. What does that tell you.
So how would you test devices in the OR if these are your only outlets available?
Most modern electrical safety analyzers recognize isolated power
@@BetterBiomedChannel I Have seen this with the analyzer I'm using (I'm using Vpad) and I've just always used a regular outlet, instead. I'm curious though, on the analyzer I'm using, it says test results may not be accurate. When testing leakage current I would get different readings when plugged into the isolation transformer vs a regular 120 outlet. It doesn't seem to fail but the readings are different, I'm interested in your take on this? Or have you experienced something similar?
The whole purpose of an isolated power system is to eliminate the direct association of line AC power to ground. Because of this, there will inherently be lower numbers for leakage in an isolated system because the power want to travel back to the iso transformer not ground.
The transformer is about not getting shocked from lightning strikes etc. Not about protecting from faulty equipment; the meter though, yeah, it can help. I man yeah, lower voltage, lower shock, but I don't buy the rest.
Isolated power systems have little to nothing to do with lighting strikes and everything to do with single fault electrical hazards, which could normally shock. Lighting strikes can transmit surge and noise through a transformer.
What do you mean about 60VAC? Measure between which two points? It should be 120VAV between L1 and L2, right? mA meter let you know L1 or L2 is grounded.
Its 60V AC between L1 or L2 and GND. Which can give some safety meters a fail condition (older meters). mA meter is for leakage between either L1 or L2 and ground. It doesn't tell you anything about the quality of your ground. -That is done by ground balance testing of the room.
It is probably ground referenced through capacitive coupling to the grounded frame in the transformer. Effectively center tapping the transformer. That's where the tiny current comes from as AC is flowing through this parasitic capacitance to ground.
@@stargazer7644 It's simpler than that. See my reply above.
There is an error in the diagram and explanation at 2:35. You can clearly read the nameplate of the panel at 0:53 where it states the Input volts is 277V (not 120V as in the diagram ).
Another error is in the right half of the diagram. There has to be 120V at the receptacles for anything that is plugged in to work properly. But if L1 equals L2 = 60V as noted, then the measurement between those points is going to be 0 Volts, which of course is not true.
Redraw the input side as 277V and either put +/-60V and -/+60V on the L1 and L2 leads or just write 120V AC and you should be fine. And BTW, I'm an Electrical Engineer.
"But if L1 equals L2 = 60V as noted, then the measurement between those points is going to be 0 Volts, which of course is not true." The voltages measured at opposite ends of a transformer are going to be 180 degrees out of phase with each other. Just as when you measure 120V on each leg of a residential panel, but when you measure across them you don't get 0V, but 240V.
Ask yourself in this circuit, what would you measure from L1 or L2 to ground? The simple answer is "nothing, 0V - it's an isolated system". But that's only true in a system with an ideal transformer. How can there be leakage to ground in an isolated system? Obviously there is leakage - the meter is measuring it. Real transformers aren't perfect, they have stray capacitance. There has to be a voltage difference from L1 and L2 to ground if there's current flowing. That's the 60V. The transformer is effectively center tapped to ground through the stray capacitance in the transformer, but the connection is high impedance, so not much current flows unless there's a fault.
Whether the input to the transformer is 277 or 120V is really rather irrelevant to what is going on here. It makes no difference on the isolated side.
Thank you Star Gazer for that perfect explanation.
Exactly. Some of panels are a simple 1:1 ratio with 120V primary. It's much easier to explain isolated power if explained 1:1 than including a step down transformer or isolating a single phase. What if the watcher of the video encounters a panel with different input power? It doesn't matter. I'm very surprised that an electrical engineer would request I label a transformer secondary as +/-60V. Anyone that understands transformers would know that it's only AC which doesn't have a +/- potential (unless you're talking @60Hz)..
The +/- 60V on the transformer is referenced to the isolated ground.
There is such thing as a floating ground or lifted ground but ground in an isolated electrical system is actually connected directly to the transformer chassis as well as system earth ground. There is no such thing as +/- 60V AC. It's just 60V AC. Anything could be on the primaries of a transformer but the secondaries are not tapped to any center leg in an isolation transformer they are isolated from everything. Noise isolation transformers do have a leg tied to ground. The secondary is one coil (isolated from everything). As you guys know, the number of windings in that coil = V of that coil.
How are you supposed to test them to comply with weekly or monthly test, besides the probably self test in the monitor.
Thanks
There is a test button on most LIMs. The invasive test is once per year.
@@BetterBiomedChannel ok thank you so much! So what the invasive test does? Does that have to be done by personal or a certified approved company?
Neutral is bonded to "ground" on the mains side (in the US/CAN)..why not show that.
Because the drawings is dramatically simplified. The neutral and "bonded" ground have no effect on subject of isolation.
@@BetterBiomedChannel I think it will confuse most people. Then there is an issue of a 240 volt panel with line 1 and line 2. I also think it should be pointed out that the reason for the monitor is to detect a neutral to ground short in anything connected to the panel output....
you don't need an isolation power in an operating room....because there is no way to get electric shock in my life as i am an electrician working with all hazardous electricity.. i don't know why operating room have isolation transformer.... wasting money.... let me say a tale " what happened if the sun not fire one day " or what happen if an earthquake in that operating room .... these are over protection. But if it is to minimize electromagnetic interference that makes sense.
Operating rooms do not need an isolation transformer if built after 1986. But as a remodel or expansion, the transformers need installed if other parts of that facility currently have them installed. ORs are a wet location and a clear electrical hazard by anyone's definition. The people in ORs for surgery are not the healthiest people in the world in the first place. "An ounce of prevention ..."
How much do I owe you for that, Doctor? 6 minutes 29 ... let's call it $800 even?