about ?SOLATED power systems
about ?SOLATED power systems
(OP)
hello, I wonder if we must bond İSOLATED Power system common earth bus to the main grounding busbar of a hospital or just earth this common IT EARTH bus to directly? which one is true. can u explain for me the final stage of earthing of the IT systems....






RE: about ?SOLATED power systems
RE: about ?SOLATED power systems
RE: about ?SOLATED power systems
The data systems' isolation is where the receptacle device has an isolated ground terminal that has an isolated grounding conductor connected to it, but which is isolated from the equipment grounding path that bonds the outlet box, conduit, panelboard can, etc.... This isolated ground conductor which terminates at an isolated ground terminal bus in the panelboard which is not electrically bonded to the panelboard can, but which is routed back through the distribution system all the way to the service entrance where it is bonded to the equipment grounding system. So a typical circuit run would include an ungrounded, current carrying conductor, ('hot' conductor-color coded); a grounded circuit conductor, ('neutral' conductor- usually white), and equipment grounding conductor, ('ground'-usually green); and an isolated ground conductor, ('isolated ground'-we use green with oranges stripe).
An isolated power system in a hospital setting is one where the neutral conductor is routed through the second pole of a 2-pole circuit breaker and the ground leakage currents are monitored by a line isolation monitor that trips the system with the slightest indication of leakage current.
We used to put these in all OR's but they are rarely used now as the use of flammable anesthetics has fallen out of favor with most of the surgical community. Current high tech hospitals we have done in the past 15 years have not been equipped with these.
RE: about ?SOLATED power systems
RE: about ?SOLATED power systems
If you have an isolated power system wherein the neutral conductor and the ungrounded conductor of each circuit are protected by a circuit breaker and a line isolation monitor. ANY fault seen by the LIM is immediately interrupted. No current can flow and all conductors are de-energized.
If by some odd occurance there is a fault between the ungrounded conductor and some other ground point, whether it be the equipment bonding conductor, an equipotentially bonded surface or conductor, or a piece of equipment, and the LIM sees current on the ungrounded conductor, but not the return path, then again the LIM will trip the circuit and de-energize the circuit and patient and personnel are protected.
I hope this helps. I have no idea what you mean by "the latest stage of grounding". The way we install the equipotential grounding system in an OR is by providing a Room Reference Ground Point. Which is a ground bus in a small panel where all grounding in the room is bonded to one point. The ground conductors from every outlet-normal and emergency, metal box covers, equipment and bed frames, med gas column or headwall unit, all grounding jacks, everything that may come in contact with the patient-is bonded together. I don't know if I am addressing the specific question in your mind. I hope so.
Regards,
EEJaime
RE: about ?SOLATED power systems
yes all the equipments made equipotential by bringing all them to the ground on the panel right? but what about bonding this bus? we make it tied with hospital basement earthing system or we earth it seperately with an electrode seperately or we just leave it as it is? excuse me i am not so experienced about
RE: about ?SOLATED power systems
If you have any additional question regarding isolated power: design, function, testing ect. feel free to shoot me an email and i will post in forums if necessary
RE: about ?SOLATED power systems
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: about ?SOLATED power systems
"...LIM will trip the circuit and de-energize the circuit and patient and personnel are protected."
This is incorrect the LIM is a monitor not a contactor. The LIM will never de-energize the circuit... this is one of the main advantages for isolated power.
Think of it this way:
On a 1-ph system the LIM really only needs 3 connections to monitor. L1 (orange), L2 (brown), Gnd (green). There is no neutral. On a balanced isolated 120VAC system if you measure the voltage you should read:
L1-L2 = 120VAC
L1-Gnd = 60VAC
L2-Gnd = 60VAC
The LIM monitors the impedance (Z) value between L1/Gnd and L2/Gnd. The lowest value between the two is taken and the current that could flow from L1/Gnd or L2/Gnd is calculated (I=V/Z) and displayed on the LIM.
If I was to take a piece of wire and connect Gnd to either, L1 or L2, the isolated power system would become a grounded power system, no breakers would trip and power would continue. The only way you would know that the isolated power system became a grounded system is the alarm of the LIM.
RE: about ?SOLATED power systems
What is the latest? The latest is in the NEC code and IEEE standards.
Let us separate the two issues. IT equipment (or so called orange isolated grounding receptacles) and the isolation transformers used for Operating Rooms (OR). Those are two totally different applications.
1. For IT or computer equipment grounding refer to IEEE- Emerald Book for sensitive system grounding. It is very clear there there is not need to argue. For those orange receptacles called isolated ground receptacles needs to be installed per NEC 250.146. This isolated grounding method is NOT ungrounded nor do they call for two separate grounding systems. Eventually all grounds are bonded to the service grounding electrode system. There is no such thing as isolated IT earth permitted.
2. For Operating Rooms (OR) isolating transformer, NEC 517.160 and other related sections there. The secondary of OR isolation transformers can be ungrounded (it is optional), but there is still an equipment grounding conductor that needs to bonded to equipment enclosure and system grounding bus (electrode), see NEC 517.19(E)and (F). LIM alarms on the first ground and depending upon the nature of the second ground OCPD of those secondary conductors could and shall open. The first ground makes the system grounded, hopefully limiting the leakage current as stipulated in the NEC. Plus the isolation transformers and LIM systems need to meet other criteria in the NEC 517 and shall be approved for such use.
Here again, there is no separate grounding electrode system permitted. Do not confuse ungrounded systems with isolated systems.