isp start up & training guide

of 4 IPS Training Guide Rev 02 03-03-14.docx

Isolated Power System Training Description Isolated Power is an un-grounded power distribution system which is isolated from the grounded service supplying power to the facility via a hospital grade isolation transformer. Isolated Power Systems protect patients and attending personnel from electric shock caused by common ground faults, while maintaining power to critical electro-medical equipment. Typical grounded distribution systems provide electric service to outlets and fixed equipment via Hot, Neutral, and Ground conductors. The Neutral conductor is bonded to earth ground at the panelboard, which results in zero volts of potential between these two points. The Hot conductor however has a potential of 120V referenced to ground. Therefore, if a fault were to develop between these two points, a significant amount of fault current would be allowed to flow through the ground plane and back to the voltage source via the neutral-to-ground bonding connection. The consequences of this could be quite severe if a person were in the current path. In an Isolated Power System neither of the two current carrying conductors (L1 or L2) are bonded to ground. In a perfectly isolated system, there would be infinite impedance between both of these conductors and earth ground, thereby resisting all flow of ground current. Even if one of the two current carrying conductors of an ideal Isolated Power System were shorted directly to ground, no hazardous fault current would be allowed to flow because it is blocked from returning to the voltage source by the infinite ground impedance of the opposite conductor. This situation is referred to as a first fault and is the main safety feature of Isolated Power Systems. Only if a second fault were to occur, simultaneous to the first on the opposite conductor, would a path exist to allow dangerous fault current to flow. Isolated Power Systems that experience a first fault may be seen as being grounded (or partially grounded), as the fault path acts like a neutral-to-ground bond.


In addition to protecting patients and personnel against electrical shock hazards, properly designed Isolated Power Systems also ensure that normal supply of power to critical medical equipment is not interrupted due to a the occurrence of a ground fault. Similar to Isolated Power Systems, ground fault circuit interrupters (GFCI) are designed to protect against ground faults. However, they do this by disconnecting power soon after an actual fault current is detected. The affected circuit cannot be re-energized until the fault is located and cleared. This makes GFCIs impractical for use on Critical Branch Circuits. With an Isolated Power System, fault protection is afforded by limiting the ability of dangerous fault currents to flow in the first place. Therefore it is not necessary to shut down power to the system and critical equipment remains energized even in the event of a first fault as described above. Since there is no perfect insulation material having infinite impedance, we must consider the relative levels of leakage current that are present in all wiring systems and devices. Leakage current is a measure of the amount of current that leaks or escapes from an electrical circuit to ground during normal operation, and is due to poor insulation resistance and capacitive coupling between live conductors and ground. Facility maintenance staffs, as well as Bio-medical and Clinical Engineering departments are familiar with the concept of leakage current. Medical grade equipment is specially designed with low leakage supplies, and regular testing confirms that this has not been compromised due to age or damage. When applied to an Isolated Power System, leakage current is referred to as hazard current, and it accumulates across the entire system. In other words, the more wiring and equipment connected to the IPS, the higher the hazard current. The use of the term hazard current is intended differentiate it from leakage current which actually flows in grounded systems. Hazard current is a calculated prediction of the amount of current that would flow in the event that a second fault develops on the isolated system. It is calculated using the measured line voltage and ground impedance of the system. The primary concern of designers, installers, and operators of Isolated Power Systems is to keep the level of hazard current as low as possible. All Isolated Power Systems employ a special device known as a Line Isolation Monitor, or LIM. This device constantly measures the line-to-ground impedance of both isolated line conductors. Since hazard current is inversely proportional to ground impedance, the LIM calculates and displays the Total Hazard Current (THC) of the system. If the THC exceeds 5mA, an audible and visual alarm is initiated to warn that a first fault has occurred on the system. This signifies that an un-safe fault current could begin to flow through the system if a secondary fault occurred, providing a path for this current. Activation of the LIM alarm does NOT indicate that dangerous fault currents have occurred, only that one layer of protection has been compromised and the potential for this now exists. Operation Refer to instruction manuals and record drawings provided with equipment for basic operation. Additional copies are available by contacting our Customer Service Department [email protected]. In the event of an alarm, the following steps should be taken:

Do not panic. Alarm does not mean that there is imminent danger. Do not endanger patient by discontinuing procedure or treatment prematurely.

If possible, immediately notify personnel responsible for maintaining equipment (Facility Maintenance, Bio-Med, etc.). Many systems include remote alarm annunciators located at nearby nurses station. Newer systems include remote monitoring and control software so that responsible personnel are notified immediately at their desktop and may begin diagnosing the problem without entering the procedure room.

If it is clear that alarm is directly related to a particular device, disconnect that device from the system. Depending on the nature of the device however, this may not be possible. For example, critical equipment being used for treatment or life-support should not be disconnected if this will endanger the patient.

Once the procedure is completed and patient has been safely removed, responsible personnel should conduct a thorough review and correct the cause of the elevated hazard current prior to next case.


o Likely causes of alarm may include damaged wire or power cord insulation, liquid intrusion into energized equipment or wiring, or faulty equipment.

o If root cause is not readily identifiable de-energize all branch circuit breakers on affected isolation panel. Then energize individual breakers independently, one at a time, and observe the circuits relative hazard current contribution as displayed on the LIM. Identify which circuits contribute the largest amount of hazard current. This will narrow down the number of conductors and devices that may be associated with the alarm.

o Certain types of equipment are known to cause elevated hazard current in isolated systems. These include fluorescent and electronic lighting ballasts and some non-medical grade power supplies. Typical personal computers and monitors for example contribute relatively high hazard current due to simple line filtering circuits built into their power supplies. Devices with surge suppressor or TVSS circuits may also affect this. If practical, these devices should be removed from the patient care vicinity and powered from a standard grounded circuit.

Testing and Maintenance Isolated Power Systems require certain specialized testing as defined in NFPA 99 - Health Care Facilities Code Chapter 6 Electrical Systems. For newly installed systems, the following tests are required. This is performed by the isolation panel manufacturer prior to turning over the equipment from Contractor to Owner. The field technician will verify that systems are properly installed per all Code requirements and manufacturers recommendations. Equipment warranties are typically contingent on this service being performed by the manufacturer or authorized representative.

Line-to-ground impedance is verified to be > 200k. For a 120VAC system, this equates to a hazard current of 0.6mA. This test establishes the baseline hazard current of system (panel and branch wiring) before any equipment plugged in.

The integrity of the equipotential grounding connections is also tested at this stage. o Resistance between reference ground bus (inside isolation panel) and receptacle grounding points is

verified to be < 0.1 o The touch voltage of all conductive surfaces in the patient care vicinity is verified to be < 20mV.

The operation of the LIM is verified by successively shorting each of the line conductors to ground through a specific resistance that will produce a hazard current of 5mA. The value of this resistance is determined by the formula R = 200 x V, where V is the measured line-to-line voltage of the isolated system. The LIM should respond with the appropriate alarm.

Additional testing is also performed at this stage including verification of remote annunciator operation and visual inspection of branch wiring, and proper receptacle polarity. Isolated branch circuits should be low-leakage type XHHW wire and be brown and orange in color. Refer to NFPA 70 National Electric Code - Article 517.160 for specific requirements on installation.

After any modification, repair, or renovation of a previously installed Isolated Power System, NFPA 99 requires at a minimum, that the operation of the LIM be re-verified with the resistance fault method identified above. Note: Do not perform this test when patients or other personnel are present. Adding or modifying a Line Isolation Monitor, transformer, circuit breaker of wiring is considered a modification of the system and therefore requires re-testing. It is highly recommended that the systems Fault Hazard Current and grounding system integrity of the area be re-verified as well. NFPA 99 also requires regular ongoing testing of Isolated Power Systems. Systems with older analog style LIMs (identifiable by mechanical dial ammeter) require monthly testing. Modern digital LIMs with self-testing and self-calibration capability (including the PGL Mark IV & Mark V) require annual testing as opposed to monthly. At a minimum this test entails pressing and holding the Test button on the front of the LIM and verifying that THC operation of the silence feature mutes the audible signal, but that the LIM remains in the alarm state according to the visual indicators. Unit should return to normal operation once Test button is released. (Unit may undergo calibration prior to resuming normal operation). If present,


remote annunciators should also be tested with the LIM. NFPA 99 requires that a permanent record be recorded for each test. Any failures of this test should be documented and referred to manufacturer for analysis and repair as necessary. Again, it is highly recommended that additional inspections be performed annually by qualified personnel to verify these critical systems continue to operate safely and reliably. In addition to the minimum annual testing requirements required by NFPA 99, it is recommended that the following tests be performed on a regular basis (typically every 1-3 years).

Measure and record system hazard current and ground impedance Verify proper receptacle ground resistance and accessible surface touch voltages Externally verify LIM alarm point with resistance fault method described above

PGL offers a full range of testing services. Valid maintenance contracts may include free extended manufacturers warranty. Contact PGL Field Service for more details 800-287-4123. As well as the shorter interval between required tests, it should be noted that older Line Isolation Monitors, including ground detectors and units with 2mA alarm thresholds can cause nuisance alarms and are difficult to maintain and repair because of component part obsolescence. Also, these units should only be repaired and/or re-calibrated by the original manufacturer. Work performed by unauthorized personnel can void UL and other safety certifications. PG LifeLink offers custom retro-fit options to upgrade outdated monitors to the latest technology, including onboard logging of alarms (with time/date stamp) and unique LIM-Connect networked monitoring software. Conclusion When properly applied, Isolated Power Systems provide a vital layer of protection for patients and staff to safeguard against electric shock hazards and unintended shut-down of critical equipment in situations where human life is most vulnerable. In the event of a first fault alarm do not panic. Safely complete the procedure and remove the patient from the area. Ensure all situational details leading up to the alarm are properly communicated to the appropriate maintenance individuals, and then identify and repair the source of the alarm before additional cases are performed. Testing requirements are defined in NFPA 99 Health Care Facilities. Testing is required for new installations, after any renovations, and at regular intervals. Regular annual testing is required and offered directly through the manufacturer. Be sure to read and understand all instructions and manuals provided by the system manufacturer and consult the factory directly if any malfunction or test failure occurs.

For additional information or to obtain a quote for Annual Testing Services call Customer Support toll free at 800-287-4123

or email [email protected]

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