Eglin AFSC Regional Hospital Eglin Air Force Base

Ft. Walton Beach, FL 32549

Ultrasound Equipment Power Audit

Report Prepared by: Phasor Corporation

October 2012

210 Division St., Suite 7, Kingston, PA. 18704 Phone: (570) 331-0502 Fax: (570) 331-0761

Introduction & Executive Summary

Preliminary Findings/Reports

Photos

Electrical One-Line Diagrams

Overview & Corrective Actions

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I. INTRODUCTION & EXECUTIVE SUMMARY

Phasor Corporation was contracted by LINC Government Services to investigate a potential power problem with their Ultrasound equipment,namely a Phillips Ultrasound model iU22 (see statement of problem section 2) located at the Regional Hospital, Eglin Air Force Base, Ft. Walton Beach, FL.

This document will provide a complete synopsis of the power investigation and a conclusion with recommended corrective actions. Please note that the power investigation involves distributed voltage to rooms 1N024.2 and 1N026 (mammography) as well as somegeneral discussion concerning power quality at the main electrical service.

Executive Summary In an attempt to supply additional critical load circuits to rooms 1N017 and 1N024.2, one phase of a three phase system was diverted to the nearest critical circuit supply. The re-routing of the supply from non-critical to critical load panels created an imbalance that caused circulating currents to flow between two different supply transformers with separate derived ground systems. Load currents of 6 to7 amps should have had a 6 to 7 amp return on the neutral wires as part of these single phase circuit connections. Instead 2 amps was measured on the neutrals with the remaining current circulating over various ground paths eventually returning to their respective supply transformers. These connections were re-wired to allow normal operation. It is believed that this condition was the main cause of artifact interference seen on the Ultrasound equipment. There are at least three additional items of concern, one being harmonic resonance and additional ground current loops due to the non-standard neutral to ground connections. Phasor Corporation continued to check for ground loop currents, and began to find current levels on the ground system that suggested additional areas of concern with indications of neutral return currents showing up on the electrical equipment safety ground circuits. Following this back to the main service supply switchgear, significant levels of current on the equipment safety ground conductors was measured, when there should have been, at most, a small level of induction current. This condition needs to be corrected and further interference investigation should not proceed until after the necessary repairs are made. The second item of concern is the harmonic current levels, which in and of themselves may or may not cause device interference. What was seen was typical of load currents we see today due to switching power supplies and other electronically controlled loads. These currents may cause interference between any two devices but is usually not a problem unless the supply voltage shows a high level of distortion as a result of these currents. The voltagetotal harmonic distortion was measured at 1.2 to 2.6% at distribution panel 1KLC2, well below the action level suggested by the IEEE of 5%. Lastly, the iU22 Ultrasound unit should have an isolated, dedicated circuit supplying this machine.

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Diagnostic Equipment Used:

(1) Fluke Model 1735 Power Quality Analyzer (2) Dranetz Model 4400 Power Quality Meters (1) Fluke Hand Held DMM, True RMS (1) Hand Held, True RMS Clamp-On Ammeter

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II. PRELIMINARY FINDINGS / REPORT Project: Eglin AFSC Regional Hospital Location: Eglin AFB Hospital, Ft. Walton Beach, FL 32549 Date: 10/26/12 Preliminary Outline: OBJECTIVES:

Phasor Corporation’s mission was to determine the root cause of an artifact present on the Phillips iU22 Ultrasound Equipment (please see statement of problem below).

Determine if the electrical supply to the rooms utilizing the Ultrasound equipment meets the manufacturer’s requirements for electrical service as outlined in “Phillips Corporation, iU22 Ultrasound System User Reference Document 45361170891 Rev. A, June 2004.”

Statement of Problem: Ultrasound equipment in use at the Eglin AFB hospital continues to have problems with the Philips HD22 ultrasound imaging system. Artifacts appearing on the screen affect the quality of analysis and in some cases to a level that precludes any possible diagnosis. These artifacts appear to be RF noise interference interlacing that creates distortion in the image. Specifically two examination rooms, room 1N024.2 (Called room 1) and room 1N026 (Called room 3) were in question. The artifact problem with the Ultrasound equipment was worse in room 3 than in room 1. Room 3 operation has improved, due to replacement of the Philips unit with a new GE unit that has not exhibited the problems seen on the Philips iU22. This is most likely due to different technology used for the power supply within the GE unit. The Philips machine in room 1 still exhibits the artifact interference. The problem is not limited to a particular time of day and has appeared in various degrees any time the unit is used including nights, weekends, and normal daytime duty hours. Personnel Interviewed: Sargent Fredrick Gumm Bien May - 850-883-8511 Samuel Radford – 850-486-6042 Randy – 850-486-6042 Herb Harrison – 850-441-0040

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Notes: Room 1N024.2 The Philips HD22 is attached to a duplex outlet identified as an emergency power outlet, marked “1NKLC@-14” (circuit #14), which is supplied from power panel 1KLC2-1, circuit breaker #14. Phasor Corporation traced this circuit and confirmed that it is the supply circuit used in room 1N024.2. However, it was noted that the panel schedule of circuits indicates circuit breaker #12 as the supply circuit to the ultrasound equipment in room 1N024.2. The duplex outlet marked “1NKLC2-12” (circuit #12) exists in room 1n024.2 but was not used to supply any equipment in the room. Phasor moved the power bed to circuit #12 and left the ultrasound unit attached to circuit #14, since the ultrasound unit is supposed to be connected to a dedicated circuit as per the manufacturer’s instructions. Room 1N026 The GE ultrasound unit is connected to a power conditioning unit, which in turn is connected to a duplex outlet identified as an emergency power outlet, marked “1NKLC-19” (circuit #19). This circuit is supplied from power panel 1KLC2-1, circuit breaker #19. As the load was measured on this circuit, 6 amps of current flow wasrecorded. An attempt was made to locate the neutral for this supply it was discovered that there was no neutral return for this circuit in the panel. Following the circuit supply, it was further determined that this circuit was originally supplied from power panel 1KL4. This panel was not part of the emergency supply circuits and it became apparent that the change was made in order to place the outlet marked 1NKLC2-19 in Room 1N026, on an emergency supply. Additional concerns here are that the original supply from power panel 1KLC2-1 was from transformer T-1KL3 which has a separate derived neutral. The emergency supply power panel 1KLC2-1 is supplied from transformer T-1KLC1 which uses its own derived neutral. By supplying phase current from one source and ground return from another source, a series of ground current loops has been established. This type of installation does not meet NEC requirements and can cause numerous operating problems throughout the facility for circuits supplied by these two panels. This situation also creates a safety hazard for personnel working in this panel.

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Partial Diagram of the Power Supply Circuits

1KLC2-1

Figure #1 – Partial Diagram of the Power Supply Circuits to Rooms 1N024.2 (Room1) and 1N026

#14

#19

1KLC2-19

480V Delta – 208Y/120 Wye 4 wire 45 kVA, 3.96%Z, S#-J04J06592

1KLC2-14

Room 1N024.2

480V Delta – 208Y/120 Wye 4 wire 30 kVA, 6.20%Z, S#-J04D06011

1KLC1-1

Room 1N026

1KL4

T-1KLC1

T-1KL3

1KL4

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Comments:

The connections as they exist set up a circulating ground current between the returns of the transformers in the preceding diagram. This is an excellent source for interference and overall power quality problems. The plan at this time is to rewire the circuits to their original state, i.e., 1KCL2-19 will be returned to power panel 1KL4 on Wednesday evening (10/24/2012) as Phasor Corporation continues measurements of the various circuits in question. October 26, 2012 Update: On Wednesday 10/24/12 at 18:30, LINC Government Services performed preliminary corrective actions, in room 1K018. The phase wires from circuits 17 & 19 from panel KLC2 were moved from panel 1KL4 and returned to their original positions in panel 1KL4 as per original design. Phasor Corporation continued monitoring circuits from Panel 1KLC2 and panel 1KL4 after the relocation. On Thursday 10/25/12 at approximately 11:00, the monitoring equipment was removed from panel 1KL4. Monitoring on panel 1KLC2 was continued. After reviewing the electrical single line diagrams on drawings E6.1 through E6.15, the monitoring equipment was placed on switchboard H-NMSWB1 located in the basement. Specifically, the neutral to ground voltage & currents were measured on the main supply neutral and ground conductor from the secondary unit substation (SUB1), from distribution section #2 which is supplied from transformer MT2. In addition to the preliminary findings mentioned above, Phasor Corporation discovered additional issues concerning ground current in switchboard H-NMSWD1, indicated in the graph below. It appears that the ground conductor is connected in parallel with the neutral conductor, as seen in the graph below.

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The ground conductor is designed to carry fault current back to the source in the event of a phase conductor coming in contact with metal surfaces or equipment, such that it may present a safety hazard to personnel. See NFPA 70 (National Electrical Code) definition below:

250.2 NEC Definitions.

Bounding Jumper, Supply-Side: A conductor installed on the supply side of a service or within a service equipment enclosure(s), or for a separately derived system, that ensures the required electrical conductivity between metal parts required to be electrically connected.

Effective Ground-Fault Current Path: An intentionally constructed, low-impedance electrically conductive path designed and intended to carry current underground-fault conditions from the point of a ground fault on a wiring system to the electrical supply source and that facilitates the operation of overcurrent protective device or ground-fault detectors on high-impedance grounded systems.

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Next Steps:

Recommendations will be provided based upon information collected at the site and data analysis.

o Review system bonding and grounding connections throughout the electrical distribution system.

o Extend dedicated circuits to the Ultrasound equipment as per manufacturer’s specifications.

o Install UPS equipment for Ultrasound devices that are presently on Life Safety circuits.

o Install UPS equipment for the servers in room 1N017 to insure access to pertinent medical data.

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MEASUREMENTS AND INVESTIGATION Figure #2 is a partial wiring diagram of the supplies to Room 1K018 supplying the Ultrasound equipment in question. This diagram shows Test Points (TP#x) and Test Points Neutral to Ground (TPNG#x). This will be used as a reference for the discussions following herein to identify locations where Phasor Corporation placed recording equipment or performed specific tests.

Figure #2 – Wiring Diagram Showing Test Points, Load and Supply Circuits

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The test points in Figure #2 listed as TPNG# and shown in green are the locations where we took neutral voltage to ground readings and current readings on both the neutral and the ground conductors. Table #1 below summarizes these measurements.

Table #1 – Current Measurements of Neutral and Equipment Ground Conductors, Neutral to Equipment Ground Voltages

Test Points

Neutral to Ground

Panel Identification

Current

measured on the Neutral Conductor

AMPS

Frequency of Current measured

on the Neutral

Hz

Current

measured on the Ground Conductor

AMPS

Voltage Measured

Between the Neutral and

Ground Conductors

Volts TPNG#1 1KL5 0.05 300 0.24 0.072 TPNG#2 1KL4 15.2 60 0.33 0.067 TPNG#3 1KL3 20.5 60 0.42 0.053 TPNG#4 1NHDP - 0.13 0.029 TPNG#5 1NHDP 5.68 60 1.5 0.290 TPNG#6 1KLC2 9.75 120 0.76 0.076 TPNG#7 1KLC1 7.18 120 0.9 0.048 TPNG#8 1KHC1 3.70 120 0.08 0.201 TPNG#9 BHCDP1 2.75 60 0.09 0.063 TPNG#10 BHCDP1 8.75 60 2.90 0.063 TPNG#11 H-HCDP - - - 0.041 TPNG#12 ATS-C1 10.9 60 2.4 0.042

One of the most significant findings, on this set of spot tests in Table #1, are the higher than expected currents found on the equipment grounding conductor (highlighted in yellow). This is indicative of possible improper neutral bounding at various power panels or elsewhere in the building. In one case we measure approximately 7 amps flowing on the equipment grounding conductor for the T-KL2 and T-KLC1 transformer ground. We were not in recording mode when we saw this and were not able to present further evidence in Room 1K018.

This did however justify a review of the neutral and ground currents in the supply panels to Room 1K018,theseresults are shown in Table #1 above. Phasor expected to measure little or no current flow on the equipment ground conductors at any panel. Consequently we then monitored the Neutral current and the Equipment Ground current in the main supply switchgear in the hospital. A Fluke model 1735 was connected in a manner that allowed the measurement of the neutral and ground currents simultaneously in switchboard H-NMSWB1, the main 480 volt supply. Also installed concurrently at this location was a Dranetz 4400, set to monitor the three phase currents and voltages.

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The connections used may be seen in Photo#1. The Fluke 1735 red CT leads may be seen connected around the equipment ground bus, lower right in the image, and around the neutral conductors. This is difficult to see since the neutral is located behind the phase conductors. The voltage leads were connected between the neutral bus and the equipment ground bus. (See Test Point TP#4)

The Dranetz 4400 was connected in a normal configuration monitoring phase and neutral currents, phase to neutral voltages,and neutral to ground voltages. (See Test Point TP#5)

The results (see figures 3,4,5,6,&7) of the testing done on the H-NMSWB1 main supply neutral and equipment ground bus revealed a problem that will require additional troubleshooting by maintenance or contracted personnel.

The recorded test measurements show that there is a considerable amount of current returning to the system neutral circuit via the electrical equipment ground bus. The electrical ground bus is intended to provide a safety ground system as mention above by the NEC for an “Effective Ground-Fault Current Path” that is used only for this purpose and is not intended to be a current carrying conductor under normal operation.

Furthermore, with this level of current flow on the equipment ground system, there is a strong possibility for the establishment of ground loop currents from both internal loads in the Hospital as well as ground currents flowing from outside the Hospital building from external sources, such as other nearby buildings. These currents may cause additional noise and load to be imposed on the system neutral causing sensitive equipment to operate erratically.

Typically, finding current flow on an equipment ground bus is not unusual, however in this case, both the level of the current and the fact that it mirrors the current flow found on the neutral bus, strongly indicates the existence of an incorrectly connected equipment ground on the system that should be removed.

Photo #1 – Main Entrance Cabinet in H-NMSWB1

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The following page shows the graph of our current measurements of the neutral and equipment ground bus. The equipment ground is carrying 30% to 50% of the total return current that should be on the neutral.

Figure #3 – Neutral Current and Equipment Ground Current shown on the same scale

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Figure #4 Neutral Current and Equipment Ground Current Scaled to Superimpose The Curves

The Dantez 4400 was used to monitor the phase and current levels on the main supply to H-MNSWB1 switchgear. There were no particular problems identified during this period of monitoring these phase currents and voltages. A graph of these measurements is included below to keep a complete record of measurements.

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Figure #5 Voltage Plots - H-NHSWB1 Switchgear

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Figure #6 Current Plots - H-NHSWB1 Switchgear

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Figure #7 - Total Harmonic Distortion Voltage Plots - H-NHSWB1 Switchgear

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Each of these are read in the following manner: The upper portion of any of these plots represents the maximum level that was recorded at least once during a recording cycle. The line shown between the upper and lower (lowest) portion of the graph represents the average value of all the readings taken during the recording cycle. The lower portion of the plot represents the minimum value that occurred at least once during the recording cycle. All recording cycles combined make up the entire plot shown.

Figure #7 shows the total harmonic distortion of the voltage for each phase. Looking at “C” phase, the highest VTHD is approximately 6.4 volts, or approximately 2.3%. This is within the normal levels identified by the IEEE standards.

Panels in Room 1K018

Room 1K018 contains the distribution panels supplying the problem areas of the Hospital operating the ultrasound equipment. Specifically, distribution panels 1KL4 and 1KLC2 in this room and supply power to three rooms of interest.

Room 1N024.2 – Also called Room 1, contains the Philips iU22 Ultrasound machine that exhibits artifacts on the output screen to varying degrees from none to complete interference. This is likely caused by interference from harmonics or loop ground currents and certainly could be caused by both. This room is supplied by circuits 12 and 14 in the 1KLC2 (critical supply panel).

The Philips HD22 is attached to a duplex outlet identified as an emergency power receptacle, marked “1NKLC@-14” (circuit #14), which is supplied from power panel 1KLC2-1, circuit breaker #14. Phasor Corporation traced this circuit and confirmed that it is the supply circuit used in room 1N024.2. However, it was noted that the circuit panel scheduleindicates circuit breaker #12 as the supply circuit to the ultrasound equipment in room 1N024.2. The duplex outlet marked “1NKLC2-12” (circuit #12) exists in room 1n024.2, but was not used to supply any equipment in the room. Phasor moved the power bed to circuit #12 and left the ultrasound unit attached to circuit #14, since the ultrasound unit is supposed to be connected to a dedicated circuit as per manufacturer’s instructions. Later it was found that both the bed and the ultrasound unit were plugged into the receptacle marked for CB #12. A suggestion would be, that the bed be placed on circuit #14 and the ultrasound device left on circuit #12,m as long as this does not create any type of safety issue with the patients being examined.

Room 1N017 – This room contains computer servers and acts as a central repository of medical data collected by the Technicians using the ultrasound machines in rooms 1N024.2 and 1N026. This room was supplied by circuit #17 from 1KLC2 critical supply panel. Note the discussion below for room 1N026 as it applies to this circuit. The circuit supplying the load in this room was transferred from panel 1KL4 and causes additional ground current looping in this configuration.

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Room 1N026 – Also called Room 3, contains a GE Model Logiqe9 ultrasound unit. This is powered by a PowerVar Model ABCE1440-11EC UPS. This room was supplied by circuit #19 from 1KLC2, critical supply panel.

As the load was measured on this circuit at power panel 1KLC2, 6 amps of current flow was measured. An attempt was made to locate the neutral for this supply, it was discovered that there was no neutral return for this circuit in the panel. Following the circuit supply, it was further determined that this circuit was originally supplied from power panel 1KL4. This panel was not part of the critical supply circuits and it became apparent that the change was made in order to place the outlet marked 1NKLC2-19 in Room 1N026, on an emergency supply. The additional concerns here are that the original supply from power panel 1KLC2-1 was from transformer T-1KL3 which has a separate derived neutral. The emergency supply power panel 1KLC2-1 is supplied from transformer T-1KLC1 which uses its own derived neutral. By supplying phase current from one source and ground return from another source, a series of ground current loops have been established. This type of installation does not meet NEC requirements and can cause numerous operating problems throughout the facility for circuits supplied by these two panels. This situation also creates a safety hazard for personnel working in this panel and on equipment attached to this circuit (Refer to Figure #1, Page 5 above).

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Distribution Panel 1KLC2

Phasor Corporation attached a Dranetz model 4400 unit to the supply side of this panel,please refer to Test Point TP#2. The general voltage levels and currents were reasonable, the next few pages show these values plotted by date and time. On the value of voltage level it appears that you could use a tap change to increase the output voltage of T-1KLC1 transformer, since the average voltage does run consistently low. Usually, Phasor prefers voltage levels within ± 5% of the nominal voltage, which in this case is 120 volts. The normal bandwidth would be 114 to 126 volts. Unless there is a specific problem however, the need to operate at a higher voltage is strictly a matter of choice. An advantage to operating at a slightly higher voltage is that it will reduce the current drawn by any motor loads, which may reduce noise caused by ground and neutral currents.

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Figure #8 – Voltage & Current Plots for Panel 1KLC2 First Time Period

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Figure #9 – Voltage & Current Plots for Panel 1KLC2 Second Time Period

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Figure #10 – Voltage & Current Plots for Panel 1KLC2 Third Time Period

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Figure #11 – Voltage & Current Plots for Panel 1KLC2 Fourth Time Period

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Figure #12 – Voltage & Current Plots for Panel 1KLC2 Fifth Time Period

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A difference may be apparent in Figure #12, as compared to previous figures reporting voltage and currents for Panel 1KLC2. The difference is due mainly to the change in capture settings that were placed on the Dranetz 4400. This was done in order to show some of the current waveforms captured during this study on Panel 1KLC2. The currents as shown below, Figure #13, is typical of the load current supplied by this distribution panel.

Figure #13 – Typical Load Currents on Panel 1KLC2

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Of interest here is that the non-sinusoidal currents for each of the phases create harmonic currents which is a natural occurrence of modern power supply systems. However, these currents can create resonant interference with some equipment and can be the source of “noise” on some devices such as the ultrasound systems. For this reason, a power conditioner or UPS system may be specified to protect a particular device. From Figure #13, the bottom waveform is the neutral return current and exhibits the effects of the 3rd harmonic. Typically, the phase currents sum vectorially to zero as all three phase currents are equal in magnitude. When harmonics are present, 3rd harmonic currents will add algebraically, as will the 9th, 15th, and any of what are termed the harmonic triplens. The magnitude of the third harmonic current is shown below on the following page as Figure #14.

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Figure #14 – Third Harmonic Currents On Each Phase

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The system voltage however shows very little effect in Figure #14, but since these currents are present on the system, as system loads increase the effects should manage to keep the distortion to 5% or less.

Distribution Panel 1KL4

Phasor investigated the loads and voltages, harmonics and load balance on Panel 1KL4 since it was originally the supply for room 1N026 and 1N017. The general harmonic level for voltages was well below the IEEE standards as shown in Figure #15.

Figure #15 – Typical Harmonics on Distribution Panel 1KL4

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Typical Voltages Currents and Load levels for 1KL4 are shown below.

Figure #16 – Typical Voltages on Panel 1KL4

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Figure #17 – Typical Currents on Distribution Panel 1KL4

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Figure #18 – Loads on Each Phase and Total Panel Load on 1KL4

Phasor Corporation collected additional data on 1KL4, but the plots above are typical of what was measured on 1KL4.

Overall, the significant findings should point out that there is a considerable imbalance in the load on the individual phase wires. This very obvious in Figure #18 as can be seen on the “C” phase load or “L3N (kW)”. The imbalance between phases also adds to the total neutral current on the system and is noted here as a possible source of future problems.

Photographs

Panel 1KL4-1, Monitoring

4.1 Panel HNMSWB1, Monitoring

4.2

HNMSWB1, Monitoring Equipment 4.3

Typical PPE Gear 4.4

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There exists a current imbalance in panel 1KL4 as well as other areas (distribution panels), in that phase ‘C’ is lightly loaded and is adding to the neutral current imbalance.

In additional to the problems found in the Mammography area, Phasor Corporation also discovered considerable ground current present at the main switchboard (please see page 11& 12). There was however, very little ground current detected in other areas of distribution in the hospital.

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Suggested Corrective Actions

Phasor Corporation recommends the following actions:

1. Rewire dedicated circuits for the Ultrasound equipment in rooms 1 and 3 (1N026 & 1N024.2) using dedicated neutrals and single (non-duplex) hospital grade receptacles. Further enhancement would include a high grade UPS.

2. Balance phase currents in distribution panels between ‘A’, ‘B’ and ‘C’ phases if possible.

3. Properly ground all transformers in the electrical closets, as per NEC article 250.30

4. Review ground scheme for externally mounted ground bars, in particular those found on drawing E6.10, ground bar PMGB-1. Verify that the grounding is installed as per the drawing.

5. Examine ground scheme at the main service to determine the source of ground current found in switchboard H-NMSWB1. This ground current, although detrimental to equipment operation, is also a concern to personnel who may come in contact with unexpected current on the ground system.