Sub-optimal Power Quality Can Cause Sensitive Medical Equipment to Fail

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Power Quality has always been a key issue for healthcare facility managers. With the rapid advances in medical technology, hospitals, medical clinics and laboratories increasingly rely on sophisticated electronic devices for diagnosis, treatment and monitoring. This equipment is often interconnected within networks, industrial processes and power infrastructure and can be negatively affected by events that arise both from the supplying power system and aregenerated within the facility.

All of the interconnection of electrical circuits, and the high sensitivity of the equipment in use, demands a high degree of power quality and reliability to prevent disruption of mission-critical operations and procedures. Power quality disturbances can be caused by a range of internal and external phenomena and often re-occur because the location and nature of the event is not well understood or identified.

The Dranetz PowerVisa

While the costs of downtime or failures can result in thousands of dollars per hour, the costs of power and equipment failures in critical patient operations are immeasurable. Power monitoring is key to maximizing uptime and ensuring all power infrastructure is functioning properly.

Manufacturing Process Unexpectedly Halted

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This medium-sized manufacturing facility, located in an industrial park that experienced an unexplained shutdown of several adjustable speed drives (ASDs) , wreaking havoc on key process equipment. Each day, at approximately 6 am, the utility-owned PF capacitor kicks on to improve the voltage of inductive loads prevalent in many of the park’s manufacturing facilities. The ASDs are conditioned to anticipate this expected power quality event and are typically able to ride through the problem. So when one of the ASDs closed down and interrupted the continuous stream manufacturing process, the facility manager needed to learn why, correct the problem, and prevent it from happening again.

As you can see from the attached screen capture, a second, unanticipated capacitor switching event occurred shortly after the first. This event was categorized by the Encore Series System Capacitor Switching Answer Module , enabling the facility manager to pinpoint the exact source of the problem. Further analysis showed that the ASD shutdown was the result of an overcurrent trip, which was quickly remedied preventing hours of downtime, at a loss of $10,000/hour.

SecuTest & SecuLife Safety Testers From Gossen Metrawatt

www.gossenmetrawattusa.com

The SecuTest SIII+ and the SecuLife ST are universal test instruments for testing the electrical safety of portable electrical equipment in commercial, residential, and medical applications operating at 120V/60Hz or 230V/50Hz.  The SecuTest SIII+ and SecuLife ST are the same basic instrument, with the SecuLife including standard features specific to medical testing, such as testing up to 10 application parts and test sequences per IEC 60601.  In order to evaluate electrical safety, tests are performed for protective conductor connections, insulation resistance, and leakage current.  Individual tests can be performed manually, or testing can be automated by using built-in test sequences that are in accordance with widely accepted international standards.

In the video below, Dieter Feulner, Product Manager for Gossen Metrawatt,  tests for touch current on a mobile X-ray device.

Dranetz Fall Power Quality Seminars

The first Dranetz Fall Power Quality Seminars have been confirmed and we hope you can attend.


These no-cost educational seminars are held at select cities in the continental US throughout the year. This incredible value is open to anyone interested in Dranetz instruments, and only requires registration to reserve your seat. All power quality seminars are 1/2 day and run from 8:00am to 12:00 noon, and a continental breakfast is included.
To register online CLICK HERE.

The current schedule (with more to follow) is:
October 9, 2013
Mayfield Village, OH

October 22, 2013
Albuquerque, NM

October 23, 2013
Lake Oswego, OR

October 23, 2013
Birmingham, AL

October 24, 2013
Greenwood Village, CO

October 30, 2013
Fort Lauderdale, FL

November 6, 2013
Fargo, ND

November 7, 2013
Bismarck, ND

November 13, 2013
Waltham, MA

General Agenda

• Introduction to Monitoring
• What Are We Measuring?
• Transducer Considerations
• Introduction to Power
• Energy and Demand, Power Factor 
• Real-Apparent-Reactive Power
• Typical Utility Billing Practices
• Case Study — determining energy costs
• Going Beyond Energy and Demand 
• to Improve Reliability
• Introduction to Power Quality
• Impact on Business Productivity
• Maintenance and Operating Costs
• Identify Typical Power Quality Events (overview of sags, transients, harmonics, etc.)
• Q & A: Your Application Questions

Ready to register?  CLICK HERE

Automatic Distribution Fault Location Case Study

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Consolidated Edison Company of New York is a long time user of Dranetz power quality monitoring systems and sister company Electrotek Concepts software and services. Dranetz Encore Series (61000) and Enhanced Power Quality, EPQ DataNodes) and legacy power quality instruments (8010 PQNode) are deployed throughout their network collecting needed data for PQ assessment. Electrotek’s PQView software, which is seamlessly integrated with the Encore System, provides database management, reporting and advanced statistical analysis. PQView’s Fault Analysis Modules identify and characterize faults, providing location information. Alarms are sent to operators who dispatch crews for repair, reducing the time to locate faults by hours.

The automatic distribution fault location system at the Consolidated Edison Company of New York was first put into use during the spring of 2005. It incorporates power quality monitors, microprocessor relays, database applications, up-to-date distribution circuit models, and geographic information system (GIS) databases in order to provide automatic distribution fault identification and fault location estimation. The system has become an indispensable tool for quickly and accurately identifying the location of faults in the Con Edison network distribution system.

The fault location system uses measurements recorded by Encore Series PQ monitors located in distribution substations. These measurements are downloaded automatically by Encore Series Software which manages the power quality monitoring system. Fault data is automatically acquired by PQView software and stored in its relational database. Calculations on these measurements estimate the reactance from the substation to the fault. The calculations are based on phasor measurements derived from the voltage and current samples and calibration constants based on previous fault data and known locations. The result of these calculations is an estimated “reactance to fault,” or XTF. The XTF values are compared with feeder models that estimate the positive-sequence impedance between substation and feeder structures. The estimated locations can be viewed in tabular format on the corporate intranet and can be displayed graphically using maps derived from a GIS database. The estimations for fault location typically are available on the company intranet approximately ten minutes after the fault’s occurrence. The estimates are accurate to within 10% of the total number of feeder structures, for about 80% of the single-phase faults measured in the system.

Each Dranetz power quality monitor records voltage and current at the output of a transformer in parallel with other transformers that together supply up to thirty underground network distribution feeders.

Example of a single phase fault on Con Edison network estimated to be j0.97 ohms downline from monitored substation

Example Summary Page for Faults Measured in a Network

Example Map Display of Estimated Fault Location

The Sign of the Sine

by Richard Bingham of Dranetz

There are certain phenomena that occur in nature which show up in so many different places that it is a bit eerie. The sine wave is one of those signs that the universe wasn't just randomly put together. If one plots the speed of the pendulum as it swings back and forth, the graph would be a sine wave. At the top of the arc, the speed is zero. Then it begins to travel faster and faster until the bottom of the arc. After reaching the bottom, it begins to slow down until it hits the other top of the arc and the speed goes to zero. The process reverses as it begins to accelerate in the opposite direction. The resulting graph is show below of the speed of the pendulum versus time.

The same curve represents the change in electrical current induced in a coil of wire as it rotates past two magnetic poles, which is the basis for an alternating current electrical generator. Not wanting to restart the debate between Edison and Westinghouse over whether AC or DC is the best way to transmit electrical energy, AC is how most electrical energy is transferred between electrical suppliers and the loads. Within loads, some devices change the voltage in to DC, such as those typically called electronic loads. Integrated circuits within personal computers, VCRs, or clock radios typically run off of either 5 or 12 Vdc (though newer circuits run on lower voltages (3.3 Vdc or smaller). But it is the AC voltage, or the sine wave, around which most of power quality phenomena is measured.

A sag or swell is determined by a variation in the amplitude of the sine wave. A sag is a reduction in the RMS value of the sine wave, typically below 90% of nominal, whereas a swell is an increase, typically above 110% of nominal. A seven cycle, two stage sag is shown below.

Harmonic distortion is a series of sine waves superimposed on each other. A transient, such as a PF cap switching generated event, can be decomposed into a series of sine waves. The oscillation following the initial negative going transient usually has a frequency between 400 and1500 Hz, compared to the fundamental power frequency of 50 or 60 Hz. As Fourier's Theorem states, any periodic waveshape can be represented by the sum of a series of sine waves. Even square wave and sawtooth waves are but a series of sine waves.

Power factor is based on sine waves. The method of measuring PF in the past was based on the difference in time or phase angle between the voltage and current. This is referred to as displacement PF. Electrical motors, which make up 60% of the load in the United States, have a current sine wave that lags behind the voltage sine wave, as a motor is mostly a coil of wire,which is an inductor. Unfortunately in today's harmonic rich electrical environments, this method no longer works. Today, true power factor is defined as watts divided by voltage amperes, or how much work is done versus the energy transferred.

Though the sine wave is really magical, most designers of equipment to be powered from the AC voltage waveform have made the assumption that the shape of the waveform will be basically sinuoidal, with the amplitude between certain limits (typically +/- 10%) and frequency stable. When events, such as large motor starts or downed wires, cause the sine wave to exceed these limits, it is usually a sign that a power quality event has occurred and possibly equipment malfunction has resulted.

Electrical Systems Reliability is Paramount

Power Quality has always been a key issue for healthcare facility managers. With the rapid advances in medical technology, hospitals, medical clinics and laboratories increasingly rely on sophisticated electronic devices for diagnosis, treatment and monitoring. This reliance demands a high degree of power quality and reliability to prevent disruption of mission-critical operations and procedures. Power quality disturbances can be caused by a range of internal and external phenomena and often re-occur because the location and nature of the event is not well understood or identified

While the costs of downtime or failures can result in thousands of dollars per hour, the costs of power and equipment failures in critical patient operations are immeasurable.

The Dranetz PowerGuide 4400

Dranetz Power Quality analyzers are ideal for proactively monitoring the power systems of healthcare facilities.

Never before has power quality and reliability been such a key issue for facility managers. Not only can the cost of downtime run into thousands, or even millions of dollars per hour, but power quality events can impact sensitive equipment such as servers, motors, process equipment and computers. This end-use equipment is often interconnected within networks, industrial processes and power infrastructure and can be negatively affected by events that arise both from the supplying power system and are generated within the facility. Power monitoring is key to maximizing uptime and ensuring all power infrastructure is functioning properly.