EPQU Magazine - Vol 3 Issue 1

Welcome to the first issue of Volume 3 of EPQU Magazine. I hope you will appreciate the new features and format of our renewed e-journal.

So what's new?

First of all, EPQU Magazine becomes a fully and exclusively electronic magazine. The magazine fully exploits the benefits of electronic publication, such as reader comments and video interviews.

Secondly, electronic publication allows more flexibility. EPQU Magazine invites your papers and articles anytime, and will review, process and publish contributions as they are received.

Finally, EPQU Magazine becomes a fully featured magazine, adding reader contributions, video interviews, reader questions and events to its regular content.

Highlights of the current issue include a series of case studies on power quality and energy efficiency in various industry sectors and a series of papers covering sector-specific power quality problems experienced in hospitals, large buildings or internet data centers. This issue also includes a number of vision statements on the future of power quality, i.e. its research needs, economics and regulatory framework.

The issue contains 20 featured papers and reader contributions, 3 video interviews and 4 reader questions.

We hope the new magazine meets your expectations.

According to the European Union, 40% of all electrical energy produced in Europe is used to power commercial and residential buildings. Commercial buildings include non-residential, non-industrial buildings such as hospitals, office and apartment buildings, hotels, schools, churches, stores, theaters, and sports arenas. Within those buildings, HVAC units, PCs, fax machines, copiers, and printers are now sharing the building wiring system with electronic fluorescent lighting, adjustable speed heat pumps, and various electronic communications equipment. While electronic based commercial equipment increases productivity, this type of equipment can often be adversely affected by poor power quality.

Today, the quality of electrical power generation, transmission, and distribution systems is very high. With the exception of conditions associated with brownouts, most utilities deliver well-regulated power to all but the most extremely remote customers. However, power dips and surges are still of concern, largely because of the potential impact for electronics damage and interference with computer operations. Another power quality issue that must be kept in mind is the production of harmonic currents by nonlinear equipment, such as office equipment, lighting, and some HVAC systems.

This PQ TechWatch takes an in-depth look at some of the larger components of commercial operations, including HVAC, lighting, office equipment, and elevators. The intent of this document is to show how power quality impacts commercial equipment, and what mitigation techniques can be applied to minimize shutdowns and equipment damage.

By Dragomir Vasic

In this reader article, Dragomir Vasic introduces a basic technique of frequency regulation for preparing the fuel-air mixture in hot water boilers used for district heating. This simple and relatively low-cost measure saves 25,000 euro per year, with a payback of just 0.6 years.

With such compelling economics, one would expect most old boilers to be retrofit in this way, but according to Dragomir, this is often not the case. It's often easier to charge customers for high losses rather than to engineer change.

An energy service company would be a solution, bringing in specialised expertise to facilitate the project. But it's often a barrier to companies to open up their operations, and expose their inefficiencies to a 3rd party.

By B Franken et al

This paper provides an appraisal of what regulators need to consider in establishing an effective voltage quality regulatory framework for distribution networks. In particular, the paper considers the regulation of five voltage quality dimensions: short interruptions, voltage dips, flicker, supply voltage variation, and harmonic distortions. The paper assesses the most appropriate regulatory control method and presents practical experiences through a number of case studies.

Jonathan Manson presents the results of a survey conducted by the European Copper Institute (ECI) into the consequences for EU industry of poor power quality. These add up to >€150bn annually, are mainly experienced by industry and caused by power interruptions (dips, surges, transients and short interruptions). A call for action is made using the significant and disturbing conclusions drawn from the analysis of the survey.

By Angelo Baggini, University of Bergamo
& Franco Bua, Engineering Consulting & Design

In industrial plants, power transformers are expensive components of high strategic importance. Unavailability due to faults generally results in high costs, both in relation to repair work and in terms of lost production.

Efficient diagnostic monitoring capable of highlighting incipient faults and therefore able to reduce the fault rate and downtime of the transformer within considered physiological limits are generally of extreme interest for maintenance departments.

This article introduces a number of general considerations on fault statistics, and explains the main on-line diagnostic monitoring approaches.

By G Esposito et al

The increasing concerns related to the global warming process determined the shifting towards the use of distributed generation (DG) designed to meet the environmental restrictions. The increasing penetration rate for the DG in the energy systems is raising technical and non technical problems that must be quickly solved in order to deeply exploit the opportunities and benefits offered by the DG technologies. In this paper, the analysis of the impact of distributed generation units on the voltage quality in a 6 kV medium voltage network is conducted. The distributed generation units may require an inverter before their interconnection to the mains. Thus, these converters can produce harmonics that propagate in the distribution network. The case studies are conducted using the software package ATPEMTP on an existing 6 kV network.

By A Baggini at al

The installation of non linear loads determines the presence of current and voltage harmonics and interharmonics. Components particularly sensitive to this kind of phenomena are power factor correction equipments. This paper describes the design process of a centralized PFC system under harmonic pollution conditions pointing out the key role of measurement campaigns.

Summary

This paper deals with PFC units' design related problems in case of installation in harmonics rich environments: in particular, the paper contains an overview of sizing approach used in a real case of PFC unit design for installation in a steel factory where new PFC units installation has been necessary after a fault with catastrophic consequences for the existing ones.

The document contains a report on stress calculation on PFC units due to harmonic currents generated by non linear loads installed in the above mentioned plant. Plant load, estimated to be around 80 MVA, is formed by a large number of small loads fed by power converters. This is a big disturbance source for the installation in terms of harmonic content.

In particular, due to the usual lack of real harmonics contents data availability, the main issue has been the process of definition of a generic harmonic distortion for installed loads, based on power converters installed and literature available data on power converters spectra and its on field verification for PFC optimal design, with three measurement campaigns aiming to verify real harmonic distortion and series and parallel resonance risk.

This kind of problem is very real, and, most of all, is constantly growing in other industries as well, not only in steel factories where harmonics content has always been a key problem.

Now, due to the continuous increase of power converter usage and equipment power consumption, and most of all to the increase of equipment disturbances sensitiveness, to avoid potentially tragic faults, a deep measurement campaign is the key solution at PFC units' design stage, also considering the usual lack of data on installation harmonic distortion.

The experience described in this paper constitutes the first detailed example of in-the-field verification of harmonic disturbance effects on two 8.4 Mvar, 13 kV PFC units in a harmonics critical environment aiming first of all at a detailed fault analysis (referred to pre-existent PFC Units) and then to a correct new unit design.

In the paper, the different design stages and related issues are described, including: installation network analysis, load analysis, harmonic distortion evaluation, PFC units stresses analysis, PFC units sizing, on field stresses verification.

This work highlights the strong need for deep measurement campaigns in harmonics rich industrial environment as the only way, in addition to a correct distortion pre-analysis aiming to a careful PFC design strategy to prevent potentially catastrophic faults.

A new case study by Michèle De Witte, Laborelec.

A steel manufacturing plant was experiencing a flicker problem. Lights in the office areas of the plant were often flickering, affecting productivity and creating an irritating nuisance for employees.

A Power Quality consultant was called in to investigate the case. He carried out measurements to gain a better understanding of the problem and to enable him to identify the source of the flicker phenomenon and the operating conditions in which it occurred. Once this information in hand, he was able to propose an appropriate solution.

A new case study by :

Nowadays, energy is one of the most important prime materials in industrial processes. Highly automated industries need to have a reliable power supply and efficient energy utilisation in order to maintain both a high productivity and to be competitive. On the other hand, in industry automation, designing the automation process has an important influence on the later energy consumption. In the following case study an automated pneumatic waste collection process was studied for its energy efficiency assessment and its improvement.

by Philip Keebler, EPRI

The healthcare environment is made up of perhaps the most unusual combination of electronic loads found in any facility. Healthcare facilities not only rely upon commercial loads (such as computers, servers, and lighting system) and industrial loads (such as food preparation equipment, laundry equipment, medical gas systems, but also rely on electronic medical loads (that is, medical equipment to operate the facility and provide patient care services.

As in other facilities, when an electrical disturbance such as a voltage sag, voltage transient, or voltage swell reaches the service entrance of the healthcare facility or medical location, computers in the accounting department may shut down, and motor starters and contactors providing power to the air-conditioning and ventilation system may change the environment within the facility. Unlike other places, however, a patient’s life could be threatened when an aortic balloon pump trips off-line during a cardiovascular surgery. The costs associated with downtime can be staggering, but no bounded cost can be placed on the irreversible result of loosing a patient.

Building, electrical, and healthcare codes in the United States require that hospitals and other medical clinics have emergency power ready to activate upon the detection of a power quality problem and assume the load within 10 seconds of the detection. However, even though a generator may be used at a healthcare facility or medical location, it cannot be on-line to support critical medical equipment with an activated transfer switch in less than about 2 to 3 seconds at best. This duration of time might as well be forever in terms of the ability of electronic medical equipment to continue operating. In fact, an undervoltage as short as ¼ of a cycle (about 4 milliseconds) is often sufficient to confuse sensitive electronic devices.

This PQ TechWatch will introduce the typical problems found in healthcare facilities, enlighten the reader on some new issues, and provide practical guidelines for avoiding those problems.

By Didier Empain, Laborelec

In this new case study, a large plant in the transport sector was experiencing a general voltage interruption caused by a local short-circuit inside the plant’s electricity network. This happened because of a non-selective tripping of the general protections at the plant’s connection point. The company decided to take action to identify the origin of the malfunction and implement corrective measures. An electricity consultant was called in to investigate the case.

By Conrad Bottu, Laborelec

Download case study (pdf)

Description of the site

The Belgian site being studied in this paper is connected to the public transmission grid (380 kV) by a High Voltage (HV) station. This HV station incorporates a 25 kV substation linked to a second substation via 25 kV underground cables. The second substation supplies the electric installations on the site.

The substations contain 25 kV circuit breakers in interior type HV cells with a metallic casing (see pictures below). The insulation is realised by SF6 gas. The safety relays and control devices are located in cabinets situated on the front panel of the cells. Their LV supply (110 VDC and 24 VDC) is provided by cabinets situated in an adjacent room.

Description of the problem

When operating the new circuit breakers, the control circuits received over-voltages and broke down. The same thing happened during other operations and events, including in-line short circuits, section switch closures, and above all the connection of the 25 kV cables to the earth to discharge them.

Thousands of Euros were going up in smoke every time one of these events occurred. The poor EMC of the installation was generating voltage surges between the LV equipment and the earth, causing the breakdowns.

Solution

The company called in an EMC consultant to study the phenomenon and propose a solution.

Since the earthing concepts of the HV station with the incorporated substation and the second substation are different, part of the consultant’s study had to be executed separately. The first substation contained an earth loop connected to the mesh of the 380 kV public grid earthing system, while the second substation earthing system consisted of earth rods.

The EMC consultant provided the company with a solution to bring the surges below the 500 V limit tolerated by the LV equipment. He recommended, among other things, building a meshed ground grid and improving the continuity of the cable shielding. In the solution, all connections to the earth were kept as short as possible and the installation of data cables and power cables next to each other was avoided.

After implementing the proposed measures, a thorough inspection and test of the substation was carried out. The measures reached their objective and no more breakdowns have occurred.

By Mark Stephens, EPRI

The building of Internet data centers (IDCs) is a growing industry that is pushing the limits of electric power and reliability requirements. As utilities must decide whether it is worth the cost to build new infrastructure to keep up with the present demand, facility operators are looking at power distribution designs that will improve efficiency and allow them to continue to expand their operations.

To meet customer expectations of “five nines” — or 99.999% — availability, IDC designers must improve power quality, reliability, and efficiency. In this quest, redundancy in the system becomes absolutely necessary, but also important are power quality issues such as mitigation of voltage fluctuations and harmonics and good techniques for grounding.

This PQ TechWatch provides information about the types of data centers being built and their design, along with new standards and certification processes that are being developed. Detailed descriptions are provided of power quality considerations and possible solutions. Grounding is given its own section, where electrical standards for safe and effective grounding are discussed and examples provided.

A power quality case study

By Michiel Van Lumig, Laborelec

Various departments at a car manufacturing plant are suffering from regular process outages due to voltage dips. These dips are causing production losses in the Metal Operation, Spray Coating, and Assembly departments that directly affect the productivity of the plant. The cost of those losses is directly related to the profile of the voltage dip (duration and depth).

Various options to reduce these costs are investigated, with particular emphasis upon the Spray Coating and Assembly departments. The following conclusions can be drawn:

1. The number and type of dips occurring at the point of connection of the plant is regular. It is similar to what is monitored at other medium voltage stations that have the same grid structure.

2. A detailed analysis of the spray coating process reveals that installing a ‘restart on the fly’ system on the large conditioning fans substantially reduces the related voltage dip losses.

3. A detailed analysis of the Assembly department shows that there are two main bottlenecks that determine the restart time after a dip (the ‘Drive’ sub-process and the ‘Cockpit’, ‘Marking’, and ‘Transport chain’ users). These bottlenecks can be removed by installing a Dynamic Voltage Restorer (DVR), which results in a payback time of 1.4 years.

Download paper (pdf)

Once upon a time there was a buyer at a large company who had to purchase a large three-phase induction motor with a power rating of 1 MW that was to be used in a big machine. As usual, he invited suppliers to submit bids. Before drafting the tender documents he spoke to the head engineer and technicians at the relevant technical department about the expected number of operating hours per year, the machine’s level of utilization and its load profile. Talks then began with potential suppliers about what sort of efficiencies could be achieved. As is normal, the buyer and supplier agreed on a penalty clause that would allow a price reduction to be imposed should the motor fall short of the efficiency level agreed in the sales contract. Equally, in the event of the motor exceeding specifications, the supplier would receive a bonus.

Once upon another time there was another buyer at another large company – or perhaps it was even the same buyer at the same company. This buyer needed to buy 1000 small three-phase induction motors each with a 1 kW rating that were to be built into the numerous small machines at his large company. He put out requests for quotes, specifying the voltage, design and con¬figuration and the number of poles, and then placed his order with the cheapest supplier. The word ‘efficiency’ was nowhere to be seen: neither in the request for quotes, nor on the motor’s rating plates. Perhaps it was mentioned in the manufacturer’s catalogue, but, as so often, it remained unread.

The sad thing about these two fairy tales is that they aren’t actually fictional at all, but a fair description of current industrial practice. Had we swapped the two stories, then we would at least have avoided the most absurd aspect of the situation: the fact that large motors are inherently far more efficient than small ones.

Download paper (pdf)

By Roeland De Meulenaere & Bohdan Soroka

Insulation and Heating -

Ventilation and Air-Conditioning -

Leonardo ENERGY launches its video channel where you can watch interviews with sustainable energy experts around the world. In this interview, Bill Howe shares the vision of EPRI on PQ research for the next 10-20 years, and also presents a renewed and vigorous vision for the role that PQ can and should play in enhancing the economic performance of modern electric power suppliers, manufacturers, and other key industry partners.

If you want to know more after viewing the video, download this paper, which was produced at the EPQU Conference.

... to increase the electric power availability, reduce running costs and prevent damage to people & property

Leonardo Energy launches its case study series with this first one about maintenance as a tool to increase the electric power availability, reduce running costs and prevent damage to people & property by Matteo Granziero, Socomec.

A lack of preventive maintenance on electrical systems can cause poor quality and wasted power or even danger for people and property. Scheduling annual inspections by experienced personnel is the solution to maintain high levels of electric power and safety for the enterprise.