Solving poor Power Quality (PQ) A win-win opportunity for installers and their clients In our increasingly digital economy, maintaining Power Quality (PQ) is a growing problem. For many business users, the cost of poor PQ is even higher than their electricity bill. Although solutions are being installed, the problem is still largely underestimated, mainly because the losses are often hidden. Revealing those losses and proposing a cost-effective mix of solutions is an opportunity for the skilled contractor to create a win-win situation with costconscious, quality-minded clients. The growth in the use of power electronic equipment influences PQ in two ways. Power electronics, built-in computer power supplies, energy saving lamps, and motor driven systems with variable speed control are generating first, harmonic disturbances. Due to the prevalence of these systems, nearly all-electric grids nowadays suffer from harmonic currents. They result in additional heat losses and premature equipment failure. Second, the very loads that disturb the system are themselves increasingly sensitive to PQ disturbances. And when electronic equipment suffers from voltage dips and outages, it can result in lost production, damaged equipment, idle personnel, and lost data. Singly or combined, these effects can lead to postponed revenue, a negative impact on cash flow, loss of goodwill from customers, and even loss of market share. Very few industrial or office sites are trouble free, and most suffer from several PQ issues at once. A gap of two nines Concerning outages, a useful rule of thumb is that digital society needs an availability of ‘6 nines’ (99.9999%). However European distribution networks typically supply an availability of only three to four nines (99.9 to 99.99%). To compound the problem, given the current energy market, it is unlikely that the quality of supply will increase significantly in the coming years. Utilities supply to a base level of quality according to the European standard (EN 50160), and it is up to the users to implement mitigation measures should this base level be insufficient. This is where contractors can play an important role. They can alert clients to the problem, explain why improving PQ is a sensible investment, and provide cost-effective solutions. A best practice working method PQ problems typically have no single generic solution, which presents another interesting challenge for the contractor. The optimal solution needs to be tailored to the characteristics of the site. This includes the quality of the local voltage supply, the type of loads installed, and the sensitivity of the equipment to disturbances. The following best practice PQ audit shows how to determine the optimal tailor-made solution. ¾ The first step is data collection. Advanced monitoring solutions are available to measure the quality of the local voltage supply. They register the types of event, the location, and the frequency with which they occur. ¾ The next step involves an assessment of the equipment installed to determine its sensitivity to each type of PQ event, and the financial consequences of malfunction or failure. By combining all of this information, the cost of each type of PQ event can be estimated as well as the total annual cost of poor PQ at the site. ¾ The reduced cost of poor PQ due to reduced sensitivity (improved immunity) can be calculated for each available mitigation measure. Adding this to the annualized cost of the investment yields the type of graph shown in Figure 1. $500.000 Solution cost Damage due to sags $400.000 $300.000 $200.000 $100.000 $0 base case - no changes Primary static switch Service entrance Protect machine Combined static energy storage (2 controls and switch with MVA) winders controls protection This allows for an accurate economic comparison between the various types of mitigation solutions. ¾ Along with these hard figures, various soft benefits of good PQ can be taken into account as well. Chief among these are the increased continuity of operation, risk-reduction, and better staff safety and well being. Detailed understanding makes the difference The best practice given above may seem a complex process. In actual fact, it is even more complex since it should cover more than a dozen problem areas for which an even larger number of solutions exist. Most companies have some notion of PQ and many have already installed some kind of solution. However contractors can make a big difference if they have a detailed and complete understanding of the subject. They are then in the best position to point out the unexpected costs of poor PQ by determining all the causes and consequences. They are also perfectly positioned to propose the optimal mix of solutions, tailored to the local conditions, that yields the largest total cost saving for the site. What is poor Power Quality? PQ can be defined as the extent to which electrical power: • Is continuously available • Is within voltage tolerances • Is within frequency tolerances • Varies according to a pure noise-free sinusoidal wave shape The five most common PQ defects are: Under or over voltage Transients 350 300 250 200 150 100 50 0 -50 -100 -150 -200 -250 -300 -350 Dips or surges 5 10 15 20 Harmonics Blackouts • Blackouts • Over or under voltage • Dips and surges • Harmonic distortion • Transients PQ defects can originate from equipment on site, or from the supply network. Typical origins of a defect are: • Sudden connection or disconnection of a load • A power station suddenly going down • An overcharged line • A lightning strike • Harmonic distortions introduced by a generation unit or by a consumer load Which problems occur? Figure 3 shows the result of a survey conducted by the European Copper Institute in 2001. Facility and building managers at 1,400 sites in eight European countries were asked about the PQ problems they had experienced. % occurence Computer lockups Flicker Equipment damage (at partial load) Data processing equipment PFC overloading Problems when switching heavy loads Overheated neutral Problems with long lines Nuisance tripping Utility metering claims 0% 5% 10% 15% 20% 25% 30% The Power Quality solutions mix Solutions can be applied at four levels (see Figure 4). % adoption Surge protection UPS T-rms metering Equipment derating Dedicated circuits Total rewire Meshed earth Passive filters Active conditioner TN-S rewiring upsized neutral 0% 10% 20% 30% 40% 50% 60% 70% 1) Install less sensitive equipment • Only a cost-effective solution in specific cases and not as a general policy 2) Protection between the equipment and the panel • Installing different protection measures for different equipment means more flexibility • More expensive if the same protection measures have to be installed several times 3) A site-wide protection and mitigation • Less expensive if it allows the grouping of certain protection measures • More expensive if different measures for different equipment need to be installed 4) Solutions in the supply grid • Requires an agreement with the utility company. • Contracts with utilities for delivering ‘premium PQ’ have had a limited success to date Figure 5 shows the most popular on-site solutions, based on the above mentioned survey. 1 controls 2 1. 2. 3. 4. motors 3 … Equipment specification Controls protection Overall protection inside plant Utility solutions 4 utility source Sensitive process machines Development of the European Association of Electrical Contractors - AIE - in the 21st century Formed by a few visionary countries to provide an opportunity to reflect together on common problems in 1954, the European Association of Electrical Contractors – AIE – comprises today 21 national associations representing 175,000 contractors, a workforce of 900,000 and a turnover of Euro 60 billion. But the scope of AIE is wider than Europe. NECA USA, ECA South Africa, NECA Australia and FAPECA (Federation of Asian and Pacific Electrical Contractors Associations) are all corresponding members of AIE, and with whom AIE maintains an excellent and strong relationship. Moreover these European and International Electrical Associations have formed the International Forum of Electrical Contractors (IFEC).