In 2001, the European Copper Institute conducted a Power Quality (PQ) survey covering 1,400 sites in 8 countries of Europe. It found that harmonic distortions, power supply reliability, voltage dips and electromagnetic compatibility are the most important issues for the countries of the European Union (EU). Another PQ study was conducted by the Leonardo Power Quality Initiative (LPQI) among various customers in the EU-25 countries in 2004. It was concluded, that on average, the absolute share of impacts of power quality and reliability related problems, are due to voltage dips (23.6%), short interruptions (18.8%), long interruptions (12.5%), harmonics (5.4%), transients and surges (29%) and other PQ related problems (10.7%). In the United Kingdom, the main complaint of customers is due to the supply standard related to the restoration time after fault interruptions. Some complaints are also about the supply quality issues such as voltage dips, harmonics and flicker. In South Africa, voltage dips and transients have been identified as a major PQ problem because a large part of the electricity infrastructure consists of overhead lines.

From various surveys, it was generally noticed that industries are vulnerable to long and short interruptions (that are considered as ‘reliability issues’ in the power system analysis). Voltage dip is the main PQ problem for semiconductor and continuous manufacturing industries, as well as to the hotels and telecom sectors. Harmonic problems are perceived mainly by commercial organizations and service sectors such as banks, retail, telecom etc. Another PQ problem that draws high attention is the presence of transients and surges at the customer’s installation.

Today’s process control equipment, mission critical systems, and devices are sensitive to PQ disturbances in the line power network. From international customer surveys, it is found that complaints on PQ related disturbances (for example: harmonics, voltage dips, flicker, etc.) are increasing every year. In Europe, the quality of electricity that is provided by a grid operator must comply with reference parameters set in the European standard EN 50160 and other specific standards or national grid codes. In contrast, it was observed that the customer’s loads often interact adversely with the network components and distort the network’s voltage. When the line voltage is distorted, the powered equipment and devices draw non- sinusoidal current from the network.

Non-sinusoidal current can cause many technical problems (extra heating, mis-operation, early aging of the devices, etc.) for the equipment being powered. Non-sinusoidal current also causes extra losses and other problems to various power network components (as example: cables and transformers). Moreover, poor PQ often has large financial consequences to the affected installations, such as increased fees from the utility provider. Factors reducing PQ include transient voltage increases, sudden power surges resulting from lightning strikes, frequency changes and fluctuations in waveforms (harmonics). The increasing size and complexities of electrical networks are a major factor leading to decreased PQ. Decreased PQ has led to nearly €150 billion in losses yearly in the EU-25 countries, and nearly $120 billion in the United States.

One of the most common methods for utility users to correct the perceived PQ problems is with the use of a power conditioner or an uninterruptable power supply (UPS).

Industrial environments can be characterized with high current loads, variable frequency drives, high ambient temperatures, and relatively high levels of mechanical vibration and airborne particulates. To meet the requirements of these more demanding applications, it is essential that a high-quality, rugged product, which is designed to the customer requirements and made specifically for industrial operating environments, be deployed.

There are several different technologies available that address PQ problems: Standby or Offline, Line- Interactive and True Online Double Conversion.

A Standby or Offline UPS typically offers only surge protection and battery backup capability. The standby UPS is the most common type used for desktop computers. It uses a transfer switch to select either AC from the mains or the battery/inverter as a backup source in the event of a power loss. Switching from line power to inverter/battery power is typically 8-10 millisecond (msec), so the term “uninterruptible” is not accurate, and this interruption may cause load equipment to shut down.

These types of systems are typically inexpensive. The inexpensive inverter design in Standby (Offline) and Line Interactive UPSs often produces a square wave (Figure 1), and not a true sine wave output. The lack of a pure sine wave output waveform may cause sensitive load equipment to constantly cycle on and off, not operate properly, and feed current distortion back on to the electrical distribution network.

Essentially standby systems offer no protection from PQ problems. They are typically deployed to provide emergency power in the event of a complete power loss. A typical application for this type of device would be emergency lighting.

A Line Interactive UPS is similar to a Standby UPS. A Line Interactive also passes input power through an autotransformer to the output with some power conditioning, and the inverter only provides power during an input power loss or brownouts, with a wider range of sags, swells and events on the input line voltage before switching to inverter/battery backup power.

These systems provide protection from the least common, but most critical PQ problems. Typical applications for this type of device are home and small office computing networks where power reliability is an issue.

An Online UPS is superior to Standby and Line Interactive UPS designs because an Online UPS works 100% of the time. Input AC electricity is continuously rectified to a DC voltage and inverted back to AC (Double Conversion) where a true sine wave AC output waveform is provided (Figure 2). The AC-DC rectification stage eliminates electrical disturbances on the input power line, and the pure sine wave output waveform generated by the inverter provides the clean, reliable output power. A True Online, Double Conversion UPS is truly uninterruptible because the inverter is online, all the time, with no interruption (0 msec) in the output power waveform when the AC input source is lost. The inverter seamlessly transitions from AC input utility power to battery backup power without any interruptions or disturbances in the true sine wave output waveform. This design effectively eliminates all PQ defects including the feedback of load anomalies to the main distribution system.

Before deciding on a specific UPS, an analysis of utility power is recommended. If the study indicates numerous PQ problems, it is a strong case that power protection is needed. Environment is also a factor, especially if the area is prone to frequent electrical storms.

Using microprocessor-based equipment, in industrial environments, is like putting a computer room right on the plant floor. Operating adjacent equipment with diverse electrical loads may cause power-line fluctuations that can cause havoc on the microprocessor-based equipment. This “power pollution” can be caused by turning on and off large industrial motors, using electric welders, switching large circuit

breakers and operating other equipment that uses large amounts of power. Steel mills, for instance, have additional concerns with electric furnaces and other devices contributing to power-line problems.
Electric utilities themselves can add to these troubles when they perform power-factor corrections in large industrial complexes. This procedure can cause a phase shift, which can result in computer-system failure. UPSs can be assets when using standby generators, or when switching between two utility feeds, especially in situations where power breaks are undesirable. Some facilities may install backup generators without a UPS, but soon find they needed to add a UPS to maintain critical loads.
UPSs can be used with a standby generator to cover power breaks during transfer time. Typically, a computer can tolerate only a 10-12 msec power outage at nominal voltage. Generators are susceptible to load changes, causing current and frequency fluctuations. Another problem can exist when facility power is brought in from two different utility feeds. A large electromechanical switch with contactors is used to transfer from one feed to another upon a failure which creates a short break in power that cannot be tolerated by today’s microprocessors. Process controls, power supplies and other electric apparatus’ used in many industrial complexes often produce their own related power anomalies. All of these situations can be corrected by installing a UPS downstream. With the UPS in place, there will be no power interruption to critical loads during transfers. Using a UPS will also help protect computers and power supplies from premature component failure due to power surges and abnormal line harmonics (those greater than 5% total harmonic distortion).

The inexpensive commercial UPS’s manufactured by large power supply manufacturers for residential and commercial applications may not be appropriate and may not be the cost-wise choice for many industrial applications due to the inadequacy of the technology, the mechanical and electrical design may be incapable of passing strict industrial standards, and the hidden life cycle costs may be considerably higher than a UPS specifically designed for applications in harsh industrial environments. Standby, or Offline, and Line-Interactive UPSs compromise power protection for cost. A true online, double-conversion UPS is the best protection for sensitive electronic equipment. It best protects both your load from electrical disturbances and your closed electrical system from harmful load harmonics.

When choosing an UPS, power conditioner, battery backup or power distribution system for your applications, it’s critical that reliability and survivability in all operating environments be considered in the context of the true life cycle costs of the purchasing decision. The UPS with the lowest initial investment may cost much more over the life of the system when replacement, sparing, logistics and downtime costs are considered.

NOVA Power Solutions is focused on solving problems encountered during the generation, distribution and use of electrical energy. Recent studies indicate that greater than 80% of electronic systems failures are power supply related. Furthermore, greater than 95% of power supply failures are directly or indirectly related to the PQ of the primary electrical system.

NOVA Power Solutions power conditioning solutions eliminate 98% of distributed electrical system anomalies, increasing system reliability and electrical generation efficiency.

NOVA Power Solutions power conversion solutions optimize load side electrical efficiency further and thus enhance reliability and allow for the use of a wide spectrum of electronic solutions to meet your requirements.

NOVA Power has established itself as a premier provider of mission-critical rugged UPS, Power Conditioners, and Battery Backup Modules, with over 40,000 units presently deployed in the world’s harshest environments. Our solutions protect critical systems worldwide for applications where “up time” and reliability is absolute and unconditional.