Harmonic Analysis & Problem Solving


Almost three decades after power electronic-based (non-linear) electronic loads entered the marketplace, utilities still encounter problems with harmonic voltage and current problems on their grids. The growth in the use of power electronic loads continues to set industry records. Several commonplace loads such as lighting and motor loads are yet to be converted to high-efficiency electronic loads. Upgrades to traditional analog systems in commercial facilities and industrial plants are increasing as well. Moreover, load growth in all customer sectors continues to increase. All of these changes continue to increase the demand for harmonic currents and reactive power on the grid.

Increases in harmonic current flow on the grid originates from customer facilities. Most facilities rely on original facility power systems which were not designed to support harmonic current flow. When harmonic currents increase, power system sources and their wiring systems cannot sustain the quality of voltage. This results in voltages with distortion beyond accepted industry limits being delivered to customer facilities. If voltage distortion becomes to high and has the right mix of harmonic components, the operation and reliability of electronic equipment is impacted.

Electrotek expert engineers maintain expertise in harmonics. Electrotek’s capabilities in this area include harmonic studies – characterization (monitoring), modeling, simulation and analysis of harmonic current sources, harmonic current flow, reactive power management (internal and external power factor capacitor banks), design of harmonic filters (passive and active).

Architecture & Engineering Firms

Electrical engineers who design commercial facilities and industrial plants are accustomed engineering the supply and distribution to the loads for their customers while following the National Electrical Code (NEC) and other building design- and construction-related codes and standards. Some design engineers are now fluent in harmonics analysis and in applying basic types of harmonic mitigation. However, customers are requesting more harmonic-rich electronic loads be designed into their facilities. Harmonic-related PQ problems are also extending out beyond the 50th harmonic. Dranetz is the first PQ monitoring manufacturer to offer instrumentation that will measure harmonics out to the 254th component.

With the increase in harmonic current flow and the need to include harmonic filtering in customer facilities and industrial plants beyond basic passive harmonic filter technologies, customers are demanding improved harmonic control and reactive power management. A&E firms who engage with Electrotek Concepts to help them provide their customers with facility and plant designs with more effective and reliable management of harmonics will provide their customers with facilities and plants that have fewer PQ problems.

Many customers demand an IEEE 519-based harmonics analysis to ensure they are not violating the IEEE 519 voltage and current harmonic limits specified in the 2014 standard. This is especially true when customers require the installation of large harmonic-rich electronic loads. While many A&E firms can conduct IEEE 519 analyses, the use of Dranetz HDPQ PQ monitors and IEEE 519 analysis functions embedded in Electrotek’s PQView data management and analysis software will reduce the analysis time by at least 35%, allowing A&E firms to increase their profits and pass some of this savings along to their customers.

Electrotek expert engineers maintain expertise in harmonics. Electrotek’s capabilities in this area include harmonic studies – characterization (monitoring), modeling, simulation and analysis of harmonic current sources, harmonic current flow, reactive power management (internal and external power factor capacitor banks), design of harmonic filters (passive and active).

Equipment Manufacturers

Equipment manufacturers who operate industrial facilities must take every measure to manage the PQ of their electrical environment. One area of PQ management is around harmonics control. Manufacturers are increasing their use of harmonic-rich loads as they aim for improved manufacturing processes with enhanced control and for reducing manufacturing costs. For example, a manufacturer who produces concrete mixing materials traditionally operating a large rotating kiln using a line connected electric motor installs a modern multi-pulse variable frequency drive (VFD). This allows them to achieve better control of the kiln and reduce energy consumption at the same time. Before the manufacturer can reliably support the new VFD, they must be sure their plant electrical system can support the increased harmonic current flow and reactive power increase.

On another front, the manufacturer of the VFD for the concrete customer may be launching a new VFD design with no practical field experience in the use of this VFD and the harmonic performance expected when the VFD is connected to a real plant electrical system. If the VFD manufacturer can show the concrete manufacturer how this VFD design performs in a real plant regarding harmonics, the concrete manufacturer will be more likely to understand how installing one of the large VFDs might impact the harmonic PQ of their plant.

Electrotek expert engineers focusing on harmonics analysis and control can answer both questions. These questions can be answered by conducting a modeling and simulation of the plant’s electrical system through conducting a harmonic study on that system. Electrotek can also help the VFD manufacturer understand how their new VFD will impact other industrial plant electrical systems by using such systems that Electrotek has on file. Such an analysis on the concrete manufacturer’s electrical system can also reveal the need for specific types of harmonic filtering at the most appropriate locations on the plant’s electrical system.

End Users

Harmonic current requirements and distortion in AC current waveforms start at the loads used in end user customer facilities. Traditional (dumb) loads—incandescent lamps, resistive heaters and electric motors were the loads that built the original utility power system. Motors are inductive loads that draw phase-shifted currents. These currents create a displacement power factor (DPF).

The advent of semi-conductor devices—transistors and diodes to start gave rise to the development of electronic loads. Traditional electronic power supplies utilized “switching” to rectify AC voltage and current. These switched waveforms allowed loads to draw non-linear harmonic currents and gave rise to a two-dimensional power factor—true power factor (TPF).

Today’s electronic power supplies utilize complex switching schemes to produce a DC voltage bus. Prior to active power factor corrected (APFC) supplies, harmonic currents drawn by electronic loads were easily 100% or more of the 60-hertz rectified and switched current. This meant that facility power systems would have to provide more harmonic current than 60-hertz current doing real work.

Although today’s power supplies used in all types of electronic equipment are APFC designs, they still draw enough harmonic current that, when banked in a facility, can cause serious harmonic current flow and the need for reactive power management and upstream PFC.

Larger loads like variable frequency drives (VFDs), which have some APFC and passive PFC, will draw an appreciable amount of harmonic current. When a facility utilizes dozens to 100s of VFDs, the need for harmonic current control and PFC is paramount.

End users who operate facilities where the number of electronic loads per square foot are high must engage in carefully designed harmonic control and PFC. Electrotek’s expert engineers have extensive experience in conducting harmonic evaluations of commercial facilities and industrial plants. Our engineers can also design state-of-the-art harmonic filtering devices—passive and active and model and simulate the customer’s electrical system and include the appropriate harmonic mitigation in the model to simulate actual results. Field performance is verified with remote PQ monitoring using Dranetz monitors.