**What is Harmonic Study and Analysis?**

Definition of harmonic wave distortion study and analysis is activity performed to determine harmonic disturbance levels and filtering requirements within a facility and to determine if harmonic voltages and currents are at acceptable level —Omazaki Engineering is a consultant who serves harmonic studies and analysis consulting services. If you are looking for harmonic disturbance study and analysis consultants company for your project or electricity system facilities in Indonesia and South East Asia contact us by sending an email to cs@omazaki.co.id or filling in the form in contact. We conduct the harmonic studies and analysis mostly using ETAP software.

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**Basic Knowledge**

**What is Harmonic?**

In electricity, a harmonic is a priodic non-sinusoidal waveform which can be represented as the summation of a sine wave having an integer multiple of the fundamental frequency. If there is a superposition between the fundamental frequency wave and the harmonic frequency wave, a distorted wave is formed so that the waveform is no longer sinusoidal.

**What Generates Harmonics?**

The main source that generates harmonic waves is non-linear loads. Non-linear loads are designed to save the use of electrical energy and be more efficient because they use semi-conductor components that can be adjusted using time. However, on the other hand, the use of semi-conductor components also causes interference in the form of distortion of current and voltage signals that flow back into the electrical power system. This disturbance is known as a harmonic.

The following are the main sources of harmonics in industrial applications:

**Saturable Magnetic Equipment**

There are various saturable magnetic equipment that cause harmonic problems such as:

- Rotating machines — rotating machines like induction motors may act as sources of the third harmonic currents when they are operating in abnormal or overloaded conditions.
- Ballasts of discharge lamps — the discharge lamps like mercury vapor, high-pressure sodium and fluorescent lamps are dominant sources of the third harmonic currents.
- Transformer harmonics — transformers create harmonics when they are overexcited. In addition, the transformer inrush currents may contain some even harmonics, but the duration is rather limited.
- Generator harmonics — voltage harmonics are created from the synchronous generators due to the non-sinusoidal distribution of the flux in the air gap. Selection of suitable coil-span factor (called also pitch factor) can significantly reduce the voltage harmonics from the generators.

**Power Electronic Devices**

There are various power electronic devices that cause harmonic problems such as:

- Variable Frequency Drives (VFDs) used in fans and pumps
- Switched mode power supplies (SMPS), used in instruments and personal computers
- High voltage DC transmission stations (HVDC)
- Static VAR compensator
- Uninterruptible power supply systems (UPS)
- Battery charger systems
- Flexible AC transmission systems (FACTS)
- AC and DC arc furnaces in steel manufacturing plants

**What Effects Do Harmonics Produce?**

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**Why and When to Do a Harmonic Study?**

Harmonic analysis is required when the amount of nonlinear loads is large (usually more than 25% to 30% of the total load on the bus or system) and/or there is a possibility to increase, or there has been a power quality problem on the systems. Often the capacitor bank is added without considering the resonance, so the study is needed as a corrective step. The frequent damage to power system components can also be the reason for conducting a harmonic study.

- Avoids damage due to excessive harmonic currents in transformers and capacitor banks.
- Ensures sensitive electronic equipment will not malfunction due to excessive harmonic voltage distortion.
- Satisfies the utility’s voltage and current harmonic distortion requirements.

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**Objectives and Objectives of Harmonic Studies**

**Objectives**

The standard lists following situations that may necessitate a harmonic study:

- To comply with IEEE Std 519, which defines the current distortion limits a user should meet at the Point of Common Coupling (PCC) with the utility.
- To evaluate impact on the system due to utility voltage harmonic distortion specified in IEEE Std 519.
- To investigate root causes of a system with history of harmonic-related problems, such as failure of power-factor compensation capacitors, overheating of cables, transformers, motors, etc., or mis-operation of protective relays or control devices.
- To plan and simulate a system expansion where significant nonlinear loads are added or where a significant amount of capacitance is added.
- To design a new facility or power system where the load flow, power factor compensation, and harmonic analyses are considered as one integrated study.

**Benefits**

Reasons and benefits to conduct harmonic study and analysis on industrial and commercial power systems include:

- Benchmark existing system and collect data to calibrate the model by measuring the existing system with a well-defined test plan
- Identify location, type, and magnitude of harmonic sources in the system
- Simulate impacts of these harmonic sources on system voltages and currents
- Study harmonic penetrations to the system
- Calculate voltage and current harmonic distortions on each individual frequency and Total Harmonic Distortion (THD)
- Check if there exists any violations in harmonic voltage and current distortion levels
- Calculate other harmonic indices and compare them to the standard or code limitations
- Investigate if the system has parallel or series resonance conditions
- Design harmonic filters and test harmonic filters
- Test transformer phase shift and analyze its effects on harmonic current cancellation and harmonic distortion deduction
- Test other harmonic mitigation designs and performance

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**Procedures to Conduct Harmonic Study and Analysis**

##### Reference Standards

The most common reference standards, and the majority used in the writing of this article, for conducting harmonic analysis studies are:

- IEEE 3002.8-2018:
*Recommended Practice for Conducting Harmonic Studies and Analysis of Industrial and Commercial Power Systems*. - IEEE Std 519-2014:
*Recommended Practice and Requirements for Harmonic Control in Electric Power Systems*

**Steps for Harmonic Analysis in Industrial and Commercial Systems**

The following summarizes the steps normally required for a harmonic study in the industrial and commercial environment:

- Prepare a system one-line diagram
- Gather equipment data and ratings
- Obtain the locations of nonlinear loads and the generated harmonic currents.
- Obtain from the utility company the relevant data and harmonic requirements at the PCC. These include the following:
- Minimum and maximum fault levels, or preferably system impedance, as a function of frequency for different system conditions.
- Permissible limits on harmonics including distortion factors and I-T factor.

- Carry out harmonic analysis for the base system configuration by calculating the driving point impedance loci at the harmonic source buses as well as at all shunt capacitor locations.
- Compute individual and total harmonic voltage and current distortion factors and I-T values (if required) at the Point of Common Coupling.
- Examine the results and, eventually, go back to step a) or step c), depending on whether the network data or only the parameters of the analysis need to be modified.
- Compare the composite (fundamental plus harmonic) loading requirements of shunt capacitor banks with the maximum rating permitted by the standards. IEEE Std 18™ has defined the following operating limits:
- Continuous operating voltage ≤ 110% of the rated voltage
- rms crest voltage ≤ 1.2 times the rated rms voltage
- kvar ≤ 135% of the rated kvar
- Current ≤ 180% of the rated rms currents

- Relocate the capacitors or change the bank ratings if they are found to exceed their ratings.
- Add filters if the harmonic distortion factors and I-T values at the PCC exceed the limit imposed by the utility.

The above steps should be carried out for the base system configuration as well as for system topology resulting from likely contingencies. Any future system expansion and utility short-circuit level changes should also be considered.

**Tools of Performing a Harmonic Analysis and Study**

The harmonic study can be performed by any of the following tools:

- Manual calculations, which are limited to small-size networks since they are very complicated and susceptible to errors.
- Field measurements, which are often used as a verification of the design, or as a preliminary diagnosis of a field problem.
- Digital computer simulations, which nowadays are the most convenient and economical method for analyzing system harmonics

**Required Data**

**Data for Harmonic Study
**

The following data are required for a typical industrial and commercial power system harmonic study:

- Single-line diagram
- Specific system configurations
- Maximum expected voltage for the system supplying the nonlinear loads.
- Bus nominal voltage, load adjustment factors, and voltage and current harmonic distortion limits
- Utility connecting point, three-phase and single-phase short-circuit MVA and X/R ratio or positive, negative, and zero sequence resistance and reactance.
- Rated MVA/kVA, rated voltage, negative reactance at fundamental frequency, resistance, operating mode (swing, voltage control, var control of P-Q load), winding connection and grounding type, and generation for generators.
- Rated MVA/kVA/HP, rated voltage, negative reactance at fundamental frequency, resistance, winding connection and ground type, and loading of motors.
- Transmission line and cable, length, positive, negative, and zero sequence resistance, reactance and admittance of unit length, and any special frequency characteristics of resistive, inductive, and capacitive impedance.
- Positive, negative, and zero sequence reactance and resistance, and frequency characteristics of resistance and reactance of bus duct, current limiting reactors, and other circuit elements.
- MVA/kVA rating, rated voltages, percent positive, negative and zero sequence impedance and X/R ratio, MVA/kVA rating, and three-phase connection and grounding types of power transformers.
- kvar, and unit kV ratings of shunt capacitors and shunt reactors.
- Passive load ID, bus connection, rated MVA/kVA, rated voltage, initial loading, phase connection and grounding type, and frequency characteristics of resistive, inductive, and capacitive loads.
- Nameplate ratings, number of phases, pulses, and converter connections.
- For arc furnace installations, secondary lead impedance from the transformer to the electrodes plus a loading cycle to include arc megawatts, secondary voltages, secondary current furnace transformer taps, and transformer connections.
- Harmonic filter type and structure, resistance, reactance, and capacitance for all elements, maximum voltage for capacitors, and maximum currents for inductor.
- Harmonic limits for special buses (PCC, dedicated, critical, etc.) in Total Harmonic Distortion as well as in individual harmonic.

**Data Collection and Preparation**

System modeling and data collection are vital to harmonic analysis. The following typical procedures are recommended for different types of system device, equipment, and entireties to prepare data for computer modeling and harmonic studies.

- Power grid data should be from the utility.
- Rotating machine data should be based on machine manufacturer-provided data sheet and nameplate, plus any data from available factory acceptance test, site acceptance test, and/or commissioning test.
- Load data should be from the load name plate plus any testing data.
- Line and cable data should be from the manufacturer-provided data sheet plus any testing data.
- Transformer data should be based on nameplate plus any testing data.
- Other power system component data should be based on manufacturer-provided data sheet and nameplate, plus any testing data.
- Nonlinear device voltage-current characteristics should be based on manufacturer-provided data sheet plus any special test data.
- Harmonic filter data should be based on manufacturer data sheet plus any testing data.
- Voltage and current harmonic spectrum data should be provided by the manufacturer plus any filed testing data.

**Study Report**

The harmonic study report should contain the following essential data and information about the studied system:

- System overall information such as number of buses, number of branches and branch types, number of machines, etc.
- Solution parameters including engineering data revision, system configuration, etc.
- Information on other original system input data, configuration, scenario, and solution parameter
- information
- Bus input data including bus name or ID, bus nominal voltage, bus generation and bus loading, and bus voltage harmonic distortion limit, if there are any
- Harmonic source spectrum including both magnitude and phase angle, and location
- Full fundamental load flow report
- Bus voltage total THD and individual IHD violations, if there are any
- Other harmonic indices for bus voltage and current including rms, peak (crest), TIF for bus voltages and branch currents, and I × T for branch currents
- Transformer, cable, capacitor, and filter overloading report, if there are any
- Identified parallel oscillation location, bus driving-impedance magnitude, and frequency from
- harmonic frequency scan study
- Tabulated report for harmonic voltage at each harmonic frequency for selected buses
- Tabulated report for harmonic current at each harmonic frequency for selected branches

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Contact **Omazaki Engineering** if you are looking for a consultant who serves consulting service to study and analyze harmonic disturbance in electric power systems to help with your new project or for other purposes related to your existing electrical system.

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**Related Articles**

- Power System Study & Analysis
- Load Flow Study and Analysis
- Short Circuit Study & Analysis
- Protection Coordination Study
- Motor Starting Study and Analysis
- Power System Transient Stability Study
- Arc Flash Study & Assessment
- Power Quality Study & Assessment
- Voltage Drop Study & Analysis
- Voltage Imbalance (Unbalance) Study

**References**

- IEEE 3002.8-2018 Recommended Practice for Conducting Harmonic Studies and Analysis of Industrial and Commercial Power Systems
- IEEE Std 519-2014:
*Recommended Practice and Requirements for Harmonic Control in Electric Power Systems* - Circutor,
*Procedure for The Study and The Analysis of Harmonic Disturbance*. - Harmonic Studies, http://electricaltestingsolutions.com/index.php/engineering/harmonic-studies
- JJ Dai, PhD, PE, SIEEE, Eaton Corporation Barranca Pkwy, Suite C-10, Irvine, CA, USA:
*Industrial and Commercial Power System Harmonic Studies*.

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