Harmonic Mitigating Transformer: How Improve Your Power Quality

In power distribution systems, nonlinear loads are prone to generating distorted harmonics. These harmonics may cause numerous problems, including equipment overheating, increased energy loss, reduced equipment lifespan, and even increased downtime.

Harmonic mitigating transformers are the best solution to this problem. Regardless of load size, they suppress harmful harmonics in your passive components, improving efficiency, energy savings, and reliability.

Table of Contents:

1. What Are Harmonics?

2. What Causes Harmonics?

3. How Do Harmonics Affect Transformers?

4. What Harmonic Distortions Are Generated By Modern Power Systems?

5. What Is a Harmonic Mitigating Transformer?

6. How Harmonic Mitigating Transformer Effect on Harmonics?

7. Which Devices Require the Harmonic Mitigating Transformer?

8. What Electrical Problems Can the Harmonic Mitigating Transformer Solve?

9. How Harmonic Mitigating Transformers Outperform K-Rated Transformers?

9. How Harmonic Mitigating Transformers Outperform K-Rated Transformers?

10. How Harmonic Mitigating Transformers Work?

11. What Are the Types of Harmonic Mitigating Transformers?

12. How Harmonic Mitigating Transformers Help You Improve Power Quality?

13. Future Trends in Power Quality Management

1. What Are Harmonics?

What Are Harmonics-sourced: pqcomponents

In power systems, electrical signals are typically sinusoidal to assist various electrical devices in performing their functions, such as lighting, driving motors, printing, and running computer programs.

Generally, in a 60 Hz system, the normal current waveform fluctuates up and down 60 times per second. However, the harmonic frequencies generated by the load are even higher. The third harmonic has a frequency of 180 Hz, and the fifth harmonic has a frequency of 300 Hz, representing harmonic wave-forms cycling at frequencies of 180 and 300 times per second, respectively.

2. What Causes Harmonics?

To understand the causes of harmonics, we need to understand linear and nonlinear loads in a system. Both are ways in which equipment in a power system consumes power. Specifically:

Linear Loads

Linear Loads-sourced: powerquality

The power consumption of linear loads generally resembles a sinusoidal waveform. Linear loads typically include motors or incandescent light bulbs.

Nonlinear Loads

Nonlinear Loads-sourced: actionpowertest

The alternating current waves generated by nonlinear loads do not conform to a sinusoidal waveform. They generate harmonics during power consumption. These harmonics are generally generated by devices such as frequency converters, rectifiers, and other modern electronic equipment, and easily cause voltage and current distortion.

Typical sources of harmonics include:

Typical sources of harmonics-sourced: megawatts

Variable frequency drives (VFDs), uninterruptible power supplies (UPS), server racks, LED lighting, electric vehicle chargers, and switching power supplies.

3. How Do Harmonics Affect Transformers?

How Do Harmonics Affect Transformers-sourced: grwinding

During transformer operation, harmonics from nonlinear loads can easily increase winding and core losses, leading to overheating or power loss. Specifically:

Increased Resistance and Heat

The transformer consists of windings and a core. During operation, harmonics move and accumulate towards the outer edges of the conductors, exacerbating heat buildup in the closely packed coils, resulting in increased transformer resistance and heat.

Increased Core Loss

With alternating current directions, the polarity of the excitation current in the core changes under the influence of high-frequency harmonics. The higher the frequency of the excitation current change, the greater the core heat loss, hence the term hysteresis loss.

Temperature Increase

Harmonics induce eddy currents (tiny rotating currents) in the equipment, further aggravating transformer heat loss and increasing equipment temperature.

Reduced Current Carrying Capacity

3rd, 9th, and 15th harmonics can cause overheating of the neutral conductor, leading to insulation failure and ultimately reducing current carrying capacity.

4. What Harmonic Distortions Are Generated By Modern Power Systems?

Generally, nonlinear loads generate harmonics that are integer multiples of the fundamental frequency (60 Hz), thus affecting transformer operation. These include:

Triple Harmonics

Triple Harmonics-sourced: electrical-engineering

Third harmonics include the 3rd, 9th, and 15th harmonics, with frequencies of 180 Hz, 540 Hz, and 900 Hz, respectively. These harmful harmonics superimpose onto the neutral line, causing an increase in neutral line current.

Fifth and Seventh Harmonics

Fifth and Seventh Harmonics-sourced: norwall

Fifth and seventh harmonics have frequencies of 300 Hz and 420 Hz, respectively. These harmful harmonics increase stray magnetic flux, leading to additional eddy current heating.

5. What Is a Harmonic Mitigating Transformer?

What Is a Harmonic Mitigating Transformer-sourced: LTEC

A harmonic mitigating transformer is a type of dry-type transformer. It eliminates harmonic currents through a special winding structure, phase shift, and zero-sequence impedance control.

Unlike passive filters that absorb harmonics, or K-rated transformers that can only withstand harmonics, it utilizes the vector and phase relationships within the transformer windings to prevent superimposed harmonic currents from flowing into the upstream system, thereby reducing harmonic distortion.

6. How Harmonic Mitigating Transformer Effect on Harmonics?

How Harmonic Mitigating Transformer Effect on Harmonics-sourced: maddox

By utilizing a harmonic mitigating transformer, harmonics generated by nonlinear loads within the system are reduced and eliminated. Its benefits include:

• Reduced heat generation, ensuring full utilization of the transformer's rated capacity;
• Preventing system overheating and excessively high temperatures;

Its advantages include:

7. Which Devices Require the Harmonic Mitigating Transformer?

Which Devices Require the Harmonic Mitigating Transformer-sourced: hammondpowersolutions

Generally, the increase of nonlinear loads in power systems, such as servers, UPS systems, LED lighting, computers, and frequency converters, easily generates harmonic distortion, leading to increased transformer heating, reduced efficiency, and increased energy consumption.

Therefore, in power systems with these linear loads, the configuration of harmonic mitigating transformers is required to help reduce and eliminate harmonics in the system.

8. What Electrical Problems Can the Harmonic Mitigating Transformer Solve?

In addition to reducing or eliminating harmonics in the system, it can also solve:

• Overheating of the neutral line or feeder;
• Upstream voltage distortion approaching limits.
• Single-phase electronic load dominance;

When encountering the above problems, before providing harmonic mitigating transformer solutions, you need to fully consider various factors such as load distribution, phase balance, grounding method, transformer connections, and other harmonic suppression equipment in the system to ensure the correct solution.

9. How Harmonic Mitigating Transformers Outperform K-Rated Transformers?

Harmonic Mitigating Transformer VS K-rated Transformer:

10. How Harmonic Mitigating Transformers Work?

The operating characteristics of harmonic mitigating transformers primarily depend on their winding geometry, core design, and engineered phase shift. These include:

Triplen Harmonic Suppression

Triplen Harmonic Suppression-sourced: capacitorconnect

In the design of third harmonic suppression schemes, harmonic mitigating transformers mainly utilize zigzag, delta-zigzag, or special double-secondary winding configurations. This is achieved by redirecting the current to cancel out the third harmonic.

5th and 7th Harmonic Cancellation

5th and 7th Harmonic Cancellation-sourced: physicsforums

Due to the 180° phase difference between the 5th and 7th harmonic currents and the different secondary output phases of the harmonic mitigating transformer, cancellation of the 5th and 7th harmonics is possible.

The main design principles of harmonic mitigating transformers include:

• Optimized core geometry
• Reduced zero-sequence impedance
• Special winding arrangements
• Controllable magnetic flux paths

11. What Are the Types of Harmonic Mitigating Transformers?

The type of harmonic mitigating transformer is primarily determined by the installation environment, and includes:

Triple Harmonic Canceling Type - HMT

This type of transformer mainly addresses voltage distortion problems caused by triple harmonics (3rd, 9th, and 15th harmonics), and is suitable for environments primarily using single-phase electronic loads, such as offices and IT data centers.

Phase-Shift/Multi-Pulse HMT

Phase-Shift/Multi-Pulse HMT-sourced: ytelect

This type of transformer mainly addresses problems caused by the 5th and 7th harmonics. By setting a certain phase difference between the secondary outputs, the 5th and 7th harmonics are naturally canceled out.

12. How Harmonic Mitigating Transformers Help You Improve Power Quality?

Harmonic mitigating transformers improve your power quality in the following ways:

Reducing Neutral Current

Neutral Current-sourced: zddqelectric

During operation, harmonic mitigating transformers significantly reduce the heating of the neutral conductor, thereby reducing the neutral current.

Reducing Transformer Heating

Transformer Heating-sourced: maddox

Harmonic mitigating transformers reduce stray losses and eddy current losses caused by harmonics, thus lowering the operating temperature of the equipment and reducing transformer heating.

Improving Upstream Power Quality

Upstream Power Quality-sourced: circutor

For sensitive equipment in the system, harmonic mitigating transformers reduce and eliminate voltage distortion caused by harmonic currents, allowing the system to connect better to the PCC (Point of Common Coupling).

Increasing System Available Capacity

By reducing and eliminating harmonics in the system, harmonic mitigating transformers free up more capacity, facilitating the connection of other loads.

Extending Equipment Lifespan

By eliminating harmonics in the system and reducing equipment temperature, HMTs extend the lifespan of the equipment.

13. Future Trends in Power Quality Management

Under the growing trend of HMT (Harmonic Mitigation Technology), it is predicted that future power quality management will gradually develop in the following aspects:

Intelligent Monitoring Systems

Intelligent Monitoring Systems-sourced: electroind

System harmonics will be monitored and synchronized by intelligent monitoring systems, facilitating subsequent adjustments and improvements.

AI-based Predictive Maintenance

AI-based Predictive Maintenance-sourced: infinite-uptime

Through operational testing, artificial intelligence can be used to predict system power quality and failure rates, facilitating future maintenance.

Renewable Energy Integration Systems

Renewable Energy Integration Systems-sourced: pnnl

The future trend will be towards more efficient and reliable renewable energy integration systems.

Conclusion:

To address the growing challenges of harmonics in modern electrical systems, HMT is a passive yet effective solution. By reducing system harmonics and improving overall power quality, it becomes a long-term, reliable workhorse for the system. To obtain the detailed technical specifications or discuss a custom engineering solution for your specific application, please contact our engineering department.