Comprehensive Guide to Power Quality: Voltage, Frequency, and Harmonics

Introduction

In the backup power system, there are various methods to achieve high-quality results. For high efficiency, you have to feed the quality power and expect lower fuel consumption. Now, you might wonder what exactly quality power is.

We will elaborate on the quality power, understand how it works, and know the comprehensive details of the power quality.

What is Power Quality?

Power quality refers to the power supply that matches closely to its ideal features. Here are a few qualities of the power.

• Stable voltage
• Constant frequency
• Pure sinusoidal waveform
• Balanced three-phase supply
• Minimal electrical disturbances

If any of these factors go beyond the required limits, it causes power issues and decreases the efficiency of the Generators.

Why Does Power Quality Matter?

How is power different from quality power? What happens if you use low-quality power? If you have the same questions, there can be several issues with using low-quality power systems.

Here are a few issues related to low power quality.

• Unexpected production downtime
• Motor overheating
• Transformer overheating
• Frequent circuit breaker trips
• Flickering lights
• Data loss in computers
• UPS alarms
• Increased maintenance costs
• Reduced energy efficiency
• Shorter equipment lifespan
• Higher operating expenses

Factor #1: Comprehensive Guide to Voltage

Voltage is one of the key parameters often discussed. It is the push of the current that lets the current pass through the system; whether high or low voltage is beyond the threshold causes issues with the devices and systems.

Here are a few recommended options.

Types of Voltage Problems

Voltage issues can be several. But we have added a few of the most important types to know.

Voltage Sag

Voltage sag refers to the voltage being lower than the normal voltage limits. Voltage sag is temporary and occurs for a short period lasting a few milliseconds to a few seconds.

There can be several issues with voltage sags listed below.

• Motor starting
• Generator Overload
• Short circuits
• Large industrial loads
• Utility faults

There are a few common effects listed below.

• PLC shutdown
• Contactor dropout
• Motor torque reduction
• Conveyor stoppage
• Computer reboot

Voltage Swell

Voltage swell is a temporary increase in the voltage above its normal limits. Compared to longer periods, it is a short period and returns to normal voltage early.

Common reasons for a voltage swell are:

• Sudden load removal
• Incorrect transformer tap settings
• Utility switching
• Generator regulation problems

There can be a significant impact on the system. The examples are:

• Equipment overheating
• Capacitor failure
• Reduced insulation life
• Electronic component damage

Over voltage

Overvoltage means the voltage remains above the specified ratio for more than a period of voltage swell. Overvoltage can be an issue, especially related to compatibility.

Possible causes:

• Incorrect generator AVR settings
• Transformer tap errors
• Utility regulation issues

Possible impacts:

Here are a few issues related to the overvoltage of the system.

• Premature equipment failure
• Increased insulation stress
• Shortened motor life

Undervoltage

Undervoltage is a significant issue in which voltage remains below the threshold for extended periods. There are a few common issues and symptoms mentioned.

• Long feeder cables
• Overloaded transformers
• Generator overload
• Weak utility supply

Common Symptoms

• Motors draw more current
• Lights become dim
• Equipment trips
• Poor machine performance

Voltage Stability in Power Systems

Voltage stability is essential for a system to perform. Constantly fluctuating voltage always causes issues with the system.

Usually, systems have electrical interferences, resistances, and many more issues. We have discussed the most important factors and options for a stable voltage.

Factors Affecting Stable Voltage

A system can present several challenges in maintaining stable voltage. The common factors affecting the voltage are:

• Heavy loading

Loading systems above the required limits causes issues with the current, voltage, and resistance. It can even shut down systems.

• Long transmission distances

When transmitting power over long distances, there are voltage losses due to the long distance. As you increase the distance, voltage losses increase.

• Weak generators

Weak generators have a low built-in capacity to generate the voltage. They can produce fluctuating voltages and cause issues.

• Reactive power deficiency

Power deficiency fails to maintain stable voltage and often interferes with fluctuating voltage systems.

• Poor transformer regulation

Transformers are often required to regulate and supply voltage to a wider area. When distribution occurs, due to transformer issues, voltage drops can occur and shut down the system.

Maintaining Stable Voltage

Maintaining Stable Voltage is crucial for a system to operate and perform efficiently.

There are different facilities and systems that can help regulate the voltage and make it stable. Here are a few common methods often used in the system for voltage regulation.

• Automatic Voltage Regulators (AVRs)
• Transformer tap changers
• Capacitor banks
• Static VAR compensators
• Synchronous condensers
• Voltage regulators

Factor #2: Comprehensive Guide to Frequency

Frequency is the number of cycles alternating current occurs each second. Different countries and systems have different frequencies.

However, it is crucial to maintain the frequency when the generator is connected to the utility grid systems.

Here are a few frequency examples.

• 50 Hz
• 60 Hz

Standard power frequencies are given below.

Why Does Frequency Matter?

Frequency is the balance between the electrical generation and demand. It offers a stable performance when it remains optimal throughout the energy generation process.

Without a stable frequency, there can be automated shutdowns, short circuits, and many more issues with the following equipment.

• Diesel generators
• Gas generators
• Turbines
• Induction motors
• Synchronous motors
• Pumps
• Compressors
• Industrial drives
• Manufacturing equipment

Frequency Deviations

There can be either high frequency or low frequency. We have discussed both options below.

Low Frequency

In low frequency, electrical demands exceed the available energy. There can be a few possible causes and results listed below.

Possible causes can be the following.

• Generator overload
• Large industrial loads
• Power plant trip
• Grid disturbance

Here are a few effects of low-frequency systems.

• Motor speed reduction
• Increased heating
• Generator instability
• Equipment shutdown

High Frequency

High frequency occurs when generation exceeds the electrical demands.

There are a few causes and effects listed below.

Possible causes

• Sudden load rejection
• Governor malfunction
• Small isolated power systems

Effects

• Overspeed conditions
• Mechanical stress
• Generator protection trips
• Equipment damage

Acceptable Frequency Limits

Common Causes of Frequency Instability

Frequency instability is always an issue. There can be a few related issues that cause the frequency instability.

Generator-Related Causes

In generator systems, frequency alterations occur due to the following issues.

• Governor malfunction
• Fuel supply problems
• Incorrect engine speed
• Mechanical failures
• Load sharing errors

Grid-Related Causes

When the system is connected to the utility grid, there can be grid-related issues as well. Here are a few issues causing frequency instability.

• Generator outage
• Transmission faults
• Rapid load growth
• Renewable energy fluctuations
• Grid instability

Voltage vs Frequency

Voltage and frequency are the key factors in the system, but they share a few differences. Here are these.

Factor #3: Comprehensive Guide to Harmonics

Generators and many other devices often operate through the AC current that alternates every second. However, many modern devices operate at short pulses of current rather than a continuous waveform. Therefore, short pulses create a distortion called harmonics.

It is a multiple of the frequency of 50 or 60Hz. For example:

• Fundamental frequency: 50 Hz or 60 Hz
• 2nd harmonic: 100 Hz (or 120 Hz)
• 3rd harmonic: 150 Hz (or 180 Hz)
• 5th harmonic: 250 Hz (or 300 Hz)
• 7th harmonic: 350 Hz (or 420 Hz)

Common Sources of Harmonics

Many non-linear loads generate harmonics. Here are a few common sources of harmonics.

• Variable Frequency Drives (VFDs)
• Uninterruptible Power Supplies (UPS)
• Switch-mode power supplies (SMPS)
• LED lighting systems
• Computer servers
• Battery chargers
• Solar inverters
• EV charging stations
• Arc furnaces
• Welding machines
• Rectifiers
• Adjustable speed drives

Common Harmonic-Producing Equipment

Every piece of equipment produces a different range of harmonics. It can be high, low, or medium harmonics.

Here are a few pieces of equipment with their harmonic production ranges.

Effects of Harmonics on Different Equipment

Harmonics have several impacts on different tools and equipment. We have listed all the tools with their necessary impact.

Motors

Harmonics significantly impact the copper and iron of the motor and cause losses. It involves overheating and many more issues listed below.

• Excessive heating
• Reduced efficiency
• Increased vibration
• Lower torque
• Insulation deterioration
• Premature bearing failure

Transformers

Eddy current losses are typical in transformers due to harmonics. It causes overheating and many more issues listed below.

• Hot spots
• Reduced insulation life
• Lower transformer capacity
• Increased cooling requirements
• Premature failure

Generators

Generators are one of the most sensitive tools to harmonics. They cause issues such as:

• Voltage waveform distortion
• Rotor heating
• Reduced efficiency
• AVR instability
• Increased fuel consumption under distorted loads

Capacitor Banks

Capacitor Banks are storage setups. They also get affected by the harmonic frequencies. Here are a few impacts of the capacitor banks.

• Overheating
• Fuse operation
• Capacitor swelling
• Dielectric failure
• Reduced service life

Neutral Conductors

Triplen harmonics add up in the neutral conductors and have the following impacts.

• Neutral conductor overheating
• Cable insulation damage
• Fire hazards
• Excessive voltage drop

IEEE 519 Harmonic Standard

It is one of the most reliable and famous standards used for harmonics. The specified limits of the harmonics are listed below.

FAQs

• How can voltage sags be prevented?

To avoid poor-quality voltage sags, you should use soft starters, variable frequency drives, voltage regulators, adequately sized generators, and properly designed distribution systems.

• What is Total Harmonic Distortion (THD)?

Total harmonic distortion is the waveform distortion. It measures values by comparing the harmonic frequency with the fundamental frequency. Lower total harmonic distortion means better power quality.

• Why is harmonic distortion harmful?

Harmonic distortion causes several issues. For example, it increases heating, reduces equipment efficiency, shortens the lifespan of motors and transformers, causes nuisance tripping, and can interfere with sensitive electronic devices.

• What are harmonics in an electrical system?

Harmonics are voltage or current components that are multiples of the fundamental frequency (50 Hz or 60 Hz).

• What causes poor power quality?

For poor power quality, there can be several issues related to voltage, frequency, or harmonics. The common examples are voltage sags, swells, frequency deviations, harmonic distortion, overloaded circuits, faulty generators, non-linear loads, and utility disturbances.

• What industries are most affected by power quality issues?

There are a few industries that are extremely affected by power quality issues. The examples are manufacturing plants, hospitals, data centres, mining operations, oil and gas facilities, commercial buildings, renewable energy plants, and water treatment facilities.

• How do active harmonic filters improve power quality?

Active harmonic filters detect the unwanted currents and cancel them by injecting equal and opposite currents.

• What instruments are used to measure power quality?

There can be several instruments causing power quality issues, such as power quality analysers, digital power meters, oscilloscopes, harmonic analysers, clamp meters, energy meters, data loggers, and thermal cameras.

Conclusion

Whenever choosing a generator, you must focus on the power quality factors. Ensure it operates at a stable voltage, offers decreased harmonics, and provides a stable current supply. Therefore, you should prefer reputed brands for generator selection.

Huaquan Power is one of the top-notch brands that has premium-quality generators. Our generators feature high efficiency, low fuel consumption, and enable stable performance over longer periods. Contact our experts to get a quote!