Comparing Partial Discharge Testing Methods: TEV vs. Ultrasound

The Importance of Partial Discharge (PD) Testing

Maintaining electrical equipment has become increasingly crucial for ensuring the reliability and safety of industrial operations. One significant concern in high-voltage electrical equipment is Partial Discharge (PD), a phenomenon that can lead to insulation failure and subsequent equipment breakdowns. Detecting PD early is essential for preventing minor faults from escalating into major issues, ultimately saving time and money while enhancing safety.

This blog post aims to educate maintenance managers and electrical engineers on the differences between two prominent PD testing methods: Transient Earth Voltage (TEV) and Ultrasound. By comparing their effectiveness, applications, limitations, and operational impacts, we hope to help you make informed decisions about your PD monitoring strategy.

What is Partial Discharge (PD)?

Defining Partial Discharge (PD)

Partial Discharge is a localized dielectric breakdown in a small portion of electrical insulation that doesn't completely bridge the space between conductors. Often occurring due to imperfections, voids, or contamination in the insulation material, PD leads to small electrical sparks.

Causes and Consequences of PD

PD can be caused by several factors, including manufacturing defects, installation issues, environmental stress, and aging of the insulation material. If left unchecked, PD can lead to the gradual deterioration of insulation, resulting in equipment failure, unplanned outages, and potentially hazardous conditions for personnel.

The Critical Need for Early Detection

Early detection of PD is crucial for maintaining electrical equipment reliability. Regular PD monitoring allows for timely intervention, preventing minor issues from escalating into major failures. For a more detailed look at the impact of Partial Discharge on electrical systems, click here.

How TEV (Transient Earth Voltage) Detection Works

Overview of TEV Detection

TEV detection involves capturing transient voltage signals emitted by partial discharges. These signals are electromagnetic pulses that propagate along the earth conductor when a discharge occurs. TEV sensors, placed on the surface of the electrical equipment, detect these pulses, providing insights into the presence and severity of PD.

Applications of TEV Detection

This method is particularly effective for identifying internal discharges within metal-clad switchgear and other enclosed electrical apparatus. It is non-intrusive and can be performed under normal operating conditions, making it suitable for continuous monitoring without disrupting operations. Additionally, TEV detection complies with international standards such as IEC 60276 and IEEE C57.104-2003, ensuring reliable and consistent results.

Limitations of TEV Detection

While TEV detection is highly effective for internal discharges, it may not be as effective in environments with high electromagnetic interference. Its sensitivity can be limited when used for surface discharges or in open environments where signal attenuation may occur. Accurate placement of the sensor is crucial; it needs to be near vents, openings, or joints to effectively capture the transient voltage pulses. Moreover, TEV detection might struggle with noise interference and may not detect low-level PD effectively. It is also noted that interpreting TEV data can require significant expertise and experience to differentiate between PD signals and noise.

Understanding Ultrasound Detection

Mechanics of Ultrasound Detection

Ultrasound detection monitors the acoustic emissions from PD activity. Partial discharges emit ultrasonic waves, which are sound waves at frequencies above the range of human hearing. Ultrasonic sensors capture these high-frequency sounds and analyze them to detect PD.

Versatility and Applications of Ultrasound Detection

Ultrasound detection is versatile and can be used across various types of electrical equipment, including transformers, cables, and switchgear. It is particularly effective for surface PD detection and can be used in conjunction with other methods for a comprehensive PD assessment. Its real-time, non-intrusive inspection capability makes it effective even in noisy environments.

Limitations of Ultrasound Detection

One limitation of ultrasound detection is the requirement for an air path to detect surface PD accurately. If the panel is airtight, actions might be needed to create an air path, such as removing screws and detecting through screw holes. This means that inspections may sometimes necessitate closer physical access to the equipment, which could be challenging in certain operational environments. While ultrasound is effective in noisy environments, extremely high levels of ambient noise can still interfere with detection. Additionally, traditional ultrasonic transducers can be susceptible to strong electromagnetic interference, and high-frequency signal attenuation can limit detection range.

Comparing TEV and Ultrasound Detection Methods

Detection Range and Sensitivity

TEV detection is effective for detecting internal discharges within metal-clad equipment by capturing electromagnetic pulses. It provides clear indications of insulation integrity, making it ideal for assessing the condition of enclosed electrical apparatus such as metal-clad switchgear. On the other hand, ultrasound detection is highly effective for surface PD detection. It pinpoints the exact location of discharge activity by capturing acoustic emissions, making it suitable for various types of electrical equipment.

Application in Different Scenarios

TEV is best suited for assessing the condition of enclosed electrical apparatus and can be integrated into a preventive maintenance program to monitor insulation health over time. Ultrasound detection is particularly useful in environments with high electromagnetic interference where TEV may be less effective.

Operational Impact and Considerations

From an operational standpoint, both methods are non-intrusive and can be performed under normal operating conditions, making them ideal for continuous monitoring without disrupting operations. However, ultrasound detection may require proximity to the equipment for accurate detection, which could be a consideration depending on the specific application.

Conclusion and Next Steps

Both TEV and ultrasound detection methods offer valuable insights into the condition of electrical insulation and are essential tools for preventive maintenance programs. TEV is ideal for detecting internal discharges in enclosed equipment, while ultrasound excels in identifying surface discharges and providing precise localization of PD activity. By combining these methods, you can achieve a comprehensive assessment, ensuring the early detection and remediation of potential faults to maintain electrical system reliability and safety.

To ensure the early detection of potential faults and maintain the reliability of your electrical systems, schedule a consultation with our expert team today. Contact us to get a free quote and safeguard your operations against costly disruptions. For more information on our on-site and in-service TEV and Ultrasound assessment services, click here.