Partial Discharge (PD) Testing for Electrical Cables and Switch Gear Panels

Partial discharge (PD) testing is a nondestructive test for assessing the health of electrical insulation systems. It involves identifying the failure of specific insulation components to resist the applied electrical field, caused by factors such as deterioration, poor design, workmanship, inadequate materials, and sludge.

Technomax has extensive experience in Partial Discharge testing in UAE & Middle East and provides equipment with various measurement technologies tailored to different PD testing applications. Over the years, this testing technique has gained widespread recognition for its effectiveness in assessing the condition of electrical assets. Our online testing methods are non-invasive and non-destructive, making them ideal for condition monitoring without disrupting operations. A wide range of electrical assets from 3kV to 700kV and above can now be evaluated using online methods.

If you are looking for partial discharge testing in UAE or Middle East, partner with Technomax for reliable testing.

What is Partial Discharge?

Partial discharge is a sign of the degradation of the insulation system. Partial discharges (PD) refer to minor electrical sparks happening within the insulation of medium and high voltage electrical assets. Each specific partial discharge occurs when there’s an electrical breakdown in an air pocket within the insulation, gradually wearing down the insulation and leading to eventual failure. Conducting Partial Discharge Testing also recognized as PD testing, is crucial for evaluating the electrical insulation’s health.

The outcomes of Partial Discharge Testing play a key role in forecasting the future performance and reliability of vital assets. Assets that can be tested include:

Motors and generators
Switchgear
Air-insulated components such as insulators, surge arresters, and bushings
Power cables, both paper-insulated and extruded types

These assessments can be done without requiring a shutdown, making them ideal for preventive maintenance and real-time diagnostics.

Types Of Partial Discharge

Partial discharge breakdown of insulation results in various effects, including rays, warmth, scent, sound, electromagnetic waves, and high-frequency electric current. It can occur in different types of insulation (air, oil, solid, GIS) and at various voltage levels (from 3kV to 769kV and beyond). The three main types of partial discharge are:
Surface Partial Discharge: The most common form, occurring across the surface of the insulation, is influenced by environmental factors humidity, temperature and pollution.
Internal Partial Discharge: These discharges happen within f defects or voids within solid insulation.
Corona Partial Discharge: Occurs in gaseous dielectrics when inhomogeneous fields are present, often involving discharges from conductors into the surrounding air.
Treeing: Treeing is a progressive degradation phenomenon in solid insulation characterized by the development of branching, tree-like patterns. It typically initiates from microscopic voids, inclusions, or material imperfections and propagates under sustained electrical stress. The two main types of treeing are electrical treeing, caused by high electrical fields, and water treeing, influenced by moisture ingress.
Void Discharge: Void discharge refers to partial discharges that occur within gaseous voids embedded in solid or liquid insulation materials. These internal cavities act as field intensifiers, where the local electric field can exceed the dielectric strength of the enclosed gas, resulting in ionization.

Benefits of Partial Discharge Testing

Why is Partial Discharge Monitoring Critical?

Partial discharge (PD) testing plays a vital role in ensuring the operational integrity and safety of electrical assets, particularly transformers.

Early Fault Identification: Detects insulation defects at an early stage, allowing timely intervention before they escalate into major failures. This proactive approach contributes to improved equipment longevity.
Condition-Based Maintenance: Supports predictive maintenance strategies by providing real-time insights into equipment health, thereby reducing unexpected breakdowns and operational interruptions.
Prolonged Equipment Lifespan: Regular PD monitoring helps preserve insulation integrity, effectively extending the service life of electrical components.
Enhanced Operational Safety: Lowers the likelihood of electrical faults that may pose serious safety risks to personnel and infrastructure.
Reduced Maintenance Costs: By identifying potential issues early, PD testing helps avoid expensive repairs and unplanned downtime, optimizing maintenance budgets.

PD Testing : Advancements in Non-Invasive Techniques

Partial discharge (PD) testing has experienced significant advancements in online non-invasive and non-destructive techniques. These cutting-edge methods provide in-depth condition assessment without disrupting the system’s operation. In this article, we will explore these techniques in detail and highlight their numerous benefits.

Online Partial Discharge (PD) Testing in Power Cables

Partial discharge occurs when insulation defects arise in power cables. Implementing online monitoring for partial discharge (PD) is an effective method to maintain the reliability of electrical power systems. This technique allows for the detection of insulation failures at joints and terminations, which, if left unaddressed, can result in extended power outages. Factors contributing to partial discharge in power cables include weak insulation areas, such as particles, voids, or cracks, as well as damage to the cables or their accessories.

By strategically placing appropriate sensors at the cable system’s terminations and joints, partial discharge can be monitored either on a temporary or continuous basis. Furthermore, utilizing advanced noise suppression techniques and algorithms for separating partial discharge sources can help accurately pinpoint hazardous discharges within the cable system.

PD Testing Solutions from Technomax

Technomax is the official UAE distributor of IPEC Limited’s advanced Partial Discharge (PD) technologies. IPEC is renowned globally for monitoring, testing, and locating PD in medium to high-voltage electrical systems.

Key Offering Highlights:

Portable PD Testing Tools

PD Detector Pro

Handheld devices like PD‑SGS, PD Detector, and PD‑SG1 support spot‑testing with PD detection, PRPD noise filtering, data logging, and synchronization. Compatible with TEV, HFCT, and UHF sensors for switchgear, cable, transformer, and other electrical asset inspections.

Permanent PD Monitoring Systems

PD monitoring System

Scalable solutions ranging from entry-level monitoring to high-channel-count installations. Features include fast data capture, IPEC’s proprietary DeciFer algorithm to distinguish PD from interference, and web‑based access via the ISM portal.

Non-Intrusive PD Sensors

Sensor types include AA Ultrasonic, CC‑TEV capacitive couplers, HFCT, and UHF models. Designed for safe, easy retrofit installation on existing high-voltage equipment with long service life.

Effective Methods for Partial Discharge (PD) Testing

Gaining a solid understanding of various partial discharge (PD) testing techniques is essential for maintaining the reliability and extending the service life of electrical equipment. These testing approaches are generally divided into two categories: offline and online methods, each offering unique benefits and specific uses.

Offline PD Testing Methods

Oscillating Wave Test (OWT): This technique uses oscillating voltage signals to evaluate the condition of insulation systems when the equipment is powered down. It is especially useful for locating weak points in insulation.
Very Low Frequency (VLF) Testing: In this approach, low-frequency sinusoidal voltages are applied to test the insulation strength of high-capacitance components such as power cables and transformers. VLF testing is particularly suited for this type of equipment due to its efficiency and accuracy.

Online Testing Methods

Acoustic Emission Testing: This method identifies PD activity by capturing and analyzing the sound waves produced by discharges. Sensors placed on the equipment detect these acoustic signals, allowing for non-invasive monitoring.
Transient Earth Voltage (TEV) Testing: TEV testing monitors transient voltage signals caused by partial discharges. Sensors placed on the surface of the equipment can detect these signals without requiring intrusive procedures, making this an effective way to track PD activity during operation.
High-Frequency Current Transformer (HFCT) Testing: This technique captures the high-frequency current generated by PD events. HFCT sensors are positioned around conductors to pick up discharge-related signals, helping to determine both the location and intensity of the discharge.

Partial Discharge (PD) Testing From Technomax

At Technomax, we specialize in Online partial discharge testing, offering advanced techniques for accurate electrical inspection and monitoring services for health assessment. Our team of PD experts provides local support, installation, and ongoing technical assistance tailored to client needs. Contact us today to explore our partial discharge testing services and safeguard the health of your electrical infrastructure. Trust in Technomax for expertise and excellence in our condition monitoring services & partial discharge testing. What we offer includes:

Routine online PD spot testing of switchgear, transformers, and cable systems.
Continuous condition monitoring in industrial, utility, or substation environments.
Preventive maintenance strategies aimed at insulation diagnostics, risk mitigation, and asset protection.

Protect Your Assets with Trusted PD Testing Solutions – Get in Touch with Our Team

Discover Our Case Study in Partial Discharge Testing

FAQs

What is the standard for partial discharge testing?

The main international guideline for conducting partial discharge (PD) tests is IEC 60270, titled High-voltage test techniques – Partial discharge measurements. This standard outlines the terminology, measurement parameters, testing setups, calibration procedures, and testing methods for detecting PD in electrical equipment operating under AC voltages up to 400 Hz or DC voltages.

2. What is the principle of partial discharge?

Partial discharge refers to a localised failure in the insulation of electrical components. It occurs when part of the insulation experiences an electrical breakdown without a complete arc forming between conductors. This typically happens when the electric field intensity at a defect such as a void or impurity surpasses the insulating material’s strength. This leads to small and rapid discharges that can gradually damage the insulation.

3. How is partial discharge detected?
PD detection involves various techniques such as ultrasonic sensing, radio frequency (RF) analysis, and ultraviolet (UV) monitoring. Advanced equipment like acoustic imaging tools can translate ultrasonic signals from PD activity into visual representations. This allowing technicians to pinpoint and document discharge locations from a safe distance for evaluation and maintenance planning.

4. What is the IEC standard for partial discharge testing?
IEC 60270 is the recognized international standard for PD testing, titled High-voltage test techniques – Partial discharge measurements. It establishes the methodologies, measurement systems, circuit configurations, and calibration techniques necessary for assessing partial discharge in the insulation of high-voltage electrical equipment.

FAQs

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