What Are Partial Discharges (PD)?

Reliable Partial Discharge Measurement Devices for Electrical Safety

Definition of PD

Partial discharges are localized electrical discharges that do not completely bridge the insulation between conductors. What these micro-arcs can do in various parts of electrical insulation systems can differ widely, they occur inside material likely;

• Inside insulation cavities

• On dielectric surfaces

• Along sharp edges

• Parallel to insulation layers

Even small PD events can lead to long-term degradation of insulation. That’s why early detection of PD is critical for ensuring the reliability and safety of electrical systems.

Why Detect Partial Discharges?

Detecting PD prevents electrical insulation failure before it leads to costly outages or equipment damage. non-destructive partial discharge testing devices are engineered to:

• Detect PD activity in real-time

• Identify weak spots before failure

• Help maintain electrical equipment health over time

Types of Partial Discharges (According to IEC 60270)

IEC 60270 classifies PDs into two main categories:

• Internal PDs: Occur within insulating materials

• External PDs: Occur on the surface of insulators

PDs can also behave as:

• Continuous discharges

• Intermittent events

Common Causes of Partial Discharge

Partial discharges can result from multiple physical and design-related factors:

• Aged or contaminated insulation

• Flawed insulation geometry or design

• High electric field stress

• Manufacturing imperfections

PD Detection Methods: Choose the Right Technology

Based on these information we can have devices that support several PD detection techniques, optimized for different test environments:

IEC 60270-Compliant PD Measurement Technology

For complying fully with IEC 60270 we can incorporate two industry-standard test circuit options:

1. Straight Detection Method

• Uses a coupling capacitor (Ck) and measuring impedance (Zm)

• Converts transient PD signals into voltage pulses

• Best for on-site field applications

2. Balanced Bridge Configuration

• Suppresses common-mode noise

• Enhances sensitivity

• Preferred for lab and R&D settings

Applications of PD Measurement

Partial discharge detection and monitoring systems are widely used in:

• Power transformers

• Gas-insulated and air-insulated switchgears

• Cables, joints, and terminations

• Rotating electrical machines (motors, generators)

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