Accurate Partial Discharge Measurements Begin with Proper Calibration
Partial discharge (PD) testing plays a critical role in evaluating the condition of high-voltage insulation systems. From transformers and power cables to rotating machines and switchgear, detecting partial discharge activity early helps engineers identify insulation defects before they develop into costly equipment failures.
However, obtaining meaningful PD measurements requires more than sophisticated detection equipment. Before test results can be trusted, the measurement system must be properly calibrated to ensure accuracy, repeatability, and compliance with industry standards such as IEC 60270.
That’s where PD calibrators come in. By establishing a reliable reference before testing begins, they help engineers verify measurement performance and build confidence in the results used to assess the health of critical electrical assets.
What Is a PD Calibrator?
A PD calibrator is a precision instrument that injects a known electrical charge into a partial discharge measurement circuit. This calibrated reference signal allows engineers to verify that the measurement system accurately detects and reports apparent charge before testing begins.
Rather than measuring the discharge itself, the calibrator verifies the performance of the entire measurement chain, including the detector, coupling device, measuring impedance, and associated cabling. This process establishes confidence that the values reported during testing truly represent the activity occurring within the insulation system.
Why Is Calibration Required?
Calibration is more than a recommended best practice; it’s a fundamental part of obtaining meaningful partial discharge measurements.
Proper calibration also establishes the scale factor for the measurement circuit, ensuring that the apparent charge displayed by the PD measuring system accurately reflects the known calibration pulse. Since the scale factor is influenced by the entire measurement setup – including the coupling device, measuring impedance, detector, test object, and connecting cables – any change to the measurement circuit can affect the calibration. For this reason, calibration should be repeated whenever components of the measurement circuit are modified or reconfigured.
Proper calibration helps ensure:
✔️Accurate measurement of apparent charge
✔️Repeatable results between test sessions
✔️Compliance with IEC 60270 requirements
✔️Confidence when comparing historical data
✔️Traceable measurements for quality assurance and accredited laboratories
Whether testing new equipment during manufacturing or evaluating aging assets in service, consistent calibration helps engineers make informed decisions based on reliable data.
Why IEC 60270 Matters
If you’ve worked with partial discharge testing, you’ve likely encountered IEC 60270. This internationally recognized standard establishes the procedures for measuring and calibrating partial discharge systems, helping ensure that measurements are accurate, repeatable, and consistent across different test environments.
Following IEC 60270 not only improves confidence in measurement results but also provides a common framework that allows manufacturers, utilities, and testing laboratories to evaluate insulation performance using standardized methods. For accredited laboratories and factory acceptance testing, compliance with the standard is an essential part of producing reliable, traceable results.
Choosing the Right PD Calibrator
Not every application requires the same level of functionality. Selecting the right PD calibrator depends on the type of equipment being tested, the complexity of the measurements, and the standards that must be met.
When evaluating a calibrator, consider:
❓Required apparent charge range
❓Compliance with applicable standards
❓Pulse generation capabilities
❓Ease of operation
❓Portability for laboratory or field use
❓Future testing requirements as your applications evolve
Investing in the right calibrator today can improve testing efficiency while protecting your laboratory’s capabilities for years to come.
Which PD Calibrator Is Right for Your Application?
Different testing environments require different calibration capabilities. HAEFELY’s family of PD calibrators offers solutions ranging from routine IEC 60270 calibration to advanced pulse generation for specialized testing applications.
KAL 9511 Basic PD Calibrator
The KAL 9511 is designed for laboratories and manufacturers performing routine IEC 60270 calibration. Its straightforward operation and reliable pulse generation make it an excellent choice for everyday calibration tasks where simplicity and accuracy are the primary requirements.
Best suited for:
➡️Routine IEC 60270 calibration
➡️Manufacturing quality control
➡️High-voltage testing laboratories
➡️Educational and research facilities
KAL 9510 Intermediate PD Calibrator
The KAL 9510 expands calibration capabilities with a modern touchscreen interface, rechargeable battery operation, selectable polarity, and a wide calibration range. Its intuitive operation and portability make it well suited for engineers who perform frequent calibrations across multiple test setups.
Best suited for:
➡️Daily laboratory use
➡️Factory acceptance testing
➡️Flexible laboratory environments
➡️Engineers requiring a portable, feature-rich calibrator
KAL 9520 Double Pulse PD Calibrator
For advanced testing applications, the KAL 9520 offers significantly expanded capabilities. Double pulse generation, synchronization options, adjustable phase shift, and an extended apparent charge range allow engineers to simulate more complex discharge conditions and verify sophisticated measurement systems.
Best suited for:
➡️Advanced research laboratories
➡️Specialized partial discharge investigations
➡️High-end manufacturing facilities
➡️Complex IEC 60270 measurement systems
KAL 9531 RIV Calibrator
The KAL 9531 is designed specifically for Radio Influence Voltage (RIV) calibration applications, supporting laboratories that perform RIV testing in accordance with applicable standards.
Best suited for:
➡️RIV testing
➡️High-voltage laboratories
➡️Utilities and equipment manufacturers requiring RIV measurements
Common Mistakes When Calibrating a PD Measurement System
Even experienced engineers can encounter issues that affect measurement accuracy. Some of the most common mistakes include:
❌Skipping calibration before testing
❌Using a calibrator with an insufficient charge range
❌Neglecting periodic verification of calibration equipment
❌Assuming all PD measurement systems respond identically
❌Overlooking changes made to the measurement setup between tests
Establishing a consistent calibration process helps improve repeatability and confidence in every measurement.
Supporting Accurate High-Voltage Testing
Reliable partial discharge measurements begin with reliable calibration. Selecting the appropriate PD calibrator helps ensure accurate measurements, repeatable results, and compliance with internationally recognized standards, providing engineers with greater confidence in every test they perform.
HV TECHNOLOGIES offers a complete range of HAEFELY PD calibrators, from routine IEC 60270 calibration instruments to advanced pulse generation systems for specialized applications. Whether you’re expanding a high-voltage laboratory, upgrading existing equipment, or implementing a new testing program, there’s a solution designed to support your specific measurement requirements.
Frequently Asked Questions
What is apparent charge?
Apparent charge is the value used to quantify the magnitude of a partial discharge event. Rather than measuring the actual charge inside the insulation defect, it represents the equivalent charge that would produce the same measurable effect at the terminals of the test object.
Why is IEC 60270 important?
IEC 60270 provides internationally recognized procedures for measuring and calibrating partial discharge systems, ensuring consistent and comparable results across laboratories and manufacturers.
How often should a PD measurement system be calibrated?
Calibration should be performed before conducting partial discharge measurements and whenever changes are made to the measurement setup. Periodic verification of the calibrator itself is also recommended to maintain traceability and confidence in test results.
What's the difference between a PD detector and a PD calibrator?
A PD detector measures partial discharge activity occurring within the test object. A PD calibrator injects known reference pulses into the measurement system to verify that the detector and associated equipment are accurately measuring apparent charge.
Which PD calibrator should I choose?
The right calibrator depends on your testing requirements. Routine IEC 60270 measurements may only require a basic calibrator, while advanced laboratories performing specialized diagnostics may benefit from additional capabilities such as double pulse generation, synchronization, or UHF pulse generation.
Why do I need to recalibrate if my measurement circuit changes?
A PD calibrator establishes the scale factor for the complete measurement circuit, not just the detector. Changes to components such as the coupling capacitor, measuring impedance, cabling, test object, or other parts of the measurement setup can alter the circuit’s response to partial discharge pulses. Recalibrating after these changes helps ensure that apparent charge measurements remain accurate, repeatable, and compliant with IEC 60270.