Railway traction power infrastructure must remain reliable under continuous operation, restricted maintenance windows and demanding environmental conditions.
Insulation deterioration, contaminated surfaces, loose connections and ageing cable accessories can generate partial discharge long before visible damage, severe overheating or an operational failure occurs. Detecting and locating these early signals can help railway maintenance teams prioritise further testing and corrective work.
For railway systems operating at 15 kV, 16.7 Hz AC, however, partial discharge assessment presents an additional technical challenge.
Most industrial electrical inspection instruments are designed around 50 Hz or 60 Hz power networks. When a railway asset operating at 16.7 Hz is analysed using the wrong power-cycle reference, the resulting phase-resolved partial discharge pattern may not accurately represent the relationship between the detected pulses and the traction voltage cycle.
HERTZINNO developed a dedicated railway inspection capability combining non-contact acoustic localisation, ultrasonic partial discharge detection and native 16.7 Hz PRPD analysis.
The solution has been applied within a German railway environment to support the inspection of energised traction power assets.
To protect customer confidentiality, the railway organisation, site location, line information, equipment numbers and detailed operational data are not disclosed.
Germany’s national railway traction power network supplies electric traction vehicles using power at a frequency of 16.7 Hz. The European railway energy framework also recognises 15 kV, 16.7 Hz AC as one of the standard electrification systems used within the European rail network.
Phase-resolved partial discharge analysis, commonly known as PRPD, maps discharge pulses according to their position within the applied voltage cycle.
The phase distribution of these pulses can support the assessment of phenomena such as:
The selected power frequency determines how the measurement system constructs this cycle.
Using a 50 Hz or 60 Hz reference for equipment operating at 16.7 Hz can place detected pulses at incorrect phase positions. This may distort the pattern and reduce its value for defect recognition and engineering review.
HERTZINNO’s railway mode uses the actual 16.7 Hz traction power cycle as the PRPD phase reference. The same inspection platform can also be configured for 50 Hz and 60 Hz electrical systems.
The German railway application involved electrical infrastructure operating in a complex environment with multiple potential sources of acoustic interference.
Typical challenges included:
Traditional single-point ultrasonic instruments can identify the presence of an abnormal signal, but the operator may still need to move the sensor around individual components to determine its origin.
This process can be time-consuming where several insulators, cable terminations, switches or connections are located within the same inspection area.
The railway organisation required a method that could scan a wider field of view, locate the suspected emission source and preserve visual evidence for later assessment.
A HERTZINNO handheld inspection system was used to survey railway traction power equipment from an approved safe position.
The system captures signals through a multi-microphone array and calculates the direction of acoustic and ultrasonic energy. The suspected source is then displayed directly over the visible image of the inspected asset.
Instead of relying only on a numerical reading or audible signal, the maintenance engineer can see which component is associated with the detected ultrasonic activity.
When a suspected source is found, the operator can refine the inspection by adjusting:
For the German railway application, the PRPD power-cycle setting was configured to 16.7 Hz.
Detected pulses could therefore be mapped against the appropriate traction power phase rather than a conventional industrial 50 Hz reference.
The inspection method is suitable for a broad range of railway electrification assets.
Potential inspection targets include:
Acoustic source localisation can help identify which connection or component is producing an abnormal ultrasonic signal.
Cable terminations and joints can be affected by installation defects, contamination, ageing and electrical stress.
A non-contact acoustic survey can support routine screening and help determine where more detailed electrical testing may be required.
Pollution, moisture, ageing and surface damage may contribute to discharge activity around railway insulators and high-voltage accessories.
Where access conditions permit, the system can support remote inspection of selected overhead line components, feeders, switches and electrical connections.
The same workflow can be applied to electrical cabinets, auxiliary power equipment and other trackside installations that may produce detectable acoustic or ultrasonic fault signatures.
Each inspection can produce a structured digital record containing:
The data can be reviewed offline using HERTZINNO Insight Studio, allowing inspection teams to organise asset records, compare historical measurements and generate standardised reports.
Repeated inspections can help determine whether a signal remains stable, increases over time or changes according to operating and environmental conditions.
The method supports condition assessment from a safe distance without direct contact with the energised component.
It does not replace mandatory electrical tests or railway safety procedures, but it can provide an efficient first-line screening tool.
A visual acoustic map helps the operator identify the likely origin of a signal without manually checking every individual point.
Native 16.7 Hz support enables PRPD analysis based on the actual traction power cycle used by the inspected equipment.
Visual localisation and recorded parameters improve inspection consistency and make the result easier to review across different teams.
Documented inspection results can help maintenance organisations prioritise additional testing, cleaning, repair or replacement according to asset condition.
The same platform may also support:
Based on HERTZINNO’s current market review, its inspection platform is the only known acoustic imaging solution providing native 16.7 Hz PRPD support specifically for railway traction power applications.
This capability is relevant not only to railway operators in Germany, but also to infrastructure managers, electrification contractors and maintenance organisations working with 15 kV, 16.7 Hz railway systems elsewhere in Europe.
The application demonstrates how acoustic localisation and frequency-correct PRPD analysis can be integrated into a practical railway condition-monitoring workflow.
Railway networks differ in traction voltage, power frequency, asset design, operating environment and inspection procedures.
HERTZINNO works with:
Contact HERTZINNO to discuss 16.7 Hz partial discharge inspection, traction substation surveys, overhead line equipment assessment or railway acoustic condition monitoring.
Detect weak fault signals before they become operational disruptions.
Contact HERTZINNO for a technical consultation or railway application demonstration.
