Partial Discharge Monitoring

The Challenge: From factory to field

The quantity and strength of Partial Discharges (PD) are considered a critical indicator of the performance of a power transformer’s insulation. During manufacture, a power transformer is required to undergo a mandatory factory acceptance test to assess the quality of the insulation to ensuring the transformer will operate efficiently in the field.

What's the challenge? It gets 'noisy' in the field.

These tests are performed within a controlled environment which minimises the impact of external influences. When a transformer is operational in the field it is open to many variable external factors, including high amounts of noise, that can overlap to the PD spectrum.

What do asset managers need?

This is the challenge for continuous online partial discharge monitoring systems, how to see through the noise and detect only the relevant Partial Discharge signals.

Camlin Energy – A new way of thinking?

At Camlin Energy we have the solution! The TOTUS transformer monitor comes with a patented, fully automated noise rejection system which has been proven in the field for over a decade and accurately monitored partial discharge on hundreds of active transformers.

The combination of the de-noising capability combined with a user-friendly interface, means the TOTUS is not only reliable but intuitive for all users. We remove the need for expert data review, minimising false alarms and supporting easy identification of the intensity and location of existing partial discharge.

What happens if Partial Discharge goes undetected?

Partial Discharges typically begin at a low intensity and do not have significant impact upon the transformer. However if left undetected the PD can begin to grow in intensity resulting in the continued degradation of the transformer insulation. This can lead to 'arcing' in the transformer, which has the potential to cause catastrophic failure including fire, tank rupture and potentially explosion.

What is Partial Discharge and what impact does it have on a transformer?

Partial discharge is an electrical discharge that occurs across a localized area within the insulation of your power transformer. PD can occur due to a range of factors, such as imperfections in the insulation, mechanical stresses, or aging of the insulation.

Although partial discharge is localised in a small portion of the insulation, continued PD events can lead to the degradation of the insulation material and eventually a complete dielectric breakdown, resulting in transformer failure.

The time to failure is dependent upon many factors such as voltage, insulation material, load, vibrations and temperature.

Furthermore, it is important to note that partial discharge can also occur inside the bushings and can rapidly result in failures, particularly in Resin Impregnated Paper (RIP) bushings.

A failure in a bushing has the potential to result in transformer failure in up to 30% of cases.

It is therefore crucial to:

• Continuously monitor the PD activity in normal operating conditions
• Correlate the PD data with key diagnostic parameters
• Automatically identify the phase affected by PD
• Automatically identify if the PD source is in the bushing or in the windings
• Easily assess and interpret the PD criticality

The two main challenges that exist to partial discharge monitoring:

1. Which method of measurement is most effective?
   To measure PD there are three key methods of measurement all with their own benefits and limitations as shown in the illustration. With years of industry experience Camlin Energy have determined that the electrical method is the best and most reliable method to measure and accurately detect partial discharge events in a transformer, including bushings.
2. How can we navigate around the negative aspects of the electrical method?
   Camlin’s patented algorithm removes the noise, disturbances and cross-coupling signals emitted from the other phases. This is achieved thanks to simultaneous and continuous acquisitions in all the phases using a Ultra-Wide Bandwidth combined with powerful algorithms, which compare the PD waveforms in real time in time, power and frequency domain. Using our specialised software we can locate the phase and winding of the partial discharge events and present the information with our easy to interpret visualisation tool, the PD Triangle.