Partial Discharge In Live Cables - Reducing HV Failures By Improved Monitoring (A UK DNO Case Study)

By Chris Dodds on 31st March, 2015

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Partial Discharge In Live Cables - Reducing HV Failures By Improved Monitoring (A UK DNO Case Study)

T&D present a new Guest Blog from EA Technology today focussing on a UK DNO case study on reducing high volage (HV) power failures by improved monitoring using EA's CableData Collector (CDC). 

The CDC identifies and reports Partial Discharge (PD) activity in live cables at distribution voltages.

EA Technology

What are the issues/problems that lead to the development of the CableData Collector™?

There is a growing concern about the increasing age and reliability of Medium and High Voltage (MV/HV) distribution networks, together with considerable pressure to implement the most cost-effective management of network assets.

Therefore asset managers around the world have a very real need to understand the condition of their ageing Medium and High Voltage (MV/HV) cable assets, to help with their management and ultimately improve network reliability.

Pictured: EA Technology's Cable Data Collector

EA Technology's Cable Data Collector

The strategy of moving toward maintaining and replacing assets only when strictly necessary (Condition Based Maintenance) can help considerably in meeting these needs.

Implemented correctly, this approach can deliver significant cost savings, whilst keeping reliability and quality at the required level for electrical assets. To do this, asset managers need accurate information at their fingertips in order to make informed decisions.

Why is this a problem if it isn’t managed?

PD is the primary cause of failures in cables, however, replacing and maintaining underground cable circuits, particularly with the need for excavation, can be very expensive, hence network managers need evidence to justify maintenance/replacement actions.

Having information regarding the presence, severity and location of PD helps to make smarter informed decisions when planning and conducting repairs. Knowing the location of PD activity can also reduce the cost of repair through more accurate excavation limited to the area of interest.

Further Reading : Video Tutorial Masterclass - PD Partial Discharge & Electrical Cable Breakdown

EA Technology's Cable Data Collector

What is the CableData Collector™ and how can it help solve the issues/problems?

EA Technology have developed a non-intrusive, on-line cable PD testing system called the CableData Collector™. This solution introduces a simple-to-use, effective tool for the quick assessment of large numbers of cables.

The CableData Collector™ enables a total view of the condition of the distribution cable network through the collection of accurate cable PD data without the need for deployment of expert engineers, expensive off-line test equipment and the need to plan and conduct an outage on cable circuits to be tested.

EA Technology are the world leaders in PD measurement. The knowledge that EA Technology possess around PD has been developed through their vast experiences from PD surveys and via the Partial Discharge User Group (PDUG), a panel of experts from each of the UK Distribution Network Operators (DNOs) who meet quarterly at EA Technology to discuss PD problems, detection methods and future instrumentation designs / requirements. 

Private Network Owners,Operators and Electrical Engineers now have the opportunity to join a similar event, the new Partial Discharge Forum.

EA Technology Partial Discharge

Video: EA Technology CableData Collector

Read these Case Studies and see the substantial financial savings our customers are making from use of the CableData Collector.

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Questions & Answers....

Q1 How do you distinguish between PD on the target cable and all other equipment connected that may also produce PD. Eg: overhead systems, switchgear, pole top switches etc....?

A1 I will assume you are referring to on line PD measurement and location using the CableData Collector? The signal travels down the earth screen, whenever it meets a change of impedance, there will be a point of reflection. The bigger the change of impedance, the bigger the reflection. At the cable termination the cable’s screen tends to be earthed or left open circuit. Either way this a massive change of impedance therefore, the signals generated on the cable tend to be confined to the cable. Signals generated outside of the cable tend to be severely attenuated by the same point of reflection. This is for signals generated on the earth screen. 

PD or noise signals also travel on the conductor. Again they tend to be attenuated by the changes of impedance but it certainly would not be usual to have the conductor open circuit or even less likely that it would be earthed. Therefore, it is not impossible for conducted PD from sources other than the cable or noise signals to appear. In practice noise is a much bigger problem than non-cable PD sources which is why the CDC has an advanced filter and phase plots to help separate between true PD and noise. With the right signal to noise ratio, it is possible to locate as well as measure using the CDC. This then will confirm whether you are looking at cable PD or an external source. If there is any doubt then connected assets should be either be disconnected or surveyed for PD activity themselves with TEV, Ultrasound and/or UHF technology as appropriate. 


Partial Discharge In Live Cables - Reducing HV Failures By Improved Monitoring (A UK DNO Case Study)

Category:  Electrical Equipment HV

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