Lord Consulting

The authors present a paper detailing some recent on-line partial discharge (PD) testing and software data analysis work carried out to develop a suitable and robust method for on-line PD spot testing and monitoring of in-service, energised high voltage outdoor cable sealing ends. The work was carried out in follow-up to several failures of 132kV and 220kV HV cable sealing ends at electricity transmission utilities in Europe. One of the main challenges encountered when testing HV cable sealing ends is to differentiate between the highly dangerous internal PD activity within the sealing ends from the large number of external, high frequency impulsive interferences originating from other nearby items of plant. Sources of such interference include corona and discharges on the surfaces of ceramic insulators related to atmospheric pollution and weather. New techniques have been developed that involve synchronously capturing data from four sensors and comparing the signals in order to identify internal PD activity in the sealing end. The system can be used as a tool for commissioning new cable sealing ends and also assessing the insulation condition of aged ones.

Presented at the EPRI Substation Equipment Diagnostics Conference XV
March 2-6, 2008

A new technology developed for remote imaging and quantification of gases has been developed using state-of-the-art diffractive optics and image processing algorithms. This technology was developed and patented by Pacific Advanced Technology for the US Defense Department1. The technology has been applied to remote gas leak imaging and quantification for the oil, gas, chemical and power industries. Gas Imaging Technology, LLC (GIT) has been granted the world wide exclusive license to market the Sherlock® for this purpose. This paper describes the Sherlock® imaging spectrometer, theory of operations, and applications in the power industry to find sulfurhexafluoride (SF6) gas leaks from circuit breakers and gas insulated switch gear (GIS).

Testing And Leak Imaging/Quantification Technology

Whilst the power industry internationally is heavily dependent on the use of SF6 gas for its unsurpassed insulation and arcquenching properties, the stewardship of the SF6 gas in the GIE equipment itself is in need of an urgent review.
There are two drivers for this. The fi rst is that the Industry is now facing aging GIE equipment and is also now more aware of the signifi cant roll that moisture in the gas can play in reducing GIE equipment life and reliability. Improved, formalised, and more regular SF6 testing regimes are now called for to ensure optimum outcomes from this equipment.
The second reason is that, with SF6 being one of the leading greenhouse gases, the Industry as been effectively put on notice by powerful environmental regulators to self regulate its environmental stewardship of SF6 by implementing guidelines being completed presently by the Cigre organisation for the handling of SF6. With Australasia now Kyoto Protocol signatories, this matter will be a prominent issue in 2008, a far cry from the attitudes of earlier years to SF6 gas handling.
This paper reviews the issues and properties of SF6, the environmental drivers and guidelines in place, and the technologies on hand to manage and implement an enhanced SF6 stewardship to a new level of overall best practice.

A series of mini papers

THE DEVELOPMENT OF A ROBUST ON-LINE PARTIAL-DISCHARGE (PD) MONITORING TECHNIQUE HAS PROMPTED EDF ENERGY to perform routine on-line mapping tests on its underground medium-voltage (MV) cable network. EDF Energy is concurrently reviewing its long-term preventive-maintenance strategy, taking advantage of the increased functionality.

The On-Line Partial Discharge (PD) testing of Medium Voltage cables (6.6kV to 36kV)
and High Voltage Cables (66kV to 400kV) originated in the UK in the late 1990’s through
the use of split-core High Frequency Current Transformer (HFCT) and TEV sensors
which are attached around the earth strap or cable core of the cable at the switchgear/
transformer with the equipment ‘live’.

The authors present a paper detailing new techniques for on-line partial discharge (PD) testing of in-service, solidinsulated, medium and high voltage plant located in outdoor environments. Detection of electromagnetic radiation is a well known and documented method for location of PD signals. However interference signals from RF sources, corona and surface discharges can be a major problem when testing outdoors, obstructing the observation of internal PD and confusing measurements. Experience in these situations has led to the development of various new tools and test techniques for PD identification and discrimination of interfering signals and background noise. Shielding sensors have been employed with a multi-channel measurement system to assist in detecting signals that are external to the equipment under test with time-of-flight (TOF) analysis. Methods for automating the test procedure and data analysis have also been a key part in this research and will be fundamental to future developments.