Economical and practicable condition assessment of MV- and LV-distribution grids

Abstract

This paper describes a procedure of condition assessment for distribution grids which is applicable in an economical, non-intrusive and practical way. The assessment procedure is based on periodic visual inspections. It is additionally supplemented by suitable and simple measurement methods which can be used without any disconnection of the components and thus without much additional effort during an inspection. Therefore suitable non-intrusive measurement methods for medium voltage substations and switchgears as well as low voltage distribution cabinets will be presented in relation to an integrated condition assessment of distribution grids. But significance of these non-intrusive measurement methods is limited. Using the example of acoustic partial discharge detection measurement uncertainties will be determined by intensive laboratory tests and numerous field tests realized with several German distribution system operators. These values will be combined with condition information of visual inspections by using theory of evidence to express the uncertainty. Since measurements and visual inspections detect different kinds of deficiencies of electrical equipment, a combination of both is crucial to achieve a high significance of condition assessment as shown in this paper.

Dynamic Inspection Interval Determination for Efficient Distribution Grid Asset-Management

“…In refs. [4,5], Beerboom and Johae discuss techniques how to use uncertainty theory to describe the uncertainty about the assets' conditions. That approach might allow assessing how visits and inspection affect the uncertainty of assets' conditions and how the process can be optimized.…”

“…In the context of distribution substation inspection, diverse papers get published that focus on how inspections can be improved, for example by increasing their objectivity [3] or by measuring and reducing their uncertainty [4,5]. However, mostly constant inspection intervals in the range of 1-4 years are assumed [5]. Lacroix et al [6] present a decision management platform for asset-management considering inspection intervals of five or even ten years.…”

“…All adjustments in the process must be made under the objective of high usability for the workers (R4). Especially a minimal time expenditure for the data acquisition is aspired, not only because of usability, but also to ensure that additional costs and working hours do not surpass the cost savings (R5) [5]. That is particularly important in the distribution grids where a high total number of inspections are performed, single assets have only low value, and relatively low follow-up costs arise in the case of an outage.…”

HIL testing and future-proofing of UFLS schemes

“…Statistical analysis of past failures helps to identify weaknesses and find appropriate diagnostic methods for a reliable condition assessment, as shown in the case study in Chapter 5.5. The approach to condition assessment can thus be divided into two different perspectives: replacement -long-term perspective -and maintenance -short-term perspective [34]. The condition assessment should take these different perspectives into account.…”

Performance Comparison of PD Data Acquisition Techniques for Condition Monitoring of Medium Voltage Cables

“…Already installed cables are aging and reaching the end of their lifetime [1]. Furthermore, due to loading conditions these cables are often operating at their capacity limits [2], which can be even worse due to increasing penetration of the power electronic loads and sources, e.g., related to distributed energy resources. On the one hand, the operational circumstances of the cable networks are causing challenges.…”