VJ Technologies Inspection Services Division. By Bob Maziuk, February 2015

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1 White Paper on the Inspection of Underground Electrical Conductors, Insulation, and Splices in Oil-Filled Piping Using High Energy Computed Tomography (CT) VJ Technologies Inspection Services Division By Bob Maziuk, February 2015 Introduction: The development of portable field solutions for high-energy X-ray generation, digital radiography now allows for the inspection of underground utilities and piping. A combination of portable high-energy X- ray generators, digital X-ray detection systems and highly specialized image processing algorithms, create expanded capabilities in X-ray imaging. With the combination of the system described above, VJ Technologies, VJ Inspection Services has been providing two-dimensional (2D) imaging services of underground high voltage conductors in oil filled piping for several years. With the advanced development of highly customized reconstruction algorithms and a specially configured, custom built gantry system, it is now possible to conduct threedimensional (3D) visualization and slice CT imaging of underground utility conductors and piping systems in-situ, providing a perspective view, which was previously only available after destructively cutting and sectioning a portion of the utility line in question. And, all of these utilities can be inspected while energized, in full operation, without shutting the utility down and creating a service outage. Yes, this new high-energy digital X-ray solution allows for inspection during operation which is allowing VJ Technologies customers to better analyze conditions of electrical conductors, insulation and splice joints under load, enabling them to make decisions and plan for their shutdown and repair as needed, in prevention of an uncontrolled outage, or worse, due to an otherwise potentially imminent failure. This White Paper will provide an explanation of using Computed Tomography (CT) in the inspection of underground utility feeder lines and how it can be employed in the field and how it is useful to the Utility companies that employ this technology and service. The Challenge: For years, 2D inspection of underground piping has been accomplished, first using X-ray film and an isotope gamma source, and then later using portable high-energy X-ray generators, digital X-ray detection systems and highly specialized image processing algorithms for near real-time results. The former method required exceptionally long exposure times and film processing which made it a very inefficient process. The advent of the portable high energy X-ray source coupled with digital detectors made the process far more effective and efficient, but the results were still only two dimensional.

2 With transmission X-ray, two dimensional data includes information that may not be visible due to the masking affect by materials that may lie in front of or behind in the direction of penetration, with respect to the area of interest. As such, important data with respect to the condition of a material can go undetected. This is where the value of computed tomography and volumetric visualization and slice data can be paramount. Volumetric reconstruction of a sample is possible when two-dimensional projection data is processed to produce the reconstructed volume of the sample. VJ Technologies (VJT) performed an application study using a custom designed Gantry scanner system on a sample section of an actual splice joint in order to prove the concept of using a gantry style Offset CT scanning system and the potential results it could deliver. The Application: Once the X-ray inspection system is in place, the next level of implementation is acquiring a series of 2D images of the sample through 360 of rotation around the sample or some portion thereof. These images, also called projections, are then processed using a proprietary algorithm, which converts the data set into a volumetric reconstruction of the sample. The volumetric data set can then be viewed as individual slice images at any point within the reconstructed volume. The data can also be viewed as a reconstructed three-dimensional (3D) volume. Examples of the projection data and the reconstructed volume data are included. The Setup: The initial design layout for this proof in concept consisted of a motorized rotating gantry setup, which held the X-ray generator and the detector, facilitating 360 of rotation around the sample. It was also designed to be mobile in that it could be rolled over the length of the pipe for full coverage from one end to another.

3 The Inspection: The images below represent the 2D X-ray images of the pipe and conductors, which are collected as the gantry rotates around the pipe through 360 of rotation.

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6 Once acquired, these 2D images are used to create the reconstructed volume of the pipe, using our proprietary reconstruction algorithms. The reconstructed volume can then be viewed using commercially available visualization software packages which display both the complete reconstructed volume as a 3D rendering or in planar slice views perpendicular to the length, width, and height of the splice pipe, which can be taken from any level within the volume. This image illustrates the main visualization screen of the volume viewing software. The volume visualization is shown in the lower right hand corner, while the other three windows show slice views from different perspectives. The upper left hand quadrant represents the Top slice view of the volume or the Axial view. When stepping through the slices of the volume in this window we are slicing through the length of the pipe. The other two windows represent the slice views from two opposing sides of the pipe. For example, one is slicing into the pipe volume through the 3:00 9:00 plane, while the other would be in the 12:00 6:00 plane.

7 Each of the quadrants can be maximized for optimum viewing. In the next several images, we will illustrate this feature using the individual windows to focus on a particular are of interest. In the image above, the view has been rotated, showing the oil at the bottom of the pipe displayed at the bottom of the image window for perspective. Also very noticeable in this image is the spider; the individual conductor segments as well as the separate strands that make up each segment. Lastly, the layers of insulation around the conductors are also very discernable, as well as the gaps within the layers of the insulation. Subsequent views on the pages that follow will focus on this area of interest at a higher level of magnification.

8 In the views below, slices though the side of the pipe show linear gaps in the insulation layers which correspond to the axial slice on the previous page.

9 In the image above, highlighted by the blue arrows are the gaps in the layers of insulation, which are more visible at this particular slice plane given the contrast curve selected. Also visible in the bottom of this image highlighted by the orange arrow is the oil level in the bottom of the pipe. Lastly, the layer of tape that goes around the entire OD of the spider is also visible and highlighted by the green arrow.

10 The image below is another rendering of the previous image without rotation applied, and with a slightly different contrast adjustment to bring out the detail of the outer layer of tape and the oil. Summary and Conclusions: VJ Inspection Services is able to offer volumetric field inspection services for underground as well as above ground and other heavy piping and electrical systems. The inspection process is fast and efficient and can even demonstrate movement in the systems being inspected. The inspection services can be offered on location during full system operation. The ability to inspect operating systems with very large, high density structures and product contents is creating new inspection solutions. Using the high-energy, digital X-ray inspection services is allowing operators to make better decisions for maintenance and to better plan for maintenance activities.