Jeffry P. Mackevich

Polymer outdoor insulating materials. Part I: Comparison of porcelain and polymer electrical insulation

It is the objective of this series of articles, beginning in this issue, to review for users the benefits of polymer insulating materials. Material science, design, and processing conditions all influence performance and must be considered. Using silicone as an example, we will discuss performance considerations and present data on performance counter to common industry perceptions. The series goal is to acquaint the user with relevant topics so that more informed decisions can be made in the evaluation, selection, and use of outdoor polymer material insulation. In Part I, a comparison of porcelain and polymer properties is presented, including the relative advantages of each.

Polymer outdoor insulating materials. Part III-Silicone elastomer considerations

The silicone-based formulations now in use by Raychem have been specially developed for electrical insulating applications. They have undergone many years of development and optimization to yield exceptional electrical and weathering performance properties, comparable to the polyolefin copolymer materials. The intent of this article is to highlight the advantages of properly formulated silicone materials in outdoor insulating applications.

Polymer outdoor insulating materials. II. Material considerations

The following article is Part II of a three-part series on the use of polymer insulating materials in outdoor insulation applications. Despite three decades of service history, polymer insulation materials do not have the same level of standardization as porcelain. As with any technology that is not well standardized, misunderstanding and confusion result, which can influence user selection and application. The objective of this series is to review the benefits of polymer insulating materials. Part II discusses the factors that affect the engineering of materials and addresses the validity of some industry perceptions. A future article will explore some of the material science aspects of silicone elastomer materials by using the case of a hybrid insulator design.

Insulation enhancement with heat-shrinkable components. III. Shielded power cable

For pt.II see ibid., vol.7, no.3, p.16 (1991). Heat-shrinkable accessories for shielded power cable, including details of the necessary components for reliable terminations and joints, are described. The key functions of terminations are outlined, and the requirements for stress control, external leakage insulation, and environmental sealing and how they are met and examined. A similar discussion for joints focuses on control of the electric field, connector insulation and restoration of the shield, environmental sealing, and oil-barrier components. Applications of the joints and terminations, performance requirements and standards, and cable accessory enhancements are discussed.<<ETX>>

Current Limiting Protector for Industrial Applications

The development, the testing, and the application of the current limiting protector (CLP) and a compatible current level sensing and trigger circuit are described. The CLP consists of a current carrying main conductor and a parallel fusible element. In response to a short circuit, gaps are formed in the main current path by pyrotechnic cutting. The gap arc voltages commutate the current to the parallel fusible element, which then interrupts the current in a current limiting mode. High-power tests in 4-15-kV circuits limited prospective short circuits of 40-kA (rms) to less than 15 kA. The CLP offers single shot current limiting protection with low let-through I2t.

Trends in underground residential distribution cable systems

Some observed trends in underground residential distribution cable designs being installed are discussed. Three major changes needed in cable design to improve service reliability are explored: (1) different insulation materials; (2) greater insulation thickness; and (3) use of a jacketed cable. Another change in design which is gaining in popularity, the use of solid or filled strand conductor, is also discussed. Cable accessory performance is reviewed, and standards for terminations and separable connectors are examined. Accessory application issues for various cable designs are discussed.<<ETX>>

Evaluation of polymer-housed distribution arresters for use on rural electric power systems

Users have converted to polymer-housed distribution surge arresters because of concerns over violent porcelain arrester failure. There is a false perception in the industry that polymer arresters are intrinsically fail-safe. It is proposed that there is a lack of understanding of the differences in failure mechanisms between porcelain and polymer arresters. Polymer arresters have unique design requirements to provide the desired reliability improvements. This paper suggests criteria for rural electric power system user evaluation of polymer arrester design and performance. Users are encouraged to participate in the standards writing process to facilitate changes beneficial to the industry. >

The Impact of IEEE Standard 404 Revisions on Industrial Cable Distribution Systems

Prior to the 1986 revision of IEEE Standard 404, the design proof testing for extruded solid dielectric cables specified in AEIC Standard CS5-82 required testing and test levels that went beyond the scope of IEEE Standards 404 and 48, the joint and termination standards, respectively. As a result, it is perceived that cable accessory performance can be inferior to that of the cable. IEEE 404-1986 is a major step towards matching joint design proof testing with that specified for cable. The effects of the revised standard on cable joint performance and design, expected future industry activities on coordinating cable and accessory standards for consistent performance levels, and the benefits to industrial cable distribution systems are discussed.