Line Splice Sensing

Risk Reduction Category

Technology Description

Line splices are ubiquitous, and while generally robust, sometimes, these splices may not have been constructed optimally such that the splice is weakened and/or may have greater impedance than specification. Thus, it may fail due to mechanical stress or the result of excess heating. One source indicated that many splice failures occur due to poor workmanship and/or due to corrosion after improperly applying a corrosion inhibitor. Should the splice physically fail, the broken conductor ends may fall upon dry, combustible vegetation and ignite a fire.

Inspection of electrical lines should occur with some regularity to identify weakened or overheated splices. A few tools that are commonly used today are described briefly:

A micro-ohmmeter mounted to a hotstick can measure resistance across a splice while energized and inservice. [2]. Elevated resistance may indicate a failing splice.
Infrared (IR) sensing may be used to detect heating of the splice. However, due to the reflective metallic surface (low emissivity) of many splices, infrared measurements can yield inaccurate results and therefore elevated surface temperatures may only be confirmed when the splice is close to failure.
Thermal imaging cameras may be used to identify hotspots on the power line, on splices, or on other power line equipment, but are subject to the same emissivity concerns as infrared spot sensing.
One company markets a device to mitigate faulty splices called the ClampStar, an electrical/mechanical shunt, that serves to brace and effectively bypass the weakened splice with no interruption of power as shown below [4].

Oak Ridge National Lab (ORNL) has developed an innovative sensor system using “smart” patches affixed to the exterior of a compression connector. The motivation for this development is to provide information about the structural integrity of the connector, where current inspection methods only warn of electrical impedance that is out of specification. In the ORNL work, a piezoelectric ceramic material (PZT) is integrated with the splice. This smart patch produces an electrical signal, that when processed, corresponds to a damage index. Laboratory tests included tensile strength and thermal cycling perturbations on the joint. The electrical signature is sensitive to variations in structural conditions so that utilities can correlate this analysis to the structural health of a connector, providing potential application in routine structural health monitoring. [5].

Technical Readiness (Commercial Availability)

The smart patch is a research and development effort by Oak Ridge National Laboratory. To the author’s knowledge, there has been no commercialization. This technology is subject to a US patent: J.-A. Wang, F. Ren, “Systems, methods and patches for monitoring a structural health of a connector in overhead transmission lines”, U.S. Patent, US 10,641,840 B2, May 5, 2020. [6].

Regarding tools that are commonly used by utilities today, the following list of manufacturers is the product of an Internet search using a general description of the technology as the search term. Sometimes more than one variation on the search term is used. The objective is to identify the most demonstration-ready products available in the category. Toward assessing demonstration readiness, the manufacturer websites typically provide useful information such as writeups of successful use cases or field demonstrations, number of deployments, or other indicators. Where lack of information exists online, further inquiry is made by phone. Generally, one to three frontrunners emerge as being most ready for a field demonstration. Preference is given to manufacturers who sell to the United States, or, if emerging technology, those who have participated in US-based field demonstrations.

Sensorlink – Ohmstik Plus

https://sensorlink.com/products/ohmstik

Teledyne FLIR (thermal imaging)

https://www.flir.com/instruments/utilities/electric-power-distribution/

HIKMICRO

https://www.hikmicrotech.com/en_us/

Fluke

https://www.fluke.com/en-us/products/thermal-cameras/product-selector