Measurement and monitoring of overhead transmission line sag in smart grid: A review

Abstract

In a transmission line, sag is intentionally provided to relax the tension on the wire when placed between two terminals. However, thermal stress and extreme weather conditions can cause increases in transmission line sag, which can eventually damage transmission line infrastructure. In this regard, this paper examines a number of sag measurement techniques based on physical or optical properties and integrated with signal processing and communication technologies. The performance of different sag measurement methods is compared in terms of accuracy, precision and key feature. Several challenges and limitations of the existing sag measurement mechanisms are reported. A number of recommendations to address the identified challenges are made. Moreover, an efficient communication framework for sag related information exchange is proposed. This comprehensive review of the sag measurement techniques will facilitate the evolution of new and efficient real-time sag measurement and monitoring methods.

A survey of sag monitoring methods for power grid transmission lines

“…Finally, for a review of some widely used sag calculation and sag prediction methods in the literature, one can refer to [139] - [142]. Note that, although [139] also provides an overview of overhead line sag monitoring methods, there is significant difference between our work and [139]. Firstly, our coverage is much wider.…”

“…Even for the GPS method that received great attention in [139], only six works were discussed there while our work has covered ten works (references [37] - [46]). Thirdly, in addition to these coverage and discussion, our work has also offered detailed comparison of different methods in terms of hardware, software and quantitative accuracy in Tables 1-3, which are missing in [139]. These tables will allow power system designers to easily identify which methods can fit their purposes.…”

“…For example, the sag prediction method was largely ignored in [139], while this method is important for timely planning of the power network and hence, it has been discussed in detail here. Also, the graphical method and the hybrid method in sag‐tension calculation were not discussed in [139], while they play crucial roles in the overhead line installation practice and have been discussed here. Secondly, our discussion is much deeper.…”

“…Secondly, our discussion is much deeper. For example, in the direct methods, this work has investigated 26 works that use different aerial or terrestrial systems to measure the sag directly (references [9] ‐ [34]), while [139] only discussed five of them briefly. Even for the GPS method that received great attention in [139], only six works were discussed there while our work has covered ten works (references [37] ‐ [46]).…”

“…For example, in the direct methods, this work has investigated 26 works that use different aerial or terrestrial systems to measure the sag directly (references [9] ‐ [34]), while [139] only discussed five of them briefly. Even for the GPS method that received great attention in [139], only six works were discussed there while our work has covered ten works (references [37] ‐ [46]). Thirdly, in addition to these coverage and discussion, our work has also offered detailed comparison of different methods in terms of hardware, software and quantitative accuracy in Tables 1–3, which are missing in [139].…”