August 18, 2020
Sumitomo Electric Industries, Ltd.

World’s First Development of Remote Cable Monitoring System
Using Existing Underground Power Transmission Lines
Sumitomo Electric Industries, Ltd. (Head Office: Chuo-ku, Osaka; President:
Osamu Inoue; hereafter, “Sumitomo Electric”) and TEPCO Power Grid, Inc. (HeadOffice: Chiyoda-ku, Tokyo; President: Yoshinori Kaneko; hereafter, “TEPCO PG”)
have jointly developed a remote monitoring system that readily uses existingunderground power transmission lines to quickly build a sensor network for thefirst time in the world.
Power grid companies have power transmission line facilities installed in undergroundtunnels, pipelines and maintenance holes. These facilities are manually inspected andmaintained by workers who are painstakingly descending into underground tunnels andmaintenance holes, of which operating efficiency has been an issue. In the meantime,to secure stable supply, power grid companies are requested to install the latest
technologies using IoT and AI to quickly detect equipment failures and diagnose
facilities. However, building new communication infrastructure to operate and monitor
the relevant remote sensors would require substantial investment.
TEPCO PG and Sumitomo Electric have jointly developed and demonstrated a remotemonitoring system (Fig. 2) that can easily build a sensor network based on power line
communications (G3-PLC)*1 by using a metal layer, or a shielding layer, of an existingunderground power transmission line of 66 KV or more as a new data transmission line(Fig. 1). In this system, a small split CT*2 is attached to the bond wire*3 installed at theconnection in the middle and ends of the power transmission line, enabling power line
communication using the existing shielding layer as the data transmission line. By
using this system, the sensor data is transmitted to above ground and then to the cloudserver for data storage by using existing above ground communications means, suchas mobile line. The system can eliminate the need to lay a new data communicationline, building a highly reliable sensor network at low cost. Sumitomo Electric hasdeveloped the system that uses the shield layer of an underground power transmission

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line as a data transmission line, and it has been verified and adopted by TEPCO PG
since July this year to monitor the equipment temperature in the underground tunnels
operated by the company.
Currently, the two companies are developing a system that can acquire information*4 inmaintenance hole facilities (Fig. 3), which has been difficult to acquire, aiming forpractical use in 2021. Sumitomo Electric will continue advancing the sophistication ofpower line maintenance and contribute to solving the problems of labor shortages andstable power supply by developing a system that adopts Digital transformation using AI
and IoT based on sensor data.
*1 This was achieved by utilizing the low frequency (about 150 to 400 kHz) used forsmart meter data transmission.
*2 CT: Current transformer. Inductive coupling method that induces signals in theshielding layer without contact.
*3 Single line to the shielding layer to connect to the ground and the adjacent section

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*4 Temperature, electric current, water level, images, etc. in maintenance holes

Figure 1.Overview of the shielding layer transmission
Figure 3.
Overview of the remote monitoring systemfor cable and maintenance hole facilities

Figure 2.Overview of the temperature monitoring system for cable tunnels■ ReferenceSumitomo Electric's Website
https://sumitomoelectric.com/

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