Upgrading and automating aging electrical assets is an ongoing project for utilities. Finding cost-effective solutions that meet the unique needs of an underground secondary network can be challenging and time-consuming. Low voltage cables are heavily meshed in multiple manholes, and network transformers are often installed in underground vaults that are difficult to access.
London Hydro is taking a unique approach to increase visibility and gain remote control of its secondary network located in London’s downtown core. Two different solutions were implemented to establish communications between 57 transformer vault locations and its Supervisory Control and Data Acquisition (SCADA) system.
Previously, London Hydro relied on manual procedures for troubleshooting issues on its underground grid. This often required field staff to be positioned in the vaults to communicate any issues back to the control room over radio. This process took a considerable amount of time and presented safety hazards that could be avoided with updated and innovative technology.
The two solutions London Hydro is leveraging support the unique operational needs of their downtown grid, while offering insights for asset management and systems engineering. The key difference between these two solutions is the communications medium. One uses optical fibre cable, and the other uses power-line carrier (PLC) technology on London Hydro’s existing underground distribution cables.
Optical Fibre Cable
London Hydro recently deployed new network equipment along a main artery of the downtown core. New construction presented the opportunity to include duct structure for the installation of an optical fibre backbone to its SCADA system. London Hydro elected to use a vault monitoring system from Eaton, with the newly installed optical fibre acting as the communications medium.
London Hydro worked with Eaton to customize a vault monitoring solution built around their Transformer Ruggedized Telemetry Link (TRTL). New transformer vaults were equipped with a TRTL responsible for collecting sensor data, such as vault liquid level, ambient temperature and transformer oil temperature. It also interfaces directly with Eaton’s Network Protection Relay to enable remote monitoring and control of the network protector.
The fibre backbone has been connected in 12 vaults adjacent to the main artery of downtown. To date, four locations have been fitted with the vault monitoring system, with the remaining eight locations being scheduled for completion by the end of 2021.
Power-Line Carrier (PLC)
The remaining 45 network transformers supply two vast networks of low voltage cable, which occupy the north and south extremities of the downtown core. The dense urban landscape and geographically dispersed network rendered traditional communications either unfeasible or cost-prohibitive.
London Hydro is currently piloting a solution provided by DigitalGrid Inc., whose network protection relay supports two-way communications over London Hydro’s existing distribution cables using power-line carrier technology. The relay couples a signal containing sensor data into the medium voltage cable. The signal gets decoupled at the substation, where it connects to London Hydro’s SCADA system.
If there is a fault on one of the medium voltage cables, the relay can take advantage of London Hydro’s highly redundant secondary network to transmit the data through a transformer connected to an un-faulted medium voltage cable. This highly redundant system mitigates the loss of London Hydro’s situational awareness during network events.
Like Eaton’s system, DigitalGrid’s platform offered remote control of the network protector relay, as well as sensors to monitor vault conditions. The pilot installation is fully commissioned at four locations and will be assessed by London Hydro over the next six months.
“Our team is always looking for ways to improve safety and take a proactive approach to system reliability,” says Jac Vanderbaan, Director of Engineering. “This hybrid approach to vault visibility and remote network transformer control allows us to design a communications system that supports our employees and elaborate downtown network.”
London Hydro will use the real-time visibility into its grid to assess the condition of its assets and troubleshoot remotely, which is critical for supplying reliable power. In the future, London Hydro will use the data to make better decisions for system planning.
London Hydro Inc. delivers safe and reliable electricity to over 160,000 customers. We are committed to being a trusted energy source provider through innovation, customer focus and operational excellence. @LondonHydro