Remote communication for pole top reclosers and switches
Viola’s solution for remotely operating pole-top reclosers and switches increases reliability, cuts operating costs and helps to meet and exceed regulatory performance targets.
Communication to Pole-tops Emerges as a Key Challenge
ESB Networks has a large number of field devices that are dispersed around the country, and due to the partly challenging environment it could take maintenance crews sometimes up to two hours to reach a fault destination. Fault location and manual maintenance was thus proving very costly, and ESB identified that the pole‐top devices used to sectionalize the network would need to be put under central control. It was thus decided to equip these pole‐top reclosers and switches with a solution that would allow for them to be monitored and operated automatically from the SCADA control centers in Dublin and Cork. Reclosers and switches also play a central role in network downtime. Meeting the regulator's performance targets on downtime has significant financial reverberations. Falling short of the target will have the network operator penalized, whereas exceeding the target will earn the company a bonus. The sums involved are in the magnitude of hundreds of thousands of euros annually. Moreover, in terms of customer service, it is vital to get electricity restored to customers as fast as possible after a blackout.
Overcoming the Communications Gap
As Frank Browning, SCADA specialist at ESB Networks' Dublin Control Center puts it: “The main technical challenge was how to talk to the pole‐tops.” At first, ESB tried to piggyback on top of the radio system that was being used for substation communication. The idea was, however, soon scrapped because many recloser sites were in areas where radio coverage was poor and the low signal disrupted the communication. It also became evident that the radio system did not have enough capacity for the number of devices envisaged. ESB Networks then sought help from another group subsidiary, ESB Telecoms. Under the supervision of Anthony Gray, Telecommunications Specialist from Telecoms Planning, the team eventually came to the conclusion that only two feasible options existed: GSM or GPRS. As a proprietary system was out of the picture the only way to get universal coverage was using a public carrier network.
The GSM testing was definitely an improvement over radio modems, but required regular polling of the field devices. As the number of devices grew, SCADA operators started to become frustrated as they had to initiate the call to each device separately, and it was becoming increasingly difficult to find a free modem for the connection. This also led to delays in getting feedback from the reclosers. Sometimes the GSM modems jammed and required a site visit to bring them back online again. GPRS, on the other hand, could be used on a real‐time basis without the need for regular polling, eliminating the scalability issues GSM presented. GPRS data also had the benefits of being easy to deploy, working everywhere and of having lower communication costs. The only problem was that pole‐top devices use a legacy serial protocol, IEC 101, whereas with packet‐based communications such as GPRS this protocol does not work. GSM uses the IEC 101 protocol but its large‐scale deployment would have required significant investment in modems at the SCADA end to ensure timely feedback.