Unexpected service disruptions due to toppled transmission towers from storms, flooding or fires normally might mean a long-term outage situation. Rebuilding affected line sections with towers of the same types as those damaged often will take weeks or even months, depending on time of year. Fortunately, thanks to development of emergency restoration systems (ERS) that can be put up in a matter of hours, normal service can be restored quickly even as work proceeds to complete whatever repairs are necessary to the affected line sections.
In spite of buoyant and growing worldwide demand, the ERS market is presently served by less than a handful of suppliers, based mostly in North America. One of these is located north of Montreal. INMR visits SBB to discuss their solution and how they have organized deliveries to meet customer requirements.
According to SBB General Manager, Patrick Gharzani, the motivation for power supply companies to restore service as quickly as possible following line structure collapses goes well beyond monetary considerations alone. There are also potential political and social repercussions such as risk of unrest when local populations find themselves deprived of power for extended periods. Says Gharzani, “all these issues impact the power system operator and require them to restore service as quickly as possible.”
SBB’s decision to focus on the highly specialized ERS business came about mostly through chance. Once a manufacturer of customized steel structures, they were approached with a request to supply a transmission tower. A market opportunity was seen and in 2015 the firm decided to drop other activities and concentrate solely on this sector. They now claim to have the largest share of an estimated global market valued at about US$ 30 million.
The key to being able to respond quickly when there are service interruptions due to damaged structures is to have the components of the ERS already nearby and available. Orders are therefore typically made in advance, either as single large contracts or in some step-by-step buying process to build up inventory. Stocking also ensures that power utilities have the time needed to issue public tenders to comply with normal purchasing rules.
Gharzani emphasizes that success with any ERS requires being able to install replacement towers quickly and without need for civil engineering work, such as for foundations. All that has to be done is to flatten the ground at the specified replacement tower location. An equally important consideration is that there is no requirement for heavy equipment such as cranes to hoist the different tower elements and hardware. For example, Gharzani reports that restoration towers for a damaged 230 kV line in the Philippines were erected during a hurricane. As for limits to the voltages that can be covered, he states that these towers have been used up to 800 kV and can accommodate 6 or even 8 sub-conductors.
Application of ERS is not limited only to calamitous events that damage line sections. Sometimes there is a need to re-route an existing line for a brief period to accommodate a construction project or to allow continued power flow while a line is being upgraded in some way. Gharzani cites such examples from Ireland and Norway.