Substation at a depth of 100 metres - a challenging project solved through cooperation

Nordkalk, Finland's leading limestone producer, ordered a new kiosk-type transformer substation from Eltel for its Pargas limestone mine. Norelco's NPM204 was selected as the substation, custom designed and delivered. In the project, the three companies' experts solved challenges, in particular related to the transport and installation of the substation in the confined mining spaces. 

Nordkalk has extensive experience of what it takes to work in a service tunnel at a depth of 100 metres: logistical expertise and meticulous planning. But when the transformer substation inside the rock had to be replaced by a new one, more skills were needed. 

“In practice, the project meant that a substation that had reached the end of its life cycle would be dismantled and a new substation installed in its place. All this had to be done efficiently, during the mine's planned maintenance stoppage," says Markus Mäenpää, Electrical and Automation Engineer at Nordkalk. 

“The project team found the removal of the old substation and the transport of the new substation to a depth of 100 metres in a narrow tunnel with a steep inclination of 17 degrees particularly biting. In addition, precise measurements had to be taken to position the transformer building on the foundations of the old substation," says Jani Vuohijoki,” Team Leader at Eltel. 

The solution was designed with logistics in mind 

The substation was designed and assembled at Norelco's factory in Savonlinna, after which Eltel and Norelco experts worked together to go through the transport and installation phases of the substation.  

The logistics of the tunnel posed particular challenges: a conveyor belt transporting crushed stone running alongside the roadway restricted the available space, and the transport of the large substation required careful planning. The tightness of the transport route and the installation space determined the starting point for the project. The installation area itself also had space for only one substation and one car at a time. 

“We went through the entire substation building and its instrumentation and planned the installation sequence. The substation was then packed into transport units at Norelco and delivered to Nordkalk to await the installation week, says Anssi Kautonen,” Sales Manager at Norelco. 

Old substation out, new one installed in five days 

The new substation was designed to fit the dimensions of the old substation. However, during the installation week, the foundations of the substation were slightly enlarged. 

“Our technicians are used to working in a variety of projects and conditions, often requiring versatile skills and problem-solving abilities. In this project, the size of the new substation did not fully match the length of the old pedestal, so during the installation week we made additional extensions of about 15 cm at both ends of the pedestal. Once the foundation was complete, the new substation building and its instrumentation were installed on top of it," says Jani Vuohijoki. 

Norelco and Eltel had carefully planned the delivery with Nordkalk, and the work was carried out very efficiently: the old one was dismantled in a day, while sorting it for waste and recycling was taken care of. Some of the material was responsibly disposed of as spare parts: 

“Among other things, we saved the old circuit breakers and transformer. So, if there was a fault, we could quickly get the substation back in operation," says Markus Mäenpää. 

Demolition and installation work proceeded as planned

“The team of six people worked together in a very professional manner. Everyone seemed to have a clear understanding of their task and the project schedule," says Mäenpää. 

As the project progressed, logistical challenges were tackled to the end, in particular the relocation of heavy equipment and the precise scheduling of the installation week. Jani Vuohijoki emphasises that the key to the success of the project was the strong teamwork and the commitment of all parties to the tight schedule: 

“Nordkalk's expertise in underground working conditions played a crucial role. Eltel brought solutions to the project that drew on the organisation's expertise and experience. The installation team consisted of experienced professionals who had worked for Eltel for a long time and whose precise work enabled the project to progress on schedule. Norelco, on the other hand, brought with them quality domestic product and expertise in the construction of substations," says Vuohijoki, summing up the team's strengths. 

Conversion to Norelco's reliable "NPM204" 

As the project involved replacing an old transformer substation with a new one, the technical requirements were clear. The rails and components were sized according to the load flows shown in the diagrams, and the LV panel was designed to distribute the loads on the rails evenly. Due to the space requirements of the transformer and the LV panel, the substation house was constructed with Norelco's NPM204. 

Norelco NorMax switchgear was chosen as the MV system. It feeds a 6/0.4kV transformer with a single load break switch, which supplies the low-voltage switchboard. The connection points for the MV cables are at the side of the transformer, so the design had to consider adequate air gaps and connection spaces next to the transformer. 

Norelco's NorPower 5000 MCC was installed in the LV section, feeding the low-voltage outputs, reserve outputs for expansion and feeds to the belt conveyors from the ACB outputs. The choice of components was based on the end customer's existing range of spare parts. 

The new transformer substation will help ensure the operational reliability of Nordkalk's Pargas mine for years to come. The project demonstrated the importance of combining the expertise of the different parties involved and working closely together from the planning stage onwards. Nordkalk's knowledge of the mining industry, Eltel's extensive electrical expertise and Norelco's top product combined to create a solution that meets both current and future needs. This project is an example of an efficient way to implement critical infrastructure projects.

More information

Norelco Oy, Anssi Kautonen, tel. +358 50 525 5315 or anssi.kautonen@norelco.fi
Eltel Networks Oy, Jani Vuohijoki, tel. +358 40 311 3123 or jani.vuohijoki@eltelnetworks.com
Nordkalk Oy Ab, Markus Mäenpää, tel. +358 50 505 8331 or markus.maenpaa@nordkalk.com