The companies refurbish and rebuild existing 33,000 and 132,000 volt power lines in the south east and east of England.
Scope of the project also includes design, feasibility and construction works, as well as to replace electricity lines, increase capacity and renew components on steel pylons.
New fibre optic cables will also be installed to send essential signals to equipment.
The contracts will cover the two years up to the new RIIO-ED1 funding framework, starting in April 2015.
UK Power Networks capital programme director Nirmal Kotecha, said, "We are delighted to be working with three contractors, including two new suppliers, which bring a depth and breadth of knowledge and experience to our business."
"Together, we will deliver essential improvements to our electricity networks to maintain reliable power supplies," Kotecha added.
"Our aim is to deliver exceptional levels of performance in customer service, safety, quality and sustainability. We hope our suppliers will implement innovative ideas which fit in with our vision to be a respected corporate citizen, sustainably cost-efficient and an employer of choice."
UK Power Networks is investing £360m in 2013 to upgrade electrical infrastructure to make sure its networks remain safe and reliable.
The company is responsible for operating 46,837km of overhead electricity network, which brings power to millions of homes and businesses across the south east and east of England.
