Hydro Electric Energy Solution for the Troll Platform and Onshore Plant
Authors: Roberton Rob 
Published: October 2008

This paper provides a history and an overview of the decisions that lead to the selection of national grid provided hydro electric power as the prime motive force for the Troll platform and onshore plant. The use of hydro electric power was a critical success factor with regard to achieving the key project design objectives concerning safety, environmental protection, technical integrity, efficiency, operability and technical cost. The paper explores the pros and cons of a hydro electric solution in relation to these design objectives. Norway is blessed with an abundance of environmentally friendly, cheap hydro electric power. When the decision was taken in 1989 to move the Troll gas processing facilities onshore, the use of electric driven compressors became a technically feasible alternative to the conventional gas turbine drivers used elsewhere in the North Sea. In 1992 Norway passed a new Energy Law which enabled consumers to purchase power direct from the producers thereby opening up competition. The resulting drop in power prices eliminated the need for onsite electric power generation. The paper compares the economics of a hydro electric solution to a gas driven solution when C02 taxation costs are considered. The Troll platform is powered from the Troll onshore plant via a 65 km "composite" 47 kv power and fiber optic control cable. The paper describes the pro's and con's of this solution. The main advantage of this solution was that it facilitated remote control of the platform from the land plant control room thereby providing the means to reduce offshore manning. Additionally, the hydro electric solution reduced maintenance requirements.

Introduction

The Troll project required the equivalent of 270,000 horsepower of compression to move 84 million Sm3 of gas per day from Norway to Continental Europe. When the decision was taken in 1989 to move the Troll gas processing facilities onshore, the use of electric driven Compressors became a technically feasible alternative to the conventional gas turbine drivers used elsewhere in the North Sea. Norway is blessed with an abundance of environmentally friendly, cheap hydro electric power. An extensive study was undertaken in 1989/1990 to investigate the technical feasibility and costs associated with different types of compressor drivers. The final solution chosen employed VSD driven electric motors, a single 132 kv hydro power supply and a simple cycle gas turbine driven power plant. In 1992 Norway passed a new Energy Law which enabled consumers to purchase hydro electric power direct from the producers thereby opening up competition. The resulting drop in power prices eliminated the need for onsite electric power generation. The power plant was replaced with a 300 kv hydro electric supply in order to ensure reliable electric power. Offshore power generation on the platform was replaced by a 65 km, 47 kv power cable laid between the land plant and the platform. The cable is a unique design combining 47 kv power conductors with fiber optic cables located at the center of the power conductors. The fiber optic cables are used to remote control all platform operations from the land plant control room and provides communications.