Pipelines for oil and gas depend on reliable and properly functioning pump stations, located at regular intervals along the lines. Pump drives require a stable voltage at all times, to avoid irregular operation, sagging, or even outages. At the same time, pipelines are often laid out through remote regions, far from populated areas, and subject to harsh environmental conditions. Power lines feeding the pump stations likewise run through desolate country, far away from roads, and with generation remotely situated. Furthermore, to save costs of infrastructure, power is usually transferred by means of single circuit corridors, at sub-transmission or even distribution voltage. The result is long, weak feeders, with low or even very low fault levels as well as poor or no redundancy.
Due to weak lines, voltages will fluctuate, and even minor faults may cause a voltage depression or a collapse. Simultaneously, pump drives, be they of AC or DC type, are voltage sensitive and depend on stable feeding conditions for proper functioning. This is where FACTS is coming in. With SVC, voltages are kept at their rated values for varying load conditions, including start-up of drives.
Alternatively, with Series Compensation, transfer reactances of the power lines are reduced, having a stabilizing effect on voltages. As alternatives to having to reinforce the power corridors by going up in voltage and/or building parallel lines, these are highly cost effective options. They are also time effective, as OH line work typically takes years, while a FACTS device can be in operation in 12-18 months from signing the contract.
Improving the availability of oil & gas fields
Production outages in oil & gas fields are very expensive, and must be prevented at all cost. To reduce production stops due to voltage drops or failures, SVC is a cost and time effective means of eliminating the cause of the problem. SVC will see to it that pump drives and other vital equipment get the voltages they require. The benefit will be stable, uninterrupted operation, enabling a steady flow of oil or gas, as required. At the same time, typically, increased feeder power transfer capability is enabled, thanks to the stabilized system voltage, facilitating possible expansion of the field.
Again, in case of long or very long feeders, Series Capacitors may be considered, as well, as a cost and time effective option to building new lines or going up in system voltage.
A case in particular is off-shore installations, where oil and/or gas are extracted below the sea floor and brought onto platforms located at sea for further transportation to shore. For powering pumps and other equipment on platform, expensive space can be saved by avoiding local power generation, and bringing power from shore through sea cables. The FACTS device required for voltage control on platform will in the typical case be located at the point of common connection on shore.
As should not be forgotten in cases like this, AC cable networks call for additional reactive power control. The overall scope of reactive power control should then encompass the platform just as well as the sea cable(s), to bring about a well regulated voltage and reactive power balance of the whole system.