Hydrocarbon Engineering

August

2019

HYDROCARBON

ENGINEERING

n its ‘Annual Energy Outlook 2019, with projections to 2050’,

released earlier this year, the US Energy Information

Administration (EIA) outlined that “the United States

became a net natural gas exporter on an annual basis in

2017 and continued to export more natural gas than it

imported in 2018.”

While there are several technological

advances in oil and gas extraction, transportation, and

processing that have reduced the need to import energy, LNG

exports have contributed significantly to the US’ shift from

being an importer of energy to becoming a net energy

exporter. To export LNG, several types of complexes such as

oil well drilling, gas separation/gathering plants, NGL pipelines

or gas transmission pipelines, tanks and storage terminals

participate, as well as LNG plants. Rotating equipment such as

pumps and compressors are at the heart of each petrochemical

complex. With easy access to electricity, medium voltage (MV)

motors are now driving large rotating equipment, such as

pumps and compressors, that were historically driven by

mechanical prime movers. Electric adjustable speed drives

(ASD) power several of these services.

This article covers two major MV ASD application areas. First,

it provides a brief review of how drives are used for energy

savings in a plant. Extensive literature exists in print and

electronic media detailing case studies where ASDs save energy

by running the driven equipment at below base speed and

hence more efficiently while reducing wear, tear and extending

the life of the overall service. This article will briefly touch on this

aspect. With recent advancements in MV drive topology and

economical power semiconductor switching devices such as

insulated gate bipolar transistors (IGBTs), a new generation of

drives not only provide motor speed and torque control, but

also improve the power factor (PF) at the connected electrical

bus or the overall plant; this is the second aspect this article

focuses on. This is extremely valuable in an environment where

the sources of electric power generation have shifted from coal

and nuclear power to renewables, such as solar, that are power

Manish Verma, TMEIC, USA,

details how using medium voltage adjustable

speed drives can help plants save energy and improve power factor.