Dealing with harmonic problems produced from the use of adjustable speed drives in industrial oil pumping field

The paper investigates a real offshore system supplied by submarine cable which has a large number of adjustable speed drives (ASD). The choice of the ASD is very essential to the pumping field operation. One strategy is to evaluate and simulate the application of different ASD models, 6-, 12-, and 18-pulse, in offshore oil field industry and how to reduce the produced harmonics. The paper presents results of the harmonic distortion levels produced by each type and compare it to the IEEE-519 limits. The study considers the worst (emergency) configuration of the system that is when only one main transformer (50 MVA 115-13.8 kV) is supplying the whole system. A frequency scan analysis is conducted to study the effect of the submarine cables shunt capacitance in introducing resonance in the system. The effect of phase shift of the transformer is investigated and used as a method to reduce and mitigate of the harmonic distortion.