Beneficial effects on thd values in onshore systems by a natural filter arm offshore feeder.

The purpose of this paper is to show the results of a harmonic study in combined onshore and offshore power system to study the effect of cable connection the two systems made for concession for Burullus Gas Company in Egypt. Electric power distribution has two parts onshore and offshore. The link between them is a combined Power and Communication Umbilical (PCU) cable. The distance between the onshore field and the offshore platform is approximately 60,500 meters. Harmonic producing loads apply in both the onshore and offshore parts of the system. The largest harmonic producing load will be the soft starter for 240-KM-3550 Flash Gas Compressor. The connection of a substantial amount of capacitance in the form of the sub sea cable plus additional generation. The overall effect of connecting the PCU appears to be beneficial. THD values in the onshore system are reduced considerably and the emphasis of the 49th harmonic removed. The same comparison can be made with the Soft Starter By acting as a sink for the 5th harmonic, the connection of the PCU has reduced onshore distortion levels to around half of the values without the PCU. The studies use the harmonic analysis module (HiWave) of the PTW software version5.0.3.3.