Harmonic study to size harmonic filter for electro chlorination package of common cooling seawater system, Qatar Energy

harmonic analysis common cooling water system

The Ras Laffan Industrial City (RLC) has experienced significant growth in its industrial infrastructure and is projected to continue expanding in the future. This expansion involves the construction and activation of multiple industrial facilities, aimed at maximizing the value and production of Qatar’s hydrocarbon reserves.

Harmonic study vital in the oil and gas sector for identifying and managing periodic vibrations and electrical distortions, preventing equipment failures and optimizing operational efficiency. It helps ensure equipment reliability and power quality in dynamic and critical industry operations. To Read more about What is Harmonic Analysis ? Click link

According to the RLC Master plan, RLC provides seawater for cooling, desalinated for process, potable, and a backup firewater network to end users. Qatar Petroleum is executing the “North Field Expansion (NFE) Project” to maximize hydrocarbon reservoir productivity in Qatar in compliance with Qatar’s 2030 strategy.

The proposed locations for these projects are anticipated to be situated in Lot W2&3, in conjunction with a forthcoming petrochemical venture. The seawater is supplied to the conventional reverse osmosis (RO) plant situated at W2 & W3, where it undergoes desalination to produce water suitable for use in the cooling towers and other various applications.

To fulfil the water requirements of the NFE Project and Future Petrochemical Plant in Ras Laffan City, QP plans to proceed with the implementation of the upcoming phase, namely the Common Cooling Water System (CCWS) Phase III for the NFE project.

The supplied seawater will feed to the common RO plant located at Lot W2&3, which will produce desalinated water for the cooling towers make-up and other applications.

The objective of the project is to extend the cooling water supply to new end users (NFE Project & Future Petrochemical Industries) identified under Phase Ill by installing pumps at existing Pump House PH3B and other associated facilities. The project is also required to make suitable provisions for the Phase IV end users.

This document reports the harmonic analysis carried out based on power distribution system and known harmonic sources depicted in key SLD.

The scope of the harmonics electrical system covers the following

  • Simulate harmonics analysis for different operating scenarios
  • To calculate the percentage of Total Harmonics Distortion (THD) viz., voltage distortion injected by the non-linear (harmonic) loads.
  • To calculate the percentage of Total Demand Distortion (TDD) viz., current distortion injected by the harmonics loads.
  • To check whether the THD and TDD caused by non-linear loads are within acceptable limits as per IEEE standard 519 (and if not, suggest suitable mitigation) to ensure that no equipment damage and overheating happens.

The Variable Speed Drive System have been modelled based on the vendor data received from ABB with rated input capacity (7.95 MVA), input voltage (3.16 Kv), rated input current (1452 A), output voltage (3.3 Kv) and output current (1624 A) respectively.

The rectifier and harmonic filter have been modelled based on the vendor data received from De-Nora. The rectifier is modelled based on the AC rated current input of 2 x 6221A and the DC current output of 14500A with the AC current of 116 V and DC Voltage of 141 V.

The HV VSDS motor have been modelled individually based on the data received from ABB such as rating (7500 kW), voltage (3.3 kV), current (1574 A) and power factor (0.88).

Harmonics studies shall be carried out to verify that the harmonics in the system are within acceptable limits specified in IEEE 519-2014 standard. In the IEEE 519 standard, harmonic limits are specified at the point of common coupling (PCC), between the plant and the power supply.

Harmonics studies shall be carried out to verify that the harmonics in the system are within acceptable limits specified in standard. In the standard, harmonic limits are specified at the point of common coupling (PCC), between the plant and the power supply. The 6.6kV switchboard is considered as PCC.

The Total Harmonic Distortion-Voltage (THD-V%) at each switchboard bus was calculated and the value ranges were as follows: Individual harmonic (%) 1to 5 and total harmonic distortion THD (%) 1.5 to 8.

The Total Harmonic Distortion – Voltage (THD-V%) at each switchboard bus was THD-V 2.49 % which is within limit of the standards.

The Results of the harmonic study show that the THD-V and THD-I (TDD) are well within the acceptable limits specified by the standard