Overview
Ras Laffan Industrial City (RLC) has witnessed rapid industrial growth and is expected to expand further, with multiple industrial facilities being developed to optimize Qatar’s hydrocarbon resources. Ensuring power quality and equipment reliability is critical in this expansion, making harmonic analysis essential for industrial operations.
Importance of Harmonic Analysis in Oil and Gas
Harmonic analysis plays a crucial role in identifying and mitigating periodic vibrations and electrical distortions that can lead to equipment failures. By managing these harmonics, industries can prevent malfunctions, ensure operational efficiency, and maintain power quality.
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Common Cooling Water System (CCWS) – Phase III
According to the RLC Master Plan, RLC provides seawater for cooling, desalination for processing, potable water, and a backup firewater network. Qatar Petroleum (QP) is executing the North Field Expansion (NFE) Project to enhance hydrocarbon reservoir productivity in alignment with Qatar’s 2030 strategy.
The expansion will be located in Lot W2 & W3, adjacent to a future petrochemical facility. The supplied seawater will undergo reverse osmosis (RO) desalination at these lots to produce cooling tower make-up water and other applications.
Project Scope
To meet the water demands of the NFE Project and the future petrochemical plant, QP plans to implement CCWS Phase III. The scope includes:
- Extending cooling water supply to new end users, including NFE Project & Future Petrochemical Industries.
- Installing pumps at Pump House PH3B and additional required facilities.
- Making provisions for Phase IV end users.
Harmonic Analysis Study
This study evaluates the harmonic performance of the power distribution system based on known harmonic sources from the Single Line Diagram (SLD).
Objectives
- Simulate harmonic analysis for various operating conditions.
- Calculate Total Harmonic Distortion (THD-V%) – the voltage distortion injected by non-linear loads.
- Calculate Total Demand Distortion (TDD%) – the current distortion caused by harmonic loads.
- Ensure compliance with IEEE 519-2014 standards at the Point of Common Coupling (PCC) to prevent equipment damage and overheating.
Key System Components
- Variable Speed Drive System (VSDS) modeled based on ABB vendor data:
- Rated Input Capacity: 7.95 MVA
- Input Voltage: 3.16 kV
- Rated Input Current: 1452 A
- Output Voltage: 3.3 kV
- Output Current: 1624 A
- Rectifier & Harmonic Filter modeled using De-Nora vendor data:
- AC Rated Current Input: 2 x 6221 A
- DC Current Output: 14,500 A
- AC Voltage: 116 V
- DC Voltage: 141 V
- HV VSDS Motor (ABB):
- Power: 7500 kW
- Voltage: 3.3 kV
- Current: 1574 A
- Power Factor: 0.88
Harmonic Analysis Findings
The 6.6kV switchboard was designated as the PCC for harmonic measurement.
- THD-V% at each switchboard bus: Ranges from 1.5% to 8%
- Individual Harmonic Distortion (%): Between 1% to 5%
- THD-V at switchboard bus: 2.49%, which complies with IEEE 519-2014 standards
Conclusion
The harmonic study confirms that the THD-V and TDD levels are within acceptable limits as per IEEE 519-2014. This ensures that the power distribution system operates efficiently without risk of equipment damage or performance degradation.
