Power Quality & Electromagnetic Interference (EMI)

On board vessels and in industrial environments, the quality of the electrical energy and EMI are crucial for the safe and efficient operation of machinery and IT systems. However, through the introduction of new and advanced technologies during newbuilds or refits, systems tend to become increasingly complex. This means unexpected problems, such as low energy efficiency or a shorter lifespan, can easily occur in end-use automation systems or computers. These disturbances can result in unnecessary costs for the end users through excessive energy consumption, system failures or increased maintenance.

Power quality analysis

Thanks to many years of accumulated expertise, Alewijnse can map and optimise the power quality of all types of electrical installations by undertaking comprehensive measurements and analysing the resulting data in accordance with IEC, MIL-STD and class requirements.

Anomalies that are often detected include harmonics, reactive power, network voltage unbalance, electrical power network oscillations, voltage variations, flicker, transients and disturbances in power quality, and electromagnetic interference or compatibility (EMI/EMC).

The following figure shows some aspects of power quality. 

Electromagnetic interference (EMI)

Electromagnetic Interference (EMI) is an unwanted electromagnetic disturbance that damages or degrades the performance of an electrical or electronic system onboard. Electric motors, transformers, high-voltage power lines, switching power supplies, etc., are sources of EMI on board vessels. 

The transmission types are:

• Conducted
• Radiated
• Inductive (Magnetic)
• Capacitive

The following figure shows the influence of conducted emission (EMI) on the sinusoidal voltage form. 

Problems for the user

Users can experience far-reaching problems as a result of poor power quality and EMI within an installation, such as the overheating of transformers, generators and motors; tripping of power breakers; non-compliance with Class requirements (Lloyd’s, Bureau Veritas, DNV-GL, etc), IEC and MIL-STD standards; shortened life spans of equipment; production failure or downtime; and the exceeding of limits that are given in the standards and subsequent failures in electrical systems (low reliability). Additional consequences of poor power quality and EMI include higher fuel consumption, higher energy costs, and unnecessary CO₂ and NOx emissions.

As an Electrical systems integrator, we can perform the following activities:

• Analysis
• Calculation
• Mitigation
• Verification

Analyses

Alewijnse can detect and analyse electrical inefficiencies and advise on power quality and EMI optimisation to comply with the latest IEC, MIL-STD, and Classification Society standards. At an early stage of new construction projects, we can work with our customers to understand their needs and propose the most suitable solutions to meet their objectives for power quality and EMI. 

During refits and modifications, we can use specialised measuring equipment to map EMI and power quality aspects, including harmonics, fast transients, unbalance, conducted emissions, etc.

After an extensive analysis of the problems encountered and the customer’s needs, we design the best customised solutions to deliver optimal cost efficiency and maximise the productivity of the ship’s systems.

Total Harmonic Distortion (THD) calculation

The THD study is an essential part of the Basic design stage of the electrical power plant design. The study will be created based on the MATLAB/Simulink model, the actual configuration of the electrical system, and the load balance data file. The different operation modes will be simulated. 

The document provides calculations of the THD level in percentage, as well as the voltage and current harmonic spectra per operational mode. The report in the recommendation provides mitigation methods to improve power quality.

Mitigation methods

Depending on the complexity of the electrical system onboard and the THD study or power quality and EMI measurements, the mitigation methods will be specified. 

In the implementation plan, the mitigation methods will be described at the technical detail level, including the approach, integration aspects and new component specifications.

Verification

Finally, during acceptance tests on the ship, power quality and EMI will be measured. The measurement data will provide information to the Classification Society, the shipyard, and the electrical integrator that the quality of the AC grid voltage complies with the agreed rules, IEC and MIL-STD standards. Measurement equipment for the power quality and EMI on board vessels is available. 

Successful experiences

Over the years, Alewijnse has successfully optimised power quality and EMI on many ships and industrial installations, including cable layers, research vessels, superyachts, dredgers, LNG tankers, cruise ships, and industrial production machines.

Want to know more? Download our white paper below.