Calculating Inductance of parallel DC cables

I am currently doing a short-circuit analysis of a vessel. The vessel has a DC busbar where all the converters are connected to it. Since the inductance value of the cables holds significant importance when analyzing short-circuits I tried to calculate and add inductance & resistance in simscape environment to model these cables. IEC documents give inductance calculations for single core cables. I want to calculate inductance for multiple single core cables or cables with more than 1 core inside. Is there any general approach I can use, or any source that might be helpfull?

Answer 1

[Simar]

Hi Mert,

As per my understanding you want to understand how to calculate the inductance for multiple single-core cables with more than one core inside, especially in the context of a short-circuit analysis of a vessel with a DC busbar. For calculating within a Simscape environment, one can follow a general approach based on electrical engineering principles and then adapt those calculations to the Simscape model. Here are the steps and considerations:

1. Understand Cable Configurations:

• Single-Core Cables in Parallel: When having multiple single-core cables running parallel to each other, the total inductance can be affected by mutual inductance between the cables.
• Multicore Cables: These cables have their cores twisted together, which can significantly impact the inductance due to the proximity and configuration of the conductors.

2. Basic Inductance Formulas:

Self-inductance for a single conductor can be calculated using standard formulas, calculating inductance for multiple conductors requires accounting for both self-inductance and mutual inductance.

3. Mutual Inductance:

Mutual inductance between two parallel conductors depends on their distance apart and their lengths. Can find formulas for mutual inductance in electrical engineering references. The total inductance of the system can increase or decrease based on the phase of currents in these conductors.

4. Proximity Effect:

For multicore cables or closely spaced single-core cables, the proximity effect must be considered. This effect can increase the inductance and resistance of each conductor due to the magnetic field's influence from neighbouring conductors.

5. Use of Standards and Documents:

As mentioned, IEC provides inductance calculations for single-core cables, it might also offer guidance or formulas for dealing with multicore or parallel cables. Reviewing detailed standards such as “IEC 60287” and “IEC 60909” might provide additional insights.

6. Modelling in Simscape:

After calculating the inductance and resistance values, use Simscape’ s electrical components to model cables. Use the Controlled Voltage Source and Controlled Current Source blocks to simulate the electrical behaviour based on the calculations. For complex cable configurations, consider using the Simscape Multibody for a more detailed electromagnetic model, if necessary.

Combining principles from electrical engineering with standards and simulation tools can lead to accurate modelling for short-circuit analysis in Simscape. Ensure the assumptions made in calculations align with the physical layout and materials of specific application.

Please refer to the following documentation links-

• Controlled Voltage Source- https://www.mathworks.com/help/sps/powersys/ref/controlledvoltagesource.html?searchHighlight=Controlled%20Voltage%20Source&s_tid=srchtitle_support_results_1_Controlled%20Voltage%20Source
• Controlled Current Source- https://www.mathworks.com/help/sps/powersys/ref/controlledcurrentsource.html?searchHighlight=Controlled%20CurrentSource&s_tid=srchtitle_support_results_1_Controlled%20CurrentSource
• Simscape Multibody- https://www.mathworks.com/help/sm/index.html?searchHighlight=simscape%20Multibody&s_tid=srchtitle_support_results_1_simscape%20Multibody

Hope it helps!

Best Regards,

Simar