Impact of MV Standards on Shipboard DC Cable System Size

There is rising interest in medium-voltage direct current (MVDC) power systems for several reasons, including compatibility with DC loads and avoidance of alternating current (AC) frequency synchronization issues when combining multiple source outputs (Cuzner and Singh, 2017). However, few MVDC systems are currently in operation, and there is relatively little experience compared to the knowledge available for medium-voltage alternating current (MVAC) systems. Presently, IEEE Std. 1709 is the only standard that provides guidance for MVDC systems (IEEE, Inc., 2018). This work's objective is to harmonize the information within MVAC standards to produce prospective design and test values for shipboard MVDC cables and evaluate their impact on cable system sizes. Standards for MVAC cable design and test parameters including Basic Lightning Impulse Insulation Level, Withstand Voltage, and cable insulation thickness are compiled to understand the range of parameter values deemed acceptable for MVAC cables. Based on existing shipboard MVAC standards and IEEE Std. 1709, this study produces prospective design and test values for a shipboard MVDC system with a 12 kV Nominal System Voltage. Additionally, a tradeoff was identified with the thickness of cable insulation where a small reduction in cable system size can be achieved but at the expense of substantially greater electric stresses within the insulation.

Automated summary

There is increasing interest in medium-voltage direct current (MVDC) power systems due to their compatibility with DC loads and the ability to avoid AC frequency synchronization issues. However, there is currently limited experience and knowledge compared to medium-voltage alternating current (MVAC) systems. This study aims to harmonize MVAC standards to provide design and test values for shipboard MVDC cables and evaluate their impact on cable system sizes. It also identifies a tradeoff between cable insulation thickness and system size reduction, where reducing insulation thickness can lead to higher electric stresses within the insulation.