Technical note | Review of DC Circuit Breakers for Submarine Applications

ABSTRACT

The Defence Science and Technology Organisation (DSTO) has undertaken a review of direct current (dc) circuit breakers for submarines as a deliverable under the System Integration (SI) Corporate Enabling Research Program (CERP). This review is conducted to support the evaluation of dc circuit breaker options for future submarines.

EXECUTIVE SUMMARY

The Defence Science and Technology Organisation (DSTO) have undertaken a review of direct current (dc) circuit breakers for submarines as a deliverable under the System Integration (SI) Corporate Enabling Research Program (CERP). This review is conducted to support evaluation of dc circuit breaker options for future submarines.

A circuit breaker is a device capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions. Circuit breakers are installed in submarines to protect crew and plant equipment against large currents caused by electrical faults. With advancements in battery technologies, and the increased use of power electronic converters, the magnitude of fault currents in a future submarine is likely to be substantially larger than that of existing submarines. This report surveys existing and developmental dc circuit breaker technologies to evaluate their ability to handle fault currents in a future submarine. Four major types of technology that are relevant to this application have been considered, broken into two categories:

• Arc based circuit breakers (electro-mechanical)
• Air arc chute circuit breakers
• Vacuum circuit breakers
• Solid state and hybrid circuit breakers
• Solid state circuit breakers
• Solid state and electro-mechanical hybrid circuit breakers

This review found that the wide availability of mature air arc chute circuit breakers lowers the risk they pose for application in a future submarine. However their slow interruption speeds allow substantial fault currents to develop, introducing potential safety risks.

Alternatively vacuum circuit breakers offer a number of distinct technical advantages over arc-chute circuit breakers such as faster interruption speed and low operating noise, however lack of mature technology and research and development for this application is likely to hinder their adaptation in future low voltage dc applications.

Solid state circuit breakers replace the electro-mechanical contacts with semiconductor devices, allowing high speed interruption of current which is beneficial in stopping the development of large fault currents. However, this is achieved at a cost of higher on-state losses. Alternately hybrid circuit breakers use a combination of semiconductor and electro-mechanical switches to achieve low on-state losses and fast current interruption speeds with minimal wear to the electro-mechanical contact. However, developments of these two technologies are still in their early stages, and commercial and practical applications remain limited.

DSTO are currently aware of conflicting views from major industry competitors regarding the magnitude and characteristic of predicted fault currents in future submarines using alternative battery technologies and increased quantities of power electronic conversion.

Based on discussions in this report, DSTO make the following comment and recommendation:

Comment 1:

DSTO is aware of conflicting points of view concerning the ability of current circuit breaker technologies to adequately cope with faults in dc power systems of future submarines with advanced battery systems.

Recommendation 1:

DSTO recommends that detailed fault current studies be conducted to determine whether existing circuit breaker technologies have sufficient fault current breaking ability to meet the requirements of a future submarine.