When using DC links for power distribution on boards ships, fault protection is of essential importance. Our fast DC breaker switches protect the onboard DC grids against short circuit currents in any part of the grid.
Solid-state 1kV DC breaker switch for marine applications: maximize system up-time and safety on board while minimizing consequential damages when short-circuit occurs.
Increased application of DC grids on vessels
The electrical power requirements of vessels are expanding as systems are expected to support power converters capable of integrating alternative sources and storage systems – including wind and solar power – and battery storage with a range of voltages, frequencies and power levels. DC links are ideal for this, but cannot be safely deployed without the necessary protection. Proper selection of protective devices (such as a DC breaker switch, high-speed fuse or a circuit breaker) and their allocation according to distribution protection zones enables the system integrator to achieve protection selectivity.
Protecting DC grids
The protection device(s) closest to the fault location should isolate the fault before the protection devices at healthy zones are triggered. That is, they operate only on faults within their zone of protection and do not ordinarily sense faults outside that zone. If a fault occurs outside the zone, fault current can flow through, but the protection device(s) will not operate for this through-fault. As a result, the fault location is isolated, enabling the unaffected zones to remain operable. Protection selectivity is achieved once the correct type of device has been chosen and the correct location at distribution protection levels. Selectivity between two protection devices can be complete (the load-side device provides protection without making the other device trip) and partial (the load-side device provides protection up to a given level of over-current, without making the other device trip). These protection devices come with a certain price tag, but the cost is justified thanks to the mitigation of any potential damage to a critical piece of equipment, or expensive system downtime and losses in production resulting from a fault.
DC breaker switches for marine applications
Based on many years of experience in the manufacturing of high-power solid-state switches for different applications, Astrol Electronic and KWx have developed a series of DC breaker switches for the marine industry. This technology provides maximum flexibility for onboard DC grids and provides protection against short-circuit currents in any part of the grid.
Contact our technical consultants for more information about DC breaker switches and their applications. Call +31 (0)186 633 600 or send an e-mail.
Short-circuit interruption within microseconds
A solid-state DC breaker switch interrupts the full short-circuit current in microseconds. With such a time constraint, an autonomous switch control system ensures local fault protection, without the need for external control or fault detection. In addition to rapid over-current protection, the breaker can be programmed to open to a time-current profile. This enables the overall system to reconfigure the behavior of the DC breaker switch within certain predefined boundaries.
The fast opening time of the solid-state breaker limits the fault current and minimizes the negative impact on the load. The current does not reach damaging levels and can be interrupted without forming an arc. Voltage reversal is therefore not required. An IGBT has been selected for this application, due to its ruggedness, speed and low power requirement to run the gate drive. Each array of IGBT modules inside the DC breaker switch operates as a single switch. Although the concept is relatively straightforward, it requires precise synchronization of the different gate controls, and snubbing of stray energy is inevitable to ensure reliability.
The gate drive units are specially designed for use in DC breakers. Included is a customized management system for the gate voltage. Switch-off behavior for both standard and emergency switch-off has been thoroughly tested. Insulation of the different IGBT modules is crucial in order to combat ground bouncing during fast switching.
For that reason, Astrol Electronic developed a special transformer with a very high insulation and PD-free operation to 6kV and beyond. An IGBT in a standard housing (instead of press pack equivalents) fails as an open circuit. Due to this behavior, operation of the switch can continue for a certain amount of time. Depending on the size of the switch and the number of defective elements, de-rating of the current handling of the entire array is not always required. Onboard diagnostics can detect component-level faults, and flag them for replacement.
The backbone of the breaker is a fast controller, which manages the synchronization of the internal switches, and at the same time receives commands from either the overall controller, other breakers in the network, or the sensors that detect local faults. The integrated control module functions as a self-operating system that combines the optical IO with the gate units, high-speed and low-speed analog inputs, as well as optical and Ethernet interfaces to the overall controller. The module also incorporates a Rogowski coil for the detection of fast current changes and a low-speed sensor for accurate DC measurement.
DC breaker switch models
|Ident number||Description||Range||Size in millimeter|
|AA-10411-101||DC breaker switch||0.5kA – 1kV||507 x 507 x 430|
|AA-10411-102||DC breaker switch||1.25kA – 1kV||507 x 507 x 673|
|AA-10411-103||DC breaker switch||2.5kA – 1kV||507 x 507 x 912|
|AA-10411-105||DC breaker switch||3.75kA – 1kV||507 x 507 x 1151|
|AA-10411-108||DC breaker switch||5kA – 1kV||507 x 507 x 1390|