Computation method current calculation

What we offer you

You’ll be working at a growing and dynamic family company. The atmosphere is pleasant and informal. You will receive a stipend and compensation for travel expenses. Because of the coronavirus pandemic, you may work at home on your internship assignments and tasks, insofar as this is possible. This will be arranged in consultation with your internship advisor.

Background information

Van der Leun builds high-power switchboards for the maritime sector. Voltages can be 400V to 690V and currents in excess of 2000A. The short-circuit current must be calculated for each switchboard. The calculation is part of the certification procedure of the board.

Certification bodies include Lloyds Register, Bureau Veritas, Det Norske Veritas, American Bureau of Shipping. The customer/shipyard chooses one certification body per ship. This varies per assignment.

Selected components and the construction of the switchboard must meet the calculated value and satisfy the ship classification requirements. There are also customary standards, such as existing IEC standards. When the rules are established in a classification, they may be downloaded from the relevant organisation. For example, Bureau Veritas (BV): https://marine-offshore.bureauveritas.com/rule-notes-and-guidance-notes, e.g. NR467 & NR217

For each project, a report is sent to one classification body (BV, LR, DNV, ABS etc.), which is applicable to the project and the customer. A report can also be sent to a body such as Transport Canada if the ship is to be used in Canadian waters.

For AC switchboards, these calculations are made using the computer program ETAP and other resources.

There is an increasing tendency to use DC switchboards. Van der Leun is also involved in building this type. These switchboards also require short-circuit current calculations. We do not have sufficient in-house expertise in this area, so these calculations are contracted out.

Van der Leun would like to do these calculations within our company, which would make it easier to complete the calculations at an early stage and apply them to the design.

The assignment

Working out a general computation method for DC short-circuit current calculation that can be used for multiple projects, therefore must be suitable for repetition.

The switchboard can be calculated using a model. Modelling of generators, battery systems, frequency drives, breakers and copper busbars to a replacement schedule consisting of resistances, inductions, capacities, diodes and voltage sources.

Using the calculations and simulation of short-circuit tests, the kA value and selectivity can be determined. The kA value is needed for further detailing of the switchboard design.

What-if simulations can be carried out using a computer simulation. A short-circuit is simulated somewhere in the switchboard, and the result is derived from the computation model. For many systems, it is important that only the fault is switched off in such a situation.

The calculations may also give rise to recommendations for dimensions and the assembly of copper components. Filter calculations for both the DC network (elimination of ripple voltage) and the AC network (reducing higher harmonics).

The computation model must meet the customary standards, i.e. existing IEC standards. The computation model can be validated using the calculations from an existing project from the previous year; these calculations were made by a surveyor working for Lloyds Register (LR; contracted expertise). The ship falls under the regulations of Bureau Veritas; otherwise there would be a conflict of interests.

At the end of the internship

Van der Leun will have a workable computation method, simulation via ETAP or similar computer programs. The applicability of existing computation modules will be researched. The computation method will be clearly documented and will, in any case, be validated using past calculations.

About us

Van der Leun has been active in electrical engineering for over 100 years. We work on installation projects all over the world—in the maritime industry, non-residential construction, dredging and the offshore industry. In addition to our main office in Sliedrecht, we also have locations in Romania, China, Vietnam, Singapore, and elsewhere. We have classified our specialties into three divisions: Maritime Systems, Metaalbewerking and Electrobouw. Our 260 employees work together on innovative, reliable integrated solutions for top companies all over the globe. Van der Leun wants to make the world smaller for its customers by providing local solutions worldwide.

Information and application

Got questions? Phone us on +31 (0)184 413 288 and ask for Hans van de Velde, Manager Technical Departments.

If you are interested in doing a work placement with us or if you would like to do final projects with us, we look forward to receiving your motivation and CV via the button below.