Traditionally dynamic positioning vessels have operated in open bus configurations which reduces fault propagation paths between redundancy groups and subsequently reduces the risk of losing position. Modern strengthening of environmental and emissions standards have prompted vessel operators to move to closed bus configurations. While beneficial, closed bus configurations can lead to loss of DP capability if the power system is unable to ride through certain faults. 

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The industry standard solution is the use of live short circuit tests to prove fault ride through capability during closed bus operations. However there is also commentary regarding the danger, difficulty, and potential damage that such testing involves. Live short circuit testing is only possible on some systems due to the fault currents associated with this test, and in many situations are not suitable for the vessel design. This has resulted in a broad range of regulatory and charterer requirements which generally allow alternative methods to be considered.

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OneStep Power has encouraged the dynamic positioning sector to consider power system testing holistically. OneStep Power has developed tools to fill the missing gaps in the industry, not to replace existing best practices. Some of these practices are included in what OneStep Power refers to as an Equivalent Integrity Protocol. 

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OneStep Power’s Equivalent Integrity Protocol is a full testing package that, when completed, provides assurance of a vessel’s equivalent integrity for closed bus operations. 

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OneStep Power’s  Equivalent Integrity Protocol has the following minimum requirements 

1. Protection setting audit (inc. version control)

2. Fuelling Testing

3. Excitation Testing

4. Over-Voltage Testing

5. Earth Fault Testing

6. Relay  & Protective Device Testing

7. Current Sensing Testing

8. Load application & Rejection Testing (Including Phase Back & Load Shedding)

9. Phase Failure Testing

10. Blackout Recovery Testing

11. Harmonic Distortion Testing

12. Fault Ride Through Testing for voltage transients GVRT + ZERODIP