MAR Consulting facilitated a hazard identification (HAZID) workshop of topsides of three (3) offshore wind substations (OSS) platforms. The methodology was based on the guidewords from DNV-ST-0145 with addition of other relevant topics such as work environment related hazards. The HAZID of offshore wind substations covered the topside during the operational phase only. The substructure including the application of the structure as a system for supporting the topside and for transfer to / from a crew transfer vessel (CTV) were not assessed in this HAZID. Participation from the different engineering contractors, as well as the operator and a 3rd party, was deemed acceptable to ensure enough experience was present to identify potential hazardous scenarios.
The project provisions for close to 100 wind turbine generators (WTGs), 3 offshore alternating current (AC) substations, array cables that string connect the individual turbines to the offshore substations, substation interconnector cables linking the substations to each other, offshore export cables, an onshore export cable system, two onshore substations, and connections to the existing onshore electrical grid infrastructure.
The OSS consists of a multi-story topside supported on a monopile substructure. According to DNV-ST-0145, the offshore substation is defined as a Type A: normally unmanned platform with power equipment. Persons are only expected to be present for inspection and maintenance activities during daytime working hours. Service crew will therefore only access the platform under conditions allowing for safe access to and from the CTV. No service operation vessels (SOV) are anticipated during the lifetime of the facility. Nevertheless, the topside will be equipped with 4 motion compensated gangways (MCG). No helicopter access / manning is expected. Helicopter winching is to be used for rescue only.
During the HAZID workshop, the group risk ranked 106 hazardous scenarios impacting either personnel safety, environment, asset, or reputation. The six (6) scenarios classified as high residual risk with the existing design under evaluation were related to:
- Main crane operation / dropped objects potentially impacting personnel safety and asset;
- Short-circuit on HV/MV equipment resulting in asset damage;
- HV transformer or shunt reactor fire resulting in asset damage.
70 recommendations were raised in total, which will have to followed-up during the detail design of the platforms. Recommendations were raised if:
- Risk was deemed intolerable;
- Non-compliant design;
- Clarifications for uncertainties required;
- Potential improvements identified.