EPS has been awarded a contract to replace four 440V switchboards for an Oil&Gas vessel (FPSO) located in the UK Continental Shelf (UKSCS). Offering the complete Engineering Procurement Construction (EPC) solution EPS has been requested to undertake the Front End Engineering Design (FEED), detailed design, project management, planning, supply and construction. The FEED began several weeks ago with detailed design due to commence in December.
Two of the three platforms generated power for to supply all three platforms. Marathon Oil proposed to decommission one of the platforms which operated with three Gas Turbine Generators and the remaining generating platform supporting the non generating platform. The power management system that manages the power flow between all three platforms was complex.
Marathon Oil requested EPS to carry out a number of transient motor starting scenarios to determine whether the existing 33 kV power network would enable a 4.35 MW motor to start on their East Brae platform. The main concern was whether the limited power generation would maintain a voltage within a transient starting voltage dip limitation of no less than 20%.
At the time Marathon Oil did not have a detailed work scope, EPS assisted in creating a work scope in the form of a project plan, the plan consisted of a structured logical plan to help Marathon achieve decommissioning of the Bravo within a certain time period. EPS set and achieved the realistic delivery dates for the following activities:
- Dynamic motor and load model creation
- Gas turbine generator dynamic model
- Check and verify the existing power system model (originally constructed some time ago for an arc flash study)
- Power system Transient stability model
- Transient motor starting report
- FEED study report
- Offshore motor starting measurement recording
- Determination of worst case events and scenarios
- A new 33 kV topside ‘T’ connection solution incorporating new 33 kV switchgear to supply a decommissioning load
- Interplatform protection schemes and designs
- Transformer tap setting optimisation (once the Brae Bravo has been removed)
- Statement of Requirements for 40 MVA transformer energisation studies
- Transformer energisation studies
- Worst case scenario transformer energisation scenarios and events
- Platform neutral earthing schemes and solutions
Load flow, short circuit and protection analysis with an arc flash study revision followed.
EPS has recently completed an electrical protection co-ordination study using power system modelling software for one of our bulk chemical transportation clients. The study reported several areas of concern and addressed where the protection could be improved to prevent future outages out at sea.
EPS was requested to provide a power system study for HV power and increased LV load to accommodate increased oil production rates for a vessel located offshore. The existing Gas Turbine Generators (GTG’s) are to be upgraded to accommodate this. This is to allow 3 out of 4 GTGs to operate during normal operation with the 4th GTG only being required during oil offloading operations. EPS completed the power system study to assess Load Flow, Short Circuit and Transient Motor Starting. The study provided recommendations to mitigate the high short circuit levels due to the increased power generation and voltage dips associated with starting a new 3.5 MW Gas Compressor.
A Teesside based chemical bulk storage company requested EPS to provide Engineering & Design EC&I services for a new compressed gas storage facility. This consisted of a new Motor Control Centre (MCC), hazardous area lighting, compressor motors, pumps, PLC panel and instrumentation to monitor and control the new facility.
EPS has recently completed an electrical protection co-ordination study using ETAP power system modelling software for one of our clients supporting the North Sea Oil&Gas industry. The study reported several areas of concern and addressed where the protection could be improved to prevent future outages out at sea.
EPS recently completed an Arc Flash Energy study for another offshore dive support vessel comprising of offshore surveys, ETAP power system model development and an arc flash energy mitigation report. The report detailed what measures should be put in place to make the electrical distribution system safe and put in place workable solutions to deal with high arc flash energy levels.
EPS was awarded a contract to provide power quality analyser services for several biomass plants located around the UK. All too often we are finding poor quality electrical design and installations where catastrophic failures have occurred due to inadequate engineering. The power study determined what caused the failures and recommended the corrective actions required to prevent future catastrophic failures.
A number of wind turbines were granted planning permission, these wind turbines to be connected to the local 11kV distribution network. The nearest electrical 11kV connection point however was located 2.8 km and the land in between both the wind turbine and 11kV connection point was not owned by the client, this meant that it proved difficult to obtain wayleaves to install a new 11kV cable across the privately owned land. An alternative solution was to install a new 11kV cable at the side of an existing public road with a total route length of 4.8 km.
Using the electrical power software ETAP Engineering Power Solutions conducted a load flow and short circuit study to assess the impact of what the new wind turbines would have on the voltage and assess the magnitude of the additional short circuit current at the 11kV point of connection. SP Energy Networks accepted the load flow and short circuit study report and granted connection to the 11kV distribution network.
Engineering Power Solutions proceeded with the design and was requested to produce a detailed design for an 11kV switch station and an 11kV substation at both ends of the new 11kV cable. To enable the electrical contractors to quote for the work the EPS electrical design workpack included:
- cable routing drawings
- lighting and small power drawings
- electrical protection settings schedules
- Substation location / site drawings
- LV and HV cable calculations
- single line diagrams
- schematic diagrams
- earthing drawings
- 11kV switchboard specifications
- 415V switch gear specifications
- 11kV / 415V transformer specifications
- Substation & switch station layout design
- Co-ordination with civil designers
The wind turbines were successfully installed and connected to the 11kV distribution system to produce a maximum of 2.4 MW electrical power (an average of 21,024,000 kWhrs per annum). This is the equivalent of supplying 840 homes.
A wind farm in Scotland was granted planning permission including a connection in principal was offered, however SSE were concerned of the number of wind turbine transformers that could potentially be energised simultaneously. Energisation of unloaded transformers results in a magnetising inrush current with a high amplitude.
The inrush currents can have many unfavorable effects, including operation failure of transformer differential protection, deterioration of the insulation and mechanical support structure of windings and reduced power quality of the system. Without controlled switching the energisation may occur at any time on the voltage wave producing high current peak, when the transformer core is driven into saturation.
The wind turbines power transformers, a vital components of the 11kV electric power network, required the protective relays with very high dependability, security, and speed of operation. But the magnetising peak current, which is often generated when the transformer is energised, may have caused false tripping of the differential relay protection, therefore a reduction of peak current would be necessary. Some methods have been to reduce high peak currents. Pre-insertion of series resistors and synchronous closing of circuit breakers are examples of the available mitigation techniques.
However, Engineering Power Solutions concluded that the most convenient and cost effective solution in this case was to control transformer energisation through operational procedures by means of controlled step sequencing methods, switching on transformers individually through a PLC based system.