Oil & Gas
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Electrical network design Hassi Messaoud oil field
I. CUSTOMER ENVIRONMENT / PROJECT CONTEXT
Customer profile:
Sonatrach is the Algerian company of research, operating, transport by pipe, transformation and marketing of hydrocarbons and of their derivatives. It also intervenes in other sectors such as the electric generation, the new and renewable energies and the desalination of sea water.
Customer objective and constraints:
The extension to the Hassi Messaoud oil field has in turn led Sonatrach to extend its supply network from 30kV to 220kV.
II. SOLUTION IMPLEMENTATION
Implementation methodology (main phases):
Sonatrach has entrusted the extension of the network and the refurbishment of existing installations to Schneider Electric. This turnkey service includes:
- network design
- supply and commissioning of: 2 x 220kV GIS substations - 47 x 30kV substations - 12 x LV switchboards - 1 supervision system, combined with PLCs for network monitoring and control.
Duration:
3 months
Solution overview (services, products, systems, architectures...):
The work carried out for this project was largely the same as that generally done for electrical network design.
load flow and voltage profile studies
- sizing of equipment (cables, lines, transformers) according to the installed power
- calculation of voltage drops over the various links
- positioning of power transformer tap changers
short-circuit current calculations
- maximum short-circuit current values (device sizing)
- minimum short-circuit current values (protection settings)
protection study
- choice of protection devices
- establishing of settings according to the various operating modes
dynamic stability study
- determining maximum fault clearing times for enabling motors reaccelerations
- impact of high power (7 MW) motor starting on voltage levels
- impact of voltage drops due to the upstream network (220kV)
- establishing a load shedding plan
III. RESULTS / ACHIEVEMENT
Customer benefits:
This specfic study is necessary for a such important site.
This Electrical network design is essential to ensure the good running of the Hassi Messaoud oil field.
IV. ADDITIONAL INFORMATIONS
Other informations
Other electrical network studies:
- Harmonics: control electrical pollution.
- Overvoltages and insulation coordination: guarantee equipment dielectric strength is respected according to expected overvoltage levels (permanent or temporary overvoltages or those due to operating or lightning strikes).
- Dependability : guarantee the availability of electric power ans the reliability of installations adapted to the application.
- Electromagnetic compatibility (EMC): design installations that are fully protected against electromagnetic disturbances.
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Solution breakdown
Main services:- Engineering services: Services
- Electrical network studies
- Power Quality studies
Detail of design services
Calculation of short-circuit currents:
These calculations are achieved using network modelling as defined in IEC 60909. They enable the maximum and minimum short-circuit currents (symmetric and asymmetric) to be determined for phase to phase and phase to earth faults. These calculations are essential for checking:
- making and breaking capacity of interrupting devices
- electrodynamic withstand of equipment (switchboards, busbars, etc.)
- thermal withstand of earthing devices
- site grounding characteristics
- protection settings
Protection study:
This study enables the type of protection to be determined (over current, directional, differential relays, etc.) by taking into consideration the various technical and economic criteria for oil process.
Protection settings are defined according to:
- short-circuit currents of the different operating modes
- transformer switching currents
- motor starting or re-energizing currents
- etc.
Dynamic stability study:
- The main objective of a network dynamic study for this type of installation is to estimate the behaviour of high power asynchronous motors should an electrical incident occur.
- For example, a phase to phase fault in the installation creates a voltage drop and the slowing of motors of substations close to the feeder under fault. If protection setting times are too long, the motors will slow too much to ensure that all loads can be fully brought up to speed once the fault has been cleared. Pre-determined load shedding will allow priority loads to be rescued.
- Further, for this installation, the study enabled network behaviour to be checked should the automatic transfer system (ATS), installed in the main substation, operate. In the event of a fault on one of the 220kV/30kV transformers, the ATS ensures busbar changeover in less than 500ms. The simulation carried out enabled system stability and the re-energizing of high power motors to be validated.
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