We use analytical tools, measurements on site and audit tools together with our joint power system experience. We examine Industrial Power Systems, identify and solve problems and thereby prevent failures before they occur. But frequently we also analyse incidents and breakdowns after they have occurred, thus accumulating valuable experience. We apply this approach to all phases of design, installation, commissioning and operation of land-based and marine plant power supply.
Operational Modes
One of the most important elements of electrical power system studies is the definition of operating modes and scenarios. We use a top down approach to this, starting with the principal operating modes for the entire facility. These are typically normal / max production modes, maintenance modes with various equipment unavailable, essential operation and emergency or critical safety related operation.
Based on these principal modes, the specific electrical modes are derived with their characteristics in terms of load balance, power system topology and circuit breaker status. Finally, the important conditions for each type of power system analysis and calculation can be identified precisely. This approach ensures that all relevant conditions are analysed and that valuable time is not spent on unrealistic scenarios.
Short circuit
- Short circuit analysis according to IEC 60909 or IEC 61363 (marine or offshore plants)
- Calculating mechanical forces and thermal effects from short circuit currents on switchgear buswork (IEC 865)
Load flow
- Load flow analysis in order to determine network voltage profiles, select transformer tappings, analyse loss conditions, etc.
Protection
- Relay coordination and selectivity (discrimination) studies
Harmonic analysis
- Harmonic analysis and filter calculations
Non-linear loads such as Variable Speed Drives, switch mode power supplies and arc furnaces cause harmonic distortions in power systems. This may result in malfunction of sensitive equipment or reduction of component thermal life due to overheating. Vibration or torque oscillations of motors or generator – prime mover string may also occur. Capacitor banks or long cable runs may amplify the problem by causing parallel resonance at characteristic frequencies.
By using experience together with the correct simulation tool, harmonic problems can be analysed and avoided at an early project stage. In existing plants measurements can be combined with harmonic simulation in order to diagnose problems and suggest remedial action.
Dynamic analysis
- Transient stability and dynamic analysis of loss of generation, governor failures, electrical faults, motor starting and reacceleration, etc.
Paper: Why, when and how to perform dynamical studies
This paper is a colaboration between Unitech Power Systems and Sintef as well as Hydro as plant owner and AkerKvaerner as main EPCI contractor. There are two main sections, one dealing with application of dynamical simulations of electrical systems and their different application areas. The other presents a case study with installation of a 10 MW compressor motor on an offshore platform were both simulations and measuremens were conducted.
Download paper (.pdf)
Earthing studies
Switching overvoltages
- Transient overvoltage analysis