Ipsa 2 Load Flow & Fault Level

IntroductionThe in-built Load Flow and Fault Level modules within Ipsa 2 have beenoptimised to analyse distribution and industrial networks.

The basis of all power system analyses are load flow and fault levelcalculations. Therefore the Load Flow and Fault Level modules are provided as standard with Ipsa 2.

The Ipsa 2 power systems analysis and modelling application issupplied with Load Flow and Fault Level modules as standard.

Forming the basis of every electrical analysis, the features supportall types of network components, parameters, ratings and models.

The module’s comprehensive functionality enables fault levelcalculations in compliance with the industry-standard G74 andIEC60909 methodologies.

Load Flow

Fault Level

Transient Stability

Protection Grading

Harmonics

Reliability

Scripting

DC Networks

Training & Support

Load Flow FeaturesLoad flow calculations are powered by a fast decoupled loadflow technique that robustly handles both radial andmeshed networks at all voltage levels.

Profile analysis can be undertaken to represent time of daystudies or to model multiple loading scenarios. Contingencyanalysis up to N-3 is also available.

Options include the ability to lock transformer taps, applyload scaling and flat starts, and identify and implementprotection relay operation. Convergence and iteration limitsare also adjustable.

Results are displayed in tables, reports and on diagrams, asspecified by the user. Components are coloured by nominalvoltage, per-unit voltage, status and power flow.

Limit checking is applied and animated power flow symbolsused to indicate flow directions and relative magnitudes.

Multiple network areas and complex DC systems are alsomodelled. Slack busbars are automatically identified foreach defined network area.

The range of components includes:

Synchronous Generators – PV, PQ and slack generatorcontrols are provided together with voltage controlbandwidth and output profiles. Reactive power limits areadded, as required.

Utility Grid Infeed – A grid infeed model is used to portrayexternal networks based on peak and RMS, LLL and LG faultcontributions.User interface

Individual phase voltages and currents are obtained as well as sequence values with fault levels and fault flowscalculated across the network.

Circuit breaker duty calculation is undertaken for busbarsand circuit breakers.

Zero sequence networks are modelled for representation ofearthing systems.

Pre-fault loading is accounted for, and flat voltage profilesapplied before calculation. The X/R ratio is calculated fromthe driving point voltage or a full DC decay method.

IEC60909 Fault Level Method This calculation method reliably implements the IEC60909:2001 standard. Voltage correction factors arespecified and default synchronous machine power factors set.

All three methods of calculating the X/R ratio (A, B and C)are provided.

Full results are displayed for every fault type.

Ipsa 2 Load Flow & Fault Level

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Induction Motors – Represented using single or double cageparameters with load torque-speed characteristics. Doubly-fedmachines for wind turbine modelling are accommodated.

Transformers – Two and three winding with on-load tap-changers takeinto account relay bandwidth and compound voltage control. Vectorgroups are specified as well as auto-transformers and phase-shiftingtransformers.

Load Model – Static load model depicts constant power loads. Theseare grouped and scaled with load transfers due to switchingrepresented. Individual profiles are also added to each load.

Universal Machine – Generic constant power load or generator modelis extended using a user-defined dynamic model and output profiles.

Circuits and Branches – Unlimited rating sets are allowed for overloadchecks. Zero impedance and zero sequence branches are permitted.Multi-section branches are modelled to represent different cable orline types on the same circuit.

Also supports the addition of circuit breakers with intertrippingschemes and protection devices.

Harmonic Filters – The most widely used filter types are included, such as single and double tuned as well as C type.

Mechanically Switched Capacitors – Voltage or power factor controlmethods are represented.

Fault Level FeaturesFault level calculations are performed using a full synchronous machinerepresentation in accordance with ER G74 or IEC60909, as relevant.

These two methodologies are detailed here:

G74 Fault Level MethodThis calculation method is based on full DQ axis machine modelsincluding saturation, saliency, sub-transient, transient decay andsecond harmonic effects. The G74 fault level method has been in usefor many years and has empirical validation.

Fault types and results supported:

• Three phase, single phase to ground, phase to phase and phase tophase to ground

• Peak, asymmetric and symmetric RMS fault results

• Fault waveform plots

• User-defined fault times

Fault waveform plots