Contingency Analysis
The new Contingency Analysis tool in DIgSILENT PowerFactory has been
designed to offer a high degree of flexibility in configuration,
calculation methods and reporting options. Single and multiple
timephase contingency analyses are available, both of which offer
automatic or userdefined contingency creation based on events, and the
consideration of controller time constants and thermal (shortterm)
ratings.
Calculation Options for Contingency Analysis:
Support of three calculation methods:
 AC load flow calculation
 DC load flow calculation
 Combined DC/AC calculation; i.e. full DC load flow calculation and automatic recalculation of
critical contingencies by AC load flow
Single and Multiple TimePhase calculations. Multiple timephase
contingency analysis facilitates userdefined postfault actions within
discrete time periods.
Generator Effectiveness and Quad Booster Effectiveness calculation:
This calculation feature assists the planner in defining appropriate
measures for overstressed components in critical contingency cases:
During contingency analysis, the possible impact of individual generator
redispatch or transformer tap changes on overstressed lines is
evaluated. Corresponding reports are available that list the generator
and quad booster effectiveness on a percase basis.
Ultimate Performance via Grid Computing: Possibility to perform
the contingency analysis calculation in parallel (on multicore machines
and/or clustered PCs)
Management of Contingencies/Fault Cases:
Userfriendly definition of contingencies (n1, n2, nk, busbar)
as ‘Fault Cases’ supporting userdefined events to model postfault
actions (reswitching, redispatching, tap adjustment, load shedding)
Clustering of ‘Fault Cases’ into ‘Fault Groups’ for efficient data management
Special Operational Libraries to manage ‘Fault Cases’ and ‘Fault Groups’ for future reuse
Automatic creation of contingency cases based on Fault Cases, considering current network topology
Result File Management:
Recording of results in (sparse) result file; accessible for any kind of export and/or customerspecific postprocessing
Predefined and userdefinable monitoring lists for recording of
results; selection of individual components, component classes and their
associated variables to be recorded. Any available calculation result
for a standard load flow calculation is accessible during contingency
analysis.
Userdefined limits for recording of results (thermal loadings, voltage limits, voltage step change)
Reports:
A wide range of standard reports is available, facilitating summary
views or the presentation of results on a percontingency basis:
Maximum Loadings Report
Loading Violations (per case) Report
Voltage Ranges Report
Voltage Violations (per case) Report
Generator and Quad Booster Effectiveness Report
Other key features:
Tracing Facilities: Use of the new ‘Trace’ function to step
through events in a multiple timephase contingency, while viewing
updated results in the singleline graphic
Support of componentwise ShortTerm Ratings based on prefault loading and postfault time
Special “Contingency Analysis” toolbar for userfriendly configuration, calculation and reporting
Parallel Computing Option:
Calculation of contingencies in parallel represents an important required computation time reduction depending on the number of cores being used.
Management of the parallel computation function
Dedicated settings for the execution of the contingency analysis
Quasi Dynamic Simulation
Power Factory offers the execution of medium to long term simulations thanks to the new Quasi Dynamic Simulation engine. If simulation periods ranging from hours up to years are under investigation, the Quasi Dynamic Simulation automates the entire simulation process. Multiple load flow calculations are carried out with userdefined time step sizes between each simulation. The results from each calculation are stored and are available for post processing. The tool is particularly suitable for planning studies in which long term load and generation profiles are defined in parallel with multiple contingency scenarios, variations and expansion stages. In terms of user handling, the tool is easy to use.
Additional features:
 All load flow calculation variabes are available for storing and plotting
 Statistical data for the variables
 Results such as maximum, minimum, average, variance, etc. are provided
 Energy estimation for the studied time interval
 Tabular reports for the most relevant results as loading/voltage ranges and nonconvergency cases
 Export to HTML or Excel options
Network Reduction
The typical application of the network reduction tool is a project where
a specific network has to be analyzed but cannot be studied
independently of a neighbouring network of the same or of a higher or
lower voltage level. In this case, one option is to model both networks
in detail for the calculation. However, there may be situations in which
it is not desirable to perform studies with the complete model; for
example when the calculation time would increase significantly, or when
the data of the neighbouring network is confidential. In such cases it
is good practise to provide a representation of the neighbouring network
which contains the interface nodes (connection points) which may be
connected by equivalent impedances and voltage sources.
The objective of Network Reduction is to calculate the parameters of a
reduced AC equivalent of part of a network, as defined by a boundary.
This boundary must completely split the network into two parts. The
equivalent network is valid for both load flow and shortcircuit
calculations. ,Following this, a model variation can be optionally
created in the PowerFactory database, whereby the full representation of
the portion of network that has been reduced is replaced by the
equivalent.
General Features
 Flexible definition and maintenance of network boundaries with Boundary Definition Tool. Various
features such as colouring of boundaries and topological checks  Network Reduction can be calculated at any appropriate boundary
 Support of load, standard Ward (PQequivalent), extended Ward (PVequivalent) and REIDIMO equivalents
 Support of shortcircuit equivalents for transient, subtransient, peakmake and peakbreak currents
 The reduced network can be created in a network variation. This
allows for simple comparison and swapping between reduced and
nonreduced cases.  Robust reduction algorithms based on the sensitivity approach,
i.e. reduced network matches for the current operating point as well as
for network sensitivities  Implicit result verification feature
Protection Functions
The basic functional model library of DIgSILENT PowerFactory’s
protection analysis tool has been extended to include additional devices
such as CTs, VTs, relays, fuses and more complex protection schemes
including userdefined modelling capabilities. Additionally, there are
specially designed interactive VIs (Virtual Instruments) for displaying
system quantities and, more importantly, for modifying protection
settings in the graphical environment. This last feature is especially
useful, as coordinated settings between different protection schemes can
be modified via the cursor in the graphical environment, following
which the settings in both the database and the simulation environment
are also updated.
All protective devices are fullyfunctional under steadystate and
transient conditions, allowing device response assessment under all
possible simulation modes, including load flow calculation, fault
analysis, RMS and Instantaneous Values (EMT) simulation.
PowerFactory’s main protection features are:
 Accurate steadystate relay checking via shortcircuit and load flow (balanced & unbalanced)
 Precise dynamic relay checking with RMS and EMT simulations
 Consideration of current transformer saturation
 Diagrams for overcurrent and distance coordination:
 Timeovercurrent diagrams
 RX characteristic diagrams
 Time distance diagrams
 Automatic Protection Coordination Wizard for timeovercurrent protection schemes
 Shortcircuit trace to examine the performance of a protection scheme in response to a fault or combination of faults
Protection Model Library and Functionality
The DIgSILENT PowerFactory protection analysis tool contains a
comprehensive protection device model library. All relays are modelled
for steadystate calculations (shortcircuit, load flow), RMS and EMT
simulation modes. The definition of relay types is highly flexible via
block diagrams. For RMS and EMT simulation purposes, relays may be
extended and adopted to cope with user specific requirements via the
PowerFactory DSL language The features of the protection model library
are listed below.
Fuses are represented by their melting curves. It is possible to take minimum and maximum melting curves into account.
TimeOvercurrent Relays for 1phase, 3phase, ground and negative
sequence time overcurrents. Additionally, the relay characteristics
can incorporate the following standards and solution methods:
 IEC 2553, ANSI/IEEE and ANSI/IEEE squared
 ABB/Westinghouse CO (Mdar)
 Linear approximation, Hermitespline approximation
 Analytical expressions via builtin formula editor and analyser (DSL)
Instantaneous Overcurrent Relays for 1 phase, 3phase, ground and negative sequence time overcurrents.
Directional Relays for overcurrent, power, ground current, and
any combination of time and instantaneous overcurrent relays.
Additionally, voltage and current polarization is used for the detection
of negative and zero sequence components considering also dual
polarization. Optional: with voltage memory.
Distance Relays for phase, ground and zone distance protection.
Provision is available for incorporating overcurrent and underimpedance
starting units (UI or Z) as well as angle underimpedance.
Different characteristics are available for distance relay zones including:
 MHO, offset MHO
 Polygonal, offset polygonal
 Tomatoes, lens and circle
 R/X Blinders and quadrilateral
Support of various polarisations such as:
 Selfpolarised
 Cross polarised (90ø connection)
 Positive, negative sequence polarised
 Optional: voltage memory
Zero sequence and parallel line compensation
Voltage Relays for undervoltage, instantaneous voltage, voltage balance and unbalance.
Additional devices such as: Breaker Fail, Motor Protection, Generator
Protection, Differential Protection, Reclosing Relays, Low Voltage
Circuit Breakers, and OutofStep Relays.
In addition to these protection functions and relays, DIgSILENT
PowerFactory provides further devices and characteristics for more
detailed protection system modelling, such as:
 Current and voltage transformers that include saturation effects
 Conductor, cable damage curves, cable overload curves and inrush peak current modelling
 Transformer damage curves (ANSI/IEEE Standard C57.1091985) and inrush peak current modelling
 Motor starting curves, cold and hot stall, inrush peak current modelling, and any userdefined curves
All protection device models are implemented within the composite model
frame environment. This allows users to easily design and implement
their own models, by utilising the graphical user interface for
constructing block diagrams.
Output & Graphical Representation
TimeOvercurrent Diagrams
 Overcurrent curve adjustment using drag & drop
 Display of tripping curve tolerances during drag & drop
 Userdefined labels
 Tripping times are automatically displayed for calculated currents in timeovercurrent diagrams
 Display of an unlimited number of overcurrent curves in diagrams
 Simple creation and addition of diagrams via single line graphics
 Display of motor starting curves, conductor/cable and transformer damage curves
 Balloon help showing name of relay, etc.
 Doubleclick on curves to change relay settings
 Additional axis for voltage levels
 Display of single line diagram paths in timeovercurrent diagrams
RX Characteristic Diagrams
 Display branch impedances with several options
 Automatic display of calculated impedances
 Adding relays with offset
 Flexible display of zones (starting zones, etc.)
Time Distance Diagrams
 Different methods for calculating curves: kilometrical or shortcircuit sweep method
 Forward and/or reverse diagram
 Selectivity check of distance and overcurrent relays/fuses in same diagram
 Separate overreach zone representation
 Additional axis showing relay locations and busbars/terminals
 Selectable xaxis scaling (length, impedance, reactance, 1/conductance)
Single Line Diagram
 Colouring of switches according to relay locations, relay tripping times
 Display of relay tripping times in result boxes
 Additional text boxes for relay settings
Relay Setting Report
 Simplified ASCII reports genertaed in the output window
 Tabular report command can be customised to deal with the structure of complex relay models and for a protective device class
Relay Tripping Report
OvercurrentTime Protection
The coordination of overcurrenttime protection is performed graphically
using the currenttime diagram as the basis. Relay settings are
modified using drag & drop to move characteristics. Shortcircuit
currents calculated by the shortcircuit command, are shown in the
diagram as a vertical line. In addition, the corresponding tripping
times of the relays are displayed. Coordination between relays at
different voltage levels is available. Therefore, currents are
automatically based on the leading voltage level, which can be selected
by the user.
Distance Protection
For distance protection coordination, two powerful graphical features
are integrated. The first of these features is the RX diagram for
displaying the tripping zone of distance relays and the line impedances.
Several relays can be visualised in the same RX diagram. This can be
useful for the comparison of two relays that are located at different
ends of the same line. The relay characteristics and the impedance
characteristic of the connecting line will be shown in the same RX
diagram. Following shortcircuit calculations, the measured impedances
are visualised with a marker in the shape of a small arrow or cross.
From the location of the marker the user can see the tripped zone and
its associated tripping time. For dynamic simulation, measured
impedances of the relays can be displayed, thereby visualising the
functioning of power swing blocking or outofstep tripping relays.
The second powerful graphical feature is the timedistance diagram,
which is used for checking the selectivity between relays along a
coordination path. The relays on a coordination path can be displayed in
diagrams for forward, reverse or for both directions. Consequently, it
is very easy to check the selectivity of the relays along a coordination
path. Two different methods for calculation of the tripping curves are
provided. These are the kilometric and the shortcircuit method.
 Kilometric method: The reach of the zones is calculated from the
intersection of the given positive sequence impedance of the lines, and
the impedance characteristic of the relays.  Shortcircuit method: This is the main method for checking the
selectivity. Shortcircuits (userdefined fault type) are calculated
along the coordination path. The tripping times for the timedistance
curve are determined using the calculated impedances. The starting
signal of a relay is also considered.
A special feature of the distance protection is the consideration of
blocking signals or POTT (permissive overreach transfer tripping), PUTT
(permissive underreach transfer tripping), which are also taken into
account. In addition to tripping curves of distance relays, the curves
of overcurrent relays can be displayed and coordinated in the same
diagram using the shortcircuit method.
Both the kilometric and the shortcircuit method consider breaker
opening times in the calculation of tripping times. The breaker opening
time can be optionally ignored.
Coordination Assistant
The coordination assistant helps the protection engineer to quickly find wellstructured and consistent network protection solutions and afterwards easily analyse, tune and implement the chosen settings in the protection devices. The algorithm is flexible, automated and comprehensive featuring the following options:
 Userdefinable coordination area
 Automatic coordination of distance protection relays
 Determination of relay protection zones
 Reactive reach via zonefactors (independent, cumulative, ref. to line 1)
 Resistive reach based on prospective fault/load resistance
 Output options:
 Tabular report
 Timedistance diagram
 Automatic update of protection devices
 Time distance plots are automatically obtained after the algorithm
Cable Analysis
Cable Sizing
 Automatic cable sizing based on IEC 60364552, NF C15100, NF C13200, and BS 7671, etc.
 Cable reinforcement optimisation
 Verification of global and/or individual thermal and shortcircuit constraints
 Verification of userdefined voltage drops per terminal and/or feeders
 Balanced (positive sequence) or unbalanced calculation with support of all phase technologies (1, 2 and 3phase systems, w/o neutral conductor)
 System phase technology and cable type consistency checks in the feeder
 Various verification reports and automatic modification of cable types in the existing network via network Variations
Cable Ampacity Calculation
 Cable Ampacity calculation based on IEC 60287 or NeherMcGrath method
 Evaluation of maximum allowable current for cables based on cable material, laying arrangement and environmental data
 Rich reports and automatic modification of cable derating factors in the existing network via network Variations
Power Quality and Harmonic Analysis
The harmonic analysis functionality is ideal for applications in
transmission, distribution and industrial networks for filter design,
ripple control signal simulation or for the determination of network
resonance frequencies.
For analysing the impact of harmonics in power systems, DIgSILENT PowerFactory provides two harmonic analysis functions.
Harmonic Load Flow
The DIgSILENT PowerFactory harmonic load flow features the calculation
of harmonic voltage and current distributions based on defined harmonic
sources and grid characteristics. It allows the modelling of any
userdefined harmonic voltage or current source, both in magnitude and
phase including interharmonics. The harmonic sources can be located at
any busbar in the power system and may be implemented within any network
topology.
Harmonic current sources can be associated with any load, SVC (TCR
injection), rectifier or inverter. Harmonic voltage sources can be
modelled using the AC voltage source model or the PWM AC/DC converter
model. The builtin rectifier models inject the spectrum of ideal
6pulse rectifiers if no other injection has been defined.
DIgSILENT PowerFactory supports any type of characteristic harmonic,
uncharacteristic harmonic (even harmonics etc.) and noninteger
(inter) harmonics. Unbalanced harmonic sources (e.g. singlephase
rectifiers) are also fullysupported. The analysis of interharmonics or
unbalanced harmonic sources is based on a complete abcphase network
model.
Because of the phase correct representation of harmonic sources and
network elements, the superposition of harmonic currents injected by
6pulse rectifiers (via YY and YD transformers leading to a reduction
in 5th, 7th, 17th, 19th etc. harmonic currents) is modelled correctly.
DIgSILENT PowerFactory calculates all symmetrical and asymmetrical
harmonic indices for currents and voltages, as defined by relevant IEEE
standards, including harmonic current indices and harmonic losses, such
as:
 THD
and HD ((Total) Harmonic Distortion)  TAD (Total Arithmetic Distortion)
 IT product
 Harmonic losses
 Active and reactive power at any frequency
 Total active and reactive power, displacement and power factor
 RMS values
 Unbalance factors
 Integer and noninteger harmonic order values
 Flicker Assessment:
 Pst, Plt (short and longterm flicker disturbance factors; continuous an switching operation)
 Relative voltage change value
Results can be represented:
 In the single line diagram (total harmonic indices)
 As histograms (frequency domain)
 As waveform (transformation into the time domain)
 As profile (e.g. THD versus busbars)
The frequency dependent representation of network elements such as
lines, cables, two and threewinding transformers, machines, loads,
filter banks etc. for considering skin effects is fullysupported.
Frequency Sweep
The frequency sweep performs a continuous analysis in the frequency
domain. The most common application is the calculation of self and
mutual network impedances for identifying the resonance points of the
network and for supporting filter design.
 All impedances are calculated simultaneously in the same run.
Since DIgSILENT PowerFactory uses a variable stepsize algorithm, the
calculation time of frequency sweeps is very low while the resolution
around resonance points remains very high (typically 0.1 Hz)  Frequency sweeps can either be performed with the
positivesequence network model (very fast) or the complete threephase
abcnetwork model  Calculation of self and mutual network impedances
 Calculation of voltage amplification factors
 Impedance plots may be created in either Bode, Nyquist or magnitude/phase forms
In addition to common applications relating to harmonic distortion,
PowerFactory’s Frequency Sweep function can also be used for
subsynchronous resonance studies. The calculation of damping and
undamping torques is supported by special scripts.
Network Modelling
The skin effect is considered by associating frequency
characteristics with line or transformer resistances and inductances.
These characteristics can be specified by either setting the parameters
of a polynomial expression or by entering the characteristic point by
point using tables. DIgSILENT PowerFactory uses cubic splines or hermite
polynoms for appropriate interpolation.
 Lines are modelled either by approximate PI sections or by the highlyaccurate distributed parameter
line model that should always be used for long lines or high frequency
applications. The skin effect can be included in both line models.  Filters can be specified by either ‘layout’ parameters or
‘design’ parameters. ‘Layout’ parameters are typically the rated
reactive power, the resonance frequency and the quality factor.
‘Design’ parameters are the actual R, L, and C values.
In addition to the explicit specification of frequency dependent
resistance or inductance via parameter characteristics, overhead lines
can be modelled by defining the tower geometry and cables can be
modelled by specifying the cable layout. In such cases, frequency
dependent effects, such as the skin effect or frequency dependent earth
return, are automatically calculated and considered by the model.
Ripple Control Signals
DIgSILENT PowerFactory provides full support for analyzing and
dimensioning ripple control systems. Series and parallel coupling of
ripple control systems can be modelled including all necessary filter
elements.
 The level of the ripple control signal in the entire network is
calculated and reported in the single line diagram, the output window or
the browser.
Filter Rating
DIgSILENT PowerFactory features a special, easytouse function for
calculating the rating of all components of a filter. All relevant
voltages across all components are calculated and made available in the
‘Filter Sizing’ report.
Power Quality Assessment according to DACHCZ Guideline
The Connection Request Assessment tool ia a very useful feature for power quality calculations according to DACHCZ guideline “Technical Rules for the Assessment of Network Disturbances” as used in Germany, Austria, Switzerland and Czech Republic. A new Connection Request Assessment command is available as well as the Connection Request element. This element represents a new load installation which is to be connected to the grid.
Full assessment of the DACHCZ guideline is performed based on the following criteria:
 Voltage changes and flicker
 Voltage unbalance
 Harmonics
 Commutation notches
 Interharmonic voltages
Following the calculation, a detailed report and summary are made available for further analysis.
 Phase 1: Sectionalising by remote controlled switch devices
 Phase 2: Subsectionalising of strategic areas
 Phase 3: Full system restoration
Sectionalizing supports serial or parallel switch actions (based on station access times).
 Overload alleviation by optimised generator redispatch, load
transfer and load shedding, under consideration of load priorities and
the amount of load that is available for shedding.  Undervoltage loadshedding
For classical bulk power system analysis, it is assumed that postfault
overloads may occur. A full AC load flow, incorporating basic generator
redispatch and automatic tap changing, is used to analyse postfault
system conditions. Additional load transfer and/or load shedding will
then be simulated.
In cases where it can be assumed that system restoration will not lead
to any overloading, the overload alleviation can be omitted and a fast
network connectivity analysis is sufficient.
System Indices and Results
PowerFactory’s Network Reliability Assessment calculates all common
reliability indices. Among others, the following indices are available:
System indices (also available for userdefined feeders, zones, and areas):
 SAIFI, System Average Interruption Frequency Index
 CAIFI, Customer Average Interruption Frequency Index
 SAIDI, System Average Interruption Duration Index
 CAIDI, Customer Average Interruption Duration Index
 ASIFI, Average System Interruption Frequency Index
 ASIDI, Average System Interruption Duration Index
 ASAI, Average Service Availability Index
 ASUI, Average Service Unavailability Index
 ENS, Energy Not Supplied
 AENS, Average Energy Not Supplied
 ACCI, Average Customer Curtailment Index
 EIC, Expected Interruption Cost
 IEAR, Interrupted Energy Assessment Rate
 SES, System Energy Shed
 LOLE, Loss of Load Expectancy
 LOEE, Loss of Energy Expectation
 LOLF, Loss of Load Frequency
 LOLD, Loss of Load Duration
 MAIFI, Momentary Average Interruption Frequency Index
Load Indices:
 AID, Average Interruption Duration
 ACIF, Average Customer Interruption Frequency
 ACIT, Average Customer Interruption Time
 LPIT, Load Point Interruption Time
 LPIF, Load Point Interruption Frequency
 LPENS, Load Point Energy Not Supplied
 LPEIC, Load Point Expected Interruption Costs
 LPCNS, Load Point Customers Not Supplied
 LPPNS, Load Point Power Not Supplied
 LPPS, Load Point Power Shed
 LPES, Load Point Energy Shed
 LPIC, Load Point Interruption Costs
 TCIF, Total Customer Interruption Frequency
 TCIT, Total Customer Interruption Time
Busbar Indices:
 AID, Average Interruption Duration
 LPIF, Yearly Interruption Frequency
 LPIT, Yearly Interruption Time
Special Features
The Network Reliability Assessment is fullyintegrated into PowerFactory, thus profiting from the extremely flexible data management and data management and data handling for setting up individual studies.
High Flexibility
Each contingency case is created and analysed based on events (i.e. switch events, load shedding events, generator redispatch events). By default, the events are created automatically by the reliability calculation algorithm. This allows the user to analyse, adjust and finetune the individual cases in a very flexible manner. The reliability calculation will then consider userdefined events for the FEA instead of creating them automatically.
Tracing of Individual Cases
The user can examine the results of a single fault by running the fault case of interest in the trace mode, a stepbystep analysis that sweeps over the individual actions of the FEA. The switching actions and load shedding/generator dispatch events created by the reliability calculation will then be applied to the network and the results can be viewed and analysed after each time step.
Powerful Output Tools for Result Representation
Results can be viewed in a variety of ways:
 Formatted reports
 Tabular result views (integrated into the PowerFactory Data Manager)
 Graphical result representations
 Various clouring modes
Contribution to Reliability Indices
Postprocessing tools allow the calculation of individual components’ contributions to system indices. In this way the user can study the impact of certain network components (such as lines/cables, transformers, etc.) on the overall system indices. Likewise, loads can be grouped into load classes (industrial, agricultural, domestic, etc.) and their contribution to, for example, energy indices can be evaluated.
Development of indices over years
Taking into account the evolution of the network model and the failure data over time, PowerFactory supports the calculation and visualisation of the reliability indices over years.
Optimal Power Restoration
PowerFactory offers Power Restoration tools for distribution networks incorporating Tie Open Point optimisation methods to achieve an utmost level of resupply. For example, PowerFactory is automatically evaluating – as part of the Power Restoration strategy – the benefits of any move of tie open points in any neighboring feeder.
Additional Features:
 Unbalanced calculations
 Handle of feeder constraints
 Calculation of reliability indices
 Use of load distribution states
 Use of Time Tariffs and Energy Tariffs
Optimal Power Restoration
Optimal Power Restoration studies can be conducted for single case to obtain a “Recovery Scheme Report” – even in the case where no failure data is available for the network components. This function includes the feature to trace the stages of the restoration and view the impacts oh the restoration on the single line graphic.
Features are:
 Animated tracing of individual cases
 Optimal Remote Control Switch (RCS) placement
 Optimal Manual Restoration

Optimal Power Flow (OPF)
The PowerFactory Optimal Power Flow serves as the ideal complement
to the existing load flow functions. Where the standard load flow
calculates branch flows and busbar voltages based on specified “set
points” (active/reactive power generation, generator voltage,
transformer tap positions, etc.), the OPF also calculates the “best
possible” values for optimising a userspecified objective function and a
number of userdefined constraints. In this way, the OPF adds
intelligence and consequently improves efficiency and throughput of
power system studies significantly.Reactive Power Optimisation (OPF I)
 Minimisation of total or partial grid losses
 Maximisation of reactive power reserve
 Reactive power optimisation (interior point method)
 Various controls such as:
 Generator reactive power
 Transformer and shunt taps
 Flexible constraints such as:
 Branch flow and voltage limits
 Generator reactive power limits
 Reactive power reserve
 Boundary flows
Economic Dispatch (OPF II)
 Various objective functions, e.g.:
 Minimisation of losses
 Minimisation of costs (eco dispatch)
 Minimisation of load shedding
 Optimisation of remedial postfault actions, e.g. booster tap changes (pre to postfault)
 AC optimisation (interior point method)
 DC optimisation (linear programming)
 Various controls such as:
 Generator active and reactive power
 Transformer, quad booster and shunt taps
 Flexible constraints such as:
 Branch flow and voltage limits
 Generator active and reactive power limits
 Active and reactive power reserve
 Boundary flows
 Contingency constraints (DC only)

TechnoEconomical Analysis
Technoeconomical calculations are used to perform an economic assessment and comparison of network expansions (projects) through an analysis of:
 Cost of electrical losses
 Economic impact of failure rates (reliabilty)
 Investment costs (including initial costs, initial value, scrap value and expected life span)
 Project timing
The output of the technoeconomical calculation is the Net Present Value (NPV) of the project over the selected period. The command can optionally reconfigure the network at each step of the calculation to minimise losses (using the Tie open Point optimisation command).
Output results are:
 Reference to the result object
 Summary report of selected calculation options, and annual costs, total costs and Net Present Value in the output window

State Estimation
The PowerFactory State Estimator provides an accurate realtime analysis
of the full operating system based on the information provided by
selectively monitored data, e.g. that of an installed SCADA system. The
objective of the state estimator is to assess the generator and load
injections in a way such that the resulting load flow solution matches
as closely as possible the measured branch flows and busbar voltages.
The features of PowerFactory’s State Estimation tool include: Flexible definition of external measurement devices in the network model supporting the following measurement types:
 Active and reactive power branch flows
 Branch current (magnitude)
 Busbar voltage (magnitude)
 Breaker status
 Transformer tap position
 Userdefinable selection of system states to be estimated/optimised:
 Loads: Active and reactive power demand, or alternatively the scaling factor
 Generators and static generators: Active and reactive power generation
 Asynchronous machines: Active power generation
 Static Var Systems: Reactive power injection
 Transformers: Tap positions
 Highprecision estimation of full system state that minimises deviations from measurements
 Fastconverging nonlinear optimisation algorithms
 Observability check based on a novel sensitivity analysis approach
 Detection of unobservable system states
 Grouping of unobservable states in equivalence classes
 Detection of redundant measurement locations
 Innovative patch strategies for unobservable areas; usage of automatically created pseudomeasurements
 Bad data detection in the loop
 Measurement plausibility checks as preprocessing, such as:
 Node sum checks for active and reactive power
 Check for consistent active power flow directions at each side of branch elements
 Check for unrealistic branch losses and unrealistic branch loadings
 Check for negative losses on passive branch elements
 Check for large branch flows on openended branch elements
 Statistical report and colouring modes to visualise measurement qualities
 Fully featured, large scale AC/DC system representation
The PowerFactory State Estimator is supporting a variety of
communication options such as OPC (OLE for Process Control) or Shared
Memory Interface for implementing data interchange with any kind of
SCADA system.  Flexible definition of external measurement devices in the network model supporting the following measurement types:

Stability Analysis Functions (RMS)
RMS Simulation with abc Phase Representation
The abc phase, steadystate component representation of the power
system, features the fundamental frequency analysis of any asymmetrical
grid operation condition. Initialisation via balanced or unbalanced power flow
 Simulation of unbalanced loading conditions in 1, 2 and 3phase AC and DC systems
 Simulation of any number and combination of unbalanced faults including single and doublephase line interruptions
 The abc phase system representation mode avoids tedious handcalculations of equivalent fault impedance
 It also allows for accessing any abc phase quantity for plotting or precise modelling purposes (e.g. protection devices)
Longterm Stability
In many cases stability calculations must be run for long periods thus
taking into account effects of slower control systems such as boiler
control, network exchange control or transformer tapchanger control.
Other applications are varying loads or applications of wind power where
the impact of wind speed fluctuations must be analyzed. In such cases,
shortterm and midterm dynamics have already reached steadystate but
slower transients are still being observed. Longterm stability simulations based on adaptive stepsize
algorithms with accuracycontrolled stepsize adaptation ranging from
milliseconds to several minutes without any decrease in precision or
even manipulation of transient behaviour.  Astable simulation algorithm which fully covers fast transients
as well as slow, semi steadystate dynamics with highprecision event
handling (stiff systems).
Typical Applications
 Voltage stability analysis considering effects of load variations, tapchanger control and reactive power limits
 Longterm flicker analysis in cases such as fluctuating renewable generation or varying loads
 Secondary control analysis and optimisation

Electromagnetic Transients (EMT)
DIgSILENT PowerFactory provides an EMT simulation kernel for solving
power system transient problems such as lightning, switching and
temporary overvoltages, ferroresonance effects or subsynchronous
resonance problems. Together with a comprehensive model library and a
graphical, userdefinable modelling system (DIgSILENT Simulation
Language (DSL)), it provides an extremely flexible and powerful platform
for solving power system electromagnetic transient problems.Any combination of meshed 1, 2, and 3phase AC and/or DC systems can
be represented and solved simultaneously, from HV transmission systems,
down to residential and industrial loads at LV distribution levels.
Standard builtin models include: Lumped and distributed parameter line/cable models; constant and frequencydependent.
 2 and 3winding transformers and autotransformers for 1, 2 or
3phase systems, including stray capacitances, tap dependent impedance
and saturation effects. Flexible definition of nonlinear magnetising
reactance: twoslope, polynomial, fluxcurrent values  Passive RLC branches, capacitor banks and filters of multiple layouts
 Surge arresters, including calculation of energy absorption
 Voltage and current, AC, DC sources
 Impulse sources (to be modelled via DSL)
 VT, CT and PT models, including saturation effects
 Series capacitor, including MOV and bypass switches
 Discrete power electronic components such as diodes, thyristors, IGBTs
 HVDC valve groups (6 and 12pulse Graetz bridge configurations) and other FACTS devices such as SVCs, UPFCs, TCSCs and STATCOMs
 Synchronous and asynchronous machine, doublyfed induction generator
 Circuit breaker models (to be modelled via DSL)
 Stochastic switching (procedures to be implemented via DPL scripts).
The package provides a powerful userfriendly graphical environment for the evaluation of simulation results characterised by:
 Usercustomisable plots for waveform visualisation, including filtering options, scaling, etc.
 Calculation of Fast Fourier Transform (FFT)
 Export capability to COMTRADEFiles, spreadsheetformat, CSVfiles, WMFfiles, etc.

Motor Starting Functions
PowerFactory’s Transient Motor Starting functionality analyses motor
starting scenarios where the effect of a motor starting on the grid
frequency is negligible. In such situations, the typical questions to be
answered are: What is the maximum voltage sag? (This is typically not the initial voltage sag at t=0)
 Will the motor be able to be started against the load torque?
 What is the time required to reach nominal speed?
 How will the supply grid be loaded and which starting options should be considered?
Static Motor Starting
The Static motor Starting simulation makes use of the load flow and
static shortcircuit calculation by executing a series of calculations
to analyse the scenario: First, execution of a load flow calculation when the motors are disconnected from the system
 Then, execution of a shortcircuit calculation, using the complete
method, simultaneously with the occurance of the motors being connected
to the network  Finally, execution of a load flow calculation after the motors have been connected to the system
Transient Motor Starting
The Transient Motor Starting function makes use of the
PowerFactory stability module by providing a preconfigured shortcut for
easytouse motor starting analysis. The motor starting is initiated by
selecting the respective motors within the single line diagram and
initiating the motor starting calculation. A complete symmetrical or asymmetrical AC/DC load flow will be
computed prior to the motor starting event; preselected and
preconfigured VIs are automatically created and scaled with full
flexibility for userconfiguration  Consideration of highprecision, complex motor models with
builtin parameter estimation. A comprehensive library of low voltage,
medium voltage and high voltage motors is provided  Typical motors supported are: single and double cage asynchronous
machines, squirrel and slipring motors, doublefed induction machine,
synchronous motors  Access to the model library for builtin motor driven machine
characteristics (torquespeed characteristics) with flexible
usermodelling support  Support of various starting methods such as direct start,
stardelta starting, variable rotor resistor, thyristor softstarter,
transformer softstarter, variable speed drives, etc.; start from any
rotational speed  Full flexibility in considering starting sequences
 Completion of motor voltages before, during, and after starting as well as successfully motor starting assessment
Full representation of generators with exciter/AVR model support on the
basis of builtin models (e.g. IEEE models) as well as userdefined
models utilising the DSL approach; consideration of protection devices
such as undervoltage protection, overcurrent protection, automatic
restarting relays (EMR) or transformer OLTC. 
Small Signal Stability
The DIgSILENT PowerFactory modal analysis tool features small signal
analysis of a dynamic multimachine system. System representation is
identical to the time domain model. It covers all network components
such as generators, motors, loads, SVS, FACTS, or any other component
used in the system representation, including controllers and power plant
models.Analysis of eigenvalues and eigenvectors is appropriate for applications
such as lowfrequency oscillatory stability studies, PSS tuning,
determination of interconnection options and its basic characteritics,
and is a natural complement to the time domain simulation environment.
It also allows for the computation of modal sensitivities with respect
to generator or power plant controllers, load characteristics, reactive
compensation or any other dynamicallymodelled equipment.PowerFactory’s Eigenvalue Analysis is very userfriendly, requiring
minimal configuration of the command. Its calculation steps are as
follows: Based on a converged and adjusted power flow, the modal analysis
starts with the calculation of the system initial conditions.
Alternatively, any interrupted status of a time domain simulation could
be used as the initial condition.  The system Amatrix is constructed automatically for the complete
system (including generators, general loads, predefined system plant and
controller models as well as DSL devices).  System and model linearisation – including userdefined models –
is performed by iterative procedures. Limiting devices are disabled
automatically. The representation of the network model is equivalent to
the simulation model, allowing a direct comparison/validation between
time domain simulations and modal analysis results.  Support of QRalgorithm as well as the ArnoldiLanczos method.
 Calculation of all eigenvalues based on QR algorithm
 Selective eigenvalue calculation:
 computation of a certain part of the eigenvalue spectrum:
calculation of a userdefinable number of (closest) eigenvalues around a
complex reference point  based on the ArnoldiLanczos method
 recommended as a fast approach for higher order systems for
which calculation of all eigenvalues by QR algorithm is too
timeconsuming
 computation of a certain part of the eigenvalue spectrum:
 Calculation results include eigenvalues (together with oscillation
information such as damped frequency, damping, damping ratio, damping
time constant, etc) and left and right eigenvectors. From eigenvectors,
the individual machines’ controllability, observability, and
participation factors are derived with respect to each mode.  Powerful postprocessing tools for result visualisation
 Tabular result representation of:
 Eigenvalues (including all oscillation information such as damped frequency, damping, damping ratio, damping time constant, etc)
 Eigenvectors (individual controllability, observability, participation of individual machines for any selected mode)
 Eigenvalue Plot
 Visualisation of calculated eigenvalues in the Gaussian plane
 Various filter and scaling options
 Automatic determination of stability border, highlighting of stable/unstable eigenvalues
 Plot has interactive features that facilitate detailed
analysis of individual modes; convenient creation of phasor plots/bar
diagrams for each mode
 Mode Bar Plot
 Bar diagram visualisation of controllability, observability and participation factors of individual machines for a given mode
 Various filter options (e.g. restriction to minimum participation, and/or individual generators)
 Mode Phasor Plot
 Phasor diagram visualization of controllability, observability and participation factors of individual machines for a given mode
 Various filter options
 Automatic detection and highlighting of clusters for convenient identification of interarea modes
 Tabular result representation of:
 Possibility to obtain MATLAB compatible output results and system matrices
 Based on a converged and adjusted power flow, the modal analysis

System Parameter Identification
Builtin system identification and general optimisation procedures
provide an easy and accurate method to perform model parameter
identification on the basis of system tests and field measurements. The
PowerFactory Parameter Identification tool is suitable for parameter
estimation of multiinput multioutput (MIMO) systems, which are
described by any type of nonlinear DSL model. The identification
procedure is fully integrated into the graphical frame definition and
block diagram, and also features parameter estimation for integrated
models (such as loads or generators) which form part of a power system
model.The optimisation procedures provided are highly generic and can also be
used for optimally tuning parameters such as PSS settings according to
defined model response functions. 
Scripting and Automation
DPL (DIgSILENT Programming Language)
The DPLProgramming Language offers a flexible interface for
automating PowerFactory execution tasks. The DPL scripting language adds
a new dimension to PowerFactory software by allowing the implementation
of new calculation functions. Typical examples of userspecific
DPLscripts are: Parametric sweep calculations (e.g. sliding fault location, wind profile load flows)
 Implementation of userspecific commands (e.g. transfer capability analysis, penalty factor calculation)
 Automatic protection coordination and device response checks
 Specific voltage stability analysis via PV/QVcurve analysis, etc.
 Contingency screening according to userspecific needs
 Verification of connection conditions
 Data preprocessing including input/output handling
 Equipment sizing and dimensioning
 Report generation
The DPL objectoriented scripting language is intuitive and easy to learn. The basic set of commands includes:
 C++ like, objectoriented syntax
 Flow commands such as “ifthenelse”, “dowhile”
 Input/import, output/export and reporting routines
 Mathematical expressions, support of vectors and matrices
 Access to any PowerFactory object and parameter including graphical objects
 Definition and execution of any PowerFactory command
 Object filtering and batch execution
 PowerFactory object procedure calls and DPL subroutine calls
 New: Calling of external libraries (DLLs) for linking and executing other applications
Easy Development
DPL’s basic syntax allows for the quick creation of simple highlevel
commands to automate tasks. Such tasks may include renaming objects,
search and replace, postprocessing calculation results and creating
specific reports.Transparency
All parameters of all objects in the network models are accessible.
DPL can be used to query the entire database and to process all
userinput and result parameters without restrictions.Standardising Commands
The DPL language can be used to create new ‘standardised’ DPL
commands that can be used over and over again. DPL commands allow input
parameters to be defined, and can be executed for specific selections of
objects. Proven DPL commands can be safely stored in DPL command
libraries and be used from there without the risk of damaging the
scripts.Control
DPL commands can configure and execute all PowerFactory commands. This
includes not only the load flow and shortcircuits calculation commands,
but also the commands for transient simulation, harmonic analysis,
reliability assessment, etc. New objects can be created by DPL in the
database, and existing objects can be copied, deleted and edited. New
reports can be defined and written to the output window; new graphs can
be created and existing graphs can be adjusted to reflect a userdefined
selection or the current calculation results.Modularity
A DPL command may contain other DPL commands as subroutines. This
modular approach allows the execution of subroutines as independent
commands. Existing commands can be combined to quickly create more
complex commands.Python Integration
PowerFactory offers support for the Python scripting language. Python can now be used for various kinds of automation tasks within PowerFactory and integration tasks from external applications. Although the proprietary builtin scripting language will be supported, there are several good reasons to start using Python:
 Nonproprietary, widely spread and very popular scripting language
 Open source licenced
 Extensive standard libraries and third party modules
 Interfaces to external databases and MSOffice like applications
 Webservices, etc.
 Support for debugging
 Compilable
PowerFactory Module in Python
The functionality of PowerFactory is offered in Python through a dynamic module with the name “powerfaytory.pyd”. Some facts about this module:
 Dynamic modeule implemented in Boost.Python using PowerFactory API
 Offers access to:
 all objects
 all attributes (element data, type data, results)
 all commands (load flow calculation, etc.)
 lots of special builtin functions (DPL functions)
 Usable from:
 within PowerFactory though the new command ComPython
 external (PowerFactory is started by the module as an engine
Integration of a Python Script into PowerFactory
Every Python script file (*.py) is represented in PowerFactory by a ComPython object. A ComPython object holds only the path, not the file itself. With the ” Open in external editor” button it is possible to edit the file directly. The “Execute” button executes the script.
Python scipts (ComPython) objects can be executed like DPL scripts (ComDpl objects) and interrupted with the “Break” button in the main toolbar.
API (Application Interface)
C++ interface for full external automation of PowerFactory
Task Automation Tool for parallelised execution of calculation functions and scripts