The power flow in the network and the voltages and currents in the network are useful for solving the following tasks in the planning, design and operational management of electrical transmission, distribution and industrial networks as well as for other types of networks operated with alternating current (micro-grids, networks on ships and traction power supply):

• Planning of new networks and network areas as well as the analysis and restructuring of existing networks
• Determination of the balanced or unbalanced voltages at all nodes in a symmetrical or asymmetrical network
• Compliance with regulatory requirements of the permissible minimum and maximum operating voltages
•  Determination of the balanced or unbalanced equipment utilization (loading) in a symmetrical or asymmetrical network
• Checking and planning of switching operations and switching configurations
• Optimization of the settings of controllable and adjustable equipment (e.g. tap position for transformers, capacitors)
• Integrated analysis of transmission and distribution networks
• Validated network model based on measurement results

The module (PF) of PSS®SINCAL offers the user fast and robust methods for calculating the load flow/power flow in electrical networks, considering a high modeling depth for elements and controlled elements.

• Robust methods (e.g. Newton-Raphson, current iteration) for calculating the distribution of currents, voltages and power in symmetrical and asymmetrical three-phase systems (as well as 4-wire systems)
• Simulation of controlled elements with regulators such as transformers, capacitors and reactors or the individual control of network elements depending on any variables (e.g. voltage, current, power) in the entire network model
• Support of complex load modeling, user-defined models, phase shifters and asymmetrical transformers as well as simulation of temperature dependencies
• Visualization of weak points in the network based on the results for voltage and utilization

The calculation of short-circuits in networks during planning and operation to assess the load on the equipment must be carried out according to standardized procedures. The results obtained in this way are also required as a basis for further analysis (e.g. protection concept, arc flash evaluation).  

In addition to the short-circuit calculation based on conventional generation, guidelines and standards increasingly require the consideration of converter-based generation. 

• Dimensioning of the equipment according to the expected thermal and mechanical stress in case of short circuits (maximum short circuit currents) 

• Determination of the protection setting based on the short-circuit results (minimum short-circuit currents) 

• Arc flash evaluation based on the short-circuit calculation results 

• Calculation of short circuits under initial load  

• Calculation of the short-circuit current contribution of converter-based generation plants 

The short circuit calculation (SC) module in PSS®SINCAL allows the calculation of short circuits according to standardized procedures and standards. The calculation and its results are then available to be used by other modules. 

• Modeling of the network elements for the short circuit calculation according to the listed standardized procedures and standards

• Calculation methods:
•  IEC 60909/VDE 0102 (2016, 2001, 1990)
• IEC 61363 (1998)
•  IEEE C37 (2016, 1990)
• G74
  
• G74 Issue 2
•  GOST R 52735 (2007), 28249 (1993)

• Short circuit calculation of balanced and unbalanced faults in asymmetrical networks with simulation of individual phases (instead of symmetrical components) and fault impedance 

• Calculation of short-circuit currents for 3-, 2- and 1-phase faults with and without earth connection 

• Calculation of short-circuit currents of converter-based generation plants in the positive and negative sequence system based on Dynamic Voltage Support 

• Calculation of short-circuit currents with initial load based on the power flow results 

• Determination of the maximum switch off time up to thermal destruction of lines and transformers 

• Visualization of the exceeding of permissible short circuit currents of equipment in the network graphic 

When planning and designing electrical networks, it is also useful to observe the frequency-dependent behavior of equipment and the resonance or damping of the harmonics emitted by individual devices:

• Determination and analysis of the frequency-dependent behavior of the network and the resonance frequencies for the current network state
• Automatic execution of the analysis for a high (combinatoric) number of network states (switchovers, maintenance) or depending on all possible positions of controllable elements (e.g. capacitors) in order to include all network configurations in the analysis
• Compliance with regulatory requirements for voltage quality of the permissible minimum and maximum harmonics and distortions of the voltage in the network
• Prevention of harmonics visible in the lighting (flicker)
• Protection of equipment (e.g. capacitors) against damage or destruction by voltages and currents of higher frequencies
• Selection of the vector group of transformers for targeted suppression of individual harmonics (e.g. 5^th and 7^th for YY0 and YY1)
• Design and placement of filters
• Reduction of network areas (boundary networks) as resonance networks, considering the frequency-dependent behavior and the switching states and tap positions of controllable elements (e.g. reconnected filters)
• Integration of the measured behavior of subnetworks that were not simulated in detail in the network model

The module (OB) in PSS®SINCAL offers the user the calculation of frequency responses in static network configurations as well as in combinatorial configurations in harmonic contingency calculation and the calculation of harmonics distribution limit. Furthermore, a functionality for filter design is available.

• Extension of the network model with frequency-dependent model behavior
• Modeling of active and passive resonance networks
• Extensive options for modeling sources with harmonic emission
• Calculation of frequency responses for static states as well as harmonic contingency calculation (malfunction calculation for harmonics): (1) Evaluation of the results for voltages and currents in relation to the limit values from standards IEEE 519 (TIF and IT), THFF and EDC, NY x UNY and NY x INY, IEC 61000-2-4 class 1, 2, or 3 -AND- (2) Evaluation of the results for voltages and currents in relation to user-defined limits
• Graphical display of gain levels over frequency, frequency response locus, impedance areas and harmonic levels in diagrams
• Function for detecting resonance points and for filter design of filter groups

The planning and operational management of complex energy systems require analysis methods in the time domain, so that not only stationary conditions but also dynamic processes that occur in between are included in the assessment of the network state. If the dynamics of the network are shifted to the network levels subordinate to the transmission network, the complexity of the demands on the operators of such systems increases.

• Time domain analysis for compliance with the classical stability concept according to IEEE regarding voltage, frequency and rotor angle stability
• Interactions in the electrical power system to and between converter-based systems
•  Analysis of transients and stresses in the transmission and distribution network in case of symmetrical / balanced and asymmetrical / unbalanced events (e.g. short-circuits, start-up processes, equipment malfunctions)
• Consideration of the influence of different types of generating plants with their control and communication devices
• Verification of the protection concept in case of mutually dependent fault sequences in time domain

The PSS®SINCAL Platform with its dynamics engine PSS®NETOMAC offers the user in this module (ST) the possibility to use it for the most basic applications directly in the PSS®SINCAL GUI, as well as in the expert mode (ExpMode) to use the native user interface of the engine for advanced calculations.

In addition to precise dynamic models, the dynamics engine offers a high degree of freedom in modeling and the possibility of using it as a calculation module in other programs such as the SIGUARD® product family.

• Time domain simulation based on phasors (RMS) for symmetrical and asymmetrical networks with symmetrical and asymmetrical fault conditions, loads and power generation
• Use of proven and successfully validated dynamic models and simulation methods of the PSS®NETOMAC dynamics engine
•  Consideration of the protection device behavior during transients in the time domain simulation and in protection coordination

The dimensioning of equipment in electrical power systems requires the determination of their electrical and mechanical stresses that can occur during operation of these systems as a result of switching operations and faults. Depending on the components, the potential physical phenomena, occurring in different frequency ranges, have to be analyzed and appropriate countermeasures taken in the sizing and protection concepts if limits are violated.

• Analysis of insulation coordination regarding temporary overvoltages (TOV) or those caused by switching operations (SOV) or lightning strikes (LOV)
• Evaluation of very fast transient overvoltages (VFTO)
• Analysis of the effects of switching on and switching off of lines, transformers, electrical machines and inductive loads
• Determination of the stresses on circuit breakers during switching operations
• Analysis of transient voltage recovery (TRV)
• Studies on the connection of converter-based electrical generation and transmission systems such as HVDC, FACTS, wind and photovoltaic systems
• Analysis of subsynchronous resonances (SSR) and interactions (SSTI) with machine drive trains (additionally, module TOR is needed)

The PSS®SINCAL Platform with its PSS®NETOMAC transient engine offers the user in this module (EMT) the possibility to use it for most basic applications directly in the PSS®SINCAL GUI, as well as in expert mode (ExpMode) to use the native user interface of the engine for advanced calculations.

The transient engine offers a very high degree of freedom for modeling and simulation control in addition to the precise and reliable internal dynamic models of equipment.

• Time domain simulation based on instantaneous values for symmetrical and asymmetrical networks with symmetrical and asymmetrical fault conditions, loads and generation
• Initialization of network model by power flow
• Use of proven and successfully validated dynamic models and simulation methods of the PSS®NETOMAC transient engine
• User-friendly and simple control of the calculation and evaluation of results

The task of network protection is to clear faults occurring in the network quickly, reliably and selectively, in order to protect plant and personnel and to ensure the continued operation of undisturbed network areas. A simulative validation of the setting values is necessary in order to verify these requirements.

The following questions must be clarified here:

• Are faults being cleared selectively?
• How long does the network protection need to clear faults?
• Have the protection device parameters been set correctly regarding any load and short circuit currents?

The following is also required:

• Analysis of the fault clearing process
• Analysis of the influence of decentralized generation on network protection
• Creation of grading diagrams based on the setting values
• Documentation of the protection setting values
• Analysis of faults that have occurred
• Reliable detection of earth faults in compensated and isolated networks

The overcurrent time protection simulation (OC) module in PSS®SINCAL enables to simulate the behavior of protection during fault events in the network. Based on the results, the protection behavior can be analyzed and the protection setting values can be checked. Overcurrent time protection devices, fuses, low-voltage circuit breakers, reclosers, bimetals and miniature circuit breakers as well as devices for the earth fault detection are supported.

• Stepwise event-oriented fault simulation including the calculation of fault clearing times

• Interactive analysis of the fault clearing process in the network graphic with relevant information on current, time and color coding of the protection devices

• Checking the setting values and checking for selective fault clearing

• Documentation of protection paths in the network graphic and the associated tripping characteristics in the grading diagram for phase and/or ground steps

• Reports with protection device setting values

Distance protection and differential protection devices are primarily used in meshed distribution networks and in transmission networks. Especially in meshed networks and networks with decentralized generation, effects occur, which change the reach of the protection devices. A simulative validation of the setting values is necessary in order to verify the setting of these protection devices. Primarily the following questions must be clarified here:

• Are faults being cleared selectively?
• How long does the network protection need to clear faults?
• Have the protection device parameters been set correctly regarding any load and short circuit currents?

The following is also required:

• Analysis of the changed reach of protection devices due to effects such as intermediate infeed or parallel follow-up lines (underreach/overreach)
• Post-mortem analysis of faults occurred in the network
• Analysis of the fault clearing process
• Creation of grading diagrams based on the setting values
• Documentation of the protection setting values
• Simulation of voltage and frequency protection, e.g. of decentral energy resources (DER)

The extended protection simulation (SZ) module in PSS®SINCAL extends the functionality of the overcurrent time protection simulation (OC) module. Here distance protection, differential protection, voltage protection and frequency protection device types are additionally supported. Beside the simulation of the behavior of the protection devices and the check of the protection setting values, additional analysis options are available, such as the calculation and display of the actual reach of protection devices.

• Extension of the protection simulation with distance and differential protection devices, voltage and frequency protection
• Stepwise event-oriented fault simulation including the calculation of fault clearing times
• Interactive analysis of the fault clearing process in the network graphic
• Verification of the setting values and checking for selective fault clearing
• Calculation and display of the reach of protection devices in the protection route calculation. Cascaded fault clearings, parallel line effects and intermediate infeeds (e.g. by decentral energy resources) are considered
• Diagrams showing the actual zone reaches of the protection devices for evaluating the tripping behavior (based on fault simulations)
• Post-mortem analysis, fault locater to analyze/locate faults that have occurred in the network

Selectivity in distance protection is achieved by a combination of time and distance graduation. The distance graduation primarily requires the calculation of the zone settings in X and R. Hereby, uncertainties (e.g. due to deviating line data) have to be considered when selecting the graduation factor. Additionally, in meshed networks effects occur that change the reach of the protection devices, this is particularly relevant for backup protection.

• Automatic calculation of protection setting parameters for distance protection devices
• Automatic parameterization/setting of protection devices

The distance protection setting calculation (DI) module in PSS®SINCAL enables automated calculation of zone settings for distance protection devices. Depending on the selected setting strategy, intermediate infeed and parallel follow-up lines, that change the reach of the protection devices, are considered.

• Automatic calculation of distance protection device specific zone settings
• Support of different setting strategies (DISTAL, line impedance, line impedance connected, medium voltage networks)
• Generation of graduation plans based on the calculated setting values of the distance protection devices

The protection security assessment (PSA) module has two functions: Protection analysis and Overcurrent time protection check.

In meshed networks and in networks with a high penetration of distributed generation, the check of orderly function (selectivity, speed, dependability, security) of the network protection solely based on input data/grading diagrams is often insufficient. In addition to observing specific fault events in the protection simulation, it is therefore necessary to check the protection settings of the entire network protection for all possible fault locations. While this must be done in a time-efficient manner, it is also necessary to identify weak points in the network protection reliable.

The growing number of decentral energy resources (DER) with fluctuating power flow increases the number of switching operations in the network. From the point of view of network operation, this requires a quick check of the entire network protection (e.g. before each switching operation).

The protection analysis (PSA) in PSS®SINCAL performs an automated check of the setting values of all protection systems present in the network by calculating fault events in the entire network. As a result, weak points in the network protection are visualized, allowing incorrect settings and faulty protection concepts to be detected.

• Automated check and documentation of the selectivity, speed,pickup dependability and pickup security of the network protection for fault events in the entire network
• Weak points in network protection are reliably detected and highlighted in a results matrix
• Start of the protection simulation from the results matrix to recalculate short circuits at specific fault locations and analyze the protection behavior in detail
• Protection setting check with very little time effort due to automated analysis of the protection behavior fault for fault events in the entire network
• Quality assurance through the improvement of the process for protection coordination (protection concept/setting value calculation/protection analysis/documentation)
• Fast calculation algorithms allow the entire network protection to be checked before each switching operation

When dimensioning fuses in low-voltage networks, the load current, short-circuit current, conductor cross-section, thermal destruction etc. criteria must be checked. Some of these criteria can be tested without simulation, while others, such as the k-factor test, require extensive simulation. The goal is the automated simulative verification of all these criteria, which leads to a considerable reduction of the workload.

The Fuse Dimensioning module (DN) in PSS®SINCAL checks the dimensioning of fuses in meshed and radial low-voltage networks.

Checking the correct dimensioning of fuses regarding:

• Load current
• Safety factor (k factor)
• Maximum switch off time (VDE 0100-410)
• Conductor cross section (VDE 0636)
• Thermal destruction
• Thermal load (VDE 0636)

Employers are obliged by health and safety laws and electric codes to assess working conditions and take appropriate measures to ensure safe working conditions. When working on or in the vicinity of live system parts, service personnel are exposed to the risk of arc flashes. According to accident statistics, arcing faults and their consequences are major causes of injuries in the electrical industry. The following measures help to reduce risks to persons:

• Risk assessment regarding arc flash events
• Definition of safety distances
• Improvements to the network and protection
• Provision of suitable personal protective equipment
•  Affixing of warnings to systems

The module for arc flash analysis (AFH) in PSS®SINCAL enables the calculation of arc flash energy and other parameters and supports the user in optimizing existing equipment. The typical steps of an arc flash analysis are: 

• Calculation based on a network model for 3-phase short-circuit current calculations with detailed simulation of the protection devices and system configurations 

• Arc flash calculation and analysis based on current national and international regulations (DGUV Information 203-077 (2020) or IEEE 1584 (2002, 2018) and NFPA 70E) 

• Display of results in network plans, reports and user-definable warning signs 

• Development of measures for risk minimization based on the calculation results 

The operating equipment of the network must be designed to be thermally short-circuit-proof. This requires a check for thermal destruction. For this purpose, the occurring short-circuit currents must first be determined for all possible fault locations in the network, possibly also for different fault types. From the occurring short-circuit currents and the short-circuit current capability of the equipment, the maximum permissible fault times can be calculated. These maximum fault times must be higher than the fault clearing times of the protection system to ensure that the equipment get not thermally destroyed. This test is very time-consuming when performed manually, so a time-efficient solution is desirable.

Taking into account the tripping behavior of the network protection, there are further requirements.

In meshed networks, the changing short-circuit currents during stepwise fault clearings must be considered.

If inverse tripping characteristics are used (e. g. inverse time OC, reclosers, fuses...), all fault types must be calculated, since here the 1-phase short-circuit current can represent the biggest thermal stress for the equipment at high tripping times.

The thermal destruction analysis in PSS®SINCAL enables both, the network planning, and the protection department to perform an automated check for thermal destruction for all lines, transformers busbars and breakers in the network.

While in the protection department a model of the network protection is usually available, it isn’t in the network planning. Therefore, there are different modes for the check for thermal destruction:

Short circuit mode: The protection systems aren’t modeled in the network to be analyzed. The thermal short circuit withstand capability of the equipment is therefore checked for a predefined maximum fault time. This maximum fault time should correspond to the maximum fault clearing time of the network protection.

Protection mode: Protection systems are modeled for the network. The thermal short circuit withstand capability of equipment, the lines and transformers is therefore checked considering the tripping behavior of the protection systems.

As a result, the user receives a clear representation of all equipment that gets thermally destroyed. With this, measures regarding network protection or network expansion can be determined to restore the thermal short-circuit withstand capability. These measures can then be tested directly with the thermal destruction analysis.

• Automated check for thermal destruction for lines, transformers busbars and breakers in the network with specification of a maximum fault time in the Short-circuit mode.
• Automated check for thermal destruction for lines, transformers busbars and breakers in the network, taking into account the tripping behavior of the network protection in the Protection mode
• Destroyed network elements are determined and displayed in the result view and in the network graphic
• Detailed view for each network element with listing of all fault locations where a fault leads to the destruction of the element
• Detailed view for each network element with listing of all fault locations where a fault leads to the destruction of the element
• Determination of measures regarding network protection, e.g. the adjustment of protection settings or protection concepts, and validation of these with the thermal destruction analysis
•  Determination of measures regarding network expansion, e.g. network reinforcements within the scope of target grid planning, and validation of these with thermal destruction analysis
• Thermal destruction analysis with very little time effort due to automated check for thermal destruction of equipment for fault events throughout the network

The quasi-dynamic observation over short and medium-term time periods (from several hours, days to several years) is relevant in addition to the observation of the steady-state behavior of the network at individually selected points in time (operating points). The behavior of the network must be analyzed according to time series in order to not only observe individual predefined operating conditions, but also the behavior of the system over the observed period.

• Power flow calculations considering historical measurement data, forecast data, profiles for generation and consumption (standard load profiles), switching states and the actuating values and effects of various regulating devices
• Quasi-dynamic calculation based on individual power flow calculations
• Analysis of the simultaneity of supply and consumption
• Maximum value determination over the entire time period
• Use of calculation values (in kWh) from customer and calculation data
• Loss analysis over period
• Parameterization and optimization of controllable network elements (e.g. capacitors, reactors, transformers, converters)
• Validated network model based on measurement results
• Determination of generation and consumption costs based on cost profiles

The module for time series and operating point calculation (LP) in PSS®SINCAL enables the simulation of a network in user-defined time periods and resolutions as well as the calculation of operating points based on the extensive methods for modeling and calculating a power flow.

• Operating point calculation for symmetrical and asymmetrical networks
• Time series calculation for symmetrical and asymmetrical networks
• Full integration of the controlled elements simulated for the power flow and user-defined models in the quasi-dynamic calculation
• Total or user-specified range of results for each network element at each point in time
• Visualization of the equipment utilizations over the entire period

In addition to the observation the network with the loads and generating plants at the actual point in time, it is necessary to observe further points in time in medium and long-term periods (years). For this purpose, the necessary measures for the expansion, restructuring or deconstruction of the network, which result from changes in loads, commissioning and decommissioning or exchange of equipment are to be derived.

• Target network planning for medium to long term periods
• Network calculations considering the predicted growth or decrease rates of loads depending on the network area as well as already known data for the commissioning and decommissioning of equipment
• Power consumption and operating points of power plants or renewable generating plants that change over time (e.g. repowering)
• Evaluation of the guaranteed power capacity for network areas for different scenarios of load increase in the supply areas
• Identification of weak points in the network and prioritization of network expansion and restructuring measures as well as determination of economic savings potential

The module (LD) in PSS®SINCAL, based on the extensive methods for modeling and calculating power flow, allows the calculation of a network at selected times in the medium- or long-term period which is considered for the target network planning.

• Extensive options for modeling increase, consumption, and increments of load power as well as the times for commissioning and decommissioning of network elements
• Calculation of the power flow at all (automatically determined) times in the calculation period at which increase, decrease, commissioning ,and decommissioning occurs in one single calculation run
• Results at the individual points in time and over the entire time period of the evaluation

To increase the accuracy of the modeling of loads and DERs in the network model, measured values at individual points in time or time periods can be used. By adjusting the modeled values for loads and decentral energy resources (DER) in relation to the measured values, statements about (subordinate) network areas for which no measured values are available should also be made.

• Determination of input data for loads as well as power flow calculations considering measured data or forecast data to refine the modeling of loads and DERs
• Determination of operating points of not measured/forecasted loads or DERs based on selected feeder measurements and metering devices
• Use of maximum or minimum measured values (e.g. from maximum trailing pointer values at the feeder hat) or time series measurements (e.g. feeder measurement with 15 min resolution)
• Optimal utilization of the network capacity based on the measured time series and profiles instead of design for individual operating points
• Validation of load modeling and network model based on measurements

The optimized setting of the position of the regulators of transformers of medium and low voltage substations must be based on measured or calculated values for nodes.

• Determination of optimal tap positions of the transformers to maintain the permissible voltage band in the subordinate network

The module for load trimming and determination of optimum transformer tap positions (LA) in PSS®SINCAL makes it possible to scale and trim load input data. Trimming can also be used to determine an optimized transformer tap position based on the minimum and maximum voltage values.

• Adaptation of the input data (or factors) of the load elements by scaling or by trimming during the power flow calculation until the minimum or maximum measured values are reached

• Determination of occurred or predicted load or supply states of the network based on measured values

• Separate consideration of loads and decentral energy resources (DER) in the trimming 

• Full integration of the functions for calling the scaling or trimming in the time series calculation (LP module)

• Determination of the position of the regulators of transformers to comply with the specified minimum and maximum voltage limit value as well as visualization of the positions in the network graphic

PSS®SINCAL Load Flow Optimization (OL) is a module for evaluating and enhancing network structures and loads. It is used for network operating maintenance and in network planning. The method alters network variables within a defined control range to minimize active power losses. This lets the user evaluate the networks and work out network variations to ensure cost-effective network planning.

The module determines network conditions with the fewest possible transmission losses and the smallest number of violated technical limits. This reduces the voltage variance at the network nodes.

The system variables in this case are generator voltages, generator reactive powers and the transformation ratios of the transformers. Observed limits are the loading of plant and equipment, the voltage range and the P/Q diagram allowed for the generators.

Two different algorithms are offered to solve the problem:

 Indirect gradient method

• Optimization with an indirect gradient method with an external penalty function
• Determination of a set of permissible solutions and then selection of the optimum
• Problem classification after network model creation as problem to minimize a specific non-linear function (objective function or cost function)
• Recovery of predefined technical limits for network elements as non-linear secondary conditions either as an equation or an inequation

Generic method

• Based on the „Ant“-Algorithm as kind of swarm intelligence with meta-heuristic optimization
• Accuracy control by defining the number/level of generations
• Result independent from the starting condition

Measures based on technical studies and calculations for the expansion, restructuring or deconstruction of the network should also be evaluated from an economic point of view. This observation is carried out in medium and long-term periods (years) within the planning horizon.

• Calculation and comparison of the expenditure and costs of planned variants for the expansion and restructuring of the network
• Assessment of capital expenditures and operating expenditures (CAPEX and OPEX)
• Calculation and assessment of the economic efficiency of a planned measure using the capital value method (also called NPV net present value method calculation)
• Support for investment decisions and the determination of a suitable time (delay or bringing forward of measures)

The module (CC) in PSS®SINCAL enables an economic efficiency assessment of technical measures and variants for a selected development period of the network and supports the operator in the preparation and selection of measures under economic aspects.

• Additional modeling dimension for one-off expenses for establishment and shutdown and the operating costs of network elements
• Calculation of investment expenditure and costs using the net present value method (with or without discounting) for each year of the period observed and for the whole period
• Optional integration of the economic calculation with loss and generation or consumption costs resulting from power flow calculations 

The operation of asynchronous machines in industrial, power plant or distribution networks requires their design for parallel and sequential starting. The sizing must be carried out with regard to the network load, the motors themselves and the protection behavior. Among other things, the following must be analyzed:

• Assessment of the ability of one or more motors to start up against given load torque characteristics and determination of start-up times
• Calculation of the voltage drop and the network load for single and parallel motor start-ups
• Determination of sequential start-up times of several asynchronous machines
• Determination of the steady-state operating points

Based on the quasi-dynamic power flow calculation, PSS®SINCAL offers with the motor start-up module (MA) an effective tool for the evaluation of simultaneous or any sequential motor start-ups and the associated network loads. The motor characteristics are basically compared with the load characteristics, considering the electrical properties.

• Simultaneous or successive sequences of start-ups of any number of asynchronous machines
• Use of customizable characteristic curves for torque and start-up current
• Use of standard characteristics according to NEMA
• Constant and switchable star/delta connection of the stator windings for motor start-up

The individual placement of faults is required for simultaneous fault observations at several points in the network (e.g. to analyze the voltage rise in the event of two separate simultaneous line-to-earth short circuits) as well as faults or interruptions along lines.

• Calculation of faults and line interruptions occurring simultaneously or in short succession at several locations
• Placement of fault observations at nodes or at different positions (fault locations) along a line
• Individual simulation of occurring faults (e.g. two separate simultaneous line-to-earth short circuits as well as 3- and 1-phase auto-reclosure)
• Repeated calculation of identical fault configurations
• Using the results as a basis for setting protection

The multiple fault calculation (MF) module in PSS®SINCAL allows you to combine individually defined fault observations into multiple faults, calculate them simultaneously and observe their effects.

• Any user-definable fault locations on busbars and lines for short circuit with or without line-to-earth connection and line interruptions
• Any combination of the individual fault observations (and fault types) as fault packages and simultaneous calculation of the occurring fault events
• Switch between the results of the calculation of different fault combinations (fault events)

Time-stamped data in power systems and pipe networks can have its origin in measurements, forecasts, dispatches or can be derived from planned and unplanned events during operation like switching. These values can cover either past, current, or future periods. The integration of this data into the power system or pipe network simulation as input data, state or boundary conditions is addressing the following use cases: 

• Leveraging the asset investment in metering devices / smart meters and the available infeed data from DERs/IBRs for network and operational planning, (strategic) asset management and grid development strategy 

• Strategic decision making for placement of additional measurement devices 

• Integration of time series data (measured, forecasted, or scheduled values) for network and operational planning 

• Measured or estimated values: Post-operational analysis of power system or pipe network to validate planning assumptions (for example coincidence) and derive critical or typical points in time as new planning reference scenarios 

• Forecasted and scheduled values: Pre-operational analysis of power system or pipe network and starting point for model-based scenario evaluation and operational planning 

• More accurate planning assumptions (data driven derivation, locally with respect to real operation) than estimations or rough planning assumptions with high security reserves 

• Gaining insight on the real utilization and voltage or pressure distribution over time and the residual flexibility of installed assets to minimize future asset invest 

• Localize, optimize, and derive planning and operation imperatives based on simulated losses to reduce them strategically and identify potential locations causing non-technical losses  

• Leveraging measurements as basis for application of extended methods (for example scaled power assignment in power systems) to obtain “virtual” measurement points for planning and operational planning use cases  

• Enablement of network model validation and calibration (impedance or topology) 

The time series data interface (TSDI) module of PSS®SINCAL offers an interface to an open generic time series database for all calculation methods based on time stamps or snapshots.

• Generic open time series database for the TSDI as target for data aggregation and pulling services from different data sources like MDM, SCADA or forecast databases

• Integration of time-stamped active power, reactive power, voltage, or status data and measured, or forecasted feeder currents for power system network models

• Integration of time-stamped consumed or infeed volume, pressure, and status data for pipe network models

• Pre-processing and substitution rules for invalid or bad-quality classified data before insertion into the calculation or simulation

• Full and flexible integration into existing workflows and modules

The aim of the contingency analysis is to evaluate the operational security in the event of malfunction of equipment and network feeders. The contingency analysis provides the network operator with information about the operational security and reliability of the network. The aim is not only to evaluate the malfunction itself, but also to analyze possible strategies for the resupply of all consumers. The network operator needs information regarding:

• Supply interruptions and ways of removing them rapidly
• Detection of impermissible network conditions (voltage deviations, overloads) in the event of equipment malfunction
•  Checking the (n-1)/(n-x) or (n-1-1)/(n-x-y) criteria in the network
• Checking the network during planned maintenance work/shutdown of individual or several devices
• Checking of predefined malfunction scenarios with remedial measures
• Evaluation of the priority of network development measures regarding the (n-1) security and the resupply possibilities of the network

The contingency analysis and resupply (CA) module in PSS®SINCAL automatically simulate the malfunction of equipment in the network and evaluates the network status during these malfunctions.

• Automatic (with conditions) generation of malfunctions of lines, transformers, generating plants, network nodes and user-defined malfunction groups according to user specifications for the n-1 case
• Automatic generation of malfunctions depending on predefined utilization limits of equipment and based on probabilistic parameters
• Simulation of the (n-1-1) case or of caused malfunctions due to the changed utilization of equipment in the (n-1) case
• Comprehensive and interactive visualization of malfunctioned and non-supplied network elements, limit violations and maximum loading
• Display of all calculated malfunctions in the result browser for analysis, recalculation and filtering of malfunctions

Remedial measures can also be analyzed in the contingency analysis if required. If network elements have malfunctions, an attempt is made to resupply all supplied consumers (loads, asynchronous machines, etc.) in a valid operating state.

• Automated resupply through switching measures, load shedding and load reduction
• Support of topological and feeder-based resupply strategies with user-defined settings
• User-defined remedial measures as scenarios, by which for example complete RAS (Remedial Action Scheme) can be simulated

The aim of the probabilistic reliability analysis is to draw conclusions about the future occurrence of supply interruptions based on failures observed in network operation in the past. For this purpose, the indices of supply reliability of the entire network under observation or of individual customers are calculated from the operating behavior of the components and their interaction in the network based on failure models.

• Determination of the supply reliability considering the statistical relevance of equipment failures in contrast to the classical application of the deterministic (n-1) criterion
• Quantitative comparison of system or network concepts that do not differ according to the (n-1) criterion
• Determination of reliability indices for load nodes, network areas or the entire network as well as contributions from equipment
• Analysis and derivation of measures to increase the reliability of supply

The probabilistic reliability analysis (ZU) in PSS®SINCAL is a significant extension of the contingency analysis and resupply (CA) module and enables the calculation of reliability indicators based on the topological and electrical network model, probabilistic failure models and operating behavior of components as well as restoration of supply measures in case of supply interruptions

• Detailed and quantitative description of supply reliability in the observed network area
• Identification of the contributions of individual components to the reliability level and analysis of weak points in the network
• Calculation of reliability indices per network node
  to which load elements are connected (“consumer indices”), as well as reliability indices for the entire network (“network indices”) such as the interruption frequency, average interruption duration and the product of both indices, unavailability of supply per network customer and year

In order to analyze the integration of decentral energy resources (e.g. photovoltaic, wind power plant, combined heat and power plant), as well as different load types (e.g. charging infrastructure for electromobility, heat pumps, Power2Heat, Power2Gas) into distribution networks, an approach is required to determine the absorption capacity of the respective current network state. The analysis should not only include the power flow, but also short circuit and protection analyses. Based on these analyses, it is possible for the network operator to proactively control the integration of loads and generation systems by regularly publishing the results.

• Quantitative analysis of selected network areas regarding their maximum capacity of additional connected active power of decentral energy resources (DER) or loads
• Fast and automated procedure that can be used for re-analysis after any change in network state or topology
• Determination of the hosting capacity based on individual operating points or on historical or forecast time series (profiles) up to several years
• Prevention or postponement of network expansion and reinforcement measures through optimal use of existing capacity

The module for determining the maximum hosting capacity (ICA) in PSS®SINCAL automatically determines the largest power value of a decentral energy resources (DER) or load that can be connected to any node of a network area to be analyzed without violating technical limitations. The user is guided step by step through the setting and execution of the calculation.

• Determine the maximum connectable power at the nodes for which the user-defined criteria are met
• Integration of the individual work steps in an efficient, specified workflow with a separate screen form without additional modeling effort in the network model
• Automatic, combined calculation of a large number of power flow and short circuit calculations as well as protection simulations in the analysis sequence

The integration of the charge infrastructure for electromobility or decentral energy resources (DER) leads impacts mainly the distribution networks.

Since these loads or feed-ins vary both in terms of location and time, the planning cannot work with predefined locations and times for the expansion of the charging infrastructure (and comparable elements to be modeled, such as heat pumps) or decentral energy resources (DER). A stochastic approach is required for a random distribution of the planned consumers or power generation systems in the supply area and the subsequent calculation and network analysis.

• Checking of the utilization (loading) of equipment due to the additional charging infrastructure/decentral energy resources (DER)
• Checking of the permissible deviations of the network voltage due to the additional charging infrastructure/ decentralized power generation systems (DER)
• Provision or inclusion of the required power by the local substation
• Determination of the critical penetration of the supply area in a medium to long-term planning period
• Identification of weak points in the network for planning the network expansion or reinforcement

The module for performing a network stress test (NST) in PSS®SINCAL allows you to analyze the effects of increasing integration of loads and decentral energy resources (DER) in the supply area.

• Analysis of the absorption capacity of supply areas for load elements/decentral energy resources (DER) in a probabilistic bottom-up approach by random distribution of the elements
• Classification of possible connection points and the loads/Converters to be connected by means of types
• Calculation of a user-defined number of loops and thus a random configuration in each loop
• Variation (increase) in network penetration over the analyzed period
• Interactive evaluation and documentation of critical configurations in relation to limit values for voltage and utilization (loading)

The increasing number of decentral energy resources (DER) may require an expansion or reinforcement of the network. Critical voltages or utilizations only arise at individual times or periods of the short and medium term since the supply of these systems may vary considerably over time. An alternative to expanding the network can therefore be the use of energy storage facilities (e.g. batteries, pumped storage power plants) to balance load and generation peaks.

• Prevention or flexible postponement of expansion measures in the network through the targeted local use of (mobile) storage systems
• Design of the rated power and the capacity of a storage system and selection of a suitable connection point (installation location) in the network in the network planning process
• Analysis of different control strategies and types of charge and discharge management of a storage system regarding voltage quality and equipment utilization
• Increase of the capacity for feed-in or load in a network area by using storage systems
• Calculation and design based on historical or predicted time series of load and generation systems

The module for the energy storage placement (ES) in PSS®SINCAL enables the design and placement of storage systems in the network with a two-stage interactive concept.

• Analysis of the placement of a storage element at selected nodes that represent possible connection points
• Two-stage process for determining an optimum connection point for storage systems, considering voltage and utilization criteria. Based on this, a calculation of the required memory states and capacity for (user-defined) storage models
• Integration of the individual work steps in an efficient, structured workflow with its own setting screen form without additional modeling effort in the network model

The integration of decentral energy resources (e.g. photovoltaic systems, wind turbines, combined heat and power plants) into distribution networks is particularly occurring on medium and low voltage network levels. In the planning phase, many countries require that the connection conditions of these systems must be verified during the design phase based on procedures and criteria defined in national standards and guidelines. The large number of (often parallel) requests to a network operator requires their careful but rapid processing and documentation.

• Implementation of a standardized procedure for checking specified limit values for the deviations of voltage, short-circuit behavior and the emission of harmonic voltages (connection assessment)
• Automatic processing of the assessment in order to process a large number of requests in a short time
• Documentation and securing of the results of the connection check for technical and legal discussions

The verifying of the connection conditions as a module (EEG) in PSS®SINCAL offers a separate screen form for the individual steps of a connection check by the network operator. The user is guided step-by-step through the data input of the DER system, the selection of the process and analysis area and the definition of the respective limit values as well as the execution of the calculation and evaluation of the results.

• Integration of the individual work steps in an efficient, specified workflow with its own screen form without additional modeling effort in the network model
• Summary of the calculations required for the check (power flow, short circuit and optional harmonics)
• Default values according to the limit values of the standards and guidelines as well as option for adjustment of the values by the user
• Automatic evaluation of the calculation results against the limit values and documentation

The purpose of this optimization in the module Optimal Network Structures (ON) in PSS®SINCAL is the determination of the best possible structure for medium-voltage networks. The optimization is based on a station-and-route model defining possible connections between infeed and loads. The conventional operating forms of loops and feeders serve as the basis for structure optimization.

The optimization of Greenfield developments or existing networks can be carried out. The optimization has the objective to minimize losses while complying with technical limits (max. feeder load, max. voltage drop, etc.). The costs of transforming the network into the proposed structure are determined.

• Three optimization methods: Rotating radial feeder, Best savings, Best neighbor
• The first static optimization loop determines the target network solution.
• In a second loop, the dynamic optimization calculates the optimal network development sequence for the transformation from the initial into the target network at minimum cost.

In meshed networks, the module optimal branching (OT) in PSS®SINCAL can be used for calculating the positions of the optimal tie open points and for applying them to the network configuration at the press of a button.

It enables the network to be split into a radial network structure with minimum system losses. For this method, the load-flow calculation is used to determine the point of minimum voltage. Then the circuit is opened at the side of the loop with the minimum current. This is continued until the selected network area is unmeshed. Topological changes are taken into account at each new calculation step.

This method is well suited for the identification of the optimal open points separating network areas supplied by different transformers.

• Determination of the radial network structure with lowest losses
• Applicable among different network levels
• Defining network areas where no open point changes should be proposed
• Automatic application of open point (switch position) changes into the network model
• Color-coding of open points, feeders and supply areas in the network graphic

The optimized utilization of reactive power compensation has a positive effect on network operation. Typical advantages are:

• Reduction in transported apparent power and loading of network components
• Reduction in system losses
• Improved voltage profile and mitigation of voltage limit violations
• Postponement of otherwise required network reinforcements
• Reduction of costs of reactive power consumption

The module compensation optimization (CO) in PSS®SINCAL offers methods for the optimized usage and placement of reactive power compensation equipment.

Reactive power optimization

A series of load-flow calculations for the entire network determines the required reactive power. In each individual load-flow calculation, a fraction of the reactive power requirement at the transformers is compensated. The reactive power requirement can be inductive or capacitive. The calculation of the reactive power requirement is carried out for selected voltage levels. In the graphical network diagram, shunt reactor or capacitor symbols are depicted at the lower voltage side terminals of transformers for network areas where reactive power is needed to achieve a specified power factor. PSS®SINCAL can also propose standard ratings based on types specified in the equipment data base.

All relevant power flow results (such as the required reactive power, reduction in losses, etc.) can be displayed.

Automatic capacitor placement

This optimization method has the objective to reduce network losses by placing capacitors in the network. PSS®SINCAL can identify optimum locations for capacitor installation offsetting the costs for capacitors and expected savings from reduced losses. Based on costs and savings the return on investment is calculated.

With the module Volt/Var Optimization (VVO)of PSS®SINCAL the voltage and the power factor can be controlled in radial medium- and low-voltage feeders, which can be symmetrical or asymmetrical, with the result that all consumer nodes are located in the defined voltage range and that the transferred reactive power is as low as possible.

The optimization of the voltage is required to ensure acceptable network operation on the basis of the prescribed limits for all consumers at the feeder.

The optimization of the power factor reduces the transfer of reactive power (and hence the losses) at the feeder. The power factor decreases with the number of inductive consumers (the cable capacities reduce this effect slightly).

The aim of Volt/Var optimization is to determine at which point of the feeder capacitors should be installed and how the transformer must be set at the beginning of the feeder. The number and the size of these capacitors are automatically determined by the software. This will ensure that the consumer nodes of the feeder are within the permissible range under high load and under low load.

The module Load Balancing (LB) in PSS®SINCAL can be used in asymmetrical networks to optimize the connection of single- and two-phase connected loads with the objective to achieve a balanced system state. Complete feeders can be re-linked as a whole.

Load balancing is a combinatorial problem which is solved by using a genetic optimization algorithm that varies the combinations of the connected phases of single phase (L1-G, L2-G, L3-G) and two-phase (L1-L2, L2-L3, L3-L1) connected loads.

The result of the optimization is the system configuration that results in the lowest system unbalance factor of all analyzed combinations.

The result dialog lists the existing and newly proposed phase connections for loads where changes in phase connection would achieve a more balanced power flow in the network. The result can be reviewed in the result dialog window where changes of the connected phases can be applied to the network for selected loads.

When working with multiple users or teams on complex network models, certain requirements must be fulfilled in order to manage a common network model to track the changes of individual users and keep the network model consistent.

• Mapping of corporate processes with different roles and their access rights to a network model for modelling and release
• Consistent network model for synchronization (and possibly also reduction) of work steps (e.g. to support project management)
• Central storage of the network model on a network server as a repository for the individual users
• Update or reset to a previous state of the central network model based on changes made by individual users by version control
• Tracking and documentation of changes

The module Multi-User Master Database (PM) in PSS®SINCAL enables you to work on a network model that is synchronized and distributed across different locations and workstations.

• Creation of a central network model in a master database on one server (repository) from a previously locally existing network model
• User management for the administration of different user roles with appropriate access rights
• Connection of decentralized users (clients) to the master database, local editing and subsequent publication of the changes made
• Central administration (version control) of the master database by an administrator with functions for synchronization and conflict management in a graphical interface

The modeling of networks is based on the output data set for a basic model, which is obtained by conversion or an import from external data sources (e.g. SCADA, GIS) or another network data set (e.g. CIM). If this initial data set changes, a new conversion or import is necessary to update the base model. At the same time, however, extensions to the model (e.g. loads, protection data, models and parameters) that have been made in PSS®SINCAL in the meantime should be retained.

• Updating a network model based on changes in the output data set without losing the additional elements modeled in PSS®SINCAL
• Separate processing of models and their regular merging into a new basic model after processing
• Incremental update based on the changed, added or removed elements of the other data source
• Avoidance of time-consuming, manual synchronization of network models

The Model Merge module (MERGE) in PSS®SINCAL enables two network models to be merged with minimal user intervention.

• Performant and automatic merging of two network models with conflict handling
• Maintaining the consistency of the simulation model
• Individual configuration of the process and marking of changes in the network graphic

The consideration of interactions between the users own and neighboring network areas, i.e. the area of observation and the influencing conditions, may for cooperative collaboration be subject to restrictions regarding data protection and computing capacity. While on the on hand this particularly involves the protection of information of critical infrastructure or intellectual property, on the other hand it involves the optimization of the model by reducing it regarding a specific purpose of analysis. In both cases, the aim is to obtain the same behavior in a reduced model at the defined boundary nodes as in the complete model:

• Reduction of defined network areas in the network model to equivalent partial models
• Enabling the transfer of reduced network data to third parties with defined boundary nodes
• Identical behavior of reduced and complete network model at the boundary nodes regarding power flow calculation and short circuit data (3-, 2- and 1-phase)
• Reduction of the network model to save computing capacity for applications such as real-time simulation

Based on the basic module for load flow calculation, the PSS®SINCAL Platform offers the network reduction (NR) module, an effective tool for reducing definable areas in network models. The network area is selected graphically, by network element groups or other selection criteria. As a result, the equivalent elements are implemented directly in the users network model or optionally in an additional include network model.

• Static reduction method based on the Ward and Extended Ward method
• Consideration of power flow calculation and short circuit data as reference
• Use of boundary injections and equivalent branches at and between the boundary nodes, for the reduction of the network area in line with the results
• Simple selection of the reduction area by polygons, network element groups or a reduction file

Analytical studies of system behavior, which depend on accurate modeling of overhead lines and cables, require the corresponding input data in the form of complex equivalent circuit diagrams and frequency-dependent elements. The planning and operating process provides the user with the information in the physical characteristic values of the conductors, insulators and insulation materials, as well as the geometric arrangement. It is necessary to convert the physics into an electrical equivalent circuit diagram for the different calculation types of the PSS®SINCAL Platform.

• Determination of parameters for single- and multi-phase systems with or without ground return from the geometric arrangement and material characteristics (conductors, insulation, shield etc.)
• Modeling of parallel systems and their mutual interaction through couplings
• Individual consideration of cable structure and arrangement with conductors, shields and armoring

The calculation of electrical parameters of overhead lines and cables (LEIKA) from geometrical arrangements and material characteristic values is made possible by the PSS®SINCAL Platform. The determined parameters serve as input data for power flow, short circuit, influence calculation and other calculation methods.

• Consideration of any arrangement and types of conductors and single cables
• Overhead lines are calculated with any number of parallel systems of different voltages and any number of ground cables
• Calculation of cables with concentric shields or metal sheaths or armor, additional common sheaths around a three-phase system and parallel ground conductors
• Line and cable characteristic values can be calculated at operating frequency and at higher frequencies up to several kHz
• Output of coupling data for PSS®SINCAL and for the expert mode (Exp Mod) in PSS®NETOMAC

An intuitive and efficient model editor is required if user-defined models of equipment, control devices or simulation controls are to be used, for which the behavior cannot be simulated by the standard models in the delivered model library.

• Possibility of modeling for user-defined models for control devices in generating and transmission systems for different calculation types as well as individual influencing of load and branch element behavior depending on various variables and network signals
• Pre-defined functions and block diagram for the simulation of controlling devices with the option to implement your own code
• Simplified integration of external DLLs that contain vendor-specific algorithms and model behavior
• Encryption of models to protect intellectual property
• Use of created dynamic models in different products of the PSS®Suite

The graphical model builder (GMB) in the PSS®SINCAL Platform contains an intuitive user interface for user-defined modeling. The block oriented GMB is fully integrated in the native GUI of the PSS®NETOMAC dynamics engine and can be used in all simulation programs of the PSS®Suite via a provided interface without compilation or other third party software.

• Intuitive operating and modeling concept as well as automatic plausibility check during modeling
• More than 30 different model types for generation and transmission systems as well as for controlling individual network elements and simulation
• Creation of user-defined models for use in different calculation types
• Over 100 predefined function blocks and the possibility of implementing user-defined code in a FORTRAN syntax
• Pre-defined templates for typical block diagram and option to create user-defined template library
• Connection of external DLLs (DLL module) as subsystems of a model
• Output of selected signals during the runtime of the model in predefined file structure
• Test environment for the created models with analysis possibility directly in the block diagram of the model as well as in diagrams
• Possibility of model encryption

When creating and maintaining user-defined models of equipment, control devices or simulation controls in the model builder (GMB module), the integration of program parts and blocks developed as DLLs as subsystems is also useful in order to address the following requirements:

• Functional extension of models with complex data types and structures as well as functions that are not natively available in GMB
• Development, use and distribution of user-defined function blocks in C, C++ or other programming languages
• Coupling of internal input or output signals of the controllers with other applications running in parallel (if necessary, synchronously)
• Protection of intellectual property in the form of subsystem design or implementation
• Standardized interface for the use of subsystems in different software environments
• Development and testing of control functions in a "Software in the Loop (SiL)" environment

The two interfaces of the DLL model interface (DLL) module, as part of the PSS®NETOMAC dynamics engine, extend the simulation of models created with the graphical model builder (GMB) by integrating user-defined subsystems as a dynamic link library (DLL).

• Integration of external, already compiled DLLs as model subsystems in models created with the GMB
• IEC DLL interface, standardized to IEC 61400-27-1 F
• EXTERN DLL interface of the PSS®SINCAL Platform with simplified definition
• Use of the interface in the LF, LP, ST, EMT calculation methods

To analyze the dynamic behavior of electrical power systems, standard models are defined by different standardization committees (IEC, VDE, IEEE etc.), which must be treated uniformly in different simulation programs and can be individualized only by changing parameters. While the classical standardization of dynamic models primarily addresses control devices for conventional generation units, type 2 generation units are gaining in importance and require the consideration of their models in dynamic simulation.

The PSS®SINCAL Platform contains a library of dynamic models (DML) for different network elements and calculation types that can be connected to the respective network model by the user.

The following dynamic models are included in the global library of the platform:

• Inherent models, which are used by default in PSS®SINCAL in the absence of user-defined dynamic models on the network elements, to simulate the basic dynamics of the network elements
• Generic models for representation of dynamic behavior of loads, general shunt and serial branches and distributed generation plants. These can be used both as the equivalent of the complex behavior and as a starting point for the creation of user-defined, dynamic models: Variable power (GNE-P/Q),  Variable shunt admittance (GNE-Y),  Variable serial admittance (GNE-Y4), Current injection (GNE-I), Voltage injection (GNE-V)
• Models of machine control devices: (1) according to the IEEE, IEC (CIM CGMES) standards, the PSS®E definition and other specifications, (2) Excitation systems, compensators, limiters, power system stabilizer, speed/power governors
• Generic inverter-based models: Distributed energy resources according to WECC, EPRI (e.g. DER_A, PVD1, BESS)

The following dynamic models are contained in the user library in the Documents folder of the user:

• Flexible AC transmission systems (FACTS) models for power flow and stability calculations: Static var compensator (SVC), STATCOM (SVC Plus), Mechanically switched capacitors (MSC), Thyristor controlled series capacitor (TCSC)
• Simple three-phase photovoltaic model
• Dynamic models of wind turbines with different generator concepts: Asynchronous machine with squirrel-cage rotor (SCIG), Doubly fed asynchronous machine (DFIG),    Synchronous machine with full converter (FCSG)

In power systems, the interaction of all components from generation, transmission and conversion systems is complex, not only in case of fault events. Generators, control devices, HVDCs, FACTS, distributed energy resources and loads interact with each other even in a quasi-steady state, which manifests itself, for example, in the high-energy dominant electromechanical modes and jeopardizes system stability, e.g. through disconnections.

The complexity of the systems is constantly increasing due to digitalization and structural and market-related developments. This situation requires innovative methods that can systematically assess the stability of such systems and support the derivation of effective countermeasures.

If the dynamics of the network are shifted to the network levels subordinate to the transmission network, the complexity of the requirements to the operators of such systems increases.

• Systematic analysis of the small-signal stability of electrical energy systems with a focus on electromechanical modes and interactions with control devices of equipment
• Fast identification of local (local), regional (intra-area) and global (inter-area) electromechanical modes and controller interactions
• Support in the identification of suitable and efficient countermeasures for weakly damped, low-frequency oscillations

The PSS®SINCAL Platform, with its dynamics engine PSS®NETOMAC, offers the user in this module (EVA) the innovative modal analysis that meets the above-mentioned technical requirements and enables the evaluation of the interaction of all components with the focus on electromechanical modes and controller interactions. In addition to the dynamic models of stability calculation, the engine uses efficient methods for the complete description of the inherent oscillation behavior of an electrical power system.

• Quick and easy identification of weakly damped, dominant modes in the electrical power system and their influencing variables that can jeopardize the stability of the system regarding voltages and synchronism
• Determination of the eigenvalue solution of an entire dynamic network model with machines, controllers, transmission systems as well as loads and thus the inherent electromechanical and controller-induced oscillation capability of a system for a given steady-state case
• Option for simplified eigenvalue screening based on signal excitation and evaluation in the time domain for very large network models

The use of series compensation in order to increase transmission capacity and to stabilize grid operation can lead to the phenomenon of subsynchronous resonances (SSR) with drive shafts of conventional generating plants and thus can lead to damage of shafts and protection tripping. Converter-based technologies can also lead to subsynchronous interactions (SSTI) with the drive shafts. These dangers must be assessed already in the planning phase of such systems, but also when the resonances are detected during operation, and necessary countermeasures must be taken in order to avoid damages and fatigue.

• Assessment of the inherent tendency of drive shafts with several turbine stages, machines and excitation systems to oscillate, which can be excited by series compensation and converter-based technologies (HVDC, FACTS etc.)
• Evaluation of the mechanical stresses on drive shafts in power plants in case of faults
• Assessment of life expectation of drive shafts under regular stress due to torsional oscillations
• Analysis of the electromagnetic compensation processes associated with the resonances occurring and their effects

Based on the transient engine PSS®NETOMAC, the expert mode in this module (TOR) allows the extension of the models of the machines by the definition of the drive shaft in order to consider the influence of turbine stages and excitation system in the mechanical part of a power plant. On the one hand, this supports the user in the assessment of mechanical stresses on the drive shafts when subsynchronous resonances (SSR) and interactions (SSTI) occur and in the development of appropriate countermeasures when dimensioning and commissioning a plant. On the other hand, it enables the user to evaluate the electromagnetic effects of the compensation processes.

• Use of proven and successfully validated models and simulation methods of the PSS®NETOMAC transient engine
• Support of detailed mass definitions for realistic representation of turbine stages
• Various possibilities for modeling the drive shaft by distributing masses, torques and the Park transformation angle
• Possibility to use torsional data in the active frequency response (FRD module)

When dimensioning equipment in electrical power systems, it is necessary to efficiently determine potential resonance points of the network as well as of the active network elements over a broadly defined frequency range. This makes it possible to prevent possible damage caused by resonances in network operation through passive and active countermeasures.

•  Analysis of the frequency response of passive network elements to determine electrically induced resonance points
• Support in the sizing of filters based on the results of the frequency response determination
•  Consideration of dynamic equipment such as machines, their drive trains, their control devices and controllable network elements in the frequency response
• Consideration of the operating point in the linearized response of the frequency response of a nonlinear system

In addition to the harmonics (OB) module, the expert mode (ExpMode) of the PSS®NETOMAC transient engine allows the passive (ST, EMT modules) and active (EMT module) system behavior in the frequency domain to be analyzed by this module (FRD). It supports the user in the detection of potential resonance points and in the development of appropriate countermeasures in dimensioning and parameterization.

Quick and easy identification of resonance areas of the network

• Use of proven and successfully validated models and simulation methods of the PSS®NETOMAC transient engine, taking the torsion data (TOR module) and used models into account
•  Application of efficient linearization rules for model blocks to determine the frequency response
• Consideration of models for network elements in the passive frequency response
• Support in the sizing of filters to suppress or shift resonance ranges

The analysis of electrical networks requires not only the development of models but also their parameterization. In the complex data collection phase, the user sometimes has access to the information provided by the system manufacturers (nameplate and data sheets). Furthermore, measured values are provided or determined by local measurements, from which the parameters for different types of models must be derived.

• Determination of the equivalent circuit diagram sizes of asynchronous and synchronous machines
• Identification of equipment model parameters based on measured values
• Determination of dynamic equivalent networks
• Reduction of the models of dynamic loads
• Determination of set values of controller parameters in open and closed control loops

When dimensioning components and control devices, their rating and parameterization should also be optimized regarding specified objectives. This requires efficient algorithms for the formulation of optimization targets, secondary conditions and the variables to be changed.

• Optimization of any parameter of the network model or control devices regarding a target function
• Definition of secondary conditions, which are considered in the optimization besides the target function
• Consideration of the optimization functions in different calculations of the time and frequency domain

The optimization algorithms (OPT) of the PSS®NETOMAC dynamics engine are used within the native user interface (ExpMode) both to identify parameters from measured values and to determine optimal settings and dimensioning values in various calculation types based on target functions.

• Identification of the equivalent circuit diagram values of asynchronous machines from basic data and provided torque-speed characteristics as well as the output of the machine definition
• Parameterization of network models and their dynamic equipment as well as control devices from measured values in the time and frequency domain
• Optimization of parameters of network elements, dynamic equipment and models with regard to a target function and secondary conditions in the calculations power flow (PF module), stability (ST module), electromagnetic transients (EMT module), active and passive frequency response (FRD module) and in the eigenvalue calculation EVA module)