## Software modules for electricity network planning

### PSS®SINCAL

## Electrical networks

PSS SINCAL offers a comprehensive range of analysis modules and tools facilitating the planning, design and operation of power systems. Its field of application ranges from short-term to long-term planning tasks, fault analysis, reliability, harmonic response, protection coordination, stability (RMS) and electromagnetic transient (EMT) studies.

PSS SINCAL supports all types of networks from low to the highest voltage levels with balanced and unbalanced network models e.g. four wire systems or transposed systems with the full coupling matrix.

Using the PSS SINCAL program, engineers can simulate future scenarios and thus help avoid costly design errors or misinvestment. It is the ideal tool for simulating smart grids and their effects including linkage to smart meters.

Several analysis modules, such as protection or dynamic simulation, are also ideally suited for training purposes.

## (Unbalanced) load flow calculation

Load flow or power flow calculation is the program module for the analysis and optimization of existing networks. Weak point determination is one of the important tasks in network planning. Different algorithms – i.e. Newton-Raphson, current iteration and others – are available for calculating the distribution of currents, voltages and loads in the network, even under difficult circumstances, e.g. when several infeeds, transformer taps and poor supply voltages are involved.

PSS SINCAL can handle more than one – isolated – network at the same time.

Networks with more than one slack are possible.

The power flow type of each generator or infeed can be set individually, e.g. swing bus (slack), PV, PQ or I type. Controllers with operating points and limits can be modeled. A re-dispatch according to user defined limits or power frequency characteristics is selectable.

Transfer capacity planning through different network areas /groups is possible.

The voltage and power controller can automatically calculate the optimal tap position of transformers or other switched elements like shunts or capacitors based on specified target voltage or power ranges.

Voltage and power regulation at a remote node is possible.

Master and slave controller function for networks with parallel transformers is available.

Different load types can be modeled

Load flow can handle phase shifting transformers and fully unbalanced transformers like center-tapped models.

Load flow already supports voltage and power dependent shedding of loads or generators (e.g. DC elements like photovoltaic panels)

Many other PSS SINCAL modules, such as multiple faults, stability, motor start or protection, use the results of the load flow module as a starting condition.

Starting value determination algorithm

PSSE load flow calculations can be directly started in the PSSSINCAL user interface if PSSE V32 or V33 is installed and licensed on the computer.

Color-coded evaluations of input data and results in the network graphic and filtering of data in the spreadsheet view is possible e.g. for:

Voltage ranges

Node overviews

Network and sub-network losses

Tap settings for transformers

Loading of elements

Voltage profiles

Graphical evaluation can be done, e.g.:

Overloaded system elements

Isolated network parts (without a feeding)

Contour plots of selected results, such as load flows, load densities and short-circuit levels, in the network diagrams with selected results

Customizable annotations

Displaying of selected network regions which are of interest (not every element must have a graphical representation)

Diagrams (e.g. voltage profile) showing the results for selected paths through the network can be created

Unbalanced power flow

In PSS SINCAL balanced network models can be easily transformed into an unbalanced network model by simply specifying the connected phases and entering single- or two-phase connected network elements (loads, generators, transformers, center-tap transformers, lines, etc.).

## Short-circuit calculation

Short-circuit analysis is the method employed for assessing the correct ratings for the network (i.e. the maximum fault currents) and also the correct protection settings (i.e. the minimum fault currents).

Single-phase, two-phase, two-phase-to-ground and three-phase faults can be calculated for individual nodes or whole sub-networks, i.e. it is possible to calculate the short-circuit current distribution in the network for each fault condition. The calculation can be performed in accordance with the standards ANSI C37, IEC 61363-1, VDE 0102, IEC 60909, engineering recommendation G74, and taking into account pre-fault loading. Any possible changes to the standard are incorporated directly and smoothly into the calculation process, since our experts are participating in standards committee meetings. In the case of asymmetrical faults different transformer vector groups are also taken into account, as are the various methods of neutral earthing employed. The short-circuit current rating of bus bars and cables (1-second current) can be checked, too.

Network design and planning tasks for which expected maximum currents are decisive are normally carried out in accordance with the relevant standard. However, if the minimum fault currents need to be determined, the preferred choice is the load flow superposition method, which takes into account the network’s pre-fault loading condition. This is especially the case when the fault current has the same order of magnitude as the load current.

The key values of the short-circuit analysis standards for assessing the fault characteristics (such as Ik“, ip, Ia, Sk“, Uo, Z0/Z1, etc.) and other relevant information are stored in the data base where they are available for further calculations. The calculation reports include fault location-based tables with all contributions and branches viewed together with summaries of results.

IEC 60909/VDE 102

IEC 61363-1

ANSI C37

Engineering Recommendation G74

Short-circuit analysis considering pre-fault loading conditions

Calculation with symmetrical components

Arc impedances can be taken into consideration

Key values are Ik“ ,ip, Ia, Sk“, Uo, Z0/Z1

ip can be calculated optionally according to radial network, meshed network or to the equivalent frequency method

Block generators are implemented according to the standards in two different ways (generator and transformer as two separate elements or combined as one element)

DC equipment like PV or wind is modeled with the correct contribution, different to normal rotating machines, taking into consideration also the possible disconnection according to the connection rules

Neutral grounding

Phase shifts in transformers

Calculation in selected or all voltage levels at the same time

Calculation of all currents in the whole network for a single fault location

Calculation of faults at every node in specified voltage levels simultaneously

Various reports for all nodes, all fault locations all network levels

Color-coded evaluation of network diagrams, e.g. the violation of equipment ratings such as the permissible 1-sec short circuit current rating of lines or bus bars

## Contingency analysis and restoration of supply

The purpose of the contingency analysis software module is to assess the load flow in networks during outages of network components and generators. It provides information on security of supply and weak points in the network. The network operator obtains important information on following issues:

n-1 and n-1-1 criteria compliance

Risk of supply interruptions

Overload conditions due to network component outages

Unfeasible network conditions as a result of network component outages

Priorities of network development measures

Form of contractual agreements with consumers

Contingency analysis comprises a series of load flow calculations. One or more elements are considered on outage in each individual load flow calculation. PSS SINCAL can simulate the outage of a single network component, or a group of components (that have to be operative as a group) and overloaded components. Conditional and unconditional outages as well as base (n-1) and resulting (n-2) outages can be modeled.

All relevant results (minimum and maximum values, unsupplied consumers, overloads, etc.) are recorded. The results can be summarized in a clearly arranged tree structure. For large networks, the evaluation can be limited to the main characteristics in order to be able to deal with large amounts of data and to achieve short calculation times. Detailed load flow results are provided for the analysis of critical cases.

The purpose of the r**estoration of supply** method is to restore the supply of all consumers (loads, asynchronous machines, etc.) to a normal operating state after outage of network components.

At first, PSS SINCAL tries to restore supply primarily by closing switches. If this is not sufficient to restore supply to all consumers then the algorithm tries to transfer loads to other feeders. If even this fails then consumption is reduced or loads are shed. As results different switching options with all performed restoration measures and the not supplied network elements are provided.

## Multiple faults calculation

When multiple faults and interruptions occur in a power system simultaneously at several locations, e.g. in the not-so-rare case of a double earth fault, multiple faults calculation determines the steady-state distribution of current and voltage in the network. The actual switching configuration is taken into account, as is load flow.

Possible fault types at nodes are:

Single-phase fault

Two-phase fault with/without earth

Three-phase fault with/without earth

Additionally, it is possible to place line faults and to vary their location on the line. The following fault and conductor interruption types can be simulated on lines:

Single-phase, two-phase and three-phase interruption

Single-phase interruption and single-phase earth fault

Two-phase interruption and two-phase earth fault

Three-phase interruption and single-phase or three-phase earth fault

Two-phase interruption and two-phase fault

Three-phase interruption and two-phase or three-phase fault

The multiple fault analysis is based on a complete 3-phase system representation (symmetrical components). All specified faults can be combined to different “fault packages” which can be calculated simultaneously. Results can be shown case by case in the network diagram, reports or data base masks.

## Reactive power optimization and capacitor placement

**Reactive power optimization**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 violation

Postponement of otherwise required network reinforcement

Cost of reactive power consumption can be reduced

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 load 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.

## Volt/Var optimization

With this procedure the voltage and the power factor can be controlled in radial medium- and low-voltage feeders, which can be symmetrical or unsymmetrical, 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 it is getting smaller with the number of inductive consumers (the cable capacities reduce this effect slightly).

The aim of the VoltVar optimization is to determine at what point of the feeder a capacitor should be installed and how the transformer must be set at the beginning of the feeder. This will ensure that the consumer nodes of the feeder are within the permissible range under high load and under low load.

## Load balancing

Electrical load balancing can be used in unbalanced networks to optimize the connection of single- and two-phase connected loads with the objective to achieve balanced system loading. Complete feeder could be relinked as a whole.

Load balancing is a combinatorial problem which is solved by PSS SINCAL 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 in PSS SINCAL lists the existing and newly proposed phase connections for loads where changes in phase connection would achieve a more balanced load 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.

## Load allocation, scaling and transformer tap optimization

Load allocation (substation load assignment module) is an enhancement of the load flow calculation software module enabling feeder load scaling. It is used to scale loads in order to determine load flow conditions matching measured currents or apparent power flows. For this purpose, recorded maximum meter readings can be entered at loads and meters placed on lines in the network. The load allocation function scales loads to which meter readings are assigned so that the results of the load flow calculation match the recorded maximum flows at the measurement points. Hence, the application load allocation function can improve the network model and lead to simulation results that are closer to real network conditions.

Tap zone detection is an enhanced load flow simulation method combining load trimming for minimum and maximum load conditions with transformer tap optimization so that the voltage of the regulated feeder remains within the permitted voltage range.

The results are the load flow results for minimum and maximum load conditions. Resulting tap positions can be visualized by means of color-coding in the network graphic. The calculated minimum and maximum voltages can be visualized and compared to the permissible voltage limits in voltage profile diagrams.

## Optimal branching, tie open point optimization

In meshed networks, this method 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 for different network levels

Defining network areas where no open point changes should be proposed.

Automatic transfer and application of open point (switch position) changes.

Color-coding of open points, feeders and supply areas in the network diagram

## Voltage profile, multi-conductor systems

This module handles continuous load flow calculations for investigations of multi-conductor systems, e.g. railway tunnels.

## Optimal load flow

Load flow optimization is an important tool for evaluating and enhancing network structures and loads. It is used for network operating maintenance and in network planning. PSS SINCAL 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 assure cost-effective network planning.

PSS SINCAL 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.

PSS SINCAL supports two different algorithms to solve the problem:

Gradient method

Network optimization is an indirect gradient method with an external penalty function. This method first determines the set of permissible solutions and then selects the best possible solution

Once a network model has been created, then the goal is to minimize a specific non-linear function. This can be either an objective function or a cost function.

PSS SINCAL recreates predefined technical limits for network elements as non-linear secondary conditions. This model can be either an equation or an inequation.Generic method

This method is based on the „Ant“-Algorithm which is a kind of swarm intelligence with meta-heuristic optimization. By defining the number/level of generations the user can control the accuracy. Advantage of this method is that the result is fairly independent from the starting conditions.

## Motor start calculation

Motor startup calculation is an effective tool for the calculation of the operational behavior of the electrical network. It provides answers to questions like:

Will the motor start successfully considering the given load torque?

How large is the voltage dip during the motor start?

What are the operation points of the motors?

How long is the start-up time? Text

What is the network loading during motor start?

With this method, the demand of power during motor start with inclusion of the voltage at the motor terminal can be calculated. This is a dynamic process, which will be solved by the method of homogeneous time steps. For this, a calculation loop over a period of time is defined; and load flow and motor power are determined. Non-linear saturation and star-delta switching is available.

Any number of motors can be started at different times.

Within PSS SINCAL the user can define the functions motor torque, load torque and current as functions of speed in diagrams with quick response to the input data. NEMA models as pre-defined equipment are also supported.

Soft startup can be done by defining

Maximum current

Auto transformer

Capacitor units

Combinations of it

For analyses, the load flow results and the following diagrams are available:

Function of time: active power, reactive power, speed, current, voltage, slip

Function of speed: motor torque, load torque

Motor current in complex plane: Heyland circle

## Power stability analysis (RMS)

Power stability analysis can provide the answer to the question of whether or not the generators can continue in stable operation in the network in the case of faults or interruptions. This stability software module handles both balanced and unbalanced network models with balanced and unbalanced disturbances like fault right through studies.

**Modeling of network and machines**

No limitations in the size of the network and in the number of machines

Network modeling with complex impedances

Fundamental frequency model for simulating electromechanical phenomena

Quasi steady-state values

Differential equations for machines

- short-term (stability) model: Park equations 5th order

- long-term model: Park equation 2nd orderSynchronous machines are built with their direct and quadrature axes:

- Derived data: subtransient, transient and synchronous reactances; time constants

- Original data: physical resistances and reactances (impedances)

**Modeling of controllers**

Differential equations for controllers

PSS SINCAL offers a controller library which contains – among others – the following components:

- IEEE standards

- Excitation systems

- Turbine governors

- Power System Stabilizer (PSS)

- PSS E controller modelsBy the use of a so called “Block-Orientated Simulation Language” (BOSL) it is also possible to include user-definable controller structures.

Manufacturer models can be built for example in MATLAB/SIMULINK or modern programming languages. With an additional standardized header file (see Appendix G in IEC 61400-27) these models can be compiled and linked as a DLL file. Such DLL files can be exchanged between different parties as black-boxes.

**Modeling of fault scenarios**Potential bus bar faults are:

Single-phase fault

Two-phase fault with/without earth

Three-phase fault with/without earth

The following interruptions and faults are possible on conductors:

Single-phase, two-phase and three-phase interruption

Single-phase interruption and single-phase earth fault

Two-phase interruption and two-phase earth fault

Three-phase interruption and single-phase or three-phase earth fault

Two-phase interruption and two-phase fault

Three-phase interruption and two-phase or three-phase fault

In addition, it is also possible to energize or de-energize node elements at specific times.

The user can simulate:

Fault application and removal

Line switching and line reclosing

Disconnection of lines, cables, transformers etc.

Addition and removal of shunts

**Output of results**The program calculates the characteristic data of the machines, such as

Phase currents and voltages

Slip and rotor displacement angle

Excitation current and excitation voltage

Power outputs

Torques

Currents and voltages and powers and impedances for any item of plant and equipment are available, too.

**Diagrams**In diagrams all results call be displayed in a user-defined manner. Diagrams can be arranged in overviews or in separate diagrams.

## Electromagnetic transients (EMT) analysis

Power stability analysis is used for investigations for which the envelope curves of the characteristic values are sufficient results. If the 3-phase reel waveform is needed PSS SINCAL’s electromagnetic transients analysis is used.

Transient stability analysis software allows for networks, machines (park 7th order) and controllers to be modeled by means of differential equations. Symmetrical systems are entered single-phasely and completed to three-phase systems. Asymmetrical systems can be accommodated by means of elements in the individual phases. This is also possible for any kind of DC system. Special equipment (e.g. load models, FACTS elements, controls, etc.) can be user-defined by means of BOSL (Block oriented Simulation Language). Therefore, the EMT module can provide a complete solution of all electromechanical (RMS) and electromagnetic (EMT) phenomena, including asymmetrical and non-linear events. The main field of application is in the design of equipment and apparatus while taking into account transient phenomena.

For instance, typical applications are wind park integration studies, investigations of dynamics of industrial networks and studies of HCDC and FACTS plants.

The results are depicted in diagrams and can be analyzed with the evaluation tool SIGRA or Comtrade viewers.

## Identification and optimization

The data collection at the beginning of a system study is one of the critical and time consuming activities. In many cases the electrical data for simulation models are not available. In special cases only measurements from the system are available. In our software special algorithms can identify parameters of electrical models from measurements. The same algorithms can be used for the optimization of settings of models.

The identification is possible for any model in the frequency range (e.g. controller transfer functions) and in the time domain (transient and stability mode). The identification mode is used for example for the following functions:

Parameterizing of asynchronous machines from torque-speed characteristic considering saturation

Parameterizing of synchronous machines

Establishing of dynamic equivalent networks (active equivalent network)

Reduction of dynamic loads (e.g. equivalent motor groups)

Parameterizing of closed-loop controllers (voltage controllers, turbine controllers)

Parameterizing of cable data and line data from geometry of configurations (constant and frequency-dependent parameters)

The possibility of optimizing can be applied to any element in the system. All modeling possibilities described are permissible so that linear and non-linear problems can be solved. The user defines the target function as evaluation function with any input variables from the network or the control loop. Secondary conditions can be considered as defined by the user. The parameters to be varied can be selected and providing with a starting value and possible upper or lower variation limit. Optimizing is possible in the time and in frequency domain, with load flow and for general mathematical functions that are defined as block oriented structures.

## Eigenvalue screening

Eigenvalue and modal analysis in large electrical power systems can be very time consuming. Also linearized models of the equipment are needed. To get a quick overview of oscillation frequencies, dampings and right locations for damping equipment, the Eigenvalue screening method for stability time domain simulations can be used. This method is much faster in large systems. It can be used as a pre-calculation for the main Eigenvalue and modal analysis. It can also be used for the tuning of stabilizers during the simulation run.

## Eigenvalue / Small signal analysis and modal analysis

In addition to the facility for simulation in the time domain, PSS SINCAL also permits the study of networks, machines, shafts and control systems in the frequency domain. Furthermore the elements of control systems can be analyzed and system behavior can be optimized.

In large-scale electrical systems the relationships between generators, networks and control systems are becoming ever more complex. FACTS elements are used for the fast active control of transmission systems and for filtering purposes in distribution systems. The analysis of such complex interactions between systems and equipment requires modern methods which are able to describe the behavior of the whole system both simply and clearly. PSS SINCAL uses the analysis of system Eigenvalues for this purpose. Compared with traditional methods of simulation, the Eigenvalue or small signal analysis method provides more information about the behavior of the system regarding damping, frequency response, observability, controllability and the effects of system state.

Specific areas of application for Eigenvalue analysis are inter-system oscillation, voltage stability, modeling of dynamic equivalents, controller design, subsynchronous resonance and harmonics effects.

## Dynamic network reduction

Deregulation and privatization in the power industry are significantly changing relations among power generation, transmission and distribution systems. Utilities are faced to be oriented to a competitive market environment to maximize their profits. In this new situation, detailed network data among competitive companies are becoming more and more confidential. Thus, exchanges of the network data among these companies could become difficult. However, with enhanced stability requirements, dynamic behaviors of the interconnected power systems involved need to be carefully studied online and offline. This includes studies such as overall system stability, dynamic security assessment and coordinating system controls in a global manner, etc. All of these studies require knowledge of interconnected neighbor networks. Thus, an issue on the establishment of equivalent networks for a large, multi-owner’s interconnected power system become essential.

On the other hand, in power system analysis, it is also a common practice to represent the parts of a large interconnected power system by some forms of a reduced order equivalent model, e.g., models used for studies on investigating or verifying dynamic behaviors of the system, for fundamental frequency over voltage studies or for AC filter performance calculations, etc. Due to limited size and capacity of tools used for real-time simulation, users are sometimes forced to reduce their net-works to match the size and capacity of the tool used. Furthermore, a reduced model can simplify the network calculation and save the investigation time in some cases. Depending on different applications, equivalent models are established either by a static or a dynamic network reduction process.

After defining the network part which shall be reduced this program module automatically generates a **dynamic equivalent network** part with the same dynamic behavior than the original system. The identification process contains four steps:

Identification of coherent generators by cross-correlation analysis

Equivalent generator for each coherent generator group

Passive network reduction (“load flow reduction”)

Identification of controller parameter for each equivalent generator

Also a normal passive network reduction based on **Ward and Extended Ward i**s available to replace selected network groups by a network equivalent.

## Real-time simulation

One of the important features of the PSS®NETOMAC program is the possibility of simulation in real-time. Our real-time simulation is used for example for:

Closed-loop hardware in-the-loop tests (protection devices, controller, etc.). Additional hardware (DINEMO-II, OMICRON) is needed.

Dynamic Security Assessment (SIGUARD®): Dynamic calculation engine added to SCADA systems.

Dynamic calculation engine in process management systems (e.g. SICAM230, T3000).

## Torsion

In some countries, e.g. USA, Canada, China and Brazil, electrical energy has to be transported over very long transmission lines on account of the long distances between the generating plants and the loads. Series capacitors are used in the transmission lines to improve the transmission capability, the stability of the power system and to compensate for the voltage drops due to the high line inductance.

The presence of the series capacitors in a power system has brought up the phenomena of subsynchronous resonance (SSR). These phenomena originally resulted in the destruction of two generator shafts in the early 1970s. Since then, considerable efforts have been spent to study this phenomena and to find solutions to prevent the damaging effects.

Additional to the electrical system model, where the generators are represented by Park equations and the admittance, are represented by differential equations, the turbine-generator shaft model is also taken into account. The shaft assembly is modeled by n rotating lumped masses which are coupled by n-1 rotating springs. For example: the steam turbine lumped masses are usually representing the major turbine sections such as the high pressure (HP),the intermediate pressure (MP) and the various low pressure turbines (LPA, LPB).

## Harmonic load flow, harmonic frequency scan

The harmonics software module is used for calculating the distribution of harmonics in electrical networks as well as for calculating frequency response. The calculated harmonic currents and voltages in the network can be evaluated by several different methods such as, for example TIF, THFF or EDC.

In addition to the graphical output of frequency responses for the required nodes, the network impedances are also shown in the complex plane and the harmonics level for all nodes and network levels with the appropriate limit values.

The input data must be supplemented with the frequency relationship of the network elements, for the purpose of which three different methods are available. The transmission lines are simulated with wave equations. Simulation of a resonance network is possible with very convenient inputs. Current and voltage infeeds are also allowed for odd-number harmonics anywhere in the network. A variety of different filters are offered.

Three phase harmonic voltage and current distribution (unbalanced harmonic short circuit)

Voltage and current harmonic distortion

Determination of harmonic distortion factors. The calculated harmonic currents and voltages in the network can be evaluated by several different methods such as, for example TIF, THFF or EDC.

For harmonics we also have transformer vector groups. That is why you can calculate the wipe out of the 5 and 7 when you have one transformer YY0 and another turning 30 degrees when you have two 6-pulse bridges.

PSS SINCAL provides you with three different methods for defining the dependency of the network elements from the frequency. They take into consideration the skin and proximity effects.

Resonance network equivalent modeling is available

Lines are modeled by wave equation

Special filter configuration are available

Overloading can be shown as in every other method by coloring the results (and of course by reports).

In addition to the graphical output of frequency responses for the required nodes, the network impedances are also shown on the complex plane and the harmonics level for all nodes and network levels with the appropriate limit values.

Filters can be calculated/designed to the specific demands.

Superposed harmonic distortion is shown in bar charts with the specific (country) standard limits

Diagrams for harmonic response

Diagrams with polar plot of the impedance (R-X plots)

Detailed tabular reports

## Ripple control

The ripple control module calculates the ripple control level and the distribution of the ripple-control currents in the electrical network for serial and parallel signal inputs. The frequency relationship of the elements can be entered for this method, too.

PSS SINCAL reproduces all the active and passive network elements (generators, loads, and lines) as impedances. When doing so, the reactive part of the power must be separated into an inductive part and a capacitive part for compensation. Ripple control transmitters are reproduced as voltage sources or current sources.

This module is used to check the level for the remote switching of e.g. street lamps or electric heating.

## Frequency domain and resonances

In addition to the facility for simulation in the time domain, the dynamic engine also permits the study of networks, machines, shafts and control systems in the frequency domain. As well as allowing the elements of control systems to be analyzed, it also permits the study of networks, protection systems and machines at different frequencies.

## Flicker simulation and analysis

Flicker is a visible change in brightness of a lamp due to rapid fluctuations in the voltage of the power system. The source of this is the voltage drop generated over the source impedance of the grid by the changing load current of an equipment or facility. These fluctuations in time generate flicker. The effects can range from disturbance to epileptic attacks of photosensitive persons. Flicker may also affect sensitive electronic equipment such as television receivers or industrial processes relying on constant electrical power. The requirements of flicker evaluation are defined in standards. Two different standards can be used separately.

## Grid-code compliance - Connection of distributed generation to the grid according to EEG

Beside the usage of separate calculation methods PSS SINCAL also offers full solutions to a complete workflow.

One of the most frequently used and increasing planning tasks is the connection of distributed generators to the grid.

PSS SINCAL offers a verification tool to check whether these power plants comply with the grid code interconnection requirements. The check of the grid code is a combination of diverse calculation methods like load flow, short circuit and harmonics and the evaluation of the results against the permissible limits in the (national) standards. For this the technical parameters of the generator have to be described in more detail.

The complete workflow is started by a simple „click“on the respective generator. The following requirements are checked in one run:

Utilization of all elements

Slow voltage changes

Fast voltage changes

Flicker evaluations

Harmonic evaluations

A full report can be created by a simple click. This Microsoft® Word® document is ready to be provided to the regulator / grid operator for acknowledgement

## Distance protection simulation

The distance protection method calculates the impedance settings for the three zones and the overreach zones (auto-reclosure and signal comparison) of distance protection relays in any type of meshed network.

When grading impedances are calculated, the setting given priority is the one that causes the protection to respond selectively regardless of how the network is connected. Initially, all values are calculated for the first zones and this is followed by all second zones and then all third zones. The second and third zone of the relays can be altered during or after calculation of the settings while working interactively from the screen, so it is a simple matter to accommodate the protection engineer’s ideas. There are various ways of taking into account the time grading of the third zone. The results of the program are provided in time grading diagrams drawn to scale and a table of settings for each protection device.

No definition of grading paths, system builds them automatically

Worst case network for each relay is build during the calculation (according to different strategies)

The algorithm DISTAL has the objective to determine settings that provide selectivity for all switching conditions

Specific modeling of each relay behavior

Results are relay specific settings

Calculation of primary or secondary values

Interaction between the calculation of each zone possible

Diagrams of relay setting and range of zones into the network

## Overcurrent-time protection simulation

The protection simulation module simulates the time sequence of the fault clearance in radial and meshed networks. This unique feature is called stepped event analysis. For this purpose, there is a data base of protection devices storing approximately 1000 circuit breakers with instrument transformers, low-voltage circuit breakers, fuses, bimetallic relays, contactors and miniature circuit breakers together with all possible settings. The combination with distance protection relays is no problem.

Faults can be simulated at nodes or anywhere on power lines or cables. The following fault types can be modeled:

Single-phase fault

Two-phase fault

Two-phase-to-ground fault

Three-phase fault

User-defined multiple faults packages, e.g. cross-country faults (see multiple fault module description)

Fault impedances, e.g. arc impedance can be simulated, if required.

Starting and triggering of protection devices are simulated in as many time steps as necessary. The operating state of the protection devices can be visualized in the network diagram by color code. Any violations of the grading times are also indicated, as is multiple tripping of protection devices. Directional elements can be freely defined. Damage curves for cables and transformer loadings are also displayed in graphical form.

The system generates grading diagrams for I2t, RX, and Zt functionality. The fields of application are the checking of thermal loads and incorrect tripping in normal operation, the determination of disconnection times, the coordination of protection and the checking of grading times.

**Specialties**

Meshed networks

Across all network levels

Data base with more than 1000 protection devices

Directional element

Protection failure

Over- and undervoltage tripping

Interlocks and intertripping

Free definition of protection devices

Mechanical protection devices

Faults located on node or lines

Fault impedances

Various short circuits

Colored display of the various relay states

Delays of relays/waiting times

Decaying back-feed of asynchronous motors

Cable/transformer damages curves

## Protection simulation and protection coordination

For networks with overcurrent, distance and differential protection devices.

This enhanced power system protection simulation module considers the settings of overcurrent and distance protection devices, as well as the protected zones of differential protection devices. The following steps are carried out:

1. Load flow calculation for direction decision and relay starting.

2. Determination of the protection devices that limit the concerned protected area and that have to trip.

3. Calculation of currents, impedances and tripping times.

4. Tripping of the device with the shortest release time.

5. Changing of network topology.

6. If fault is not cleared: second short-circuit calculation and determination of the next relay to trip.

7. Repetition of the above steps until the fault is cleared and the total fault clearance time is determined.

8. Evaluation whether the correct relays have tripped, and provision of all relevant information, e.g. indication of unselective relay operation.

Important is the simulation of special protection device properties:

Directional elements

Starting conditions:

- Overcurrent

- Voltage-controlled under-impedance

- Impedance characteristicsInterlocks and intertripping

Asymmetrical faults

Protection failure

Simulation across several voltage levels

Representation of downstream overcurrent time relays

**Method**

On disposal: load flow and several short circuits

Time-sequential work: possibility of correction or changes

Active elements with dynamic properties

Choosing or changing the protection philosophy

**Graphic documentation**

I-t grading diagram: across voltage levels, additional information

interactive changing of protection characteristics

Display of protection settings in network diagram

Z-t diagram: several downstream relays, impedance and zone reaches

R-X diagram: impedance area with directional lines and pointers

Composite protection: diagrams with both types of relays to check the coordination.

**Different protection devices**

Protection device catalogue with all setting facilities

Facility to augment the catalogs

Definition of general protection elements

**Protection simulation**

Symmetrical and asymmetrical short circuits

With and without preload

Faults at nodes and on lines

With and without fault impedances

Visualization of the operational state of protection devices (e.g. started, tripped) by means of color code.

**Protection documentation**

PSS SINCAL also offers a fully automated documentation of selected grading paths. This enables the protection engineer to quickly generate the necessary diagrams and maps.

## Arc flash analysis

PSS SINCAL‘s arc flash software module is intended for designers and facility operators of electrical plants. It determines the arc flash hazard distance and the incident energy to which employees could be exposed, based on the guidelines defined by IEEE 1584 standard.

Its calculation features include the Empirical Model, Lee Method, current limiting fuses and low-voltage circuit breakers as given in IEEE 1584. The Arc Flash Hazard calculations cover the empirically derived model for voltages from 208V to 15kV and a theoretically derived model for any voltage level. Additionally, user-defined O/C protection devices including I-t characteristics and current limiting behavior can be added, i.e. the usage is not limited to the protection devices stated in IEEE 1584.

Furthermore, required Personal Protective Equipment classes are determined in accordance with NFPA 70E standard. The calculated results can be documented in one-line diagrams, automatically generated reports and as printable warning labels.

## Dimensioning of low-voltage networks

Low-voltage fuse design, i.e. checking the tripping conditions, is a combination of load-flow calculation and short-circuit calculation. In accordance with the VDE 0102 standard, the program utilizes the minimum single-phase fault currents to determine the maximum permitted rated current of the appropriate fuse. For this purpose the protected zone under investigation is examined with help of a travelling fault to find the point where the minimum fault currents flow through the adjoining fuses. A protected zone can be limited by up to three protection devices. PSS SINCAL identifies the existing fuses whose rated current exceeds the maximum permitted value. A situation where the load current exceeds the maximum permitted current of the fuse will also be reported.

Unique method of checking fuses in low voltage networks

Results are the identification of deviations from planning standards

Fuses with incorrect rated currents are indicated in the network diagram

## Protection Assessment Checks

A first automated selectivity check for OC relays downstream of a feeder is available as a standard tool within PSS®SINCAL.

If there is need for a more detailed evaluation of the protection in complete feeders, an automated feeder check including backup protection is offered for overcurrent protection devices. Here the different reach zones and the limits can be customized.

The most advanced** Protection Analysis** – as an automated short-circuit sweep throughout the whole network – allows the **systematic assessment **of all operation and fault cases and saves a lot of time.

A result is a matrix with all simulated protection zones and the check of the actual protection settings against:

Normal selectivity

Backward routes

Protection failure (backup)

Specific consideration of machine protection

Different fault and different fault impedances

It shows the number of picked-up and tripped devices, the clearing time, and the number of steps to clear the fault.

When clicking on one cell you will directly be forwarded to this specific simulation within the network diagram for further evaluation.

## Protection device management - PSS PDMS

PSS®PDMS is a universal program to centrally manage protection devices and their settings. All the data are stored in a central relational database (either Microsoft Access or Oracle) for protection devices and can be read by other programs at any time.

PSS PDMS’ key features are:

Data is stored in a central relational database (either Microsoft Access or Oracle or MS SQL Server).

PSS PDMS is a multi-user enterprise application.

A modern Windows user interface optimally supports data management.

Protection devices are modeled comprehensively with all their functions and settings including different parameter sets for the same relay.

Settings are checked against the available settings ranges

Protection device templates can be created and managed and then used to generate real protection devices.

It is easy to connect to external documents (parameter files, descriptions of protection devices etc.)

Extensive functions for relay import and export.

Access rights (user roles) can be specified and customized according to the company’s need

User defined workflow (e.g. planned, approved, active settings) is supported including historical settings

Data exchange with PSS SINCAL enables the planner to verify the settings directly in the network model

## Probabilistic reliability

Reliability assessment for power systems evaluates a number of different criteria in the network planning process. There is a differentiation, for example, between failure and customer-orientated planning criteria, and deterministic and probabilistic criteria. A failure-orientated reliability criterion − such as the (n-1) criterion, for example − filters out those failures whose effects are unacceptable. Only one fault or two faults (n-2) are assessed at a time. In PSS SINCAL this can be done with the contingency analysis module.

Customer-orientated planning criteria summate all fault-related supply interruptions of a customer. Probabilistic reliability calculations are employed for determining expected values for individual customers. These characteristic values can then be compared against limit values for specific customers.

For a long time, deterministic reliability criteria were used exclusively for assessing adequate reliability of a power supply at the planning stage of a network. The task of the planner was to select a limited number of system states and fault scenarios and then to examine them for adherence to the requirements specified by the criterion.

The probabilistic reliability calculation makes special demands on the data base. In addition to the electrical and topographical data for load flow and short circuit calculations, additional information is needed for setting the boundaries of the network to be examined, and its component parts, for network protection and for simulating faults.

When analyzing reliability it is usually necessary to subdivide large transmission and distribution networks into smaller sub-systems. The subdivision of the system arises from the task to be examined. Within the examined system there are further boundaries. All individual items of equipment whose failure has the same effects on network performance are combined to form component units. This subdivision is especially important with regard to the degree of detail and computation time. The bounding of components, from which the inception of a fault and the intervention of the system protection can be simulated, is obtained by grouping items of equipment that are all tripped by the primary protection when a fault occurs. Overhead power lines, cables, transformers and bus bars usually comprise this tripping range orientated component bounding; the outgoing feeder and the equipment of the switch bay are assigned to the corresponding components.

Failure models have been developed from analyses of the operation of real networks and from fault statistics which allow the course of events of faults to be classified. The most important models are:

Independent single failure: failure of one single component

Common mode failure: simultaneous failure of several components due to a common cause

Multiple earth fault with multiple tripping: interdependent failure of two components in networks with resonant earthing or with an isolated neutral on the basis of an existing earth fault

Failure during maintenance of the backup component: interdependent failure during maintenance of the backup component

Over-functioning of protection devices: stochastic secondary failure due to non-selective tripping of the protection system

Protection device failure: stochastic secondary failure due to failure of the primary protection device and tripping of the backup protection device

The **analytic method** combinatorial generates all failure combinations. Only those combinations with a probability above a given threshold value are further considered in the calculation. Another possibility to limit the number of the combinations included in the calculation is the limitation of the order, i.e. the number of simultaneously failed elements, of the combinations. Probabilistic reliability calculation allows a quantitative description of supply reliability through appropriate characteristic indices. Internationally in the field of reliability calculation a multitude of different more or less meaningful and widespread indices exist. However, certain basic indices have proven to be valuable, and from those basic indices further sizes can be calculated on demand.

For a more detailed simulation PSS SINCAL also offers a fully featured **Monte Carlo method**. This especially is useful in the area of maintenance outages. Parallel usage of the full cores enables the user to get to a solution in a reasonable time.

Symbol | Name | Unit |
---|---|---|

Hu | Frequency of supply interruptions | 1/a |

Tu | Mean duration of supply interruptions | h or min |

Qu | Unavailability | 1(common: min/a) |

Lu | (Cumulated) interrupted power | MVA/a |

Wu | (Cumulated) energy not supplied | MVAh/ |

PSS SINCAL also supports most of the indices like SAIFI, SAIDI, MAIFI, ASIFI, ASIDI or CAIDI.

## Cost calculation

Economic efficiency calculations for power systems determine the economic benefit of development and restructuring measures and evaluate costs at yearly intervals.

For cost benefit analysis PSS SINCAL uses an evaluation method commonly used in electricity companies: the Net Present Value Method.

To evaluate costs, the Summation Method determines costs at yearly intervals.

Economic efficiency calculations determine the costs and present values resulting from network operations and diverse expansion and restructuring measures for the time period from the current view time t0 to the planning horizon tn.

The calculation results are prepared annually at the end of the year. These "annual tranches" are used to evaluate both investment expenditures and ongoing annual costs. The annual results are provided both as present values and not yet discounted costs.

Analogous to the net present value method, the costs Cc are determined from the acquisition costs Ci and shutdown costs Cs together with the operating costs in the observation period. If the calculatory life span of the equipment is greater than the planning horizon, then the residual value Cr also needs to be considered.

The summation method provides you with the actual costs for individual annual tranches and the sum of all occurring costs for the planning horizon.

PSS SINCAL provides two different types of results:

Total results for the entire observation period

Results for each annual tranche in the observation period

The economic efficiency of an investment is actually evaluated using the total results from the entire observation period tn – t0. All accruing costs are evaluated and then compared to the anticipated income.

For current network operation, mainly expected annual costs are of interest. Results are prepared for individual annual tranches.

## ICA Simulation (Maximal Hosting Capacity)

In some regions of the world the questions is not if a specific DER can be linked to the grid, but how much generation can be linked without creating the need for network improvements considering the quality and reli-ability of the network.

For this type of study the evaluations listed in the follow-ing have to be performed under all relevant network conditions. These can be defined with help of profiles of operations points in addition to the normal load flow:

Thermal loading of the network elements within user-defined ranges for load flow and short circuit

Steady state (long) voltage changes within defined limits

Dynamic (quick) voltage changes within limits

Reverse power flow allowed

Protection system working correctly (reach factor check)

For each node in the network PSS®SINCAL evaluates the maximal power which does not violate these constraints.

The results are available as contour plots on top of the network diagram or in form of a results view.

## Load and generation profile simulation

Load and generation profile simulation is a special form of load flow calculation varying load consumption and generation output over time according to a given daily, weekly or yearly profile. Typically, load profiles with 15-min time steps are used to simulate the effect changing load flows conditions, which is also applied in smart grid simulation and distributed generation modeling.

Besides the normal nominal power, loads have assigned information on the specific type of consumer with a daily load profile (in absolute or relative values). Optionally, the user can define customer data like annual consumption or maximum power demand.

The power of each load or generator at a given point in time is calculated based on the given parameters and operation profile.

For customer loads of the same type it is possible to consider the effect of simultaneity/coincidence. This can be easily done by means of the simultaneity factor which can be defined as a function. Different simultaneity functions can be defined for different customer groups. The actual simultaneity factor is calculated based on the number of downstream connected customers of the same load type. Taking into account the effect of simultaneity, the load flow calculation can no longer calculate with static impedances for the network in dependency of the location of the consumers.

**Results**

All load flow results are available including the analysis of maximum or minimum values (e.g. for voltages and loading etc.).

Diagrams with daily, weekly and yearly profiles for nodes and branches are created.

Voltage band and loading limit violations as well as line utilization during the simulation period are indicated in diagrams.

Total losses and lost energy are presented in a diagram.

## Load development

Load development calculation provides information on how to develop electrical networks taking into account future load growth and migration. Load forecasts are the input data and can be derived by historical data directly in the GUI.

PSS SINCAL load development calculations are enhanced load flow calculations with load and generation levels that vary over time. PSS SINCAL automatically determines load flow results at points in time when changes are applied to the network.

In addition to nominal values, PSS SINCAL assigns load changes (i.e. in-/decreases) and considers commissioning and decommissioning dates for network components. Absolute or relative load changes can be assigned to individual loads, groups/types of loads or loads in graphically selected areas. A commissioning and decommission date can be entered for each network element. This allows taking new loads, transformer, lines, etc. into service and existing ones out of service at future points in time. All power system development scenarios and the foresighted assessment of future network performance can be modeled.

The entire load flow calculation results with evaluation of minimum and maximum values (e.g. voltages or loading levels) and diagrams with information on power requirements and overloaded lines are provided.

Additional information is provided if limits have been violated during the calculation period.

The load development tool provides valuable information to identify weak points and to prioritize required network reinforcement or restructuring measures.

## Optimal network structure

Power system structure optimization is the determination of the optimal design for medium-voltage networks. 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 is based on a station and route model defining possible connections between infeed and loads. The optimization has the objective to minimize losses while complying with technical limits (max. feeder load, max. voltage drop, etc.). The cost of transforming the network into the proposed structure is determined.

Three optimization methods - rotating ray, best savings and best neighbor – are available. 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.

## Generic wind models

The wind power model package contains the following models for load flow and stability simulations during distributed generation modeling:

Squirrel-cage induction generator (SCIG)

The SCIG model represents a fixed-speed wind turbine. It includes the induction machine model, single or two-mass mechanical model, aerodynamic model, over-/ undervoltage protection, no-load compensating capacitor or switched capacitor bank.Doubly-fed induction generator (DFIG)

The model includes the induction machine representation, DC-circuit, rotor side converter control and protection (reactive current boosting, crowbar protection), line-side converter control, single or two-mass mechanical model, over-/ undervoltage protection.Full converter wind generator (FCSG)

The FCSG model is based on a variable speed generator. It includes the synchronous machine model, inverter and control, AC voltage/reactive power control, DC-voltage control, reactive current boosting, current limitation, virtual inertia / pitch control, aerodynamics model; overspeed/DC overvoltage, AC over-/undervoltage protection.

## Generic FACTS models

The FACTS model package contains the following FACTS models for load flow and stability simulations:

SVC - Static Var Compensator

SVC Plus – STATCOM

Mechanically switched capacitors

TCSC – Thyristor Controlled Series Compensation

## Line constants

Line constants calculation is capable of determining characteristic parameters of overhead lines and under-ground cables. The line parameters required for network analysis − i.e. load flow, short circuits, interferences and other studies − can be calculated based on geometrical configuration (i.e. tower or trench structure), overhead line or cable type. The following systems can be calculated:

One-phase systems with ground return conductor

Two-phase systems (AC systems, e.g. railway systems)

Three-phase systems

Sections with up to nine parallel systems with different voltages are possible. The fully couple matrix can be automatically assigned to the elements of the network model.

## Graphical model editor: Graphical Model Builder (GMB)

In PSS SINCAL a modern Microsoft® Visio®-based Graphical Model Builder (GMB) is integrated as a stand-alone application. This Graphical Model Builder uses the powerful Visio interface to easily create dynamic models. It is a simple and quick-to-operate drawing tool for implementing, editing and documenting of dynamic models:

Excitation systems (AVRs)

Turbine governors

Power system stabilizers

HVDC models

FACTS models

Load models

Transformer models

Distributed generation models (e.g. generic wind models)

New storages models

Protection functions

The Graphical Model Builder system has a large symbol library which contains more than 100 different control blocks in the form of symbols. The user establishes system diagrams and the block diagram by graphical connection of library symbols. The data is input via masks that are object-related and have abbreviated aid texts in addition to detailed aid texts. It is also possible to combine groups of linked symbols to form independent new symbols as macro models and to add these to the symbol library or to the user’s own library.

The symbol library “BOSL” (Block-Oriented Simulation Language) contains more than 100 different function blocks. These blocks can be combined to any open or closed-loop control structures or evaluation devices by means of the graphic interface. Besides very simple blocks, such as PID elements, there are also complex “blocks”, such as FFT (Fast Fourier Transformation). The controllers can be stored as subsystems in a library so as to link them quickly to a system. Parameterizing can be input individually and changed, or the default values can be used. Optionally complex open and closed-loop control and protective functions can be implemented with the Block-oriented Simulation Language. External, user-defined subroutines can also be coupled (open-loop) and there is an interface to real-time applications (closed-loop). The block-oriented structures can be combined with FORTRAN-like terms, such as mathematical functions, logical terms or instructions, e.g. IF/THEN/ELSE.

The user can switch between two different block styles:

1. The European DIN symbols and

2. The transfer functions.

The Graphical Model Builder also offers testing and debugging functionalities like in Matlab® Simulink®. After finishing the design of the model there is no need for compiling and linking. The user can now start PSS SINCAL and the dynamic simulation.

Black-Box manufacturer models can be connected with input and output values in NetCad.

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