Electrical Components

A detailed list of all supported electrical components and their attributes can be found in the latest Data Exchange Format Tables and in the XML Schema Definition.

Buses

Buses define the electrical nodes where lines, connections and transformers are connected. A general requirement for buses is that the base voltage $V_{nom}$ should be defined.

A bus can host several other components, such as

• Loads
• Generators
• Storages
• Network Feeders

Lines

Lines define cables or overhead lines and are characterized by the following electrical parameters:

• length $L$
• resistance per length $r$ (positive and zero sequence)
• reactance per length $x$ (positive and zero sequence)
• capacitance per length $c$ (positive sequence, the zero sequence capacitance is ignored)
• frequency $f$
• maximum current $I_{max}$

Lines are connected on both ends to a bus. The length, resistance, reactance and capacitance are used to calculate line currents, line losses, bus voltages and phase angles during Power Flow calculation calculations. The maximum current is used to calculate the line loading in %.

The electrical parameters can be defined in the Component Library.

Lines are modelled as single lines with the $\pi$-equivalent circuit:

• $z=r+\mathrm{j}\cdot x$
• $y=\mathrm{j}\cdot 2\cdot \pi \cdot f\cdot c$

Connections

Connections model lossless lines. Electrical parameters are not required.

Details

Due to numerical reasons, Connections are assigned a very small resistance of $0.01m\mathrm{\Omega }$.

Transformers

Transformers are the only electrical component that can connect two buses with different voltage levels. Transformers are characterized by

• Rated power $S_r$
• Maximum apparent power $S_{max}$
• Short circuit voltage $U_k$
• Copper losses $U_r$
• Rated voltage at primary and secondary side $V_{R_1}$, $V_{R_2}$
• Vector group
• Star point grounding type and grounding impedance

$U_k$ and $U_r$ are used to calculate currents, losses, bus voltages and angles during Power Flow calculation calculation.

$S_{max}$ is used to calculate the transformer loading in %.

The vector group and star point grounding are required for short circuit calculations (especially for asymmetric faults with ground connection).

The turns ratio of the transformer is specified on both sides of the transformer as $r_i=\frac{V_{no{m}_i}}{V_{R_i}}$, where $i\in [1,2]$ is the primary and secondary side of the transformer.

Tap changing

An on-load tap changing (OLTC) transformer can be defined. It acts as a controller during operation and changes the tap automatically to keep the voltage of the measured bus close to the set-point.

The following parameters are required

• Number of taps [-]
• Tap size [%]
• Dead-band [%]
• Voltage set-point [pu]
• ID of the measured bus

The electrical parameters can be defined in the Component Library.

Voltage Regulators

Voltage regulators behave similar to OLTC transformers. They are hosted by a line. The voltage is measured at the end of the line that is further away from the slack bus.

The following parameters are required for the model

• Number of taps [-]
• Tap size [%]
• Dead-band [%]
• Voltage set-point [pu]
• ID of the hosting line

Switches

Switches are purely visual elements to indicate if a line or connection is connected or disconnected from a bus. Switches are hosted on the end of a line or connection. Switches can optionally host protection devices that define a switching behaviour when running a Protection calculation.

Fuses

Fuses are used for the Protection calculation. Current dependent switch-off times and current ratings are defined in the Component Library.

Fuses are hosted on the end of a line or connection and also indicate the connectivity to the bus (open or closed).

Protection Devices

Protection devices define the switching behaviour of a switch when running a Protection calculation. Two types of protection devices are available:

• Definite Time Overcurrent Protection
• Distance Protection

The Definite Time Overcurrent Protection device opens the switch after a definite period of time once the current exceeds the defined value. The Distance Protection device defines a impedance-time characteristic to actuate the switch.

Loads

Loads are primarily used in the Power Flow calculation. They are hosted by buses.

The following parameters are required:

• Active power $P$
• Reactive power $Q$ (or power factor $\cos (\varphi )$)

A time series behaviour can be defined by including the ID of the associated smartmeter or assigning a pre-defined reference profile from the Component Library.

Voltage dependent reactive power and power factor characteristics can be defined in the Component Library.

Loads can be connected to one, two or three phases.

WARNING

Not all features support asymmetrically connected loads yet.

Generators

Generators are primarily used in the Power Flow calculation. They are hosted by buses.

The following parameters are required:

• Active power $P$
• Reactive power $Q$ (or power factor $\cos (\varphi )$)

A time series behaviour can be defined by including the ID of the associated smartmeter or assigning a pre-defined reference profile from the Component Library.

Voltage dependent reactive power and power factor characteristics can be defined in the Component Library.

Generators can feed three phase Short Circuits that occur nearby. Depending on their connection type, they contribute to a greater or lesser extent to the short circuits:

• Direct: No contribution
• Inverter: 1x rated current
• Synchronous Machine: 8x rated current
• Asynchronous Machine: 6x rated current
• Converter: 1x rated current

Generators can be connected to one, two or three phases.

WARNING

Not all features support asymmetrically connected generators yet.

Storages

Storages are primarily used in the Power Flow calculation. They are hosted by buses. Storages add a time dependency to the time series based Power Flow calculations because the state of charge of the storage is time dependent.

Two different controller types for the storage element can be defined in the Component Library:

• $P(U)$
• $P(Loading)$

The first one will charge/discharge the battery based on the voltage measured at the controlled bus. The second will charge/discharge the battery based on the calculated loading of the controlled line or transformer.

The following parameters are required to model a storage element:

• Rated Power $P$
• Rated Energy $E$
• Charging/Discharging efficiency ${\eta }_{ch}$, ${\eta }_{dis}$
• Min/Max state of charge $So{C}_{min}$, $So{C}_{max}$
• Initial state of charge $So{C}_{t=0}$

Storages are assumed to be connected on all three phases.

Network Feeders

The network feeders represent the higher level power grid connections and are hosted by a bus. The bus will act as the slack bus in the Power Flow calculation. The grid can have multiple network feeders.

The network feeder is characterized by the following parameters:

• Operational voltage $v_{nom}$
• Operational angle $\theta$
• Min/max short circuit capacity $S_{k{Q}_{min}}^{″}$, $S_{k{Q}_{max}}^{″}$ of the overlying grid
• Impedance to reactance ratio $\frac{X}{R}$ of the overlying grid

The last two parameters are used to parametrize the short circuit behavior of the network feeders of the sub grids when splitting.

Stations

Stations are a purely visual element without any electrical characteristics. It acts as a container for electrical components and can represent a

• transformer station
• substation
• distribution cabinet