Bus

Low-impedance conductor to which several electric circuits can be connected at separate points.
Note – In many cases, the bus consists of a bar. IEC 60050.

Bus in PSP-UFU

The bus element, or simply busbar, is a connector or node in the PSP-UFU single-line diagram.
This bus can represent a PCC (Point of Common Coupling), a distribution pole, a substation, a substation bus, among many other types of analysis and connection points between elements.

Bus editing form

Attention!

The bus must be the first electrical element inserted in the power diagram, since all other power components are connected to it.

The figure below shows the bus data insertion/editing form:

This form is subdivided into four different contexts:

• General: where general bus information and load flow data are entered;
• Fault: where the shunt short-circuit must be inserted;
• Stability: containing options for displaying bus data in time-domain plots and inserting three-phase faults in transient stability calculations;
• Power Quality: contains the option to display the harmonic impedance seen by the bus.

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General

Name

Electrical element identification. Any number of characters can be entered using the Unicode standard.

All PSP-UFU power components have this field.

Nominal voltage

Used to calculate the base impedance of some connected elements, as well as the transformer turns ratio between buses.
Its unit can be selected, expressed in V or kV.

Changing this parameter will modify the entire voltage of the segment connected by electrical lines, and a warning is issued to the user.

Controlled voltage

Characterizes the bus as a voltage-controlled bus (PV Bus).

Attention!

This option is only valid if a synchronous machine is connected; otherwise, the value is ignored.
If the reactive power limit of the connected synchronous machine is exceeded, this value is also ignored.

The value can be entered in p.u. or in volts (or kV if the nominal voltage is in this unit).

Slack bus

Characterizes the bus as a slack bus (Swing Bus).
This option is only valid if a synchronous generator is connected; otherwise, an error message will appear during program calculations.

Fault

Insert fault

Indicates whether there is a short-circuit at the bus in short-circuit studies.

Warning!

Note that this option will insert a fault for the short-circuit calculation and will not be considered in the stability study.

Fault type

Selects the type of bus shunt fault:

• three-phase to ground
• phase-to-phase
• phase-to-phase-to-ground
• single-phase-to-ground

Fault location

Selects the phase(s) where the fault occurs (or their combination in two-phase faults); this option is disabled for three-phase faults.

Fault resistance and reactance

Represents the fault impedance.
Solid short-circuits (zero-impedance faults) are represented by entering zero in both fields.

Stability

Print data

Displays the edited bus data in the transient stability study plot.
The following data are shown:

• bus voltage magnitude
• bus voltage angle

Insert fault

Inserts a three-phase fault at the bus in the stability calculation.

Warning!

This option will insert a fault for the stability calculation and will not be considered in the short-circuit study.

Time

Time instant ($t_{fault}$) when the fault occurs during stability studies.
This and the following fields are only accessible if a fault is inserted in the stability study.

Fault duration

Duration of the inserted fault ($\Delta t_{fault}$) in the stability study.
The fault starts at $t_{fault}$ and is cleared at $t_{fault}+\Delta t_{fault}$.

Fault resistance and reactance

Fault impedance in stability studies.
A solid fault is represented by inserting a very low shunt impedance ($j10^{-5} p.u.$).

Power Quality

Print bus harmonic impedance

Prints the harmonic impedance seen by this bus in the Frequency Response study.

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Tip

Summary of how to define bus type:

• To define the bus as a PQ Bus, the options "Slack bus" and "Controlled voltage" must be unchecked;
• To define the bus as a PV Bus, check only the "Controlled voltage" option, leaving "Slack bus" unchecked;
• To define the bus as a Slack Bus, check the "Slack bus" option.
  If "Controlled voltage" is unchecked, a controlled voltage of $1{,}0~p.u.$ is assumed.

Warning!

The system must have only one slack bus.