ram with network components

An electrical power system consists of nodes and elements.
Nodes
A node is the connection point of two elements or a location, where electrical
energy will be produced or consumed (generator, load). A node is described by its
name (identification with 17 characters),
nominal system voltage in kV,
description (31 characters),
network group or area,
type of node (main bus bar, bus bar, sleeve, special node),
association with a station.
The nominal system voltage Un is the line-to-line voltage, for which a power
system is designated and on which several characteristics of the power system
has been referred. In NEPLAN the nominal system voltage of the nodes must be Tutorial
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entered during the node data input. Every voltage is given as a line-to-line voltage
(delta voltage).
Elements
An element corresponds to a network component, like e.g. cable, transformer or
electrical machine. There are active elements and passive elements. An element
is described topological by a starting and an ending node. For three windings
transformers a third node must be given. The elements will be described electrical
by
the rated current, rated power and rated voltage and
its parameters, such as losses, reactances, ...
In NEPLAN these parameters are entered with the help of input forms.

The active elements are network feeders, asynchronous machines, synchronous
machines and power station units. A network feeder represents a neighboring
network.
The passive elements are lines, couplings, switches, reactors, two and three
windings transformers, shunts and loads. The loads can also be entered along a
line without entering nodes (line loads).
Modeling of Active Elements
For a short circuit calculation the active elements are modeled with the help of
their sub-transient reactances.

For a load flow calculation these elements will be represented by resistive and
reactive powers (PQ-nodes) or by voltage magnitude and angle (slack nodes) at
the node. The network feeder usually will be modeled as a slack node.
Protection Devices, Current and Voltage Transformers
Protection devices (overcurrent relays, distance protection relays, circuit breakers)
and current or voltage transformers are associated with the built-in node and the
switching element. They have no influence on the load flow and short circuit
calculation. Only their limits are checked during the calculation. These elements
are used in the relay coordination modules.
Field
A field can be assigned to every node/element connection. If there were protec-
tion devices at the node and in the element the field name will be associated with
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the devices. A field has no meaning for the calculations or for protection device
coordination and will only be used in relation to the data base.
Station
A station can contain several nodes and has no meaning for the calculations or
for protection device coordination. It will only be used in relation to the data base.
General Element
NEPLAN provides a general element type, which can be used for documentation
and information purposes. These elements will not be used for the calculation.
New general element types can be defined with the symbol editor. For each
element type it is possible to assign a SQL database table (requires the optional
NEPLAN SQL database driver module). The fields of this SQL table can be
defined by the user.
Symbol
Each element has a standard symbol. If you like to have a different symbol, you
can select a symbol from the library before adding a new element to the network
diagram. A symbol library is included in the NEPLAN package. You can add your
own symbols with the Symbol Editor (see chapter "Symbol Editor"). It is also
possible to change the symbol as well as the angle of the element later (see
"Element - Symbols" in chapter "Menu Options").
Switches
In NEPLAN the switches are used to change the network topology (switching
on/off elements). There are two different types of switches:
physical switch and
logical switch.
Physical switches are couplings, circuit breakers and disconnect or load switches.
They can be entered in two ways: either they are entered as an element with a
starting and an ending node or the are entered as protection devices, which are
topological defined with the element to protect and one node of the element.
Logical switches are fictive switches, which are assigned to all elements (see
section "Elements"
on page 2-2)
by the system. A line, for example, has two
logical switches, one at the starting and one at the ending node. A physical switch
has no logical switch, because it will already be switchable.
During the input of a network, the physical switches can be neglected, because
switching can be done with the help of the logical switches. These has a disad-
vantage, when a line leads to a double bus bar system. Switching from one bus Tutorial
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bar to an other, the user has to change the starting or the ending node of the line.
If the user enters two disconnect switches (one to each bus bar) with an additional
node in between, the switching can be done with the disconnect switches. The
physical switches can be reduced during the calculation (see "Disconnect Switch
Data" in chapter "Element Data Input and Models").
Network Group
A network group is a network area. The network is defined in the node data mask.
Each node with the same group name belongs to the same network group or
area. Each area can be drawn in a different color.
Partial Networks
Unlike network groups, a partial network is an independent network. A partial
network has no connections to any other networks. You can make partial
networks by opening logical or physical switches. It is possible to color each
partial network differently (Fig. 2.2).

Network feeder
Node
Node
Node
Disconnect,
Load switch
Line
logical switch "open"
Station
Partial network 2
Partial network 1

Fig. 2.2 Partial networks
Graphic Layer
To each node or element a graphical layer will be assigned. Before you insert a
new node or element graphically, you can choose the graphical layer. The graphi-
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cal layers can be displayed selectively. For example, it's possible to use different
layers for current transformers and relays. If you are doing load flow calculation,
you could switch off the layer for the relays. If your doing relay coordination you
can switch on again the relay layer. The graphical layer of each element is
displayed in the title oft the data form of the element. Please note the difference
between the graphical layers and the network layers (see "Network Layer
Technique"
on page 2-15
). Each graphic layer can be colored differently. If a DXF
file will be imported, NEPLAN takes all layers which have been defined in this
DXF graphic. It is possible to color DXF layers and NEPLAN graphic layers
differently.

Saving the Network Data
The topological, the electrical and the graphical data of the elements, protection
devices, current transformers, etc. as well as the load data are saved in the
project file.
The project file is an ASCII file with the extension .MCB. The previous version of
the project file will be saved in a file with the extension .MC_
The load data or the so called node data can be additionally saved in the node
data file. These are the active or reactive power of the loads or generators as well
as the voltages of the slack nodes (usually network feeder). The file extension is
.NDB.
The topology can also be saved in a file. The state of all logical and physical
switches as well as the taps of tap changing transformers are saved. The file
extension is .ZDB.

Automatically Saving the Data
If this option is active (standard setting) the project will be automatically saved
before each calculation. The network data will be saved in the file tmp_proj.mcb.
After a computer breakdown the user can immediately read this file and save it
under the valid project name.
Note! After computer breakdown no other project must be opened, otherwise the
temporary file will be overwritten!
Thus the file name tmp_proj.mcb is reserved by NEPLAN for internal use.
Variant Management System
For calculating different cases (variants), NEPLAN has the possibility to separate
and save the loads, the topology and the single line diagram from the project data. Tutorial
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NEPLAN is also able to manage all differences form a base network system, this
means NEPLAN can notice all changes which have been done to a network (e.g.
insert new elements, change an element, delete an element). These differences
can be saved in a different file.
As soon as the base case or root network (*.MCB file) has been loaded, variants
can be defined. The variant can consist of the following data:
loads (node data), feeders (*.NDB file)
topology data (*.ZDB file)
graphic (single line diagram) data (*.NGR file)
Network differences (*.VEL files)

In the project files (*.MCB file) all network data (incl. loading, topology, graphic
data) of the base case system or root network are saved.

If the user changes data of the root network (e.g. deleting, inserting, changing
nodes or elements) NEPLAN recognizes the changes. It