Power Systems Transients Transients.pdf · (EMTP) in early 1960s. Later when worked at BPA...

ELEC4612: Transients in power systems

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Power Systems Transients

Toan Phung2012

The University of New South Wales

School of Electrical Engineeringand Telecommunications

Transients in power systems:

Occurs due to sudden change in circuit conditions, e.g. switch operates or fault occurs. Network changes from one steady-state to another.

Under AC, energy transferred cyclically between Ls and Cs in circuit. Sudden change in circuit results in redistribution of energy to satisfy new condition. This, however, cannot happen instantaneously.

Transient period is very short (s to ms range)

Can produce excessive voltages or currents → damage to equipment


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Internal Transients:

switching operations (load break switches, circuit breakers, disconnectors), short-circuit faults

cause of most power system transients.

External Transients:

overvoltage induced by lightning strikes in vicinity of transmission lines

current surges due to direct lightning strikes on line conductors.

Transient Recovery Voltage (TRV):

generated by operation of CBs during current interruption for fault clearance or even just load current breaking.

L = system inductance between fault and source; C = total distributed capacitance of system


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Current chopping:

occur when CBs are interrupting small inductive currents such as transformer magnetizing current.

current interrupted before natural current zero. As a result, inductance still contains substantial stored energy (which is zero at natural current zero). Dissipation of this energy will cause an enhanced and additional voltage transient at breaker terminals.

in contrast to normal TRV, transient voltage due to current chopping is not limited to a peak of 2Vm: it can potentially be much higher.


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Offset current during faults

When S closes at time t=0 to simulate fault, resulting current is:

DC offsetcurrent transient


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Purelyinductive

Purelyresistive

Alternative Transient Program (ATP)

H.W. Dommel created Electromagnetic Transients Program (EMTP) in early 1960s.

Later when worked at BPA (Bonneville Power Administration, USA) and together with S. Meyer, made EMTP source code public-domain prior to its commercialization in 1984.

Based on this public-domain EMTP, S. Meyer and T. Liu developed the Alternative Transient Program (ATP).

ATP is not in public domain. Licensing is required. Contact local ATP-EMTP users group.


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Operating principles and capabilities:

Predict electrical variables (voltage, current) as functions of time following some disturbances

Use trapezoidal rule to convert differential equations of network components into algebraic equations and solve in the time domain, e.g.


Operating principles and capabilities:

Also provide frequency-domain harmonic analysis and calculation of frequency response of phasor networks.

Large library of components:

Basic components: R, L, C, sources, switches

Other non-linear components: surge arresters, power electronic devices, etc.

Power system components: rotating machines, transformers, transmission lines, cables.

Interface to program modules MODELS and TACS to enable modelling of control systems and components with nonlinear characteristics.


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Structure of user’s ATP input data file


Example of ATP input data file


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ATPDraw version 5.6:

MS-Windows graphical preprocessor to ATP version of Electromagnetic Transients Program (EMTP).

User constructs circuit using mouse and selecting components from menus. Extensive circuit editing facilities.

ATPDraw then generates ATP input file. ATP and plotting programs can be called from ATPDraw.

Developed by Hans K. Høidalen (Norwegian Uni. of Scienceand Technology), financed by BPA.

ATPDraw program is royalty free and can be downloaded from several Internet sites: EEUG, JAUG users group.

Software installation – A simple procedure:

Step 1: run InstATP121.exe to install Basic set of programs into a directory, e.g. E:\ATP:

ATP/MinGW (20-Aug-2008)

ATP Launcher (Ver 1.16)

ATPDraw (Ver 5.3)

PlotXY (Dec-2007)

GTPPLOT (20-Aug-2008)

Associations

Step 2: run InstATP121_add.exe to install Additional set

Step 3: run InstATP121_lib.exe to install Library set

Step 4: run ATPDraw57_install to install ATPDraw updater

Step 5: run PlotXY-Nov09 to install new PlotXY into E:\ATP


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Files and sub-folders in ATPDraw folder:

Files required to run ATPDraw:

ATPDraw.exe

ATPDraw.scl (standard component library)

ATPDraw.chm (help file)

User’s own library components and include files

User’s circuit is stored in a project file “.acp”

ATPDraw creates “.atp” file as input to ATP simulation

User’s interface


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Build and Edit circuits:

Operating the mouse:

Left click

Right click

Left click and hold

Left double click

Where: on object, connection, node, open area

Generally:

left button for selecting objects or connecting nodes

right button for specifications of object/node properties


Useful edit operations:

Undo, Redo

Cut, Copy, Paste, Duplicate, Delete

Rotate right, Rotate left, Flip horizontal

Rubber band (stretch connection)

Select all, Select inside, Select group of objects

Zoom In/Out


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Steps in building a new circuit :

Create a new project file (.acp)

Select components required from library

Specify data to components

Connect components to form circuit

Assign node names, specify grounding

Save project file

Modify miscellaneous parameters (ATP | Settings)

Run ATP to create ATP input file (.atp)

Circuit objects:

To show Component Selection menu, click right mouse button in an empty circuit window space

Component dialog box:

Attributes

Characteristic


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Circuit objects:

Probes & 3-phase:

probes for node voltage, branch voltage, current, TACS, Models output monitoring

3-phase transposition objects

splitter (coupling between 3-phase and single phase circuits) and collector.

ABC/DEF Reference objects for specifying master node for phase sequence

6-6 phaseRL coupled line

Exa_2.acp: example of three-phase circuit


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Circuit objects:

Branch Linear: resistor ()

capacitor with damping resistor (F if Copt=0)

inductor with damping resistor (mH if Xopt=0)

RLC in series

3-phase RLC in series, independent values in phases

3-phase RLC in series, Y coupling

3-phase RLC in series, coupling

capacitor with initial condition

inductor with initial condition

Circuit objects:

Branch Non-linear:Current dependent resistor

Time dependent resistor

Current dependent inductor with or without initial flux

True non-linear current dependent inductor with or without initial flux

Pseudo-nonlinear hysteretic inductor with or without initial flux

Current dependent resistance in exponential form

3-phase current dependent resistance

TACS / MODELS controlled time dependent resistor


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Circuit objects: Switches:Single or 3-phase time controlled.

Multiple closing/openings.

3-phase time controlled. Independent.

Voltage controlled.

Diode. Uncontrolled.

Valve/thyristor/triac.

TACS/MODELS controlled.

Current measuring switch.

Statistic switch.

Systematic switch.

Ideal or nonlinear resistance with forward resistance and snubbers

Circuit objects:

Sources:AC

DC

Ramp or slope-ramp

Double exponential

Voltage or current

Single or 3-phase

Ungrounded or grounded

TACS/MODELS controlled

CIGRE/Heidler/Standler type

User-defined time characteristics


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Circuit objects:

Steady-state:RLC present only during initialization, t<0

CIGRE single-phase load

CIGRE three-phase load

HFS source: harmonic frequency source

Linear RLC for HFS study

Kizilcay F-dependent: frequency dependent branch in s or z domain

Load flow PQ: component with active & reactive power restriction (load bus)

Load flow UP: component with voltage & active power restriction (generator bus)

Load flow TQ: component with angle & reactive power restriction

Plotting programs for ATP:

Execute ATP simulation: TPBIG.EXE

Simulation results stored in “.pl4” file.

Windows-based plotting programs:

ATP Analyzer

GTPPLOT

PlotXY

others


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Plotting program PlotXY and PlotXWin:

No installation procedure, simply copy PlotXY.exe or PlotXWin.exe to directory of choice, eg. E:\atp\PlotXY

Graphical User Interface

Up to 8 plots per sheet, 8 files on same sheet.

Up to 5 simultaneous plot windows

plots versus time, X-Y plots

Linear or logarithmic scales

Factors, offsets and zoom support

automatic axis scaling and labelling

Cursor to display numerical values

printing and Windows Metafile export facilities

Plotting program PlotXY and PlotXWin:

PROCEDURE:

Run program → Data Selection Window

Click ‘Load’ button to load a ‘.pl4’ file

Click on variables to select for plotting

Set factors and offsets if desired.

Click ‘Plot’ button to plot → Plot Window

Click ‘Save’ to export to ASCII file (.adf) or MatLab format

Plot Window functions:

Title, Customise plot, Manual scale, Show cursor, Mark, Write WMF file, Copy to clipboard, Print


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Example: lightning impulse generator

Pasoni & Villa 400kV/20kJ impulse generator (UNSW HV lab)


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1.2/50s


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Resources and references:

ATP-EMTP user groups (www.emtp.org)

Join ATP-EMTP-L mailing list

ATPDraw version 5.6 for Windows Users’ Manual

Plotting Programs PlotXY and PlotXYWin – Short Description and Operating Instructions, October 2005

GTPPLOT: Plotting Program for ATP Output Files, Orlando Hevia, Canadian/American EMTP User Group

Users Guide to Models in ATP, Laurent Dube, 1996

EMTP Theory Book

Power Systems Transients Transients.pdf · (EMTP) in early 1960s. Later when worked at BPA...

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Transcript of Power Systems Transients Transients.pdf · (EMTP) in early 1960s. Later when worked at BPA...