De la igualdad formal a la igualdad material

"



The above resistance is maintained constant for all time bands and sequences (negative, zero, positive). In this case the X/R ratio will be variable for different time bands and sequences.

3.7 AC IEC 60909 Short Circuit

This analysis method is based on the IEC60909 Standard. The Calculation Tab is similar to the AC and ANSI/IEEE Standard and provides the same options. Users can select calculations based on different versions of the standard:

 1988 Version

 2001 Version

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The short circuit program supports two options for generators and motors resistances. The first option uses constant X/R ratio (which is defined in the generator and motor input dialogs). In the second option (variable X/R, see the lower left part of the following figure), the generator/motor resistance is computed from the

The above resistance is maintained constant for all time bands and sequences (negative, zero, positive). In this case the X/R ratio will be variable for different time bands and sequences.

In the IEC 60909 short circuit program, the control tab allows users to select:

 Fault Current Multiplying Factors

 The method employed in calculating the Peak Current (method A, B, C or Classical Thevenin) Also, as per IEC 60909 standard, users can select:

 System Voltage

 IEC maximum Voltage

 IEC minimum Voltage Peak current method:

 Method A: uniform ratio R/X. The smallest X/R ratio determines the k factor

 Method B: applies to the calculation of peak current in mesh networks X=1.15 multiplied by the Xb. Xb

from Fig.8 page 47 IEC 60909 Std.

 Method C: applies to the calculation of peak current in mesh networks; The value of X is calculated from Fig. 8, IEC 60909 and depends on X/R ratio of the network

 DesignBase Thevenin: X is calculated from the Thevenin equivalent

3.7.1 Impedance Correction Factors:

Apply

K

_gfactor to Generator

Z

_g impedance:

This field should be selected when calculating the initial short circuit current in systems fed directly from generators without unit transformers. This is the case when short circuit currents are calculated at generator terminals.

The

K

_g factor is given by formula (18) – IEC Std.:

G d rG

n

G

X

c U

K U

 sin

1

^"

max

 

(18, IEC 60909 Std.)

Where:

U

n - is the system rated voltage

U

rG- the generator rated voltage

"

X

d- generator sub transient reactance referred to generator rated impedance



G

sin

- generator phase angle between current and terminal voltage

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Apply Kt factor to network transformer Zt :

Users should check the above field if the short circuit occurs from a network transformer.

A network transformer (see the figure below) is when a transformer is connecting two or more networks at different voltages (IEC Std.). For two-winding transformers with and without on-load tap-changer, an impedance correction factor KT is to be introduced in addition to the impedance evaluated according to IEC (equation (7) to (9)).

T

T

X

K c

6 . 0 95 1 .

0

^max

 

Where,

X

_T is the relative reactance of the transformer and C_max is related to the nominal voltage of the network connected to the low-voltage side of the network transformer. This correction factor shall not be introduced for unit transformers of power station units (IEC, see 3.7). This factor is active only if the user selects the “Network Transformer (used in IEC 60909 method)” checkbox in the transformer editor, as shown below:

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Apply Adjust

Z

_tfactor by using actual tap:

If this option is selected, DesignBase adjusts

Z

_T by using actual transformer tap. In this case, the program considers the transformer impedance as a function of the transformer tap position.

If the 1988 IEC 60909 version is selected, the “c” factor values are provided by the program, as in table 3:

Table 3: IEC c factor

Low Voltage networks: 230/400V, 3P3W Other voltage levels, 3P3W

1.05 1.05

1 1 Low voltage networks: 230/400V, 3P4W

Other voltage levels, 3P4W

Above 1000 V: Per user selection per user selection

Low voltage networks: 230/400V, 3P3W/4W Other voltage levels 3P3W/4W

Above 1000 V: Per user selection per user selection

Other per user selection per user selection

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4 AC IEC 61363 SHORT CIRCUIT METHOD

IEC 61363 Standard calculates the short circuit instantaneous current as a function of time and displays its instantaneous values. The method provides an accurate evaluation of the short circuit current for sizing protective devices and coordinating relays for isolated systems (off-shore platforms and ships electrical design). The machine’s sub-transient reactance and time constants are used by this method. The Calculation Tab is similar to the AC ANSI/IEEE Standard and provides the same options.

DesignBase AC IEC 363 Short Circuit program tools are shown below:

Options

Report Manager

Back Annotation

Analyze

Generators are modeled by their positive sequence sub-transient reactance, and motors are modeled by their locked-rotor impedance. The sub-transient and transient time constants and dc time constants are also considered in the calculations.

This application allows users to display results in a standard report format, annotate results on the one line diagram, and plot short circuit results varying with time.

For this tutorial, open the IEC3632 sample file under the IEC363SC sample folder and then follow the steps below:

1. Launch the short Circuit program, by clicking on the short circuit program icon.

2. Select the “AC IEC 61363” analysis method, and then click on the “Options” icon to open the Short Circuit Analysis Basic Option window. The “Options” features are similar to the ANSI Method.

Click “OK”, and then open the Report Manager.

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As can be seen from the window above, Reports can be set to the following options:

 Fast

 User Defined

 Curve with Time Users can also see and modify:

 Input Report & Abbreviations: Input Data and Abbreviation.

 Report Style, Units & Log: Print Layout, Unit, View Log File.

The AC IEC 61363 Short Circuit program “Abbreviations” are displayed below:

If Fast Report is selected, the following dialog window will be displayed:

If User Defined Report is selected the additional “User Defined Output Options” will appear:

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Similarly to ANSI and IEC 60909 analysis methods, Fast or User Defined report allow users to select:

 Time Bands:

0 – cycle

½ - cycle 1 – cycle 3 – cycle 5 - cycle 8 – cycle 30 – cycle

 User defined output options:

Td –DC Time constant, in seconds

Iac –Short circuit AC symmetrical component, rms value Idc –Short circuit DC component

Ienv-Short circuit envelope

In order to display Short Circuit Results varying with time, Select Bus B1. Then, click on the “Report Manager” icon. Select “Curve with Time” and then click “OK”.

Click the analyze icon. The following graphs will be displayed:

Figure 7: IEC-61363 Short Circuit Chart

The following Short circuit components can be individually displayed or in combinations:

 Idc – dc component of SC Current

 iac – instantaneous ac component

 Ienv – Upper Envelope of Sc current

 I – Instantaneous total short circuit current

 Im – magnitude of ac component

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5 AC SINGLE PHASE SHORT CIRCUIT METHOD

The AC Single Phase Method is based on the Complex E/Z calculation method and the X/R ratio is extracted from the complex impedance matrix (X/R). The Calculation Tab is the same as in AC ANSI/IEEE Standard and provides the same options.

6 USING DESIGNBASE REPORT MANAGER

Open the ANSI-YY sample file located in the short circuit sample folder. All the following steps and explanations are applicable to AC Classical, ANSI/IEEE, and IEC-60909 short circuit analysis methods.

Launch the short circuit toolbar, and click on the report manager Icon The Report Manager provides:

 Output Reports: Fast, User Defined, PDE, Misc.

 Output Destination: output to CSV or output to Text File Fast Report:

Users can select “Fault Type”, “Time Bands”, Input Data, Abbreviation, Report Style, Unit & Log. If the fault is at one bus, the “Branch Contribution” option can be used.

Select the Fault Types as shown below: 3-P, L-G, L-L, LL-G. Time Bands ½ cycle.

Figure 8: Short Circuit Report Manager

Click “OK” and then run the program by clicking the “Analyze” icon.

The rms short circuit currents values at 1/2 Cycle are calculated at selected buses or at all buses depending on the bus selection (in the short circuit Options dialog or directly on the drawing).

The positive, negative, and zero sequence sub-transient reactance X” are used in modeling both the generators and motors. Motors are normally not grounded and therefore the grounding option should be none.

User Defined Reports:

It is similar to the “Fast Report”, but additionally users can select the Phase Bus/Branch Components: X/R, AC, DC, Asym, Angle.

In order to get a tabulated output report, proceed as follows:

 Select Output to CSV or Text File

 Click on “Browse” icon and assign the path and the file title

 Click “OK”

 Then click the “Analyze” icon on the short circuit toolbar

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An excel report will be generated under the DesignBase output folder as shown below.

Figure 9: Short Circuit Excel Report

Professional Report:

Open the report manager. Select “Fast” output report, ANSI Bus Summary and then click on “Professional Report Writer Wizard”.

The program will display the Report shown below:

Figure 10: Short Circuit Professional Report

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 Generator, motor, and transformer grounding types and winding connections are taken into consideration while building up the system positive, negative, and zero sequence networks

 The positive, negative, and zero sequence sub-transient reactance is used for modeling both the Generators and motors

 For steady short circuit, generators are modeled by their positive, negative, and zero sequence reactance

 Short circuit current contributions from motors are ignored in steady short circuit calculations

 The rms short circuit currents values after 30 cycles are calculated (as per ANSI/IEEE Standards or IEC 60909 Standard) at selected buses or at all buses based on user bus selection (in the short circuit Options dialog or directly on the drawing). The short circuit current contributions from motors are ignored, and the generators are modeled by their positive sequence transient reactance X’.

7 PROTECTIVE DEVICE EVALUATION (PDE) BASED ON ANSI/IEEE AND IEC-60909

Paladin DesignBase PDE is a fast and accurate tool which evaluates buses and protective devices such as:

LV, MV and HV CBs, fuses, and switches based on ANSI/IEEE and IEC Standards.

Some features of the PDE program are:

 Equipment operating voltage can be set to:

o Load Flow calculated Voltage o Actual Voltage

o System voltage

 The PDE program includes CB impedances and CB’s X/R ratio

 Equipment can be:

o Buses (ANSI only)

o Protective Devices (ANSI and IEC)

 Output results can be organized by:

o Equipment Input Rated Data o PDE Calculated Data o Circuit Duty calculated data

PDE output results are either graphically displayed onto the one line diagram (in green if the equipment passes or in red if they fail), or as a Text Report, based on user selection.

The fault study is per the Standard selected by the user: IEEE/ANSI C37 Standard or IEC 60909. The program calculates momentary symmetrical and asymmetrical rms, momentary asymmetrical crest, interrupting symmetrical rms, and interrupting adjusted symmetrical rms short circuit currents at faulted buses.

The circuit duties are checked against equipment interrupting capabilities, and if:

Intrr Equip Duty

Circuit

I

I

_{_}



_{._}

The equipment passes; otherwise it fails.

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Open the ANSI-YY sample file located in the short circuit sample folder. All the following steps and explanations are applicable to both the ANSI/IEEE and IEC-60909 short circuit analysis methods.

In the Short Circuit Analysis Basic Option, select “All buses”, default output “Report”, and then click “OK” as shown below:

If “Annotation” is selected as the “Default Output”, the PDE results will be displayed on the one line Diagram.

If “Max Branch Fault Flow” is selected under the “Duty Type for PDE”, protective device evaluation will be done based on branch short circuit current versus total bus fault current.

Note:

The “Total Bus Fault Current” method is the most conservative method. This option is present in both ANSI/IEEE and IEC-60909.

In the Report manager, select PDE:

Click “OK” and then run the short circuit program. The Protective Device Evaluation List shown below will be displayed:

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Notes:

 User can select evaluation of branches or buses by toggling the “List Equipment of type” field:

 In general Data error is displayed if:

o The equipment voltage is not equal or lower than the system voltage o The equipment voltage in the editor is zero

o The equipment short circuit ratings in the editor are zero or not consistent with their definitions.

 More details regarding equipment failing and data error can be seen under the “Detailed Report”:

Double click on breaker A10 in the equipment list. The Peak closing and latching current is 0 when it should be bigger than the 40 kA Asymmetrical current to be consistent. Change the Peak current to 50 kA and the data error message will disappear.

Click on “Summary Report” to display the summary report.

Figure 12: ANSI PDE Summary Report

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8 SHORT CIRCUIT BACK ANNOTATION

Short circuit results can be displayed on the one the one-line diagram by selecting “Annotation” in the short circuit Options.

To customize the annotation, click on the Short Circuit Back Annotation icon The Annotation window below will appear:

Figure 13: Short Circuit Annotation Window

Select the back annotation ON or OFF, Auto-refresh, Font, Font Style, size and font color for additional customizations.

Select this option to display the bus Pre-Fault Voltage

Select the color and font size

Select this option to display the Fault Branch Current

Select the unit Select this option to display

the Bus Sym.-Fault Voltage/

Residual Voltage

Fault Current to be displayed

Select this option to display the current flow arrows

9 MANAGING SCHEDULES IN SHORT CIRCUIT CALCULATIONS

Schedule is a Paladin DesignBase feature that allows users to combine several motors and loads in a single symbol.

Open the “SC_MCC_SCHEDULE” sample file under C:\DesignBase\Samples\3PhaseSC. The following networks are represented:

a) Model with each motor individually represented

b) Model with the three motors in a) combined inside a MCC schedule

Double click on the motor “MCC” symbol to see the motors representation inside the schedule.

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Figure 14: Motors inside schedule

Click on the “Prot Dev/Cable” button to see the cables associated with each motor.

Figure 15: Feeder Representation inside a Schedule

Click on the “Status” button to switch “ON” or “OFF” motors.

Figure 16: Motor Status inside a Schedule

Click on the “Usage” button to change each motor percent running.

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To display the schedule short circuit results onto the drawing and Report, click on the AC short circuit icon and follow the steps below:

Step 1: Select the “MCC” bus symbol.

Step 2: Open the Short Circuit Basic Option shown below:

Step 3: In the Report Manager select the “Fast” report, Fault Type, and Time Band shown below:

Step 4: Click the “Analyze” icon and the Short Circuit Results will be displayed onto the drawing:

Figure 18: Short Circuit at MCC bus and branch contributions

In order to see the detailed short circuit results for each motor inside the “Schedule”, proceed as follows:

Step 5: Open the Report Manager and select “Misc” then “MCC/Schedule.

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Step 6: Click “Analyze” icon. The fault results will be displayed as a “Text output Report”:

Phase B,C for Line-Line or Line-Line-Ground Fault

Classical Calculation:

Complex Z for X/R and Fault Current

Transformer Phase Shift is not considered.

Generator and Motor X/R is constant.

Base Voltages : Adjusted by Tap/Turn Ratio Prefault Voltages : Use System Voltages

Jobfile Name: SC_MCC_SCHEDULE

MCC Schedule Results Validation:

Perform short circuit calculation at bus “Motor Bus” and compare it to the results obtained previously at

“MCC”.

The fault results match in the both motor representation.

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10 NETWORK REDUCTION/EQUIVALENT

In document D H D F J , M P Concepto de género: de las teorías feministas a las políticas públicas Tesis Doctoral U S (página 174-182)