Contingency Analysis

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PSS SINCAL 6.5 Contingency Analysis Automatic Calculation of Contingencies and their Effects in Electricity Networks

Published by SIEMENS AG Freyeslebenstraße 1, 91058 Erlangen E D SE PTI SW

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PSS SINCAL Contingency Analysis Manual Preface

Preface The PSS SINCAL manuals can be divided into three parts: ● ● ●

the PSS SINCAL System Manual technical manuals for electricity and flow networks the database description

The user can find the general principles for using the PSS SINCAL manual and the PSS SINCAL user interface in the PSS SINCAL System Manual. The technical manuals for electricity networks contain detailed descriptions of the various calculation methods for electricity networks - such as load flow, or short circuit calculations - and their input data. The technical manuals for pipe networks contain detailed descriptions of the various calculation methods for pipe networks - water, gas and heating - and their input data. The database description contains a complete description of the data models for electricity and flow networks.

Copyright This manual and all the information and illustrations contained in it are copyrighted. SIEMENS retains all rights, in particular the right to publish, translate, reprint, photocopy, make microcopies or electronically store in a database. Previously expressed written permission from SIEMENS is required for any reproduction or use beyond the limits specified by copyright law.

Warranty Even though our manuals are thoroughly checked for errors, no liability can be taken for errors found or any resulting problems or difficulties. Modifications are frequently made to the text and the software as a part of our routine updates.

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PSS is a registered trademark of SIEMENS AG Copyright SIEMENS AG 2009 All Rights Reserved

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PSS SINCAL Contingency Analysis Manual Table of Contents

1.

Introduction to Contingency Analysis

1

2.

Contingency Analysis Calculation Method

2

2.1

Malfunctioning Elements

3

2.2

Determining Malfunctions

3

2.3

Evaluating Malfunctions

6

2.3.1

Violation Performance Indices (VPI)

6

2.4

Advantages to the Network Carrier

7

3.

Example for Contingency Analysis

8

3.1

Presetting Calculation Settings

9

3.2

Defining Malfunction Groups

11

3.3

Defining Function Groups

12

3.4

Performing the Contingency Analysis

13

3.4.1

Malfunction

14

3.4.2

Overloaded Elements

16

3.4.3

Details

16

3.5

Displaying and Evaluating the Results

17

3.5.1

Results in the Contingency Analysis Dialog Box

17

3.5.2

Results in Tabular View

18

3.5.3

Results in Reports

18

3.5.4

Coloring in the Network Diagram

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PSS SINCAL Contingency Analysis Manual

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Table of Contents

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PSS SINCAL Contingency Analysis Manual Introduction to Contingency Analysis

1.

Introduction to Contingency Analysis PSS SINCAL Contingency Analysis calculations are a series of load flow calculations. One or more elements malfunction and do not participate in individual load flow calculations. PSS SINCAL determines malfunctioning elements by network areas. The malfunction can be conditional or unconditional. PSS SINCAL displays all data relevant to the malfunction (minimum values, maximum values, unsupplied consumers, overloads, etc.) in the results. This manual contains the following chapters: ● ●

Contingency Analysis Calculation Method Example for Contingency Analysis

Contingency Analysis Procedure You never need special settings when you enter data for Contingency Analysis. The following steps are necessary: ● ●

Define the number of malfunctioning network elements in the network areas Define the voltage and load limits in the calculation settings for load flow

Contingency Analysis also checks for load current tripping.

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2.

Contingency Analysis Calculation Method The purpose of PSS SINCAL Contingency Analysis calculations is to evaluate load flow in distribution networks when the following elements malfunction: ● ● ●

Individual elements Elements that can operate only together (function groups) Overloaded elements

Load flow calculations for the entire network provide the basis of contingency analysis calculations. PSS SINCAL only uses elements supplied in this basic load flow to evaluate the network when one or more elements malfunction.

Contingency Analysis Calculation Procedure Calculate load flow of the complete network Determine malfunctioning elements Turn off malfunctioning element and operating group in load flow calculations

Network analysis and load flow calculations in remaining network

Determine minimum values, maximum values, unfed elements and loads

Store overloaded elements for caused malfunctions

Have all elements been observed?

No

Yes Prepare results Illustration: Sequence diagram

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PSS SINCAL Contingency Analysis Manual Contingency Analysis Calculation Method

2.1

Malfunctioning Elements Malfunctions are broken down into element types. Only elements of the following types can malfunction: ● ● ● ● ● ● ● ●

2.2

Lines Serial reactors Two-winding transformers Three-winding transformers Synchronous machines Asynchronous machines with load flow type DFIG Power units Static compensators

Determining Malfunctions PSS SINCAL recognizes the following types of malfunctions: ● ●

Basic malfunctions Caused malfunctions

Why the element failed is not important. PSS SINCAL always checks the malfunction of an individual element and its effect on the remaining network. This procedure is the same as checking the n – 1 criterion for the network. You can set parameters for contingency analysis individually for each network area. Use the Contingency Analysis tab to set which network elements will malfunction and whether this will generate caused malfunctions.

Illustration: Data screen form for Network Area – Contingency Analysis

The small network area below shows how contingency analysis functions in basic and caused malfunctions. The network area contains the lines L1 to L7.

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L2 L1

L3 L4 L5

L6 L7

Illustration: Network area for malfunction simulation

Basic Malfunctions Depending on the settings in the Contingency Analysis tab, basic malfunctions are either for ● ● ● ● ● ●

All elements Loaded elements All lines Loaded lines All lines and transformers Loaded lines and transformers

If there is no entry for load limit (e.g. if you use the All elements option), PSS SINCAL calculates one malfunction per line. Line L1 is switched OFF for the first malfunction.

L2 L1

L3 L4 L5

L6 L7

Illustration: Malfunctioning network elements without load limit (Malfunction 1 – Line L1)

For the next malfunction, Line L1 is switched ON again and Line L2 switched OFF. Then Line L2 is switched ON and Line L3 switched OFF. This repeats until all lines have failed. If you set a load limit, PSS SINCAL only calculates malfunctions for network elements whose load is greater than the preset load limit. The following diagram shows the base load after the line names. If you have set 75 % preliminary load setting, only Line L3 would malfunction, since this has a load of 79 %.

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L2 (62 %) L1 (60 %)

L3 (79 %) L4 (25 %)

L6 (47 %)

L5 (58 %) L7 (38 %)

Illustration: Malfunctioning network elements with a load limit of 75 % (one malfunction – one line)

Caused Malfunctions Caused malfunctions are always load-dependent. To investigate caused malfunctions, load flow must be calculated in the rest of the network after a basic malfunction. All elements that exceed the prescribed load limit in this load flow cause a new malfunction.

L2 (78 %) L1 (68 %) L6 (57 %)

L3 (89 %) L4 (42 %) L5 (67 %)

L7 L2 L3

… Basic malfunction … Caused malfunction 1 … Caused malfunction 2

L7

Illustration: Caused malfunctions with a load limit greater than 75 %

These two caused malfunctions have the following elements: ●

●

Caused Malfunction 1: Basic malfunction of line L7 Caused malfunction of line L2, because the load with 78 % is above 75 % Caused Malfunction 2: Basic malfunction of line L7 Caused malfunction of line L3, because the load with 89 % is above 75 %

Detailed parameters can be set for how PSS SINCAL generates caused malfunctions. You can select whether PSS SINCAL only generates caused malfunctions in their own network area or in all the network areas where you switched ON Marked for Caused Malfunction.

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Function Groups Function groups can be used to group any network elements that you choose. The following agreement is valid: all elements in an function group must always operate together. This means network elements grouped like this way always malfunction at the same time. In PSS SINCAL, the function group is built by the Network Element Group. In malfunction simulation, the use of function groups is optional. PSS SINCAL considers all entered function groups independent of whether there is a basic malfunction or a caused malfunction.

2.3

Evaluating Malfunctions The results of the contingency analysis are used to evaluate the results of different malfunctions. For this evaluation, PSS SINCAL provides the following results: ● ● ● ● ● ●

Number of unsupplied loads Number of limit violations for load and voltage Number of protection devices that trip (load flow tripping) Violation Performance Indices Minimum and maximum network voltage Maximum utilization

These statistics are used to for an in-depth evaluation of the different malfunctions. You can execute a detailed analysis for a specific malfunction at any time! PSS SINCAL will provide complete load flow results for this malfunction.

2.3.1

Violation Performance Indices (VPI) Violation Performance Indices are measurements used to evaluate limit violations. For each monitored current and voltage value, a violation performance index (VPI) is calculated. For each load flow case, the individual VPIs of all monitored branch currents and node voltages can be summed up to Total VPI(I) and Total VPI(V). Those total VPIs allow you to compare different load flow cases. The total VPIs are excellent sorting criteria for Contingency Analysis results.

VPI Calculation for Currents The limit used to determine the VPI for currents comes from the input data for network elements. The calculation is performed as follows:

VPI(I)

Weight(I)

Value(I) Limit(I)

2

Total VPI(I) = ∑ of all monitored VPI(I)'s

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VPI Calculation for Voltages The limit used to determine the VPI for voltages is taken from the Load Flow Calculation Settings. The calculation is as follows: Lower Limit (V)

Upper Limit (V)

Nom (V)

Ref (V) dMax (V)

dMax (V)

Value (V)

where Re f ( V ) dMax( V )

0.5 (Upper Limit( V ) Lower Limit( V )) 0.5 (Upper Limit( V ) Lower Limit( V ))

then the required values are:

VPI( V )

Weight( V )

Value( V ) Re f ( V ) dMax( V )

2

Total VPI(V) = ∑ of all monitored VPI(V)'s

2.4

Advantages to the Network Carrier Malfunction simulation provides network carriers with information on the reliability and deficiencies in the network. The carrier gets important network information on: ● ● ● ● ● ●

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n – 1 criteria for network operation Breaks in supplies Overload conditions during network element malfunctions Impossible network conditions during network element malfunctions Priorities of network development measures Influences on consumer contractual agreements

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3.

Example for Contingency Analysis Below is a simple example of how Contingency Analysis works. The following descriptions show: ● ● ● ● ●

Presetting Calculation Settings Defining Malfunction Groups Defining Function Groups Performing the Contingency Analysis Displaying and Evaluating the Results

Basic Data All descriptions are based on the following network:

Illustration: Example network for contingency analysis

When PSS SINCAL is installed, it automatically provides a network ("Example Ele"), which can be used to check the simulation procedure.

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PSS SINCAL Contingency Analysis Manual Example for Contingency Analysis

3.1

Presetting Calculation Settings PSS SINCAL assigns individual network elements to a precise network area. PSS SINCAL Contingency Analysis calculations can be done for any network area. Click Insert – Network Area… in the menu to open the Network Area data screen form and enter the initial setting.

Illustration: Data screen form for Network Area – Contingency Analysis

You can set control parameters in the Contingency Analysis tab. Marked for Caused Malfunction regulates the scope of caused malfunctions. When you switch this option ON, PSS SINCAL generates caused malfunctions for this network area assuming selected network areas has been selected in the Caused Malfunction field. If this option is not switched ON, PSS SINCAL will not generate caused malfunctions for this network area. Malfunction turns the elements in the network area ON and OFF or checks them for the contingency analysis. ● ● ● ● ● ● ●

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None: No elements malfunction. All elements: All elements malfunction. Loaded elements: All elements malfunction if their Utilization Limit has been violated. All lines: All lines malfunction. Loaded lines: All lines malfunction if their Utilization Limit has been violated. All lines and transformers: All lines and transformers malfunction. Loaded lines and transformers: All lines and transformers malfunction if their Utilization Limit has been violated.

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Consider Connectors switches the connectors of the network area for the contingency analysis ON or OFF. ● ●

Yes: Connectors are considered. No: Connectors are ignored.

The Caused Malfunction field regulates the number of caused malfunctions in the network areas. ● ●

●

None: No caused malfunctions are generated. Marked areas: Caused malfunctions for network areas are only generated, if Marked for Caused Malfunction is selected. Own area: PSS SINCAL only generates caused malfunctions for the current network area.

How many elements for caused malfunctions PSS SINCAL actually considers can also be set with the Caused Elements field. ● ● ●

Loaded elements: All malfunctions caused by overloaded elements. Loaded lines: Malfunctions caused by overloaded lines. Loaded lines and transformers: Only malfunctions caused by overloaded lines and transformers.

There is an additional contingency analysis for elements where the Caused Utilization Limit is exceeded where original and the presently overloaded elements fail together. Show Limits sets parameters for the scope of the results in malfunction analysis. ● ●

● ●

● ●

●

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None: No overloaded elements are documented. Elements and nodes: All elements are documented that exceed the preset lim it. PSS SINCAL logs all nodes if their voltage is outside the prescribed voltage limits. Elements: All elements are documented that exceed the preset limit. Lines, transformers and nodes: All lines and transformers are documented that exceed the preset limit. PSS SINCAL logs all nodes if their voltage is outside the prescribed voltage limits. Lines and transformers: All lines and transformers are documented that exceed the preset limit. Lines and nodes: All lines are documented that exceed the preset limit. PSS SINCAL logs all nodes if their voltage is outside the prescribed voltage limits. Lines: All lines are documented that exceed the preset limit.

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3.2

Defining Malfunction Groups If you want to have multiple elements malfunction together for contingency analysis, use Malfunction group to assign them to a network element group. Simply select these elements in the network diagram and switch them ON with Insert – Network Element Group… in the menu. Then click New Group in the following dialog box.

Illustration: Creating a new group

Enter the name and select Malfunction group as the type of group in the data screen form. Then press OK to create the new group. Add Selection assigns all selected elements to the new group.

Illustration: New network element group with assigned network elements

All elements of a network element group with the Malfunction group type cause their own malfunction in Contingency Analysis.

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3.3

Defining Function Groups If elements are only able to operate in conjunction, use Function group to assign them to a network element group. Simply select these elements in the network diagram and switch them ON with Insert – Network Element Group… in the menu. Then click New Group in the following dialog box.

Illustration: Creating a new group

Enter the name and select Function group as the type of group in the data screen form. Then press OK to create the new group. Add Selection assigns all selected elements to the new group.

Illustration: New network element group with assigned network elements

If only one network element in a function group malfunctions because of the malfunction amount defined in the network area data, all the other network elements in this group also malfunction automatically at the same time.

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3.4

Performing the Contingency Analysis To start PSS SINCAL Contingency Analysis calculations, click Calculate – Load Flow – Contingency Analysis in the menu. If there are no errors in the simulation and network areas have been switched ON for the contingency analysis, PSS SINCAL automatically opens the Contingency Analysis dialog box when the calculations are finished.

Illustration: Contingency Analysis dialog box

You can click Calculate – Results – Contingency Analysis in the menu at any time to open this dialog box. The Contingency Analysis dialog box has two parts. You can select either Overview of the malfunctions or Overloaded elements in the part at the top. The bottom part provides the details for the malfunction you have selected. Click Calculate to turn load flow calculations ON where PSS SINCAL calculates the selected malfunction in detail. PSS SINCAL displays the results of these load flow calculations in the network diagram so you can observe the malfunction more closely.

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3.4.1

Malfunction The Filter field, assigns a temporary filter for the malfunctions. Assigning a filter immediately reduces the amount displayed in the attached list of options. A special feature of the input field is the control button in the input field. If you click it, it displays a menu.

Illustration: Menu to select the display

The menu has the following functions that let you customize how the list of options is displayed. ●

● ●

●

Filter: An additional dialog box is opened where the data in the dialog box can be filtered and sorted according to various criteria. For a detailed description, see the section on Filter Functions in Tabular View in the chapter on Tabular View in the System Manual. Disable Filter: A filter can be temporary deactivated, displaying all the data again. Simple: Malfunctions are displayed flat and all malfunctions and caused malfunctions are displayed in a single layer. Hierarchically: Malfunctions are displayed in a structured manner, i.e. caused malfunctions are displayed under the malfunction that caused them.

The Malfunction list has the results of the contingency analysis. The list shows the network element that has malfunctioned and additional information on the malfunction (number of unfed loads, etc.). Click on a malfunction in the list of options with of the right mouse button to open the pop-up menu with the following functions: ● ● ●

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Details: Opens the data-output form for the malfunction. Select: Highlights the selected malfunction in the network diagram. Calculate: Starts load flow calculations for the selected malfunction.

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Details of Malfunction When you click Details… in the pop-up menu for an entry in the list, this opens the detailed data output form for the malfunction.

Illustration: Data screen form for Contingency Analysis Results

This dialog box has detailed information on the malfunction. Malfunction Key and Base Malfunction Key identify the malfunction. If it is a secondary malfunction, the malfunction that caused it is entered as a basic malfunction key. Number of Limits Reached, Number of Voltage Limits Reached and Number of Loading Limits Reached have the number of limit violations for the malfunction. Number of Tripping Devices shows how many protection devices trip during this malfunction due to load currents. Total Voltage VPI and Total Current VPI show total values of the Violation Performance Indices (VPI) for current and voltage. Minimum Voltage and Maximum Voltage have the minimum and maximum tensions in the network for this malfunction. Maximum Loading has the highest load for a network element for this malfunction. Maximum Factor Ext. Calculation shows the highest factor from the extended calculation at a node. Number of Not Supplied Loads shows how many consumers are not supplied due to this malfunction. Load Flow Solved shows whether PSS SINCAL will calculate the network after the malfunction.

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3.4.2

Overloaded Elements The Filter field assigns a temporary filter for the malfunctions. Assigning a filter immediately reduces the amount displayed in the attached list of options. Overloaded elements lists elements that are most critical for the respective malfunction. The list includes the overloaded element, the malfunction causing the overload and additional information on the malfunction (the number of unsupplied loads, etc.). The list of options can either have an overview of all the overloaded elements or a more detailed view for a definite element with all the malfunctions. If you reduce the amount PSS SINCAL displays in the overview to a single overloaded element, this changes the list of options in the detailed view. Double-click on an entry to change this for the selected element. Click on a malfunction in the list of options with the right mouse button to open the pop-up menu with the following functions: ● ● ●

3.4.3

Details: Opens the output form for the malfunction. Select: Highlights the selected malfunction in the network diagram. Calculate: Starts load flow calculations for the selected malfunction.

Details These are enhanced functions for the selected malfunction. The list displays all the nodes and elements of the malfunction. PSS SINCAL provides the following display options: ●

●

●

Limit reached: PSS SINCAL displays nodes where the voltage is above or below the predefined limit. PSS SINCAL also lists any network elements that exceed the limits (e.g. any elements that are overloaded). Not fed: PSS SINCAL displays the nodes and network elements that are not supplied due to the malfunction. Malfunction: PSS SINCAL displays all the nodes and network elements that are malfunctioned (if function groups are used this can also be multiple nodes or network elements).

You can assign a temporary filter for detailed information of the selected malfunction in the Filter field. When you assign a filter, PSS SINCAL immediately reduces the amount displayed in the attached list of options. A special feature of the input field is the control button in the input field. If you click it, it displays a menu.

Illustration: Menu to select the display

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The menu has the following functions that let you customize how the list of options is displayed. ● ● ●

All: PSS SINCAL lists both the nodes and the network elements of the malfunction. Nodes: PSS SINCAL only lists the nodes of the malfunction. Elements: PSS SINCAL only lists the network elements of the malfunction.

Click the right mouse button on elements in the list to open the pop-up menu with the following functions: ● ●

Edit: Opens the data input form for the selected elements. Select: Highlights the selected elements in the network diagram.

Click Details… to open the screen form with the results for the selected malfunction. Click Start Evaluation to display the malfunction in colors in the Graphics Editor. To remove the colored marking in the Graphics Editor, click the End Evaluation button. Click Select to highlight the network elements of the malfunction in the network diagram that you have selected in the dialog box. PSS SINCAL highlights the nodes and network elements according to the display option selected. ● ● ●

3.5

Limit reached: Highlights all network elements that exceed the limit. Not fed: Highlights all network elements not supplied due to the malfunction. Malfunction: Highlights the network element leading to the malfunction in the network diagram.

Displaying and Evaluating the Results PSS SINCAL provides the results of the contingency analysis in various forms for different kinds of analyses and evaluations: ● ● ● ●

3.5.1

Results in the Contingency Analysis Dialog Box Results in Tabular View Results in Reports Coloring in the Network Diagram

Results in the Contingency Analysis Dialog Box For information on the representation and analysis of the results, see the chapter on Performing Contingency Analysis.

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3.5.2

Results in Tabular View The results of the contingency analysis – the data for the malfunction and the details – are available in Tabular View. Click View – Tabular View in the menu to open this screen form.

Illustration: Tabular View with results of the contingency analysis

Use the browser in Tabular View to select among the following results: ● ● ●

3.5.3

Network results Node results Branch results

Results in Reports The results of the contingency analysis are available as reports. Click File – Print Report… in the menu to open the Print Report dialog box.

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Illustration: Print Report dialog box

The reports for the contingency analysis can be found in the list of options for available reports under the item Results – Load Flow. For a detailed description of how to use this dialog box, see the chapter on Reports in the System Manual.

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3.5.4

Coloring in the Network Diagram Network elements in the network diagram can be colored. Select the desired malfunction in the Contingency Analysis dialog box. The dialog box closes.

Illustration: Contingency Analysis dialog box

Click View – Evaluation Settings… in the menu to open the dialog box for coloring the network.

Illustration: Evaluation dialog box

For a detailed description of how to use this dialog box, see the section on Evaluations in the chapter on Displaying Input Data and Results in the System Manual.

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Illustration: Coloring to show results

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Contingency Analysis

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