Motor Starting e Tap

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Run Dynamic Motor Starting

Click this button to perform a time-domain simulation for starting and/or switching off motors and staticloads. Accelerating motors are modeled dynamically for this study; therefore, related motor parameters

such as dynamic model (or LR model for synchronous motors), inertia, and starting load must be specified.Motors (induction and synchronous) and static loads can be switched off and on in any event created.

Run Static Motor StartingClick this bu tton to perform a tim e-domain simulation for starting and/or switching off motors and static loads. For this s tudy, starting motors are

modeled as constant impedance loads calculated from their locked-rotor currents with a user-def ined acceleration time. Required parameters for

thi s study include the locked-rotor current and power fac tor, acceleration t ime at n o-loa d and full-load, and starting load .

Motors (induction and synchronous), MOVs, and static loads can be switched off and on in any eventcreated.

Display OptionsClick this button to customize the information and results annotations displayed on the one-line diagram inMotor Starting mode.

Alert ViewClick this button to bring up Motor Starting Analysis Alert View, which lists all critical and marginal alertsfor a study based on the set up in the Alert page of the study case used.

Report ManagerMotor acceleration output reports are provided in Crystal Reports. The Report Manager provides four

pages (Complete, Input, Result, and Summary) for viewing the different parts of the output report for bothtext and Crystal Reports. Available formats for Crystal Reports are displayed in each page of the ReportManager for motor starting (dynamic and static) studies.

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Crystal Reports formatted reporting is activated by choosing a format in the Report Manager. You canopen the whole study output report or only a part of it, depending on the format selection. You can view

the report in the Crystal Reports viewer, or save the report in PDF, MS Word, Rich Text Format, or Excelformat. If you wish this selection to be the default for reports, click the Set As Default check box.

You can also view output reports by clicking the Output Report button on the Study Case toolbar. A list of all output files in the selected projectdirectory is provided for motor starting calculations. To view any of the listed output reports, click the output report name, and then click the List

Output Report button.

Motor Starting PlotsTo view plots of accelerated motors, click this button to bring up a dialog box to select motors from a drop-down list.

Halt Current CalculationThe Stop Sign button is normally disabled. When a motor acceleration calculation has been initiated, thisbutton becomes enabled and shows a red stop sign. Clicking this button will terminate the current

calculation. One-line diagram display will not be available if you terminate the calculation before itcompletes; but the output report and plots do store the calculation results up to the time when you terminate

the calculation.

Get On-Line DataThis button is active when the ETAP Real-Time Advanced Monitoring is online. Click on this button touse real time data as initial conditions for this analysis.

Get Archived DataThis button is active when the ETAP Real-Time Event Playback is online. Click on this button to usearchived data as initial conditions for this analysis.

Time Slider Toolbar

Motor Starting Time-SliderOnce a motor starting study is completed, the Motor Starting Time-Slider, as shown below, will appear

next to the Configuration & Mode Toolbar. The slider ranges from zero to the total simulation time.Initially, the reference pointer is at the far left, corresponding to t = 0 seconds. You may click on either endof the ruler to move the pointer one grid at a time, or hold the mouse button down to move the pointercontinuously. You may also click on the pointer, hold the mouse button down, then drag the pointer to the

Motor Starting Analysis Toolbars

- Time Slider Toolbar Study Case Editor - Info Page

- Event Page - Add Action by Starting Category - Add Action by Load

- Model Page - Adjustment Page

- Alert Page Display Options

Motor Starting Plots - Plot Display Motor Starting Calculation Methods - Motor Starting Required Data Motor Starting Output Reports One-Line Diagram Display

Alert View





desired position. The time corresponding to the pointer position is also displayed next to the ruler in unitsof seconds. As you move the pointer along the slider, the displayed results change accordingly, providingyou with a quick way to examine the calculation results.

Study Case Editor - Motor Starting AnalysisThe Motor Starting Study Case editor contains solution control variables, prestart loading conditions,motor starting events, and a variety of options for output reports. The study case is used for both dynamic

and static motor acceleration studies.

ETAP allows you to create and save an unlimited number of study cases. Motor starting calculations are

conducted and reported in accordance with the settings of the study case selected in the toolbar. You canswitch between study cases without resetting the options each time. This feature is designed to organizeyour study efforts and save you time.

As part of the multi-dimension database concept of ETAP, study cases can be used for any combination of

the three major system toolbar components (configuration status, one-line diagram presentation, andBase/Revision Data).

The Motor Starting Study Case editor can be accessed by first selecting the Motor Starting Analysis Modefrom the Status/Mode toolbar, then clicking the Study Case button from the Motor Starting toolbar. Youcan also access this editor from the Project View by clicking the Motor Starting Study Case folder.

To create a new study case, go to the Project View, right-click the Motor Starting Study Case folder, andselect Create New. The Motor Acceleration module will then create a new study case, which is a copy of

the default study case, and adds it to the Motor Starting Study Case folder.

Motor Starting Analysis Toolbars - Time Slider Toolbar Study Case Editor

- Info Page - Event Page - Add Action by Starting Category

- Add Action by Load - Model Page

- Adjustment Page - Alert Page Display Options

Motor Starting Plots - Plot Display Motor Starting Calculation Methods

- Motor Starting Required Data Motor Starting Output Reports One-Line Diagram Display Alert View



- Event Page







and Adaptive Newton-Raphson. Choose solution control values for the load flow and motor startingsolutions as well as the plot resolution.

Max. IterationThis value determines the maximum number of iterations ETAP can make while solving the load flowequations. This means that the load flow should quit if it has not converged after the number of iterations

you specify here. Since dynamic and static motor starting calculation methods use the Newton-Raphson

algorithm, typical systems are solved within two to three iterations. We recommend choosing a minimumof five iterations. If the solution does not converge, you may want to increase this number, as well as

decrease the value you have specified for precision.

PrecisionThe load flow algorithm works by an iterating procedure until the motor loads it calculates for each busmatch the motor loads which are scheduled for each bus. The difference is called system mismatch.Solution Precision tells ETAP how many mismatches are allowed for a solution to be considered valid.When the mismatch for the motor MW and Mvar on each individual bus is below the value you enter forprecision, ETAP halts the load flow solution and declares that the solution has converged. Try using a

value of 0.001 to begin. If your system will not converge, try increasing this value incrementally (forexample, to 0.005, etc.) until it converges.

Simulation Time StepEnter the simulation time step for motor starting calculations. The recommended simulation time step is

0.001 second. If the simulation time step is too small, accumulation of the round off errors can causeinaccurate results. On the other hand, if this value is too large, calculation results may not capture thedynamic characteristics corresponding to very small time constants of the control equipment or system.

Plot Time StepThis value determines how often ETAP should record the results of the simulation for plotting. Forinstance, if you specify 20 steps, ETAP will plot points at every 20 X simulation time step (for example,for a simulation time step of 0.001 plot time step will be .02 seconds). The smaller this number is, thesmoother your plots will look, but also remember that the plot files on your hard disk may grow quite large.

The main thing to keep in mind is that ETAP records plot information at this interval throughout thesimulation. So if you specified a simulation time step of 0.001 seconds, plot time step of 10, and a total

time of 20 seconds, ETAP will write 20/(0.001*10)= 2000 points to disk, which is a large plot file.

Apply XFMR Phase-ShiftSelect this option to consider transformer phase-shift in load flow calculations. The phase-shift of atransformer can be found in the Transformer Editor.

Prestart Loading CategoryThis option allows you to specify how the system is loaded prior to starting any motors and/or switching onany static loads. You can select prestarting loads by loading categories or from operating load.

Loading CategorySelect one of the ten loading categories for prestart loading in the motor starting study case. With theselection of any category, ETAP uses the percent loading of all motors and other loads as specified for thatcategory.

Note: You can assign loading to each one of the ten categories from the Nameplate page of the Motoreditors and the Loading page of the Static Load editors.

Operating P, QThis option is enabled only if your installation of ETAP has the on-line feature (Real-Time module). When

this option is selected, the operating load will be used as the prestart load instead of the loading category.

Prestart Generation CategoryThis option allows you to specify how the generators and power grids are operating prior to starting anymotors and/or switching on any static loads. You can select prestarting generation by generation categories





or from operating values.

Generation CategorySelect one of the 10 generation categories for prestart generation. With the selection of any category,ETAP uses the generation values as specified for that category in the Rating page of a generator or a powergrid. Depending on the operating mode of the source, the generation values may include voltage magnitude

and angle, real and reactive power, or power factor.

Operating P, Q, VWhen this option is selected, the operating values will be used as the prestart generation instead of thegeneration category.

Note: The operating values for a generator or a power grid can be entered from the Rating page of its editoror be updated automatically from a load flow calculation.

Prestart Charger LoadingThis group allows you to select the charger loading source.

Loading CategoryWhen this option is selected, the load from the category specified in the Category field will be used tocalculate the charger load for the prestarting load flow.

Operating LoadWhen this option is selected, the charger operating load will be used for the prestarting load flow.

Note: The charger operating load is updated from DC load flow studies when the Updating Charger Load

option has been selected in the DC Load Flow Study Case.

Load Diversity FactorThis group allows you to specify load diversity factors to be applied on the loading category load. When

the Operating Load is selected, no diversity factor is considered.

NoneSelect this option to use the percent loading of each load as entered for the selected Loading Category.

Bus MaximumWhen this option is selected, all motors and other loads directly connected to each bus will be multiplied

by the bus maximum diversity factor. Using this option, you can simulate load flow studies with each bushaving a different maximum diversity factor.

This study option is helpful when the future loading of the electrical system has to be considered and eachbus may be loaded at a different maximum value.

Bus MinimumWhen this option is selected, all motors and other loads directly connected to each bus will be multipliedby the bus minimum diversity factor. Using this option, you can simulate load flow studies with each bus

having a different minimum diversity factor.

GlobalEnter the diversity factors for all constant kVA, constant Z, constant I, and Generic loads. When you selectthis option, ETAP will globally multiply all loads of the selected category with the entered load diversity

factors according to load types.

Note: A motor load-multiplying factor of 125% implies that the motor loads of all buses are increased by

25 percent above their nominal values. This value can be smaller or greater than 100 percent.

Report





Bus Voltage in PercentPrints Calculated bus voltages in the output report as a percentage of the bus nominal voltages. Forinformation about graphical display of bus voltages, see Section 21.3, Display Options.

Bus Voltage in kVPrints Calculated bus voltages in the output report in kV. For information about graphical display of bus

voltages, see Section 21.3, Display Options.

Skip Tabulated PlotsCheck to skip generating tabulated plots for the output report. This will significantly reduce calculationtime.

Study RemarksYou can enter up to 120 alphanumeric characters in this remark box. Information entered here will be

printed on the second line of every output report page header. These remarks can provide specificinformation regarding each study case.

Note: The first line of the header information is global for all study cases and entered in theProject Information Editor.

Time Event Page - Motor Starting Study Case Editor

ETAP allows you to set up unlimited number of events to simulate switching actions in a single Motor

Starting simulation. You can start or switch off individual loads or categorized motor groups with theAction by Load and Action by Starting Category features, respectively. You can also change the operatingload by clicking the Load Transitioning option to change from one loading category to another.

Motor Starting Analysis

Toolbars - Time Slider Toolbar Study Case Editor

- Info Page - Event Page - Add Action by Starting Category - Add Action by Load

- Model Page


Motor Starting Plots - Plot Display Motor Starting Calculation Methods - Motor Starting Required Data

Motor Starting Output Reports One-Line Diagram Display Alert View





You can start or switch off multiple loads by starting category and/or by individual load.

Note: The Motor Acceleration module assumes that all In Service loads are operating, except for the loadsthat are started or switched off in time events.

If you start an already running load, ETAP will ignore the second starting action. If you switch off analready switched off load, ETAP will ignore the second switch off action.

Note: You can specify conflicting actions on a motor during the same time event by using the Action byStarting Category and Action by Load options. In such an event, the Motor Acceleration module checks theaction specified by Action by Load first, and then checks the Action by Category event. The first valid

action gets executed in the simulation and the rest are ignored.

EventsThe Events Group lists all the events you specified in the study case according to their time of occurrence.The active events are flagged by a “*” sign and are listed before inactive events. In the calculation, onlyactive events are simulated. For each event, it displays the event name and the time of occurrence. Whenyou click an event from the list, all the actions defined for the event are displayed in the other groups onthe page.

You may Add, Edit or Delete an event by clicking the corresponding buttons.

Add

When you click the Add button, it brings up the Event Editor for you to add a new event.

Active

Select this option to activate the event. When an event is inactive, it will not be considered in the motor





starting calculations.

Event IDEnter a name for the event. It can be an alphanumeric string up to 12 characters. This name does not haveto be unique, but it is suggested to use a unique name for each event within a give study case.

Time

Enter the time for each time event in seconds.

Note: ETAP lists events in the order of the time defined here.

EditWhen you click the Edit button while an event is selected from the Events list, it brings up the Event Editor

with all the information for the event for you to modify. For description of the Event Editor, see the AddSection above.

DeleteWhen you click the Delete button while an event is selected from the Events list, it removes the events andassociated actions from the study case.

Note: All changes, including removing an event, will not take effect until you click the OK button or

navigate to another study case.

Total Simulation TimeTotal Simulation Time is the amount of time, in seconds, that you want the simulation to run. For instance,let's say you set up the following scenario:

t1 = 0.00 Nothing happens during this time eventt2 = 0.10 Start motor Mtr10 and switch on static load Stat2 on bus 20t3 = 0.20 Switch off Mtr8 on bus 10

Total Simulation Time = 2.00

This simulation will go as follows: at time t1 = 0, ETAP will run a load flow, using the prestart loading youselected, to find the initial conditions of the system. At time t2 = 0.1 seconds, ETAP will begin accelerating

motor Mtr10 and switch on static load Stat2 on bus 20. At time t3 = 0.2 seconds, ETAP will switch off themotor Mtr8 on bus 10. The simulation will continue for 1.8 more seconds, until time T = 2.0 seconds, whenthe simulation ends and the plots and summary reports are generated. As you can see, the total time must

be greater than your last event time.

Action by ElementThis feature allows you to switch on/off any existing motor or static load or change generation category of

a generator/power grid in a time event. The list of loads and sources that have been selected is displayed inthe Action by Load list box.





AddTo add a switching action for a motor, MOV, static load, generator, or power grid, click the Add button to

open the Add Action By Element editor. This editor allows you to add and/or modify a motor, MOV, staticload, generator, or power grid specifications, such as start/switch off, starting categories and generationcategories. Click the OK button and the specifications of the selected elements will be displayed in the

Action by Element list box.

Element TypeMotor Starting studies simulate switching of three types of loads: induction/synchronous motor, static load

and capacitor, and MOV. ETAP also simulates change of generation category for a generator or a powergrid.

ActionSelect this option to switch/stop motor, switch on/off a static load or a capacitor, start an MOV, or change

generation category for a generator or a power grid. If you start an already running load, ETAP will ignorethe second starting action. If you switch off an already switched off load, ETAP will ignore the secondswitch off action.

Note: ETAP assumes that all In Service loads are operating, except for the loads that are started or

switched off in time events.

Motor, Load, MOV, Generator

IDSelect an element ID from the drop-down list. The content in this list varies according to element typeselected. For motor load, it contains all induction and synchronous motors; for static load, it contains all

static loads and capacitors; for MOV, it contains all the MOVs; and for Gen/Power Grid, it contains all the





generator and power grids in the system.

Starting CategoryWhen Motor is selected from Element Type, this field shows up for you to specify a predefined startingcategory from the list box. This list box contains all ten motor starting categories. Information for startingcategories can be defined in the Start Cat page of Induction and Synchronous Motor editors, including

starting and final loading percent, as well as begin and end time of load change. When starting a motor by

element, you do not need to select the Starting Category option to use the loading and time data defined forthe starting category.

Note: The starting category is not applicable to static loads.

Loading CategoryWhen Static Load is selected from Element Type and the selected action is Switch On, this field shows upfor you to specify a predefined loading category from the drop-down list. This list contains all ten loadingcategories. The loading percent of the specified loading category, as defined in the Loading page of StaticLoad Editor, will be used to determine the amount of load to be switched on.

Generation Category

When Gen/Power Grid is selected from Element Type, this field shows up for you to specify a predefinedgeneration category from the list box. This list box contains all ten generation categories. Thegenerator/power grid operating data from the selected category, as defined in the Rating page of

Synchronous Generator Editor or Power Grid Editor, will be used to simulate its operating condition.

EditTo edit an action, click its action item and then click the Edit button. The Edit button opens the Edit ActionBy Element editor. This editor allows you to modify the data. The options in this editor are the same asthose for the Add Action by Element editor. For information about the Add Action by Element editor, seethe Add Section above.

Delete

To delete an action from the Action by Element list, select the element by clicking its action item and thenclick the Delete button. The selected load will be removed from the action list.

Action by Starting CategoryThis feature allows you to start motors by predefined motor starting categories.

Note: Motor starting categories can be defined in the Start Cat page of the Induction Motor, SynchronousMotor, and MOV editors. The selected motor groups are displayed in the Action by Starting Category list

box.

Add

To start or switch off a predefined group of motors, click on the Add button to open the Add Action ByStarting Category editor. This editor allows you to add and/or modify motor group specifications, such as

start/switch off, starting categories, and connected bus IDs. Click the OK button and the specifications ofthe motor groups selected in this editor will be displayed in the Action by Starting Category list box.





ActionSelect Start or Switch Off for the selected motor group. If you start an already running load, ETAP will

ignore the second starting action. If you switch off an already switched off load, ETAP will ignore thesecond switch off action.

Note: ETAP assumes that all In Service loads are operating, except for the loads that are started in timeevents.

By Category

Starting CategorySelect a predefined starting category from the list box. This list box contains all ten motor startingcategories. Motor starting categories can be defined in the Start Cat page of Induction and SynchronousMotor editors.

Bus ID

Select a bus ID to define the motor starting group from the drop-down list. This list contains all bus IDscreated for the electrical system under study. In addition, you can choose Start or Switch Off for all busesdefined by a starting category by selecting All Buses from the Bus ID list.

EditTo edit a selected group of motors, click its action item and then click the Edit button. The Edit button

opens the Add Action By Starting Category editor. This editor allows you to modify the data. Forinformation about the Add Action by Element editor, see the Add Section above.

DeleteTo delete a motor group from the Action by Starting Category listing, select the motor group by clicking itsaction item, and then click the Delete button. The selected motor group will be removed from the action

list.

Action by Load TransitioningThis feature allows you to change operating load from one loading category to another. In changing theloading category, if a motor load is changed from a zero percent to a non-zero percent load, it will create anaction to start the motor. However, once a motor is started by an action from Load Transition, the LoadTransition option will not apply to the motor anymore. Furthermore, once a load, including motors, staticloads, and capacitors, has been switched on or off through Action by Load or Action by Starting Category,

the Load Transition option will not apply to this load from that point on.







Transformer LTC

Include Automatic ActionIn this group you can specify the transformer LTC feature to be simulated in motor starting studies.

For Prestart Load Flow

If this option is selected, automatic voltage regulation actions and LTCs of transformers, if there are any,will be simulated in the prestart load flow calculation.

During & After Motor Acceleration

If this option is selected, LTCs of transformers, if there are any, will be simulated in calculations after the

prestart load flow.

Time DelayDuring motor starting, the Motor Acceleration module will check the voltages of the LTC regulated buses

and set up an internal clock with a time delay. If a voltage is out-of-range and stays out-of-range, at the endof the initial delay time (Ti), the module will check the voltage again and decide whether to reset the clockor initiate an LTC tap adjustment. In the latter case, it will take a time duration equal to the operating time

(Tc) to complete the LTC tap change. This process will continue until the final voltage falls within theregulating range or the LTC has reached its limits.In this group you specify the LTC time delay used in the calculation. The information in this group isapplied in the study only when the During & After Motor Acceleration option is selected.

Use Individual LTC Time DelayIf this option is selected, the initial time delay and the operating time entered in the individual transformereditor will be used in the calculation.





Use Global Time Delay

When this option is selected, the values entered in the Initial Time Delay and Operating Time fields will beused in the calculation. This means that all of the LTCs in the system will assume the same initial time

delay and operating time.

Initial Time Delay

In this field you can enter the global initial time delay in seconds.

Operating Time

In this field you can enter the operating time in seconds.

Starting Load of Accelerating MotorsIn the motor acceleration calculations, the difference between the motor torque and the load torque changesthe motor speed. In ETAP, the load torque model is specified as torque in percent as a function of

normalized motor speed. This load torque may be based on motor electrical rating or on mechanical load.In this group, you indicate to the Motor Acceleration module which base you want to use.

Based on Motor Electrical RatingWhen this option is selected, it is assumed that the load torque model you selected in the Motor editor onlyrepresents the shape of the load as a function of speed. The load torque values will be adjusted so that atthe synchronous speed the torque is equal to 100%. This means that, with the modified load curve, themotor will consume the rated electrical power at 100% starting load, under the rated voltage and at therated speed. When this option is selected, the torque base used to construct load torque model has no effect

on calculation results.

Based on Motor Mechanical LoadWhen this option is selected, it is assumed that the load torque model you selected in the Motor editorrepresents the actual load based on rated output torque. The load curve will be applied as it is without any

adjustments.

To illustrate the implication of this selection, consider a mo tor that has a start load of 50% and rated outputtorque Tr. On the Load page of the motor, the load torque curve is Model 1 given below, which has a loadtorque of 80% at operating speed and the curve is based on Tr.

Motor Load Model Curves

Model 1 : Load @ Rated Speed < 100% Model 2: Load @ Rated Speed = 100%

Case 1: Load Model Based on Motor Electrical Loading

In this case, the load torque curve will be shifted so that the torque at rated speed is 100% of the motorrated torque. This means that the torque at each point on the load curve will be multiplied by a factor of

1.25 (equal to 1/0.8). This modified the curve will be used as the load torque curve for the study. Note thatthe modified curve is given as Model 2 above.

Since the starting load is 50%, the actual load will be 50% of the load based on the modified curve (Model





2) as described above. The starting load torque is equal to 0.5 Tr.

Case 2: Load Model Based on Motor Mechanical Load

In this case, the load torque curve will not be shifted because it is assumed to represent the actual load.However, since the starting load is 50%, the load torque curve will be adjusted so that the torque at each

point of the curve is multiplied by 0.5. The starting load torque is equal to 0.5*0.8 Tr = 0.4 Tr.

Note: If the motor has a load model as given in Model 2 above, there is no difference in calculation resultsbetween the two options.

Adjustment Page - Motor Starting Study Case Editor

This page allows the User to specify tolerance adjustments to transformer, reactor, and overload heaterimpedance, cable and transmission line length, and cable and transmission line temperature effect on theirresistance values. Each tolerance adjustment can be applied based on the individual equipment percenttolerance setting or based on a globally specified percent value.



- Event Page - Add Action by Starting Category

- Add Action by Load - Model Page - Adjustment Page

- Alert Page Display Options Motor Starting Plots

- Plot Display Motor Starting Calculation Methods - Motor Starting Required Data Motor Starting Output Reports One-Line Diagram Display

Alert View





Impedance ToleranceIn this group, you can specify impedance tolerance values for transformer, reactor, and overload heater.

TransformerThis adjustment is applied to transformer impedance. The net effect of the transformer impedance

adjustment in motor starting calculations is to increase the impedance by the specified percent tolerancevalue. For example, if the transformer impedance is 12% and the tolerance is 10%, the adjusted impedanceused in the motor starting calculation will be 13.2%, resulting in higher losses.

The Impedance Adjustment can be applied to individual transformers by using the tolerance percent valuespecified in the Transformer editor Rating page. Alternatively, a global Transformer Impedance

Adjustment can be applied as well by selecting and specifying a global tolerance other than 0% in thecorresponding field.

ReactorThis adjustment is applied to the reactor impedance. The Motor Starting module increases the reactor

impedance by the specified percent tolerance resulting in a larger impedance value and consequently alarger voltage drop. For example, if the impedance of the reactor is 0.1 Ohm and its tolerance is 5%, thenthe adjusted reactor impedance used in the Load Flow calculation is 0.105 Ohm.

The Impedance Adjustment can be applied to individual reactors by using the tolerance percent valuespecified in the Reactor editor Rating page. Alternatively, a global Reactor Impedance Adjustment can beapplied as well by selecting and specifying a global tolerance other than 0% in the corresponding.

Overload HeaterThis adjustment is applied to the overload heater (OH) resistance. The Motor Starting module increases theOH resistance by the specified percent tolerance resulting in a larger resistance and consequently a larger





voltage drop. For example, if the resistance of the OH is 0.1 Ohm and its tolerance is 5%, then the adjustedOH resistance used in the motor starting calculation is 0.105 Ohm.

The Resistance Adjustment can be applied to individual overload heaters by using the tolerance percentvalue specified in the Overload Heaters editor Rating page. Alternatively, a global Overload HeaterResistance Adjustment can be applied as well by selecting and specifying a global tolerance other than 0%

in the corresponding field.

Length ToleranceYou can specify length tolerance values for cables and transmission lines in this group. If Ohms is selectedas the unit for a cable in the Impedance page of Cable editor, the length tolerance will not be applied to thecable. Likewise,if Ohms is selected as the unit for a transmission line in the Impedance page ofTransmission editor, the length tolerance will not be applied to the transmission line.

CableThis adjustment is applied to the cable length. The Motor Starting module increases the cable length by thespecified percent tolerance resulting in larger impedance and consequently a larger voltage drop. For

example, if the length of the cable is 200 ft. and the tolerance is 5%, then the adjusted cable length used inthe motor starting calculation is 210 ft.

The Length Adjustment can be applied to individual cables by using the tolerance percent value specifiedin the Cable editor Info page. Alternatively, a global Cable Length Adjustment can be applied as well byselecting and specifying a global tolerance other than 0% in the corresponding.

Transmission LineThis adjustment is applied to the transmission line length. The Motor Starting module increases thetransmission line length by the specified percent tolerance resulting in larger impedance and consequentlya larger voltage drop. For example, if the length of the transmission line is 2 miles and the tolerance is

2.5%, then the adjusted transmission line length used in the motor starting calculation is 2.05 miles.

The Length Adjustment can be applied to individual lines by using the tolerance percent value specified in

the Transmission Line editor Info page. Alternatively, a global Transmission Line Length Adjustment canbe applied as well by selecting and specifying a global tolerance other than 0% in the corresponding field.

Resistance Temperature CorrectionThis group allows the User to consider resistance correction based on the maximum operating temperaturefor cable and transmission line conductors. Each temperature resistance correction can be applied based on

the individual cable/line maximum temperature setting or based on a globally specified value.

CableThis adjustment is applied to the cable conductor resistance. The Motor Starting module adjusts theconductor resistance based on the maximum operating temperature. If the maximum operating temperatureis greater than the rated base temperature of the conductor, then its resistance is increased.

The temperature correction can be applied to individual cables by using the maximum operating

temperature value specified in the Cable editor Impedance page. A global temperature correction can bespecified as well by selecting and specifying a global maximum temperature value in the correspondingfield. For more information, see the Cable Editor Impedance Page Section in Chapter 11, AC-Editors.

Transmission LineThis adjustment is applied to the transmission line conductor resistance. The Motor Starting module adjusts

the conductor resistance based on the maximum operating temperature. If the maximum operatingtemperature is greater than the rated base temperature of the conductor, then the resistance is increased.

The temperature correction can be applied to individual lines by using the maximum operating temperature

value specified in the Transmission Line editor Impedance page. A global temperature correction can be

specified as well by selecting and specifying a global maximum temperature value in the corresponding.For more information, see the Transmission Line Editor Impedance Page Section in Chapter 11, AC-





Editors.

Alert Page - Motor Starting Study Case Editor

You can specify the limits for ETAP to raise critical and marginal alerts for a Motor Starting simulationfrom the Alert page. The alerts consist of three categories: alerts on starting motor and MOV, alerts ongenerator operating conditions, and alerts on bus voltage. Each category also consists of several types.Select an alert type to have ETAP perform an alert check for that type. If an alert type is not selected,ETAP will skip the alert check for that alert type.

Motor Starting Analysis Toolbars - Time Slider Toolbar

Study Case Editor

- Info Page - Event Page - Add Action by Starting Category - Add Action by Load

- Model Page - Adjustment Page - Alert Page

Display Options Motor Starting Plots - Plot Display

Motor Starting Calculation Methods - Motor Starting Required Data






Critical and MarginalThere are two levels of alerts for a Motor Starting study: critical alert and marginal alert. The alert limitvalues are set in the Critical and Marginal columns. The difference between Marginal and Critical Alerts is

their use of different percent value conditions to determine if an alert should be generated. If a conditionfor a Critical alert is met, an alert will be generated in the Critical Alert group of the Alert View window.The same is true for Marginal Alerts. Also, the Marginal Alerts option must be selected to display the

Marginal Alerts. If a device alert qualifies it for both Critical and Marginal alerts, only Critical Alerts aredisplayed.

Note: For ETAP to generate alerts for an element type, both the element rating and the percent valueentered in this page must be non-zero. The element ratings for alert checking are given in the following

Sections.

Starting Motor/MOVETAP checks alert for motor terminal voltage and fail to start for starting motors and MOVs.

MOV Terminal VoltageETAP checks the terminal voltage of a starting MOV against the limit you set in the study case. The alertlimit is a percentage based on MOV rated voltage.

Motor Terminal VoltageETAP checks the terminal voltage of a starting motor against the limit you set in the study case. The alertlimit is a percentage based on motor rated voltage.

Motor Slip (Fail To Start) >=Motor slip alert is for identifying fail to start condition for a starting motor. It is applicable only for





Dynamical Motor Acceleration calculations. The alert limit is motor slip in percent. If after a motor isswitched on, its slip is always higher than this limit until the end of simulation, an alert will be generatedby ETAP.

GeneratorIn this group, you can specify alert limits for operating values of a generator, generator engine and

generator exciter.

You can specify a minimum time of violation for generating an alert for each type of alert in this group.

When a non-zero value is entered in this field, ETAP will generate an alert only when a continuousviolation lasts longer than the minimum time of violation.

Generator RatingA generator rating alert is generated when the output power (MVA) from a generator is larger than the alertlimit. The alert limit is in percent based on generator rated MVA.

PrimeMover Continuous RatingAs the Prime Mover rating of a generator may not be the same as the generator itself, a separate alert forPrime Mover rating is needed. A Prime Mover continuous rating alert is generated when the output real

power (MW) from a generator is larger than the alert limit. The alert limit is in percent, based on generatorPrime Mover continuous rating, entered in the Prime Mover Rating group of the Rating page in theSynchronous Generator editor.

PrimeMover Peak RatingA Prime Mover peak rating alert is generated when the output real power (MW) from a generator is largerthan the alert limit. The alert limit is in percent, based on generator Prime Mover peak rating, entered in the

PrimeMover Rating group of the Rating page in the Synchronous Generator editor.

Mvar Peak RatingETAP provides an alert on the maximum var peak rating for generators. A var peak rating alert is generatedwhen the output reactive power from a generator is larger than the alert limit. The alert limit is in percent,

based on generator peak var, entered in the Mvar Limits group of the Rating page in the SynchronousGenerator editor.

Bus VoltageDue to large and heavily reactive currents drawn from starting motors, system under-voltage is always ofgreat concern in maintaining normal operations during motor starting. To quickly identify any potential

under-voltage problems, ETAP provides different levels of alerts for starting motor terminal buses,generator and power grid terminal buses, and other buses with different voltage levels.

You can specify a minimum time of violation for generating an alert for each type of alert in this group.When a non-zero value is entered in this field, ETAP will generate an alert only when a continuousviolation lasts longer than the minimum time of violation.

Starting Motor Term. VoltageAn under-voltage alert for starting motor terminal voltage is generated when the motor terminal voltage isless than the alert limit. The alert limit is in percent based on motor rated voltage. This alert helps identifypossible fail to start conditions, especially for Static Motor Starting studies which do not simulate the

motor acceleration process. The alert limit can be set based on the manufacturer provided minimumvoltage requirement for a motor to start.

Generator/Grid Term. VoltageAs a power source delivers heavy starting current, its terminal voltage can also suffer serious drop. It is ofgreat importance to monitor and maintain acceptable voltage level for a generator or power grid during

motor starting because it can affect a far larger area of loads than voltage drop on a starting motor terminalbus. An under-voltage alert for generator or power grid terminal voltage is generated when the sourceterminal voltage is less than the alert limit. The alert limit is in percent based on the generator or powergrid rated voltage.





HV Bus, kV >=An under-voltage alert for a high voltage bus is generated when the bus voltage is less than the alert limit.The alert limit is in percent based on the bus nominal voltage. A bus is considered as a high voltage bus ifits nominal kV is larger than or equal to the value entered in the field on the same line.

MV Bus, kV Between

An under-voltage alert for a medium voltage bus is generated when the bus voltage is less than the alertlimit. The alert limit is in percent based on the bus nominal voltage. A bus is considered as a medium

voltage bus if its nominal kV is between the voltage limits set for high and low voltage buses.

LV Bus, kV <=An under-voltage alert for a low voltage bus is generated when the bus voltage is less than the alert limit.The alert limit is in percent based on the bus nominal voltage. A bus is considered as a low voltage bus if

its nominal kV is less than or equal to the value entered in the field on the same line.

Auto DisplayAfter the motor starting calculation is completed, ETAP checks for any abnormal operating conditions

according to alert limits you set in the Alert page of Motor Starting Study Case. If any abnormal conditionshave been determined, alerts will be generated and reported in Alert View as well as in the Crystal Reportsformat report. If you select the Auto Display option and alerts are generated by the calculation, the AlertView will open automatically. For information about the Alert View window, see Section 21.8, AlertView.

MarginalSelect the Marginal option if you want the Alert View to display marginal alerts.

Motor Starting Display OptionsThe Motor Starting Analysis Display Options consist of a Results page and three pages for AC, AC-DC ,and color information annotations.

Note: The colors and displayed annotations selected for each study are specific to that study.

Results PageSelect the result information to be displayed on the one-line diagram.


Toolbars

- Time Slider Toolbar Study Case Editor - Info Page - Event Page

- Add Action by Starting Category - Add Action by Load

- Model Page


Motor Starting Plots - Plot Display Motor Starting Calculation Methods - Motor Starting Required Data Motor Starting Output Reports

One-Line Diagram Display Alert View





Voltage MagnitudeFrom the drop-down list, select a unit for bus voltage display. It can be in percent or kV.

Bus MagnitudeSelect this option to display bus voltage magnitude in the selected unit. When the option is cleared, a busvoltage will not be displayed on one-line diagram.

Load Term. MagnitudeSelect this option to display load terminal voltage magnitude in the selected unit. When the option is

cleared, a load terminal voltage will not be displayed on one-line diagram.

Load Term. Base kVThis group allows you to select base kV for load terminal voltage when voltage magnitude is to be

displayed as a percentage. If the voltage is to be displayed in kV, this group is disabled.

Load Rated kVSelect this option to use load rated kV as the base voltage.

Bus Nom. kVSelect this option to use load terminal bus nominal kV as the base voltage.

Power Flows

Select a unit of measure for power flow from the drop-down list to be displayed on the one-line diagram.This can be in kVA or MVA. The display unit options listed below change depending on this selection.

kW + kvar or MW + Mvar





Select the kW + j kvar option ( for kVA units) to display power flow in kW and kvar or MW + jMvar (forMVA units).

KVA or MVA Click the kVA button to display power flow in kVA or the MVA button to display power flow in MVA.

Amp

Click the Amp button to display current flow in amperes.

%PFSelect the %PF option to display power factor in percent.

Show UnitsSelect this option to show units for voltage and power flow annotations.

AC Display Option PagesAC Page

AC-DC Page

Motor Starting Plots

ETAP also provides simulation plots for you to examine calculation results graphically. To view thesimulation plots, click the Motor Acceleration Plots button in the Motor Starting toolbar. It will bring up aMotor Starting Plot Selection dialog box, where you can specify devices and types of plots to view.

Motor Starting Analysis Toolbars - Time Slider Toolbar Study Case Editor - Info Page


- Model Page

- Adjustment Page - Alert Page Display Options Motor Starting Plots

- Plot Display Motor Starting Calculation Methods - Motor Starting Required Data






Device TypeThere are five types of devices for which you can plot: generators and power grids, starting motors, startingMOVs, static loads and capacitors, and buses.

Device IDThis list contains IDs of all devices for the selected device type. Click a device ID to view its plots.

Clicking again will deselect it. Plots for up to 16 devices can be displayed on one plot view. If more than16 devices have been selected, plots for the first 16 devices will be displayed.

Plot Type

The Plot Type group provides a selection of plots for the selected device type. The following table listsavailable plots for the five device types. Plots for slip and starting motor torques are generated only by

dynamic motor starting calculations. The motor torque is in percent, based on motor rated torque.

Available Plot Types for Motor Starting Studies

Generator Power Grid Starting Motor Starting MOVStatic Load

CapacitorBus

Current Slip Current Current Voltage

Vt (Machine Base) CurrentVt (MOVBase)

Vt (LoadBase)

MW Vt (MotorBase)

Vt (Bus Base) Vt (Bus Base)

Mvar Vt (Bus Base) Vbus Vbus





The Check All button allows you to check all available plot types for the selected plot type. Clicking the

Uncheck All button will clear all available plot types for the selected plot type.

Combine PlotsSelect this option to plot curves for the selected plot types on one graph. This feature allows you tocompare different types of plots (for example, voltage, slip, and starting motor torque) on the same graph.

Close All Plots

Clicking the Close All Plots button will close all existing open plots.

When you click the OK button, ETAP will open plot views for all the selected plot types. ETAP opens one

plot view for each selected plot type to display the type of plots for the selected motors.

For information about viewing plots, see Section 7.7, Plots.

MVA Vbus kW kW

PF Accel. Torque kVar kVar

Motor Torque kVA

Load To rque

kW, Electrical

kvar

kW,Mechanical





Modifying Plot ParametersPlot parameters such as plot line type, axis, legend, and text can be modified directly from the plot view.For example, to modify plot line type, double-click the plot line and change the line type from the PlotParameters editor. For more information about modifying plot parameters, see Section 7.7.1, Modify PlotParameters.

Plot Display


Toolbars - Time Slider Toolbar Study Case Editor - Info Page


- Model Page

- Adjustment Page - Alert Page

Display Options Motor Starting Plots - Plot Display Motor Starting Calculation Methods - Motor Starting Required Data Motor Starting Output Reports






Motor Starting Calculation MethodsETAP provides two methods for motor starting: Dynamic Motor Acceleration and Static Motor Starting.

Both methods perform time-domain simulations and report results in both text report and plot formats.

The purpose of performing a motor starting study is twofold: to investigate whether the starting motor can

be successfully started under the operating conditions and to see if starting the motor will seriously impede

Motor Starting Analysis Toolbars - Time Slider Toolbar

Study Case Editor - Info Page - Event Page


- Model Page - Adjustment Page - Alert Page

Display Options Motor Starting Plots - Plot Display

Motor Starting Calculation Methods - Motor Starting Required Data Motor Starting Output Reports One-Line Diagram Display

Alert View





the normal operation of other loads in the system.

The Dynamic Motor Acceleration and Static Motor Starting differ in the way the starting motors are

modeled.

Dynamic Motor AccelerationIn Dynamic Motor Acceleration, a dynamic model throughout the whole simulation models theaccelerating motor. For this study, you also need to specify a load torque model for the load that the motor

is driving.

From the Model page for induction motor, or the LR Model page for synchronous motor, you can specifymotor dynamic model from one of the five different types:

Single1 - Equivalent (Thevenin) circuit model with constant rotor resistance and reactance

Single2 - Circuit model with deep-bar effect, rotor resistance and reactance change with speed

DBL1 - Double cage circuit model, with integrated rotor cages

DBL2 - Double cage circuit model, with independent rotor cages

TSC - Torque slip characteristic curve model

While the Single1, Single2, DBL1, and DBL2 models are all based on an electrical circuit representation ofthe motor, the TSC model allows you to model a starting motor directly from the manufacturer’sperformance curves. You can choose one of the existing library models or create your own motor model in

the Motor Library.

ETAP also allows you to model the load torque curve for each individual motor. You can choose one of the

existing library models or create your own motor model in the Motor Load Library.

Due to the difference in modeling of starting motors, you may perform the static motor starting study if youare more concerned with the effect of motor starting on other operating loads in the system or ifinformation on dynamic model for the starting motor is not available. On the other hand, if you are





concerned with the actual acceleration time or whether the starting motor can be successfully started, adynamic motor acceleration study should be performed.

Static Motor StartingIn the Static Motor Starting method, it is assumed that the starting motor can always be started. Youspecify from the Motor Editor motor acceleration time at 0% and 100% of the load, and the module

interpolates the acceleration time for the motor load based on these two values.

During the acceleration period, the motor is represented by its locked-rotor impedance, which draws the

maximum possible current from the system and has the most severe effect on other loads in the system.Once the acceleration period has passed, the starting motor is changed to a constant kVA load and ETAPsimulates the load ramping process according to the starting and final loads specified in the motor editor.Refer to Motor Starting Category page in Motor editor for more information.

Load TransitionIn an event, you can specify a load transition to transfer system operating load from one loading ca tegoryto another. This allows you to globally adjust the system load during motor starting studies. You may applya load transition to all operating loads or to a group of loads by setting an upper limit of capacity on loads

to be involved in the load transition. Additionally, you can start motors through load transition if the loadpercent is changed from zero to a non-zero value.

Due to the complexity involved in the interaction between normal motor starting actions and loadtransition, the following rules are implemented to resolve conflicts in motor starting action preparation.

1. If, in an event, both action by load or starting category and action by load transition call for changeof status or loading of a load, the action by load or starting category takes priority.

2. If a load, whether a motor, an MOV, a static load, or a capacitor, is switched on/off through actionsby load or starting category in one event, the load transition will not apply to this load from thatpoint on.

3. If, in a load transition, the load percent of a motor (or an MOV) is changed from zero percent to anon-zero value, this motor (or MOV) will be started at the new load percent (non-zero value). Andfrom this point on, the load transition will not apply on this motor (or MOV) any more.

4. Load transition does not apply on MOVs that have initial status as either Open or Closed .5. In calculating load for a load transition, it takes into considera tion the options for load diversity

factors entered in the Motor Study Case editor for prestart load flow.

MOV Motor StartingMOVs are specially designed motors that have different operational characteristics from regular motors.Since these motors behave close to constant impedance load during operation, they are modeled as constant

impedance load in motor starting calculations.

The operation mode of an MOV may be opening or closing a valve, depending upon its initial status. Tostart an MOV motor, its status has to be either open or closed. If the initial status of an MOV is open, itsoperation mode will be closed and if the initial status is closed, its operation mode will be open. Both

modes involve several stages of operation as defined in the Characteristic group of the Nameplate page inMOV editor. For each stage, the impedance to represent the MOV is calculated based on the current andpower factor for the stage and the rated voltage.

For one motor starting simulations, a MOV is allowed to start only once due to infrequent operations ofMOV.

Starting DeviceA starting motor can have one of thirteen types of starting devices modeled in the Motor Starting studies,

including four general models for soft starter. You can specify starting device type and its controlcharacteristics from the Start Dev page of Induction Motor editor or Synchronous Motor editor. Dependingon the model type selected to represent a starting motor, certain types of starting device may not apply. The





following table gives applicable starting devices for each type of motor models.

Starting Device Modeled in Motor Starting Studies

Generation Category ChangeIn power system operations, it happens sometimes that while a larger motor is in the process of starting up,a major source such as a power grid suddenly changes its operating values for the magnitude of voltage atthe interface point between the power grid and your electrical system. To simulate this situation, ETAP

allows you to change generation category for generators and power grids. In any event, you can changegeneration category from the existing one to any category. The operating values for the ten generation

categories are entered from the Rating page of Synchronous Generator editor or Power Grid editor.

If a system contains multiple power sources (generators and power grids), change of generation for anypower source will potentially alter operating conditions of other power sources. In motor startingcalculation , whenever there is a change of generation category for a generator or a power grid, ETAP usesthe prestart system loading to determine internal voltage magnitude and angle of all generators and power

grids. These internal voltage magnitude and angle values stay constant until there is a new change ofgeneration category.

Motor Starting vs. Transient Stability StudiesThe motor starting calculation is intentionally directed to investigate the behavior of a starting motor andits effect on system operations, as facilitated by starting devices, etc. The transient stability calculation can

also simulate the motor starting process, with emphasis on the dynamic behavior of the whole system underthe impact of motor starting. The differences in objectives of the two types of calculation lead to differentmodeling of system elements, as shown in the table below.

Comparison of System Element Models

Motor Model

Starting Device ModelStatic Motor

Starting Dynamic Motor Starting

LRZ Single 1 Single 2 Double 1 Double 1 TSCAuto-XFMR Yes Yes Yes Yes Yes Yes

Stator R Yes Yes Yes Yes Yes Yes

Stator X Yes Yes Yes Yes Yes Yes

Capacitor @ Bus Yes Yes Yes Yes Yes Yes

Capacitor @ Term Yes Yes Yes Yes Yes Yes

Rotor R Yes No Yes No No No

Rotor X Yes No Yes No No No

Y/D Yes Yes Yes Yes Yes Yes

Partial Winding Yes Yes Yes Yes Yes No

Current Limit Yes Yes Yes Yes Yes Yes

Current Control Yes Yes Yes Yes Yes Yes

Voltage Control Yes Yes Yes Yes Yes Yes

Torque Control No Yes Yes Yes Yes Yes

Element Load Flow Transient StabilityDynamicMotor Acceleration

StaticMotor Starting

Generators Infinite BusDynamicallyModeled

Constant VoltageBehind Xd’

Constant VoltBehind Xd’

Exciter/GovernorsNot Applicable

DynamicallyModeled

Not Modeled Not Modeled

Utility Ties Infinite BusConstant VoltageBehind X ”

Constant VoltageBehind X ”

Constant Volt

Behind X”





Other Features of Motor Starting StudyMany features are included in the motor starting study to facilitate system design and analysis, includingthe following:

A static load can be switched on and off repeatedly at any time during a simulation with user

specified loading category.

A motor can be started and switched off repeatedly at any time during a simulation.

The motor switching can be specified by an individual load or by bus and starting category.

In static motor starting, after the acceleration period is passed, it will be modeled as a constantpower load. The load level can vary at a rate specified by the user. Please see Motor StartingCategory page for a detailed description on the model for load changes.

An MOV can be started at any time during the simulation.

Modeling of SVCIn the initial load flow calculation, an SVC is modeled the same way as in a standard Load Flowcalculation. It will adjust terminal bus voltage as specified in the SVC editor and provide or absorb reactive

power as needed. However, after the initial load flow, it will be represented as a constant impedance loadwith the value set based on the initial load flow.

Induction Motor with %Loading Equal to ZeroSince the induction motor editor has been enhanced to allow to specify the motor input current at zeroloading, in load flow calculations, a motor with %loading equal to zero may still draw power from the

system due the losses in the motor. This means that in load flow calculation a motor with zero loadingindicates that the motor has no output power, but the motor is still running.

In motor acceleration calculations, the meaning of loading being zero is different from load flowcalculation. If a motor has zero loading, it means that the motor is not connected and it draws zero currentand power from the system, even if the no-load current entered in the motor editor is larger than zero. Thisapplies to operating induction motors in both initial load flow and load transition.

Note that if an operating motor has loading equal to 0.01%, its input power will be calculated based on theparameters from the Nameplate page of the Induction Motor Editor. So there may be a jump in input powerfor operating motors in motor acceleration when the load is changed from 0.01% to 0%.

Modeling of Induction GeneratorThere is an option in the Info page of the Induction Machine editor to set the Application Type as Motor or

Generator. If an induction machine is set as Induction Generator, its modeling can be different depending

on whether the machine is started in a Motor Stating simulation. For all operating induction generators, theones that are not started in a simulation, they are modeled the same way as in Load Flow calculation. Theinduction generator provides real power to the system and draws reactive power from the system. This rule

Operating Motors Constant kVA

ModeledDynamically or

Constant kVAConstant kVA Constant kVA

Starting Motors Not Applicable

Single1, Single2,

DBL1, & DBL2Models

Single1, Single2,

DBL1, DBL2, &TSC Models

Locked-Rotor ZPower Factor

Starters Not Applicable Modeled Modeled Modeled





applies to initial load flow as well as load transitions.

For induction generators that are started during a simulation, either through action by element, action by

starting category, or action by load transition, it is modeled differently before and after the inductiongenerator is started. In the initial load flow and during load transitions before the machine is started, it ismodeled as in induction generator in the same way as in the Load Flow calculations. Once the machine is

started, it will be modeled as an induction motor from that point on in the simulation. When modeled as an

induction motor, its rated kVA will be the same value as displayed in the editor, but its output horsepower(or kW) will be recalculated based on the machine rated kVA, efficiency and power factor.

Modeling of VFD

VFD ConnectionsETAP allows for very flexible connections for a VFD. Its input can connect to a bus, a branch, or multipletransformers. Its output can be connected to a bus or a load (motor or a lump load). The following figure

shows some typical connections of VFD in ETAP. From the view point of calculation handling, there aretwo types of VFD connections: VFD sub-network and load directly connected VFD. A load directlyconnected VFD is shown as VFD-1 below where a load (a motor or a lump load) is connected to a busthrough a VFD. A VFD sub-network is a sub-system connected to the output of a VFD, consisting of

buses, loads and branches, as shown in VFD-2, VFD-3 and VFD-4 below. In the current version of ETAP,it is required that a VFD sub-network be a radial system, contain only one energized motor, and not include

3-winding transformers or source elements.

In Motor Acceleration Analysis, the sub-network powered by a VFD, i.e. the sub-system below VFD-4, isaggregated along with motor equipment cable as one equivalent impedance. ETAP does not report thevoltages and flows on the buses and branches in the VFD sub-network. All adjustment options specified inthe study case are still applicable to these elements. The fixes or manual operating taps of transformers in aVFD sub-network are considered in the calculation, but transformer LTC is excluded.

Typical VFD Connections

Modeling of VFD for Operating LoadsFor an operating load (a motor or a lump load) powered by a VFD, either in the initial load flow or duringload transition, the VFD is modeled the same way as the regular load flow calculations. The VFD is





represented as a constant voltage source with the output voltage and frequency determined by the V/Hz andoperating frequency of the applicable generation category. On the input side, the VFD is modeled as aconstant power load with the input power equal to the output real power divided by its efficiency. The

input reactive power is dependent on the operating input PF option selected from the Loading page of theVFD editor. When there are multiple input transformer connections, the input power is equally sharedamong all connections.

Note that for a load that is directly connected to a VFD,( i.e. VFD-1 shown above) the equipment cableloss is calculated based on the VFD operating voltage. For a VFD sub-network, i.e. VFD-4 shown above,the losses associated with the sub0network is calculated based on the aggregated equivalent impedance.

Modeling of VFD for Starting MotorsFor a starting motor powered by a VFD, the VFD output voltage and frequency follow the control scheme

specified in the Start Device page if the Frequency Control type is selected. If the option “None” isselected, the modeling of VFD will be different depending on if the motor is directly connected to the VFDor there is a bus in between (case for VFD sub-network). Additionally, the starting motor may have its ownstarting device entered in the motor editor and this motor starting device may take effect in some cases.

The specific rules for handling all these cases are listed the section below.

Basic Rules for Starting Motors with VFD

a. If a starting motor is directly connected to a VFD (i.e. Mtr1 below) and the VFD Starting Devicetype is set as None, the VFD is ignored in motor acceleration. This is similar to the bypass switchbeing closed. The motor starting device takes effect if it is specified.

b. If a starting motor is directly connected to a VFD (i.e. Mtr5 below), but the VFD Starting Devicetype is set as Frequency Control, the VFD will be modeled according to the specified Control

Scheme. The starting device of the motor is ignored.c. If the VFD output is connected to a bus (i.e. VFD3 below), the VFD will be modeled according to

the specified Control Scheme. The starting device of the motor is ignored.d. If the bypass switch of a VFD is closed, the VFD is simulated as a closed switch. The motor starting

device takes effect if it is specified.

VFD and Motor Modeling for Starting Motors





If a VFD has the Frequency Control type selected for motor acceleration and the starting motor has thecharacteristic model selected, ETAP does not support Dynamic Motor Starting simulation for the motor,since the characteristic model is only for rated frequency and it does not represent motor behavior underdifferent frequency. For the same reason, if a starting motor is powered by a VFD, it is not supported to

start this motor in the Static Motor Starting simulations, except that the motor is directly connected to theVFD. This exception is primarily for compatibility to the older versions of ETAP.

Motor Plots for VFD Controlled Starting MotorsDue to the variable frequency applied on a starting motor, several new types of plots are added to starting

motors. The following table gives definitions for different plots. Note that the rated frequency for a motoris the ETAP project frequency. If a VFD is connected to the starting motor through a sub-network, the sub-network is modeled as an equivalent impedance for the motor. The table shows that when a starting motoris controlled by a VFD, plots for the motor line current and input power are actually the values at VFDinput.

Plots for Starting Motors

Plot Type Definition

SlipMotor slip with respect to applied frequency. For a VFD controlled startingmotor, this plot does not indicate motor speed if the applied frequency is not therated value.

Speed Motor speed in percent of the synchronous speed for motor rated frequency.

Current (Line) VFD input current in percent of motor FLA.

Current (Terminal) Motor terminal current in percent of motor FLA.

Vt (Motor Base) Motor terminal voltage in percent of motor rated kV.

Vt (Bus Base) Motor terminal voltage in percent of VFD input terminal bus nominal kV.

V bus VFD input terminal bus voltage in percent of bus nominal kV.

Accel. Torque Motor acceleration torque in percent of motor rated torque.

Motor Torque Motor acceleration torque in percent of motor rated torque.

Load Torque Load torque in percent of motor rated torque.

kW (Electrical) VFD input real power in kW.

Kvar VFD input reactive power in kvar.

kW (Mechanical) Motor output power in kW.

Frequency VFD output frequency applied on motor

Voltage/Hz Motor terminal Volt/Hz in percent on motor rated voltage and freuqnecy.





Motor Starting Required Data

Bus DataRequired data for motor starting calculations for buses includes:

Bus ID

Nominal kV

%V and Angle (when Initial Condition is set to use Bus Voltages)

Load Diversity Factor (if the Loading option is set to use the Maximum or Minimum load)

Branch DataBranch data is entered into the branch editors, including the 3-Winding Transformer Editor, 2-WindingTransformer Editor, Transmission Line Editor, Cable Editor, Reactor Editor, and Impedance Editor.Required data for motor starting calculations for branches includes the following:

Branch ID

Branch Z, R, X, or X/R values and units, tolerance, and temperatures, if applicable

Cable and transmission line length and unit

Transformer rated kV and kVA/MVA, tap and LTC se ttings

Impedance base kV and base kVA/MVA

Power Grid Data

Required data for motor starting calculations for power grids includes:

Utility ID



- Event Page


- Model Page - Adjustment Page

- Alert Page Display Options Motor Starting Plots

- Plot Display Motor Starting Calculation Methods - Motor Starting Required Data

Motor Starting Output Reports One-Line Diagram Display

Alert View





Mode (Swing, Voltage Control or Mvar Control)

Rated kV, and short-circuit MVA and impedance

Generation category data (%V and Vangle)

Synchronous Generator DataRequired data for motor starting calculations for synchronous generators includes:

Synchronous Generator ID

Mode (Swing, Voltage Control or Mvar Control)

Rated kW, kV, and power factor

Xd’ and X/R ratio

Generation category data, ( V%, MW and Mvar)

Synchronous Motor DataRequired data for motor starting calculations for synchronous motors includes:

Synchronous Motor ID

Rated kW/hp and kV

Power factors and efficiencies at 100%, 75%, and 50% loading for operating motors

Loading Category IDs and % Loading for operating motors

Equipment cable data

Induction Motor DataRequired data for motor starting calculations for induction motors includes:

Induction Motor ID

Rated kW/hp and kV

Power factors and efficiencies at 100%, 75%, and 50% loading

Loading Category ID and % Loading


Static Load DataRequired data for motor starting calculation for static loads includes:

Static Load ID





Rated kVA/MVA and kV

Power factors at 100%, 75%, and 50% loading

Loading Category ID and % Loading


MOV DataRequired data for motor starting calculation for MOV includes:

MOV ID Rated kW/hp and kV

Current, PF, and time for each operation stage


Capacitor DataRequired data for motor starting calculation for capacitor includes:

Capacitor ID

Rated kV, kvar/bank and number of banks

Loading category ID and % Loading


Lumped Load DataRequired data for motor starting calculation for lumped load includes:

Load ID

Rated kV, MVA, power factor, and % for motor load

Loading category ID and % Loading

Variable Frequency Drive (VFD) DataRequired data for motor starting calculation for VFD includes:

VFD ID

Rated input/output kV, kVA, frequency, efficiency, and input power factor

Operating input power factor, frequency, and V/Hz ratio Starting control type, control parameters, and current limit

Additional Data for Starting MotorsFor Static Motor Starting studies, the additional data includes:

Motor locked-rotor impedance and power factor

Motor acceleration time at no load and full load

Start and final percent loading and begin and end of load change time

Starting device data when needed





No load and full load accelerated time (for static motor starting)

For Dynamic Motor Acceleration studies, the additional data includes:

Dynamic motor model for induction motors

LR model for synchronous motors

Load torque model

Motor inertia

Study Case DataThere are some study case related data, which must also be provided. This data includes:

Study Case ID

Maximum number of iteration

Precision of solution

Total simulation time, simulation time step, and plot time step

Prestart loading (loading category)

Initial condition

Transformer LTC data

Equipment adjustment options

Alert options

Report (report format)

The study case related data is entered into the Motor Starting Study Case editor.


Toolbars - Time Slider Toolbar Study Case Editor - Info Page - Event Page - Add Action by Starting Category

- Add Action by Load - Model Page

- Adjustment Page - Alert Page Display Options Motor Starting Plots

- Plot Display Motor Starting Calculation Methods

- Motor Starting Required Data Motor Starting Output Reports





Motor Starting Output ReportsThe motor starting calculation results are reported in four different formats: Crystal Reports, a one-lineview display, and plots. You can use the Display Options editor to specify the content to be displayed.

The Crystal Reports format provides you with detailed information for a motor acceleration analysis. Youcan utilize the Report Manager to help you view the output report.

The output report consists of several sections, as summarized in the following Section.

Output Report Sections

System Input DataThe beginning of the output report prints the system input data that is used in the motor starting study,including bus input data with the operating load connected to each bus, system branch data, branchconnection summary, and generator and utility machine data.

Initial Load Flow ReportAn initial load flow study is performed with the specified prestarting load. This load flow calculation iscarried out using the Newton-Raphson method. The load flow result is printed for you to inspect systemoperating conditions.

Switching Motor and Static Load DataThe switching motor and static load data printed include the motor nameplate data, equivalent cable data,

and the switching static load data.For dynamic acceleration studies, the motor dynamic model and load model data are also printed in thissection.

Switching Event DataThis section of the output report lists, in the sequence of time events, every load-switching action,generation category change, and bus loading change from load transitions. It provides you with a summaryof all the actions that are to be simulated in the study.

Event Load Flow ReportFor each specified time event, whether there are switching actions or not, the module will run a load flowcalculation and report the result in this section. This feature provides you with a way to inspect systemoperating conditions at any time during motor starting simulation. The module also runs a load flow at theend of the total simulation time and prints the results in this section.

Tabulated Simulation ResultsThis section tabulates, the simulation results, for each switching motor, as functions of time at the specified

plot time step. The tabulated results include motor slip, motor terminal voltage, bus voltage, motor current,and motor real power input.

View Output Reports From Study Case ToolbarThis is a shortcut for the Report Manger. When you click the View Output Report button, ETAP

automatically opens the output report, which is listed in the Study Case toolbar with the selected format. Inthe picture shown below, the output report name is MS-Stat and the selected format is Complete.






Motor Starting Report ManagerTo open the Report Manager, click the View Report Manager button on the Motor Acceleration toolbar.The editor includes four pages (Complete, Input, Result, and Summary) representing different sections of

the output report. The Report Manager allows you to select formats available for different portions of thereport and view it via Crystal Reports. There are several fields and buttons common to every page, as

described below.

Output Report NameThis field displays the name of the output report you want to view.

PathThis field displays the path of the project file based on which report was generated, along with thedirectory where the project file is located.

HelpClick this button to access Help.

OK/CancelClick the OK button to dismiss the editor and bring up the Crystal Reports view to show the selected

portion of the output report. If no selection is made, it will dismiss the editor. Click the Cancel button todismiss the editor without viewing the report.

Input Data PageThis page allows you to select different formats for viewing input data, grouped according to type. Theyinclude:

Acceleration Report Events

Adjustments Impedance





Result PageThis page allows you to select formats to view the result portion of the output report.

Alert Complete Inverter

Alert Critical Load Flow R

Alert Marginal Load Torque

Branch Machines

Bus Reactor

Cable SVC

Complete Switching LoCover Torque Slip

Equipment Cable Transformer





Summary PageThis page allows you to select formats to view summary reports of the output report, including variousalerts, sequence of events, and switching motors and static loads.

Complete PageIn this page there is only one format available, Complete, which brings up the complete report for a motor

acceleration study. The complete report includes input data, results, and summary reports.






Toolbars - Time Slider Toolbar

Study Case Editor - Info Page - Event Page


- Model Page

- Adjustment Page - Alert Page Display Options Motor Starting Plots - Plot Display

Motor Starting Calculation Methods

- Motor Starting Required Data Motor Starting Output Reports






Alert View - Motor Starting Analysis

After the motor starting calculation is completed, ETAP checks any abnormal operating conditionsaccording to alert limits you set in the Alert page of Motor Starting Study Case. If any abnormal conditionshave been determined, alerts will be generated and reported in Alert View as well as in the Crystal Reports

format report. The Alert View can be brought up by clicking the Alert View button in the Motor Starting

toolbar. If you have selected the Auto Display option in the Alert page of Motor Starting Study Case, theAlert View will open automatically when alerts are generated. The following is a sample Alert View,

which displays alerts for various bus Under Voltage and Motor Fail To Start alerts.


Toolbars - Time Slider Toolbar Study Case Editor

- Info Page - Event Page - Add Action by Starting Category

- Add Action by Load - Model Page - Adjustment Page - Alert Page Display Options

Motor Starting Plots

- Plot Display Motor Starting Calculation Methods

- Motor Starting Required Data Motor Starting Output Reports One-Line Diagram Display Alert View
