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AutoTrans#

( Circuit Element, PD Element )

EPRI’s OpenDSS Documentation for this component: https://opendss.epri.com/AutoTrans.html

#

Name

Type

Default

Units

Description

1

Phases

integer

3

Number of phases this AutoTrans.

2

Windings

integer

Number of windings, this AutoTrans. (Also is the number of terminals) This property triggers memory allocation for the AutoTrans and will cause other properties to revert to default values.

3

Wdg

integer

Set this = to the number of the winding you wish to define. Then set the values for this winding. Winding 1 is always the Series winding. Winding 2 is always Common winding (wye connected). Repeat for each winding. Alternatively, use the array collections (buses, kVAs, etc.) to define the windings. Note: reactances are BETWEEN pairs of windings; they are not the property of a single winding.

4

Bus

string
(bus def., on array)

Bus connection spec for this winding.

5

Conn

string
(from enum. Connection, on array)

Connection of this winding. Default is “wye” with the neutral solidly grounded.
For AutoTrans, Winding 1 is always Series and Winding 2 (the Common winding) is always Wye.
If only 2 windings, no need to specify connections.

6

kV

real
(on array)

kV

For 2-or 3-phase, enter phase-phase kV rating. Otherwise, kV rating of the actual winding. Specify H terminal kV rating for Series winding.

7

kVA

real
(on array)

Base kVA rating of the winding. Side effect: forces change of max normal and emerg kVA ratings.If 2-winding AutoTrans, forces other winding to same value. When winding 1 is defined, all other windings are defaulted to the same rating and the first two winding resistances are defaulted to the %loadloss value.

8

Tap

real
(on array)

Per unit tap that this winding is on.

9

%R

real
(on array)

Percent ac resistance this winding. This value is for the power flow model.Is derived from the full load losses in the transformer test report.

10

RDCOhms

real
(on array)

Winding dc resistance in OHMS. Specify this for GIC analysis. From transformer test report (divide by number of phases). Defaults to 85% of %R property (the ac value that includes stray losses).

11

Core

string
(from enum. Core Type)

shell

Core Type. Used for GIC analysis in auxiliary programs. Not used inside OpenDSS.

12

Buses

array of strings
(bus defs., on array)

Use this to specify all the bus connections at once using an array. Example:

New AutoTrans.T1 buses=[Hbus, Xbus]
Redundant with Bus

13

Conns

array of strings
(from enum. Connection)

Use this to specify all the Winding connections at once using an array. Example:

New AutoTrans.T1 buses=[Hbus, Xbus] ~ conns=(series, wye)
Redundant with Conn

14

kVs

array of reals

Use this to specify the kV ratings of all windings at once using an array. Example:

New AutoTrans.T1 buses=[Hbus, Xbus]
~ conns=(series, wye)
~ kvs=(115, 12.47)

See kV= property for voltage rules.
Redundant with kV

15

kVAs

array of reals

Use this to specify the kVA ratings of all windings at once using an array.
Redundant with kVA

16

Taps

array of reals

Use this to specify the p.u. tap of all windings at once using an array.
Redundant with Tap

17

XHX

real

Use this to specify the percent reactance, H-L (winding 1 to winding 2). Use for 2- or 3-winding AutoTranss. On the kVA base of winding 1(H-X).

18

XHT

real

Use this to specify the percent reactance, H-T (winding 1 to winding 3). Use for 3-winding AutoTranss only. On the kVA base of winding 1(H-X).

19

XXT

real

Use this to specify the percent reactance, L-T (winding 2 to winding 3). Use for 3-winding AutoTranss only. On the kVA base of winding 1(H-X).

20

XSCArray

array of reals

Use this to specify the percent reactance between all pairs of windings as an array. All values are on the kVA base of winding 1. The order of the values is as follows:

(x12 13 14… 23 24.. 34 ..)

There will be n(n-1)/2 values, where n=number of windings.

21

Thermal

real

2.0

hour

Thermal time constant of the AutoTrans. Typically about 2.
Not used

22

n

real

0.8

n Exponent for thermal properties in IEEE C57. Typically 0.8.
Not used

23

m

real

0.8

m Exponent for thermal properties in IEEE C57. Typically 0.9 - 1.0
Not used

24

FLRise

real

65.0

°C

Temperature rise for full load.
Not used

25

HSRise

real

15.0

°C

Hot spot temperature rise
Not used

26

%LoadLoss

real

Percent load loss at full load. The %R of the High and Low windings (1 and 2) are adjusted to agree at rated kVA loading.

27

%NoLoadLoss

real

Percent no load losses at rated excitation voltage. Converts to a resistance in parallel with the magnetizing impedance in each winding.

28

NormHkVA

real

kVA

Normal maximum kVA rating of H winding (winding 1+2). Usually 100% - 110% of maximum nameplate rating, depending on load shape. Defaults to 110% of kVA rating of Winding 1.

29

EmergHkVA

real

kVA

Emergency (contingency) kVA rating of H winding (winding 1+2). Usually 140% - 150% of maximum nameplate rating, depending on load shape. Defaults to 150% of kVA rating of Winding 1.

30

Sub

boolean

False

Designates whether this AutoTrans is to be considered a substation.

31

MaxTap

real
(on array)

Max per unit tap for the active winding.

32

MinTap

real
(on array)

Min per unit tap for the active winding.

33

NumTaps

integer

(on array)

Total number of taps between min and max tap. Default is 32 (16 raise and 16 lower taps about the neutral position). The neutral position is not counted.

34

SubName

string

Substation Name. Optional. If specified, printed on plots

35

%IMag

real

Percent magnetizing current. Magnetizing branch is in parallel with windings in each phase. Also, see “ppm_antifloat”.

36

ppm_Antifloat

real

1.0

Default=1 ppm. Parts per million of AutoTrans winding VA rating connected to ground to protect against accidentally floating a winding without a reference. If positive then the effect is adding a very large reactance to ground. If negative, then a capacitor.

37

%Rs

array of reals

Use this property to specify all the winding ac %resistances using an array. Example:

New AutoTrans.T1 buses=[Hibus, lowbus] ~ %Rs=(0.2 0.3)
Redundant with %R

38

Bank

string

Name of the bank this transformer is part of, for CIM, MultiSpeak, and other interfaces.
Not used

39

XRConst

boolean

False

Signifies whether or not the X/R is assumed constant for harmonic studies.

40

LeadLag

string
(from enum. Phase Sequence)

Lag

{Lead | Lag (default) | ANSI (default) | Euro } Designation in mixed Delta-wye connections the relationship between HV to LV winding. Default is ANSI 30 deg lag, e.g., Dy1 of Yd1 vector group. To get typical European Dy11 connection, specify either “lead” or “Euro”

41

WdgCurrents

string
(read-only)

(Read only) Makes winding currents available via return on query (? AutoTrans.TX.WdgCurrents). Order: Phase 1, Wdg 1, Wdg 2, …, Phase 2 …

WARNING: If the transformer has open terminal(s), results may be wrong, i.e. avoid using this in those situations. For more information, see dss-extensions/dss-extensions#24

42

NormAmps

real

6.194

Normal rated current.

43

EmergAmps

real

8.447

Maximum or emergency current rating.

44

FaultRate

real

0.007

AutoTrans.faultrate

45

pctPerm

real

0.0

Percent of failures that become permanent.

46

Repair

real

0.0

Hours to repair.

47

BaseFreq

real

Hz

Base Frequency for ratings.

48

Enabled

boolean

True

Indicates whether this element is enabled.

49

Like

string
(AutoTrans name)
deprecated

Make like another object, e.g.:

New Capacitor.C2 like=c1 …

Enumerations#

AutoTrans: Connection#

Value

wye

delta

series

y

ln

ll