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Transformer#

( Circuit Element, PD Element )

EPRI’s OpenDSS Documentation for this component: https://opendss.epri.com/Transformer1.html

#

Name

Type

Default

Units

Description

1

Phases

integer

3

Number of phases this transformer.

2

Windings

integer

Number of windings, this transformers. (Also is the number of terminals) This property triggers memory allocation for the Transformer 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. 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.

6

kV

real
(on array)

kV

For 2-or 3-phase, enter phase-phase kV rating. Otherwise, kV rating of the actual winding

7

kVA

real
(on array)

Base kVA rating of the winding. Side effect: forces change of max normal and emergency kVA ratings.If 2-winding transformer, 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 resistance this winding. (half of total for a 2-winding).

10

RNeut

real
(on array)

Ω

Neutral resistance of wye (star)-connected winding in actual ohms. If entered as a negative value, the neutral is assumed to be open, or floating. To solidly ground the neutral, connect the neutral conductor to Node 0 in the Bus property spec for this winding. For example: Bus=MyBusName.1.2.3.0, which is generally the default connection.

11

XNeut

real
(on array)

Ω

Neutral reactance of wye(star)-connected winding in actual ohms. May be positive or negative.

12

Buses

array of strings
(bus defs., on array)

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

New Transformer.T1 buses=“Hibus, lowbus”
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 Transformer.T1 buses=“Hibus, lowbus” ~ conns=(delta, wye)
Redundant with Conn

14

kVs

array of reals

kV

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

New Transformer.T1 buses=“Hibus, lowbus”
~ conns=(delta, 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

XHL

real

Use this to specify the percent reactance, H-L (winding 1 to winding 2). Use for 2- or 3-winding transformers. On the kVA base of winding 1. See also X12.
Redundant with X12

18

XHT

real

Use this to specify the percent reactance, H-T (winding 1 to winding 3). Use for 3-winding transformers only. On the kVA base of winding 1. See also X13.
Redundant with X13

19

XLT

real

Use this to specify the percent reactance, L-T (winding 2 to winding 3). Use for 3-winding transformers only. On the kVA base of winding 1. See also X23.
Redundant with X23

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 transformer. 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. Default is 0. 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). 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). 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 transformer is to be considered a substation.Default is No.

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. Default is null. 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 transformer 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 %resistances using an array. Example:

New Transformer.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.

39

XfmrCode

string
(XfmrCode name)

Name of a library entry for transformer properties. The named XfmrCode must already be defined.

40

XRConst

boolean

False

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

41

X12

real

Alternative to XHL for specifying the percent reactance from winding 1 to winding 2. Use for 2- or 3-winding transformers. Percent on the kVA base of winding 1.

42

X13

real

Alternative to XHT for specifying the percent reactance from winding 1 to winding 3. Use for 3-winding transformers only. Percent on the kVA base of winding 1.

43

X23

real

Alternative to XLT for specifying the percent reactance from winding 2 to winding 3.Use for 3-winding transformers only. Percent on the kVA base of winding 1.

44

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”

45

WdgCurrents

string
(read-only)

(Read only) Makes winding currents available via return on query (? Transformer.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

46

Core

string
(from enum. Core Type)

shell

Core Type. Used for GIC analysis

47

RDCOhms

real
(on array)

Winding dc resistance in OHMS. Useful for GIC analysis. From transformer test report. Defaults to 85% of %R property

48

Seasons

integer

Defines the number of ratings to be defined for the transformer, to be used only when defining seasonal ratings using the “Ratings” property.

49

Ratings

array of reals

[1100.0]

An array of ratings to be used when the seasonal ratings flag is True. It can be used to insert
multiple ratings to change during a QSTS simulation to evaluate different ratings in transformers. Is given in kVA

50

NormAmps

real

Normal rated current.

51

EmergAmps

real

Maximum or emergency current rating.

52

FaultRate

real

0.007

Transformer.faultrate

53

pctPerm

real

0.0

Percent of failures that become permanent.

54

Repair

real

0.0

Hours to repair.

55

BaseFreq

real

Hz

Base Frequency for ratings.

56

Enabled

boolean

True

Indicates whether this element is enabled.

57

Like

string
(Transformer name)
deprecated

Make like another object, e.g.:

New Capacitor.C2 like=c1 …