This section contains parameters of 3-winding transformers. All the per-unit impedances and admittances for 3-winding transformers are based on the transformer’s own MVA base and the tap voltages. The grounding impedances are in ohms and should be entered without any multiplication by 3. The first line in the section must say: [3W TRANSFORMER DATA]. This is followed by the data described below. A blank line ends the section.
1. Bus1 Name: Bus name at one end of the transformer, enclosed in quotation marks.
2. Bus1 Base kV: Nominal kV of Bus1.
3. Bus2 Name: Bus name at the other end of the transformer, enclosed in quotation marks.
4. Bus2 Base kV: Nominal kV of Bus2.
5. Tertiary-Bus Name: Bus name at the tertiary terminal, enclosed in quotation marks.
6. Tertiary-Bus Nominal kV: Nominal kV (line-to-line) of the tertiary-terminal bus.
7. Circuit Identifier: A two-character identifier. Transformers with two or more terminal buses in common must have different circuit identifiers. The circuit identifier is enclosed in quotation marks.
8. In-Service Flag: 1 if the transformer is in-service; 0 if it is not. The default value is 1.
9. Meter Flag: 0 if the transformer is metered at Bus1; 100 if it is metered at Bus2. No other values are allowed.
10. Branch Name: A 12-character name for the transformer, enclosed in quotation marks. The branch name is blank by default.
11. Bus1 Tap kV: The Bus1 winding tap voltage in kV, line-to-line. The default is the nominal kV of Bus1.
12. Bus2 Tap kV: The Bus2 winding tap voltage in kV, line-to-line. The default is the nominal kV of Bus2.
13. Tertiary Tap kV (line-to-line): The default is the nominal kV of the tertiary terminal.
14. Auto-Transformer Flag : 1 if the transformer is an auto-transformer; 0 if it is not.
15. RPS: Real part of the positive-sequence short-circuit impedance measured at the Bus1 terminal with the Bus2 terminal short circuited and the tertiary terminal open. RPS and XPS are in per-unit, based on the transformer’s own MVA base and the tap kVs.
16. XPS: Imaginary part of the positive-sequence short-circuit impedance measured at the Bus1 terminal with the Bus2 terminal short circuited and the tertiary terminal open.
17. RPT: Real part of the positive-sequence short-circuit impedance measured at the Bus1 terminal with the tertiary terminal short circuited and the Bus2 terminal open. RPT and XPT are in per-unit, based on the transformer’s own MVA base and the tap kVs.
18. XPT: Imaginary part of the positive-sequence short-circuit impedance measured at the Bus1 terminal with the tertiary terminal short circuited and the Bus2 terminal open.
19. RST: Real part of the positive-sequence short-circuit impedance measured at the Bus2 terminal with the tertiary terminal short circuited and the Bus1 terminal open. RST and XST are in per-unit, based on the transformer’s own MVA base and the tap kVs.
20. XST: Imaginary part of the positive-sequence short-circuit impedance measured at the s Bus2 terminal with the tertiary terminal short circuited and the Bus1 terminal open.
21. B: Positive-sequence magnetizing susceptance in per unit, base on the transformer’s own MVA base and the tap kVs. The same susceptance is used in the negative-sequence model. B must be zero or negative.
22. RPS0: Same meaning as RPS, except RPS0 is for the zero sequence.
23. XPS0: Same meaning as XPS, except XPS0 is for the zero sequence.
24. RPT0: Same meaning as RPT, except RPT0 is for the zero sequence.
25. XPT0: Same meaning as XPT, except XPT0 is for the zero sequence.
26. RST0: Same meaning as RST, except RST0 is for the zero sequence.
27. XST0: Same meaning as XST, except XST0 is for the zero sequence.
28. B0: Same meaning as B, except B0 is for the zero sequence.
29. Bus1 Winding Configuration: ‘G’ if wye connected; ‘D’ if delta connected. The default value is ‘G’ The table below lists the winding configuration codes for the different transformer types supported by the program:
1. Wye-wye-wye: Winding config.=’GGG’; Test config.=’GGG’; Auto flag=0
2. Auto-wye-wye: Winding config.=’GGG’; Test config.=’GGG’; Auto flag=1
3. Wye-wye-delta, delta lags: Winding config.=’GGD’; Test config.=’GGD’; Auto flag=0
4. Wye-wye-delta, delta leads: Winding config.=’GGE’; Test config.=’GGD’; Auto flag=0
5. Auto-wye-delta, delta lags: Winding config.=’GGD’; Test config.=’GGD’; Auto flag=1
6. Auto-wye-delta, delta leads: Winding config.=’GGE’; Test config.=’GGD’; Auto flag=1
7. Wye-delta-delta, delta lags: Winding config.=’GDD’; Test config.=’GDD’; Auto flag=0
8. Wye-delta-delta, delta leads: Winding config.=’GEE’; Test config.=’GDD’; Auto flag=0
9. Delta-delta-delta: Winding config.=’DDD’; Test config.=’GGG’; Auto flag=0
30. Bus2 Winding Configuration: ‘G’ if wye connected, ‘D’ if delta connected and the delta is lagging the wye winding, or ‘E’ if delta connected and the delta is leading. See table in item 29.
31. Tertiary Winding Configuration: G if wye connected, D if delta (lagging) connected and E if delta (leading) connected. The default value is G.
32. Bus2 Winding Configuration in Test: (Note: The Bus1 winding configuration in test is assumed to be ‘G’ always.) The Bus2 winding configuration in test is G if wye connected; D if delta connected and the delta was closed during the test. See table in item 29.
33. Tertiary Winding Configuration in Test: G if wye connected; D if delta connected and the delta was closed during the test. See table in item 29.
34. RG1: Grounding resistance in ohms. This is meaningful only if the Bus1 winding configuration in use is G.
35. XG1: Grounding reactance in ohms. Meaningful only if the Bus1 winding configuration in use is G.
36. RG2: Grounding resistance in ohms. Meaningful only if the Bus2 winding configuration in use is G.
37. XG2: Grounding reactance in ohms. Meaningful only if the Bus2 winding configuration in use is G.
38. RGN: Grounding resistance in ohms. Meaningful only if both Bus1 and Bus2 winding configurations in use are G.
39. XGN: Grounding reactance in ohms. Meaningful only if both Bus1 and Bus2 winding configurations in use are G.
40. RG3: Grounding resistance in ohms. Meaningful only if the tertiary winding configuration in use is G.
41. XG3: The grounding reactance in ohms. Meaningful only if the tertiary winding configuration in use is G.
42. Number of Ratings to follow: Must be 3.
43. MVA Rating 1: Three-phase MVA rating of transformer. Default value is 0.0.
44. MVA Rating 2: Three-phase MVA rating of transformer. Default value is 0.0.
45. MVA Rating 3: Three-phase MVA rating of transformer. Default value is 0.0.
46. Fictitious Bus Number: The fictitious bus number must be in the range 1-99999, inclusive. The default value is 0. When exporting the data to the PTI format (Version 26 or earlier) and the GE PSLF format, Power Flow assigns this number to the middle, fictitious bus of the equivalent T model.
47. Base MVA: All the transformer impedances and admittances are based on this MVA base. The default is the system MVA base.
48. LTC Side: 0 if the transformer does not have a movable tap or if the tap is locked. 1 if the movable tap is on the Bus1 side, 2 if it is on the Bus2 side, and 3 if it is on the Bus3 side.
49. LTC Type: 0 if the LTC regulates the voltage magnitude. 1 if the LTC regulates the MVAR flow. The MVAR regulation has not been implemented in the current version.
50. Minimum Tap: Minimum tap voltage in per-unit. The default is 0.51.
51. Maximum Tap: Maximum tap voltage in per-unit. The default is 1.50.
52. Step Size: The tap increment in per-unit. Specify 0.0 if the tap is continuous. The default is 0.00625.
53. Minimum Target: The minimum per-unit voltage or the minimum MVAR flow. The default is 0.51.
54. Maximum Target: The maximum per-unit voltage or the maximum MVAR flow. The default is 1.50.
55. Regulated Bus Name: Name of the bus whose voltage magnitude is to be regulated by the LTC. The bus name is enclosed in quotation marks.
56. Regulated Bus Base kV: Nominal kV of the bus whose voltage magnitude is to be regulated by the LTC. Set the Regulated Bus Name to blank and the Regulated Bus Base kV to 0 if the LTC is locked or if it is regulating MVAR flow.
57. LTC center tap kV: Load tap changer center position in kV.
58. LTC Ganged Flag: 1 if this LTC moves in unison with other LTCs that control the same bus voltage. 0 otherwise.
59. LTC Adjustment Priority: 0 if ‘normal’, 1 if ‘medium’, and 2 if ‘high’.
60. Memo: Comments with a maximum of 512 characters. Any alpha-numeric characters can be used, except for the string delimiter (single or double quotation mark). The comment text is enclosed in quotation marks.
61. Tags: Tag string with a maximum of 512 characters. Tags in string are separated by semicolon. Any alpha-numeric characters can be used, except for the string delimiter (single or double quotation mark). The tag string is enclosed in quotation marks.
62. In-service Date: Set to 0 if not available. Otherwise enter an unsigned 32-bit integer that store the year/month/date information given by the CTime object in Microsoft Foundation Class.
63. Out-of-Service Date: Set to 0 if not available. Otherwise enter an unsigned 32-bit integer that store the year/month/date information given by the CTime object in Microsoft Foundation Class.
64. UDF: User-defined data fields. Enter the list of user defined field values as a tab delimited text string enclosed in single quotes.
An example 3-winding transformer data section is shown below.
[3W TRANSFORMER DATA]
'NEVADA' 132 'NEW HAMPSHR' 33 'DOT BUS' 13.8 '1'= 1 0 'Nev/NH/Rnk' 132 33 13.8 1 /
0 0.318 0 0.416 0 0.318 0 0 0.27995 0 0.416 0 0.318 0 G G D G D 0 0 0 0 0 0 0 0 3 0 0 0 0 100 0 0 0.51 1.5 0.00625 0.51 1.5 '' 0 33.0 0 0 '' '' 0 0