[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

With the movement to deregulate electric utilities in the U.S., most utilities have now chosen to neglect
elements of system cost that no longer may apply or to abandon entirely the consideration of the effects
of transformer losses on the efficiency of their distribution system. Typical loss evaluation factors in the
year 2003 are A = $2.50/W and B = $0.80/W.
References
ABB, Distribution Transformer Guide, Distribution Transformer Division, ABB Power T&D Co., Raleigh,
NC, 1995, pp. 40–70.
ANSI, Requirements for Pad-Mounted, Compartmental-Type, Self-Cooled, Single-Phase Distribution
Transformers with Separable Insulated High Voltage: High Voltage (34,500 GrdY/19,920 V and
Below); Low Voltage (240/120 V, 167 kVA and Smaller), C57.12.25-1990, Institute of Electrical and
Electronics Engineers, Piscataway, NJ, 1990.
ANSI, Standard for Switchgear and Transformers: Pad-Mounted Equipment — Enclosure Integrity for
Coastal Environments, C57.12.29-1991, Institute of Electrical and Electronics Engineers, Piscataway,
NJ, 1991.
ANSI, Standard for Requirements for Secondary Network Transformers — Subway and Vault Types
(Liquid Immersed) Requirements, IEEE C57.12.40-2000, Institute of Electrical and Electronics
Engineers, Piscataway, NJ, 2000a.
ANSI, Underground-Type Three-Phase Distribution Transformers: 2500 kVA and Smaller; High-Voltage,
34,500 GrdY/19,920 Volts and Below; Low Voltage, 480 Volts and Below — Requirements,
C57.12.24-2000, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 2000b.
ANSI, Submersible Equipment — Enclosure Integrity, C57.12.32-2002, Institute of Electrical and Electronics
Engineers, Piscataway, NJ, 2002a.
ANSI/NEMA, Pad-Mounted Equipment — Enclosure Integrity, ANSI/NEMA C57.12.28-1999, National
Electrical Manufacturers Association, Rosslyn, VA, 1999.
Bean, R.L., Chackan, N., Jr., Moore, H.R., and Wentz, E.C., Transformers for the Electric Power Industry,
Westinghouse Electric Corp. Power Transformer Division, McGraw-Hill, NY, 1959, pp. 338–340.
Claiborne, C.C., ABB Electric Systems Technology Institute, Raleigh, NC, personal communication, 1999.
Galloway, D.L., Harmonic and DC Currents in Distribution Transformers, presented at 46th Annual
Power Distribution Conference, Austin, TX, 1993.
Hayman, J.L., E.I. duPont de Nemours & Co., letter to Betty Jane Palmer, Westinghouse Electric Corp.,
Jefferson City, MO, October 11, 1973.
IEEE, Guide for Application of Transformer Connections in Three-Phase Distribution System, IEEE
C57.105-1978, section 2, Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1978a.
IEEE, Standard Terminology for Power and Distribution Transformers, IEEE C57.12.80-2002, clause 2.3,
Institute of Electrical and Electronics Engineers, Piscataway, NJ, 2002b.
IEEE, Standard for Transformers: Underground-Type, Self-Cooled, Single-Phase Distribution Transformers
with Separable, Insulated, High-Voltage Connectors; High Voltage (24,940 GrdY/14,400 V and
Below) and Low Voltage (240/120 V, 167 kVA and Smaller), C57.12.23-2002, Institute of Electrical
and Electronics Engineers, Piscataway, NJ, 2002c.
IEEE, Standard Requirements for Secondary Network Protectors, C57.12.44-2000, Institute of Electrical
and Electronics Engineers, Piscataway, NJ, 2000c.
IEEE, Guide for Loading Mineral-Oil-Immersed Transformers, IEEE C57.91-1995, Institute of Electrical
and Electronics Engineers, Piscataway, NJ, 1995, p. iii.
IEEE, Recommended Practice for Establishing Transformer Capability when Supplying Nonsinusoidal
Load Currents, C57.110-1998, Institute of Electrical and Electronics Engineers, Piscataway, NJ,
1998.
IEEE, Standard General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers,
C57.12.00-2000, Institute of Electrical and Electronics Engineers, Piscataway, NJ,
2000d.
IEEE, Guide for Distribution Transformer Loss Evaluation, C57.12.33, Draft 8-2001, Institute of Electrical
and Electronics Engineers, Piscataway, NJ, 2001.
Myers, S.D., Kelly, J.J., and Parrish, R.H., A Guide to Transformer Maintenance, footnote 12, Transformer
Maintenance Division, S.D. Myers, Akron, OH, 1981.
Oommen, T.V. and Claiborne, C.C., Natural and Synthetic High Temperature Fluids for Transformer
Use, internal report, ABB Electric Systems Technology Institute, Raleigh, NC, 1996.
Palmer, B.J., History of Distribution Transformer Core/Coil Design, Distribution Transformer Engineering
Report No. 83-17, Westinghouse Electric, Jefferson City, MO, 1983.
Powel, C.A., General considerations of transmission, in Electrical Transmission and Distribution Reference
Book, ABB Power T&D Co., Raleigh, NC, 1997, p. 1.
2.3 Phase-Shifting Transformers
Gustav Preininger
2.3.1 Introduction
The necessity to control the power flow rose early in the history of the development of electrical power
systems. When high-voltage grids were superimposed on local systems, parallel-connected systems or
transmission lines of different voltage levels became standard. Nowadays large high-voltage power grids
are connected to increase the reliability of the electrical power supply and to allow exchange of electrical
power over large distances. Complications, attributed to several factors such as variation in powergeneration
output and/or power demand, can arise and have to be dealt with to avoid potentially
catastrophic system disturbances. Additional tools in the form of phase-shifting transformers (PSTs) are
available to control the power flow to stabilize the grids. These may be justified to maintain the required
quality of the electrical power supply.
To transfer electrical power between two points of a system, a difference between source voltage (V S )
and load voltage (V L ) in quantity and/or in phase angle is necessary. See Figure 2.3.1. Using the notation
of Figure 2.3.1, it follows that:
Z R jX Z e j Z
*
Z R X
Z
2 2
X
arc tan( )
R
V V *( cos + jsin
), V V *( cos - jsin
)
S S S S L L L L
V V S
– V L
V (V * cos V * cos ) j( V *sin V *sin ) V*
e
S S L L S S L L
2
V V 2*V *V * cos( ) V
S
2
S L S L L
j
(2.3.1)
(2.3.2)
(2.3.3)
(2.3.4)
(2.3.5)
(2.3.6)
(2.3.7)
© 2004 by CRC Press LLC
© 2004 by CRC Press LLC