[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

FIGURE 2.6.29 5-kV three-phase/four-wire metering rack with 3 VT and 3 CT. (Photo courtesy of Kuhlman Electric
Corp.)
FIGURE 2.6.30 34.5-kV three-phase oil-filled metering unit. (Photo courtesy of Kuhlman Electric Corp.)
products, 5 kV through 34.5 kV (Figure 2.6.29), but they are also available in oil-filled units (Figure
2.6.30). It is a prewired assembly with all of the elements’ secondary leads connected to a common
junction box for easy access. The elements can be in any combination needed to provide accurate energy
measurement. For three-phase/four-wire installations use either 2 1 / 2- or 3-element arrangements, and
for three-phase/three-wire installations use 2-element arrangements. There are even single-phase assemblies
available for special applications.
When measuring energy usage for the purposes of revenue billing, and knowing the RCF and phaseangle
readings of each element, the watts or watt-hours can be corrected by multiplying the reading by
the product of [TCF CT ][TCF VT ].
2.6.4.15 New Horizons
With deregulation of the utility industry, the buying and selling of power, the leasing of power lines, etc.,
the need for monitoring power at the transmission and distribution level will increase. There will be a
need to add more metering points within existing systems beginning at the generator. The utilities will
want to add this feature at the most economical cost. The use of window-type slipover CTs for revenue
metering will drive the industry toward improved performance. The need for higher accuracies at all
levels will be desired and can be easily obtained with the use of low-burden solid-state devices. Products
will become more environmentally safe and smaller in size. To help the transformer industry fulfill these
needs, steel producers will need to make improvements by lowering losses and increasing initial permeability
and developing new composites.
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© 2004 by CRC Press LLC
© 2004 by CRC Press LLC