IEEE C57.12.20-2005 pdf free

IEEE C57.12.20-2005 pdf free.IEEE Standard for Overhead-Type Distribution Transformers, 500 kVA and Smaller: High Voltage, 34 500 V and Below; Low Voltage, 7970/13 800Y V and Below.
7.1.2.1 High-voltage terminals
Terminal details shall be as shown in Figure 5a. High-voltage bushings of transformers 2(X) kV BIL and below shall bc equipped with tinned, copper-alloy soldcrless connectors. High-voltage terminal sizes shall be as shown in Table X.
7.1.2.2 Low-voltage terminals
Terminal details shall be as shown in Figure Sa and Figure 5b. Low-voltage terminal sizes shall be as shown in Table 9. Terminals of low-voltage windings 600 V and below shall be arranged for vertical take-off.
External spacing between low-voltage bushing terminals shall be such as to provide the maximum clearance between live metal parts in the working area, For low-voltage ratings above 60(1 V. the electrical characteristics of the bushings determine the spacing. For low-voltage ratings 600 V and below, spacing shall be within the limits of Table 10.
7.1.3 Neutral termination
On single-phase transformers having one high-voltage bushing. the H2 end of the winding shall be securely connected internally to the grounded clamping structure or the tank. This connection shall be independent of all other electrical connections.
On all three-phase transformers, a fully insulated low-voltage neutral bushing, X0. shall be provided when the low-voltage windings are wye-connected.
On three-phase transformers, a fully insulated high-voltage neutral bushing, H0, and a fully insulated low- voltage neutral bushing. X(p. shall be provided where wye-connected high-voltage windings are rated 8.32Y kV and below and low-voltage windings are rated 208Y’l20 V or4SOY.277 V.
On three-phase transformers, a common fully insulated low-voltage-type neutral bushing. lL>X. shall be provided where wye-connccted high-voltage windings are rated above 8.32Y kV and low-voltage windings arc rated 208Y1 120 V or 480Y1277 V. The high-voltage and low-voltage neutrals shall be connected internally by a link that is accessible and capable of reconnection.
7.1.4 Terminal boards
On single-phase transformers with low-voltage ratings of 120240 V or 240/4X0 V. the internal connections to the low-voltage bushings on sizes 100 kVA and smaller shall be arranged to serve in lieu of a low- voltage terminal board. These connections shall be in contbrmancc with and arranged as shown in Figure 6.IEEE C57.12.20 pdf free download.