IEEE Std C57.12.34 pdf free download

IEEE Std C57.12.34 pdf free download.Pad-Mounted, Compartmental-Type, Self-Cooled, Three-Phase Distribution Transformers, 10 MVA and Smaller; High-Voltage, 34.5 kV Nominal System Voltage and Below; Low-Voltage, 15 kV Nominal System Voltage and Below.
8.7.2 Terminals greater than 600 V
8.7.2.1 General
The number, location, and arrangement of the terminals described by this section shall be as shown in Figure I,
Figure 2, Figure 3, Figure 5, Figure 6, Figure 7, Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14.
Figure 15, Figure 16, Figure 17, or Figure 18.
8.7.2.2 Bushing replacement
The terminals described by this subclause, whether bushing wells and bushing inserts, integral bushings, or bushings shall be externally replaceable. The inside terminal connections shall be externally removable through the connector’s opening in the transformer tank, or accessible through a handhole to permit removal and replacement.
8.7.2.4 Voltage terminals using high-voltage bushings
Bushings shall have either tin-plated copper alloy clamp-type connectors or a two-hole spade terminal, both being arranged for a vertical take-off. The clamp connectors shall accommodate No. 6 AWG solid to 250 kcmil stranded conductors. The holes in the spade terminal shall be on the same plane, of a diameter of 14.3 ± 0.8 mm (0.56 ± 0.03 in) typical and be 44.5 ± 0.8 mm (1.75 ± 0.03 in) center to center.
8.7.3 600 V and below terminals
8.7.3.1 General
The phase and neutral terminals shall be in accordance with Figure 4 or Figure 8 of this standard and arranged for vertical take-off Terminal dimensions shall be as shown in Figure 19 of this standard or, if specified. Figure 20 of this standard.
8.9.2 Pressure relief
A replaceable valve shall be provided to relieve pressures that build up slowly in excess of normal operating pressures. These excess pressures may be due to overloads, high ambient temperatures, external secondary faults, and incipient faults in the low-voltage winding. When relieving these excess pressures. the valve shall emit only a negligible amount of oil. The valve shall be furnished in the low-voltage compartment on the tank wall above the 140 °C top oil level, by the manufacturer’s calculation, and shall be located so as not to interfere with use of the low- voltage terniinals or the operating handle of the low-voltage circuit breaker. The inlet port shall be 1/4 inch or larger NPT (or NF thread with gasket), sized for a specified minimum flow rate. Exposed parts shall be of weather- and corrosion-resistant materials. Gaskets and 0-rings shall withstand oil vapor and a 105 °C temperature continuous under operating conditions as described in IEEE Std C57.91 [B4], without seizing or deteriorating, for the life of the transformer. The valve shall have a pull ring for manually reducing pressure to the atmosphere using a standard hook- stick and shall be capable of withstanding a static pull force of 112 newtons (25 Ib) for one minute without permanent deformation. The valve shall withstand a static force of 445 newtons (100 Ib) for one minute applied normal to its longitudinal axis at the outermost extremity of the body. When specified, the venting port, on the outward side of the valve head set, shall be protected to prevent entry of dust, moisture, and insects before and after the valve has actuated: or a weather-cap-type indicator shall be provided, which will remain attached to the valve and provide positive indication to an observer that the valve has operated. Venting and sealing characteristics shall be as follows:
— Cracking pressure: 69 kPa (gauge) ± 13 kPa (gaugc)(10 psig ± 2 psig)
— Resealing pressure: 42 kPa (gauge) (6 psig) minimum
IEEE Std C57.12.34 pdf download.