IEEE C37.74-2014 pdf free

IEEE C37.74-2014 pdf free.IEEE Standard Requirements for Subsurface,Vault, and Padmounted Load-Interrupter Switchgear and Fused Load-Interrupter Switchgear for Alternating Current Systems upto38kV.
The peferred values of rated maximum voltage are those shown in Columns 1, 2, and 3 of Table 1.
5.2.1.3 Rated lighting impulse withstand voltage (Up)
The rated lightning impulse withstand voltage shall be the voltage of the way with the lowest rating. The preferred values of rated lightning impulse withstand voltage are shown in Column 4 ofTable I.
5.2.1.4 Rated power frequency withstand voltage (Ua)
The rated power-frequency withstand voltage shall be that of the way with the lowest rating. The preferred values of rated power-frequency withstand voltage are those shown in Column 5 of Table I.
5.2.1.5 Rated short-time withstand current and duration (4) (4)
The rated short circuit withstand current shall be the lowest of the fllowing ratings of any of the ways and shall be expressed in both short-time withstand and peak withstand current.
a) The rated interrupting current of the protective devices (if applicable).
b) The rated peak withstand and shor-time current of the switches, loadbreak devices (if applicable), grounding switches (if applicable), and bus.
c) The rated fault making current of the switches, loadbreak devices, protective devices, and grounding swiches (if applicable).
The relationship between the peak withstand current and short-time withstand current shall be based on a minimum peak current to root-mean-square (rms) symmetrical current ratio of 2.6 for 60 Hz and 2.5 for 50 Hz, which equates to an approximate XIR of 17 for 60 Hz systems and 14 for 50 Hz systems. These figures are based on a decay time constant of 45 ms, see Annex A. The rated short-time withstand current durationis Iso Q.
DSG consisting of only a single switched way and ways containing fuscs, may have a rated short-circuitwithstand current equal to that of the fuses if it can be demonstrated that the switch can withstand the faultmaking and peak current duty as limited by the fuses.
NOTE Bushings, separable connectors, terminators, or cables may not have short-circuit withstand capabilities as high as the rating of the DSG and could limit its application.
5.2.1.6 DC withstand voltage (required related capability)
The assembly shall pass a DC withstand voltage test in accordance with 6.7.8, with test valucs based on rated maximum voltage values shown in Column 7 ofTable 1.IEEE C37.74 pdf free download.