Common use of Short Time Emergencies Clause in Contracts

Short Time Emergencies. Disconnect switches can be subjected to currents higher than those calculated using Equation (3), above, for periods not exceeding the thermal time constant of the switch, generally 30 minutes. The permissible Short-Time Emergency (STE) and Drastic Action Limit (DAL) currents can be calculated using the following Equation (4) and substituting 15 minutes or 5 minutes, respectively, for the time duration, d: Ie(st) = ⎡ 1 ⎛ θ max − θ max e ⎞⎤ Ir ⎢ ⎜ + θ max− θa ⎟ 0.5 Equation (4) ⎜ ⎥ ⎢θr 1 − e−d /τ ⎟⎥ Where: ⎣ ⎝ ⎠⎦ Ie(st) is the permissible short time current, and τ is the thermal time constant of the switch in minutes Values of τ may be conservatively assumed to be 30 minutes for switches rated 1200 Amperes or greater. Contact the manufacturer for switches rated less than 1200 Amperes.

Short Time Emergencies. Disconnect switches can be subjected to currents higher than those calculated using Equation (3), above, for periods not exceeding the thermal time constant of the switch, generally 30 minutes. The permissible Short-Time Emergency (STE) and Drastic Action Limit (DAL) currents can be calculated using the following Equation (4) and substituting 15 minutes or 5 minutes, respectively, for the time duration, d:  1   max   max  0.5 Ie(st) = ⎡ 1 ⎛ θ max − θ max Ir   e ⎞⎤ Ir ⎢ ⎜ + θ max− θa ⎟ 0.5   max a  Equation (4) ⎜ ⎥ ⎢θr r  1 − e−d /τ ⎟⎥  ed /     Where: ⎣ ⎝ ⎠⎦ Ie(st) is the permissible short time current, and τ is the thermal time constant of the switch in minutes Values of τ  may be conservatively assumed to be 30 minutes for switches rated 1200 Amperes or greater. Contact the manufacturer for switches rated less than 1200 Amperes.