IEEE Std 946-2020 pdf free download

IEEE Std 946-2020 pdf free download.IEEE Recommended Practice for the Design of DC Power Systems for Stationary Applications.
of the system intact to continue supplying power to unaffected areas. Refer to Annex C and Annex D for details and examples of battery and charger short-circuit current contributions.
8.3.1 Batteries
The short-circuit current across a battery terminal is a function of its actual voltage. internal impedance, intercell connectors impedance, and other series connected components. Note that internal impedance is significantly affected by the chemistry and internal design for all battery types. Also, the rise time when a short-circuit occurs is relatively fast. If connecting multiple battery strings in parallci. the fault current contribution from each string needs to be considered. It is recommended to contact the battery manufacturer for the maximum short-circuit current value. Refer to Annex C for calculations.
As an example, the fault current from a large vented lead-acid storage battery resulting from a bolted short at the battery terminals will typically exhibit a rate-of-rise that delivers the peak current within 17 ms. The fault current for a short at the dc distribution switchgear or panelboard peaks later (typically within 34 ms to 50 ins) depending on the cable size and layout, due to the inductance of the dc power system in series with the fault. The magnitude of the fault current for a short at the distribution bus will also be lower than the value at the battery due to the resistance of the cables between the battery terminals and the bus.
8.3.2 Chargers
The available short-circuit current at the charger output depends on the charger design topology. Two predominant designs are used:
Low-frequency rectifying chargers such as SCR, lerro-resonant, and magnetic amplifier
— High-frequency rectifying chargers commonly called switched mode chargers
Tests on current-limited low-frequency battery chargers have shown that the initial short-circuit current contributed from the battery charger can exceed the current-limited value. A large transient current spike may occur during a certain time before the charger current limit mode activates or a protective device opens.IEEE Std 946-2020 pdf free download.