Risk Assessment / JSA

Battery Arc Flash Calculator

This tool is used to calculate the potential arc flash hazard of a battery, and therefore the level of PPE required when working on it. 

The arc flash incident energy for battery systems is calculated by:

IE_m = 0.01 x V_sys x I_arc x (T_arc/D²) x MF

 

Battery mounted in enclosure?

Only select this box if the battery is mounted in a separate enclosure (box).  This increases the Multiplying Factor to 3.

For battery rooms = 1.5

Multiplying factor 

An enclosure or box can mean that the amount of energy dissipated in the direction of the person working on the battery could be increased. The factor by which this is increased is known as the multiplying factor. 

For battery system enclosures and BESS enclosures, a minimum multiplying factor of 3 is applied. For battery rooms, a minimum multiplying factor of 1.5 is applied.

Battery intra-string protection installed?

Common scenarios: lead acid battery banks with a fuse installed within the string (before the terminals). 

Protection device I_trip value

This is the I_trip rating of the intra-string fuse. This value is considerably higher than the nominal current of the fuse. Consult manufacturer's specifications. 

 

Unprotected battery fault current / prospective fault current - I_bf 

The prospective fault current (prospective short circuit current) at the battery terminals of the battery system. This information should be provided by the battery manufacturer.

The I_bf is usually greater than the nominal current rating of a fuse/CB integrated in the battery system.

For lead acid battery banks, this is the battery voltage divided by the internal resistance - check the manufacturer's specifications. 

Arc Flash

Electrical explosion or discharge, which occurs between electrified conductors during a fault or short circuit condition

Arc flash incident energy - IE_m

Measurement applied to determine the available incident arc flash energy at a specified distance originating from an arc flash. 

Arc flash protection boundary

Boundary marked by the distance from electrical equipment as which the arc flash incident energy is equal to 1.2 cal/cm2. This is used to define where PPE may be required. 

Arcing time - T_arc

For work being undertaken on the PCE side of the battery system's protection device, the operating time for the protection based on the prospective fault current shall be used as the arcing time. 

If the operational time of the protective device is unknown, an arcing time of 2 seconds should be used.

Working distance - D

A maximum working distance of 45cm is used. 

Arcing current - I_arc

Calculated at 0.5 x I_bf  (battery prospective fault current, in amps. )