Fault Current Through ICTs

Fault current through ICTs

Whenever ICTs operates in grid; manual calculations for fault current through ICTs are lengthy. Hence such calculations of fault current through the ICTs is done using simulation software at corporate office and results are shared with field. This latest data of fault currents contributed by ICTs for HV and IV bus faults shall be used while performing calculations of settings of over current and earth fault relays (called as backup relays). For calculating ICT HV side relay settings (TMS or HS) it is necessary to use current contributed by ICT for IV bus fault and vice a versa as shown in following figures.

ICTs has delta tertiary. Thus even for ICTs operating in radial Sub-Station hand calculations of fault current contributed by ICTs for IV side bus SLG fault are not straight forward. Help of some sort of computer program is essential for these calculations too. Hence manual calculations for ICT fault current are not included here. Due to delta tertiary winding of transformer single phase fault current increases. Someone may choose for calculating fault current of ICTs for three phase fault (obviously need not to consider tertiary) and may consider 80% to 90% of this fault current for single phase fault for approximation.