Symmetrical ault Calculations
Eample 1 SCC 1200 10/12.5 Calculate the fault current at
Eample 1 SCC 1200 10/12.5 Step 1: Calculate Base Values I 100 34.5 34.5 100 2 2 2898.55A 11.9ohms 100 Calculate the fault current at
Eample 1 SCC 1200 Step 2: Calculate p.u impedances Tpu t 100 0.06 12.5 old 0.48 10/12.5 Calculate the fault current at
Eample 1 SCC 1200 Step 2: Calculate p.u impedances Tpu t 100 0.06 12.5 old 0.48 10/12.5 Calculate the fault current at utility old 100 34.5 1200 34.5 0.0833 old
Eample 1 SCC 1200 Step 3: Calculate fault current I pu V pu total 1.0 0.48 + 0.0833 1.775 pu 10/12.5 Calculate the fault current at
Eample 1 SCC 1200 Step 3: Calculate fault current I pu V pu total 1.0 0.48 + 0.0833 1.775 pu 10/12.5 Calculate the fault current at I I HV LV I Ipu 3 2898.55 1.775 3 IHV 34.5 13.8 7426 A 2970 A
Eample 2 Addition of a Generator SCC 1200 10/12.5 5 0.12 Calculate the fault current at
Eample 2 Addition of a Generator Step 1: Calculate impedances SCC 1200 10/12.5 5 0.12 utility old 100 34.5 1200 34.5 0.0833 old Calculate the fault current at
Eample 2 Addition of a Generator Step 1: Calculate impedances SCC 1200 10/12.5 5 0.12 utility Tpu 100 34.5 1200 34.5 0.0833 t old 100 0.06 12.5 old 0.48 old Calculate the fault current at
Eample 2 Addition of a Generator Step 1: Calculate impedances SCC 1200 10/12.5 5 0.12 Calculate the fault current at utility Tpu Gpu 100 34.5 1200 34.5 0.0833 t old 100 0.06 12.5 G old 100 0.12 5 0.48 old 2.4 old
Eample 2 Addition of a Generator Step 2: Calculate equivalent impedances SCC 1200 1.0V 10/12.5 5 0.12 utility 0.0833 2.4 Gpu Tpu 0.48 Calculate the fault current at
utility 2.4 Eample 2 Addition of a Generator Step 2: Calculate equivalent impedances 1.0V 0.5633 * 2.4 Eq 0.5633 + 2.4 0.456 0.0833 Tpu 0.48 Gpu 0.456
Eample 2 Addition of a Generator Step 3: Calculate fault current 1.0V 0.5633 * 2.4 Eq 0.5633 + 2.4 0.456 0.0833 utility 2.4 I V 1.0 pu pu Eq 0.456 2.192 pu Tpu 0.48 Gpu 0.456
Eample 2 Addition of a Generator Step 3: Calculate fault current 1.0V 0.5633 * 2.4 Eq 0.5633 + 2.4 0.456 0.0833 utility 2.4 I V 1.0 pu pu Eq 0.456 2.192 pu Tpu 0.48 Gpu 0.456 I I HV LV I Ipu 3 2898.55 2.192 3 IHV 34.5 13.8 9170 A 3668 A
Eample 1 & 2 Comparison SCC 1200 SCC 1200 10/12.5 10/12.5 5 0.12 I 7426 Amps I 9170 Amps
Eample 3 Presence of transformer & motor SCC 1200 10/12.5 5 0.12 3 5% 2.4 M 2500 HP 0.17 Calculate the fault current at
Eample 3 Presence of transformer & motor Step 1: Calculate impedances SCC 1200 10/12.5 5 0.12 utility old 100 34.5 1200 34.5 0.0833 old 3 5% 2.4 M 2500 HP 0.17 Calculate the fault current at
Eample 3 Presence of transformer & motor Step 1: Calculate impedances SCC 1200 10/12.5 5 0.12 utility old 100 34.5 1200 34.5 0.0833 old 3 5% Tpu1 t 100 0.06 12.5 old 0.48 2.4 M 2500 HP 0.17 Calculate the fault current at
Eample 3 Presence of transformer & motor Step 1: Calculate impedances SCC 1200 10/12.5 5 0.12 utility old 100 34.5 1200 34.5 0.0833 old 3 5% Tpu1 t 100 0.06 12.5 old 0.48 M 2500 HP 0.17 2.4 Calculate the fault current at Gpu G 100 0.12 5 old 2.4
Eample 3 Presence of transformer & motor Step 1: Calculate impedances SCC 1200 utility Tpu1 Gpu 0.0833 pu 0.48 pu 2.4 pu 10/12.5 3 5% 5 0.12 Tpu2 t 100 0.05 3 old 1.667 2.4 M 2500 HP 0.17 Calculate the fault current at
Eample 3 Presence of transformer & motor Step 1: Calculate impedances SCC 1200 10/12.5 5 0.12 utility Tpu1 Gpu Tpu2 0.0833 pu 0.48 pu 2.4 pu 1.667 pu M 2500 HP 0.17 3 5% 2.4 Motor Mpu rating 2500 * 0.746 pf 1865 2154 0.866 m old 100 0.17 2.154 7.89 Calculate the fault current at
Eample 3 Presence of transformer & motor Step 1: Calculate impedances SCC 1200 10/12.5 3 5% 5 0.12 2.4 utility Tpu1 Gpu Tpu2 Mpu 0.0833 pu 0.48 pu 2.4 pu 1.667 pu 7.89 pu M 2500 HP 0.17 Calculate the fault current at
Eample 3 Presence of transformer & motor Step 2: Calculate Equivalent impedances SCC 1200 1.0V 10/12.5 5 0.12 0.0833 1.667 utility 2.4 Mpu 3 5% Tpu1 0.48 Gpu 7.89 Tpu2 2.4 M 2500 HP 0.17 Calculate the fault current at
Eample 3 Presence of transformer & motor Step 2: Calculate Equivalent impedances 1.0V 1.0V 0.0833 1.667 utility 2.4 Mpu 0.4354 Gpu Tpu1 0.48 7.89 Tpu2
Eample 3 Presence of transformer & motor Step 3: Calculate fault current 1.0V I V 1.0 pu pu Eq 0.4354 2.297 pu 0.4354 I I HV LV I Ipu 3 2898.55 2.297 3 IHV 34.5 13.8 9609 A 3844 A
Symmetrical ault SCC 1200 SCC 1200 SCC 1200 10/12.5 5 0.12 10/12.5 10/12.5 5 0.12 3 5% 2.4 M 2500 HP 0.17 I 7426 Amps I 9170 Amps I 9609 Amps