#Variable declaration
I_setting = 150.0 #Current setting of IDMT(%)
t_mult = 0.5 #Time multiplier setting
ratio_CT = 500.0/5 #CT ratio
CT_sec = 5.0 #Secondary turn
I_f = 6000.0 #Fault current
#Calculation
I_sec_fault = I_f/ratio_CT #Secondary fault current(A)
PSM = I_sec_fault/(CT_sec*I_setting/100) #Plug setting multiplier
t = 3.15 #Time against this PSM(sec). From graph E7.1 in textbook page no 595
time_oper = t*t_mult #Operating time(sec)
#Result
print('Time of operation of the relay = %.3f sec' %time_oper)
#Variable declaration
ratio = 525.0/1 #CT ratio
CT_sec = 1.0 #Secondary turn
t_mult = 0.3 #Time multiplier setting
I_f = 5250.0 #Fault current(A)
#Calculation
I_sec_fault = I_f/ratio #Secondary fault current(A)
PSM = I_sec_fault/(1.25*CT_sec) #Plug setting multiplier
t = 3.15 #Time against this PSM(sec). From graph E7.1 in textbook page no 595
time_oper = t*t_mult #Operating time(sec)
#Result
print('Time of operation of the relay = %.3f sec' %time_oper)
#Variable declaration
MVA = 20.0 #Transformer MVA
overload = 30.0 #Overload of transformer(%)
kV = 11.0 #Bus bar rating(kV)
CT_trans = 1000.0/5 #Transformer CT
CT_cb = 400.0/5 #Circuit breaker CT
ps = 125.0 #Plug setting(%)
ts = 0.3 #Time setting
I_f = 5000.0 #Fault current(A)
t_margin = 0.5 #Discriminative time margin(sec)
#Calculation
I_sec_fault = I_f/CT_cb #Secondary fault current(A)
CT_cb_sec = 5.0 #Secondary turn
PSM = I_sec_fault/(ps/100*CT_cb_sec) #Plug setting multiplier
t = 2.8 #Time against this PSM(sec). From graph E7.1 in textbook page no 595
time_oper = t*ts #Operating time of feeder relay(sec)
I_ol = (1+(overload/100))*MVA*1000/(3**0.5*kV) #Overload current(A)
I_sec_T = I_ol/CT_trans #Secondary current(A)
CT_T_sec = 5.0 #Secondary turn of transformer
PSM_T = I_sec_T/CT_T_sec #Minimum plug setting multiplier of transformer
I_sec_T1 = I_f/CT_trans #Secondary fault current(A)
ps_T1 = 1.5 #Plug setting as per standard value
PSM_T1 = I_sec_T1/(CT_T_sec*ps) #Plug setting multiplier of transformer
t_T1 = 7.0 #Time against this PSM(sec). From graph E7.1 in textbook page no 595
time_setting = (time_oper+t_margin)/t_T1 #Time setting of transformer
#Result
print('Operating time of feeder relay = %.2f sec' %time_oper)
print('Minimum plug setting of transformer relay, P.S > %.2f ' %PSM_T)
print('Time setting of transformer = %.3f ' %time_setting)
#Variable declaration
I_f = 2000.0 #Fault current(A)
ratio_CT = 200.0/1 #CT ratio
R_1 = 100.0 #Relay 1 set on(%)
R_2 = 125.0 #Relay 2 set on(%)
t_margin = 0.5 #Discriminative time margin(sec)
TSM_1 = 0.2 #Time setting multiplier of relay 1
#Calculation
CT_sec = 200.0 #CT secondary
PSM_1 = I_f*100/(CT_sec*R_1) #PSM of relay 1
t_1 = 2.8 #Time against this PSM(sec). From graph E7.1 in textbook page no 595
time_oper_1 = TSM_1*t_1 #Operating time of relay with TSM of 0.2(Sec)
PSM_2 = I_f*100/(CT_sec*R_2) #PSM of relay 2
t_2 = 3.15 #Time against this PSM(sec). From graph E7.1 in textbook page no 595
actual_time_2 = time_oper_1+t_margin #Actual time of operation of relay 2(sec)
TSM_2 = actual_time_2/t_2 #Time setting multiplier of relay 2
#Result
print('Time of operation of relay 1 = %.2f sec' %time_oper_1)
print('Actual time of operation of relay 2 = %.2f sec' %actual_time_2)
print('T.S.M of relay 2 = %.4f' %TSM_2)
#Variable declaration
I_min = 0.1 #Relay minimum pick up current(A)
slope = 10.0 #Slope characteristic(%)
CT_ratio = 400.0/5 #CT ratio
I_1 = 320.0 #Current(A)
I_2 = 304.0 #Current(A)
#Calculation
I_op_coil = (I_1-I_2)/CT_ratio #Current in operating coil(A)
I_re_coil = 1.0*(I_1+I_2)/(2*CT_ratio) #Current in restraining coil(A)
I_re_coil_slope = I_re_coil*slope/100 #Current in restraining coil with slope(A)
#Result
if(I_op_coil<I_re_coil_slope):
print('Relay will not trip the circuit breaker')
else:
print('Relay will trip the circuit breaker')