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In a three phase power system line to line fault happened between phase a and c :
A) write the fault conditions in phase domain
b) derive the fault condition in sequence domaine. show all necessary steps. it must be noted that ABC positive phase sequence has to be used
C) draw the sequence networks.
The synchronous generator in Figure 7.3 is operating at rated MVA, 0.95 pf. lagging and at 5% above rated voltage when a bolted three-phase short cir- cuit occurs at bus 1. Calculate the per-unit values of (a) subtransient fault current; (b) subtransient generator and motor currents, neglecting prefault current; and (c) subtransient generator and motor currents including prefault current. FIGURE 7.3 2 Single-line diagram ofa (G synchronous generator feeding a synchronous 100 MVA 138 kVY/13.8 kV Δ X = 0.10 100 MVA 100 MVA 100 MVA 13.8 kV X"0.20 motor 13.8 kV 13.8 kV A/138 kVY X"0.15 X0.10
A balanced-Y load is in parallel with a balanced-D-connected capacitor bank.
The Y load has an impedance ZY ¼ ð3 þ j4Þ W per phase, and its neutral is
grounded through an inductive reactance Xn ¼ 2 W. The capacitor bank has
a reactance Xc ¼ 30 W per phase. Draw the sequence networks for this load
and calculate the load-sequence impedances.
Calculate the sequence components of the following balanced line-to- neutral voltages with abc sequence: (25p) 13= Van 1 LV (277/0° = 277/–120 277=120 volts
The synchronous generator in Figure 7.3 is operating at rated MVA, 0.95 p.f.
lagging and at 5% above rated voltage when a bolted three-phase short cir-
cuit occurs at bus 1. Calculate the per-unit values of (a) subtransient fault
current; (b) subtransient generator and motor currents, neglecting prefault current; and (c) subtransient generator and motor currents including prefault
current.
A 500-MVA 20-kV, 60-Hz synchronous generator with reactances Xá = 0.15, Xá = 0.24, Xd 1.1 per unit and time constants T'a = 0.035, T'a = 2.0, TA = 0.20s is connected to a circuit breaker. The generator is operating at 5% above rated voltage and at no-load when a bolted three-phase short circuit occurs on the load side of the breaker. The breaker interrupts the fault 3 cycles after fault inception. Determine (a) the sub-transient fault current in per-unit and kA rms; (b) maximum dc offset as a function of time; and (c) rms asymmetrical fault current, which the breaker interrupts, assuming maximum dc offset.
design a MOD 60 counter
A factory has an operating load of 40kw and a power factor of 0.45 lagging the factory is supplied from a 3 phase 400v supply
calculate the load current of the factory
calculate the KVAr of the factory at 0.45 power factor lagging
the factory operators are required to improve the power factor to 0.9 lagging calculate the KVAr of the capacitor for this operation
calculate the load current drawn by the factory after the power factor correction has been done
The ratings of the various components of a 3-bus system are listed below:
GENERATOR 1: 50 MVA, 13.8kV, X"= 0.15 p.u. ;
GENERATOR 2: 40 MVA, 13.2kV, X" = 0.20 p.u.
GENERATOR 3: 30 MVA, 11kV, X" = 0.25 p.u.
TRANSFORMER 1: 45 MVA, 11kV, Delta/110 kV Wye, X=0.1 p.u. ;
TRANSFORMER 2: 25 MVA, 12.5 kV, Delta /115 kV Wye, X = 0.15 p.u.
TRANSFORMER 3: 40 MVA, 12.5kV, Delta / 115 kV Wye, X = 0.1p.u.
The line impedances are shown in the figure. Draw the reactance diagram based on 50 MVA and 13.8 kV as base quantities in Generator 1. Note: Show a complete solution.
Using the supermesh approach, find the current through each element of the
network below.
