In a 230 kV system, the line to ground capacitance is .03 μF and inductance is 12 mH. If an instantaneous magnetizing current of 8A is interrupted find the output voltage appearing across the pole of a C.B.
For an overcurrent relay with plug setting multiplier of 5 and time multiplier setting of 2, the operating time of relay is 5 sec. The operating time when plug setting multiplier is not changed and time multiplier setting is made 0.5 is _____ (in sec)
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A 50 Hz, 20 kV generator is connected to a power system. The system reactance and capacitance per phase are: 5 mH and 0.6 mF respectively. What is the maximum voltage across the contacts of the circuit breaker at an instant when it passes through zero
A 10-ampere, over current relay having a current setting of 150% and a time setting multiplier of a 0.8 connected to supply circuit through a 400/5 current transformer when the circuit carries a fault current of 5000 A. Find the plug-setting multiplier.
A connection of a percentage differential relay is shown in the figure. A high resistance fault occurs near the neutral end with the current distribution the relay has 10% i.e Nr/No = 0.1 and pick up of 0.15 A the CT ratio is 500/5. Find the relay current.
A star connected 3 phase, 12 MVA, 8 KV alternator is protected by Merz-Price circulating current principle using 1000/5 amperes current transformers. The start point of the alternator is earthed through a resistance of 10 Ω. If the minimum operating current for the relay is 1 A. Calculate the percentage of each phase of the stator winding which is unprotected against earth-faults when the machine is operating at normal voltage.
A 50 Hz, 13 kV three phase alternator with earthed neutral has a reactance of 8 ohms per phase and is connected to a bus bar through a circuit breaker. The distributed capacitance upto circuit breaker between phase and neutral is 0.02 μF. The average rate of rise of re-striking voltage up to first peak is (in kv/μsec)
Consider a Δ/Y connected, 20 MVA, 33/11 -kV transformer with differential protection applied for the current transformer ratios shown in figure find the minimum relay current setting to allow 125 percent overload
A 150 MVA, 22 kV synchronous generator having a reactance of = 0.2 pu,xd = 1.1pu is connected to a transformer through a 5-cycle circuit breaker.
The generator is at no load and rated voltage when a three-phase short circuit fault occurs between the breaker and transformer. The ratio of momentary current to sustained short circuit current of breaker is -
A – 3 phase transformer rated for is connected star/delta and the protecting current transformer on the low voltage side has a ratio of 500/5. Determine the ratio of the current transformer on the HV side.