2p.y = 2a = 76 0.4+3.42 나 0.2 +0.85 Open circuit tests carried out on a 3.5 MVA, 4.16 kV, 60 Hz, three phase star connected synchronous generator gave the following results: EPM: Vpnt Ip.y (2p.u) ► If (A): 10 ▸ Ę₁ (KV): 15 3.5 4.16 5.7 20 25 30 6.25 7.95 =1+120° 6.2 +10.8 1+1 (0.87 176. 1 +0.87 £76.7 ➤ In the short circuit test a field current of 20A was needed to circulate full load current. The armature winding 1+0.2+10 resistance is 1.20 /phase, the field winding resistance is 500 and the rotational loss is 250kW. Determine the power angle, the voltage regulation and the efficiency when the generator delivers rated load at terminal voltage of 4.4 kV and at 0.8 power factor leading. ▸ Draw the power flow diagram for the generator and include all values of power flows. 1.2 + Jo E =14743

The synchronous reactance of a 200 MVA, 10kV, 3-phase, 50 Hz generator is 1.0 p.u. at its own base. Its p.u. reactance at 100 MVA, 20 kV base will be

The reactance of a generator is given as 0.25 per-unit based on the generator’s of 18 kV, 500 MVA. Find its per-unit reactance on a base of 20 kV, 100 MVA. a. 0.0505 b. 0.0605 c. 0.0405 d. 0.0606

A 13.2 kV, 60 Hz, 3-phase synchronous generator is connected in star and its neutral point is earthed while inductance per phase is 0.02 Henry. The generator is connected to a bus bar through a circuit breaker. The distributed capacitance up to circuit breaker between phase and neutral is 0.015 micro Farad. Determine the following: (i) Peak re-striking voltage (in kV) across the contact of circuit breaker; (ii) Frequency of oscillations (in kHz); (iii) Time to occurs first peak re-striking voltage (in micro second) and (iv) The average rate of rise of re-striking voltage (in mega volts per second)

Q A 50 Hz, 13.6kv, 3-phase arternator with grounded neutral hasinductance of 12 mH per phase and is connected to busbar 16]through a circuit breaker. The capacitance to earth between thealternator and the location of circuit breaker is o.03pF per phase.Neglect the resistance of the alternator. Determine the following:i) Maximum value of re-striking voltag. ."ro". the contactsof circuit breaker.i1) Frequency of transient oscillationsiii) Maximum value of RRRVir') Average RRRV upto the first peak of transientoscillations.

21) Two 3-phase 6.6kV, Star-connected alternators supply a load of 3000kW at 0.8pf lagging. The synchronous impedance per phase of machine A is (0.5 +j10)Q and machine B is (0.4+j12) Q. The excitation of machine A is adjusted so that it delivers 150A at a lagging pf and the governors are set so that the load is shared equally between the machines. Find the line to line voltage of alternator B.

High voltage engineering subject

(Qle, A three phase generator is operating at 1500rpm and has a no-load voltage of 7 kV. What would be the terminal voltage if a capacitive load is connected to its terminals? (a) 6.7 kV, (b) 6.9 kV, (c) 7 kV, (d) 7.2 kV

The amplitude of the sinusoidal symmetrical ac component of the three-phase short-circuit current of an unloaded synchronous machine decreases from a high initial value to a lower steady-state value, going periods through the stages of __________ and ________ periods.

(c) A star connected 3 phase wound field synchronous generator with a synchronous reactance of 202 is connected to a 6.6 kV (phase voltage) grid and supplies 1.5 MW at 0.95 lagging power factor at its terminals. Calculate the phase current and resultant voltage across the synchronous reactance (Vxs), and from a scaled phasor diagram graphically determine the required excitation voltage (En) and load angle (5).