A substation receives 6000 kva at 6 kv 08 pf lagging on low...

A substation receives 6000 kVA at 6 kV, 0.8 p.f. lagging on the low voltage side of a transformer from a generating station through a 3-phase cable system having a resistance of 7 Ω and reactance of 2 Ω per phase. Identical 6600/33000 V transformers are installed at each end, with the 6600 V side being delta connected and the 33000 V side star connected. The resistance and reactance of each transformer are 1 Ω and 9 Ω respectively, referred to the high voltage side. Calculate the voltage at the generating station bus bars.

Transcript

00:01 Let's discuss this question.

00:02 So our substation receives 6 ,000 kilowalt ampere at 6 kilowat 0 .8 pf lagging on the low voltage side of the transformer from the generating station.

00:14 Through the three -phase cable system having a resistance of 7 oms and reactants of 2 oms per phase.

00:20 So here we need to calculate the voltage at the generating station bus bars.

00:24 So for example, if this is the diagram here, so i will get a very much.

00:47 Give us 0 .8 pf lag and here substation is 6 volt that is vs this is 6kvae and this is 3300 per 6600 volt this is y minus delta and this is 6 ,000 kva so 6600kva so 6600 per 333 0 0 volt delta minus y so here we can say the single line diagram of the system is given so since both the transformers are delta connected in lv side and y connected in hv side so here we can say phase transformation ratio will be equal to 33000 divided by under root 3 divided by 6600 so this will be equal to 2 .887 so this is the phase transformation ratio therefore we can say that substation voltage referred to hva site of substation and transformer.

03:14 So here we can say v -s is equal to 6 multiplied by 2 .887 kilo -volt.

03:22 This is per phase.

03:26 So this will be v -s will be equal to 17 .322 kilowolt and this is also phase.

03:34 So finally here we can say that i is equal to 6 ,000 divided by 3 multiplied by 6 and here i is equal to 33 .33 mpia.

03:48 So this is the current.

03:53 So here we can say therefore phase current referred to hv side of the substation and transformer so i dash is equal to 33 .33 divided by 2 .887 and here we can say i dash is equal to 115 .46 ampere so this is the value of i dash now further we can say also it is given that each transformer impedance referred to to hb side this will be equal to 1 plus j 9 oms per phase so here we can say transmission cable impedance will be equal to 7 plus j 2 oms for phase therefore the single line impedance dense diagram says that, let's draw the diagram.

06:01 So this is the diagram again.

06:12 This is i -dash.

06:14 So here we can say this is v -s -s...

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