Introduction to Electrical Systems Course Code: EE 111 Course Code: - PowerPoint PPT Presentation

Introduction to Electrical Systems Course Code: EE 111 Course Code: EE 111 Department: Electrical Engineering Department: Electrical Engineering Instructor Name: B G Fernandes Instructor Name: B.G. Fernandes E ‐ mail id: bgf@ee iitb ac in E ‐ mail id: bgf@ee.iitb.ac.in EE 111: Introduction to Electrical Systems Tue Oct 1/19 Prof. B.G.Fernandes Lecture 33 27, 2009

Sub ‐ Topics: • Operation when feeding a local load • Operation when connected to grid • Synchronization S h i ti • Grid failure EE 111: Introduction to Electrical Systems Tue Oct 2/19 Prof. B.G.Fernandes Lecture 33 27, 2009

Review • Cylindrical rotor → generally 2 pole construction • Cylindrical rotor → generally 2 pole construction ∵ air gap is uniform, ‘L’ is independent of rotor position • Salient pole → Air gap is minimum along field axis (d ‐ axis) and maximum along quadrature axis (q ‐ axis) ∴ X d > X q For Generator: For Generator: • Purely ‘L’ load demagnetizing in nature while purely ‘C’ l ‘C’ load is magnetizing in nature d i ti i i t • In phase component → distort the field → cross magneti ing → cross ‐ magnetizing EE 111: Introduction to Electrical Systems Tue Oct 3/19 Prof. B.G.Fernandes Lecture 33 27, 2009

Cylindrical rotor Salient pole rotor EE 111: Introduction to Electrical Systems Tue Oct 4/19 Prof. B.G.Fernandes Lecture 33 27, 2009

3V [ ] = δ − θ − θ i P E V cos( ) cos 0 Z Z S π → ≅ ∵ θ & |Z | |X | s s 2 2 3EV = o P sin δ X X s • Operation at δ 1 is stable & δ 2 is unstable ∠ F ‘ δ ’ is the angle between r Fs • At steady state, both fields are rotating at ‘ ω s ’ EE 111: Introduction to Electrical Systems Tue Oct 5/19 Prof. B.G.Fernandes Lecture 33 27, 2009

Generator feeding local load ∴ ∴ E & E & V V A Any change in I f would result in a change in h i I ld lt i h i o t ⇒ as the load changes, speed of the prime mover and ∴ ‘f’ of ‘V’ in stator would change mover and ∴ ‘f’ of ‘V’ in stator would change ⇒ rating of synchronous machine in MVA in MVA ⇒ only small portable DG feed the local load h l l l d ⇒ high power generators are connected to the grid ⇒ Grid is a network to which a large no. of generators are connected connected EE 111: Introduction to Electrical Systems Tue Oct 6/19 Prof. B.G.Fernandes Lecture 33 27, 2009

EE 111: Introduction to Electrical Systems Tue Oct 7/19 Prof. B.G.Fernandes Lecture 33 27, 2009

Southern grid In India, there are two grids In India, there are two grids Rest of India ⇒ Total installed capacity is approx. 1,40,000 MW ⇒ Total installed capacity is approx. 1,40,000 MW ⇒ assume that at Khopoli, engineer changes the excitation of the generator it ti f th t ⇒ Its E o would change ⇒ If V t changes, it would affect all the other generators ⇒ not practical ⇒ grid ‘V’ and ‘f’ are kept almost constant(50.5 < f < 49) EE 111: Introduction to Electrical Systems Tue Oct 8/19 Prof. B.G.Fernandes Lecture 33 27, 2009

⇒ behavior of synchronous generator connected to the grid is different from that of generator feeding local grid is different from that of generator feeding local load ⇒ grid is a network whose ‘f’ & ‘V’ are held constant & g they do not change for small disturbance ⇒ change of excitation of generator connected to grid will g g g not change the terminal ‘V’ ∵ power input is held constant, output also will not ∵ p p , p change EE 111: Introduction to Electrical Systems Tue Oct 9/19 Prof. B.G.Fernandes Lecture 33 27, 2009

Operation at variable excitation and constant load E V E V = 0 P sin δ at constant load, X s PX PX → → constant ∴ = t t s E sin δ i δ 0 V also, VIcos φ = P = constant also, VIcos φ P constant ∴ Icos φ = constant If excitation is varied, then E 0 and δ would change such that ‘E 0 sin δ ’ will remain constant EE 111: Introduction to Electrical Systems EE 111: Introduction to Electrical Systems Tue Oct 10/19 Prof. B.G.Fernandes Prof. B.G.Fernandes Lecture 33 27, 2009

How to connect to the grid: • Process is kno n as s nchroni ation • Process is known as synchronization Just prior to closing the switch, ⇒ ‘f’ & |V| should be ≅ same as that of grid ⇒ Phase sequence should be same ⇒ Phase sequence should be same EE 111: Introduction to Electrical Systems Tue Oct 11/19 Prof. B.G.Fernandes Lecture 33 27, 2009

What is meant by grid failure? Assume that due to some reason, one of the power Assume that due to some reason, one of the power station (2000 MW) is tripped ⇒ prior to tripping there was a steady state & P = P ⇒ prior to tripping there was a steady state & P m = P e ⇒ loss of generation = 2000 MW ⇒ load is not disconnected ⇒ load is not disconnected ⇒ this load is now being shared by other generators ⇒ generators start slowing down ∴ frequency falls Maharashtra state electricity Transco web http://www.mahatransco.in/load ‐ dispatch.shtm California iso web http://www.caiso.com/ EE 111: Introduction to Electrical Systems Tue Oct 12/19 Prof. B.G.Fernandes Lecture 33 27, 2009

EE 111: Introduction to Electrical Systems Tue Oct 13/19 Prof. B.G.Fernandes Lecture 33 27, 2009

EE 111: Introduction to Electrical Systems Tue Oct 14/19 Prof. B.G.Fernandes Lecture 33 27, 2009

EE 111: Introduction to Electrical Systems Tue Oct 15/19 Prof. B.G.Fernandes Lecture 33 27, 2009

EE 111: Introduction to Electrical Systems Tue Oct 16/19 Prof. B.G.Fernandes Lecture 33 27, 2009

EE 111: Introduction to Electrical Systems Tue Oct 17/19 Prof. B.G.Fernandes Lecture 33 27, 2009

EE 111: Introduction to Electrical Systems Tue Oct 18/19 Prof. B.G.Fernandes Lecture 33 27, 2009

C Courtesy: Tata Power t T t P EE 111: Introduction to Electrical Systems Tue Oct 19/19 Prof. B.G.Fernandes Lecture 33 27, 2009