Transmission Line Protection (21)

Transmission Line Protection
https://youtu.be/s_IrsNHv4aQ

new innovations in electrical

Power Flow Analysis: Transmission and Distribution Systems:

Power Flow Analysis: Transmission and Distribution Systems: 

Power flow or load flow is one of the important power system analyses. Problem. This problem is determining the unspecified (dependent) parameters of the power network by some specified (independent) parameters.

It is known that the power system consists of generators, loads, transformers, transmission lines and other protective devices. In power flow every bus (node) is having four parameters.

1. Real Power P

2. Reactive power Q

3. Voltage magnitude [V]

4. Voltage magnitude φ

Depending on the type of the bus two out the four variables are specified and the remaining two has to be determined. The specified two variables and unspecified two variables of each bus are related by the kirchoff’s network laws.

The network elements are modeled according to their steady state characteristics.

1. Generator –voltage source with series impedance

2. Loads: constant power or constant admittance (impedance)

3. Transmission line: pi model

4. Transformers are to be incorporated in the transmission line model.

The specified and unspecified parameters
Type of the bus	Specified variables	Unspecified variables
Slack	[V],φ	P,Q
Generator	[V],P	Q, φ
Load(Constant power)	P,Q	[V], φ

When the power is transmitted from the generators to the loads through the transmission line the loss occurring in the transmission line is unavoidable. It is call the transmission loss and it not known in advance so there must be a provision that a generator should include the transmission loss in its generation.

This is the reason why the slack bus concept is included in the power flow analysis. The generator having largest capacity is chosen as the slack bus. Depending on the selection of the slack bus generator the power flow solution will vary.

Procedure to solve transmission system power flow

The following steps are to be followed to carry out power flow analysis. Here it is assumed that the three phase network is a balanced one.

1. Collect the specified data of generators, loads, transmission lines, and transformers. You can follow some matrix format like matpower.
2. Convert the network as per unit equivalent.
3. Formulate the equations as per kirchooff’s law.

These equations can be written in either polar form or rectangular form. In polar form no of equation are to be solved in 2(n-1)-m, wherein the rectangular form the no of equations are 2(n-1).

1. The system of non linear (polar trigonometric, rectangular quadratic) equations are to be solved by numerical methods only because so far no analytical solution is derived to sole this problem.
2.   Newton Raphson method, Decupled and gauss seidal are methods used to solve this problem. Among this N-R and Decoupled are preferred for their quadratic convergence.

Distribution Power flow.

The distribution systems are characterized by their nature of high R/X ration and radial nature (no loop).The admittance matrix is sparse and the Newton Raphson method may fail to converge for some networks. So the modeling of the problem as well as the solution methodology is different.

 The power flow equations for a radial distribution system are derived as the relationship between the specified complex bus powers and the bus voltages. If the network has n (total number) buses and ‘m’ generator buses the power flow equations are written as follows

k(i) is the set of nodes connected to node i, and P_i /Q_i denote the real/reactive power at node i. The complex non linear equations (B2) are to be solved to determine the bus voltages. So many methods ranging form sweep methods to conic programming methods available in the literature 

 to solve this problem..

SGP BITS

1. Oil immersed type reactors are used for voltages __________.

2. A circuit breaker is essentially _________.

3. The arcing contacts for a circuit are made up of ______.

4. The fault clearing time of a circuit breaker is usually of ________.

5. For modern circuit breakers, the time of closing the cycle is _______.

6. The pressure of air used in air blast circuit breakers is around _____.

7. The rating of circuit breaker is usually determined on the basis of ____.

8. Busbars are usually made of _______.

9. A fuse is normally a ___________.

10. Buchholz relay is a ___________.

11. Mho relays have an R-X  plane characteristic depicted by __________.

12. Under voltage relays are mostly used for _______.

13. Differential relays are used for protection of equipment against _________.

14. Earth fault relays are _____________.

15. Reactance relay are employed for phase fault in ____________.

16. Location of lightning arrestor is near a ___________.

17. Grounding is done generally at _______.

18. A relay used on short transmission line is ___________.

19. In tap changing transformers, the tappings are provided on _______.

20. Which of the following is a static excitor?

21. Which of the following equipment is not installed in a substation?

22. The recovery voltage will be maximum for power factor of ____.

23. Arc chutes are used in _______________.

24. Breaking capacity of circuit breakers is usually expressed in ___________.               
25. Earth wire is made of ______.

26. A Buchholz relay protect a transformer from__________

27. In Mertz –Price protection, the CT’s  secondary of delta – star power transformer will be in______________

28. For transformer protection, a differential relay is biased to avoid mal operation due to_____________

29.The percentage bias for a generator protection lies between____

30.For the protection of transformers, harmonic restraint is used to guard against_________________

31.The bus-bar zone faults are generally__________

32.A line trap in a long transmission line is used to _________

33.First zone distance relay protects a transmission line section up to   full length.___________

34.The over voltage surges in the power systems may be caused by___________

35.Location of lightning arrestors is near a___________

36.The reflection coefficient of a short circuited line is ___________

37.In railway applications  Circuit Breakers is used__________

38.Arc is initiated due to___________

39.Current zero interruption method used in________

40.Minimum oil circuit breakers use oil for_____________

41.Making capacity of a circuit breaker is equal to_____________

42.Arc in a circuit behaves as a____________

43.Differential relays are used for protection of___________

44.The relay used on short transmission lines____________

45.Both voltage and current signals are required for____________

46.Differential relays used for the protection of equipment against________

47.Auto reclosure improves  what type of stability.___________

48.what is the power factor of an arc?_________

49.Peterson coil has a reactance called?__________

50.what is the rating of SF6?___________

 KEY

1. above 33kv                                                                     

2. arc extinguisher                                                                   

3. copper tungsten alloy                                                    

4. few cycles of supply voltage                                          

5. 0.003 sec                                                                        

6. 20kg/cm2                                                                                                                         

7. symmetrical faults

8.copper

9current limiting devices

10. gas actuated relay

11.a circle passing through origin

12 motor protection

13. internal faults

14. directional relay

15. short lines

16  transformer

17 supply end

18 reactance relay

19 secondary winding

20 rectifier

21. exiters

22  unity

23 air blast CB

24 MVA

25 galvanised standered steel

26 internal faults

27 star – delta

28 inrush currents

29 5-10

30 swithing over voltages

31 single line to ground

32  confined the carrier signals in the line

33  80%

34 switching

35 transformer

36 -1

37 air blast

38 current between contacts

39 AC circuit breakers

40 arc quenching

41 2.55 times of symmetrical breaking capacity

42 resistance increases voltage increases

43 transformers

44 reactance relay

45 directional relay

46 internal faults
47 transient

48 unity

49 inductance

50. above 132kv

working of relay

https://www.facebook.com/ElectricalTechnology.org/

hi to all