This book on "Power Systems Conceptualization with MATLAB” deals with the MATLAB exposure in power system for postgraduate as well as undergraduate students of Electrical Engineering. Electric Power System is the most important subject in electrical engineering and the most complex subject ever studied by the students. This book covers all the prominent topics like per unit systems, unsymmetrical fault calculations, fuse/relay/circuit breakers etc., and the more advanced topic like symmetrical components and arcing phenomena in power systems. The book covers a very wide spectrum of electrical power system studies which is normally not available in one single book. The book is so comprehensibly written that MATLAB programme on power systems are ready to use with the data of various standard distribution test systems.

Introduction Electrical Engineering generally uses a consistent, structured approach to the solving of various practical problems. An acceptable problem-solving approach and method can be defined, although variations can be seen in specific problems. Problems need to be approached methodically, applying an algorithm by which engineer arrives at an acceptable solution. Problem-Solving Process in Engineering: (i) Define the engineering problem (ii) Create a mathematical model (iii) Develop a computational method for solving the problem (iv) Implement the computational method (v) Test and assess the solution.

Short Transmission Line A short transmission line is defined as a transmission line with an effective length less than 80 km (50 miles), or with a voltage less than 69 kV. Unlike medium transmission lines and long transmission lines, the line charging current is negligible, and hence the shunt capacitance can be ignored. For short length, the shunt capacitance of this type of line is neglected and other parameters like electrical resistance and inductor of these short lines are lumped, hence the equivalent circuit is represented as given below. Let’s draw the vector diagram for this equivalent circuit, taking receiving end current Ir as reference. The sending end and receiving end voltages make angle with that reference receiving end current, of φs and φr , respectively.  

Introduction For the analysis of electrical power system, different values are required, thus, per unit system provides the value for voltage, current, power, impendence, and admittance. The Per Unit System also makes the calculation easier as all the values are taken in the same unit. The per-unit system is mainly used in the circuit where variation in voltage occurs. The per-unit value of any quantity is defined as the ratio of actual value in any unit to the base or reference value in the same unit. Any quantity is converted into per unit quantity by dividing the numeral value by the chosen base value of the same dimension. The per-unit value is dimensionless.

Introduction The Over-head insulator for overhead lines provides insulation to the electrical conductor. It is connected to the cross arm of the supporting structure and the electrical conductor passes through the clamp (insulator). It is mainly made of either glazed porcelain (Silica 20% + Feldspar 30% + Clay 50%) or toughened glass. The porcelain must be free from any defect. It should be vitrified because the presence of pore or air will lower down its dielectric strength. Any captured air impurity will also reduce the dielectric strength of the porcelain. Therefore, it is highly desirable that the insulators should be air free and resistant to the entrance of liquids/gases. It is desirable not to allow porcelain to come in direct contact with a hard metal screw thread. Therefore, cement is used between metal and the porcelain.

Introduction Dr. C.L. Fortescue presented a paper in 1918 in which he proved that a system of several vectors or quantities may be resolved into equal different symmetrical groups or systems. The method of symmetrical components is a general one applicable to any poly-phase system. Because of the widespread use of 3-phase systems and the greater familiarity which electrical engineers have with them, symmetrical component equations will be developed for three phases. The useful expression showing relationship between unsymmetrical and symmetrical component:

Introduction Dr. C.L. Fortescue presented a paper in 1918 in which he proved that a system of several vectors or quantities may be resolved into equal different symmetrical groups or systems. The method of symmetrical components is a general one applicable to any polyphase system. Because of the widespread use of 3-phase systems and the greater familiarity which electrical engineers have with them, symmetrical component equations will be developed for three phases. In the Analysis of Unsymmetrical Faults, the following assumptions will be made: 1. The generated emf system is of positive sequence only. 2. No current flows in the network other than due to fault i.e. load currents are neglected. 3. The impedance of the fault is zero. 4. Phase R shall be taken as the reference phase.

Introduction A generator is subjected to electrical stresses imposed on the insulation of the machine, mechanical forces acting on the various parts of the machine, and temperature rise. These are the main factors which make protection necessary for the generator or alternator. Even when properly used, a machine in its perfect running condition does not only maintain its specified rated performance for many years, but it does also repeatedly withstand certain excess of overload. Preventive measures must be taken against overloads and abnormal conditions of the machine so that it can serve safely. Even ensuring an efficient design, construction, operation, and preventive means of protection – the risk of a fault cannot be completely eliminated from any machine. The devices used in generator protection, ensure that when a fault arises, it is eliminated as quickly as possible.

Introduction The insulating material (may be fluid or air) used in circuit breaker should serve two important functions. They are written as follows: 1. It should provide sufficient insulation between the contacts when circuit breaker opens. 2. It should extinguish the arc occurring between the contacts when circuit breaker opens. The second point needs more explanation. To understand this point let us consider a situation if there is some fault or short circuit in the system, the relay provides desired signals to the circuit breaker so as to prevent system from ongoing fault. Now when circuit breaker opens its contacts, due to this an arc is drawn. The arc is interrupted by suitable insulator and technique. Methods of Arc Interruption

Introduction In normal working condition of electrical network, the current flows through the network is within the rated limit. If a fault occurs in the network mainly phase to phase short circuit fault or phase to ground fault, the network current crosses the rated limits. This high current may have a very high thermal effect which will cause permanent damage to the valuable pieces of equipment connected to the electrical network. So this high fault current should be interrupted as fast as possible. This is what an electrical fuse does. A fuse is a part of the circuit which consists of a conductor which melts easily and breaks the connection when current exceeds the predetermined value. An electrical fuse is the weakest part of an electrical circuit which breaks when more than predetermined current flows through it.

Inroduction The process of connecting neutral point of 3-phase system to earth (i.e. soil) either directly or through some circuit element is called neutral grounding. Neutral grounding provides protection to personal and equipment. It is because during earth fault, the current path is completed through the earthed neutral and the protective devices (e.g. a fuse etc.) operate to isolate the faulty conductor from the rest of the system. This point is illustrated in Figure 10.1. Figure 10.1 shows a 3-phase, star-connected system with neutral earthed. Suppose a single line to ground fault occurs in line R at point F. This will cause the current to flow through ground path as shown in Figure1. Note that current f lows from R phase to earth, then to neutral point N and back to R-phase. Since the impedance of the current path is low, a large current flow through this path. This large current will blow the fuse in R-phase and isolate the faulty line R. This will protect the system from the harmful effects of the fault. One important feature of grounded neutral is that the potential difference between the live conductor and ground will not exceed the phase voltage of the system i.e., it will remain nearly constant.

Solar Photovoltaic A single solar cell cannot provide required useful output. Therefore, to increase output power level of a PV system, it is required to connect number of such PV solar cells. A solar module is normally series connected sufficient number of solar cells to provide required standard output voltage and power. One solar module can be rated from 3 watts to 300 watts. The solar modules or PV modules are commercially available basic building block of a solar electric power generation system. Actually, a single solar PV cell generates very tiny amount that is around 0.1 watt to 2 watts. But it is not practical to use such low power unit as building block of a system. So required number of such cells are combined together to form a practical commercially available solar unit which is known as solar module or PV module.

Experiment No.-1 Aim: Study the characteristics between voltage and time of over voltage relay. There are several instruments in power system which may be exposed to over voltage like motor, transformer, capacitor etc. To protect instruments from over voltage, relay is necessary. The several type of over voltage relay is studying here. It is electromechanical type and very rigid in use. Its failure is almost negligible. Here the relay has an operating coil which core developed a rotating flush in disk due to this disk rotates at certain voltage. Before the certain voltage a vehicle spring makes force in opposite directions. So, the disk is not is the condition to rotate. A socket is given to different setting of tripping voltage. Time setting multiplier is given to setting direction so the disk is not in the condition to rotate.