EFFICIENCY

Efficiency

The losses in a transformer are limited to the following:
1) Copper loss in the resistance of the windings which is variable with load current
2) Iron loss in the core made up of component hysteresis and eddy current losses which are usually considered to be constant.
3) Stray loss produced by stray flux producing eddy current losses in the conductors
4) Dielectric loss in the insulating material which is appreciable only in the particular case of high voltage transformers {Note that apart from line transformers we also have instrument transformers and welding transformers}
Efficiency = Output/Input
= Output/(Output + Losses)

For an approximate equivalent circuit, Efficiency PU = V(21)I(21)puCosθ/V(21)I(21)puCosθ + I2(21)puR + V2(1)pugpu

TRUST GOD ALWAYS

Learn to trust in God all the time. Let not your heart be troubled.

Earthing

This is a connection to the general mass of the earth. The following items should be earthed.
a) All metalwork of wiring systems.
b) Exposed metalwork of all apparatus
c) One part of the secondary winding, and the non-current carrying parts of the metalwork of any transformer.

Parts of an earting System
Earth-Continuity conductor, the consumer’s earthing terminal, the earthing lead, and the earth electrode or its equivalent.

Earth-Continuity conductor. This is the cable or conductor which the metalwork to be earthed is connnected and which itself is connected to the earthing lead by way of the consumer’s earthing terminal

This could be the metal sheating of cables, or special continuity wire enclosed in the cable sheath or metal conduit enclosing the cable. When the metal sheathing of cables or metal conduit is used as an earth continuity conductor, all joints should be soundly made and be protected where necessary against corrosion.

Earthing Lead

This is the final conductor by which connection is made betweeen the consumer’s earthing terminal and the earth electrode or equivalent.

Buried electrodes
1) One or more hard – drawn bare copper rods are driven vertically into the ground surrounding the building in as damp a position as possible. Extension lengths may be available to allow for further depth penetration. A bare copper conductor, plate or strip, laid in a shallow trench again in the most suitable position.
2) A bare copper conductor, plate or strip, laid in a shallow trench again in the most suitable position.

Bonding

Bonding usually confused with earthing. Bonding applies to the internal installation, and is in the form of a low resistance connection between any two points of the earthed system to prevent a difference of potential. It is an Effective way to prevent Earth Leakage current. It is an effective way to prevent Earth Leakage current from harming users of domestic appliances and installations who may come in contact with these appliances and facilities in the course of their use and daily activities. Consumer’s earth terminal must be properlybonded to the gas and water services as near as possible to the point of entry into the premisis. Before bonding is done, the earthing must be properly tested. Other metal objects or metal works which one may accidentally come in contact with should be properly bonded. Examples. bath and exposed metal pipes, radiators, sinks and tanks. In the absense of metal to metal joints, of negligible electrical resistance, where bonding is not posible, for some reason, the metals have to be segregated to prevent a potential difference between them.

Beloved

Beloved now are we the sons of God, and it doth not yet appear what we shall be: but we know that when He shall appear, we shall be like Him; for we shall see Him as He is. And every man that hath this hope in Him purifieth himself, even as He is pure. Whosoever abideth in Him sinneth noth: whosoever sinneth hath not seen Him, neither known Him. Little children, let no man decieve you: he that doeth righteousness is righteous, even as he is righteous. Whosoever is born of God doth not commit sin; for His seed remaineth in him: and He cannot sin, because he is born of God.
Hereby perceive we the love of God, because he laid down His life for us: and we ought to lay down our lives for the brethren. But whoso hath this world’s good, and seeth his brother have need, and shutted up his bowels of compassion from him how dwelleth the love of God in him? My little children, let us not love in word, neither in tongue; but in deed and in truth. And hereby we know that we are of the truth, and shall assure our hearts before Him. For if our hearts condemn us, God is greater than our heart , and knoweth all things. Beloved, if our heart condemn us not, then have we confidence to ward God. And whatsoever we ask, we receieve of Him, because we keep His commandments, and do those things that are pleasing in His sight. And this is His commandment, That we should beleve on the name of His Son Jesus Christ, and love one another, as He gave us commandment. And He that keepeth His commandments dwelleth in Him, and He in Him. And hereby we know that He abides in us , by the Spirit which He hath given us.

POWER AND TORQUE IN INDUCTION MOTORS (Losses and the Power-Flow Diagram)

Induction motors are singly excited machines. LOSSES AND THE POWER-FLOW DIAGRAM. An induction motor can be basically described as a rotating transformer. In a transformer, the input is the electrical input to the primary winding while the output is the electrical output at the secondary. In this case, the inpute is the electrical input to the (3 phase) three phase stator winding. The secondary rotor windings are short circuited hence there is no electrical output. Hence the output is mechanical. The relationship between the input Electrical Power and the output Mechanical Power of this motor is shown in the Power-Flow Diagram. The input Power to an induction motor P(in) is in the form of three-phase Electric Voltage and Current. LOSSES : The first losses are -:- I2R(Isquared R) losses in the stator windings. (the stator copper loss, P(scl)). Then -:- Core losses in the form of hysteresis and eddy currents in the stator, P(core) . The remaining Power at this stage is transferred to the rotor of the machine across the air gap b/w between the stator and the rotor. This is the air gap power P(AG). The air-gap Power P(AG) is the power transfered from the stator to the rotor of the Induction Machine having removed the losses at the stator ie. Copper (Cu) losses and core losses from the input Power. After this Power transfer, to the rotor, some more losses occur in the form of Copper losses in the rotor. (remember that the rotor windings are shortcircuited) . At this stage, the rest of the Power is converted to Mechanical Power. P(conv). There are Mechanical Losses which are accounted for. These are -:- Friction and Windage Losses, P(F&W) and Stray Losses P(misc). When all these Losses are subtracted, we have the Output Power left. ie. The Power Output of the Motor, P(out)

THE TONGUE

My brethren, be not many masters, knowing that we shall receive the greater condemnation. For in many things we offend all. If any man offend not in word, the same is a perfect man and able also to bridle the whole body. Who is a wise man and endued with knowledge among you ? Let him shew out of a good conversation his works with meekness of wisdom. The wisdom that is from above is first pure, then peaceable, gentle, and easy to be intreated, full of mercy and good fruits, without hypocrisy. And the fruit of righteousness is sown in peace of them that make peace. Do you think that the scripture saith in vain, The spirit that dwelleth in us lusteth to envy? But He giveth more grace. Wherefore he saith, God resisted the proud, but giveth grace unto the humble. Submit yourselves therefore to God. Resist the devil, and he will flee from you. Draw nigh to God, and He will draw nigh to you. Cleanse your hands, ye sinners, and purify your heart, ye double minded. Humble yourselves in the sight of the Lord, and He shall lift you up. In every nation he that feareth Him, and worketh righteousness is accepted with Him. For God so loved the world that he gave His only begotten Son that whosoever believeth in Him should not perish, but have everlasting life.

STABILITY STUDIES

Stability Studies is a study of the Electrical Power System with a view of determining if the System will retain Synchronism after a perturbation. There are three main studies in stability studies. These are TRANSIENT STABILITY STUDIES, DYNAMIC STABILITY STUDIES, AND STEADY STATE STABILITY STUDIES. As stated earlier on, Stability Studies is the ability of the Power system to return to normal operation after a disturbance. Transient Stability studies deals with the ability of the Power System to remain in synchronism following major disturbances such as transmission line faults, sudden load changes, loss of generating unit or Electrical Power System Transmission line switcing.

STABILITY STUDIES

Stability Studies is a study of the Electrical Power System with a view of determining if the System will retain Synchronism after a perturbation.

SLACK BUS

A bus is also called a busbar. This is where connections are made in the power system. There three main types of buses in the Power System. These are the Slack bus, the Voltage controled bus and the Load bus. The Slack bus is the reference bus. It is also called the Swing bus. It is fully specified and no calculation is required at this bus. How ever all the calculations in Load flow analysis are made with respect to the slack bus. The total complex power is also calculated at the slack bus.

Load duration curve

Load Duration Curve is a graphical illustration and representation of the load cosumption in a place of interest. The load duration helps you to establish the load consumption pattern in any given place. This load duration curve is important in Electrical Power System Planning. It is also used in determing load growth. It helps the Electrical Power planning Engineer to determine specify and select appropriate power plants for different identified loads with different load patterns and characteristics. Information from the load duration curve can be used for studies involving Unit Commitment and Economic Dispatch. The load duration curve usually represents the load in the Electrical Power System Network of interest for a period of 24hrs ie. one day. It is cyclic in nature. (ie. Repetative). Three main parts of the load duration curve can be identified. These are the base load region, the peak load region and the intermediate load region. Appropriate Electrical Power Plants with the correct specification and characteristics are used to supply these loads. It is important that the right plants are used to supply the right load. Load consideration is important in the economic consideration in the choice of electrical power plant type. Load duration curves are usualy studied or estimated. Load duration curves are usually divided into three parts . The base load is the load below which the demand never falls and is supplied 100% of the time. The peak load is usually seen about 15% of the time. The intermediate load represents the remaining load region. Peaking load stations are used only a fraction of the time so one desires to minimize their capital costs knowing that even if the fuel cost is high, it can be tolorated since the station will be used only occasionally. For this reason, fossil fueled plants that will burn oil or natural gas is recommended. Base loaded plants are usually loaded as heavilly as possible operating costs for these plants are quite important and should be minimized. Most new coal powered stations are base loaded plants. Intermediate loaded plants tend to find an appropriate medium between base loaded plants and peak loaded plants. Eg. BBASE LOADED ELECTRICAL POWER PLANTS(New coal Power.Station, Hydro, Nuclear Power Station) INTERMEDIATE LOADED ELECTRICAL POWER PLANTS(coal Power Station, Hydro Power. Station) PEAK LOADED ELECTRICAL POWER PLANTS(Gas Power.Station, Petroleum Power. Station, Hydro Power. Station)