Journey of electrical network

how to wire electrical panel

Electrical Switch gear

Electrical switch gear is on of the important part of electrical system. the purpose is to provide switching function, control function and protection of the system. Usual switch gear elements are- circuit breaker, relay, magnetic contactor, solenoid, instrument transformer- current transformer, voltage transformer etc.

1. Circuit Breaker
2. Relay
3. Magnetic devices
4. Instrument transformer

1. Circuit Breaker

1. Function and rated characteristics of circuit breaker – all things need to know of circuit breaker (1 of 3)
2. Rated frequency, operating sequence, short-circuit & out-of-phase breaking current characteristics of circuit breaker. (Part 2 of 3)
3. How to select Fuse or Circuit Breaker for group of motor in same branch circuit as per National Electric Code.
4. Arc Fault Circuit Interrupter (AFCI)- circuit breaker that prevents electrical fire causing arcing.
5. RCB – Residual circuit breaker to detect earth fault ; how it works.
6. Ground or Earth fault protection Relay- RCB, RCD

2. Relay

1. 1.Basic of Relay – definition, configuration and symbols.
2. 2.Relay accessories devices
3. Types of Relay based on working principle.
4. A brief insight on directional relay- its function, theory and use.
5. A brief insight on relay auxiliary switch or contacts.
6. Over Current Relays
7. Ground or Earth fault protection Relay- RCB, RCD
8. Time delay relay – types and categories.
9. Purpose & details on Trip circuit Supervision Relay -TSR.
10. How to obtain variety of operation with auxiliary relay by adding accessories.
11. Electrical Ladder diagram- definition and details.
12. How to implement control logic gate with relay.
13. Pick and place robot control with timer relay.

03. Magnetic devices

1. Magnetic Contactor- construction & how it works.
2. Solenoid types, parameters and practical application area.
3. Solenoid application area and its limitation.
4. Solenoid basic working principle and a practical Solenoid valve.
5. What is AC-hum & Contact bounce in Magnetic Contactor.
6. How to do maintenance of contacts in Magnetic Contactor.

4. Instrument transformer

1. Instrument transformer installation and maintenance- complete list of precaution and instructions.
2. Instrument transformer – application and types.
   Current transformers, Voltage transformers in brief, Function of Instrument transformers.

Current Transformer

1. Non-magnetic current transformer with Rogowski coil & its advantages.
2. Current transformer- definition, basic function, composition, types & rating.
3. CT burden, Knee point voltage & Magnitization curve- details of Current transformer.
4. Basic connections of current transformer to a circuit

Voltage or potential transformer (PT/VT)

1. Basic of voltage/Potential transformer. Definition, function of VT/ PT | Why secondary of VT/PT must not be shorted | Composition of VT /PT | Types of VT/PT.
2. Connection of Voltage / Potential transformer. Basic connection of VT/PT | Metering connection arrangements for VT/PT | Measure residual voltage with PT/VT | Internal connection of PT / VT.
3. Why a voltage transformer should not be connected in short circuit – explained by equations.

How dry type transformers are self-extinguishing and fire resistant.

Dry type transformers are self-extinguishing and fire resistant as construction materials used in the dry type transformer are aluminum, silica (quartz sand), epoxy resins which are very much flame-retardant and self-extinguishing materials.

What is meant by self-extinguishing

Self extinguishing means

• Prevent the development of fire
• Interrupt or slow down combustion processes by removing any of the fire continuing factors such as -heat, oxygen, fuel, exo-thermic action.

In dry type transformer if the cause of fire is removed then the fire will be ceased by itself by continuously consuming the energy of fire. This is done by the construction materials of dry type transformer which are self-extinguishing and fire resistant it self. These materials are aluminum, silica (quartz sand), epoxy resins etc.

Aluminum, self-extinguishing and fire resistant

1. Low melting point of Aluminum
Melting point of Aluminum alloys are between 600 and 660 degrees Celsius. This is why when aluminum is exposed to fire environment it will begin to melt (not burn). Also as temperature passes the melting point it will not increase until the whole melt down is completed.

2. Higher Heat conductivity of Aluminum
Heat conductivity of Aluminum is almost four times greater than that of iron. Specific heat capacity of Aluminum is similar to iron. Reflectivity to thermal radiation of fire is 80 to 90% for aluminum and for iron it is 5 to 25%.

3. High heat dissipation rate of Aluminum
With the exposure to fire, aluminum will dissipate large amount of heat quickly and at the same time it will absorb huge amount of thermal energy from the fire. These actions are self-extinguishing in nature.

Resin,fire resistant

The resin has fire resistance property with the following nature-

• High resistance to ignition of fire.
• Reduced smoke and fume emission.
• Reduced the rate of flame speed.
• Reduced the heat release.

Inspection & diagnostics of transformer

Periodic inspection & diagnostics of transformer- Ensuring a long life for your transformer.

Transformer is a static device, thus it requires less attention but with proper Periodic inspection & diagnostics of transformer it would be possible to avoid the unwanted break down & frequent interval of schedule maintenance.

As transformer is the heart of power network, the maximum availability of it and also to meet the full life time of transformer is a matter to think of.

Main parameter for defining transformer health

The four main parameters that are defining the transformer health and thus highly important for transformer inspection & diagnostics are

• Paper used for conductor insulation.
• pressboard used for the major insulation
• winding support
• Transformer oil

Among these, transformer oil is the highly important. Modern transformer design are such that by just inspecting the status of transformer oil, the health of the transformer can be easily defined.

Regular parameter reading of transformer is important

The regular data reading of different parameters is very important for maintenance of transformer. The deviation in regular readings is effective to point out a likelihood of a fault or a fault that is slowly forming.

Basic checklist for a transformer

• Temperature (oil temperature of conservator tank, OLTC tank, radiator etc.)
• Hot point.
• Oil leak.
• Oil level (LTC, Transformer tank, bushings, radiator etc.)
• Supporting system-Silica gel, cooling fan, control heater, door gaskets conditions.
• Load tap changer – noise & misalignment in operation, amount of LTC in different position.
• Any loose or displaced parts- such as loose earth connection, loose base etc.
• Crack in structure.
• Sign of burning.

Parameters for periodic inspection & diagnostics of transformer

01. Temperature (Oil, Hot point) in transformer

As per ANSI (American National Standards Institute), the maximum temperature permitted for oil is of 90°C and the maximum temperature of the hottest point is 110°C.

02. Oil level in transformer

Oil level in a transformer conservator tank and that of the OLTC or radiator has no specific rules. The requirement is to maintain the oil presence in the oil tanks. Standard oil level is maintained in consideration of oil low level in low temperature and high level in high temperature or in loading condition. The requirement is to maintain oil in the oil tank by avoiding empty tank in low temperature and over flow of oil in loading or high temperature.

03. Silica gel color & oil cup in transformer

The function of silica gel is to absorb moisture from the air to maintain the transformer safe from the demerits of moisture. Color of the silica gel is changed when it becomes saturated that is it can not absorb moisture any more. There is confusion about color changing. Some silica gel changes to black or red or become white when they become saturated. So saturated silica gel color can be confirmed from the manufacture recommendation.

04. Oil leaks in transformer

Oil leak is basically due to deterioration of some gaskets or they are in wrong position.

05. Noise in transformer

Noise is an important parameter. Some fault can be readily identified with comparison of regular noise and abnormal noise of transformer.

Basic concept of Demi water used in industrial application and equipment

Water without minerals such as, salt etc. called de-mineralized water or demi water or de-ionized water. With low mineral content, demi water has some changed expected properties such low conductivity, low corrosive effects etc. Demi water has some specific uses in industrial applications such as, boiler, pipeline etc.

Why demi water is used:

Regular water with mineral contents has some corrosive effects to metals or conductivity issues for certain applications. Additionally, minerals deposits or residues might settle in the metal surface, which in time become hard. This is called Scaling effects.

steam turbine run by steam of demi water.

Demi water is used extensively for all mos all of the industrial applications in which there are water use provisions. Without demi water, the expensive parts of would be of shorten life time with simple water.

Quality of Demi water:

Demi water quality and specification varies as per the use. Usually the manufacturer of the equipment dictates specification of the demi water in which it is going to be used. Even the equipment manufacturer itself provides some time provided the demi water system.
There is a international standard- American Society for Testing and Materials (ASTM) D1193-91, Standard specification for Reagent Grade Water

How demi water is prepared:

ion exchanger resin beads used for demi water preparation

Demi water is prepared through ion exchange resin. These are special types of insoluble matrix (or support structure) normally in the form of small (0.5-1 mm diameter) beads, fabricated from an organic polymer substrate.
What ion exchange polymer does is just trap certain ions in exchange of releasing of other ions. In case of basic demi water preparation, ion exchange resin releases hydrogen, hydroxide, and traps minerals ions. For specific application and usages, the ion exchange process may vary with 

GATE EXAM SYLLABUS

GATE EXAM SYLLABUS

Electrical Engineering - EE

ENGINEERING MATHEMATICS

Linear Algebra: Matrix Algebra, Systems of linear equations, Eigen values and eigen vectors.

Calculus: Mean value theorems, Theorems of integral calculus, Evaluation of definite and improper integrals, Partial Derivatives, Maxima and minima, Multiple integrals, Fourier series. Vector identities, Directional derivatives, Line, Surface and Volume integrals, Stokes, Gauss and Greens theorems.

Differential equations: First order equation (linear and nonlinear), Higher order linear differential equations with constant coefficients, Method of variation of parameters, Cauchys and Eulers equations, Initial and boundary value problems, Partial Differential Equations and variable separable method.

Complex variables: Analytic functions, Cauchys integral theorem and integral formula, Taylors and Laurent series, Residue theorem, solution integrals.

Probability and Statistics: Sampling theorems, Conditional probability, Mean, median, mode and standard deviation, Random variables, Discrete and continuous distributions, Poisson, Normal and Binomial distribution, Correlation and regression analysis.

Numerical Methods: Solutions of non-linear algebraic equations, single and multi-step methods for differential equations.

Transform Theory: Fourier transform, Laplace transform, Z-transform.

ELECTRICAL ENGINEERING

Electric Circuits and Fields: Network graph, KCL, KVL, node and mesh analysis, transient response of dc and ac networks; sinusoidal steady-state analysis, resonance, basic filter concepts; ideal current and voltage sources, Thevenins, Nortons and Superposition and Maximum Power Transfer theorems, two-port networks, three phase circuits; Gauss Theorem, electric field and potential due to point, line, plane and spherical charge distributions; Amperes and Biot-Savarts laws; inductance; dielectrics; capacitance.

Signals and Systems: Representation of continuous and discrete-time signals; shifting and scaling operations; linear, time-invariant and causal systems; Fourier series representation of continuous periodic signals; sampling theorem; Fourier, Laplace and Z transforms.

Electrical Machines: Single phase transformer - equivalent circuit, phasor diagram, tests, regulation and efficiency; three phase transformers - connections, parallel operation; auto-transformer; energy conversion principles; DC machines - types, windings, generator characteristics, armature reaction and commutation, starting and speed control of motors; three phase induction motors - principles, types, performance characteristics, starting and speed control; single phase induction motors; synchronous machines - performance, regulation and parallel operation of generators, motor starting, characteristics and applications; servo and stepper motors.

Power Systems: Basic power generation concepts; transmission line models and performance; cable performance, insulation; corona and radio interference; distribution systems; per-unit quantities; bus impedance and admittance matrices; load flow; voltage control; power factor correction; economic operation; symmetrical components; fault analysis; principles of over-current, differential and distance protection; solid state relays and digital protection; circuit breakers; system stability concepts, swing curves and equal area criterion; HVDC transmission and FACTS concepts.

Control Systems: Principles of feedback; transfer function; block diagrams; steady-state errors; Routh and Niquist techniques; Bode plots; root loci; lag, lead and lead-lag compensation; state space model; state transition matrix, controllability and observability.

Electrical and Electronic Measurements: Bridges and potentiometers; PMMC, moving iron, dynamometer and induction type instruments; measurement of voltage, current, power, energy and power factor; instrument transformers; digital voltmeters and multimeters; phase, time and frequency measurement; Q-meters; oscilloscopes; potentiometric recorders; error analysis.

Analog and Digital Electronics: Characteristics of diodes, BJT, FET; amplifiers - biasing, equivalent circuit and frequency response; oscillators and feedback amplifiers; operational amplifiers - characteristics and applications; simple active filters; VCOs and timers; combinational and sequential logic circuits; multiplexer; Schmitt trigger; multi-vibrators; sample and hold circuits; A/D and D/A converters; 8-bit microprocessor basics, architecture, programming and interfacing.

Power Electronics and Drives:Semiconductor power diodes, transistors, thyristors, triacs, GTOs, MOSFETs and IGBTs - static characteristics and principles of operation; triggering circuits; phase control rectifiers; bridge converters - fully controlled and half controlled; principles of choppers and inverters; basis concepts of adjustable speed dc and ac drives.

Electronics and Communication Engineering - EC

ENGINEERING MATHEMATICS

Linear Algebra: Matrix Algebra, Systems of linear equations, Eigen values and eigen vectors.

Calculus: Mean value theorems, Theorems of integral calculus, Evaluation of definite and improper integrals, Partial Derivatives, Maxima and minima, Multiple integrals, Fourier series. Vector identities, Directional derivatives, Line, Surface and Volume integrals, Stokes, Gauss and Greens theorems.

Differential equations: First order equation (linear and nonlinear), Higher order linear differential equations with constant coefficients, Method of variation of parameters, Cauchys and Eulers equations, Initial and boundary value problems, Partial Differential Equations and variable separable method.

Complex variables: Analytic functions, Cauchys integral theorem and integral formula, Taylors and Laurent series, Residue theorem, solution integrals.

Probability and Statistics: Sampling theorems, Conditional probability, Mean, median, mode and standard deviation, Random variables, Discrete and continuous distributions, Poisson, Normal and Binomial distribution, Correlation and regression analysis.

. Numerical Methods: Solutions of non-linear algebraic equations, single and multi-step methods for differential equations.

Transform Theory: Fourier transform, Laplace transform, Z-transform.

ELECTRONICS AND COMMUNICATION ENGINEERING

Networks: Network graphs: matrices associated with graphs; incidence, fundamental cut set and fundamental circuit matrices. Solution methods: nodal and mesh analysis. Network theorems: superposition, Thevenin and Nortons maximum power transfer, Wye-Delta transformation. Steady state sinusoidal analysis using phasors. Linear constant coefficient differential equations; time domain analysis of simple RLC circuits, Solution of network equations using Laplace transform: frequency domain analysis of RLC circuits. 2-port network parameters: driving point and transfer functions. State equations for networks.

Electronic Devices: Energy bands in silicon, intrinsic and extrinsic silicon. Carrier transport in silicon: diffusion current, drift current, mobility, and resistivity. Generation and recombination of carriers. p-n junction diode, Zener diode, tunnel diode, BJT, JFET, MOS capacitor, MOSFET, LED, p-I-n and avalanche photo diode, Basics of LASERs. Device technology: integrated circuits fabrication process, oxidation, diffusion, ion implantation, photolithography, n-tub, p-tub and twin-tub CMOS process.

Analog Circuits: Small Signal Equivalent circuits of diodes, BJTs, MOSFETs and analog CMOS. Simple diode circuits, clipping, clamping, rectifier. Biasing and bias stability of transistor and FET amplifiers. Amplifiers: single-and multi-stage, differential and operational, feedback, and power. Frequency response of amplifiers. Simple op-amp circuits. Filters. Sinusoidal oscillators; criterion for oscillation; single-transistor and op-amp configurations. Function generators and wave-shaping circuits, 555 Timers. Power supplies.

Digital circuits: Boolean algebra, minimization of Boolean functions; logic gates; digital IC families (DTL, TTL, ECL, MOS, CMOS). Combinatorial circuits: arithmetic circuits, code converters, multiplexers, decoders, PROMs and PLAs. Sequential circuits: latches and flip-flops, counters and shift-registers. Sample and hold circuits, ADCs, DACs. Semiconductor memories. Microprocessor(8085): architecture, programming, memory and I/O interfacing.

Signals and Systems: Definitions and properties of Laplace transform, continuous-time and discrete-time Fourier series, continuous-time and discrete-time Fourier Transform, DFT and FFT, z-transform. Sampling theorem. Linear Time-Invariant (LTI) Systems: definitions and properties; causality, stability, impulse response, convolution, poles and zeros, parallel and cascade structure, frequency response, group delay, phase delay. Signal transmission through LTI systems.

Control Systems: Basic control system components; block diagrammatic description, reduction of block diagrams. Open loop and closed loop (feedback) systems and stability analysis of these systems. Signal flow graphs and their use in determining transfer functions of systems; transient and steady state analysis of LTI control systems and frequency response. Tools and techniques for LTI control system analysis: root loci, Routh-Hurwitz criterion, Bode and Nyquist plots. Control system compensators: elements of lead and lag compensation, elements of Proportional-Integral-Derivative (PID) control. State variable representation and solution of state equation of LTI control systems.

Communications: Random signals and noise: probability, random variables, probability density function, autocorrelation, power spectral density. Analog communication systems: amplitude and angle modulation and demodulation systems, spectral analysis of these operations, superheterodyne receivers; elements of hardware, realizations of analog communication systems; signal-to-noise ratio (SNR) calculations for amplitude modulation (AM) and frequency modulation (FM) for low noise conditions. Fundamentals of information theory and channel capacity theorem. Digital communication systems: pulse code modulation (PCM), differential pulse code modulation (DPCM), digital modulation schemes: amplitude, phase and frequency shift keying schemes (ASK, PSK, FSK), matched filter receivers, bandwidth consideration and probability of error calculations for these schemes. Basics of TDMA, FDMA and CDMA and GSM.

Electromagnetics: Elements of vector calculus: divergence and curl; Gauss and Stokes theorems, Maxwells equations: differential and integral forms. Wave equation, Poynting vector. Plane waves: propagation through various media; reflection and refraction; phase and group velocity; skin depth. Transmission lines: characteristic impedance; impedance transformation; Smith chart; impedance matching; S parameters, pulse excitation. Waveguides: modes in rectangular waveguides; boundary conditions; cut-off frequencies; dispersion relations. Basics of propagation in dielectric waveguide and optical fibers. Basics of Antennas: Dipole antennas; radiation pattern; antenna gain.