Six Weeks Industrial Training

AT

BHUSHAN STEEL LIMITIED

BY

MANINDER SINGH

ROLL NO.: 1409445 (Sem. 4th)

BRANCH: ELECTRICAL

Doaba Khalsa Trust Group of Institutions

Chhokran

INDEX

Introduction Training Supervision Area Salient Feature Of Blast Furnace Plant Overview How A Blast Furnace Works Power Distribution What Is Transformer Types Of Transformer Distribution Transformer

Dry Type Transformer1. Classes Of Insulation2. Efficiency

Oil Type Transformer1. Parts of Oil Type Transformer

6.6KV Switchboard Types Of Motors Used At Blast Furnace

Squirrel Cage Induction Motor 1. Stator2. Rotor3. Reasons For Skewed Rotor

Wound Rotor Motor Motor Starting Methods

1. VVVF Drive2. Soft Starter

Application How Does Soft-starter Works Benefits Of Soft-starters Basic Components Of Soft-starter Advantages

INTRODUCTION:

Bhushan Steel Limited is the largest manufacturer of auto-grade steel in India and

is spending Rs. 260 billion to expand its capacity to 12 million tonnes annually,

from the present installed capacity of around one million tonnes. Gross sales of

Bhushan Steel grew from Rs.5 billion in 2001 to Rs.40 billion in 2007. It earned

net profits of Rs.3.13 billion in 2007 and exported goods worth Rs.12.57 billion.

Its exports include steel for both the automotive and white goods industry and the

list of countries it is exporting to includes several developed countries.

Its biggest expansion is in Odisha – it has signed an agreement with the

Government of Odisha for setting up of a three million tonnes capacity steel plant

at Meramandali in Dhenkanal district,[7] and as part of its total integration of the

steel value chain, Bhushan Steel is in the process of setting up a power plant and

an advanced hot rolling plant on 3,200 acres (13 km2) at Meramandali in

Dhenkanal district near Angul, at a cost of 52 billion and its subsequent backward

integration and expansion to 4 million tonnes.

Brij Bhushan Singal is chairman of board of directors of Bhushan Steel.

Neeraj Singal is the Vice Chairman & Managing Director of Bhushan steel

limited

TRAINING SUPERVISION AREA: - Blast Furnace # 2

A blast furnace is a type of metallurgical furnace used for smelting to produce industrial metals, generally iron, but also others such as lead or copper.

In a blast furnace, fuel, ores, and flux (limestone) are continuously supplied through the top of the furnace, while a hot blast of air (sometimes with oxygen enrichment) is blown into the lower section of the furnace through a series of pipes called tuyeres, so that the chemical reactions take place throughout the furnace as the material moves downward. The end products are usually molten metal and slag phases tapped from the bottom, and flue gases exiting from the top of the furnace. The downward flow of the ore and flux in contact with an upflow of hot, carbon monoxide-rich combustion gases is a countercurrent exchange process.

In contrast, air furnaces (such as reverberatory furnaces) are naturally aspirated, usually by the convection of hot gases in a chimney flue. According to this broad definition, bloomeries for iron, blowing houses for tin, and smelt mills for lead would be classified as blast furnaces. However, the term has usually been limited to those used for smelting iron ore to produce pig iron, an intermediate material used in the production of commercial iron and steel, and the shaft furnaces used in combination with sinter plants in base metals smelting

SALIENT FEATURES OF BLAST FURNACE # 2

Furnace volume - 4186m3

Useful volume - 3814m3

Working volume – 3230m3

Annual Production – 2.5MT

Tap Hole – 4 Nos.

Tuyeres – 34 Nos.

Internal Combustion Stoves – 3 Nos.

Furnace Top Pressure – 2.5 kg/cm2

Furnace Bottom Pressure – 4.1 kg/cm2

Blast Volume (WET) – 350KNM3/HR

Paul Wurth BLT Charging System - Yes

Waste Gas Recovery System – Yes

Slag Granulation Plant – INBA

DE Dusting System in Cast house & Stock House –Yes

Top Recovery Turbine – Yes

Pulverised Coal Injection – 150kg/thm

PLANT OVERVIEW:

HOW A BLAST FURNACE WORKS:

The purpose of a blast furnace is to chemically reduce and physically convert iron oxides into liquid iron called "hot metal". The blast furnace is a huge, steel stack lined with refractory brick, where iron ore, coke and limestone are dumped into the top, and preheated air is blown into the bottom. The raw materials require 6 to 8 hours to descend to the bottom of the furnace where they become the final product of liquid slag and liquid iron. These liquid products are drained from the furnace at regular intervals. The hot air that was blown into the bottom of the furnace ascends to the top in 6 to 8 seconds after going through numerous chemical reactions. Once a blast furnace is started it will continuously run for four to ten years with only short stops to perform planned maintenance.

Iron oxides can come to the blast furnace plant in the form of raw ore, pellets or sinter. The raw ore is removed from the earth and sized into pieces that range from 0.5 to 1.5 inches. This ore is either Hematite (Fe2O3) or Magnetite (Fe3O4) and the iron content ranges from 50% to 70%. This iron rich ore can be charged directly into a blast furnace without any further processing. Iron ore that contains a lower iron content must be processed or beneficiated to increase its iron content. Pellets are produced from this lower iron content ore. This ore is crushed and ground into a powder so the waste material called gangue can be removed. The remaining iron-rich powder is rolled into balls and fired in a furnace to produce strong, marble-sized pellets that contain 60% to 65% iron. Sinter is produced from fine raw ore, small coke, sand-sized limestone and numerous other steel plant waste materials that contain some iron. These fine materials are proportioned to obtain a desired product chemistry then mixed together. This raw material mix is then placed on a sintering strand, which is similar to a steel conveyor belt, where it is ignited by gas fired furnace and fused by the heat from the coke fines into larger size pieces that are from 0.5 to 2.0 inches. The iron ore, pellets and sinter then become the liquid iron produced in the blast furnace with any of their remaining impurities going to the liquid slag.

The coke is produced from a mixture of coals. The coal is crushed and ground into a powder and then charged into an oven. As the oven is heated the coal is cooked so most of the volatile matter such as oil and tar are removed. The cooked coal, called coke, is removed from the oven after 18 to 24 hours of reaction time. The coke is cooled and screened into pieces ranging from one inch to four inches. The coke contains 90 to 93% carbon, some ash and sulfur but compared to raw coal is very strong. The strong pieces of coke with a high energy value provide permeability, heat and gases which are required to reduce and melt the iron ore, pellets and sinter.

The final raw material in the ironmaking process in limestone. The limestone is removed from the earth by blasting with explosives. It is then crushed and screened to a size that ranges from 0.5 inch to 1.5 inch to become blast furnace flux . This flux can be pure high calcium limestone, dolomitic limestone containing magnesia or a blend of the two types of limestone.

Since the limestone is melted to become the slag which removes sulfur and other impurities, the blast furnace operator may blend the different stones to produce the desired slag chemistry and create optimum slag properties such as a low melting point and a high fluidity.

All of the raw materials are stored in an ore field and transferred to the stockhouse before charging. Once these materials are charged into the furnace top, they go through numerous chemical and physical reactions while descending to the bottom of the furnace.

POWER DISTRIBUTION SLD:

WHAT IS A TRANSFORMER?

TRANSFORMER IS A STATIC DEVICE WHICH TRANSFORMS A.C. ELECTRICAL POWER FROM ONE VOLTAGE TO ANOTHER VOLTAGE KEEPING THE FREQUENCY SAME BY ELECTROMAGNETIC INDUCTION.

TYPES OF TRANSFORMER:

DISTRIBUTION TRANSFORMER

POWER TRANSFORMER

CURRENT TRANSFORMER

POTENTIAL TRANSFORMER

GROUNDING TRANSFORMERS

AUTO TRANSFORMERS

Distribution Transformer:

A distribution transformer is a transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer. The invention of a practical efficient transformer made AC power distribution feasible; a system using distribution transformers was demonstrated as early as 1882.

If mounted on a utility pole, they are called pole-mount transformers. If the distribution lines are located at ground level or underground, distribution transformers are mounted on concrete pads and locked in steel cases, thus known as pad-mount transformers.

Distribution transformers normally have ratings less than 200 kVA, although some national standards can describe units up to 5000 kVA as distribution transformers. Since distribution transformers are energized for 24 hours a day (even when they don't carry any load), reducing iron losses has an important role in their design. As they usually don't operate at full load, they are designed to have maximum efficiency at lower loads. To have a better efficiency, voltage regulation in these transformers should be kept to a minimum. Hence they are designed to have small leakage reactance

Distribution Transformer Types

Dry Type Transformer:

Dry Type transformers use air as the cooling medium. Dry Type Transformers can be located closer to the load unlike oil transformers which require special location and civil construction for safety reasons. Locating the transformers near the loads may lead to savings in cable costs and reduced electrical losses.

Moisture Proof In cast-resin dry-type transformers, the complete encapsulation of primary and secondary winding in epoxy resin prevents penetration of moisture into windings. The cast resin offers very good protection against adverse ambient conditions. These transformers can work without disruption of service at 100% humidity.

Immediate Switch on Due to the high grade insulation material, coils are non hygroscopes & the transformer can be switched on directly without pre-drying even after a long period of service interruption.

Impulse Strength Contrary to the conventional dry type transformers the cast coil transformers are better in respect of impulse voltage withstand strength.

Short Circuit Strength Higher dynamic short circuit withstand strength

as compared to oil immersed and conventional dry type transformers because of fibre glass reinforced epoxy encapsulation.

Free of partial discharge's No partial discharges can occur during operation.Resistant against temperature Fluctuation

The insulation material used is glass fibre reinforced with epoxy resin of class 'F' which can withstand wide temperature variation.

Hardly inflammable and self extinguishing

Due to high quality insulation material the transformer is practically non-inflammable by an electrical arc, special fire protection measures are not required.

No Maintenance Required Due to encapsulation of coils with cast resin the coils dimensions are stable & no coil tightening is required to maintain the short circuit strength. Also no check of oil level and electrical insulation/oil is required. This leads to saving in cost on account of maintenance.

No leakage or Pilferage of Oil

As cast resin transformers are solidly cast, problem associated with oil filled transformers like oil leakage and pilferage of oil is completely avoided.

Saving in Space These transformers are generally smaller in dimensions and lesser in weights. The construction and installation cost for the sub-station can be reduced by adopting dry type transformers.

Saving in Civil work cost and LT cables

Without fire or danger of explosion, it is possible to place the transformers near to the load centre. Also, these transformers do not need construction of special fibre brick walls or oil pits, which reduces the overall civil works. Additionally, since LT cables are not required, thers is also saving in cost on account of expensive cable laying works.

Eco-friendly Since no oil is used in these transformers, there are no chances of contamination of ground water due to oil leakage.

DRY TYPE TRANSFORMER

Dry type Transformers - Classes of insulation

Dry-type transformers are available in three general classes of insulation. The main features of insulation are to provide dielectric strength and to be be able to withstand certain thermal limits. Insulation classes are:

220°C (Class R). 180°C (Class H), 155°C (Class F). 130°C (Class B). 105°C (Class A).

Temperature rise ratings are based on full-load rise over ambient (usually 40°C above ambient and are 150°C (available only with Class H insulation), 115°C (available with Class H and Class F insulation) and 80°C (available with Class H, F, and B insulation). A 30°C winding hot spot allowance is provided for each class.

The lower temperature rise transformers are more efficient, particularly at loadings of 50% and higher. Full load losses for 115 °C transformers are about 30% less that those of 150°C transformers. And 80°C transformers have losses that are about 15% less than 115°C transformers and 40% less than 150°C transformers. Full load losses for 150°C transformers range from about 4% to 5% to 30 kVA and smaller to 2% for 500 kVA and larger. When operated continuously at 65% or more of full load, the 115°C transformer will pay for itself over the 150°C transformer in 2 yrs or less( 1 yr. if operated at 90% of full load). the 80°C transformer requires operation at 75% or more of full load for a 2-yr payback, and at 100% load to payback in 1 yr over the 150°C transformer.

If operated continuously at 80% or more of full load, the 80°C transformer will have a payback over the 115°C transformer in 2 yrs or less. You should note that at loadings below 50% of full load, there is essentially no payback for either the 115°C or the 80°C transformer over the 150°C transformer, Also at loadings below 40% the lower temperature rise transformers become less efficient that the 150°C transformers. Thus, not only is there no payback, but also the annual operating cost is higher.

EFFICIENCY :

At Load AT Unity P.F AT 0.8 Lag P.F

100% 99.02 % 98.77% 75% 99.21 % 99.01% 50% 99.37% 99.21% 25% 99.41% 99.27%

OIL TYPE TRANSFORMER:

STANDARD KVA ratings of distribution Transformer

25,63,100,160,200,250,315,400,500,630,750,1000, 1250,1500,2000,2500 KVA.

IS-2026 is the NATIONAL I S STANDARD.

PARTS OF OIL TYPE TRANSFORMER:

MAIN TANK RADIATORS CONSERVATOR EXPLOSION VENT LIFTING LUGS AIR RELEASE PLUG OIL LEVEL INDICATOR TAP CHANGER WHEELS HV/LV BUSHINGS FILTER VALVES OIL FILLING PLUG DRAIN PLUG CABLE BOX

6.6 KV SWITCHBOARD:

Electricity has to be distributed with minimal losses after generation. Unlike a shore based transmission system, where the lengths of the conductors run throughout a country, a shipboard electrical distribution system is short and simple. In this article, the general layout of the main electrical distribution system, along with the main switchboard and emergency switchboard arrangements, will be discussed. The main switchboard is the main power distribution center of the ship. Thus the main bus bars are contained within the switchboard feeding various ship board auxiliaries. A ship may contain two or more generators connected to the main bus bar via the circuit breaker. Various protection for the generators like overload, reverse power, etc. are connected to circuit breaker such that the faulty generator is electrically isolated from the main bus bar. From the main bus bar, the electrical power is supplied to various ship board auxiliaries like pumps, blowers, compressors, etc. The main switch board has various measuring and monitoring devices like ammeters, voltmeters, frequency meters, watt meters, synchroscope, and power factor meters.

6.6kv Switchboard supply power to the equipment like as transformer

(6.6kv/433v) and motors. In these switchboard vacuum circuit breaker (VCB) are

used to switch on/off the motor or transformer. For protection there are several

equipments used. Equipments used in 6.6kv board Details are given bellow:-

Vacuum Circuit Breaker (VCB) Tripping Relay (86) REM615/REF615/REU610 Temperature Scanner Load Manager TNC Switch Synchronous Check Relay Ammeter Test Terminal Block (TTB) Beacon Lamps Indications Lamps Annunciator Surge Arrestor Current Transformer Potential Transformer Bus-Bar Isolator

TYPES OF MOTOR USED AT BLAST FURNACE:

SQUIRREL CAGE INDUCTION MOTOR:

The stator is the outer most component in the motor which can be seen. It may be constructed for single phase, three phase or even poly phase motors. But basically only the windings on the stator vary, not the basic layout of the stator. It is almost same for any given synchronous motor or a generator. It is made up of number of stampings, which are slotted to receive the windings. Lets see the construction of a three phase stator. The three phase windings are placed on the slots of laminated core and these windings are electrically spaced 120 degrees apart. These windings are connected as either star or delta depending upon the requirement. The leads are taken out usually three in number, brought out to the terminal box mounted on the motor frame. The insulations between the windings are generally varnish or oxide coated.

Rotor: Squirrel Cage Rotor:

This kind of rotor consists of a cylindrical laminated core with parallel slots for carrying the rotor conductors, which are not wires, as we think, but thick, heavy bars of copper or aluminium (aluminium) or its alloys. The conductor bars are inserted from one end of the rotor and as one bar in each slot. There are end rings which are welded or electrically braced or even bolted at both ends of the rotor, thus maintaining electrical continuity. These end rings are short-circuited, after which they give a beautiful look similar to a squirrel thus the name.One important point to be noted is that the end rings and the rotor conducting bars are permanently short-circuited, thus it is not possible to add any external resistance in series with the rotor circuit for starting purpose. The rotor conducting bars are usually not parallel to the shaft, but are purposely given slight skew. In small motors, the rotor is fabricated in a different way. The entire rotor core is placed in a mould and the rotor bars & end-rings are cast into one piece. The metal commonly used is aluminium alloy. Some very small rotors which operate on the basis of eddy current, have their rotor as solid steel without any conductors.

Reasons for Having Skewed Rotor

1. It helps in reduction of magnetic hum, thus keeping the motor quiet,

2. It also helps to avoid “Cogging”, i.e. locking tendency of the rotor. The

tendency of rotor teeth remaining under the stator teeth due to the direct

magnetic attraction between the two,

3. Increase in effective ratio of transformation between stator & rotor,

4. Increased rotor resistance due to comparatively lengthier rotor conductor

bars,

5. Increased slip for a given torque.

WOUND ROTOR MOTOR:

A wound-rotor motor is a type of induction motor where the rotor windings are connected through slip rings to external resistances. Adjusting the resistance allows control of the speed/torque characteristic of the motor. Wound-rotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit; as the motor accelerates, the resistance can be decreased.

Compared to a squirrel-cage rotor, the rotor of the slip ring motor has more winding turns; the induced voltage is then higher, and the current lower, than for a squirrel-cage rotor. During the start-up a typical rotor has 3 poles connected to the slip ring. Each pole is wired in series with a variable power resistor. When the motor reaches full speed the rotor poles are switched to short circuit. During start-up the resistors reduce the field strength at the stator. As a result the inrush current is reduced. Another important advantage over squirrel-cage motors is higher starting torque.

A wound-rotor motor can be used in several forms of adjustable-speed drive. Certain types of variable-speed drives recover slip-frequency power from the rotor circuit and feed it back to the supply, allowing wide speed range with high energy efficiency. Doubly fed electric machines use the slip rings to supply external power to the rotor circuit, allowing wide-range speed control. Today speed control by use of slip ring motor is mostly superseded by induction motors with variable-frequency drives.

MOTOR STARTING METHODS:

VARIABLE VOLTAGE VARIABLE FREQUENCY DRIVE:

The present day industry categorizes AC motor drives into two distinct categories — Induction Motor Drives, and Permanent Magnet AC Motor Drives. The basic difference between the two types of drives is performance and cost.Induction motor still forms the work horse of today’s industry. Applications that use induction motor may not need very high precision position and velocity control. Such applications typically use what is known in the industry as“General Purpose AC Motor Drives” However, the machine tool industry that caters to the semiconductor manufacturing and other sophisticated industries, require highly precise and controlled motion. Permanent magnet motors are the motor of choice because of their smaller size, higher efficiency, lower inertia, and hence higher controllability. Such motors are clubbed into the Servo Motor category and are controlled by Permanent Magnet AC Motor (PMAC) Drivesand are typically more expensive than their induction motor counterpart.General Purpose AC Motor Drives — V/f Control The power structure of the General Purpose AC Motor Drives is similar to the PMAC motor drives. Both of these drives are referred to as Voltage Source Inverters, a term which will soon be clear. Since the power topology includes a large DC bus capacitor as a filter, and since it is the voltage that is modulated to provide variable voltage, variable

frequency to the AC motor, such an inverter topology is called a Voltage Source Inverter and forms the integral part of most present day AC motor Drives. A typicalschematic of the present day AC motor drive The general purpose AC motor drives typically provide constant flux into the induction motor. Since the motor flux is the ratio of the voltage to the frequency (V/f) applied tothe motor, this ratio is held constant to achieve constant flux operation. The motor current increases almost linearly with load. Conveyor belts and other frictional loads require such profiles. For centrifugal loads like fans and pumps, the fluxin motor can be altered to follow a square function. By doing this, the power consumed by the motor becomes a cubic function of speed (Pocf) enabling significant energy savings. Even if the V/f is held constant in these types ofapplications, there is still significant energy savings compared to constant speed drives, where relatively large losses are associated with valve or damper control. Thanks to the square type torque characteristics of the load, voltage reduction at lower speed range is possible improves efficiency further. The resulting improvement in efficiency is so significant that even the member countries that ratified the Kyoto agreement in the year 2000 agreed to convert fansand pumps from being operated directly across the line to be operated via AC motor drives to save energy and reduce the overall carbon foot print of a given plant. It is significant and important only, for those countries but for all peopleusing centrifugal loads to convert the fixed speed fans and pumps to variable speed.

SOFT-STARTER:

A soft starter is a solid-state device that protects AC electric motors from damage caused by sudden influxes of power by limiting the large initial inrush of current associated with motor startup. They provide a gentle ramp up to full speed and are used only at startup (and stop, if equipped). Ramping up the initial voltage to the motor produces this gradual start. Soft starters are also known as reduced voltage soft starters (RVSS).

ApplicationsSoft starters are used in applications where:• Speed and torque control are required only during startup (and stop if equipped with soft stop)• Reducing large startup inrush currents associated with a large motor is required• The mechanical system requires a gentle start to relieve torque spikes and tension associated with normal startup (for example, conveyors, belt-driven systems, gears, and so on)• Pumps are used to eliminate pressure surges caused in piping systems when fluid changes direction rapidly

How does a soft starter work?Electrical soft starters temporarily reduce voltage or current input by reducing torque. Some soft starters may use solid-state devices to help control the flow of the current. They can control one to three phases, with three-phase control usually producing better results

Most soft starters use a series of thyristors or silicon controlled rectifiers (SCRs) to reduce the voltage. In the normal OFF state, the SCRs restrict current, but in the normal ON state, the SCRs allow current. The SCRs are engaged during ramp up, and bypass contactors are pulled in after maximum speed is achieved. This helpsto significantly reduce motor heating.

.

Benefits of choosing a soft starterSoft starters are often the more economical choice for applications that require speed and torque control only during motor startup. Additionally, they are often the ideal solution for applications where space is a concern, as they usually take up less space than variable frequency drives.

Soft Start Definition

In technical terms, a soft starter is any device which reduces the torque applied to the electric motor. It generally consists of solid state devices like thyristors to control the application of supply voltage to the motor. The starter works on the fact that the torque is proportional to the square of the starting current, which in turn is proportional to the applied voltage. Thus the torque and the current can be adjusted by reducing the voltage at the time of starting the motor.

There can be two types of control using soft starter:

1) Open Control: A start voltage is applied with time, irrespective of the current drawn or the speed of the motor. For each phase two SCRs are connected back to back and the SCRs are conducted initially at a delay of 180 degrees during the respective half wave cycles (for which each SCR conducts). This delay is reduced gradually with time until the applied voltage ramps up to the full supply voltage. This is also known as Time Voltage Ramp System. This method is not relevant as it doesn’t actually control the motor acceleration.

2) Closed Loop Control: Any of the motor output characteristics like the current drawn or the speed is monitored and the starting voltage is modified accordingly to get the required response.  The current in each phase is monitored and if it exceeds a certain set point, the time voltage ramp is halted.Thus basic principle of soft starter is by controlling the conduction angle of the SCRs the application of supply voltage can be controlled.

Components of a basic soft starter

Power switches like SCRs which need to be phase controlled such that they are applied for each part of the cycle. For a 3 phase motor, two SCRs are connected back to back for each phase. The switching devices need to be rated at least three times more than the line voltage.

Control Logic using PID controllers or Microcontrollers or any other logic to control the application of gate voltage to the SCR, i.e. to control the firing angle of SCRs in order to make the SCR conduct at the required part of the supply voltage cycle.

Advantages of Soft Start

Now that we have learnt about how an electronic soft start system works, let us recollect few reasons why it is preferred over other methods.

Improved Efficiency: The efficiency of soft starter system using solid state switches is more owing to the low on state voltage.

Controlled Start up: The starting current can be controlled smoothly by easily altering the starting voltage and this ensures smooth starting of the motor without any jerks.

Controlled acceleration: Motor acceleration is controlled smoothly. Low Cost and size: This is ensured with the use of solid state switches.