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TRAINING REPORT

By Anil Nair Under the guidance of Mr. R.K. Mishra, General Manager (Electrical & Instrumentation)

ACKNOWLEDGEMENT

Though words are seldom sufficient to express gratitude and feelings, I would like to fulfill a fraction of my moral obligation by expressing a word of gratitude to all those who have helped me to complete the training successfully.

First of all I would like to thank Mr. R.K.Mishra (General Manager, Electronics and Instrumentation) UNIVERSAL CABLES LIMITED, for his guidance,without which this training would have been incomplete.

I would like to thank Mr. Sudhir Jain, (Asst. Vice President, Administration), UNIVERSAL CABLES LIMITED, Universal Cables Limited for accepting me as a trainee and giving me opportunity to visit the company.

I would also like to thank all the staff member and wiremen at UCL for giving suggestions, encouragement and support which have been instrumental in the study.

Submitted by:Anil Nair

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Content

Company Profile Controllers

i) Temperature Controllerii) Diameter Controlleriii) PF controller

Cablesi) Basic Process of Manufacturing Cablesii) VCV Line Extrusioniii) CCV Line Extrusion

Automationi) PLC Panelsii) Communication System of PLC with other Devices

Power Distribution Telephone Exchange

i) EPABX

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Company Profile

UNIVERSAL CABLES LTD.

Universal Cables Limited (UCL) was established in the year 1962 as a modern mass production unit to manufacture paper insulated power cables in technical collaboration with world's largest cable producer BICC, UK. Late Shri M.P. Birla, who had adorned the chair of the Company for over 25 years since its inception, enabled the Company to flourish in a highly competitive world, while distinguishing itself by the latest technological tie-ups with the foremost leaders in the world of this industry and the most up-to date technology.

Universal Cables Limited entered into a collaboration agreement with ABB high Voltage Cables, Sweden in 1977 to manufacture cross-linked Polythene Power Cable for the first time in the country. The Company is the foremost manufacturer of XLPE Cables with modern dry cured dry cooled process for voltage range extending from 1.1 to Extra High Voltage up to 132 KV grade.

Under the collaboration Agreement with ABB high Voltage Cables, Sweden, UCL brought in complete know how of compounding of Polymer and produced complete range of dielectrics presently used in all special cables.

In 1983, UCL embarked on a joint venture with MPAVN to manufacture Jelly Filled Telephone Cable in technical collaboration with one of the world's leading manufacturers of Telephone Cable, Ericsson Cable AB, Sweden. This plant was incorporated as Vindhya Telelinks Limited (VTL) and is situated at Rewa, only 50Km away from its Power Cable Plant at Satna.

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Since 1985, ABB High Voltage Cables, Sweden, is further assisting UCL to manufacture Fluroplastic Cables, specifically for very high temperature operation and high frequency signalling circuitry.

In 1993, UCL & VTL jointly entered into the field of optical communication by way of manufacturing Optical Fibre Cables in technical and financial collaboration with Ericsson Cables AB, Sweden. This marked the birth of Birla Ericssion Optical Limited (BEOL).

QUALITY CONSCIOUSNESSWhether conventional or specially designed to any Indian or International specification, UCL's products are put to the grill of rigorous in-process quality cheeks by stage inspection and testing Its quality is taken as standard in the world market.

MEANS ARE AS IMPORTANT AS THE ENDUCL proudly claims to have the most sophisticated plant, equipment, laboratory and testing facilities available in the country. The entire plant is housed in dust-proof pressurized building to ensure consistency in the product quality.

CERTIFICATION

The above claim is certified by various test authorities of the country like NTH, Calcutta and CPRI Bhopal & Bangalore and all consultants like Ell, DCPL, M.N. Dastur, Lloyds register of Shipping, MECON, Crown Agents and others. This confirms the dependability and reliability of UCL products.

ISI MARKING

All standard UNISTAR cables are ISI marked.

IS/ISO QUALITY CERTIFICATION

UCL is accredited with IS/ISO 9001/2000 Quality Systems Certification in recognition of the High Quality Standard of its cables. The company is also accredited for its well-established environmental friendly activities and atmosphere.

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TECHNICAL SERVICESThe Company welcomes enquiries on cable engineering problems and provides solutions through its design and development team. It also assists customers in cable design to suit their specific requirement. A team of experts is always ready to assist cable engineers for installation, laying and jointing cable systems throughout the India. When requested the technical dept. of the company provides help to customers for fault location and other related problem.

RESEARCH & DEVELOPMENTUCL emphasizes on in-house Research and Development. The R & D programme is mainly directed to applied research for product development, process development and technological up gradation. The R & D laboratory of UCL is a recognized unit of Department of Scientific and Industrial Research of Govt. of India. This laboratory has developed many new Cables for special applications such as FRLS Cables, Ship wiring, Air craft wiring, Radars, Submarine, Medical Equipments etc.

CAPACITORS

UCL set up its Capacitor Division in the year 1967, in technical collaboration with world renowned TOSHIBA, to manufacture Paper & Power Capacitors. In 1977 this division entered into a technical collaboration with General Electric Company of USA, to manufacture Mixed Dielectric Capacitors. Subsequently the collaboration was extended to include All Polypro- propylene (All-PP) Dielectric Capacitors impregnated with Non PCB oil. Today the Capacitor Division is rated to be the foremost manufacturer of All-PP Power Capacitors in LT & HT range in the country.

This division offers complete schemes for power factor improvement and can supply capacitors along with associated equipments on turnkey basis. It can also carry out harmonic analysis of Power System on request and design & supply Filter Banks. EXPORTS UCL also exports its products to various countries of the world and has earned due recognition for its export efforts. Universal Cables limited is a vibrant progressive company, a leader in its field of activities, serving the aspiration of the nation in the field of Power Development

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Controllers

What are controllers?

Controllers are devices, using mechanical, hydraulics or electronics techniques often in combination, but in the form of a microprocessor or computer which monitors and physically alters the operating condition of a given dynamic system.

Types of Controllers

There are three basic types of controllers:-

On-off controller PID Controller

Depending upon the system to be controlled, the operator will be able to use one type or another to control the process.

On/Off Controllers

On-off controllers are simplest form of control devices. The output from the device is either on or off, with no middle state. There is not much control over the process in this type on controllers. There occurs a continuous switching if

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Controllers

On/Off Controller PID Controllers

the response time is very small. Due to continuous switching the other sensitive devices in the system might get affected. On-off control is usually used where a precise control is not necessary. These types of controllers are mainly used in basic alarming system or switching systems.

PID Controllers

The third controller type provides proportional with integral and derivative control, or PID. This controller combines proportional control with two additional adjustments, which helps the unit automatically compensate for changes in the system. These adjustments, integral and derivative, are expressed in time-based units; they are also referred to by their reciprocals, RESET and RATE, respectively. The proportional, integral and derivative terms must be individually adjusted or “tuned” to a particular system using trial and error. It provides the most accurate and stable control of the three controller types, and is best used in systems which have a relatively small mass, those which react quickly to changes in the energy added to the process. It is recommended in systems where the load changes often and the controller is expected to compensate automatically due to frequent changes in set point, the amount of energy available, or the mass to be controlled. Different Types of Controllers used in the System

There different types of controllers are present based on the application. Controllers run on the basis of many physical quantities such as temperature, capacitance, power factor etc. Some of the controllers which are used in the plant are:

Temperature Controller Diameter Controller PF controller Pressure Controllers

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Temperature Controller

A temperature controller is a type of PID controller used to control the process by taking an input from a temperature sensor and has an output that is connected to a control element such as a heater or fan. It accurately controls the process without extensive operator involvement.

Working of a basic temperature controller

The temperature controller basic work is to monitor the temperature and control the process. The thermocouple acts as the input for the temperature controller. The controller then compares the actual temperature to the desired control temperature or set point, and provides an output to a control element mainly a contactor. If the detected temperature is lower than the set point the command is sent through B1 (which is the output of the relay circuit) and the contactor is turn on. When the target approaches the setpoint the switching action takes place at a definite rate and the process is controlled. Once the temperature is above the set point the contactor is switched off. Once the set point is attained the contactor if switched off and unless and until the temperature drops, the controller does allow the contactor to switched on. Thus the temperature controller attains the control of the process.

Controller Circuit Diagram of working of Temperature

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Temperature Controller

Diameter Controller

Diameter controller is also a PID type of controller. It monitors the diameter of the cable and controls the process. It’s mainly used to control the line rate and the extruder.

How diameter of a cable is measured?

Diameter is measured using different methods. Basic diameter detector measures the diameter with the help of a light source and a tray of photo diodes. The cable is passed in between the light source and the tray of photo diodes. When the light is emitted, it falls on the photo diode and generates a voltage difference. The light does not fall of the portion of the tray which is the diameter of the cable and those photo diodes do not have a voltage. Detecting the voltage the detector decides the diameter of the cable.

Nowadays X-rays are used for this purpose. The x-rays cut the through the cable, and gives the cross sectional view of it. This type of diameter detectors are used where cable is insulated with two or materials and diameter helps a curtail role in the quality of the cable.

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Basic Diameter Detector

Output of Sikora Detector (One of the X-ray diameter detectors used in the plant)

Basic working of diameter controller

Diameter controller is basically used for maintaining the desired thickness of the insulation of the cables. Diameter controller takes the input from the diameter detector (Dia-head). If the diameter of the cable is less than the set point, then the controller will decrease the line rate or increase the rpm of the extruder. If the diameter is more than the set point then the controller increases the line rate or decreases the rpm of the extruder thus maintaining the diameter of the cable.

PF Controller

Power factor controller or PF controller is a controller with the help of which the power factor in the power supply line can be controlled and the power loss can be controlled.

What is power factor?

Power factor is the ratio of the real power and the apparent power drawn by the electrical load.

Power factor (P . F . )= RealPower (kw )ApparentPower (kVA )

Why power factor correction is very important?

In industries due to the motors and other heavy coiling machineries, a lag is created in the phase of the voltage and current. This results in the formation of the apparent power.

Apparent power= Real powerPower factor

The apparent power is always greater than the real power as a result there will be a power loss. The power loss can be controlled if the power factor is made unity.

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A PF controller

ApparentPower (kVA )

Reactive Power (kVar )

ᵩ

RealPower (kw )

The relational between the apparent and real power can be explained with the right angled triangle. An angle is created between the apparent and real power calledΦ. The power factor can be said to be equal tocosΦ. So if the angle between the apparent and the real power is reduced and made to tend to zero so the power factor tend to unity. By doing this the power loss is controlled.

How does a P.F. controller work?

The power factor controller or the PF controller monitors the power factor of the supply line and checks whether the power factor is near to the unity or not. If the current is lagging the power factor pass the supply line through the suitable capacitor banks and make the current to be in phase with the voltage. If the power factor is equal to the set power factor then the capacitor banks are switched off and the power factor is monitored.

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CablesIntroduction

The electrical current in a conductor causes a voltage drop and power losses. The temperature rise in the cable caused by the losses must be kept within certain limits order not to shorten the service life of the cable. The temperature limit varies with the type of cable, or more precisely the type of insulation. The best way to keep the temperature within limits specified for the type of cable is to choose the conductor cross-section so that the cable and its surroundings with the actual continuous load achieve thermal balance at a temperature below or equal to the temperature limit recommended. Cable type and size should be selected keeping in view the following:-

Application Working voltage; earthed or unearthed neutral system Load current, load factor, starting duty and frequency Installation method The environment in which the cable has to operate Short circuit current and system protection Acceptable voltage drop Economies

How the above factors influence on the choice of cable?

1) Application: Application of the cable determines the basic factors for the choice of cable type and the rules according to which it must be manufactured. Following are the major factors for choice of cable type.

a) Conductor materials: No doubt copper is better conductor material owing to its high electrical conductivity and other electrical/mechanical properties but due to its high cost and scarcity, researches are being carried out to find other cheaper and abundant metals which may be a close substitute to copper in electrical application. Aluminium conductors are being used in place of copper conductors for the past many years and have proved to be quite satisfactory. The lower

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conductivity of an Aluminium (61% of the annealed copper) results in increased dimensions of the cable and ultimately of conduits and fittings for the same current carrying capacity as that of a copper conductor cable. Aluminium conductor cables although bigger and somewhat stiffer when lower number of wires is used for the conductor than the equivalent copper conductor cables, are still flexible enough to be installed where a copper conductor cable was formerly used. The advantages of the lighter weight offset the disadvantages of larger sizes for a given capacity. The use of Aluminium conductor cables should be preferred as far as possible. The use of flexible copper conductor is recommended where very high degree of flexibility is required as in the case of mines etc.

b) Insulating materials: The right type of insulation material for a particular usage depends upon the voltage grade, operating temperature required, degree of flexibility, current capacity requirement and restrictions on size etc. and other climatic conditions.

c) Metallic Sheathing: Either pure lead or different lead alloys are used for Sheathing of PILC cables or each has its own advantages. The most common and popular alloy is lead Alloy 'E'.

d) Bedding and Serving materials: In case of PVC cables the normal bedding and serving material is PVC compound. The normal bedding and serving in case of PILC cables consist of a combination of an impregnated paper, cotton and Hessian tapes and bituminous compound. These materials provide protection against corrosion of armour and lead and are suitable in great majority of installations. However, in special cases where severe chemical corrosion is to be encountered, the use of PVC bedding and PVC serving is recommended.

e) Armouring: The purpose of armour is to provide mechanical protection to the cable and to facilitate earthling for safety requirements. This also carries phase to ground fault currents of the system safely. Double steel tape provides good mechanical protection but when in addition longitudinal stresses are encountered during the installation or in service, steel wire/strip armouring is recommended for vertical armouring should be preferred. Double wire runs, river crossing, cables

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laid on bridges and mine shafts etc. where longitudinal stresses are expected.

2) The system voltage determines the voltage class of the cables.

3) The current rating is, in general, the decisive factors for fixing conductor cross-section. But in certain applications where intermittent load is required, it is more relevant to use the squared average r.m.s. current with a reduced cross section.

4) The power cables must be capable of carrying, the required normal full load current continuously under the site conditions throughout the year. Therefore, the current ratings specified must be corrected to site conditions by applying suitable derating/uprating factors depending upon –

a) Ground or ambient air temperature (max.)

b) Thermal resistivity of soil during dry season.

c) Total number of cables/circuits in groups.

5) Chemical substances in the environment might cause special stringent requirements on the outer covering. If it is necessary to reduce the propagation of fire along cable route combined with low corrosivity, toxicity and smoke generation characteristics for cables, "FRLS' cables (Flame Retardant low Smoke) with thermoplastic or thermosetting material or fire survival cables with elastomeric material should be used. These types of cables are designed with special composition of protective sheath materials, and by using beat barrier tapes etc. for use in such critical fire risk installations.

6) Short circuit current together with duration of short circuit determines the short circuit energy the cable insulation has to with stand thermally. In certain cases a larger size of cable then the cable required for normal full load current may be needed to match system short circuit current levels. Voltage drop is also a major factor in deciding the conductor size of the cable. The cross section of the cable should be chosen such that voltage drop of the cable for the given route length does not exceed the statutory requirement.

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7) Naturally, the most economical construction and the size of the cable consistent with required current carrying capacity and laying condition has to be selected. Thus the selection of particular type of cable i.e. PVC, XLPE, PILC or rubber and the particular material for screening, sheathing, bedding, armouring or serving etc. out of many choices available depends upon the usages, laying and climatic conditions. The design of the cable for a particular application must be optimized taking into account all the above-mentioned factors. In case expert guidance in this respect is desired, please contact UCI Technical Service Division. UCL SATNA

Manufacturing process of CablesThe different stages of manufacturing consist of the following different types of processes:

Wire Drawing – Annealing Tinning Bunching Stranding Insulation

(For Paper/PVC/Rubber/XLPE/Fluroplastic/Polythelene)

Laying Impregnation Lead Sheathing Bedding – Extruded/wrapped/fibrous lapping Armouring Round wire/Flat strip/Steel tape Sheathing/ Serving Extruded/Fibrous lapping

The details of above manufacturing processes are as follows:

Conductor:

Wires of different sizes are drawn from Aluminium/Copper rods on wire-drawing machines. The size (diameter) of wire depends upon the overall cross sectional area of the ultimate cable under manufacture as well as the flexibility requirement. Annealed copper Wires for flexible rubber cables are then tinned before they are released for next process. The tinning is done by passing the cleaned cu. wires seated with the flux through molten tin both. The excess of tin adhering to wire surface is wiped out by means of wipers.

Stranding:

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The Al or Cu. wires or tinned copper wires as the case may be are bunched/stranded together. The direction of stranding of alternate layers is always kept in opposite direction in order to have tight and balanced configuration of wires. The standard Conductor may be compact circular or shaped as per the cable construction.

Insulation:

PVC: Different type of PVC compounds are used for required Physical & electrical properties and continuous operating temperature of cables. PVC compound extruded over conductor by extrusion process on different sizes of extruders as per the size of conductor. In line to extrusion process H.V. testing (Spark testing) is being done to check the quality of extruded core.

Rubber - Natural or synthetic rubber based compounds are prepared to meet the physical & Elec. properties and continues operating temperature of cable. Various types of rubber compounds are then extruded over the conductor as per the requirement of the customer.

Paper insulation - In this case insulated paper tapes are lapped on conductor. The thickness of insulation is built up by required number of paper tapes according to voltage grade of cables. The top layer of paper tapes is suitably numbered for core identification.

XLPE – XLPE cables have become very much popular now a day. These cables are replacing paper-insulated cables right from low voltage grade to extra high voltage grade. In these cables two types of constructions are used i.e. screened and unscreened. 11 KV and above grade cables are all screened. Conductor screen, insulation and insulation screen are generally applied in one operation called dual-tandem process. M/s Universal Cables Ltd is one of the pioneer cable manufacturers of XLPE cable up to 132 KV grade cables in INDIA.

Vulcanization/Cross-linking:

Rubber and XLPE cables are vulcanized after extrusion. This process is done just after extrusion on CV/CCV/PLCV lines. This process is done to improve the electrical and physio-mechanical properties of rubber and polyethylene compounds. In some cases batch vulcanization is carried out for rubber cables and low voltage XLPE cables.

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Laying up of cables:

The insulated cores are laid up along with filling material and twisted to get approximate circular Cable. A binding tape is also provided to hold the fillers and maintain the circularity of laid up cables.In case of paper-insulated cables if the cables are belted type, belt insulation is done along with laying up process by providing required no. of paper tapes and in screened type cables copper woven fabric tape is provided over laid up cores.

Impregnation process :

Paper insulated cables need a special process known as impregnation. The

function of this process is to extract moisture out of paper insulation and impregnate the insulation with moisture resistant insulating compound. Heating the Cable under vacuum for some period and then filling the insulating compound over cable within the impregnating vessel do this process. The cycle of drying flooding and cooling etc. depends on size and voltage grade of cables. By impregnation the electrical properties of paper insulation are enhanced. Procedure adopted for drying and impregnation of paper-insulated cables comprises the following stages:

Rewinding the cables in impregnation trays Loading the trays in the impregnation tanks Heating the cables under vacuum Impregnating of cables with impregnation compound for required

period Unloading the cable-trays from the tanks after impregnation. The compound used for impregnation is a petroleum product and has

excellent electrical and mechanical properties.

Lead sheathing:

After impregnation, lead sheath is applied over the paper-insulated cables. This process is done by sleeve extrusion (pipe extrusion). The object of Lead sheathing is to prevent the entry of moisture in the impregnated cable while maintaining the flexibility of cable.

Inner Sheathing/Bedding:

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PVC and Rubber insulated cables are provided with inner sheathing over laid up cores as bedding for armouring. In case on PVC cables inner sheathing may be done by lapping PVC/PE tapes or by PVC extrusion but in case of rubber insulated cables rubber extrusion is done for this purpose.Armouring The armouring is provided to provide mechanical protection of cables during handling and installation. This is done by providing galv. round steel wires or galvanised steel strips or double steel tapes over the bedded cables.Though the main function of armouring is to protect the cable from outside mechanical damages to the cable but it also serves the purpose of carrying the short circuit current produced during system failure or any type of short circuit in the system.

Sheathing/Serving:

After armouring or in case of un-armoured cables, the laid and bedded cables are provided with a protective sheathing of extruded PVC or PE sheath. Paper insulated cables are generally provided with a fibrous lapped serving but PVC or any other type of extruded sheath can also be given if required.

Final testing :

All cables are rewound in proper size wooden/steel reels and sent to testing section where all the cables are subjected to rigorous electrical and physical tests. Both the ends of cables after testing are sealed and given a unique identification number. These are then handed over to marketing department for onward dispatch to relevant customer

Quality control

In universal cables quality is maintained by following an inbuilt quality system which is based on international specification IS/ISO 9001.Products are tested and processes are controlled at all stages of manufactures from raw material to the finished stage. In addition certain standards procedures are adopted in order to ensure that product successfully fulfils the customer requirement.

Extra high Voltage XLPE Cables

Introduction:

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UNIVERSAL CABLES LTD, the pioneer of XLPE cables in India, manufactures Extra High Voltage (EHV) XLPE cables in the range of 66-220 kV using ‘Vertical Continuous Vulcanizing (VCV) technology in technical collaboration with World Leader in Cable manufacturing, FURUKAWA ELECTRIC CO. LTD. (In association with VISCAS Corporation, Japan). This technology for EHV XLPE Cable manufacturing process is the only of its kind in the Country.EHV Underground Power Transmission is the solution for meeting today’s growing power demand of the power starved Metro Cities. Underground Power Transmission System requires highest reliability to ensure uninterrupted power supply.

The main cutting edge features of this technology as True simultaneous triple extrusion with single (common) cross-head, Dry cure dry cooled process, Dimensional accuracy for perfect geometry with Zero eccentricity/ovality of the insulation, Class 1000 cleanliness level with completely closed material handling system, Online X-Ray monitoring system, Direct gravitational feeding of XLPE compound, Control and Monitoring in production process using SCADA, all add up to unmatched quality standard to ensure reliable and efficient performance of the cable throughout its service life.

Process of Manufacturing EHV XPLE:

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Extrusion and Curing rocess VCV LineThe system adopted for insulation of EHV XLPE cable is DRY Curing for cross linking in Vertical Continuous Vulcanizing(VCV). The VCV line having common

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VCV Plant

head for triple extrusion ensures excellent concentricity, prefect bonding of insulation and semiconducting layers, smooth interfaces free from protrusions provides superior di-electric properties for very high voltage cable. On-line monitoring and controlin the production process ensures adherence to specified Nd strict dimensional standards. The process adopted for cross linking ensures that the cables are kept absolutely dry during the curing process. This eliminates the chances of electrochemical treeing during the full life of the cable. The outstanding characteristic of XLPE cables manufactured by VCV line are:

True simultaneous triple extrusion with single (common) cross head conductor screen, insulation and insulation shield applied in single process. This provides perfect bonding of tinsulation and semicon layers with smooth boundary and free of protrusions.

Completely dry curing process prevents formulation of micro voids and eliminates mositure contents in the XLPE insulation . This also prevents electrochemical tree fromulation in the insulation and capable to withstand higher stress voltage.

Dimensional accuracy with prefect geometry with zero eccentricity/ovality of the insulation. Theis enables uniform stress distribution over the insulation.

Class 1000 cleanliness level in manufacturing with completely closed material handing system. This prevents insulation contamination which is an imperative for Extra High Voltage Cables enabling high impulse and breakdown voltage levels.

HV/MV XPLE Cables

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Extrusion and Curing at CCV LineKey features of Continuous Catenary Vulcanization (CCV) line

HV/MV XPLE cables are insulated

Triple headed cross linking extruder

Diameter is controlled using SIKORA X-ray type diameter controller.

HMI controlled heating zones.

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HMI controller display of CCV Line

AUTOMATION

IntroductionAutomation refers to a process of optimization of energy consumption (Heat, Light, Fuels, water etc.), and optimization of operation and maintenance cost through a closed loop direct digital and analog control. Supervision and regulation of the various service equipments, using computer network with field interface units (I/O Modules) and signal conditioners (Sensors and signal converters).It facilitates in remote operation of equipments. It replaces hardware wired annunciaters, mimic panels, and local control desks.

Importance of Automation

The manufacturing process which considered to be highly dynamic as variances occur at each stage of input. An expert operator is, however, required to run the plant in a stable condition at all times. Moreover, each operator response to given situation may be different. Hence, a software solution consisting of fuzzy logic, regression analysis, neural networks are required to capture the expert knowledge to take action well in advance to achieve optimization on a continuous basis.

Automating System

PLC NETWORK SCADA DCS CONTROLLERS

Introduction to PLC

A PLC is a device which replaces the necessary sequential relay circuits for machine control. A PLC can be considered as a versatile version of such a controller. It is a device, which can accept multiple inputs, of different kinds, of different voltage levels, from various different devices and different parts of a process or a machine. Based upon the state of these inputs the PLC acts further. It controls various devices by turning on/off the outputs that these devices are connected. The logic on which the inputs are related to the outputs

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or the Logic by which the devices connected to PLC are controlled can be programmed, thus the name Programmable Logic Controller.

The programming of a PLC is generally done through programming software or a dedicated programming terminal. Because of this flexibility of programming that a PLC offers a PLC finds many different, almost endless applications in the industry. A PLC can be programmed and reprogrammed to suit to just about any application that one can think of.

PLC's have a wide area of applicability, in Machining, Material Handling, Automation etc.

PLC ARCHITECTURE

Memory Section Stores user logic, state RAM, system overhead in battery backed CMOS RAM & system’s executive firmware in nonvolatile ROM.

CPU Section Solves the user logic program based on the current input values in state RAM, then updates the output values in state RAM.

I/O processing Section Directs the flow of signals from input modules to state RAM and provides a path over which output signals from CPU’s logic solve are sent to output module.

Communication SectionCommunication section helps PLC to communicate with programming panels, host computers, hand-held diagnostic tools, and other peripheral (master) devices as well as with other PLCs and nodes on a communication network.

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Block Diagram of PLC

Basic PLC operation

PLCs consist of input modules or points, a Central Processing Unit (CPU), and output modules or points. An input accepts a variety of digital or analog signals from various field devices (sensors) and converts them into a logic signal that can be used by the CPU. The CPU makes decisions and executes control instructions based on program instructions in memory. Output modules convert control instructions from the CPU into a digital or analog signal that can be used to control various field devices (actuators). A programming device is used to input the desired instructions. These instructions determine what the PLC will do for a specific input. An operator interface device allows process information to be displayed and new control parameters to be entered.

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Communication System of PLCCommunication is mainly used by plc for communicating with the drives and other field devices. The communication channel is used for data exchange and passing the commands to control the system.

There are basically four types of protocols are used for Communication: USS Protocol PROFIBUS Protocol Modbus Protocol PROFINET Protocol

PROFIBUS protocol is mainly used for the communication between the PLCs and other devices.

PROFIBUS Protocol:PROFIBUS protocol is commonly used type of protocol for communication between different devices and PLC. It is a standard for fieldbus communication in automation technology and was first promoted by BMBF (German Department of Education and Research) and was later used by Siemens. Twisted pair cables or fibre cables are used as physical media and bus type topology is used.

PROFIBUS Protocol(OSI reference Model)

OSI Layers:1. Physical Layer2. Data link3. Network4. Transport5. Session6. Presentation7. Application

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To utilise these functions, various service levels of the DP protocol were defined:

DP-V0 for cyclic exchange of data and diagnosis DP-V1 for acyclic exchange of data and alarm handling DP-V2 for isochronous mode and data exchange broadcast (slave-to-

slave communication)

Security LayerThe security layer FDL (Field bus Data Link) works with a hybrid access method that combines token passing with a master-slave method. In a PROFIBUS DP network, the controllers or process control systems are the masters and the sensors and actuators are the slaves. Various telegram types are used. They can be differentiated by their start delimiter (SD):

No data: SD1 = 0x10

SD1 DA SA FC FCS ED

Variable length data: SD2 = 0x68

SD2 LE LEr SD2 DA SA FC DSAP SSAP

PDU FCS ED

Fixed length data: SD3 = 0xA2

SD3 DA SA FC PDU FCS ED

Token: SD4 = 0xDC

SD4 DA SA ED

Brief acknowledgement: SC = 0xE5

SC

SD: Start Delimiter

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LE: Length of protocol data unit, (incl. DA, SA, FC, DSAP, SSAP)

LEr: Repetition of protocol data unit, (Hamming distance = 4)

FC: Function Code

DA: Destination Address

SA: Source Address

DSAP: Destination Service Access Point

SSAP: Source Service Access Point

SAP (Decimal) SERVICE

Default 0 Cyclical Data Exchange (Write_Read_Data)

54 Master-to-Master SAP (M-M Communication)

55 Master-to-Master SAP (M-M Communication)

56 Read Inputs (Rd_Inp)

57 Read Outputs(Rd_Outp)

58 Control Commands to a DP Slave (Global_Control)

59 Read Configuration Data (Get_Cfg)

60 Read Diagnostic Data (Slave_Diagnosis)

61 Send Parameterization Data (Set_Prm)

62 Check Configuration Data (Chk_Cfg)

Note: SAP55 is optional and may be disabled if the slave doesn't provide non-volatile storage memory for the station address.

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PDU: Protocol Data Unit (protocol data)

FCS: Frame Checking Sequence

ED: End Delimiter (= 0x16!)

The FCS is calculated by simply adding up the bytes within the specified length. An overflow is ignored here. Each byte is saved with an even parity and transferred asynchronously with a start and stop bit. There may not be a pause between a stop bit and the following start bit when the bytes of a telegram are transmitted. The master signals the start of a new telegram with a SYN pause of at least 33 bits (logical "1" = bus idle).

PLC Panel

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Introducing the S7-200 Micro PLCThe S7-200 series is a line of micro-programmable logic controllers (Micro PLCs) that can control a variety of automation applications. Figure 1-1 shows an S7-200 Micro PLC. The compact design, expandability, low cost, and powerful instruction set of the S7-200 Micro PLC make a perfect solution for controlling small applications. In addition, the wide variety of CPU sizes and voltages provides you with the flexibility you need to solve your automation problems. Advantages

Smaller physical size than hard-wire solutions. Easier and faster to make changes. PLCs have integrated diagnostics and override functions. Diagnostics are centrally available. Applications can be immediately documented. Applications can be duplicated faster and less expensively.

Ladder Logic

Elements

Symbols Meaning

-| |- Normally open contact

-| \ |- Normally closed contact

-|P|- Positive Transition contact

-|N|- Negative Transition contact

-( )- Normal Coil

-(L)- Latched Coil

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POWER DISTRIBUTION

Incoming supply line from the State Electricity Board is 33kv. At UCL, there are two substations:

i) At the main substation 3000kVA x 3 transformers are installed.ii) At the VCV Line substation 2000kVA x 2 transformers are installed.

Incoming for main substation and VCV substation is 33kV and output of main substation and VCV substation is 415V 3-Phase + N

Captive PowerAt the power house following DG (Diesel Generator) sets are installed.i) 500kVA x 6 (DG sets are installed)ii) 1550kVA x 2 (DG sets are installed)iii) 2100kVA x 1 (DG sets are installed)

Total captive power = 8200kVA or 8.2MVA

State Electricity Supply Voltage power = 33kV Contract Demand = 4000kVA Maximum Demand = 3600kVA (M.D. is always 10% less than the C.D.)

3-phase Distribution

Primary

Voltage between:

R-Y, Y-B, R-B= 33kV

Current (I)= 87Amp

Secondary

Voltage between:

R’-Y’, Y’-B’, B’-R’ =Vph/√3=415V

Voltage between:

R’-N, Y’-N, B’-N= 230V

Current (I’)= 7000Amp

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TELEPHONE EXCHANGE SYSTEM

Telephone exchange system at UCL is based on the Time Division Multiple Access (TDMA). Time division multiple access (TDMA) is a channel access method for shared medium networks. It allows several users to share the same frequency channel by dividing the signal into different time slots. The users transmit in rapid succession, one after the other, each using its own time slot. This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity. TDMA is used in the digital 2G cellular systems such as Global System for Mobile Communications (GSM), IS-136, Personal Digital Cellular (PDC) and iDEN, and in the Digital Enhanced Cordless Telecommunications (DECT) standard for portable phones. It is also used extensively in satellite systems, combat-net radio systems, and PON networks for upstream traffic from premises to the operator.

TDMA is a type of Time-division multiplexing, with the special point that instead of having one transmitter connected to one receiver, there are multiple transmitters. In the case of the uplink from a mobile phone to a base station this becomes particularly difficult because the mobile phone can move around and vary the timing advance required to make its transmission match the gap in transmission from its peers.

Siemens make High IP Ready 4300 EPABX (Electronic Private Automatic Branch Exchange) system is installed at the telephone exchange supported by PIR cards of 30 channels with 2Mbs speed. Two analog trunk extensions are used. LTUCX is used for interconnecting different stages of EPABX. Digital enhanced cordless telephone is used with the help of DECT cards, which are connected to EPABX connected to the trans-receiver base station.

EPABX

EPABX: These are solid state digital systems.EPABX mainly have the following features:

Establishing connections (circuits) between the telephone sets of two users (e.g. mapping a dialed number to a physical phone, ensuring the phone isn't already busy)

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Maintaining such connections as long as the users require them (i.e. channeling voice signals between the users)

Disconnecting those connections as per the user's requirement Providing information for accounting purposes (e.g. metering calls) Time and attendance or Workforce Management clocks: we have many

varieties of clocks that suit every customer like electronic tags, barcode badges, magnetic stripe cards, (hand, fingerprint, or facial), and touch screens. We also have electrical time recorders, digital keyboard time recorders and industrial time recorders.

Online/Offline UPS: We have different UPS units either to protect a single computer or to large units powering entire data centers, buildings etc. Offline UPS offers surge protection and battery backup. Typical protection time is 20 minutes and the switchover time is just 25 milliseconds. The Online UPS units provide 5–30 minutes of protection time and the capacity expansion is for several hours. We have units ranging from 500 watts or less to 10 kW.

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References

The report has been made referring the information from various sources and explanatory notes.

Internet sources like wikipedia.com and google.com were also referred for the same.

Various materials available in the Instrumentation department were also taken for reference work.

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