14-09-2012, 01:58 PM
STUDY OF PROTECTIONS OF 60 MW TURBO-GENERATORS OF CAPTIVE POWER PLANT IN VSP
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ABSTRACT
This project titled “STUDY OF PROTECTIONS OF 60 MW TURBO-GENERATORS OF CAPTIVE POWER PLANT IN VSP” covers the complete electric protections of Turbo generator in a Thermal Power Plant of Visakhapatnam Steel Plant. The main objective of the project is to study the various protections provided for the alternator and the necessity of each.
The study also covers verification of the existing settings used for different protective relays by actually calculating the fault currents under various conditions.
Normally the faults in Generator can occur either inside like stator, rotor or external to it in the bus-ducts of feeders. While internal faults in a generator should be cleaned as fast as possible to minimise the damage of the core where as the external faults should be sustained for a considerable period to enable the respective down-stream protections to act and isolate the same from the generator. In case of downstream protections not clear a fault, a backup is to be provided in generator scheme to isolate the same. Proper coordination between these protections are also to be verified.
INTRODUCTION
An electrical power system should ensure the availability of electrical energy without interruption to every load connected to the system. Among all the systems, electrical energy is quite transferable to the consumers by transmission and distribution systems. The power supply to the consumer should not disturbed and the agencies which supplies the power without interruption. As industrial processes and plants have become more complex and extensive, the demand for improved reliability of electrical power supplies has also increased. The potential costs of outage time following a failure of the power supply or plant have accordingly risen dramatically as well. If at all any fault happens in the system the fault system has to be isolated so that other system should not be disturbed. This is a challenge to the engineers to supply the uninterrupted power to the customers. To attain this, logical and fast acting protective equipment is required.
INTRODUCTION TO VSP
Steel comprises one of the most important inputs in all sectors of economy. Steel industry is both a basic and a core industry. The economy of any nation depends on a strong base of Iron and steel industry in that country. History has shown that countries having a strong potentiality of Iron and Steel Production have played a prominent role in the advancement of civilisation in the world. Steel is such a versatile commodity that every object we see in our day to day life has used steel either directly or indirectly. To mention few it is used for such a small item as nails, pins, needles etc. through surgical instruments, agricultural implements, boilers, ships, railway materials, automobile part etc., to heavy machines, structures etc. The great investment that has gone into fundamental research in Iron and steel technology has helped both directly and indirectly many modern fields of today’s science and technology. It would seen very painful to image the fate today’s civilisation had steel not been there.
BACKGROUND
The decision of Government of India to set up an integrated steel plant at Visakhapatnam was announced by the then Prime Minister Smt. Indira Gandhi in the Parliament on 17th April 1970. Visakhapatnam Steel Plant (VSP), a public sector undertaking, is a subsidiary of Rashtriya Ispat Nigam Limited. It is one of the most sophisticated modern plants. The foundation stone for which was laid by the former Prime Minister Smt. Indira Gandhi in the year 1972. It is strategically located on the coast of Bay of Bengal in the state of Andhra Pradesh. An integrated steel plant with the state-of-the-art technology. Overcoming the perils of recession in the steel market it has turned into a profit making organization with proper strategic decisions. The management of late has been geared up to implement new technologies to meet the challenges of completion and the dumping imports of steel. Visakhapatnam is in a geographically advantageous position. Midway between Kolkata and Chennai. It is easily accessible to major business centers.
TURBO BLOWERS
VSP has 2 Blast Furnaces. To meet the blast air requirement, 3 Turbo Blowers, each of 6067 NM3 /min capacity, are installed at TPP. These blowers are of axial type and are the largest blowers installed in India. The blowers are provided with suction filters, pre-coolers and inter- coolers.
AUXILIARIES OF TPP
These include coal conveyors, cooling towers & pump house No-4 for cooling water system, pump house for ash water, ash slurry , fire water and fuel oil & HSD air compressor station, emergency Diesel Generators, electric switch gear for power distribution, ventilation and air conditioning equipment etc. The entire power generated at Back Pressure Turbine Station and Gas Expansion Turbine Station is transmitted over 11 kV cables to power plant, stepped up through a 220 kV transformer at LBSS5 and transferred to plant grid.
CHEMICAL WATER TREATMENT PLANT
Chemical Water Treatment Plant located in TPP zone produces high purity De-mineralised Water and Soft Water. There are six streams of De-mineralising units each capable of producing 125 cubic meters per hour each. Two softening units of 125 m3/hr. each. DM water is supplied to TPP, Steel Melt Shop, CDCP Boilers at Coke Ovens, and Rolling Mills. Soft water is supplied to Chilled water plant-I, II and SMS mould cooling.
CHILLED WATER PLANT NO-2
Chilled Water Plant No-2 located in TPP zone is having nine Chillers, each having a chilling capacity of 337 M3/hr. The chilled water is supplied to TPP, Blast Furnace and Sinter Plant for air conditioning purpose at 70 C. The return water temperature is 160 C.
COKE DRY COOLING PLANT (CDCP) BOILERS
In VSP, hot coke produced in the Coke Oven Batteries is cooled by circulating Nitrogen in Coke Dry Cooling Plant. The hot circulating gas is passed through Waste Heat Boilers in which steam is produced at 40 KSCA pressure and 4400 C temperature. There are three Coke Dry Cooling Plants, four Waste Heat Boilers. Boiler is of 25 T/Hr Capacity.
BPTS & CHILLED WATER PLANT NO-1
The 40 KSCA steam generated in CDCP Boilers is utilised for driving 2 Nos. of 7.5 MW Back Pressure Turbines for generation of Power. The 2.5 Ata exhaust steam is utilised for production of Chilled water in CWP-1. The 7 Ata extraction steam is used for process requirements of CO & CCP zone . The CWP-1 has 5 Chillers installed, each capable of cooling 337 M3/hour BPTS and CWP-1 are housed in a single located near Battery No-3 of CO&CCP zone.
GAS EXPANSION TURBINE STATION (GETS)
Both the Blast Furnace of VSP are designed to operate at a high top pressure of 2.5 Kg/cm2. The high pressure BF Gas is cleaned in Gas cleaning plant and expanded in Gas Expansion Turbines driving electric generators. The BF Gas after passing through the Turbine is fed to gas distribution net work and is used as heating fuel in TPP & other units of VSP. Each Blast Furnace is connected to a Gas Expansion Turbine of 12 MW capacity 7.5 MW of power is generated by each of the turbine at full production level. GETS is located in BF zone, between the two furnaces.