DADI INSTITUTE OF ENGINEERING & TECHNOLOGY

A STUDY ON PROTECTIONS OF 60MW TURBO GENERATORS OF CAPTIVE POWER PLANT IN VSP

Internal Guide

Mr. MANOFAR ALI,

Assistant Professor

EEE DEPARTMENT

SUBMITED BY

K.SIVA GOVINDARAO (09U41AO264)

L.THARUN KUMAR (09U41A0272)

M.CHAITANYA DEEPTHI (09U41A0277)

A.AJAY KRISHNA (09U41A0248)

ABSTRACT

This project 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. Normally the faults in Generator can occur either inside like stator, rotor or external to it in the bus-ducts of feeders.

INTRODUCTION TO VSP Steel industry is both a basic and a core industry. 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 plant is designed to produce 3.0 Million tones of liquid steel. It possesses thestate-of-the-art technology and a strong well trained manpower of 17,000 employees.Nearly 40% of the South Indian domestic market has been captured for the steel products. International customers are from the countries of China, Singapore, Russia, Nepal, Sri Lanka, USA, Japan, UAE etc.

ACHIEVEMENT AND AWARDS

Indira Priya Darshini Vrikshamitra for massive afforestation efforts of RINL : 1992-93. Award from Ministry of heavy industries for achieving MoU targets for 2000-01. National Energy conservation award-2002 -- First Prize in Integrated sector. Certificate of appreciation for achieving OHSAS 18001 from department of Factories, Govt. of Andhra Pradesh.

INTRODUCTION TO TPP Power requirement of VSP is met through captive generation as well as

supply from ABSEB grid. The captive capacity of 270 MW is sufficient to meet all the plant needs in normal operation time we have 3 units of each 60 MW and one unit of 67.5 MW capacity.

BOILERS:

Thermal Power Plant has 5 Boilers each of 330 T/hr. steam capacity at 101 KSCA and 540O C.

The boilers are of BHEL make, capable of firing combination of fuels namely, Coal, Coke Oven Gas, Blast Furnace Gas and Oil

Thermal Power Plant has 4 Turbo Generators, three of 60 MW capacity each and the fourth 67.5 MW

CHEMICAL WATER TREATMENT PLANT

TURBO GENERATORS

Chemical Water Treatment Plant located in TPP zone produces high purity De-mineralised Water and Soft Water.

CHILLED WATER PLANT

The chilled water is supplied to TPP, Blast Furnace and Sinter Plant for air conditioning purpose

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.

ISLAND OPERATION SCHEME A scheme has been envisaged at TPP to get isolated form the grid in case of system disturbance or low frequency condition with ABB make relay type FCX 103b relay with following settings:

POWER REQUIREMENT

Integrated Steel Plants are major consumers of electricity, with specific consumption of power at around 600-650 kWh/Ton of liquid steel.

POWER DISTRIBUTION IN POWER PLANTIntegrated Steel Plants are major consumers of electricity, with specific consumption of power at around 600-650 kWh/Ton of liquid steel. The estimated annual power requirement of Visakhapatnam Steel Plant, at full level of production in each shop (corresponding to 3.0 MT of liquid steel), is 1932 million kWh. Power requirement of VSP is met through captive generation as well as supply from AP TRANSCO grid. The captive capacity of 270 MW is sufficient to meet all the plant needs in normal operation time.

SYNCHRONISATION

The operation of connecting an alternator in parallel with another alternator or with common bus-bars is kwon as Synchronizing. Generally, alternators are used in a power system where they are in parallel with many other alternators. It means that the alternator is connected to a live system of constant voltage and constant frequency.

THEORETICAL REVIEW OF RELAYS

TYPES OF PROTECTIONSTwo types of protection:

 1. Primary protection2. Backup protection

Primary protection

Primary protection is the first line of defence and primary relays clear faults in the protected section as fast as possible.

 

Backup protection

Backup relays operate if the primary relays fail and cover not only the local station but the next one also and have a time delay long enough for the primary relays to operate if they can.

ELECTROMAGNETIC RELAYS

These are earliest form of relays devices used for power system protection and till now they are the most widely used variety relays.

ATTRACTED ARMATURE TYPE  

The type includes plunger, hinged armature relays. These are the simplest type which respond to AC as well as DC. The electromagnetic force is given by F = KI2

INDUCTION RELAYS

Induction type relays are the most widely used for protective relaying purposed involving A.C. quantities. The Actuating force is given by F = K 1 2 Sin

GENERATOR DIFFERENTIAL RELAY

A differential relay is defined as the relay that operates when the vector difference of two or more similar electrical quantities exceeds a predetermined value.

External & Internal circuit connections of generator

differential relay

GENERATOR RESTRICTED EARTH FAULT RELAY

In circulating current protection schemes, the sudden and often asymmetrical growth of the system current during external fault conditions can cause the protective current transformers to go into saturation resulting in a high unbalance current.

External & Internal circuit connections of generator

stator earth fault relay

GENERATOR VOLTAGE RESTRAINED OVER CURRENT RELAY

 

Fault conditions cause a greater drop in bus bar voltage than normal over load, and this fact has been utilised in voltage restrained over current relay. An over load characteristics determine by the operation of instantaneous under voltage unit monitoring the generator voltage.

External and internal connections of Voltage restrained over current relay

GENERATOR VOLTAGE RESTRAINED OVER CURRENT RELAY

 

Fault conditions cause a greater drop in bus bar voltage than normal over load, and this fact has been utilised in voltage restrained over current relay. An over load characteristics determine by the operation of instantaneous under voltage unit monitoring the generator voltage.

External and internal connections of Voltage restrained over current relay

Time / current characteristics of Voltage restrained over current relay

GENERATOR DIRECTIONAL OVER CURRENT RELAY

When fault current can flow in both directions through the relay location, it is necessary to make the response of the relay directional by the introduction of directional control elements.

GENERATOR DIRECTIONAL OVER CURRENT RELAY

GENERAL FIELD FAILURE RELAY

Under current relays connected in the field circuit have been extensively but the most selective type of loss-excitation relay is a directional-distance type operating from the A.C. current and voltage at the main generator field.

General field failure relay

EARTH FAULT PROTECTION

A single earth fault is not in itself dangerous since it does not cause any fault current, but a second fault effectively short circuits or all parts of the field system and the unbalancing of the magnetic force caused there by may be sufficient to spring the shaft and make it eccentric.

Earth fault relay 

GENERATOR DIRECTIONAL EARTH FAULT RELAY

The relay is used for directional earth fault protection for generator. Typical external and internal connection. Since the current may be derived from any phase, in order to obtain directional response it is necessary to obtain a related voltage. Such a voltage is the residual voltage of the system.

ROTOR EARTH FAULT RELAY

When a single earth fault is detected in the d.c field circuit of a Machine, the Machine has to be taken out of service at the first opportunity.

PROTECTION AGAINEST PRIME MOVER FAILURE

The effect of prime mover failure is to cause the machine to motor by taking power from the system which may result in severe mechanical damage and, in addition will impose a heavy motoring load on the generator.

GENERATOR SENSITIVE EARTH FAULT PROTECTION

This protection is especially provided in the generator to sense any earth leakage near to the neutral. Question may come why separate earth fault relays is used. Reason is that other earth fault relay senses earth current of higher magnitude.

GENERATOR OUT OF STEP RELAY

A CAG 19 relay serves as an over current starter and this is set at between 50 and 20% of nominal current. Based on 5 A CTs below the current no operation can occur. Both character look into the source and consequently ignore all conditions of load other than those which produce a reversal of power flow such as would occur with a condition of pole slip or power swing exceeding 90O.

CONCLUSION

The purpose of protection system is to monitor the unwanted conditions and when such conditions arise, to remove the fault in the shortest time possible, leaving unaffected are operational.

In this project we have studied the protection provided to 60 MW Turbo generator in Thermal Power Plant of Visakhapatnam Steel Plant. In this we have studied both symmetrical and unsymmetrical faults and response of different relays for these faults with the existing settings.

ANY QUERIES

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THANK YOU…