01-08-2014, 12:45 PM
STUDY OF 400KV SWITCHYARD & PROTECTION
STUDY OF 400KV SWITCHYARD.docx (Size: 1.1 MB / Downloads: 58)
ABSTRACT
This is a project about protection of 400kv switchyard in power plant for economical transmission of power to various loads centers by using protective devices like circuit breakers, isolators, earth switch, relays, Computer-based SCADA system (for control, metering and synchronizing) ,capacitive voltage transformers etc...
Protective relays are the decision –making elements in the protection scheme for electrical power systems. They monitor circuit condition and initiate protective action when an undesired condition is detected. Protective relays work in concert with sensing and control devices to accomplish their function. Under normal power system operation, a protective relay remains idle and serves no active function. However , when required to operate because of fault or undesirable condition, the relay function correctly.
INTRODUCTION TO KTPP-BHUPALPALLY:
• The govt of AP accorded approval on FEB 28th 2005 for setting of 1*500MW thermal project at bhupalpally dated 28-02-2005
• Fuel supply agreement was entered with SCCL on 31st march 2005 for supply of 2.16 mtpa of coal from bhupalpally mines of SCCL
• The government of AP have allotted one(1) TMC water from Godavari at kaleswaram near metpalli village
• Detailed purchase order for supply of material was issued on BHEL on 04-08-2005 for an amount of Rs 964.222 Cr
BIOLER:
The boiler is a rectangular furnace about 50 feet (15 m) on a side and 130 feet (40 m) tall. Its walls are made of a web of high pressure steel tubes about 2.3 inches (58 mm) in diameter.
Pulverized coal is air-blown into the furnace through burners located at the four corners, or along one wall, or two opposite walls, and it is ignited to rapidly burn, forming a large fireball at the center.
The thermal radiation of the fireball heats the water that circulates through the boiler tubes near the boiler perimeter.
The water circulation rate in the boiler is three to four times the throughput. As the water in the boiler circulates it absorbs heat and changes into steam. It is separated from the water inside a drum at the top of the furnace.
SUPER HEATER:
Fossil fuel power plants often have a super heater section in the steam generating furnace. The steam passes through drying equipment inside the steam drum on to the superheated, a set of tubes in the furnace.
The saturated steam at boiler is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace. Here the steam is superheated to 1,000 °F (540 °C) to prepare it for the turbine.
Here the steam picks up more energy from hot flue gases outside the tubing and its temperature is now superheated above the saturation temperature. The superheated steam is then piped through the main steam lines to the valves before the high pressure turbine.
REHEATER:
Power plant furnaces may have a reheater section containing tubes heated by hot flue gases outside the tubes. Exhaust steam from the high pressure turbine is passed through these heated tubes to collect more energy before driving the intermediate and then low pressure turbines
ECONOMISER:
The water enters the boiler through a section in the convection pass called the economizer. From the economizer it passes to the steam drum and from there it goes through down comers to inlet headers at the bottom of the water walls.
CONDENSOR:
The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be pumped. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and efficiency of the cycle increases.
COOLING TOWER:
The condenser generally uses either circulating cooling water from a cooling tower to reject waste heat to the atmosphere, or once-through water from a river, lake or ocean
The heat absorbed by the circulating cooling water in the condenser tubes must also be removed to maintain the ability of the water to cool as it circulates. This is done by pumping the warm water from the condenser through either natural draft, forced draft or induced draft cooling towers (as seen in the image to the right) that reduce the temperature of the water by evaporation, by about 11 to 17 °C (20 to 30 °F)—expelling waste heat to the atmosphere. The circulation flow rate of the cooling water in a 500 MW unit is about 14.2 m³/s (500 ft³/s or 225,000 US gal/min) at full load.
The condenser tubes are made of brass or stainless steel
The cooling water used to condense the steam in the condenser returns to its source without having been changed other than having been warmed. If the water returns to a local water body (rather than a circulating cooling tower), it is tempered with cool 'raw' water to prevent thermal shock when discharged into that body of water.
INTRODUCTION:
A 400kV switchyard shall be provided for evacuation of power generated in the plant through two (2) double circuit 400kV transmission lines to Warangal & Gajwel.
Introduction:
The over current protection required for transformers is consider for Protection of Transformer only. Such over current protection will not necessarily protect the primary or secondary conductors or equipment connected on the secondary side of the transformer.
When voltage is switched on to energize a transformer, the transformer core normally saturates.This results in a large inrush current which is greatest during the first half cycle (approximately 0.01 second) and becomes progressively less severe over the next several cycles (approximately 1 second) until the transformer reaches its normal magnetizing current.
To accommodate this inrush current, fuses are often selected which have time-current withstand values of at least 12 times transformer primary rated current for 0.1 second and 25 times for 0.01 second. Some small dry-type transformers may have substantially greater inrush currents.
To avoid using over sized conductors, overcurrent devices should be selected at about 110 to 125 percent of the transformer full-load current rating. And when using such smaller overcurrent protection, devices should be of the time-delay type (on the primary side) to compensate for inrush currents which reach 8 to 10 times the full-load primary current of the transformer for about 0.1 s when energized initially.
Protection of secondary conductors has to be provided completely separately from any primary-side protection.
A supervised location is a location where conditions of maintenance and supervision ensure that only qualified persons will monitor and service the transformer installation. Overcurrent protection for a transformer on the primary side is typically a circuit breaker. In some instances where there is not a high voltage panel, there is a fused disconnect instead.
It is important to note that the overcurrent device on the primary side must be sized based on the transformer KVA rating and not sized based on the secondary load to the transformer.