electrical mant. of esp

7/30/2019 Electrical Mant. of Esp

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PRESENTED BYSAYANTAN JANAB.E (ELECTRICALENGG.)


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CONTENT:

1.BASIC PRINCIPLE OF ESP2.HVTR(HIGH VOLTAGE TRANSFORMER RECTIFIER)3.ELECTRONIC REGULATOR

4.RAPPING MOTORS5.INSULATORS6.MAINTENANCE DURING SHUTDOWN


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What is an ESP???An electrostatic precipitator (ESP), orelectrostatic air cleaner is a particulatecollection device that removes particles from a

flowing gas (such as air) using the force of aninduced electrostatic charge.

Electrostatic precipitators are highly efficient

filtration devices that minimally impede the flowof gases through the device, and can easily removefine particulate matter such as dust and smokefrom the air stream.


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Principle behind ESP

Precipitators function by electro statically chargingthe dust particles in the gas stream. The chargedparticles are then attracted to and deposited onplates or other collection devices. When enough dust

has accumulated, the collectors are shaken todislodge the dust, causing it to fall with the force ofgravity to hoppers below. The dust is then removed

by a conveyor system for disposal or recycling.


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Negative Corona-

+

- +

- +

-

-

-

+

+

Corona Discharge

Step 1

Step 2

Step 3

Step 4

Collection Plate

Electron

Molecule

Particle

Electrode

Q: How can we generate charges?


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Six activities typically take place:

Ionization - Charging of particles

Migration - Transporting the charged particles to the collectingsurfaces

Collection - Precipitation of the charged particles onto thecollecting surfaces

Charge Dissipation - Neutralizing the charged particles on thecollecting surfaces

Particle Dislodging - Removing the particles from the collectingsurface to the hopper

Particle Removal - Conveying the particles from the hopper to adisposal point


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Most Basic-The Plate Precipitator

The most basic precipitator contains arow of thin wires, and followed by astack of large flat metal plates, with theplates typically spaced about 1 cm apart.

If the applied voltage is high enough anelectric discharge ionizes the air aroundthe electrodes. Negative ions flow to theplates and charge the gas-flow particles.

The ionized particles, following thenegative electric field created by thepower supply, move to the groundedplates.


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ComponentsThe major precipitator components that accomplishthese activities are as follows

Discharge Electrodes

Collecting plates

Power Supply and controls

Rapping Systems Hoppers and Dust Handling


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Discharge Electrodes - Discharge electrodes emit charging

current and provide voltage that generates an electrical fieldbetween the discharge electrodes and the collecting plates

Power supply and controls - The power supply system isdesigned to provide voltage to the electrical field (or bus section)

at the highest possible level.

Rapping Systems - Rappers are time-controlled systemsprovided for removing dust from the collecting plates and the

discharge electrodes

Hoppers and Dust Handling - Precipitator hoppers aredesigned to completely discharge dust load on demand.


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HIGH VOLTAGE TRANSFORMER RECTIFIER


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The HVTR unit consists of :Primary voltage:415 V ,AC voltage

full wave rectified bridgeTank filled with insulating oil

Limiting linear reactor connected in series with primary winding

(to limit the short circuit current during sparking inside ESP to a safe value)

HF chock connected tove terminal of rectifier

(to protect the transformer from surges)

A high voltage feedback element mounted on transformer tank

HVTR is fitted with following accessories:

Bucoltz relay

Oil temperature indicator

A high voltage DC(-ve)bushing with provision of bus duct connection

Conservator with oil level indicator


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ELECTRONIC CONTROLLER:

The electronic controller unit feeding regulated i/p to HVTR is a

micro processed based controller .Objective:The automatic voltage control system operate so as to maintainconstant current from transformer under dynamic conditions ofESP loadThe controller controls the precipitator power by changing the

firing angle of thyristors connected to primary of transformer.

Salient features of controller:Spark regulation: Digital detection and control philosophy offlashover enabling sensing of pits, sparks and arcs by comparingsamples of KV signals in a half wave.

Energy saving feature based on 'VI' characteristicsCharge ratio (pulsed operation) with a higher range up to 1:255for improving precipitation and/or for energy saving dependingupon the type of process, dust resistivity etc.


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Fault indications:

Under voltage(o/p KV)Over voltage(o/p KV)Ac current high(i/p)OverloadSingle SCR firingSCR Temp high

TX oil temp high alarmTX oil temp high tripTOP floatBottom float


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Heating elements:

Mineral filled tubular type heating elements are provided on outsidehopper walls.

The heating elements are suitable for 415v, 50HZ supplyGrouped to form delta using field mounted junction boxes.The configuration of heating element differ to suit the requirement ofshaft insulator, support insulators And hopper heaters.

GEARED MOTOR S FOR RAPPING MECHANISM:

Each collecting &emitting system is provided with one geared motor unitcoupled to rapper shaft & located outside casing

The geared motor consists of Helical reduction gear with an integralDOL start squirrel cage induction motor as prime mover.


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INSULATORS:

1. Each section consists of four support insulators forsupporting the emitting system. These insulatorsare located inside individual housing mounted onthe roof of ESP.

2. Shaft insulator is provide to isolate each gearedmotor assembly from associated emitting rappingshaft

3. One bushing insulator is provide corresponding toeach field and is mounted in the insulator bushing.

4. The insulators are of high quality porcelaindesigned to with stand the operating temp &

voltage.


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Cause of poor performance:

The performance of ESP is evaluated by voltage & current readings .The voltage current level of ESP may be low because of:

High ash deposit on emitting/collecting electrodes

Poor alignment of emitting/ collecting electrode s

Heavy sparking caused by high resistivity dust.


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ELECTRICAL MAINTANCE ON LONG OVERHAULING OF UNIT:

1.Shutdown of MCC of ESP: Isolate the power Earth switches made on All manhole are to be earthed.

2. Maintenance of HVTR:The external body cleaned by rubbing the deposits of dustAll bus ducts are to be cleanedThe silica gel are to be replaced or regenerated if it is blueThe level of conservator is to be marked & If it is less then 40% thefresh filtered transformer oil to be pouredBDV testing of oil sample is to be done .( if it is less than 30KV theoils of transformer needs filtration)

The DGA ( dissolved gas analysis) test of oil is carried out t check thehealthiness of transformer

3. Maintenance of HOPPER HEATERS4. Maintenance of INSULATORS


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CONCLUSION:

ESP is one of the equipments, which has veryfew moving rotating parts and hence needs

minimum maintenance.Still proper maintenance & regularmonitoring will improve the performance ofESP.


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electrical mant. of esp

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