Sub Station Training Program

VESTAS INDIA

TWO DAYS AGENDA TO VESTAS ENGINEERS

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SAFETY MANAGEMENT IN DISTRIBUTION AREA

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Unsafe Action By Personnel Causing Accidents

• Carelessness in job.• Half knowledge (half-baked) of work• Tension (Anger) on duty• Ineffective supervision• Absence of supervision• Non-planning before commencing work• Non-cooperation bet personal• “I know it all” Attitude (Ego)

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General Cause Of Accident

• Unsafe action of personnel

• Unsafe status in distribution

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Unsafe status in distribution

• Snapping of conductor.• Stay w/o guy shackle becomes live.• Steel pole w/o proper earthing.• Damaged pole falling down• Inadequate ground clearance• Leaning poles

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Reason for snapping of conductor

• Line with copper connected to Aluminum conductor • Due to falling of trees• L.T.Shackle without metal parts

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Unsafe Action By Personnel Causing Accidents

• Non- adoption of safety procedures• Not exercising with the safety device- gloves, Earth

rod, Waist-belt etc.• Over confidence• Drunkenness on duty• Performing work in disturbed mind• Hurry in finishing job• Ignorance (unawareness) of work

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OPERATION OF FIRE EXTINGUISHERS

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SODA ACID (9L)

The extinguishers should be taken within 1M offire. After taking out the safety cup, the extinguisher should be held and plunger struck against a hard surface. Now the acid bottle will get broken and acid on mixing with solution will evolve carboridioxide gas. The gas pressure will expel water when cylinder kept inverted. The expelled water should be directed to the base of the fire. Upright type; as having discharge tube inside from nozzle to bottom, should not be used in inverted position.

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FOAM TYPE (9L)

The knob should be pulled up, turned clockwise and pin seated on the groove. This will keep the port of inner container open and when the-cylinder kept inverted the two solutions mix together forming foam. The evolved CO2 gas will expel the foam. The foam has to be directed on to the fire without force to cover as a blanket covering the fire. This prevents entry of oxygen thereby extinguishing fire. For effective formation of foam the cylinder may be alternatively kept shaking upright and inverted quickly 2 to 3 times.

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DRY CHEMICAL POWDER (DCP)

Remove the safety clip and strike the plunger. The pin in the plunger will puncture the seal of the co2 cartridge and the gas coming out with pressure will stir the powder and expel the powder. The powder coming out through the hose should be directed on to the fire show as to cover the fire as a blanket and extinguish the fire.

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CARBONDIOXIDE CYLINDER

The extinguisher should be taken every close to the fire. After opening the cylinder value, the gas coming thro the hose and can may be directed on to the fire. The gas coming out through the hose will expand and cover the fire as a shroud and extinguish the fire.

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General Precautions

1. The lids of all extinguishers should be checked for tightness. If two or more threads are exposed out that cylinder should not be used. The high pressure developed in the cylinder could be withstood only if the lid is completely screwed on to the body. Other wise the lid would come out as a blast and cause serious injury to the operator.

2. All extinguishers should be used in the direction of the wind.

3. There are three pin holes on the periphery of the lid. When there is any block in the cylinder. Nozzle or hose the contents will not come out while using. Then the cylinder lid may be unscrewed very slowly. When the holes come up, the pressurized gases will come out thro’ these holes. Only after the gas completely goes out. The lid can be fully opened. On no account we should think that there is no pressure inside the cylinder, if contents do not come out during usage.

4. whenever newly filled, the gas cartridge and CO2 cylinder should be checked for its correct weight.

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MAINTENANCE OF EXTINGUISHER

• Monthly cleaning and checking for nozzle block and lid tightness.

• Quarterly open the lid. Check for free 11; movement of plunger. Clean the outside of the inner container.

• In foam type the solution should be poured separately in utensils and stirred. Few drops may be taken out separately and mixed together for checking proper formation of white colored foam.

• Once in 6 months the gas cartridge should be checked for weight. If there is more than 10% loss in weight of gas, the cylinder may be used in fire mock drill antler refilled.

• Once in two years the cylinder should be checked for pressure test. Soda acid and foam type should withstand pressure of 17.5 Kg/Sq.cm. for 2.5 minutes.

• All fire extinguishers should be checked for healthiness Once in a year.

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Introduction to Substation and equipments

• In Power System network, in order to transmit and distribute the generated power, it is necessary to install “SUBSTATIONS” at strategic points to work at required voltage level since “HIGH VOLTAGE TRANSMISSION” is resorted to. The Sub stations are classified as “GRID” or “RADIAL” Substations. The Grid station is installed in Grid network to reduce the voltage level from 230KV to 110 KV. The radial Station with in Distribution net work to reduce the voltage from 110 KV to 11KV or 22KV or 33KV).

• In essence the substation provides • (a) Transfer of voltage level • (b) Transmission of the required Power and • (c) Adjustment of voltage variations caused by the system

voltage regulation.

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110/11KV SUB STATION : CLASSIFICATION OF EQUIPMENTS

• Sl. No Classification Equipments Purpose • 1. Functional • a) Bus Bar • b) Transformers • c) Earthing System To carry Power feeding To

transmit Power from one voltage to other To ensure effective grounding for safety & Protective operation.

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• 2. Isolation & Control • a) Isolation • b) Breakers Isolate feeding equipments from source

of supply (Potential ) Breaking the Current (Power flow) for normal maintenance; and for isolation of faulty section)

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• 3. Protection from internal disturbances • a) Earth Mast • b) Surge Diverter • c) ROD GAP To prevent damage to equipment from

direct stroke of lightning. Protecting the transformer from the impact of surges. Back up Protection for Surge Diverters.

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• 4. Protection & Metering • a) Potential Transformer (PT) • b) Current Transformer (CT) • c) Relays Metering (Voltage and Energy) Metering

(Current & Energy) Protection For sensing the fault and give command to breakers to isolate the faulty circuit. For

• i) Indication of Status • ii) Annunciation of the fault • iii) Operation of breaker for isolation of faulty

circuit.

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5. A.C.System for LT 3phase, 400V supply a) Station Transformer 11KV/400V. b) b) A.C.Panel To feed L.T-3Ph. 400V Supply for c) i) Auxiliaries of breakers & Transformers. d) ii) Yard & Control room lighting e) iii) Supply to battery charge Control of A.C.Supply

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6. Housing a) Yard & Structures b) Control room To house equipments with required

horizontal and vertical clearances. To house indoor equipments like D.C. System, D.C. & A.C. panels etc.,

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LAYOUT OF SUBSTATION

• A single line diagram called the Schematic layout of Sub-Station should be available, showing the arrangement of the above equipments.

• A typical layout of a 230 / 110KV Grid station and that a 110/11KV Radial station are shown in Fig. 1 & 2 below.

• Based on this single line diagram detailed Electrical layout, drawn to scale showing the Plan and Elevation of the Sub Station arrangement is prepared.

• A civil layout for the lands acquired for the installation of the substation will also be prepared, wherein the Electrical layout will be incorporated in the specified location, showing, Road, control room, Quarters and other civil amenities.

• In this detailed Electrical layout, the required clearances, Height of structures, space occupied by equipments etc., will be clearly marked so that the Erection Engineer will carryout erection works and installation of equipments accordingly.

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FUNCTIONAL EQUIPMENTS

• BUS BARS • The Purpose of bus bar is to receive the Power and

feed to the concerned equipments. Types : Strung Bus & Regid Bus

• Strung Bus : The Conductor (ACSR) Strung between the two ends of Sub Station through Disc. insulators and Gripper sets.

• Regid Bus : Aluminum tubes erected and Pedestal insulators over pedestal support structure.

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BUS BARS

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BUS BARS

• Points: • The Main Bus will be of strung bus and the feeding

arrangement to equipments will be Regid bus. • The insulators should be cleaned and checked for

any breakage, cracks and to be replaced. • Since the bus bars are heavy current carrying

parts, tightness of the clamps to be checked and avoid glow.

• The Pedestal Insulators may be Polycone insulator for 110KV and above and post type insulators 33 KV and below.

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POWER TRANSFORMER

• This is the Main Equipment of Substation. The Purpose of Transformer is Transmission of Power from one voltage level to the other required voltage level, with negligible losses.

• Reduction to the required voltage level. • The drop in voltage in the system is compensated

by tapings.

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POWER TRANSFORMER

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INTERNAL ACCESSORIES

• The transformer mainly comprises of Magnetic core and windings wounded for the 3 phase. Each phase will have a Primary and Secondary winding, wound according to the voltage for which it is put into use. The core and winding Units are placed in a Main tank and filled with Transformer oil.

• The transformer oil is for insulation and cooling purpose.

• The leads from the winding are brought out through the bushings for external system connections.

• The three phase windings on Primary will be connected in DELTA & the Secondary in Star as shown below:

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DELTA & the Secondary in Star

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Details of Transformer

• Voltage Rating :110 KV/11 KV

• Current Rating :52.5/525A

• Capacity :10 MVA

• Tapings :-3 To + 9% @ 1.5%

• % Impedance :10%

• Vector group :41 Dy11

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BUSHING CONNECTION

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EXTERNAL ACCESSORIES

• Main tank with value & cooling arrangement

• Bushings with C.Ts.

• Conservator

• Tap switch

• Air release Plug

• Equalizer pipe

• Explosive vent

• Temperature indicators

• Breather

• Buchholz relay

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EXTERNAL ACCESSORIES

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MAINTENANCE OF POWER TRANSFORMERS

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Item of Inspection or Maintenance

• Checking for unusual noise • Checking oil level in the conservator and bushings • Cleaning of bushings • Inspection and cleaning of breather. • Reconditioning or replacement of silica gel . • Examination of relief diaphragms to ensure that they are not

cracked or broken • Checking up or temperature alarm for correct operation • Measuring insulation resistance of windings • Testing of oil from tank and conservator for dielectric strength

on all transformer. • Checking up gap settings on bushings of transformer horn

gaps• Testing of transformer oil for acidity • Testing of oil in oil filled bushing of dielectric strength and

acidity

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periodical maintenance

• The following periodical maintenance are recommended for Power Transformers:

• Annual inspection and maintenance of power transformer should be carried out thoroughly.

• The following should be checked. Operation of Buchholz relay by pumping air. Oil level in the conservator tank using a dip stick. Check for any cracks is the foundation. Tightening of all loose bolts and nuts. Measuring rod gap. Release of air in tank and bushings. Polarization index value test with power operated megger. Checking the stop block in the rail. Check relief diaphragm. Clean Bushings

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periodical maintenance

• Calibrate temperature indicators and check up operation if temperature alarms and trips. Lubricate all moving parts in on load tap changer mechanism.

Check and tighten all connections. Check the resistance of the transformer windings. Recording Insulation values of winding by meggering with 1000 Volts Power megger, after removing neutral Earth connection – HV to Earth, LV to Earth and HV to LV and check the continuity of winding.

• Oil sample testing : Dielectric strength, Acidity content of oil is to be tested. In addition , the other tests conducted are

• a) Resistivity • b) Interfacial tension • c) tan delta • d) Dissolved gas analysis (DGA)

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EARTHING SYSTEM

• The Solidly grounded system ensures speedy & accurate sensitive of fault and isolate the faulty section. Neutral of Transformer secondary is grounded All other metallic parts associated with Electrical equipments should be grounded.

• Surge diverter should be grounded. Double Earthings should be ensured for each grounding All the groundings should be interconnected.

• The Earthing system comprises of 1) Earth conductor, 2) Earth connection, 3) Earth Pipe, 4) Earth pit and 5) Earth interconnection.

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EARTHING SYSTEM

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EARTH INTER CONNECTION

In order to interlink all the individual Earth Electrodes, it is in practice to lay an earth Mat under the ground level of Substation yard. The Earth Electrodes, in Earth pit are connected to this Earth Mat, running nearby under the Ground, so that the combined Earthing system is formed.

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MAINTENANCE OF EARTHING SYSTEM

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EARTHING SYSTEM

• The soil in Earth pit should be kept well packed homogeneously. The soil in Earth pit should be kept wet by pouring water. Earth Connections are checked for tightness. Earth pipe to be maintained intact without corrosion.

• For improving the Earthing system Charcoal, Ash, pentonite powder, Salt etc., may be filled in the Earth pit and Watered.

• Earth Resistance value to be measured and effectiveness checked, by using Earth Megger. The values are 1) Individual Electrode : < 25 ohms.

• Combined Earth Resistance : less than one ohm.

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EARTH MAT

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EARTHING SYSTEM

This should be tested by removing all connection from Electrode.

2) Combined Resistance:

< 1 ohm.

This should be linked by providing all Earth connection.

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ISOLATION & CONTROL OF EQUIPMENTS

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ISOLATORS

These are Potential Isolating Switches to isolate the equipments from the source.

This should not be used for current breaking. In Sub-station , only “Double break” (or Center rotating type as it is called) switches are used.

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ISOLATORS

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TYPES OF DOUBLE BREAK SWITCHES

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• Isolator with Arcing horns: Used before transformer to break magnetizing current.

• Isolator without Arcing horns: Used in other places of Sub-station

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• Tandem Operation for simultaneous operation for the three phases should be ensured.

• The contact pressure should be adequate to withstand load current. This is ensured by spring & tempered contact leaves. Contact pressure will be > 0.25 Kg. per ampere of normal current rating.

• The Operation should be free by proper lubrication and by treating the fixed and moving contacts with Petroleum Jelly.

• The close/open should be done from Ground level. The operating Rod should be earthed safely.

• The isolator may be hand operated (or) it can be motor operated using A.C. Motor with reduction gear & can arrangement with limit switches, to stop the motor at the end of closing/opening without overshoot.

• The Motor operated mechanism will also have the de-linking arrangement to de-link motor & gear mechanism and perform the hand operation in case A.C. Supply fails.

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BREAKERS

• The main purpose is: To break the load current or fault current It should be capable of quenching the arc quickly & effectively arising due to interruption of heavy current.

• The rating of the breaker should be well above the FAULT LEVEL of the substation, so that the breaker is capable of breaking the maximum fault current due to 3phase FAULT that may occur near. The rating is defined in MVA and is called as “RUPTURING CAPACITY”

• The time of opening should be fast. Modern breakers are as fast as to open in 2 cycles (ie) in 0.04 secs. TYPES OF BREAKERS: The breakers are classified according to the Medium by which arc is quenched.

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BREAKERS

• OIL CIRCUIT BREAKER ( OCB) : Oil is used for quenching as well as for insulation since metal tank is used.

• MINIMUM OIL CIRCUIT BREAKER ( MOCB) : Oil of small quantity is used for arc quenching only.

• VACUUM CIRCUIT BREAKER ( VCB) : Arc extinguished in VACUUM

• GAS CIRCUIT BREAKER ( GCB) : SF6 gas is used as the medium for quenching arc.

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BREAKERS

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BREAKERS

• Rated Breaking Capacity: It is the current (rms) that a breaker is capable of breaking at a given recovery voltage and under specified condition i.e. PF,RRRV

• Rated Making Capacity: The peak value of current including d.c. component during the first cycle of current wave after the closure of circuit breaker is known as making capacity Rated Short-time Capacity: It is the period for which the circuit breaker is capable to carry fault current while remaining closed.

• Rated Normal Current Rating: It is the rms value of current which the circuit breaker is capable of carrying continuously at its rated frequency under specified conditions with temperature rise of various parts within specified limits.

• Relay Time: The time elapses between the instant of fault & the closure of trip circuit. Circuit Breaker Time: The time elapses between the closure of trip circuit & the final arc

• extinction Total Break Time: It is the summation of Opening Time and Arcing time. Opening Time: The time interval lapses from the energisation of trip coil to the instant of

• contact separation. Arcing time: The time from separation of contact to the extinction of arc is called the arcing time

• Fault Clearing time: The time elapsed between the instance of the occurrence of a fault and the instant of final arc extinction in the circuit breaker i.e F.C.T.=Relay time + Circuit breaker time Total Break time)

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OPERATING MECHANISM

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BREAKERS

• The Breaker has two operation :CLOSE / OPEN

• The OPEN operation is also called : “TRIP” These 2 operation are speedily performed by using operating mechanisms of the following kind:

• a) Spring actuated : Use of spring & leavers this can be operated by hand (or) AC Motor b) Hydraulic actuated : Using hydraulic fluid like “AERO- shell oil” c) Pneumatic Actuated : using air comprised system Any type of mechanism can be employed to any type of breaker.

• Details of maintenance procedure:

• Stationary contact: Visually inspect, when contact surface is found uneven, remove it and polish with sand paper. then measure the dimension of stationary contact. When the wear becomes 3 mm or over replace the contact with a new one. Apply thin coat of Vaseline to the contact.

• Moving contact: When it is deteriorated by large current interruption remove it and polish with sand paper. Apply thin coat of Vaseline to the contact.

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QUARTERLY “CARE”

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QUARTERLY “CARE”

Q.1. External Cleaning of Insulator Prior to monsoon and as & when Shutdown is available or deposits are too thick. Dust / Dirt to be removed.

Q.2. Switch cubicle cleaning: Open the switch cubicle & Remove webs/ dust.

Q.3 Check wiring connection in switch cubicle Check wiring connection Tightly secured. Check healthiness of the relay operations.

Q.4. Compressor Check: Compare the Running Time. Q.5. Compressed Air Plant Maintenance to be carried out as per

instruction manual check for any leakage, check oil leakage, check for alarm, non Return valve to be opened & Cleaned, Verify motor thermal overload is working or not.

Q.6. Pressure switch in switch cubicle: Check the pressure valve by reducing the pressure and filling the pressure .

Q.7. Verification of SF6 Alarm Healthiness of alarm can be verified by shorting electrical circuit, not by draining SF6 Gas.

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Trouble shooting chart for SF6 circuit Breaker

• Type of Condition Possible Cause A. Gas Alarm CHECK :

1)Electrical Circuit 2)Gas pipe Braze Joints 3)Gas pipe Couplings. 4) Insulator joints. 5) Lip seal Assembly.

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Procedure for Checks

• If any leakage is felt check it with the soap water solution.

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PROTECTION FROM EXTERNAL DISTURBANCES

• Protection from Direct Stroke of lightning. • To protect all the equipments from the direct Stroh

of lighting earth mast is used. • Earth mast is a metal spike with sharp end • Height of mast is so chosen that all equipments

comes under the protective zone, defined as 45 degree cone with top of Spike as the APEX of the cone.

• Effectively grounded to permit the lightning discharge.

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PROTECTION FROM SURGES

• The surges are very high peak voltage under very high frequency.

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PROTECTION

• This will travel on the line up to the transformer winding and shatter it therefore the surges are is be prevented from entering the Transformer.

• “SURGE DIVERTORS” are provided before and after the transformer.

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PROTECTION

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PROTECTION & METERING EQUIPMENTS:

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Cross section of a resin cast VT

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Potential Transformer

• The Secondary rating of PT is 110volts 11 KV / 110 VOLT is shown, In Radial stations, P.T. used for metering only P.T. will have only a small burden (in VA).

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Current Transformer

• Each Breaker is associated with a set of C.Ts for Protection & metering

• Secondary Current: 1 Amps • Separate

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Current Transformer

• secondaries will be available for protection of metering.

• C.T. Ratios of say 600, 300, 150/1Ampere or 5 Ampere are available for usage.

• It is defined as : Ratio available : Ratio set at : • C.T. will also have a small burden (say 30 VA) to

connect meter or Relay loads. • C.T. Secondary should never be open – circuited.

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RELAYS

• 3 O/L and 1 O/L Relay Scheme for Transformers and Breakers and Differential Relay for Transformer only

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RELAYS

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D.C. SYSTEM

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D.C. SYSTEM

• Points: • 2 Sets of 110V battery are used, one set for control

of feeders and the other set for protection of Transformers and group control breakers.

• At Normal condition charger will supply small DC loads & feed charging current to Battery Heavy trip coil currents supplies by battery.

• The battery should be kept on wooden stand over insulated pedestal.

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D.C. SYSTEM

• Maintenance • The cell voltage should be around 2 VOLTS &

Specific gravity of Electrolyte 1200/27 degree. • Battery should be on trickle charge continually. • If drained due to continuous tripping it should be

put on quick charge & brought to the level. • To be tested daily for leakage is detected & for

catering of load. • If positive or negative leakage is detected, the

faulty section to be isolated & rectified. • Battery room should be free of dust ,fire etc &

properly ventilated.

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D.C. SYSTEM

• Breaker is in closed condition feeding a 11KV feeder. If any fault occurs on the feeder, the breaker should trip. Cutting off supply to the feeder. The sequence is as follows:

• Fault occurs on the feeder & heavy current flows thro the circuit

• The C-T Senses the fault current & high secondary current flows through the Relay coil.

• The relay contact closes & D.C circuit is closed. • With breaker kept on Auxiliary Contacts 4-4’& 3-3’ are N/c &

hence D-C + Ve & - Ve juice is supplied to the trip coil • Trip coil energized & the plunger is moved up & trigger the trip

latch. • The Breaker is tripped of Aux Switch moves of the contacts 4-

4‘& 3-3’ are now N/o & hence the trip coil current is cut off. • Since faulty section is isolated, the current in secondary is

zero & hence relay moves back to its normal position, breaking the relay contact.

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TRANSFORMER PROTECTION

• The transformers are controlled by group control breaker on 110 KV side & independent L.V. breakers on 11KV side. If a fault occurs on transformers these breakers should be tripped.

• The fault on the transformer is identified by: a) Over current relay b) Differential Relay c) Bucholtz relay d) Winding temp relay e) Pressure Release Valve Relay

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• Closing of these contacts by actuation of relay in case of fault initiates the trip circuit of the controlling breaker thro’ a common relay called “MASTER RELAY”

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L.T.A.C. SUPPLY SYSTEM

• A Station transformer of 100KV 11KV/400V as connected to the 11KV Bus. provide A-C supply (Alternative supply) either fed from another substation (or) from a generator will be provided for emergency.

• The LT A-C supply / Alternative supply is fed to the A-C panel in control room from which it is supplied to the following requirements with power control arrangements.

• To A.C motors of breaker mechanism, Air compressor systems,

• To cooling fans of pump motors of power transformer& OLTC operation to battery charger Yard lighting and control room lighting

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TAP OPERATION

• Since the sub section in the sending end of power to the load pockets, it is necessary to maintain constant voltage at the secondary, irrespective of voltage received on HV side. This is done by providing On Load Tap Changer.

• A diagram of tapping coil arrangement with Main primary coil with pre selector AND Selector contacts and also its On load operational features sequence are shown in the two figures enclosed.

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PHASE TO EARTH AND GROUND CLEARANCE

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STANDARD CLEARANCES ADOPTED IN PRACTICE

• b) SECTIONAL CLEARANCES in “MM” • 1. 230 KV -4270 MM • 2. 110 KV -3350 MM • 3. 66 KV -3050 MM • 4. 33 KV & 22 KV -2740 MM • 5. 11 KV -2590 MM • c) BAY WIDTH “IN METRES” • 1. 230 KV -12.2 • 2. 110 KV -9.5 • 3. 66 KV -7.0 • 4. 33 KV -4.5 • 5. 22 KV -3.8 • 6. 11 KV -3.5

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CONCLUSION

• The sub station forms part & parcel of the power of the power system net work. The essential equipments installed in a sub station, with the operation and control features are explained in detail which will provide practical utility information

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SUB STATION EQUIPMENTS AND ITS FUNCTIONS

• Bus Bars:Various incoming and outgoing circuits are connected to bus bars.

Circuit Breaker:Switching, automatic interruption

Isolator, also called disconnecting switch:Disconnection under no load condition.

Earthing switch: Discharging the voltage on the lines to earth for safety.

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Lightning arrester:Diverting the high voltage surges to earth and protect insulation

Current Transformer:Stepping down current for measurement protection and control.

Voltage Transformer:Stepping down voltage for purpose of protection and control

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Series reactor:To limit short circuit current level. Used in approximate location.

Tap-changer:Used for voltage control, stepping up and stepping down voltages.

Shunt reactors:Used for long EHV transmission line to control voltage during low load period. To compensate shunt capacitance of transmission line.

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Shunt capacitors:Power factor improvement, switched in during low power factor loads and less voltage.

Series capacitors:Used with EHV transmission lines to increase the power transferability.

Coupling capacitors and line traps:For carrier current equipment.

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RELAYS

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Differential relay

Differential relay responds to vector difference between two or more similar electrical quantities.

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Impedance relay

Impedance relay operates when the impedance between relay point and fault point is below a specified value.

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Over current relay

Over current relay responds to increase in current. When the current in the operating coil increase above certain value the relay picks up.

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Instantaneous relay

Instantaneous relay is any relay without intentional time lag and with operating less than 0.2sec.

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Time relay

Time relay is one in which operating time can be set.

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Static relay

Static relay the relay in which the measurement is performed by a stationary circuits and which has no moving parts.

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Fault clearing time

Fault clearing time between occurrence of fault and final arc extinction.

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Relay time

Relay time between occurrence of fault and closure of relay contacts.

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SAFETY IN SUBSTATION

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General safety methods

• While execution of any work, that part of equipment or line is to be isolated from the supply.

• Using discharge rods, charging, current if any is to be discharged.

• Using Earth rods, all phases/conducting paths are to be property earthed by securing good Earthing.

• When even opening an AB switch or removing of fuse, it is also advisable and preferable to wear rubber gloves.

• Use of belt rope is another safety method to be adapted to work on elevated places.

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Line clearance (LC)

• For Grid feeders and Stations, the authorized officer for issue of line clearance is S.E. (L.D. Centre), Madras, for 110 KV, 66 KV, radial feeders SE/ concerned and for 33 KV EE/O&M are the approving authorities. Without obtaining proper approval from the competent authority, no L.C. should be issued nor availed by anybody.

• Hence, after getting proper approval, line clear is to be issued to the requested party. Both should have knowledge about equipments. The line clear issuing person should clearly record the following:

• a) Which breaker is tripped? • b) Which A.B. switches were opened? • c) Where Earthing was done? • d) What is the Safer place / Line to carry on the execution of

work.?

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Safety arrangements in control room

• Keyboard should be in open condition with keys are orderly arranged to take out quickly during any urgency. Line clear keyboard should be in locked up condition to prevent other persons from using the keys inside, before the cancellation of the Line clear permit.

• • Rubber mat should be provided on the floor in front of the panel board. • • The following details should be clearly displayed in the control room. • a) Approved operating instructions for all equipment’s. • b) Break down instructions. • • The operator should be fully conversant with the above instructions and the must be

able to act quickly and effectively. • • The D.C. cable layout, panel-wiring diagram and earthing layout should be displayed in

the control room. This is necessary to attend the faults immediately after their occurrence. D.C. Earth leakage test system should be available.

• • There should not be any defective power plugs, switches and bulb holders in the control

room wiring. • • One artificial respirator should be available in ready condition. Stools made of insulating

material should be used for operating HT communication equipment (Telephones). • • Adequate number of rubber gloves, belt ropes, discharge rods, and earth rods in good

condition should be available in the control room.

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Safety arrangements in battery room

• Battery room should be in locked up condition. • “Naked flame is prohibited inside of the battery room” and “Smoking

prohibited” warnings should be kept written on the battery room door.

• One exhaust fan should be functioning. • Accurate D.C. cell testing voltmeters, hydrometers and

thermometers should be available in the battery room. • Pilot cell voltage, specific gravity and temperature should be taken

every week. • The specific gravity should not be maintained below 1195 at 15.6°C

and below 1183 at 32. 20°C. The battery should not be allowed to discharge below 1160.

• Cell voltage should be maintained between 1.95 V to 2.05 V. The battery should not be allowed to discharge below 1.85 V.

• Battery should be allowed neither to over charge not to undercharge. It should not also be kept idle.

• Electrolyte level must be checked in every shift. It must be ensured that the level is 10mm above the top of the plates.

• Weak cells should be rectified then and there. • While taking specific gravity readings, care must be taken not to

allow the acid to come in contact with the eyes.

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Safety adopted for transformers

• Transformers are to be maintained periodically as per schedule. Switches on HV side and LV side are to be isolated after reducing the Load by tripping the breakers.

• Kiosks and OCB: All the Live parts of the kiosk should have H. T. insulation tape. To be protected by wire mesh. It should be vermin proof. Keys are to be kept with interlock. Whenever to open the door of the kiosk, kiosk should be tripped and link should be opened by the interlock key. The opening of the links is to be verified physically. After doing all the above precautions, the tank should be lowered down. Proper care is to be taken and it should be kept in mind that supply is available at the roofing. Oil leak should be arrested. Back feeding is avoided. Cotton waste should not be used for clearing purpose.

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Circuit Breakers

• SF6 breakers are maintenance free comparing to the air blast circuit breakers and oil circuit breakers. Preventive maintenance avoids premature failure. It shall be done as per manufacturer’s recommendation.

• Continuous monitoring of gas pressure is essential. If there is gas leakage, top up before gas low alarm / indication is received. Gas leakage test shall be carried at all leakage sources by availing shut down.

• If the breaker is pneumatically operated, compressor starting pressure, building up pressure time shall be checked with respect to pre-commissioning test values.

• Air pressure drop for each operation shall be checked and ensured the values are within limits. • If the breaker is spring operated mechanism, spring charging time shall be checked with the pre-

commissioning test values. For each closing operation, see that spring is charged fully and indication received.

• The following breaker operation checks shall be done as per periodicity. • 1. Breaker opening time & closing time are within limits • 2. Whether pole discrepancy relay operates. • 3. Checking of all operational lockout. • 4. Checking of all pressure settings • 5. Checking of all inter locks • Measurement of breaker contact resistance, resistance of close and trip coils and MV drop test across

terminal connectors shall be done periodically. • Healthiness of operation counter shall be checked. • Tightness of all cable connections in control cubicle and working of space heater shall be checked. • Checking of door gaskets, blocking of spare cable entry holes and must be ensured for vermin proof. • Cleaning of breaker poles and support insulators shall be done with clean Gada cloth. Using cotton

waste shall be avoided. Vacuum cleaners shall be used for cleaning for control cubicle. Ensure that the terminal connectors are free from corona.

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Safety in AD switches

Handle of the AB switch is to be earthed properly. Blades should be kept at opening position. It should not be closed automatically; proper maintenance is to be done for this. AB switchblades are to be opened fully. AB switches are to be kept locked on both conditions. AB switches are to be opened only after tripping the breakers.

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Safety in Lightning arresters

Lightning arresters are used to bypass the sudden lightning surges and thereby to protect the equipment’s. Only after proper discharging is done on lightning arresters, it should be attempted to attend to maintenance. Fencing is to be provided around lightning arresters. A door arrangement with lock is to be provided. Separate earth connections are to be provided for lightning arresters.

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Safety in instrument transformers

• Current transformer secondary side is to be short circuited during maintenance and testing. Before doing any testing, the current transformers are to be discharged.

• Potential transformers primary side is to be Earthed

during maintenance and testing. Secondary side is to be earthed at only one place. Whenever giving connection, or removing meters on the secondary side of die potential transformer, the fuses are to be removed and renewed.

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Capacitors

Capacitors should be provided inside fencing. Before attempting to do any work, proper discharging is to be done. They only it should be attempted for maintenance work. Proper Earthing should be provided during the execution of the work. After completion of the work, Earthing is to be removed.

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Earth pits

• Sub-station earth connections should be properly maintained so that the earth resistance is minimum. Water should be poured in the earth pits daily. Earth connections, must be capable of protecting the persons working in the electrical equipment’s and protect in the equipment’s during heavy fault current. Earth resistance should not exceed the following limits.

• Grid stations: I Ohm • Other sub-stations ..2 Ohm. • Distribution transformers ..5 Ohm.

• They must be a clearance of 5 feet, between the sub-station fence and the electrical equipment’s / live points. The fence should be earthed at every 200 feet, separately. Generally the fence Earthing should not be linked with the sub-station Earthing. But if the clearance is less than 5 ft. feet fence Earthing must be linked with the sub-stations Earthing. The iron gates in the sub-station fence should also be earthed separately.

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Fire fighting equipments

The equipments are to be kept on good and working condition. Proper schedule of maintenance is to be done for keeping them in good conditions. The equipments should be kept at an easily accessible place so as to use them immediately under emergency. Dry sand heaps are to be available wherever necessary. Empty buckets are to be provided.

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S.S. Yard

• S.S. yard should be provided with fencing. • Unauthorized persons should not enter into the

yard • Cable ducks are to be provided with slabs. • Best illumination is to be provided for the yard. • A warning board with a display that “Umbrella”

stick Dogs should not be brought inside the yard” is to be provided at the entrance of the yard.

• A separate room is to- be provided for keeping the empty drums. At the entrance of the room “No smoking” Board is to be provided.

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General causes for accidents in SS

• Mal operation in view of symmetrical designing of equipments.

• Opening of switch on Load/ working without proper supply isolation.

• Working without de-energizing and earthing of lines and equipments.

• Charging the equipment without removing the earth rod. • Working without knowing the back feeding available in the

equipment. • Operation without making back feeding and alternate feeding

into oneness (Two phase to Three phase linking) • Charging the equipment without concurrence on both ends of

supply point (eg. Grid feeders). • Charging the feeders without considering the total number of

line clears availed in a feeder (e.g. charging after returning one L.C.)

• Giving L.C. in the feeder, but climbing on the roof top of the KIOSK (without Bus L.C.)

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Avoidance of accidences

• Strictly adopting LC procedures and operating instructions in every operational work though it is minor.

• All operation in the yard in the presence of operator or at least with the knowledge of the operator.

• Be always keep in mind that “Authorized Person; Approved Work”

• Through knowledge of equipments and systems, observational ability, analytical ability and communication skills are required to the operators.

• Ready to use fire-fighting equipments and operators should have knowledge in using the same.

• No defective equipments should be put into service.

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Conclusion

In every sub-station, action should be taken for adopting safety precautions, so as to avoid accidents. All staff should be well educated about the safety rules, precautions and methods.

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Case study

An operator on shift duty observed tripping of an 11KV Town Feeder with loud noise. He went to the yard and charged the OCB of the concerned feeder after resetting the relay with indications of 3 OL and 1 EL. Immediately on charging there was loud burst and oil with flame from the Breaker engulfed the operator resulting in a fatal accident. After thorough inspection and investigation following were found to be the causes for the accident.

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Basic cause

The breaker had not immediately isolated the fault by tripping. There, had been sluggishness in breaker operation, which resulted in feeding of fault with high current, arcing, carbonization of oil and heavy evolution of gases. (Unsafe condition)

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Major causes

• All the moving contacts of the breaker were highly corroded without replacement (Unsafe condition).

• Oil was not tested before filling into Breaker (Unsafe condition).

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Minor causes contributing the accident

The operator did not check for any indication like smoke or spilling of oil surrounding the tank or thro’ the vent pipe. When there were indications of 3 OL and 1 EL the operator should have been more alert and checked for any near by fault. (Human error -Unsafe action)

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LIFE MANAGEMENT OF STATION BATTERIES THROUGH CELL MANAGEMENT

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BATTERY

• Over the years the batteries that are used in power plants and substations have not changed a lot. Yes, we have batteries made of different material, some of them are sealed, and others use different electrolytes.

• The battery system usually forms the heart of the DC control and protection system for the station. This DC system is the power source for equipment control and protection. The need to have this system extremely reliable is what drives preventative maintenance on batteries.

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• Regardless of the type of battery, it must be maintained to function properly. We typically maintain our batteries on a weekly, monthly, and yearly schedule.

• On a weekly cycle, the battery is inspected, several cell voltages are read, and the respective specific gravities are checked.

• On a monthly basis, all the cell voltages are read and all the specific gravity readings are taken.

• Annually, all the inter cell connections are removed, cleaned, lubricated and reinstalled. Doing all of the recommended maintenance requires many man-hours.

BATTERY

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BATTERY

• The installation of the monitoring system consisted of installing 2 sensing modules to the side of each battery jar. These are attached with a self-adhering tape that is an integral part of each cell module. In addition, it was decided to install a wire gutter to contain the cell-to-cell data link and other wire. This made for a neat installation. See Figure 1.

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BATTERY

126

BATTERY

127

BATTERY

• Figure 1 shows the sensing modules and wire gutter attached to the jars. Also shown are the measuring leads attached to the bus bars, and the chokes attached to the main battery leads.

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BATTERY

• Figure 2 shows the communication interface (with built in modem) and the bank monitor/controller mounted on the wall, the current sensor mounted at cell #1, and the rest of the hardware.

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BATTERY

• Next, connections were installed to each bus between the battery posts. These connections are used to measure cell voltage, and voltage drop across the cell when a one-millisecond bank load is applied for the current path integrity test.

• A choke (isolation inductor) is installed around each main battery lead. The installation of all the equipment took two days and consisted of mounting modules on each cell, installing power cabling, and mounting the bank monitor and communications interface equipment. See Figures 2.

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BATTERY

• Measuring leads • chokes • Current sensor • Bank monitor/system controller • Communications interface • The overall system is shown schematically in Figure

3. The data links between the cell monitoring modules are optically isolated to eliminate the possibility for a current path to exist between modules. The isolation inductors (chokes) provide test isolation for approximately one millisecond during the connection resistance test (current path integrity test).

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BATTERY

132

BATTERY

• Once the equipment was installed the system was set up and calibrated. A complete set of readings was taken on the battery and the data entered into the software as the starting point for monitoring. Much to our surprise, within days of putting it in service, the monitoring system started to report problems with the battery.

• The first deficiency it found was high resistance at several inter-cell link and battery post connections. We had taken resistance readings on the connections and not found any problems. However, the monitor takes connection voltage-drop readings while a load of about 400 amps is applied to the battery for one millisecond (current path integrity test). This method found poor connections that we had missed. See Figure 4.

• Figure 3 shows the overall configuration of the non-invasive battery monitoring system

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BATTERY

Figure 4 is a view of the opening page showing cells with problem in red. All the cells in question had high resistance connections.

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BATTERY

• The current path integrity is measured by employing the four-wire resistance technique. To prepare for the measurement, the bank monitor simultaneously instructs all cell monitors to measure their cell’s voltage and store the result in memory.

• The bank monitor next switches an electronic load across the bank that draws current for approximately one millisecond. At the peak of the bank current, which is arranged to be roughly equal to the amp-hour capacity of the bank, the bank monitor again simultaneously instructs all cell monitors to re-measure cell voltage and subtract the results from the zero-current values of voltage already stored in memory.

• The difference voltage for each cell, reported as “delta V” is proportional to the resistance of the current path including both the cell and strap/post connections. Figure 5 shows the relationship of the voltages and currents during this test.

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BATTERY

136

BATTERY

• Upon opening the software up to the individual cells, one can get either a cell-by-cell view of the battery or a view that shows the average cell, the high cell, and the low cell in each category.

• In looking at Figure 6 you can see the trends of cell #1 over a period of time. Of interest is the gradual rise in the voltage drop across the connection of this cell. With every voltage drop alarm, our electricians reported that the connecting bolts did tighten before the torque wrench reached the desired value.

• It was also interesting to note that just prior to developing a high resistance connection the battery underwent a load cycle as indicated by the downward spike in the readings, shown in Figure 6.

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BATTERY

• Voltage-current relationship for measuring the voltage drop across connection resistance in the series circuit

• The load is electronically inserted across the battery for one millisecond. The chokes provide test isolation.

• Figure 5 shows the process for automatically measuring current path integrity

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BATTERY

Figure 6 gives a view of the screen that gives trends on individual cells.

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BATTERY

• After some months of operation MCM reviewed the data that was being taken. They noticed that the water consumption of the battery was fairly high. From the Float Current Bypass cell readings it was noted that all the cells were bypassing 100% of the float current. In essence this indicated that the battery was being over charged, making it use more water. We started lowering the float voltage until most of the cells read in the 80% bypass range. This reduced water consumption in the battery. See Figure 7.

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BATTERY

• The system allows the user to look at many conditions in each cell, and the battery bank as a whole.

• In addition it will record bank discharges, showing the overall bank and each cell’s performance during the discharges.

• This information goes a long way to assuring the quality and integrity of the battery.

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BATTERY

• The monitoring system performs a test on the battery however often the user desires. The monitoring system is set up to automatically do a test and collect data every 24 hours at Morrow Point.

• This gives us good data without building a huge database. However, during a load test on the battery or during an actual emergency event, the battery monitoring system steps up its data measurement rate to capture the performance of the battery, during the event.

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BATTERY

• The data is downloaded to a computer in the plant once a week, reviewed, and any necessary actions taken.

• This test sequence yields the data that we have looked at above. This system has been in use for almost two years, and has successfully found serious problems; it has also minimized the required battery maintenance.

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BATTERY

• The cost of this system approaches the cost of a battery. In order to justify this cost we must take a close look at what our battery does, and how important it is in the overall scheme of things.

• Not all battery systems are used for the same purpose, however most of them operate the control and protection schemes for large rotating equipment and breakers when they are employed in power plants and substations.

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BATTERY

• Figure #7 is a screen view showing the high, low and average of all the cells. Note that the fluid levels move down. The straight line shows where water was added. Note place where the bank voltage is lowered you also notice that the slope of the water use curve changes, and the cell bypass currents drop.

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BATTERY

• For the most part the DC control and protection circuits in Reclamation facilities run on battery chargers most of the time. Only under charger failure or loss of station AC power do we need the batteries. As often happens, it is during times of system or equipment problems when station AC disturbances will occur.

• This is simply Murphy’s Law in action. These are the times when controls, protection and breakers MUST operate to prevent damage to equipment. Thus, the main purpose of the battery is to provide critical power to control and protection equipment when it most needs it. Failure of the battery system during these periods of time can have consequences that range into the millions of dollars for the equipment they protect.

• Thus it must be argued that the justification for the monitoring system should be based on the cost of these consequences rather than the ratio of the cost of the battery versus the monitoring system.

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BATTERY

• The bottom line for the monitoring system at Morrow Point is that it has drastically cut our man-hours of maintenance. Since the monitor’s installation, several bad connections have been corrected, and the battery bank has had water added only twice.

• Then since system has been in service; a set of readings was manually taken after one year to verify the readings of the monitoring system, and they proved to be identical. The Morrow Point crew has decided that a lot of the maintenance that was done previously was probably causing as many problems as they solved. Redoing the jumper bar connections probably loosened more connections than it did to repair possible corrosion and tightness problems.

• The need to be assured that your battery will operate as designed when it is needed most has been assured. This along with the reduced maintenance makes the cost of the system easily justifiable.

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SAFETY IN SUB-STATION

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• Prevention of damages to equipment’ s and men working on then due to any accidents is an essential aspect in any establishment. Prevention of accident which is an unforeseen one is more essential aspect of any establishment / organization.

• As accidents occur mainly due to unsafe execution, actions and circumstances, these accidents can be avoided by adopting safety precautions, implementing safety procedures and following safety rules.

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• General safety methods: • While execution of any work, that part of equipment

or line is to be isolated from the supply. • Using discharge rods, charging, current if any is to

be discharged. • Using Earth rods, all phases/conducting path are to

be property earthed by securing good Earthing. • When even opening an AB switch or removing of

fuse, it is also advisable and preferable to wear rubber gloves.

• Use of belt rope is another safety method to be adopted to work on elevated places.

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• Safety methods to be adopted in Sub-Stations :

• In any work is to be attended to any line, first and fore most item of work is to get proper approval from the competent controlling authority for execution of the work specifying the date, time, duration, place of work, affected parties etc. .

• For Grid feeders and Stations, the authorized officer for issue of approval is S.E. (L.D. Centre), Madras, For 110 KV, 66 KV, radial feeders Superintending Engineer / Distribution is the approving authority. Similarly for 33 KV Divisional Engineer incharge of distribution is the approving authority.

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• Without obtaining proper approval from the competent authority, no L.C. should be issued nor availed by anybody. If the above procedure is not followed, it is nothing but a suicidal. Further it also amounts to murder of others.

• So, after getting proper approval, line clear is to be issued to the requested party. But the issue and receiver should be aware/have full knowledge about the SS equipment’s, control room panel details etc.,

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• The line clear issuing person should clearly record the following:

• a) Which breaker have been tripped • b) Which A.B. switches were opened • c) Where Earthing was done • d) What is the Safer place / Line to carry on the

execution of work

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• Safety arrangements in control room:

• Key Board should be in open condition so that the keys could be taken out quickly during any urgency.

• Line clear keyboard should be in locked up condition to prevent other persons from using the keys inside, before the cancellation of the Line clear permit.

• The keys should be placed in the key board in an orderly manner according to their numbers. Otherwise, the required lock could not be opened in time and the possibility of opening a wrong lock may happen.

• Rubber mat should be provided on the floor in front of the panel board.

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• The following details should be clearly displayed in the control room.

• Approved operating instructions for all equipment’s. • Break down instructions.

• Operating instructions including for the emergency operations to be carried out in the event of operation of buchholz relay. Differential relay, Group control trip, total supply failure, grid failure. The operator should be fully conversant with the above instructions and the must be able to act quickly and effectively.

• The Board containing D.C. cable layout. A cable layout panel wiring diagram and Earthing layout should be displayed in the control room. This is necessary to attend the faults immediately after their occurrence.

• 5) D.C. Earth leakage test system should be available.

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• There should not be any defective power plugs, switches and bulb holders in the control room wiring.

• One artificial respirator should be available in ready condition.

• Stools made of insulating material should be used for operating high tension communication equipment’s (Telephones).

• Adequate number of rubber gloves, belt ropes, discharge rods, and earth rods in good condition should be available in the control room.

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• Battery room: • Battery room should be in locked up condition. • “Naked flame is prohibited inside of the battery room” and “Smoking

prohibited” warnings should be kept written on the battery room door. • One exhaust fan should be functioning. • Accurate D.C. cell testing volt meters, hydro meters and thermometers should

be available in the battery room. • Pilot cell voltage, specific gravity and temperature should be taken every

week. • The specific gravity should not be maintained below 1195 at 15.6°C and below

1183 at 32. 20°C. The battery should not be allowed to discharge below 1160.

• Cell voltage should be maintained between 1.95 V to 2.05 V. The battery should not be allowed to discharge below 1.85 V.

• Battery should be allowed neither to over charge not to undercharge. It should not also be kept idle.

• Electrolyte level must be checked in every shift. It must be ensured that the level is 10mm above the top of the plates.

• Weak cells should be rectified then and there. • While taking specific gravity readings, care must be taken not to allow the

acid to come in contact with the eyes.

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• Safety adopted for transformers:

• Transformers are to be maintained periodically as per schedule. Switches on HV side and LV side are to be isolated after reducing the Load by tripping the breakers.

• Kiosks and OCB : All the Live parts of the kiosk should have H. T. insulation tape. To be protected by wiremesh. It should be vermin proof. Keys are to be kept with interlock. When ever to open the door of the kiosk, kiosk should be tripped link should be opened by the interlock key. The opening of the links are to be verified physically. After doing all the above precautions, the tank should be lowered down. Proper care is to be taken and it should be kept in mind that supply is available at the roofing.

• Oil leak should be arrested. Back feeding is avoided.

• Cotton waste should not be used for clearing purpose.

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• AB switches:

• Handle of the AB switch is to be earthed properly. Blades should be kept at opening position. It should not be closed automatically, proper maintenance is to be done for this.

• AB switch blades are to be opened fully. AB switches are to be kept locked on both conditions.

• AB switches are to be opened only after tripping the breakers.

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• Lightning arresters :

• Lightning arresters are used to bypass the sudden lightning surges and thereby to protect the equipment’s.

• Only after proper discharging is done on lightning arresters, it should be attempted to attend to maintenance.

• Fencing is to be provided around lightning arresters. Door arrangements with lock is to be provided. Separate earth connections are to be provided for lightning arresters

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• Current transformers:

• Current transformer secondary side is to be short circuited during maintenance and testing.

• Before doing any testing, the current transformers

are to be discharged.

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• Potential transformers:

• Potential transformers primary side is to be Earthed during maintenance and testing. Secondary side is to be earthed at only one place. Whenever giving connection, or removing meters on the secondary side of die potential transformer, the fuses are to be removed and renewed

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• Capacitors and H. T. Coupling capacitor: • Capacitors should be provided inside fencing.

Before attempting to do any work, proper discharging is to be done. They only it should be attempted for maintenance work. Proper Earthing should be provided during the execution of the work.

• After completion of the work, Earthing is to be removed.

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• Earth pits:

• Sub-station earth connections should be properly maintained so that the earth resistance is minimum. Water should be poured in the earth pits daily.

• Earth connections, must be capable of protecting the persons working in the electrical equipment’s and protect in the equipment’s during heavy fault current.

• Earth resistance should not exceed the following limits.

• Grid stations: I Ohm Other sub-stations ..2 Ohm

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• Earth pits:

• Distribution transformers ..5 Ohm.

• They must be a clearance of 5 feet, between the sub-station fence and the electrical equipment’s / live points. The fence should be earthed at every 200 feet, separately. Generally the fence Earthing should not be linked with the sub-station Earthing. But if the clearance is less than 5 ft. feet fence Earthing must be linked with the sub-stations Earthing. The iron gates in the sub-station fence should also be earthed separately.

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• Fire fighting equipments:

• These equipment’s are to be kept on good and working condition. Proper schedule of maintenance is to be done for keeping them in good conditions. These equipment’s should be kept at an easily accessible place so as to use them immediately under emergency.

• Dry sand heaps are to be available wherever necessary. Empty buckets are to be provided.

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• S.S. Yard:

• S.S. yard should be provided with fencing. • Unauthorised persons should not enter into the yard • Cable ducks are to be provided with slabs. • Best illumination is to be provided for the yard. • A warning board with a display that “Umbrella” stick

Dogs should not be brought inside the yard” is to be provided at the entrance of the yard.

• A separate room is to- be provided for keeping the empty drums. At the entrance of the room “No smoking” Board is to be provided.

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• General

• The territory of the work spot which was declared safety to work is to be clearly identified by tying a rope. Inside this boundary is to be further identified by hanging a green flag. Outside this boundary where it is unsafe to work is to be identified by a red flag.

• Wherever necessary caution boards like “Men on working” “Don’t Switch on“ Safe for work” etc., are to be provided.

• If any unauthorized, unskilled staff happen to go near the equipment’s he can do so with the assistance and under the vigil of an experienced, authorised staff.

• Conversation is strictly prohibited wile execution of any work. It should be totally avoided especially when work is being carried out on any bus bars and kiosk.

• Placing the materials, tools and plants and men are to be at a safety clearance from the Live. parts.

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General:

• T & Ps like spanners etc. are to be lifted and brought down only by means of ropes and not by throwing and catching.

• Study and safe ladder with steps at convenient intervals is to be used. To avoid slippage of the ladder, necessary precaution is to be taken at the bottom of the ladder by providing empty gunnies.

• Lifting of any ladder or rods (Earth) are to be done only horizontally. Vertical lifting may cause damages by interrupting with the safe clearances.

• The bus and line links art’; to be kept opened while doing work on OCB and OMCB Summing up, 100% care should be taken in adopting and implementing safety rules and precautions.

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• Conclusion: • In each and every sub-stations, action should be

taken for adopting safety precautions, so as to avoid accidents. Each and every staff should be wel1 educated about the safety rules, precautions and methods. If everybody is aware of the safety procedures, rules etc., accidents can be eliminated in sub-stations.

Sub Station Training Program

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Transcript of Sub Station Training Program