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substations INTRODUCTION Electrical power plays an important role whenever man lives and work in industry, Agriculture, Transportation etc. The living standard and prosperity of a nation very directly with increase in use of power. Electrical power is the back born of industrial world today. Further comfort convenience and safety of large population all over the world depends upon electrical power. “Energy can neither be created nor be destroyed; it can be change from one form to another”; the famous law of conservation of energy. Power system consist of 3 stages I. Generation II. Transmission III. Distribution Power is generated in the power station and distributed through substation efficiently and effectively. Substation has a major role in transmission of electricity. Westhill substation is a 110/11 KV substation.

GENERATION Electrical power generated in power station where power is converting from one form to another and give electrical energy as output. There are many type of generating station according to energy source. The major source of energy in the world is coal, oil, gas and water. The sources are very unevenly distributed in the world. In Kerala most of power is generating by hydro electric power station. Because the availability of water in this state is very high when compared to others. In hydro electric power stations potential energy at high level is utilized for the generation of electric energy. The water from upstream is guided to the power house through penstock which discharges the water to the inlet of hydraulic turbine. The turbine converts most of the kinetic energy of water into mechanical or rotating energy. The alternator converts this rotational energy into electrical energy.  In Kerala there are 12 hydro electric projects. In thermal power station steam is utilized for rotating turbine.  In Kerala there are 4 thermal projects:  KPCC Mylathy  BDPP Brahmapuram  KDPP Nallalam  RGCCP Kayamkulam

POWER GRID The all generating stations, substations and feeders are connected in electric network is called power grid. The different states uses different kinds of energy sources for produces electricity based on the availability of energy sources. The source may not available whole year so we can import and export electric power according to its availability through grid. in Kerala hydro electric power is used for producing electricity so in rainy season there is a plenty of water and in all generating station there are a large amount water and can produce electricity in large quantity which is higher then that of our utilization. So the excess power can be export to other stated and in summer season there are decreases in electric power because of the lack of water during this period we input electricity from other states because power cannot be stored. So equilibrium is maintained in whole of the year the system connects all stations is called power grid.

TRANSMISSION

The electricity produced in different generating stations are step up in to extra high tension voltage and transmit to consumers through transmission and distributions lines. Transmission line carry power at high voltage such as 66KV, 110KV, 220KV, 400KV over a long distance from generating stations to the major load centre or recovering stations. The power is supplied to various consumers from secondary substations by means of distribution lines.

SUBSTATIONS: A substation may be defined as the assembly of various electrical apparatus installed to perform. 1. To transform high voltage to low voltage and vice versa. 2. To switch ON and OFF the power lines. 3. To convert AC to DC and vice versa (power conversion) 4. To convert frequency from one value to another 5. To improve the power factor by installing synchronous condenser. The power generated in the generating stations stepped up and transmitted to load centers. There the high voltage stepped down and distributed to consumers. In Kerala:  Two 440KV substations » Madakkathara » Pallippuram  21 – 220KV substations  134 – 110KV substations  85 – 66KV substations SUBSTATION EQUIPMENTS The equipment depends upon the type of substation, service requirement and the degree of protection desired. However, in general, substation has the following main equipments: BUS-BARS: When a number of lines operating at the same voltage have to be directly connected electrically, bus-bars are used as the common electrical component. Bus-bars are copper or aluminium bars (generally of rectangular z-section) and operate at constant voltage. The incoming and outgoing lines in a substation are connected to the bus-bars. The most commonly used bus-bar arrangements in substations are: I. Single bus-bar arrangement. II. Single bus-bar system with sectionalisation. III. Double bus-bar arrangement. A detailed discussion on these bus-bar arrangements has already been made. However, their practical applications in substations are discussed. INSULATORS: The insulators serve two purposes. They support the conductors (or bus-bars) and confine the current to the conductors. The most commonly use material for the manufacture of insulators is porcelain. There are several types of insulators (e.g. pin type, suspension type, post insulators etc.) and their use in the substation will depend upon the service requirement. For the example, post insulators consist of a porcelain body, cast iron cap flanged cast iron base. The hole in the cap is threaded so that bus-bar can be directly bolted to the cap. Porcelain: now-a-days porcelain is used extensively for the manufacture of insulators. It is produced by firing a mixture of Quartz, Kaolin and Feldspar at a high temperature. It is mechanically stronger than glass. Its surface is not affected by dirt deposits and it withstands temperature changes. INSULATING SWITCHES: In substations, it is often desired to disconnect a part of the system for general maintenance and repairs. This is accomplished by an isolating switch or isolator. An isolator is essentially a knife switch and is designed to open a circuit under no load. In other words, isolator switches are operated only when the lines in which they are connected carry no current. POWER TRANSFORMER: A power transformer used in a substation to step up or step down the voltage. The modern practice is to use 3-phase transformers in substations; although 3 single phase bank of transformers can also be used. The uses of 3-phase transformer (instead of 3 single phase bank of transformers) permit two advantages. 1.Only one 3 phase load tap changing mechanism can be used. 2.Its installation is much simple than 3 single phase transformers. Core-construction:

         The core is build up with high grade non aging cooled rolled grain oriented silicon steel lamination having high permeability and low hysteresis loss.  Three legged milled and low hysteresis loss and inter locked type core construction gives adequate mechanical strength and prevent vibration during operation.

Winding construction: The windings are arranged to ensure free circulation of oil and reduce hot spot in windings. Type of cooling is ON/OFF. All insulation parts are made from high quality pre compared press board. Windings are designed and manufactured to with stand short circuit forces. Tank: The tank is welded construction side walls top and bottom of tank are stiffened by structural steel. All bolted construction to tank are made oil tight with oil seals. Tank is provided with two earth terminal one on each mercury switch attached to closes alarm circuit. There by the operation come to know that there is some fault in transformer. On load tap changer: The transformer is provided with 33KV class on load tap changer. Driving mechanism of OLTC is transported separately. Transportation brackets for DLTC must be removed. Coupling: Transformer connected parallel with the help of a bus coupler for maintaining equal load Bushings: The voltage bushings are oil filled type and HV neutral LV and LV neutral bushings are of plain porcelain type. Buchholz Relay: It is a gas actuated relay used for the protection of oil immersed transformers against all incipient faults and makes use of the fact that fault decompose oil thus generating (more than 70% of hydrogen) gases. This relay can only be fitted to the transformers having conservator tank and is connected by means of pipes between the top of the transformer tank and conservator and is therefore under normal conditions of operation, the relay, will be with full of oil. The relay consist of an oil tight container with two internal hinged hollow floats, inside of which the mercury switches are provided, which in turn connected to the external alarm and to the tripping circuit. When an incipient fault occurs in the transformer, the arc due to fault causes decomposition of transformer oil. The product of decomposition contain more than 70% of Hydrogen gas, which being light, the gas bubbles get collected in the upper portion of the Buchholz relay, thereby the oil level in the Buchholz relay drop down. The float floating in the oil tilts down with the lowering oil level. While doing so the mercury switch attached to it closes the alarm circuit. There by the operator come to know that, there is some incipient fault in the transformer. The transformer is disconnected as early as possible and the gas sample is tested. The testing of gas gives clue regarding type of fault. Buchholz relay gives an alarm so that the transformer can be disconnected before incipient fault grows into a serious one. When a serious fault (such as short circuit between phases or turns, puncture of bushings insulators etc.) occur in the transformer, pressure in the tank increases. The oil rushes towards the conservator, while doing so it passes through the Buchholz relay. The baffle (or plate) in the relay get pressed by the rushing oil. There by closing mercury switch, this in turn closes the trip circuit of circuit breaker. There after the transformer is removed from the service. For the fault above oil level, this relay is ignorant. Buchholz relay gives an alarm when the oil level reduces below a certain level due to leakage of transformer oil. There can be false operation of relay by operation of relay by vibrations, earth quakes, mechanical shocks to the pipes, sitting of birds etc. it is slow in operation, minimum operating time is 0.1 second, average time is 0.2 seconds. MAINTANANCE OF TRANSFORMER While collecting oil sample from equipment through sampling clock, allow small quantity of oil to be drained out initially and then collect the oil in the bottle for testing purposes. Before conducting oil test, cool the sample and remove any air bubbles present. Oil sample taken for testing should be collected in dry bottle through the cocks provided in the equipment and tested in standard testing equipment. All air bubbles should be removed by a clean stirrer. Test For new oil as per I.S.335 of 1985 For used oil as per I.S.1966 of 1983 1. Breakdown voltage KV (dielectric strength) 50KV (rms) 50 KV 2. Specific resistance at 27o C (ohm cm) 500X10 12 3. Water content 50PPM 25PPM 4. Die electric dissipation factor(tan delta at 90 o C) 0.005 0.2 5. Neutralization value mg.of KOH/gm of oil 0.03 0.05 6. Inter facial tension N/M at 27 o C 0.04 0.018 7. Flash point 140o C 125o C 8. Sludge 0.1 percent by Wt No sediments precipitable sludge should be detectable

RECOMMENDED MIN INSULATION RESISTANCE FOR TRANSFORMER WINDINGS Rated voltage of the winding Min. Safe Insulation Resistance in Mega Ohms (temperature during testing) 30o C 40o C 50o C 60o C 66KV and above 600 300 150 75 22KV and 33KV 500 250 125 65 6.6KV and 11KV 400 200 100 50 Below 6.6KV 200 100 50 25

GAS ANALYSIS OF BUCHHOLZ RELAY (IS 3638-1966) 1) Examine buchholz relay for the collecting gas. 2) Note the record the quantity and colour of gas collected. A colourless accumulation usually indicates the presence of air. 3) Release a small quantity of gas and smell. Peculiar smell other than oil smell is not desirable. 4) Prepare silver nitrate solution of any concentration in a wolf bottle (the solution must be clear) 5) Allow sum quantity of gas bubble through this clear solution of Silver Nitrate. 6) a) if there is no change in the colour of the solution, it generally indicates that the gas is merely air. b) Whitish precipitation – Decomposition of water c) Yellow precipitation – Decomposition of wood d) Deep grey gas of over heated oil due to burning of iron. e) Black gas of decomposed oil due to electric arc. 7) If a precipitate is obtained, thorough examination of the transformer should be made at the earliest opportunity. Get the dissolved gas analysis done before thorough inspection of transformer to detect incipient faults. KEY GAS METHOD Presence of gas Indication Methane,H2 PD (over stressing of insulation, cavities in insulation, poor impregnation) Methane, Ethane Low temperature over heating Ethylene Thermal fault Acetylene, H2 Arcing fault(short circuit in winding, break down between winding) CO,CO2 Overheating involving cellulose

RECOMMENED MAINTANANCE SCHEDULE FOR TRANSFORMER ITEM TO BE INSPECTED INSPECTION NOTES FREQUENCY ACTION REQUIRED 1 Oil Check for dielectric strength and water content Half yearly Take suitable action to restore quality 2 Oil level weekly If low, top up with dry oil examine transformer for leakage 3 Load and Voltage Check against rated figures Daily 4 Bushings Examine for crack and dirt Quarterly Clean or replace 5 Relays, alarm and circuit Examine relays and alarm contacts yearly Clean components, replace contacts and fuses 6 Earth Resistance Yearly Take suitable action if resistance is high 7 O.L.T.C. Overhauling Check OLTC for proper functioning Quarterly Clean and grease all moving contacts check oil in the diverter arrangement. 8 Buchholz relay Check contacts and floats Monthly Rectify or replace defective contacts

INSTRUMENT TRANSFORMERS: The lines in the substations operate at high voltage and carry current of thousand of ampere. The measuring instrument and protective devices are designed for low voltages (generally 230V) and currents (about 5A). Therefore, they will not work satisfactorily if mounted directly on the power lines. This difficulty is overcome by installing instrument transformer on the power lines. The function of these instrument transformers is to transfer voltage or current in the power lines to values which are convenient for the operation of measuring instruments and relays. There are two types of instrument transformers viz. (i) Current Transformer C.T. (ii) Potential Transformer P.T. CURRENT TRANSFORMER (C.T) A current transformer is essentially a step-up transformer which step down the current in a known ratio. The primary of this transformer consist of one or more turns of thick wire is connected in series with the line. The secondary consist of a large number of turns of fine wire and provides for the measuring instruments and relays a current which is a constant fraction of the current in the line. Suppose a current transformer rated at 100/5A is connected in the line to measure the current. If the current in the line is 100A, then current in the secondary will be 5A. POTENTIAL TRANSFORMER (P.T) It is essentially a step down transformer and step down the voltage in a known ratio. The primary of this transformer consist of a large number of turns of fine wire connected across the line. The secondary winding consist of a few turns and provides for measuring instruments and relays a voltage which is known fraction of the line voltage. Suppose a potential transformer rated at 66KV/110V is connected to a power line. If line voltage is 66KV, than voltage across the secondary will be 110V. INDICATING INSTRUMENTS: There are several indicating instruments (e.g. ammeters, voltmeters, energy meters etc.) installed in a substation to maintain watch over the circuit quantities. The instrument transformers are invariably used with them for satisfactory operation. CONTROL PANEL : All indicating instruments are mounted on control panels for recording and monitoring purpose. CIRCUIT BREAKER: A circuit breaker is an equipment which can open or close a circuit under normal as well as fault conditions. It is so designed that it can be operated manually (or by remote control) under normal conditions and automatically under fault conditions. For the latter operation, a relay circuit is used with a circuit breaker. Generally air-blast, vacuum and SF6 circuit breakers are used. 110KV CIRCUIT BREAKERS

          110KV circuit breakers of the substation are SF6 gas CB of make Crompton Greaves. The three phases have their own mechanism and air reservoirs interconnected pneumatically operated. The control panel is mounted in the middle phase. The pneumatic operating mechanism is operated by compressed air for opening and by spring force for closing. Hence it is important to monitor the air pressure.
                 The Breaker can be switched on or off by operating the breaker control switch (TNC) in the control panel in remote mode, and by operating TNC in the breaker mechanism box in local mode. Any change in status of CB closed through control switch is accompanied by auto trip lamp. It can be reset by turning the control switch to trip position. Trip relays should be reset for closing CB.

AIR BLAST CIRCUIT-BREAKERS In air blast circuit breaker (also called compressed air circuit-breaker) high pressure air is forced on the arc through a nozzle at the instant of contact separation. The ionized medium between the contacts is blown away by the blast of air. After the arc extinction, the chamber is filled with high pressure airs, which prevent restriking of arc. Air blast circuit- breakers are used today from 11KV to 1100KV, for various applications. They offer several advantages such as: (a) Faster operation (b) Suitable for repeated operation (c) Auto reclosure (d) Unit type multi-break construction (e) Simple assembly (f) Less maintenance etc.

            A compressor plan is necessary to maintain high air pressure in the air receiver. Air-blast circuit breakers are especially suitable for railways and arc furnaces where the breaker operates repeatedly.

For opening operation, the high pressure air (30Kg/m2) is admitted into the arc extinction chamber. It pushes away the moving contacts against spring pressure. In doing so, the contacts are separated and the air blast takes away the ionized gases along with it and assists arc extinction. The high pressure air has higher dielectric strength than that of atmospheric pressure. Hence a small contact gap of a few centimeters is enough. SF6 CIRCUIT BREAKERS SF6 gas circuit breakers are well suited for high-voltage systems. Sulpher Hexafluoride (SF6) is an inert, heavy gas having good dielectric and arc extinguishing properties. The dielectric strength of the gas increases with pressure and is more than that of dielectric oil at a pressure of 3Kg/cm2. This gas is now being very widely used in electrical equipment like high voltage metal-clad switch gear, capacitors, circuit breakers, current transformers, bushings, etc. The following are the properties of SF6 gas: 1. It is highly inert gas 2. It is an electro negative gas and absorbs free electrons 3. Superior arc quenching property 4. It is heavy 5. Good dielectric strength 6. Good arc extinguishing property.

Advantages of SF6 circuit breakers: 1. The arc time is small 2. The contact erosion is less 3. Dielectric strength of this gas remains same as no carbon is formed during arcing. 4. Its operation is not effected by the atmospheric condition 5. Compact in size due to high dielectric strength of SF6 6. Noise less operation due to low pressure and high velocity 7. Low maintenance cost 8. No fire problems because SF6 is non-inflammable. 9. No moisture problem as the gas is not exposed 10. Well suited for mines etc.

Construction: it mainly consists of a fixed contacts and moving contacts enclosed in an arc interrupting chamber. Both fixed and moving contacts are made of hollow cylindrical in shape. The moving contacts are provided with holes to permit the SF6 gas to let out through these holes after flowing along and across the arc. Working: under normal working conditions, the fixed and moving contacts are closed and are surrounded by SF6 gas. Due to some fault the moving contacts by a moving mechanism an arc is established between the contacts immediate after separation. When the moving contacts moves soon after the valve opens to permit SF6 gas at high pressure of 14Kg/cm2 from the gas reservoir. This high pressure gas while moving into arc chamber absorbs the free electron in the arc path and try to lengthen the arc. As a result of this the medium between the contacts quickly builds high dielectric strength and causes arc extinction. As soon as the arc is extinguished, the valve closes by a set of spring action. VACUUM CIRCUIT BREAKERS (VCB) In such breakers, vacuum is used as the arc quenching medium. Since vacuum offers the highest insulating strength, it has far superior arc quenching properties then any other medium. For the example when contacts of a breaker are opened in vacuum, the interruption occurs at first current zero with dielectric strength between the contacts building up at a rate thousands of times higher than that obtained with other circuit breakers. Principle: the production of an arc in vacuum circuit breaker and its extinction can be explained as follows: when the contacts of the breaker are opened in vacuum, an arc is produced between the contacts by the ionization of metal vapours of contacts. However, the arc is quickly extinguished because the metallic vapours, electrons and ions produced during arc rapidly condense on the surfaces of the breaker contacts, resulting is quick recovery of dielectric strength. The reader may note the salient features of vacuum as an arc quenching medium. As soon as the arc is produced in vacuum, it is quickly extinguished due to the fast rate of recovery of dielectric strength in vacuum. Construction: it mainly consists of a fixed contact, moving contact and vapour condensing shields mounted inside a vacuum chamber. The movable member is connected to the control mechanism by stainless steel bellows. This enables the permanent scaling of the vacuum chamber so as to eliminate the possibility of leak. A glass vessel or a ceramic vessel is used as the outer insulating body. The arc shield prevents the deterioration of the internal dielectric strength by preventing metallic vapours falling on the inside surface of the outer insulating cover. Working: when the breaker operates, the moving contact separate from the fixed contact and an arc is struck between the contacts. The production of arc is due to the ionization of metal ions and depends very much upon the material of the contacts. The arc is quickly extinguished because the metallic vapour, electron and ions produced during arc diffused in a short time and seized by the surface of moving and fixed members and shields. Since vacuum has very fast rate of recovery of dielectric strength, the arc extinction is vacuum is faster and occurs with a short contact separation. Advantages: 1. They are compact, reliable and have longer life. 2. They are no fire hazards 3. There is no generation of gas during and after operation 4. Maintenance is low and are quiet in operation 5. This are successfully withstand lightning surges 6. This have low arc energy 7. They have low inertia and hence require smaller power for control mechanisms. Protections for CB 1. Low air pressure alarm – Gives alarm when the air pressure goes below 13Kg/cm2 2. Low gas pressure alarm - Gives alarm when the gas pressure goes below 4.5Kg/cm2 3. CB Lockout – When the air pressure falls to 12Kg/cm2 Pole discrepancy relay – If any of the pole is not closed, the other poles will be tripped acting this relay. The relay is provided in the CB cubicle of middle phase (yard). An auxiliary relay is mounted on the relay panel. SWITCH GEAR: Different switch gear equipment is used in sub-station for satisfactory operation such as  Fuses  Relays  Isolators etc. RELAYS: INDUCTION TYPE OVER CURRENT RELAY These relays operate on the principle of induction motor operation. Construction: it mainly consists of a metallic disc which is free to rotate between the poles of two electromagnet. The upper electromagnet has a primary and a secondary winding on its central limb. The primary is connected to the secondary of a current transformer in the line, which is to be protected and provides with tapings. These tapings are connected to a plug setting bridge by which the number of turns to be used can adjust in order to have the desired current setting. The secondary winding is energized by the induction effect and is wound on the central limb just below the primary winding. The emf induced in the secondary winding supplies current to the winding on the lower U magnet. Principle of Operation: under faulty conditions, the proportionate current flows through the primary and secondary windings of the relay according to the current settings. The upper magnet establishes a flux of 1 and the lower magnet establishes another flux of 2 in the disc. The two fluxes 1 and 2 are sufficiently displaced from each other to produce the eddy current in the disc. The eddy current produces a torque in the disc and hence it starts rotating. The speed of the disc depends on the value of fault current. When the deflecting torque is produced on the disc, the spindle of the disc carries a moving contact which bridges two fixed contacts on the trip circuit after disc has rotated through some angle. The disc rotate through an angle which is adjustable between O0 to 36O0 . by adjusting this angle the travel of the moving contact can be adjusted so that the relay can be given any desired time setting which is indicated by a pointer on a time setting dial . as soon as the trip circuit closes, the circuit breaker operating mechanism is actuated and it operates for the opening operation. DISTANCE RELAY OR IMPEDENCE RELAY Distant relays differ in principle from other forms of protection, in that their performance is not governed by magnitude of the current or voltage in the protected circuit but rather on the ratio of these two quantities. In distant relays, there is a balance between voltage and current. The ratio of which can be expressed in terms of impedance. Impedance is an electrical measure of distance along a transmission line. The relay operates when the ratio V/I is less than predetermined value. WAVE TRAP: It is communicating equipment between stations. The same power lines are used for the communication waves at different frequencies. So wave trap isolates the communication waves from power waves and transfers. In Kerala now only there is some substation the wave trap system is present. In Westhill power station it is out of work. In Kozhikode district it presents in Nallalam substation and Chevayur substation. Normally telephone line is used for communication between stations. A special range of band is permit for this purpose. So there is no lag in the communication. STATION TRANSFORMER/ STATION AUXILLARY: This transformer supplies power to the station requirements like lighting, DC charging, fans, AC etc. it is a separate transformer for station purpose. Normally its rating is 11KV/230V. LIGHTINING ARRESTORS: Varieties of lighting arrestors are used for protecting transformers, lines etc. EARTHING: Every equipment in the substation is earthed for safety. The main two types of earthings are (i) Pipe earthing (ii) Plate earthing To provide earthing for pole-mounted substations as well as distribution poles, pipe earthing is sufficient. Plate earthing is used for large installation such as sub-stations, transmission towers etc. the maximum value of earth resistance for satisfactory operation are given below: Large power station - 0.5 Ω Major sub-stations - 1.0 Ω Small sub-station - 2.0 Ω In all other cases - 8.0 Ω PIPE EARTHING: In this method of earthing, a 38 mm internal diameter, perforated galvanized pipe of length 2.5m is placed vertically is a permanent wet soil. Where the rock is encountered at a depth of less then 2.5m electrode may be buried inclined to the vertical. The inclination should not be more than 300 from the vertical. The pipe is surrounded by the pieces of coke or charcoal and salt in alternate layers of about 15cm around the pipe is used to decrease the earth resistance. Another pipe of 19mm diameter and length 1.25m is connected to the buried pipe through reducing socket. At the top of 19mm pipe a funnel is fitted and is fastened in a cement concrete work. For effective water should be poured 2 to 4 buckets now and then through funnel particularly in the earth wire is carried in a GI pipe of 12.7mm diameter at a depth of 60cm from the ground level. If is necessary to reduce the depth of burial of an electrode under unavoidable circumstances, this can be done without increasing the earth resistance. It is achieved by using a number of electrodes connecting them together. The distance between two electrodes in such case should not less than twice the length of electrode. A cast iron cover is hinged in a small masonary work on the top of the earthing facilities its identification and periodical checking. PLATE EARTHING: In this type of earthing a copper plate of dimensions 60cm X 60cm X 3.15mm or a GI plate of 60cm X 60cm X 6.3mm is used as an earth electrode. Plate electrode should be buried with its face vertical such that the top edge is at a depth of not less than 1.5m below the surface of the ground. The electrode is surrounded by alternate layers of broken pieces of coke or coal and salt. The earth wire is securely bolted to an earth plate with the help of a bolt, nut and washer made of copper for copper electrode and GI for GI electrode. A cast iron cover is provided at the top of the earthing with a hing to facilitate its identification and for periodic checking. When resistance of one plate earthing is higher than the required value more than one plate should be earthed and connected together. CABLES: For protective relays and instruments the cables are used. BATTARY ROOM: Every substation will have battery room for supplying DC to relays. Indications, lightening systems etc. normally Lead-Acid battery of 2.2 volt, 55 numbers are used for 110 volt.

FIRE RIGHTING EQUIPMENT: Fire fighting equipment is used for safety in case of fire. Electrical fire equipment is different from ordinary fire equipment. FIRE PROTECTION Carbon dioxide and DCP type fire extinguishers and fire buckets filled with sand are provided in the control room and in the yard for quenching of fire in the station (make: Rainbow industries). There are 2 sets of 2x22.5Kg trolley mounted CO2 fire extinguishers (1 set in control room and 1 set in yard), 4 Numbers of 22.5Kg CO2 fire extinguishers, 4Nos of 5Kg DCP & CO2 fire extinguishers at the substation. CO2 Fire extinguisher is used to put out fire involving oil (class B) and Gas (class C). This is an upright type fire extinguisher. These fire extinguishers are operated by a simple wheel valve mechanism through which the rate of discharge can be regulated. To prevent bursting of cylinders due to temperature pressure fluctuations a safety disc is provided on the valve. Method of Operation: Remove the safety pin and turn the wheel in anti clockwise direction and direct the gas to the seat of fire with the help of the discharge horn. DCP Fire extinguisher is used to put out fires involving oil (class B) and Gas (class C). Method of Operation: Withdraw the hose from its seat, swing back the safety clip and press down the knob with the palm. This releases CO2 gas from the cartridge and pressurizes the extinguisher body. This pressure pushes the dry powder out which comes out as a stream. The stream of powder is directed towards the source of fire. ADVANTAGES OF HIGH VOLTAGE AC 1. Electrical losses (I2R or copper loss) will be less. 2. Voltage regulation will be improved. 3. The material required for conductor is reduced. 4. The transmission efficiency increased. 5. Future extension flexibility is more. 6. With high voltage system more power can be transmitted. DISADVANTAGES OF HIGH VOLTAGE AC 1. Corona loss will be more. 2. Heavy and tall supporting structures. 3. Insulation and switching problems. 4. Ferranti effect. DUTIES AND RESPONSIBILITIES OF OPERATOR 1. Be in complete charge of station during the period of shift duty 2. Carry out operations as per the standing instructions 3. Issue and cancel permits to work in the lines connected to substation as well as substation equipments 4. Take readings of the instruments and post them in the log sheets as per standing instructions and enter details of operation carried out in the diary 5. Attend telephone messages (transmission & reception). Attend telephone calls promptly and politely. 6. Report Station Engineer immediately if any abnormalities are noticed in the station 7. Assist the Station Engineer in charge of the station in maintenance work 8. Assist the Station Engineer to prepare and forward the monthly log sheets 9. Carry out any other work that may specifically be assigned to him/her

DUTIES AND RESPONSIBILITIES OF SHIFT ASSISTANT 1. Assist the operator on duty as per specific instructions 2. Report promptly to the operator on duty any abnormality noticed by him/her. 3. Attend to miscellaneous types of works like starting/stopping of pump sets, compressor etc, oiling and greasing equipments; renew fused bulbs etc as per the instruction of operator on duty. 4. Carry out any other work that may specifically be assigned to him/her. 5. Assist the superior in charge of the Station in Maintenance works.

OPERATING PROCEDURES On taking charge of shift duty, the operator should inspect the yard, station battery, battery charger, control panels and check the healthiness of trip circuits, control DC, annunciation DC and the conditions should be recorded in operator’s diary.

The general operations at this Substation are listed as follows.    

1. When 11KV outgoing feeder trips Accept alarm. Note down the relay indications, and reset the relay and alarm circuit. Charge the feeder after 3 minute. If feeder trips, give another test charge after 3 minutes. If the feeder again trips, declare the feeder as faulty and inform district control room & distribution sections concerned, preferably as a message. However, if the operator is convinced that the fault persists or is heavy the feeder need not be test charged. Ensure all phase currents are balanced after test charging of the feeder. 2. When 11KV incomer trips Cancel alarm. Tripping of incomer may probably be due to the none tripping of faulty 11KV feeder. Switch off the bus coupler & all 11KV outgoing feeders. Inspect for any abnormality. If no abnormality is noticed, charge the incomer. If it stands, charge the feeder breakers one by one. The operator can identify the faulty feeder which was not tripped by tripping of incomer. Cancel the alarm. Reset the relays and charge the incomer followed by outgoing feeders one by one except the faulty feeder. If the incomer trips again during the above operation report the matter to station Assistant Engineer, Assistant Executive Engineer and District control room. Care should be taken to avail station auxiliary supply through non faulty incomer feeder. 3. When Transformer trips a) When Back up protection acts (O/C & E/F)– Cancel alarm. Switch off bus coupler & out going feeders of the Transformer followed by the incomer. Inspect the Transformer for any visible abnormalities. If no abnormality is noticed, charge the Transformer. If it stands charge the incomer followed by the outgoing 11KV feeders one by one. b) When Buchholz relay acts– Cancel alarm. Note down the relay indications and reset the relays. Do not charge the Transformer. Inform the matter immediately to station AE & AEE. c) When restricted earth fault relay acts (on EHV or HV side) – Do not charge the Transformer. Switch off and isolate the Transformer on both side and report the matter immediately to station AE & AEE. d) When differential relay acts – Do not charge the Transformer. Isolate the Transformer on both sides and report to station AE & AEE. e) When winding temp. Relay acts – Note down the winding temp. Switch off 11KV feeders. Allow Transformer to cool down. Charge and load Transformer. (The operator should take action well in advance when it is noticed that the temperature is increasing/high, without waiting till the transformer is tripped. Switch on cooler fans where forced cooling is provided, or other means to reduce temperature) f) When pressure relief valve acts – Do not charge the Transformer. Report to station AE & AEE.

1. Incoming (110KV) Supply failure:

        If the total incoming supply failure exceeds two minutes all the outgoing 11KV feeders may be switched off. Lower tap position of the Transformer. After collecting the switched off information of all 11KV feeders from feeding stations the same may be conveyed to Nallalam Substation & G/S O/Ds 

SAFETY GUIDELINES FOR OPERATING PERSONNEL 1. Operating Staff should be mentally alert, should concentrate on the work 2. Operating Staff should not do any work for which he is not qualified and where not authorized. If any one is doubt as to the work assigned to him he should ask for instruction from the superior officer. 3. Under no circumstances should the operating person hurry or take unnecessary risks when working in a hazardous position. 4. Report unsafe condition and equipment defects for immediate attention. 5. No operating staff should smoke or bring naked flames near Oil Filled Equipments and Battery Room. 6. Be well aware of type and operation of fire extinguishers available 7. All voltages should be considered dangerous, even though it may not be high enough to produce a serious shock. Bare fingers or hands should not be used to check whether a circuit is live 8. No signal systems like waving hands or flags should be resorted to for convey instructions. 9. Aware of safety rules and become safety minded. 10. Work, safely, orderly, and with general care. 11. Study safety practices like first aid, artificial respiration method etc. 12. Treat the injuries immediately. 13. Always exercise good house keeping. 14. Handle materials with care; lift and carry properly. 15. Keep all tools clean and use them properly. 16. Select right tools and keep in good working condition. 17. Study the job, determine what to do and how to do, plan well. 18. Do only the Do’s, not the Don’ts. 19. Never substitute assumptions for facts. 20. Visitors should be prohibited from any live part. 21. While on duty practical jokes or daring men to take chances while on job should not be done. 22. Serious Action will be taken against those who disregard the rules and cause accidents. Since the Operator is the full in charge of the Station for the particular Shift, all Gate Keys should be under his custody. It has to be ensured that nobody should enter the yard without the permission of the Operator. GENERAL INSTRUCTIONS TO THE OPERATORS 1 The operator is in charge of the station including control room, switch yard and premises during his/her shift. 2 Operators and shift assistants should wear tight dress during duty hours. 3 Carry out the operations as per standing instructions. 4 Ensure that the control room, switch yard and premises are kept neat and tidy. 5 Discipline should be maintained in the control room. 6 The operator should be familiar with the system layout, the equipments, wiring diagram of the station and the operating instructions. 7 Check all equipments for any change from normal, before taking charge. 8 Go through operator’s diary, message book and permit book to get updated about the operational position before starting each shift. 9 Keep a constant watch over the equipments and panels and report any abnormalities to the station engineer. 10 Record all operations, system operating conditions and weather conditions correctly in proper time and sequence in the diary. 11 Check oil levels of transformers, CTs, PTs etc and report to station AE if found low. 12 Be familiar with area fed by the outgoing feeders and also possible interconnections between feeders and substations and back feeding possibilities. 13 Whenever a feeder is declared faulty, inform the same immediately to District control room and section officer concerned. 14 Maintain voltage within 10.8 to 11KV unless there is voltage restriction. 15 Take battery readings daily as per standing instructions. 16 Switch off the battery charger at 8 hrs daily for 1 hr. Note down the voltage of the pilot cell (No 27) and other 7 cells per day on the battery maintenance register. Take the battery voltage at 15 minits interval. The voltage should not reduce by 10%. 17 Synchronize the station clock time with the time at 220KV Substation Nallalam at 00Hrs. 18 During morning peak and evening peak hours, half hourly readings should be taken.

      Morning peak duration:  5hrs to 8hrs
      Evening peak duration: 18hrs to 22.30hrs

19 Operator should inspect the yard during peak hrs and check whether any red hot or abnormal condition is there. 20 Operator should be familiar with the emergency hand operations of circuit breakers, tap changers, spring charging motors etc and procedures to be followed in case of fire/accidents. They should be familiar with first aid, artificial respiration and safety procedures. 21 Operators are responsible for maintaining water supply from open well, switching on and off yard and colony lights. 22 Prepare daily interruption report in the prescribed form. 23 Operators should ensure safe custody of tools kept in control room and all drawings and manuals and should not be given to outsiders without the permission of Station Engineer. 24 Since the Operator is the full in charge of the Station for the particular Shift, all Gate Keys should be under his custody. It has to be ensured that nobody should enter in the control room and yard without the permission of the Operator. 25 During the tripping of 11KV feeders the duration of test charge should be maintained at an interval of 3minutes. Phone message if any should be conveyed immediately over phone if Station Engineer is not available at office.

Procedure for issuing permit to work (PW) on Power transformers: 1 Receive request for PW from station AE/AEE 2 Ensure that the total 11KV load is within the safe loading limit of the other transformer. 3 Switch Off 11KV incomer VCB on which permit is requested. 4 Switch off 110KV breaker of the required transformer. 5 Rack out incomer VCB and open 110KV bus isolator of the transformer. 6 Earth the transformer. 7 Prepare PW in the prescribed form which should contain Name of the transformer, Operations carried out by the operator. The issue of PW has to be acknowledged by the officer concerned in the book copy as well as in the issuing copy. 8 Proper caution boards should be provided on the equipment. Record all Operations in chronological order in operators register. Total shut down of the Substation: 1 Obtain sanction from Executive Engineer, LD, Kalamassery & Assistant Executive Engineer, district control room, Kozhikode. 2 Avail & ensure station auxiliary supply through 11KV Aredathpalam feeder. while availing the shut down of the Substation it should be ensured that the station auxiliary is available so as to maintain station battery and pneumatic pressure of 110KV Crompton & Greaves breaker. 3 S/Off 11KV feeders & isolate yard AB’s of out going 11KV feeders to issue NBC so as to back feed the 11KV system scheduled by district control room. 4 Issue NBC to Koyilandy Substation OD so as to back feed 110KV NLMU feeder. 5 S/Off HV & LV side circuit breaker’s of transformers. 6 S/Off all 110KV incomers and isolate. Record all operations in chronological order. To energize the station: 1 Close all incomer line isolators. Close CHWH bay isolator after cancelling NBC and getting confirmation from Koyilandy Substation. 2 Charge all 110KV feeders. 3 Charge HV side of transformer. 4 Charge 11KV incomer. 5 Charge 11KV outgoing feeders after canceling NBC on the respective feeders and getting confirmation from distribution sections concerned. AUTHORIZED PERSONS Permit work should be given to authorized persons as detailed below. 1 11kV, 22kV, 33kV Lines & Equipments. - Not Below the Rank of Sub Engineer 2 Lines & Equipment of 66kV & above - Not below the Rank of Assistant Engineer.

AUTHORISED PERSONS TO ENTER THE CONTROL ROOM Station Engineer Shift staff Maintenance staff Authorized persons to take permit–to-work NO OTHER PERSONS OTHER THAN THE AUTHORISED PERSONS SHOULD NOT BE PERMITED TO ENTER THE CONTROL ROOM WITH OUT PRIOR PERMISSION FROM THE STATION ENGINEER This gives you general operating instructions to be followed at this Substation. All operating persons at this Substation should go through this and acknowledge the same. An operator should be alert, know the problem and act immediately and accordingly. DISTRIBUTION The conductor system by which electrical energy is conveyed from a substation to the consumer is called a distribution system. The distribution system at a medium voltage is called primary distribution and at a low voltage is called secondary distribution.

Primary distribution: Power received by major substation at high voltage through transmission lines is stepped down to voltages somewhat higher than general utilization levels and conveyed to different substation to handle large blocks of power than the average low voltage consumer uses, is called a primary distribution or a high voltage distribution. The most commonly used nominal voltage is 11KV. Secondary distribution: At distribution substations, primary voltage is stepped down to 440/230 volt and is feed to consumers. This part of distribution of power is called secondary distribution or low voltage distribution