12

Materials and Components

AC POWER SUPPLY SYSTEM

Introduction:

Low voltage AC supply both single and three phases, is needed in a substation for internal use for several auxiliaries.

Supply Source for Auxiliary AC System:

a) 415 V three phase supply from the distribution transformers.

b) Station transformers connected to the 11 kV or 33 kV station bus.

c) In case of main power Transformers, where tertiary winding is available station Power supply can be availed with one auxiliary Transformer connected to the tertiary winding.

d) From the station transformer low voltage supply is extended to the indoor AC Distribution panel through duplicate cables. Duplicate feeds are given to important loads from the ac distribution panels through outlets which are controlled by switch fuses or MCBs.

e) In case of shutdown of entire substation Diesel Generator set ensures AC auxiliary supply for charging protective equipments. Changeover scheme shall be provided in the AC distribution panel.

Auxiliary Low Voltage (LVAC) Supplies:

The auxiliary AC system in a substation supplies to following electrical auxiliaries

1. Illumination 2. Battery charging 3. Transformer cooling system 4. Oil Filtration plant 5. Transformer tap-changer drives 6. Air compressors 7. Power supplies for communication equipment 8. Crane9. Breakers/ disconnect switch motors 10. Fire protection system 11. Space heaters in cubicles and Marshalling Kiosks 12. Air conditioning/Ventilation equipment.

Auxiliary system is at two or three A.C voltages such as 415V, 6.6 kV, 3.3 kV, and 11 kV.

Auxiliary AC system comprises the following:

Auxiliary step-down transformer in the substation

High voltage switchgear

LV AC switchgear

Load control centers

Power cables

A.C auxiliary distribution system

AC Distribution System:

This is made up of 415V load control centers and LV distribution system. This system also shall have automatic load transfer system.

LT Transformers:

Ratings of LT Transformers:i. 33/0.433 kV, 800, 630 & 250 kVA ii. 11/0.433 kV, 630 & 250 kVATechnical Requirements:

Core:

The core shall be constructed from high grade, non aging, and cold rolled grain-oriented silicon steel laminations. The maximum flux density in any part of the cores and yoke at normal voltage and frequency shall be such that the flux density at any tap position with 10% voltage variation from the voltage corresponding to the tap shall not exceed 1.9 wb/sq.m.

Windings:

The conductor shall be of electrolytic copper, free from scales and burrs.

Insulating Oil:

The oil supplied with transformer shall be unused and have the parameters for unused new oil conforming to IS: 335 while tested at oil contractors premises. No inhibitors shall be used in oil. Ten percent extra oil shall be supplied for topping up after commissioning in non returnable containers suitable for outdoor storage.

Terminal Arrangement:

a. Bushing terminals shall be provided with suitable terminal connectors of approved type and size for cable/overhead conductors termination of HV side and cable termination on LV side.

b. The neutral terminals of 433 V winding shall be brought out on a bushing along with the 433 volt phase terminals to form a 4 wire system for the 415 volt. Additional neutral bushing shall also be provided for earthing.

Off Circuit Tap Changing Equipment:

The tap change switch shall be three phase, hand operated for simultaneous switching of similar taps on the three phases by operating an external hand wheel.

Marshalling Box:

A metal enclosed, weather, vermin & dust proof marshalling box shall be provided with each transformer to accommodate temperature indicators, terminal blocks etc. It shall have a degree of protection of IP 55 as per IS: 2147.

Cable Boxes:Whenever cable connections are required, suitable cable boxes shall be provided and shall be air insulated. They shall be of sufficient size to accommodate Purchaser's cables and shall have suitable removable side/top cover to facilitate cable termination and inspection. Cable boxes shall be dust & vermin proof.Fittings:

The following fittings shall be provided with each transformer1 Conservator with drain plug and oil filling hole with blanking plate

2 Plain oil Gauge3 Silica gel Breather4 Pressure Relief vent5 Pocket on tank cover for Thermometer6 Valves7 Earthing Terminals8 Rating & Terminal Marking Plates9 Lifting Lugs10 Rollers11 Air Release PlugThe fittings listed above are only indicative and any other fittings which generally are required for satisfactory operation of transformer are deemed to be included.Technical Parameters:

Sl.NoDescriptionParameters

a. TypeTwo winding

b. ServiceOutdoor

c. Number of PhasesThree

d. Frequency50 Hz.

e. Type of coolingONAN

f. Rating250 kVA, 630 kVA and 800 kVA

g. Ratio11/0.433 kV 33/o.433 kVA

h. Impedance at 750C with tolerance0.05 ( 10%

i. DutyContinuous

j. Over loadAs per IS: 6600

k. Maximum Tem. Rise over 500C ambient

i. Oil (temp. rise measurement by thermometer)

ii. Winding (temp. rise measured by resistance method)500C

550C

l. Windings33 kV, 630kVA/ 250 kVA33 kV, 800kVA11 kV, 630kVA/ 250 kVA0.433 kV

m. 1. 1.System apparent short circuit level (kA)As per IS: 2026 (Part-I)

n. 1. 2.Winding connectionDeltaDeltaDeltaStar

o. 3. Vector groupDyn 1

p. 4. InsulatorUniform

q. 5. Insulation level l(kV)

a. Power frequency test level (kV rms)

b. Basic impulse level (kV peak)36

70

17052

95

25011

28

750.433

2

--

r. 6. Highest voltage (kV) for each winding365212--

s. 7. Method of earthingSolid earthed

t. Tap Changer

u. 1. Tap range+5%/-10% in steps of 2.5% on HV side

v. 2. Tap controlOff circuit tap

w. HV Bushings800 KVA630 KVA

x. 11 kV33 kV

y. 1. Rated voltage, kV521236

z. 2. Rated current, kV100 A

aa. 3. Basic impulse level (kV)25075170

ab. 4. Wet and dry power frequency withstand voltage (kV rms)952870

ac. 5. Minimum total creepage distance (mm)1300300900

ad. 6. MountingTank/Transformer body

ae. LV and Neutral bushing

af. 1.Rated Voltage (Volts)110011001100

ag. 2.Rated Current (amps)200010001000

ah. Terminal Details

ai. 1.High VoltageSuitable for 33 kV/11 kV

Cable

aj. 2.Low voltage phase and neutralCable box

ak. Minimum Clearances (mm)

in Air33 kV, 630kVA/ 250 kVA33 kV, 800kVA11 kV, 630kVA/ 250 kVA0.433 kV

al. 1.Phase to phase35053028025

am. 2.Phase to Earth32048014025

A.C Circuits:

Following are the A.C circuits present in a substation.

1. Auxiliary L.T Circuits 2.OLTC Control Circuits

Auxiliary L.T Circuits: L.T Distribution Circuits to VCBs for Spring Charging motors, space heaters and indications ( in some Breakers)

L.T Supply for Operation of OLTCs of Power Transformers

L.T Supply to Battery Charger L.T Supply to Air Compressors

L.T Supply to Yard Lighting L.T Supply for Sub Station Control Room, water Pumping etc.

OLTC Control Circuits of Power Transformers:

Local (Electrical) tap changing circuit and Remote tap changing circuit (Individual)

Simultaneous Remote tap changing circuit for Power Transformers in parallel (Master and follower circuits)

Example:

A typical example for A.C auxiliary system for a 220/33kV substation is given below:

Diesel Generator Set:

Diesel generator set is one of the auxiliary systems present in a substation. The diesel generator is provided in important substations and also in power stations to avoid complete blackout in case of system failure.

DG set will be equipped with following equipment:

a) Diesel engine complete with all accessories

b) An alternator directly coupled to the engine through coupling complete with all accessories.

c) Automatic voltage regulator

d) Complete starting arrangement, including two batteries and chargers.

e) Base frame and foundation bolts.

f) Day tank of 990 litres capacity

g) Oil pump for transferring to day tank.

h) Engine cooling and lubrication system.

i) Engine air filtering system

j) Exhaust silencer package

k) Set of GI pipes, valves, strainers, unloading hose pipes as required

l) All lubricants, consumable ,touch up paints for filling, testing and commissioning at site .The fuel oil for first commissioning will also provided by the contractor.

m) AMF (Auto mains failure) panel for control, metering and alarm.

n) Acoustic insulation for DG set as per the norms of Central Pollution Control Board.

System Design:

The diesel generator units shall be installed indoors. Suction of air shall be from indoor and exhaust will be let out outside the atmosphere, condensate traps shall be provided on the exhaust pipe.

The fuel used shall be High Speed Diesel oil (HSD) or Light Diesel Oil (LDO) as per IS: 460.

The diesel engines shall be directly water cooled. Cooling of water through

Radiator and fan as envisaged.

The engine shall have closed loop lubricating system. No moving parts shall require lubrication by hand prior to start of engine or while it is in operation.Control and Instrumentation:

i Each D.G set shall be provided with suitable instruments, interlock and Protection and arrangement, suitable annunciation and indications, for proper start up, control, monitoring and safe operation of unit.

ii The D.G set sets shall be provided with automatic start facility to make it possible to take full load within 30seconds of power supply failure.

iii A three attempt starting facility using two impulse timers and summation timer for engine shall be provided and if the voltage fails to develop within 40sec.from receiving the first impulse, the set shall block and alarm to this effect shall be provided in the AMF panel.

iv One local AMF control panel along with each D.G set shall be provided. The AMF panel shall have IP-52 degree of protection as per IS: 12063. Testing facility for automatic operation of D.G set shall be provided in AMF panel

Following indication lamps shall be provided in the AMF panel:

a) Mains on

b) Alternator on

c) Charger ON/OFF

d) Breaker ON /OFF

e) Main LT supply ON/OFF

Following visual annunciations shall be provided in the panel for Reasons for set shut down .

i. Engine overheating

ii. Low oil pressure

iii. Lack of fuel

iv. Set failed to start in 30 sec. after receiving the first start impulse

v. High cooling water temperature

vi. Low level in daily service fuel tank

vii. Over speed trip

viii. Audio& visual Annunciation for alternator fault

The following accessories shall be provided in AMF panel.

i. Frequency meter

ii. 3 nos. CTs for metering

iii. 3 nos. CTs for differential protection on neutral side

iv. One DC Ammeter (0-40A)

v. One DC Volt meter(0-30V)

vi. One Volt meter selection switch

vii. One AC Voltmeter

viii. Three timers (24V DC)

ix. Two Auto /Manual selector switches

x. Two Auto /Test /Manual selector switches

xi. Eleven auxiliary contactors suitable for 24V DC

xii. One motorized potentiometer for voltage adjustment

xiii. Two sets of Battery chargers

xiv. One set phase and neutral busbars

Technical Requirements:

A typical example giving technical requirements for DG set of a 400/220 kV substation is as follows:

1. Ratings: 250kVA, 1500RPM, 0.8pf, 415V, 3phase, 50Hz frequency.

2. DG sets shall be rated for 110% of full load for 1hour/day of continuous running.

3. The output voltage, frequency and limits of variation from open circuit to full load shall be as follows:

a) Voltage variation: +/-5% of the set value .Provision shall exist to adjust the set value between 90% and 110% of nominal generator voltage of 415V

b) Frequency 50Hz +/-2%

4. Type insulation but limited to class-B for temperature rise consideration. The diesel generator and other auxiliary motor shall have epoxy thermo setting

5. The day tank of 990 litre capacity shall be provided on suitably fabricated steel platform. The tank shall be complete with level indicator marked in liters, filling inlet with removable screen, an outlet, a drain plug, an air vent, an air breather and necessary piping. The tank shall be painted with oil resistant paint and shall be erected with Indian Explosive Act of 1932.

6. Six output terminals shall be provided in alternator terminal box. The neutral shall be formed in Auto Mains Failure (AMF) panel. The generator terminal box shall be suitable to house necessary cables and should be made of non-magnetic material.

7. For transferring oil to day tank transfer pumps are envisaged. The capacity of transfer pump shall be adequate to fill the day tank in about 30 minutes.

Operation of D.G Set:Standby DG set consists of a diesel engine coupled to an alternator. The standby DG set has the Auto Mains Failure (AMF) sensing panel which senses the failure of mains supply on input bus more than the set time before starting of a D.G set. MCCB s 1 & 2 will be tripped off due to their under-voltage coil being not energized because of absence of input A.C power. Contactors in AMF panel will then close to restore power to critical loads. Mains failure is sensed on both UPS-1 and UPS-2 input buses and in case of these buses has mains failure, the DG will start and supply power to that bus via either of the contactors. AMF panel makes three successive attempts for starting the DG sets. DG set will be inhibited from staring if AMF panel selector switch is in off position. When primary power is restored and remains on for 1 to 10 minutes, the DG set will be automatically switched off.

Following instruments shall be provided with diesel engine:i. Lubricant oil pressure gauge

ii. Lubricant oil temperature thermometers

iii. Water temperature thermometers

iv. Exhaust gas pyrometer with temperature switch

v. Engine meter

DG set shall be capable of being started /stopped from remote as well as local manually. Remote START/ STOP push button shall be provided to prevent shutting down operation as long as D.G circuit breaker is closed.

The diesel generator shall commence a shutdown sequence whenever any of following conditions appears in the system:

i Over speed

ii Overload

iii High temperature of engine, cooling water and lubricating oil.

iv Low lubricating oil pressure.

v Generator differential protection

vi Short circuit protection

vii Under voltage

viii Over voltage

ix Further interlocking of breaker shall be provided to prevent parallel operation of DG set with normal stationary supply.

Tests:

The diesel generator set shall be tested for Routine and Acceptance tests as per relevant standards. The type test report for a diesel engine and alternator are to be submitted by the supplier.

Commissioning Checks:

The following commissioning checks are to be carried out at site.

Load Test:

The engine shall be given test run for a period of at least six hours. The set shall be subjected to the maximum achievable load not exceeding the specified D.G set rating. During the load test, half hourly readings of the following shall be taken.i. Ambient temperature

ii. Exhaust temperature if exhaust thermometer is fitted

iii. Cooling water temperature

iv. Lubricating oil temperature

v. Lubricating oil Pressure

vi. Colour of exhaust gas

vii. Speed

viii. Voltage, Wattage and current output

ix. Oil tank level

Insulation Resistance Test for Alternator: Insulation resistance between the coils and the alternator frame shall be measure with 500V Megger.Check for Fuel Consumption: The check for fuel consumption shall be made during the load run test.Insulation Resistance of Wiring: Insulation resistance of control panel wiring shall be checked by 500V Megger. The same shall not be less than one mega ohm.Functional Tests:

On control panel,On starting provision on the engine,On all field devices,On AVR and speed governor.

Measurement of Vibration:

The vibration shall be measured at maximum achievable load and shall not exceed 250 Microns.

Noise Level Check:

The noise level shall be measured (as per IS: 12065) when the D.G set is operating at rated speed at maximum achievable load with a slow response meter on the A- weighting scale at a minimum of 8 points all round DG set at a distance of one meter from the nearest surface of the machine and at a height of 1.5 m from the floor level. The average of A-weighted sound level measurement shall be expressed in decibels to a reference of point 0.002 microbar.

Uninterruptible Power Supply (UPS):

Introduction: An Uninterruptible Power Supply (UPS) is a device installed upstream of the equipment or the network which requires a continuous source of electrical power, with a high level of reliability. UPS systems are designed to filter out voltage transients and variations, and assure continuous operation during primary power failures of variable duration caused by lightning, short-circuit, etc.

Functionality: The UPS consists of the following elements.

i Rectifier battery/charger

ii DC/AC inverter

iii Battery

iv Static switch for source commutation

v Isolating transformer

vi Mains by-pass switch

vii Maintenance by-pass switch

Only the first three components in the above list occur in all UPS. Others may be installed depending on power, importance and type of load.

A UPS has the following modes of operation.

Normal Mode:Load is supplied from the mains 1 via the rectifier and inverter. Battery is being charged.

Autonomous Operation: Mains 1 power cut. Load is supplied from the battery via the inverter.

By-pass Supply:

When Mains 1 power is cut due to overload or failure of the inverter. The static switch changes over to the Mains 2.

Manual by-pass

Rectifier, charger and static switch are isolated. Maintenance of the UPS is possible without any disruption for the supply.

UPS Operation Monitoring:

For the proper operation of the UPS several measurements, parameters and alarms are monitored. They may vary according to the manufacturer and type. The following lists of typical parameters are not exhaustive and for a given type may be reduced or extended.

Measurements to be obtained:

a. Rectifier voltage/current

b. Inverter voltage/frequency

c. Load current

d. Mains 1 voltage

e. Mains 2 voltage

f. Battery voltage/current

Status to be indicated:

Position of all switches.Alarms Provided:

i Inverter fault

ii Rectifier fault

iii Inverter current limitation

iv Mains 2 voltage/frequency out of limits

v Overcharge

vi Overheating

vii Battery voltage too high

viii End of battery autonomy

DC AUXILIARY SYSTEMIntroduction:

The most critical component of a Protection, Control and Monitoring (PCM) system is the auxiliary DC control power system. Failure of the dc control power can render fault detection devices unable to detect faults, breakers unable to trip for faults, local and remote indication to become inoperable. Capital cost and reliability objectives must be considered before defining the D.C systems to be used for a specific installation.

a) Battery Unit:

A battery converts chemical energy I n to electrical energy by means of an electrochemical oxidation-reduction reaction. This type of reaction involves the transfer of electrons from one material to another through an electric circuit. The basic electrochemical is called cell

Components of a battery cell:

A resilient plastic container i. The anode: This gives up electrons to the external circuit and is oxidized during the electrochemical reaction it should be an efficient reducing agent with high columbic output (Ah/g), good conductivity, stability etc.

ii. The Cathode: This accepts electrons from the external circuit and is reduced during the electrochemical reaction it should be an efficient oxidizing agent, stable when contact with electrolyte and have useful working voltage.

iii. Electrolyte: This provides the medium for transfer of electrons as ions inside the cell between the electrodes. It must have good ionic conductivity but not electrically conductive as it wound cause electrical short-circuiting it should not react with the electrode materials and shall be stable with temperature changes.

iv. Plate separators: These made of porous synthetic material for separating anode and cathode mechanically. They are permeable to the electrolyte in order to maintain the desired ionic conductivity

v. Lead terminals: These are for connecting the battery to the external circuits. Both +ve and ve terminals of the cells shall be capable of proper termination and shall ensure its consistency with the life of the battery.

vi. Container: The container shall be fire retardant and shall have an oxygen index of at least 28%.The porosity of the container shall be such as not to allow any gases to escape except from the regulation valve. The container material shall have chemical and electro chemical compatibility and shall be acid resistant. Cell shall not show any deformity or bulge on the sides under all working conditions.

vii. Cell covers: The cell covers shall be made of suitable material compatible with the container material and permanently fixed with the container. Fixing of pressure regulation valve and terminal posts in the cover shall be such that the seepage of electrolyte, gas escapes and entry of electro static spark are prevented.

viii. Pressure Regulation Valve: Each cell shall be provided with a pressure regulation valve. The valve shall be self re-sealable and flame retardant. The valve unit shall be such that it can not be opened without proper tool.ix. Connectors, Nuts and Bolts, Heat Shrinkable Sleeves: Where it is not possible to bolt the cell terminals directly to assemble a battery, separate non corroding lead or copper connectors of suitable size shall be provided to enable connection of the cells. Copper connections shall be lead coated to withstand corrosion due to sulphuric acid at a very high rate of charge or discharge. Nuts and bolts for connecting the cells shall bee made of copper, brass or stainless steel. Copper or brass nuts and bolts shall be lead coated to prevent corrosion. Stainless steel bolts and nuts can be used without lead coating. All inter cell connectors shall be protected with heat shrinkable silicon sleeves for reducing

Batteries: Batteries consisting of individual cells are used to store electricity and are relied upon to provide the required power for a specified period with in specified voltage limit.

Battery Capacity: The capacity of the battery is determined by the capacity of the individual series Connected cells.

Types of Cells: The Battery cells are of two types.

1. Primary Cells

2. Secondary Cells

A primary cell is any kind of electrochemical cell in which the electrochemical reaction of interest is not reversible, so used in disposable batteries. The most common primary cells today are found in alkaline batteries; earlier carbon-zinc cells, with a carbon post as cathode and a zinc shell as anode were prevalent. Unlike a secondary cell, attempting to reverse the reaction in a primary cell via recharging is dangerous and can lead to a battery explosion. A related difference is that primary batteries use up the materials in one or both of their electrodes, while, ideally, the reversibility of the reactions in a secondary cell allows them to be restored to almost the same fully charged condition on each recharging.

The battery unit consists of number of secondary cells (storage cells).

The Chemical reaction which takes place in a Lead Acid Storage Battery is as follows.

Battery Discharged Battery Charged

(+Plate) (-Plate) (+Plate) (-Plate)

PbSo4 + PbSo4 + 2H2O PbO2 + Pb + 2H2SO4

Lead Sulphate +Lead Sulphate+ Water Led Peroxide + Lead + Sulphuric Acid

Types of Batteries:

1. Tubular Lead Acid Batteries

2. Plante Lead Acid Batteries

3. Valve Regulated Lead Acid(VRLA)Batteries

4. Flooded/Wet cell batteries :

5. AGM: Absorbed Glass Mat batteries

6. Gel cell batteries 7. Carbon foam leads acid batteries

8. The principle of the lead acid cell can be demonstrated with simple sheet lead plates for the two electrodes. However such a construction would only produce around an amp for roughly postcard sized plates, and it would not produce such a current for more than a few minutes.

Gaston Plante realized that a plate construction was required that gave a much larger effective surface area. Plant's method of producing the plates has been largely unchanged and is still used in stationary applications.

Wet cells designed for deep discharge are commonly used in golf carts and other battery electric vehicles, large backup power supplies for telephone and computer centers and off-grid household electric power systems.

Gel batteries are used in back-up power supplies for alarm and smaller computer systems (particularly in uninterruptible power supplies) and for electric scooters, electrified bicycles and marine applications. Unlike wet cells, gel cells are sealed, with pressure relief valves in case of overcharging. In normal use they cannot spill liquid electrolyte.

Absorbed glass mat (AGM) cells are also sealed and used in battery electric vehicles, as well as applications where there is a fairly high risk of the battery being laid on its side or over-turned, such as motorcycles.

VRLA(Valve Regulated Lead Acid) Batteries: These batteries are preferred for use in substations and power stations due to the following advantages.i VRLA batteries have a pressure regulated valve which does not allow the gasses to escape unless the set pressure is exceeded. As the charging voltage is kept at lower level, there is negligible gassing. Moreover, recombination of hydrogen and oxygen is achieved by, which further results in reduction in loss of water. As the amount of released gasses is negligible, release of acid fumes is also reduced. Hence these batteries can also be installed in the equipment room. Whereas, in flooded batteries (tubular/flat-pasted batteries) a large amount of sulphuric acid fumes are released, due to which a separate battery room with exhaust fans is essential.

ii Use of VRLA batteries results in:

Saving in space as the battery, power plant and equipment can be installed in the same room.

Saving in bus-bar/cable material.

Low voltage drop resulting in better utilization of battery capacity and increase in efficiency of equipment.

iii Charge efficiency of these batteries is excellent, i.e., 6 to 8 hours for 90% recovery, as against 12 to 14 hours for flooded batteries. Recouping of capacity is quicker as shorter time is sufficient as compared to flooded batteries, suiting the rural power supply conditions particular

iv They have high charge density, resulting in smaller battery size. Moreover, the battery can be discharged to lower end-cell voltage, viz., and 1.75V/cell against 1.85V/cell for flooded batteries.

v They can be stacked horizontally and the cell can be stacked one above the other, which reduces the battery space requirement by 30-60%.

vi They can be transported in the charged condition as there is no danger of the spillage of the electrolyte, and hence, initial charging at site is not required. Flooded batteries can not be transported in charged condition, hence assembly and charging at site is essential. Moreover, it will be more difficult for the flooded batteries to meet the pollution norms, issued by Ministry of Environment and Forest.

vii Capacity of VRLA batteries can be recovered even after a storage period of six months/one year within three to four charge discharge cycles, while in flooded batteries it very difficult even after one month, due to sulphation of the plates while in idle condition.

viii Stratification is unavoidable in flooded batteries because of the settling down of the acid in the lower portion of the cell which causes sulphation in both lower and upper parts of the plates. To avoid stratification, periodic boost-charging of these batteries at 2.7V/cell is absolutely essential, for agitating the electrolyte. ix In VRLA batteries, internal short-circuiting does not occur, while it is quite common in flooded batteries due to sedimentation of shed active material of the positive plate.

DC Circuits:Following D.C circuits are present in a substation:

i Control circuits

ii Indication and alarm circuits

iii Battery Charger, and D.C distribution circuits

i. Control Circuits:

a) Breaker Closing Circuits

Remote closing circuits

Local closing circuits b) Breaker Tripping Circuits

Remote tripping circuits

Local tripping circuits

Relay tripping circuits

c) Interlock Circuits

Interlock between breakers and isolators

Interlock between breakers

ii. Indication and Alarm Circuits:

i. Breaker close indication circuit

ii. Breaker open indication circuit

iii. Healthy trip indication circuit

iv. Spring charge indication circuit

v. Semaphore circuit

vi. Breaker trip alarm circuit

vii. Over Current/Earth fault relay trip alarm

viii.Transformer Alarm Circuits, Oil Temp High, winding Temp high, Transformer Buchholtz, OLTC Buchholtz, Low oil level alarms Distance Protection, differential. Protection and various other protection relays trip alarm.

iii. Battery Charger and DC Distribution Circuits:

Boost Charger Circuit

DC Leakage Circuit

Float Charger Circuit

DC Distribution Panel Circuit

DC Systems:The DC System in the sub stations comprises of the following:

1. DC Charging System consisting of AC/DC Chargers

2. Battery Unit

3. DC Distribution System

Communication circuits:1. Emergency lighting system

2. UPS-Uninterrupted power supply

3. PLCC (Power Line Carrier Communication) and

4. SCADA (Supervisory Control and Data Acquisition)

Auxiliary D.C Voltage Levels:

System Requirements:System VoltageMaximum Voltage during Float operationMin. Voltage When no charger is working and battery fully discharged up to 1.85V per cell

220V

110V242 V

121 V198 V

99 V

48V52.8V43.2 V

a) DC Charging System:

Storage battery cells are charged to compensate their discharge so that they are available for any emergency. The charging is done on continuous basis to take care of load discharge or self discharge by the battery there are mainly two types of charging used in the sub-stations. Normally the DC power is supplied to the load by the float charger. It also supplies trickle current to the battery to keep it healthy. If the charging current under float mode exceeds a set level, boost charger is switched on. It supplies quick charging current to the battery. On battery reaching the set value, the boost charger is switched off.

Float/boost chargers are must in power substations, generating stations, telephone exchanges etc. For control/monitoring systems, tripping circuits and supplying DC power source. 1. Float or Trickle Charging: Float charging is done to meet the demand. When nominal voltage of the battery cell is 2.0 V there is considerable variation during charging and discharging. For batteries on float charge for continuous stand by duty floating voltage is to be selected correctly. If this voltage is below 2.10V per cell, the cells will gradually loose there charge due to internal losses and would require frequent boost charging at 2.3 2.7V per cell to bring back to the fully charged state. If the floating voltage is above 2.3V per cell there would be excessive gassing and electrolyte level have to be made up at more frequent interval levels. For Keeping the Battery fully charged. With out requiring boost charging, Battery manufactures recommend floating at 2.25V per cell. For allowing necessary safety margin for voltage fluctuations, charger regulation, voltmeter error etc. The optimum continuous bus voltage would be about 7% higher than the nominal voltage of the DC system. It would be about 235Vfor 220V system. The number of cells would be 109 with 2.15V per cell.

Equalizing Charging: This consists of raising voltage above floating voltage and maintaining it for specific time. To prevent batteries from under charging and also to build up the specific gravity after prolonged battery discharge equalizing charging is to be done to the battery banks. This charges up the week cells before they become sulphated and arrests any tendency of heavy acid to sink to the bottom of the cell. It is recommended that equalizing charge shall be given quarterly to all floating batteries.

2. Boost Charging: Boost charging is done as emergency charging for the batteries which are in discharged condition. During boost charging the battery charger shall operate on constant current mode (when automatic regulator is in service) .It shall be possible to adjust the boost charging current continuously over a range of 50 to 100% of the rated output current for Boost charging mode. The charger output voltage shall automatically go on rising, as the battery charges up. For limiting the output voltage of the charger, a potentio meter shall be provided on the front of the panel, where by it shall be possible to set the upper limit of the voltage. Suitable filter circuits shall be provided in all the chargers to limit the ripple content (peak to peak)in the output voltage to 1%,irrespective of the DC load level, when they are not connected to a battery.

All battery chargers shall have two nos. MCCBs on the input side to receive cables from two sources. Mechanical interlock should be provided such that only one shall be closed at a time. It shall be of P2 duty and suitable for continuous duty. MCCBs should have auxiliary contacts for annunciation.

Rectifier Transformer: The rectifier Transformer shall be continuously rated, dry air-cooled (A.N.) and of Class - F insulation type. The rating of the rectified Transformer shall have 10% overload capacity.

Rectifier Assembly: The rectifier assembly shall be fully /half controlled bridge type and shall be designed to meet the duty as required by the respective charger. The rectifier shall be provided with heat sink having their own heat dissipation arrangements with natural air cooling. Necessary surge protection device and rectifier type fast acting HRC fuses shall be provided in each arm of the rectifier connections

Instruments: One AC Volt meter and one AC ammeter along with selector switches shall be provided for all chargers in the AC incoming circuit.. One DC Volt meter and one DC ammeter (with shunt) shall be provided for all chargers on DC out going circuit. The instruments shall be flush type, dust proof and moisture resistant. The instruments shall be of 1.5 accuracy classes. In addition to the above a centre zero voltmeter with selector switch shall also be provided for 220 V chargers for testing purpose.

Blocking Diode: Blocking Diode shall be provided in the positive pole of the output circuit of each charger to prevent current flow from the DC battery into the charger.

Annunciation System: Through LEDs following audio-visual indications shall be provided in the chargers.

a. AC power failure

b. Rectifier/charger fuse blown

c. Over voltage across the battery when boost charging

d. Abnormal (High/Low) voltage

On owners control boardCHARGER TROUBLE indication when above abnormalities occur

Tests:

Continuous rating

Ripple free output

Voltage regulation

Load limiting characteristic

Insulation resistance

Performance of annunciation system.

b) Battery/ Battery Charger Configurations:Figure (a) and (b) gives the main electrical features associated with battery/battery charger combinations. Charger units are used to supply either just a battery, provide an autonomous DC supply, or a battery/inverter combination to provide an autonomous AC supply. The level of autonomy usually defined in terms of the number of hours or minutes the equipment will enable the load to function to correctly after loss of input mains AC supply. The capacity of the charger must also be such that after a severe discharge it has the capacity to supply the full DC system load current simultaneously. The technique used for battery charging is called float charging and involves the battery being permanently connected to the load in parallel with a charger.a) Single 100% Battery and 100% Charger:

b) Semi-Duplicate 2x50% Batteries and 2x100% Chargers:

Battery Sizing Calculations:

Capacity and Loads:

The load on the battery is calculated from the power consumption characteristics of the loads taking into account their nature:

Typical Substation Loads are listed below:

Trip Coils: Load requirements approximately 150 W for less than 1 second. Note that in complex protection schemes (e.g. Busbar protection) several trip coils may be simultaneously energized and the sum of the individual loads must therefore be used in the battery sizing calculations.

Controls/Relays: Continuous loads such as indicator lamps will contribute to battery discharge on loss of mains supply.Closing Coils: Older oil circuit breaker coils may take 10-30 kW depending upon design for less than 1 second at 110 V. More modern vacuum or SF6 circuit breaker motor wound spring charged mechanisms and solenoid closing coils have 300-600 W ratings.DC Motors: Diesel generator black start pump and cranking, isolator or switchgear drives, air blast circuit breaker air compressor motor drives.

Choice of Voltage: The choice of voltage based on the voltage drops in the leads at maximum specified load current for cross-section. It also depends on the rated voltages of various auxiliaries and other sources.

The voltage drops in the leads is calculated from following:

V = 2xRxI Here V = Voltage drop in volts, DC

I = Line current in amps, DC

R = Resistance of lead in ohms in one way

Also V= 2XRxI/kVa

k=conductivity (copper-56%, aluminium-35%)

a=cross-sectional area of lead, mm 2

For medium and small installations, D.C. voltage of 110V is generally preferred while for large installations, 220V DC is preferred.

Ampere Hour Capacity:

The capacity of battery system is specified in terms of ampere hours. It is a product of discharge current and the time of discharge. Ampere-hour capacity is dependant on the magnitude of the discharge current.

Typical Ratings of Battery System:

Hours123510

Current A7040332213

Ampere-hour Capacity7080100110130

Maximum discharge current =

The battery capacity and no. of cells shall be arrived at based on the following duty cycle

System voltageLoadDurationType of Loads

220V

Continuous load3 hoursRelays, IEDs, Station HMIs, spring charging, Isolator interlocking load, Miscellaneous permanently connected loads.

Emergency load1 hour Substation emergency lighting loads.

Momentary load1 minuteBreaker closing, Tripping loads(taking simultaneous occurrence as per system).

48V

Continuous load3 hoursContinuous load associated with PLC(when speech is not working.

Momentary load15 minutesLoads associated with PLC (when speech is working.

Battery Room Ventilation:

The area or enclosure where the battery system is located should have an adequate level of air changes to prevent buildup of hydrogen gas to an explosive level. The minimum explosive level is 4% by volume. A design value of 2% should typically be used. The amount of hydrogen evolution during operation varies based upon the battery technology in use and the operating conditions.

D.C Distribution System:

Schemes generally adopted:

i One battery one charger scheme

ii One battery two charger scheme

iii One battery two charger scheme

One main DC distribution board has to be provided for each battery bank from which power is distributed. Proper monitoring system of DC distribution supply must be defined so that remedial action is taken when the DC supply fails. In addition to the alarms on the battery/battery charger combination itself alarms may be derived from failure within the DC distribution. One main DC distribution board has to be provided for each battery bank from which power is distributed to the various loads through switch fuse feeders.

The DC supply is duplicated to each control and relay panel by sectionalizing the DC distribution and having separate feeders to each panel. Each relay and control panel DC circuit associated with each substation circuit is also monitored for loss of DC supply. Since DC failure could in itself prevent alarms from operating small AC/DC converters may be specified to drive the annunciation modules.

Complete segregation is maintained between the two main sources and no mixing is allowed. For this purpose only single core cables are provided for all inter connections between the batteries, chargers and main distribution boards. The busbars and connections in the distribution board would be fully insulated with PVC sleeving or epoxy painting, so as to minimize the risk of flashover.

Battery Earth Fault Relays:

The 220V DC system will operate as ungrounded systems. Suitable relays are provided in the main DC distribution board for detecting single earth fault. 220V DC system is ungrounded and provides 110V each on positive to earth and negative to earth.48V DC system is positive grounded .As DC is vital part in any substation, any second earth fault on 220V system may affect the system and earth fault need be identified and eliminated.

To give alarm on earth fault relays are provided in the DC system.

Typical Enquiry Data of DC switchboard

1. Maximum physical dimensions width x depth x height (mm)

2. Enclosure IP rating

3. Single line diagram drawing number

4. Unequipped spare ways

5. Equipped spare ways

6. Busbar maximum current rating (A)

7. Switchgear type

8. Manufacturer

9. Manufacturers drawings

10. Metering, alarms and protection Boost charge

11. contactors Anti- paralleling diodes

Notes:

a) Recommend P2 category for repeated short circuit capability

b) Metal-clad, metal enclosed, etc

c) To be completed by the manufacturer

d) To be clearly indicated upon enquiry drawing or detailed circuit by circuit here. Quiescent and operated power consumption should be noted.

e) Maximum current rating, coil rating and method of interlocking if applicable.

Battery Specification:Sl.No.Technical ParticularsDetails

1Type of battery and Standard

2Electrolyte

3Nominal System voltage

4Float voltage per cell

5Normal system float voltage required

6Normal float charging current required

7Minimum recommended battery voltage

8Recommended boost charging voltage per cell

9Recommended boost charging current

10Dimensions of cell width x depth x height

11Overall Dimensions of battery bank width x depth x height

12Overall weight of battery bank

13Material of battery cases

14.Battery capacity i.e.; discharge rate Amp. hours

15Duty cycle requirements

16Battery voltage at the end of duty cycle

17Normal standing load

18Max. D.C. current capability-(short time)

19Battery mounting

20Connections

21Volume of hydrogen produced during boost charging

22Manufacture, type, reference and manufacturers drawings

Battery Charger Specification:

Sl.No.DetailsParticulars

1.Max. physical dimensions

-width x depth x height

2.Charger to suit (type of battery)

3.1. A.C. input supply for specified out put -kVA

2. No. of phases single or 3-phase

3. Voltage tolerance +/-

4. Frequency

5. Frequency tolerance +/-

4.D.C. output

1. Float voltage

2. Boost voltage

3. Float current

4. Boost current

5. Ripple

5.Psophometric output noise level for loads between 0% and 100% as per regulations ( mV @ - Hz)

6.Noise level limit

( mV rms hum @ - Hz)

7.Current limitation range +/-

8.Voltage limitation range +/-

9.Time to recharge battery to 90% capacity from fully discharged state

10Charger efficiency

11.Overload protection

12.Controls, indications and alarms

13.Applicable standards

14.Manufacturer and reference

AC & DC DISTRIBUTION BOARDSDistribution Boards:

Construction:

1. All boards shall be of metal enclosed, indoor floor mounted, compartmenta-lized construction and free standing type.

2. All board frames, shall be fabricated using suitable mild steel structural sections or pressed and shaped cold-rolled sheet steel of thickness not less than 2.0 mm. Frames shall be enclosed in cold-rolled sheet steel of thickness not less than 1.6 mm. Doors and covers shall also be of cold rolled sheet steel of thickness not less than 1.6 mm. Stiffeners shall be provided wherever necessary.

3. All panel edges and cover/door edges shall be reinforced against distortion by rolling, bending or by the addition of welded reinforcement members.

4. The complete structures shall be rigid, self-supporting, free from flaws, twists and bends.

5. All cut-outs shall be true in shape and devoid of sharp edges.

6. All boards shall be of dust and vermin proof construction and shall be provided with a degree of protection of IP: 52 as per IS 2147. However, the busbar chambers having a degree of protection of IP: 42, in accordance with IS 2147, arc also acceptable where continuous busbar rating exceeds 1000 Amp. Provision shall be made in all compartments for providing IP: 52 degree of protection, when Circuit breaker or module trolley, has been removed. All cut-outs shall be provided with neoprene/ Synthetic rubber gaskets.

7. Louvers backed with metal screen shall be provided on the busbar chambers where continuous busbar rating exceeds 1000 Amps.

8. All boards shall be of uniform height not exceeding 2450 mm.

9. Boards shall be easily extendible on both sides, by the addition of the vertical sections after removing the end covers.

10. The base frames shall be made of structural steel sections, along with all necessary mounting hardware required for welding the base frames to the insert plates, shall be supplied along with the base frames.11. All boards shall be divided into distinct vertical sections, each comprising of:

(i) A completely enclosed busbar compartment for running horizontal and vertical busbars. Busbar chamber shall be completely enclosed with metallic portions. Bolted covers shall be provided for access to horizontal and vertical busbars and all joints for repair and maintenance, which shall be feasible without disturbing feeder compartment.(ii) Completely enclosed switchgear compartment(s) one of each circuit for housing circuit breaker or MCCB or motor starter.(iii) A compartment or alley for power and control cables. Cable alley door shall preferably be hinged. Cable alley shall have no exposed live parts, and shall have no communication with busbar chamber. It shall be of atleast 350mm width.

(iv) A compartment for relays and other control devices associated with a circuit breaker.

12. Sheet steel barriers shall be provided between two adjacent vertical panels running to the full height of the switchboard, except for the horizontal busbar compartment. Each shipping section shall have full metal sheets at both ends for transport and storage. All equipments associated with a single circuit except MCB circuits shall be housed in a separate compartment of the vertical section. The Compartment shall be sheet steel enclosed on all sides with the withdrawal units in position or removed. The front of the compartment shall be provided with the hinged single leaf door, with locking facilities.13. In case of circuits controlled by MCBs, group of MCB feeders can be LOCATED in common compartment. In such case number of MCB feeders to be used in a common compartment shall not exceed 4 (four) and front of MCB compartment, shall have a viewing port of toughened glass sheet for viewing and sheet steel door of module shall be lockable with knob/panel key.

14. After isolation of power and control circuit connections it shall be possible to safely carryout maintenance in a compartment with the busbar and adjacent circuit live. Necessary shrouding arrangement shall be provided for this purpose over the cable terminations located in cable alley. 15. The minimum clearance, in air between phases and between phase and earth for the entire run of horizontal and vertical busbars, shall be 25 mm. For all other components, the clearance between "two live parts", " A live part and an earthed part" and isolating distance shall be atleast ten (10) mm throughout. Wherever it is not possible to maintain these clearances, insulation shall be provided by sleeving or barriers. However, for horizontal run of busbar minimum clearance of 25 mm should be maintained even if they are sleeved.16. The temperature rise of horizontal & vertical busbars when carrying rated current along its full run shall in no case exceed 55C, with silver plated joints and 40C with all other types of joints over an outside ambient temperature of 50C.

17. All identical circuit breakers and module chassis of same size shall be fully interchangeable without having to carryout modifications.

All Circuit breaker boards shall be of single front type, with fully draw out circuit breakers, which can be drawn out without having to unscrew any connections. The circuit breakers shall be mounted on rollers and guides for smooth movement between SERVICE, TEST and ISOLATED positions and for withdrawal from the switchboard. Testing of the breaker shall be possible in the TEST position. Wherever two breaker compartments are provided in the same vertical section, insulating barriers and shrouds shall be provided in the rear cable compartment to avoid accidental touch with the live parts of one circuit when working on the other circuit.18. All disconnecting contacts for power circuits shall he of robust design and fully self aligning. Fixed and moving contacts of the power draw out contact system shall be silver plated. Both fixed and moving contacts shall be replaceable.19. All AC & DC boards shall be of single front type.

All modules shall be fixed type except air circuit breaker module, which shall be drawout type.The connections from busbars to the main switch shall be fully insulated/ shrouded, and securely bolted. The partition between the feeder compartment and cable alley may be non-metallic and shall be of such construction as to allow cable cores with lugs to be easily inserted in the feeder compartment for termination. The tentative power and control cable entries shall be from bottom.

Adopter panels and dummy panels required to meet the various busbar arrangements and layouts required shall be included in the scope of work.20. All sheet work shall be pre-treated, in tanks, in accordance with IS: 6005. Degreasing shall be done by alkaline cleaning. Rust and scale shall be removed by pickling with acid. After pickling the pans shall be washed in running water. Then these shall be rinsed in slightly alkaline hot water and dried. The phosphate coating shall be of Class - C as specified in IS: 6005. The phosphated surfaces shall be rinsed and passivated prior to application of stoved lead oxide primer coating after primer application, two coats of finishing synthetic enamel paint on panels shall be applied. Electrostatic painting shall also be acceptable.

Finishing paint on panels shall be shade 692 (Smoke grey) of IS: 5 unless required otherwise by the PURCHASER. The inside shall be properly stoved. The paint thickness shall be coated by peelable compound by spraying method to protect the finished surfaces from scratches grease din and oily spots during testing, transportation, handling and erection.BUS BARS AND INSULATORS: All AC Distribution Boards shall be provided with three phase buses and neutral bus bars to carry the specified rated current. All busbars and jumper connections shall be of high conductivity aluminium/ copper of adequate size the bus bar size calculation shall be submitted for approval. The Cross-Section of the busbars shall be uniform through out the length of Switchgear and shall be adequately supported and braced to withstand the stresses due to the specified short circuit currents. All busbars joints shall be provided with high tensile steel bolts. Belleville/spring washers and nuts, so as to ensure good contacts at the joints. Non-silver plated Busbars joints shall be thoroughly cleaned at the joint locations and suitable contact grease shall be applied just before making a joint. All busbars shall be colour coded as per IS: 375.

All busbars shall be adequately supported by non-hygroscopic, non-combustible, track resistant & high strength type Polyester fibre glass moulded insulators. Separate supports shall be provided for each phase and neutral busbar. If a common support is provided anti-tracking barriers shall be provided between the supports.

EARTH BUS:1. A galvanised steel earthing shall be provided at the bottom of each panel and shall extend throughout the length of each switchboard. It shall be welded/bolted to the frame work of each panel and breaker earthing contact bar. Vertical bus shall be provided in each vertical section which shall in turn be bolted/welded to main horizontal ground bus.

2. The earth bus shall have sufficient cross-section to carry the momentary- short circuit and short time fault currents to earth without exceeding the allowable temperature rise.3. Suitable arrangements shall be provided at each end of the horizontal earth bus for connecting to the station earthing system. The horizontal earth bus shall project out the switch board ends and shall have predrilled holes for this connection. 4. All non-current metal work of the Switchboard shall be effectively bonded to the earth bus. Electrical conductivity of the whole switchgear enclosures, frames work and the truck shall be maintained even after painting.5. The truck and breaker frame shall get earthed while the truck is being inserted in the panel and positive earthing of the truck and breaker frame shall be maintained in all positions. 6. Each module frame shall get engaged to the vertical earth bus. Before the dis-connecting contacts on these module are engaged to the vertical busbar. All metallic cases of relays, instruments and other panel mounted equipments shall be connected to earth by independent stranded copper wires of size not less than 2.5 mm. Insulation colour code of earthing wires shall be green. Earthing wires shall be connected to terminals with suitable clamp connectors and soldering is not acceptable. Looping of earth Connection which would result in loss of earth connection to the devices when a device is removed is not acceptable. However, looping of earth connections between equipment to provide alternative paths or earth bus is acceptable. 7. VT and CT secondary neutral point earthing shall be at one place only, on the terminal block. Such earthing shall be made through links so that earthing of one secondary circuit shall be removed without disturbing the earthing of other circuit.8. All hinged doors shall be earthed through flexible earthing braid. Caution nameplate "Caution-Live Terminals shall be provided at all points where the terminals are like to remain live and isolation is possible only at remote end.

Circuit Breakers:

1. Circuit breakers shall be of three-pole air break horizontal drawout type and shall have inherent fault making and breaking capacities as specified in "Technical Parameters".

2. Circuit breakers shall be mounted along with it operating mechanism on a wheeled carriage. Suitable guides shall be provided to minimize misalignment of the breaker.3. There shall be 'Service', Test and Fully withdrawn positions for the breakers. In 'Test' position the circuit breaker shall be capable of being tested for operation without energizing the power circuits i.e. the power contacts shall be disconnected while the Control circuits shall remain undisturbed. Locking facilities shall be provided so as lo prevent movement of the circuit breaker from the SERVICE, TEST OR FULLY WITHDRAWN position. It shall be possible to close the door in TEST position.

4. All circuit breakers shall be provided with 4 NO and 4 NC potentially free auxiliary contacts. These contacts shall be in addition to those required for internal mechanism of the breaker. Separate limit switches each having required number of contacts shall be provided in both 'SERVICE' & TEST position of the breaker. All contacts shall be rated for making continuously carrying and breaking 10 Amps at 240V AC and 1 Amp (Inductive) at 220V DC.

5. Suitable mechanical indications shall be provided on all circuit breakers to show 'OPEN', 'CLOSE, 'SERVICE', TEST and 'SPRING CHARGED positions.

6. Main poles of the circuit breakers shall operate simultaneously in such a way that the maximum difference between the instants of contacts touching during closing shall not exceed half cycle of rated frequency.

7. Movement of a circuit breaker between SERVICE AND TEST positions shall not be possible unless it is in OPEN position. Attempted with drawl of a closed circuit breaker shall trip the circuit breaker.

8. Closing of a circuit breaker shall not be possible unless it is in SERVICE, TEST POSITION or in FULLY WITHDRAWN POSITION. 9. Circuit breaker cubicles shall be provided with safety shutters operated automatically by the movement of the circuit breaker carriage to cover the stationary isolated contacts when the breaker is withdrawn. It shall however, be possible to open the shutters intentionally, against spring pressure for testing purpose.10. A breaker of particular rating shall be prevented from insertion in a cubicle of a different rating.11. Circuit breakers shall be provided with electrical anti-pumping and trip free feature, even if mechanical anti-pumping feature is provided.12. Mechanical tripping shall be possible by means of front mounted RED Trip' push-button. In case of electrically operated breakers these push buttons shall be shrouded to prevent accidental operation.

13. Breaker controlled motors shall operate satisfactorily under the following conditions:

i. Direct on-line starting of Induction Motors rated 110 kW to 220 kW with a locked rotor current of seven times the rated current, and starting time of up to 30 seconds.

ii. Breaking on-load, full load and locked rotor currents of Induction Motors for rated 100 kW to 220 kW. 14. Means shall be provided to slowly close the "circuit breaker in withdrawn position. If required for inspection and setting of Contacts, in SERVICE position slow closing shall not be possible.

15. Power operated mechanism shall be provided with a universal motor suitable for operation with 220V DC Control supply with voltage variation from 90% to 110% rated voltage. Motor insulation shall be class 'E' or better. The motor shall be such that it requires not more than 30 seconds for fully charging the closing spring. Once the closing springs are discharged, after the one closing operation of circuit breaker, it shall automatically initiate, recharging of the spring. The mechanism shall be such that as long as power is available to the motor, a continuous sequence of closing and opening operations shall be possible. After failure of power supply at least one open-close-open operation shall be possible.16. Provision shall be made for emergency manual charging and as soon as this manual charging handle is coupled, the motor shall automatically get mechanically decoupled.

17. All circuit breakers shall be provided with closing and trip coils. The closing coils shall operate correctly at all values of Voltage between 85% to 110% at rated control voltage. The trip coil shall operate satisfactorily under all values of supply voltage between 70% to 110% of rated control voltage.

18. Provision for mechanical closing of the breaker only in "TEST and 'WITHDRAWN' positions shall be made.

Protection Co-Ordination:The overload and short circuit tripping of the circuit breakers shall be co-ordinated with the upstream and down stream circuit breakers/fuses/motor starters, to provide satisfactory discrimination.

Moulded Case Circuit Breaker (MCCB) and MCB

MCCB shall in general conform to IS: 13947 Part-2. All MCCB shall be of P2 duty.

MCCB shall be flush mounted on the AC/DC distribution boards.

MCCBs shall be provided with thermo-magnetic type release for over current and short circuit protection. The setting of the thermal release shall be adjustable between 75% to 100% of the rated current. The MCCB shall have breaking capacity not less than 20 kA.

MCCBs used for ACDB incomers and Bus coupler shall be equipped with stored energy mechanism for electrical closing and tripping. All other MCCBs shall be manually operated. The operating handle should give a clear trip indication.

Miniature circuit breaker (MCB) shall conform to EC: 898-1987 and IS: 8828. Relays:1. All relays and timers in protective circuits shall be flush mounted on panel front with connections from the inside. They shall have transparent dust light covers removable from the front. All protective relays shall have a drawout construction for easy replacement from the front. They shall either have built-in test facilities, or shall be provided with necessary test blocks and test switches located immediately below each relay. The auxiliary relays and timers may be furnished in non-drawout cases. All AC relays shall be suitable for operation, at 50 Hz with 110 volts VT secondary and 1 amp or 5 amp CT secondary.2. All protective relays and timers shall have at least two potentially free output contacts. Relays shall have contacts as required for protection schemes. Contacts of relays and timers shall be silver faced and shall have a spring action. Adequate number of terminals shall be available on the relay cases for applicable relaying schemes.3. All protective relays auxiliary relays and timers shall be provided with hand reset operation indicators (Flags) for analyzing the cause of operation.4. All relays shall withstand a test voltage of 2 kV (rms) for one minute.5. Motor starters shall be provided with three elements, ambient temperature compensated, lime lagged, hand reset type overload relays with adjustable settings. The setting ranges shall be properly selected to suit the motor ratings. These relays shall have a separate black coloured hand reset push button mounted on compartment door and shall have at least one changeover contact.6. All fuse-protected contactor-controlled motors shall have single phasing protection, either as a distinct feature in the overload relays (by differential movement of bi-metallic strips), or as a separate device. The single phasing protection shall operate even with 80% of the set current flowing in two of the phases.Contactors: Motor starter contactors shall be of air break, electromagnetic type rated for un-interrupted duty as per IS: 13947 (Part 4).

Contactors shall be double break, non-gravity type and their main contacts shall be silver faced. Direct on line starter contactors shall be of utilization category AC2. These contactors shall be as per IS: 13947 (Part 4). Each contactor shall be provided with two (2) normally open (NO) and two (2) normally close (NC) auxiliary contacts. Operating coils of contactors shall b& of 240V AC unless otherwise specified elsewhere.

The Contactors shall operate satisfactorily between 85% to 110% of the rated voltage.

The Contactor shall drop out at 70% of the rated voltage.

Instrument Transformers: All current and voltage transformers shall be completely encapsulated cast resin insulated type suitable for continuous operation at the temperature prevailing inside the switchgear enclosure, when the switchboard is operating at its rated condition and the outside ambient temperature is 50C. All instrument transformers shall be able to withstand the thermal and mechanical stresses resulting from the maximum short circuit and momentary current rulings of the associated switchgear. All instrument transformers shall have clear indelible polarity markings. All seconding terminals shall be wired to a separate terminal on an accessible terminal bloc*k where star point formation and earthing shall be done. Current transformers may be multi or single core type. All voltage transformers shall be single phase type. The Bus VTs shall be housed in a separate compartment. All VTs shall have readily accessible HRC current limiting fuses on both primary and secondary sides.

Indicating Instruments: All indicating and integrating meters shall be flush mounted on panel front. The instruments shall be of at least 96 mm square size with 900 scales, and shall have an accuracy class of 2.5 or better. The covers and cases of instruments and meters shall provide a dust and vermin proof construction. All instruments shall be compensated for temperature errors and factory calibrated to directly read the primary quantities. Means shall be provided for zero adjustment without removing or dismantling the instruments. All instruments shall have white dials with black numerals and lettering. Black knife edge pointer with parallax free dials will be preferred. Ammeters provided on Motor feeders shall have a compressed scale at the upper current region to cover the starting current. Watt-hour meters shall be of 3 phase three element type. Control & Selector Switches:1. Control & Selector switches shall be of rotary type with escutcheon plates clearly marked to show the function and positions. The switches shall be of sturdy construction suitable for mounting on panel front. Switches with shrouding of live parts and sealing of contacts against dust ingress shall be preferred.

2. Circuit breaker selector switches for breaker Controlled motor shall have three slay put positions marked 'Switchgear', Normal and Trial respectively. They shall have two contacts of each of the three positions and shall have black shade handles.

3. Ammeter and voltmeter selector switches shall have four stay put position with adequate number of contacts for three phase 4 wire system. These shall have oval handles Ammeter selector switches shall have make before break type contacts to prevent open circuiting of CT secondaries.

4. Contacts of the switches shall be spring assisted and shall be of suitable material to give a long trouble free service.5. The contact ratings shall be at least the following:

(i) Make and carry continuously10 Amp.(ii) Breaking current at 220V DCI Amp (Inductive)(iii) Breaking current at 240V AC5 Amp (at 0.3 of lagging)Air Break Switches:

Air breaker switch shall be of the heavy duly, single throw group operated, load break, and fault make type complying with IS: 4064.

The Bidder shall ensure that all switches are adequately rated so as to be fully protected by the associated fuses during all abnormal operating conditions such as overload, locked motor, short circuit etc.

Switch operating handles shall be provided with padlocking facilities to lock them in OFF position.

Interlocks shall be provided such that it is possible to open the cubicle door only when the switch is in "OFF position and to close the switch only when the door is closed. However suitable means shall be provided to intentionally defeat the interlocks explained above. Switches and fuses for AC/DC control supply and heater supply wherever required shall be mounted inside and cubicles.

Push Buttons: Push-buttons shall be of spring return, push to actuate type. Their contacts shall be rated to make, continuously carry and break 10A at 240V and 0.5A (inductive) at 220V DC.

All push-buttons shall have one normally open and one normally closed contact, unless specified otherwise. The contact faces shall be of silver or silver alloy.

All push-buttons shall be provided with-integral escutcheon plates marked with its function. The colour of the button shall be as follows:(i) GREEN : For motor START, Breaker CLOSE(ii) RED :For motor TRIP, Breaker OPEN

(iii) BLACK :For overload reset.

All push-buttons on panels shall be located in such a way that Red-push-buttons shall always be to the left of green push-buttons.

Indicating Lamps:

Indicating lamps shall be of the panel mounting cluster LED type. The lamps shall have escutcheon plates marked with its function, wherever necessary.

Lamps shall have translucent lamp-covers of the following colours, as warranted by the application: Wired with 2.5 square mm copper wires. Voltage grade and insulation shall be same as above. Extra-flexible wires shall be used for wiring to device mounted on moving parts such as hinged doors.

All wiring shall be properly supported, neatly arranged, readily accessible and securely connected to equipment terminals and terminals blocks.

Power Cables Termination: Cable termination compartment and arrangement for power cables shall be suitable for stranded aluminium conductor, armoured XLPE/PVC insulated and sheathed, single core/three core, 1100 V grade cables.

All necessary cable terminating accessories such as Gland plates, supporting clamps and brackets, power cable lugs, hardware etc. shall be provided by the successful bidder, to suit the final cable sizes which would be advised later.

The gland plate shall be of removable type and shall cover the entire cable alley. Bidder shall also ensure that sufficient space is provided for all cable glands. Gland plates shall be factory-drilled according to the cable gland sizes and number which shall be informed to the contractor later. For all single core cables, gland plates shall be of non-magnetic material.

Type Tests:Type tests reports on Panels (Switchgear and control gear assemblies) as per IS 8623 Part- I shall be submitted for the following tests in line before the fabrication of switchgear is started:

i. Verification of temperature rise limitsii. Verification of the dielectric propertiesiii. Verification of short circuit strengthiv. Verification of the continuity of the protective circuitv. Verification of clearances and creepage distancesvi. Verification of mechanical operationvii. Verification of degree of protectionAutomatic Control of Outdoor Lighting:

EL type module of 415 V main lighting distribution board and emergency lighting distribution board and shall be controlled by timer and contactor module to facilitate its operation automatically. Automatic Supply Changeover:Automatic changeover between Incomer I, Incomer II, and DG set is to be carried out during the failure of supply in one/or both the incomers. After the restoration of the supply, system shall be restored to normal condition automatically. The requirement of changeover under various conditions are as below:

(i) Under normal conditions i.e. when supply is available in both the incomers, incomers I & II of 415 V Main switchboard, ACDB shall be in closed condition and Bus couplers and DG set breaker shall be in open condition.

(ii) In case of failure of either of the sources, the incomer of that source shall trip and Bus coupler shall get closed. On restoration of supply, normal conditions described above are to be established automatically.

(iii) In case of failure of supply in both the sources, both incomers, incomers of ACDBs and ACDB Bus coupler shall trip and DG set breaker switched on. On restoration of one or both sources, DG set breaker shall trip, DG set stopped and conditions described in paragraph (i) /(ii) shall be restored.To avoid unnecessary operation of switchgear for momentary disturbances all changeovers from one state to another shall be initiated after a time delay, after the conditions warranting such change has been detected.Modules & Components in the Distribution Board:

Each AC & DC Distribution Board shall comprise of a number of different types of modules as described hereunder. Module Type: AE (Electrically controlled circuit breaker for incoming and Bus Coupler Circuit).

(i) One (1)Triple pole air circuit breaker complete with all accessories and power operated mechanism as specified.

(ii) Two (2)Neutral link.

(iii) Three (3)Current Transformer for metering.

(iv) One (1)Ammeter with selector switch.

(v) Three (3)Current Transformer for relaying.

(vi) One (1)Triple pole instantaneous over-current relay having the setting range of 200-800% or 500-2000% or CT secondary and adjustable definite minimum time.

(vii) One(l)Instantaneous earth fault relay having an adjustable setting range of 10-40% or 20- 80% of CT secondary current and adjustable definite minimum time. The earth fault relay shall be provided with a stabilizing resistor.Modular Type M1 (Circuit Breaker Controlled Motor Feeder):Triple pole Air Circuit Breaker complete with accessories, and power operated mechanism as specified.

(i) One (1)Triple pole air circuit breaker complete with all accessories and power operated mechanism as specified.

(ii) One (1)Three position 6 pole selector switch SWITCH GEAR/NORMAL/TRIAL.

(iii) Three (3)Current Transformer for metering.

(iv) One (1)Ammeter with Ammeter selector switch.

(v) Three (3)Current Transformer for relaying.

(vi) One (1)Triple pole instantaneous over-current relay for providing positive sequence current protection in all the three phases. The relay setting range shall be continuously adjustable between 200-800% or 400-1600% of CT secondary rated current as required.

(vii) One (1)Double pole inverse definite minimum time over current relays connected in R & B phases for over current protection of motor rated 110 kW - 200 kW. The relay shall have an adjustable setting range of 50% - 200% of CT Secondary current and time setting range of 0-30 second. The relay shall be CDGM-22 of EE or equivalent.

(viii) One(l)Single pole adjustable definite lime delay relay for motor overload alarm connected in Y-phase only. The relay shall have reselling ratio of no. 1 less than 90%. The relay shall have continuously adjustable lime delay range of 2.5 lo 25 sec.

(ix) One(l)Instantaneous earth fault relay having an adjustable setting range of 10-40% or 20-80% of CT secondary current. The earth fault relay shall be provided with a stabilizing resistor.Module Type E:

(i) One (1)Four pole MCCB

Module G-1 (VT Module with under Voltage Ready):

(i) Three (3)

volts single phase voltage transformer star/star connect with stat point solidly earthed mounted on common draw out chassis. Accuracy class 0.5 for protection and metering with 50 VA Burden.

(ii) Six (6)HRC Fuses mounted on the above chassis.

(iii) One (1)Four position voltmeter selector switch.

(iv) One (1)Voltmeter (0-500 V)

(v) One (1)Double pole instantaneous under voltage relays with continuous variable setting range of 40-80% of 110 volts.

(vi) One (1)Time delay pick up relay having a time setting range of 0.5 to 3 sees with 3 NO. Self reset contacts, suitable for 220V DC.

(vii) One (1)Auxiliary relay 220 V DC with 2 No. self reset contacts.

(viii) Three (3)Indicating lamps with series resistor and colour lenses (Red, Blue & Yellow).

Module Type G-2:

(i) One (1)Four pole MCCB

(ii) One (1)Red indicating lamp to indicate isolating switch closed position.

Module Type S: (DC Metering and Protection Module):

i) One (1)Volt meter 300-0-300 V DC for 220 V DC DB/Voltmeter 0-75V DC for 50 V DCDB.

ii) One (1)Three(3) position voltmeter selector switch.

(iii) One (1)Instantaneous over voltage relay with 95% of 220 V DC. The resisting ratio of relay of relay should not be more than 1.25. The relay shall be provided with a series resister and a push button across if for resetting (pickup) the relay at about 105% of the drop out voltage.

iv) One (1)Instantaneous over voltage relay with setting range of 110% of 220V DC. The resetting ratio of relay should not be less than 0.8. The relay shall have a push button in series of resetting the relay at about 95% of the operating voltage.

v) One (1)Earth leakage relay only for 220V DC system having adjustable pick up range between 3 to 7 milliamps the relay shall be suitable for 220V DC/240V AC Auxiliary supply.

Module Type X: (DC Incomer from Battery Charger)

i) One (1)Double pole 250 V DC MCCB for incomer from battery.

ii) One (1)DC ammeter with shunt and range of 90-0-400 Amps, For 220 V DC DB and 90-0-200 Amp for 50V DC DB.

iii) One (1)Double pole 250V DC MCCB/MCB

iv) Two (2)Double pole single throw 250 V DC air break switch connecting battery & charger sections to DC DB.

Module Type DG-1 (Electrically Controlled Circuit Break for Incomer from DG Set):

i) One (1)Triple pole circuit breaker complete with all accessories and power operated mechanism as specified.

ii) One (1)Frequency meter.

iii) One (1)Voltmeter with selector switch.

iv) One (1)Remote/Local Selector switch.

v) Three (3)Current transformer for metering.

vi) Six (6)Current transformers for differential protection (out of this 2 Nos. will be supplied loose for mounting in DG set panel.

vii) Three (3)Current transformer for relaying.

viii) One (1)Ammeter selector switch.

ix) One (1)Ammeter

x) One (1)Watt meter of range 0-300 kW.

xi) One (1)Three pole voltage controlled definite time delay relay having current setting range of 50-200% of CT secondary current and adjustable time delay 0.3 to 3 sec.

xii) One (1)Watt hour meter with six (6) digits and minimum count of one (1) kwh.

xiii) One (1)Single pole definite time over current relay having a continuous setting range of 50-200% of CT secondary current and a time delay of 2.5-25 sec. connected in CT of Y phase for overload alarm. The relay shall have a setting ratio of not less than 90%.

xiv) One (1)Three pole differential protection relay having an operating current setting range of 10-40% of generator full load current. The relay shall be of high impedance type, with necessary stabilizing resistors.

xv) Two (2)Push buttons for remote starting & stopping of DG set (Red, Green).

Module Type H1:

i) One (1)Double pole DC switches with pad locking facility in off position.

Module Type EL:

i) One (1)Four pole MCCB.

ii) One (1)Contractor.

iii) Electronic Timer suitable for continuous operation, push button and selector switch be as per scheme requirement.

Technical Parameters:

Power Supply:

AC System

3 Phase, 4 wire, solidly earthed

b) Voltage

415 volts, ( 10%

c) Frequency50 Hz (5%

d) Combined variation( 10% absolute sum in voltage & frequency.

e) Fault level20 kA (rms)

DC System2 Wire, unearthed

a) System voltage220 V (10%

b) Fault level4 kA

c) System voltage50 V ( 10%

d) Fault level--

Cubicle Date:

Busbar Rating:

a) Continuous

for vertical panels

As required

b) Short time (1 sec.

kA (rms)

20 kA

c) Momentary (kA)

45 kA

Peak

d) Ambient Temperature

500C

e) One Minute Power Frequency withstand:

I. Power Circuit

2500 volts (rms)

II. Control Circuit

2500 Volts (rms)

Cubicle Colour Finish:

b) Interior

Glossy white.

c) Exterior

Smoke Grey shade No. 692 of IS: 5.

Circuit Breaker:

a) Type

Air break

b) No. of pole

3

c) Voltage & Frequency

415 ( 10%, 50 Hz + 5%

d) Rated Operating Duty

B-3 Min, M-B-3 Min. MB

e) Symmetrical

Interrupting rating

20 kA (rms)

f) Short circuit making

45 kA (peak)

current

g) Short time withstand

current for 1 sec

20 kA (rms) for 1 sec.

duration

h) Operating Mechanism

Current for 1 sec

20 kA (rms) for 1 sec.

Duration

i) No. of auxiliary contacts4 No. & 4 NC contacts for purchasers use on fixed portion of the cubicle.

j) Short circuit breaking current:

I. AC Component

20 kA (RMS)

II. DC Component

As per IS: 13947(Part 2)

Moulded Case Circuit Breaker:

AC System

DC System

a) No. of Poles

4

3

b) Voltage & Frequency

415 ( 10%

250 V

c) Rated Operating Duty

P2

P2

d) Symmetrical interrupting

Rating

20 kA (RMS)

4 kA

e) Short circuit making current45 kA (peak)

--

f) No. of auxiliary contacts

2 No. & 2 NC

2 No. & 2 NC

g) Short circuit breaking current:

I. AC Component

20 kA (RMS)

As per IS

II. DC Component

IS 13947

IS 13947

Meters:

a) Accuracy class

2.5

--

b) One minute power Frequency

withstand test voltage in kV2.0

--

Current Transformers:

a) Type

Cast resin, Bar primary

b) Voltage class and frequency650 V, 50 Hz.

c) Class of insulation

E or better

d) Accuracy class

Class 1, VA adequate for application, but

metering CT

not less than 7.5 VA.

e) Accuracy class

5 P 15, VA adequate for application, but

Protection CT

not less than 7.5 VA.

f) Accuracy class

PS, KPV = 300 V

Differential protection

g) Short time current rating (for CTs associated with circuit breakers):

I. Current

20 kA (rms)

II. Duration

One second

III. Dynamic Rating

45 kA (peak)

IV. One minute power

frequency withstand

2.5 kV (rms)

test voltage

Voltage Transformer:

b) Type

Cast Resin

c) Rate Voltage

Primary

415/3 V

Secondary

110/3 V

d) Method of connection

Primary

Star

Secondary

Star

e) Rated Voltage factor

1.1 continuous, 1.5 for 3 seconds

f) Class of insulation

E or better

g) One minute power frequency

Withstand voltage

2.5 kV (rms)

h) Accuracy class

0.5, not less than 20 VA.

Relay:a) One minute power frequency

withstand test

2 kV (rms)

AC Distribution Board in Control Room:

AC Distribution Board in Outdoor Yard:

Incoming & Outgoing Feeder Cable Sizes:(for a Typical 400/220 kV Substation)Sl.

No.

Description of Cables required

XLPE Cable Size

Overall diameter of cable; tolerance ( 2 mm

A.For AC Distributions

1. For 150 A incoming feeders from Station Service Transformers I & II of 630 kVA

3:3 (1C( 630 sq.mm46 mm/1C

2. 2 (1C( 630 sq.mm46 mm/1C

3. For 800 A incoming & outgoing feeders

3:2 (1C( 630 sq.mm46 mm/1C

4. 2 (1C( 300 sq.mm36 mm/1C

5. For 630 A incoming & outgoing feeders

3:2 (1C( 300 sq.mm36 mm/1C

6. 1(1C( 500 sq.mm41 mm/1C

7. For 400 A incoming & outgoing feeders

3 (1C( 300 sq.mm41 mm/1C

8. 1(1C( 500 sq.mm25 mm/1C

9. For 200 A & 150 A & 125 A incoming & outgoing feeders

10. 220 V Battery chargers & PLCC Battery Chargers[3.5C(70 sq.mm +

3.5C(35 sq.mm ](33 mm + 27 mm)

11. Switchyard lighting panel etc.

12. For 100 A incoming & outgoing feeders3.5C(70 sq.mm33 mm

13. For 63 A incoming & outgoing feeders3.5C(35 sq.mm27 mm

14. For 32 A incoming & outgoing feeders3.5C(35 sq.mm27 mm

BFor DC Distribution Boards

1. For 200 A incoming from Battery Charger I & II for DCDB2C(185 sq.mm39 mm

2. For 32 A incoming & outgoing feeders2C(10 sq.mm20 mm

3. For 16 A incoming & outgoing feeders2C(6 sq.mm18 mm

CONTROL AND RELAY PANELS

Power System Control Systems:

1. Substation Control System (SCS)

2. Power Plant Control System (PCS)

3. Substation Monitoring System(SMS)

4. Supervisory Control And Data Acquisition System (SCADA)

5. Energy Management System(EMS)

6. Distribution Management System(DMS)

Functions of Protective Relaying:

Protective relaying is to remove from service any element of a power system in case of any abnormal conditions like short circuits and earth faults.

Objectives:

i. Reliability:

When a fault occurs the relay shall operate instantly and correctly.

ii. Selectivity:

The relay must act fast with in its primary zone and shall have delayed operation in its back- up zone.

iii. Sensitivity:

The relaying equipment must be sufficiently sensitive so that it operates reliably when required under the actual conditions that produces least operating tendency.

iv. Speed:

It is desirable that the relay operates at the required speed. As per IEEE 100-1984 a high speed relay is one that operates in less than 50 seconds. Modern high speed circuit breaker operates in the range of 17 to 50 milliseconds others operate at less than 83 milliseconds. Thus the totals clearing time (relays plus breaker ranges from 35 to 135 milliseconds.

v. Simplicity and Economic:

A protective relay system shall be kept simple with minimum circuitry. The use of solid state and digital technologies in protective relaying provide much convenient possibility for increased sophistication.

Classification of Relays:Based on FunctionsBased on InputsBased on Operating Principles or Structure:Based on Performance Characteristic

1. Protective relays

2. Monitoring relays

3. Re-closing relays

4. Regulating relays

5. Auxiliary relays

6. Synchronizing relays

1. Current

2. Voltage

3. Power

4. Pressure

5. Frequency

6. Temperature

7. Flow

8. Vibration1. Current balance

2. Multi restraint

3. Product solid state