CENTRAL ELECTRICITY AUTHORITY (TECHNICAL STANDARDS FOR CONSTRUCTION OF ELECTRICAL PLANTS AND ELECTRIC LINES) REGULATIONS, 2010
(1) These regulations may be called the Central Electricity Authority (Technical Standards for Construction of Electrical Plants and Electric Lines) Regulations, 2010.
(2) They shall come into force on the date of their publication in the Official Gazette.
(1) In these regulations, unless the context otherwise requires,--
(a) "Act" means the Electricity Act, 2003;
(b) "Authority" means the Central Electricity Authority established under sub-section (2) of Section 70 of the Act;
(c) "Base Load Operation" means operation at maximum continuous rating (MCR) or its high fraction;
(d) "Basic Insulation Level (BIL)" means reference voltage level expressed in peak (crest) voltage with standard 1.2/50 us lightning impulse wave. Apparatus should be capable of withstanding test wave of basic insulation level or higher;
(e) "Black Start" means the start up of a generating unit or gas turbine or internal combustion (IC) engine based generating set without use of externa
(1) The Electrical Plants and Electric Lines shall be suitable for full range of ambient and other environmental conditions as prevailing at site.
(2) The various parts or components or assemblies of equipment and systems shall be of proven materials with well established physical and chemical properties appropriate to the service as intended.
(3) All equipment and systems installed shall comply with the provisions of statutes, regulations and safety codes, as applicable.
(4) The Electrical Plants and Electric Lines shall be designed to comply with the requirements stipulated in:
(a) Central Electricity Authority (Installation and Operation of Meters) Regulations, 2006;
(b) Central Electricity Authority (
Part- A: Common to all types of Thermal Generating Stations;
Part- B: Coal or lignite based Thermal Generating Stations;
Part- C: Gas Turbine based Thermal Generating Stations;
Part- D: Internal Combustion (IC) Engine based Thermal Generating Stations.
PART- A
COMMON TO ALL TYPES OF THERMAL GENERATING STATIONS
(1) The coal or lignite based thermal generating stations shall be designed to give life of not less than twenty five (25) years. Gas turbine based Stations and IC engine based Stations shall be designed for life not less than fifteen (15) years.
(2) The Station shall comply with all applicable environmental stipulations of Ministry of Environment and Forests (MOE&F) in regard to ambient air quality, gaseous emissions, liquid effluent discharges, solid waste disposal and any other stipulation of the Central Pollution Control Board (CPCB) and State Pollution Control Board (SPCB) in this regard.
(3) Noise level
(a) Noise level at the Station boundary shall not exceed the ambient air quality standard in respect of noise as notified by Ministry of Environment and Forest (MOE&F) and any other stipu
(1) Site selection- The following criteria shall be considered for selection of site for thermal generating stations:
(a) Availability of adequate land for the Station;
(b) Avoidance of proximity to geological faults, high flood zone of rivers or the high tide zones of sea/ backwaters;
(c) Siting criteria prescribed by MOE&F
(d) Availability of required water;
(e) Feasibility of rail, road or other linkages for transportation of fuel and equipment to the site;
(f) Feasibility of power evacuation.
(2) Layout considerations- The following minimum layout requirements shall be complied with as may be applicable for coal
(1) The unit shall give MCR output under the following conditions:
(a) Maximum cooling water temperature at site;
(b) Worst fuel quality stipulated for the unit;
(c) Grid frequency variation of -5% to +3% (47.5 Hz to 51.5 Hz).
(2) The unit shall be capable of base load operation. However, the unit shall also be capable of regular load cycling and two-shift operation. The steam turbine shall be designed for a minimum of 4000 hot starts, 1000 warm starts and 150 cold starts during its life.
(3) The sub-critical unit shall be designed for constant pressure and sliding pressure operation. The supercritical unit shall be designed for sliding pressure operation.
(4)
(1) The steam generator shall normally be based on pulverized fuel combustion and shall be of sub-critical or super- critical type with single pass or two pass or any other proven flue gas path configuration. However, wherever very low grade fuel or coal or lignite with high sulphur content is stipulated, fluidized bed combustion (FBC) based steam generator may also be considered based on Owner's assessment of techno- economics and availability of proposed unit size.
(2) The efficiency of the steam-generator (on high heat value basis) in %, as guaranteed by the manufacturer, shall not be less than the value as arrived with the following formula for the quality of performance coal or lignite:
Minimum steam generator efficiency (%) = 92.5 - [ 50xA + 630(M+9xH) ]
HHV
(1) The steam turbine shall comply with latest versions of relevant International Electro-technical Commission (IEC) standards or equivalent.
(2) The gross turbine cycle heat rate as guaranteed by the equipment manufacturer shall not exceed the following values:
Table 1
Unit rating (MW) Heat rate* (kcal/ kWh) at 100% MCR with motor driven BFP Heat rate* (kcal/kWh) at 100% MCR with turbine driven BFP
50 MW to less than 100 MW** 2280 -
100 MW to less than 200 MW** 2000 -
200 MW to less than 250 MW** 1970 -
250 MW to less than 500 MW** 1955 -
500 MW and above** 1895 1935
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(1) General requirements
(a) For the purpose of design of electrical equipment and systems, an ambient temperature of 50C and relative humidity of 95% shall be considered. The equipment shall be suitable for operation in a highly polluted environment. However, for equipment installed in air conditioned areas, design ambient temperature shall be 35 C.
(b) The telecommunication system shall be based on optical fibre or power line carrier communication (PLCC) or both. Owner's telecommunication equipment provided to transmit the required data of the Station to the procurer of electricity, Regional/ State Load Despatch Centre and Transmission Company shall have matching equipment and compatible communication protocol with the receiving end.
(2) Generator
(1) General
(a) Control and Instrumentation system provided for the Station shall be consistent with modern power station practices and in compliance with all applicable codes, standards, guidelines and safety requirements in force.
(b) The complete thermal, mechanical and electrical functions of the unit shall be remotely controlled from the central control room and those of balance of plant facilities shall be controlled from respective local control room during normal as well as emergency conditions. The number of control areas shall be kept to the minimum with a view to optimizing manpower requirement.
(c) All stand-by auxiliaries shall be designed to start automatically as quickly as possible on failure of running auxiliaries as per process requirement.
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(1) Coal or lignite handling system- The arrangement for transportation of coal or lignite from supply source to the Station may be by rail or other captive systems such as merry go round (MGR), belt conveyor system, ropeway system etc. Further, handling shall comply with the following requirements:
(a) The coal or lignite handling plant capacity shall be such as to meet the day's fuel requirement by its operation in 14 hours. A day's fuel requirement shall be worked out at 100% BMCR using worst coal or lignite plus a margin of 10%.
(b) The coal or lignite handling plant shall be provided with 100% standby streams. Each coal or lignite stream shall be provided with 2x75% or 3x50% paddle feeders (in case of track hoppers) or apron feeders (in case of wagon tippler) and 2x50% crushers with belt feeders. Single set of coal or lignite convey
The design philosophy of civil works shall be based on tech no-economics of various options for the construction techniques.
(1) Geo-technical investigations- Geo-technical investigations required for elastic assessment of foundation geology shall be carried out during investigation stage prior to taking up construction activity. The geo-technical investigations shall include determination of the sub soil type, ground water table etc. Based on these, the type of foundation system, the bearing capacity, the pile parameters, requirement of soil stabilization/ compaction etc., shall be established.
(2) Site levelling- The formation level of the Station shall be kept minimum 1.0 m above the high flood level (HFL) of the site. St is preferable to keep the entire Station at the same level. However, to keep the leveling cost to minimum, differe
(1) The gas turbine(s) shall be installed alongwith heat recovery steam generator(s) and steam turbine except where intended to be used for emergency, black start or only for peaking duty.
(2) Combined cycle gas turbine (CCGT) module, comprising of gas turbine generator(s) and steam turbine generator, shall give its MCR output at the specified site conditions and the design fuel.
(3) The CCGT module shall be capable of base load operation. However, these shall also be capable of load cycling and two-shift operation.
(4) The gas turbine, steam turbine and all rotating auxiliaries shall be suitable for continuous operation within the frequency range of 47.5 Hz to 51.5 Hz.
(5) The design of the equipment and control system shall be suitable for operati
(1) The gas turbine and t auxiliaries shall comply with latest versions of applicable ISO/ ASME codes.
(2) The gas turbine compressor shall have a stable aerodynamic characteristic throughout its operating regime. The operating point in the entire frequency range of 47.5 to 51.5 Hz shall be sufficiently away from surge line so that it is stable at all conditions of load, ambient temperature and blade fouling.
(3) The compressor shall be provided with variable type inlet guide vanes to meet start up/ shutdown requirements, improved part load performance in combined cycle mode of operation and exhaust gas temperature control over a wide range.
(4) Combustion chamber arrangement shall be such as to allow maintenance without dismantling of compressor or turbine section and with minimum dismantling
(1) HRSG shall be suitable for outdoor installation and shall be constructed to form a gas tight envelope to prevent gas leakage.
(2) HRSG shall comply with IBR requirements.
(3) Gas turbine exhaust plenum shall be designed for proper gas velocity and temperature distribution and effective pressure recovery. The exhaust system design shall take into account very rapid start-up and shutdown rate of the gas turbine.
(4) Arrangement for mandatory purging of gas turbine exhaust system and HRSG shall be provided in order to eliminate chances of explosion (puffing) for combined cycle plants envisaged for operation on liquid fuel firing.
(5) The design of HRSG shall be based on finned tube heat transfer banks of superheaters, evaporators, economisers etc.
Steam turbine shall be single or multi pressure, condensing type complying with relevant IEC Standards or equivalent. Other requirements stipulated for coal or lignite based thermal generating stations in Part-B of this Chapter in respect of steam turbine and auxiliaries shall be complied with, as applicable.
Electrical Systems shall meet the requirements stipulated for coal or lignite based thermal generating stations in Part-B of this Chapter in respect of Electrical System, as applicable. However, in case of smaller size of generators, the neutral may be earthed through resistance or voltage transformer.
Control and Instrumentation Systems shall meet the requirements stipulated for coal or lignite based thermal generating stations in Part-B of this Chapter in respect of Control and Instrumentation System, as applicable.
Station water system which includes clarified water system, cooling water system, de-mineralisation system, service water system, potable water system, waste water treatment system shall meet the requirements as stipulated in Part-B of this Chapter in respect of Station Water System, as applicable.
Fire detection, alarm and protection system shall meet the requirements as stipulated for coal or lignite based thermal generating stations in Part-B of this Chapter in respect of fire detection, alarm and protection system, as applicable.
Civil works shall meet the requirements as stipulated for coal or lignite based thermal generating stations in Part-B of this Chapter in respect of civil works, as applicable. However, stack shall be of steel construction and its height shall meet the requirements of MOE&F and any other stipulation of the CPCB and SPCB in this regard.
(1) The IC engine based thermal generating stations shall comprise of generating sets (Gen- sets) and associated facilities These shall use liquid fuel viz. heavy fuel oil, diesel, bio oil or natural gas or a combination of gas and liquid fuel.
(2) The IC engine based thermal generating stations shall be suitable for indoor installations either on pads or on reinforced concrete foundations. Smaller IC engine based generating sets (Gen- sets) may be skid mounted. All the facilities required for receiving and feeding the inputs such as fuel, lubricants, water, air etc. and the control panel and synchronizing panel shall be provided.
(1) The Gen-sets shall be capable of base load operation. However, these shall also be capable of load cycling and single shift or two-shift operation.
(2) The IC engine and all rotating auxiliaries shall be suitable for continuous operation within the frequency range of 47.5 Hz to 51.5 Hz.
(3) For grid connected generating stations, design of the equipment and control system shall be suitable for operation of the Gen- set in automatic load frequency control.
(4) The Gen- set shall have auto start, auto loading, auto stop features and capable of parallel operation in the power distribution system with synchronizing facilities.
(5) The gross heat rate of Gen- set as guaranteed by the manufacturer shall not exceed the following values:
(1) The IC engine and auxiliaries shall comply with latest versions of applicable IS/ ISO/ BS (British Standard) or equivalent codes.
(2) Turbo charger, if applicable, shall be of robust construction, suitable of being driven by engine exhaust. It shall draw air through air filter and have adequate capacity to suit engine requirements
(3) The IC engine shall be capable of satisfactorily driving the generator at 10% over load at rated speed for one hour in any period 12 hours of continuous running for applications other than base load operation.
(4) The IC engine shall be provided with suitable self-starting device.
(5) The IC engine shall be provided with an air intake filtration system to deliver filtered air of quality suitable for the engine.
(1) Liquid fuel storage capacity shall be provided corresponding to 15 days requirement.
(2) Liquid fuel unloading, storage and forwarding system shall be designed to comply with all applicable statutory requirements.
(3) Each IC engine or a group of IC engines installed at one location shall be provided with on-line fuel flow metering device to monitor fuel consumption.
Electrical requirements stipulated in Part- B of this Chapter shall be complied with for switchgear, transformers, cables, protections etc. as applicable. However, in case of smaller size of generators, the neutral may be earthed through resistance or voltage transformer.
Suitable fire detection, alarm and protection system shall be provided for the Station.
This Chapter stipulates the minimum technical requirements for construction of Hydro-Electric Generating Stations for various types of schemes i.e. Run-of-river scheme, Storage scheme, Pumped storage scheme, Canal head scheme etc. with installed capacity of 25 MW and above. For hydro- electric generating Stations having installed capacity less than 25 MW, the stipulations as appropriate, shall apply.
(1) While designing hydro- electric projects, the life of the civil works shall not be less than one hundred (100) years, while that of main electro-mechanical generating equipment i.e. turbine, generator, transformers, auxiliaries, etc. installed shall not be less than thirty five (35) years.
(2) The Station shall be designed for unconstrained operation over maximum net head and minimum net head, specified silt conditions wherever applicable, and full range of ambient and other environmental conditions.
(3) The dimensions of the power house, turbine settings, speed rise, pressure rise, run-away speed, etc. shall be governed by the limits specified in relevant IS.
(4) The chemical analysis of water and silt data including the petrographic analysis shall be taken into consideration while design
(1) General layout of the Station shall be developed considering the proper utilization of space, functional requirements, future extensions and considering requirements of space during construction stage. The layout of the Station shall be compact so as to economise on the use of materials.
(2) Maintenance facilities shall be provided as required for assembly, disassembly and handling during maintenance of ail important equipments and auxiliaries.
(3) Fire escape staircases/ galleries shall be provided in main Station building/Cavern. Each equipment room shall be provided with alternate exits to be used in case of fire/ accidents as per requirements of the Factory Act and other statutory requirements.
(4) Adequate provisions in layout shall be made for protection of power house against floodi
(1) The unit shall be capable of giving the rated output continuously as specified by the manufacturer at the rated design head and rated discharge and shall be capable of operating between the minimum and maximum head specified by the purchaser and ambient temperature at site as specified.
(2) The maximum continuous overload capacity of the unit at the generator terminals during the high head conditions or high discharge conditions or both as guaranteed by the manufacturer shall be based on hydraulic parameters of the Station.
(3) The unit and all the associated auxiliaries shall be suitable for continuous operation without any restriction within a frequency range of -5% to +3% (47.5 Hz to 51.5 Hz). All the equipment driven by the electric motors shall give their rated performance even at a power supply frequency of 47.5 Hz.
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(1) The hydraulic turbine shall comply with latest versions of relevant IS/ IEC standards.
(2) Turbine shall have smooth and quiet operation. The vibrations, pressure pulsations and power fluctuations shall be within the limits specified in relevant standards. The amplitude of the vibrations at the shaft shall not exceed the limits specified in relevant ISO standards.
(3) The type and rotational speed of the turbine shall be selected considering the range of head, specific speed, head variation etc. In case two different types of turbines are found suitable for the range of head envisaged (overlapping zone of net head) at a particular site, the selection of turbine shall be based on the techno economic considerations taking into account the aspects such as head variation, civil costs, part load operation, operation and maintenance, effic
(1) Microprocessor based digital governing system shall be used for regulating the flow of water to the turbines for the control of active power (MW) thus providing the requisite speed/frequency control and load control. The speed sensing device shall be provided with the requisite redundancy. The performance requirements of the governing system shall be governed by relevant IS / IEC standards
(2) High pressure oil system shall be provided for each turbine for the operation of wicket gates/nozzle/deflector servomotors through governors and for the control of main inlet valve (MIV). Piston type accumulator with nitrogen bottles shall be used for pressures higher than 60 kg/cm2
(3) Separate oil pressure systems shall be used for the control of turbine and the control of MIV.
(4) The sizes of var
(1) The main inlet valve of either butterfly or spherical type shall be provided depending on head conditions.
(2) The spherical and butterfly valves shall comply with the requirements of latest versions of relevant IS / IEC standards.
(3)The valves shall have service seal on downstream side and maintenance seal on upstream side.
(4) The opening and closing of spherical / butterfly valves shall normally be done under balanced water condition. Suitable number of air release valves/ anti-vacuum valves shall be provided at the appropriate location on the downstream side to allow the air trapped in the penstock to escape when it is filled with water through the bypass valve and for supplying/ admitting the air when the valve is suddenly closed.
(5) The
(1) Electric overhead travelling (EOT) cranes
(a) The EOT cranes shall comply with the requirements and standards of latest versions of relevant IS/ IEC standards. The span of the crane shall be fixed in such a way that the travel and lift of the main and auxiliary hooks of the crane as well as the hook limits shall be adequate for the assembly and disassembly of the main equipment in the power house. The lift above the service bay (upper limit) shall be adequate to hoist and carry the rotor of the generator and to assemble and disassemble the transformer. The lift below the service bay (lower limit) shall be fixed in such a way as necessary for assembly and disassembly of the turbine.
(b) The hook capacity shall be taken as 10% more than the maximum weight to be lifted inclusive of the weight of the lifting beam. If the maximum weight t
(1) General requirements
(a) For the purpose of design of equipment or systems, an ambient temperature of 40C or higher as applicable to Station site and relative humidity of 95% shall be considered.
(b) All equipments shall be suitable for rated frequency of 50Hz with a variation of -5% and +3%. The overall system shall be designed considering maximum voltage variation and combined variation of voltage and frequency as specified in Central Electricity Authority (Technical Standards for Connectivity to the Grid) Regulations, 2007.
(c) The telecommunication system shall be based on optical fibre or power line carrier communication (PLCC) or both. Owner's telecommunication equipment provided to transmit the required data of the Station to the procurer of electricity, Regional/ State Load Despatc
(1) General
The control and instrumentation system provided for the Station shall be consistent with modern power Station practices and in compliance with all applicable codes, standards, guidelines and safety requirements.
(2) Control and protection system
(a) Unit and station control system shall be microprocessor / computer based distributed digital control system interconnected through fibre optic cables or copper cables (for distances less than 100 metres) having hundred percent redundancy. Each generating unit shall have independent programmable logic controller with requisite redundancies. The control of each unit from the unit control board shall be independent of each other.
(b) The following control, operation and monitoring points shall b
Following provisions shall be made for protection of Power House against flooding:
(1) Suitable number of submersible pumps with provision for automatic starting by means of level switches shall be provided at main inlet valve (MIV) floor, in addition to drainage and dewatering pumps as per Regulation 36(3).
(2) The control panels for dewatering and drainage pumps shall be located at a floor higher than that of turbine floor.
(3) Suitable float switches shall be provided in power house building to give closing signal to the MIV in the event of inundation of power house due to any reason including penstock rupture or leakage in penstock or for some other reasons.
(4) The station service transformers and station service boards shall be located at high
Part - A: Sub-Stations and Switchyards (66kV and above)
Part - B: Sub-Stations (33/11 kV, 33/22kV and 22/11kV)
Part - C: Distribution Sub-stations (DSS)
(1) The rated rupturing capacity of the circuit breaker to be installed at any new sub-station or switchyard shall be at least 25% higher than the calculated maximum fault level at the bus to take care of the increase in short circuit levels as the system grows. The rated breaking current capability of switchgear and breakers to be installed at different voltage levels, based on available capacities of the breakers, shall be considered as shown in Table 6 below.
Table 6
66 kV 31.5 kA (for 1 sec.)
110/132 kV 31.5 kA (for 1 sec.)
220 kV 40 kA (for 1 sec.)
400 kV 40 or 50 kA (for 1 sec.)
765 kV 40 or 50 kA (for 1 sec.)
(1) The sub-station or switchyard can be a conventional air insulated sub-station (AIS) or a gas insulated sub-station (GIS) or a hybrid sub-station. The factors to be taken into account for designing sub-stations shall be as under.
(a) The choice of site for a sub-station or switchyard shall be based on technical, economic and environmental factors. The approximate location shall be determined on grid considerations. The new sub-station shall enhance the operational flexibility, system reliability and transmission or transformation capacity after becoming a part of the network.
(b) Land area required shall be considered based on the present requirement and the future expansion on a 10 to 15 year scenario.
(c) Reactive compensation as indicated by system studies shall be provided. The series c
(1) System design parameters
(a) The system design parameters of sub-stations and switchyards shall be as given below in Table 9.
Table 9
Parameter 66 kV 110 kV 132 kV 220 kV 400 kV 765 kV
Highest system voltage (kV) 72.5 123 145 245 420 800
Rated frequency 50Hz 50Hz 50 Hz 50 Hz 50 Hz 50Hz
No. of phases 3 3 3 3 3 3
Rated insulation levels
(i) Full wave impulse withstand voltage (1.2/50 micro sec.) (kVpeak) 325 550 650 1050* 1425* 2100*
(ii) Switching impulse withstand voltage (250/ 2500 micro sec.) dry and wet (kVpea
The design parameters given at Regulation 43 (1) shall be applicable for the AC equipment installed in the HVDC terminal station to be developed for bulk power transfer over long distances or asynchronous connections (back to back) between areas operating with different frequency regimes. The system parameters given for 400 kV or 220 kV or 132 kV AC system shall be applicable for the commutation voltage for both HVDC back to back and HVDC long distance transmission systems. Technical details of HVDC terminals/ stations are given in Schedule- VI.
(1) For HVDC system, one DG set with auto start facility shall be provided per pole as emergency backup. Batteries and battery chargers shall be provided for auxiliaries, DC power supplies, valve hall ventilation systems, etc. Other electrical auxiliaries provided shall include illumination, public address and communication system, UPS etc. The mechanical auxiliaries shall include air conditioning, ventilation systems, fire fighting including very early smoke detector acquisition (VESDA) system for valve hall, water supplies, etc.
(2) All auxiliaries shall give full output at voltage variation of 10% and frequency variation of -5% to +3%.
Diagnostic equipment shall be provided to assess the health of various equipment in substations and switchyards of 132kV and higher voltages. On-line diagnostic equipment shall be dedicated type for those critical equipment the health of which is to be monitored continuously. Portable type on-line diagnostic equipment and off-line diagnostic equipment shall be provided for one or a cluster of substations or switchyards, depending upon the size of the substations or switchyards. The diagnostic equipment shall include dissolved gas analyzer, winding resistance meter, and frequency response analyzer for transformers and reactors, capacitance and tan-delta measuring units for transformers, reactors and instrument transformers, circuit breaker analyser including dynamic contact resistance meter, and leakage current monitor for surge arrester, and relay testing kit. Other necessary diagnostic equipment may be provided at the discretion of the Owner.
The system shall conform to the design parameters indicated in Table 14 below:
Table 14
Parameter 33 kV 22 kV 11kV
Nominal system voltage (kV) 33 22 11
Highest system voltage (kV) 36 24 12
System earthing Solidly earthed system Solidly earthed system Solidly earthed system
Frequency (Hz) 50 50 50
Lightning impulse withstand voltage (kVpeak). 170 125 75
Power frequency withstand voltage (dry) (kVrms) 70 50 28
(1) The sub- station shall be designed and constructed complying with the requirements mentioned in these standards, applicable Indian Standards (IS) as well as other rules and regulations as per latest amendments. The design and construction of the sub-stations shall be such that they perform their intended functions. In case of conflict, the more stringent provisions shall prevail.
(2) The sub-station shall be indoor/ outdoor or underground type depending upon the site requirement. The sub-station shall be either air insulated (AIS) or gas insulated (GIS), as the case may be.
(3) The sub-stations in urban areas shall be provided with supervisory control and data acquisition (SCADA) system for monitoring and control.
(4) The 33/ 11 kV or 33/ 22 kV or 22/ 11 kV sub-stations shall, at least hav
(1) The selection of site for 33/11 kV or 33/ 22 kV or 22/11 kV sub-station shall be made after taking into consideration the capacity and location of the feeding grid sub-station, load in the area, spatial load forecast, demographic factors, the existing network configuration, etc. and the economic, and environmental considerations.
(2) The selection of the site of the sub-station shall be done on the basis of the following:
(a) The site shall be near the load center;
(b) The site shall be such that it is convenient for terminating extra high voltage (EHV)/ high voltage (HV) lines/ cables;
(c) The site shall not be in a low-lying area to avoid flooding during the rains;
(d) The site shall be easily appro
The layout of the sub-station shall be such that:
(1) The incoming and outgoing feeders are easily taken to and from the sub-station structures.
(2) Equipment maintenance shall be possible without interrupting the entire supply.
(3) The layout shall be economical and shall not hinder future expansion.
(1) Switching arrangements shall ensure operational flexibility, system safety and reliability.
(2) Single bus, single bus with bus sectionalizer, main and transfer bus, double bus or mesh arrangement shall be adopted as per requirement.
The system configuration shall be radial, ring or combination of both as per requirements. The radial configuration shall be minimized to improve reliability. In densely loaded city centers, and for essential services and installations, the system shall be of ring configuration.
(1) The control room building can be single storey or double storey or underground depending upon availability of space.
(2) While selecting equipment for the sub-station, de-rating due to increase in altitude and for cables due to depth of burial in the ground shall be given due consideration as per the altitude/depth of burial at the site.
(1) The transformers and fittings and accessories shall comply with the relevant IS.
(2) The 33/ 11 kV or 33/ 22 kV or 22/11 kV transformers shall have delta star or delta-zigzag winding connection. At existing sub-stations, the percentage impedance, vector groups, on load tap changer connection and range etc. of the new transformer shall match with that of the existing transformer.
(3) The preferred ratings for 33/ 11 kV or 33/ 22 kV or 22/ 11 kV transformers shall be 1, 1.6, 3.15, 5, 6.3, 8, 10, 16 and 20 MVA.
(4) The transformers shall be three-phase type.
(5) The transformer can be oil filled, gas filled epoxy cast dry type or ventilated dry type depending on whether it is installed indoor or outdoor. Outdoor dry-type transformer may be non-vent
(1) Bus-bars shall be of Rigid type or Strain type.
(2) A bus-bar shall be able to carry the expected maximum load current continuously without exceeding the temperature rise limit as per relevant IS. The capacity of a bus-bar shall also be checked for maximum temperature rise of the conductor under short circuit conditions.
(3) The bus-bar connections and insulator supports shall be mechanically strong and bus-bars shall be supported so as to withstand the stresses generated by vibrations and short circuits.
(4) Aluminium used for the tubes of rigid type bus-bars shall conform to relevant IS.
(1) Structures shall be provided for:
(a) Incoming and outgoing gantries and/or cable supports and terminations;
(b) Circuit breakers, isolators, fuses, insulators, CTs and PTs (potential transformers);
(c) Bus-bar/insulators.
(2) Switchyard structures to support buses, electrical equipment and termination of line conductors shall be made of fabricated steel, reinforced cement concrete (RCC) or pre-stressed concrete (PSC), rail or rolled steel joist (RSJ) depending on technical and economic considerations.
(3) The structures shall be able to withstand tension of conductors and load of the equipment and accessories without guys or stays.
(4) The steel structures
(1) Adequate insulation is of prime importance for ensuring reliability of supply, safety of personnel and equipment, etc. The station design shall be such that number of insulators is minimum but at the same time reliability of supply is ensured.
(2) The insulators shall be of porcelain or polymer type.
(3) Suitable means shall be provided to accommodate conductor expansion and contraction and there shall not be any undue stress on any part or equipment due to temperature change.
(4) The minimum specific creepage distances for different pollution levels shall be as per Table 12 at Regulation 43.
(1) The post insulators shall be of pedestal type or Solid Core Station type and shall conform to relevant IS.
(2) In the areas where problem of insulator pollution is expected (such as near sea or thermal power station, railway station, industrial area, etc.) special insulators viz. semi conducting glazed porcelain or polymer insulators with higher leakage resistance and creepage distance shall be used. The special coating on the insulators may be used as per requirement.
(1) Circuit breakers (CBs) shall comply with the provisions of relevant IS. The circuit breakers shall be SF6 or vacuum type. Normally vacuum type circuit breakers shall be used for voltage levels of 33 kV and below. The rated voltage for the circuit breakers shall be 36 kV, 24 kV and 12 kV for 33 kV, 22 kV and 11 kV systems respectively.
(2) Rated short time current rating of 33 kV CBs shall not be less than 25 kA for 1 second and for 22 kV or 11 kV CBs shall not be less than 16 kA for 1 second. In case of rural areas for 11 kV CBs, this shall not be less than 12.5 kA for 1 second.
(3) The operating mechanism shall be motor operated spring charged type or magnetic actuator type. The circuit breaker shall be provided with anti pumping and trip free features.
(4) The 33 kV, 22kV and 11 kV switc
(1) The isolators shall comply with relevant IS. The rated current shall be at least 630 A at 36 kV and 24 kV. For 11 kV system, isolating switches of 400 Amps at 12 kV shall be used. The isolators shall be gang operated type.
(2) The frame of each isolator switch shall be provided with a separate earthing terminal for each phase for connection to an earthing conductor.
(3) The operating mechanism for the isolators and the controlling circuit breaker shall be interlocked so that the isolators cannot be opened unless the corresponding breakers are in open position.
(4) Earthing switches shall be provided at various locations to facilitate maintenance. Main blades and earth blades shall be interlocked, both electrically and mechanically.
(5) The earth
(1) The control and relay panels shall contain control and metering equipment, relays and annunciation systems for incoming feeders, outgoing feeders, bus bars, switch-gears, instrument transformers and capacitors etc.
(2) The control and relay panel shall consist of separate cubicle with side covers made of sheet steel and shall be complete with internal wiring, terminals, ferrules and illumination operated with door off and on switch.
(3) The panel shall be suitable for floor mounting and shall be completely dust and vermin proof.
(4) The panel shall be provided with:
(a) Suitable over current and earth fault relays to protect the equipment and system against short circuit current and earth fault current.
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(1) The surge arrester (SA) which responds to over-voltages without any time delay shall be installed for protection of 33 kV, 22 kV and 11 kV switchgear, transformers, associated equipment and 33 kV, 22 kV and 11kV lines.
(2) Station class, heavy duty, gapless metal oxide (ZnO) type surge arresters in general shall be provided on the buses, high voltage and low voltage sides of all transformers and on the incoming terminations of 33/ 22 kV lines. The arresters shall conform to relevant IS.
(3) Surge arresters shall be provided at the junction of overhead line and under ground cable. These shall also be installed on 11 kV overhead lines, both at sending end and terminating end.
(4) Surge arresters shall be single-phase units suitable for outdoor duty. These arresters shall draw negligible curr
(1) Current transformers (CTs)
(a) Current transformers shall comply with relevant IS.
(b) The rated currents and ratio, the number of secondary cores (protection/metering), accuracy class, burden, secondary winding resistance, knee point voltage, instrument security factor and excitation current shall be as per the requirements of the protection and metering system.
(c) The primary side rating shall depend on the rating of the power transformer of the sub-station. Current transformers with secondary side rating of 1 Amps or 5 Amps shall be provided. Where the distance between the primary equipment and relay panel is large, CT of 1 Amp secondary current may be used to avoid large VA (volt ampere) burden on the CT.
(d) The CT may be oil filled or res
(1) Control room shall be provided to house the control and relay panels and all other indoor equipment, and measuring and recording instruments required for control and operation of the sub-station.
(2) Adequate space shall be provided for the operation and maintenance staff.
(3) Provision of space for future expansion shall also be kept.
(1) Earthing shall be provided for:
(a) Safety of personnel;
(b) Preventing and minimizing damage to the equipment as a result of flow of heavy fault currents;
(c) Improving reliability of power supply.
(2) Earthing shall be carried out in accordance with relevant IS and Central Electricity Authority (Measures relating to Safety and Electricity Supply) Regulations as and when these are notified by the Authority.
(3) The step and touch potentials shall be within safe limits.
(1) Shunt capacitors shall be connected on secondary side of 33/11 kV, 33/22 kV or 22/11kV transformers.
(2) Capacitors and the residual voltage transformer shall be as per relevant IS.
(3) The capacitors shall be of automatic switched type for sub-stations of 5 MVA and higher capacity.
(4) Where un-switched (fixed) capacitors are provided, the rating shall be chosen so as to prevent over compensation during off peak periods.
(5) Each capacitor unit shall be provided with a built-in discharge resistor of adequate rating to discharge the residual voltage as per relevant IS.
(6) The capacitors shall be fixed firmly to the supporting structure to make them immovable.
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voltage rating shall be provided.
(2) Power cables shall be cross linked poly ethylene (XLPE) insulated, poly vinyl chloride (PVC) sheathed type conforming to relevant IS. Cables shall be flame retardant low smoke (FRLS) type. Cables shall be de-rated for the site's ambient and ground temperature, grouping and soil resistivity as per IS. Proper attention shall be given to ventilation/heat dissipation aspects particularly in case of HV cables.
(3) The control cables shall be of copper and conform to relevant IS.
(4) Cables shall not be laid directly on the trench floor.
(5) The cables shall be segregated by running in separate trenches or on separate racks, with the highest voltage class cables laid at the highest racks/tiers.
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(1) A dedicated and reliable telecommunication system i.e. radio, mobile telephone, satellite or a combination of these shall be provided, besides usual public communication and local public address (PA) system.
(2) The radio communication network shall be in the very high frequency (VHF)/ ultra- high frequency (UHF) frequencies.
State-of-art systems such as supervisory control and data acquisition system (SCADA) and data acquisition system (DAS) shall preferably be provided in the 33 kV or 22 kV sub-stations, associated feeders and distribution transformers for improving the operational flexibility, minimizing restoration time of power supply and preventing overloading of lines and transformers in real time mode.
(1) DC supply arrangement- The battery charger, battery and load shall be connected in parallel and work as a system.
(2) Battery
(a) The 24V/ 30V/ 48V DC batteries shall be stationary lead acid or nickel cadmium type. The capacity and discharge rate shall be as per the load requirement.
(b) The batteries shall conform to relevant IS.
(3) Battery charger- The battery chargers shall be of static type. The battery charger shall be capable of continuous operation at the rated load in float charging mode. The charger in boost charging mode shall be capable of boost charging the associated DC battery at the desired rate.
(4) Auxiliary power supply transformer- An auxiliary power supply transformer of adequate
Fencing shall be provided around the sub- station. A metalled approach road to transport the equipment should be provided leading from the main road.
Energy efficient lighting system shall be provided at the sub- station. The lighting system shall comprise of the following:
(1) AC normal lighting- AC lights shall be connected to AC lighting panels. All the lights connected to the AC lighting system in different areas shall be connected to the main lighting distribution boards (LDBs).
(2) DC emergency lighting- Emergency lighting operated on the DC system shall be provided in strategic locations viz. control room, battery room, passages etc.
(1) Proper attention shall be given to isolation, limiting and extinguishing of fire so as to prevent damage to equipments, reduce chances of serious interruption of power supply and ensure safety of personnel. The layout of the sub- station itself shall be such that the fire shall not spread from one to other equipment and areas as far as possible.
(2) Fire hydrant, carbon dioxide (CO2) type fire extinguisher or dry chemical powder type fire extinguisher conforming to relevant IS shall be provided as per site requirement.
(1) The system shall conform to the design parameters indicated in Table 15 below:
Table 15
Parameter 33 kV 22 kV 11kV 0.415 V
Nominal system voltage (kV) 33 22 11 0.415
Highest system voltage (kV) 36 24 12 0.450
System earthing Solidly earthed system Solidly earthed system Solidly earthed system Solidly earthed system
Frequency (Hz) 50 50 50 50
Lightning impulse withstand voltage (kVpeak) 170 125 75 -
Power frequency withstand voltage (dry) (kVrms) 70 50 28 3
(2) The distribution sub- stations (DSS) shall normally be located ne
(1) The transformer shall conform to relevant IS.
(2) The transformer can be oil filled or dry type depending on requirements. In indoor installations, installations under stilts, rooftop and underground installations the transformer shall be only dry type.
(3) Energy efficient transformers made of high grade cold rolled grain oriented (CRGO) steel or amorphous material shall be used. Scrap CRGO material shall not be used for manufacturing of transformers.
(4) (a) The maximum losses of oil filled distribution transformers shall not exceed as that for at least three star rating transformer specified by Bureau of Energy Efficiency (BEE), wherever applicable.
(b) For those kVA rating of transformers, for which losses are not specified by BEE, the m
(1) For transformer upto 200kVA, tapping shall be provided as per relevant IS.
(2) For ratings higher than 200 kVA, tapping shall be provided on the higher voltage winding within range of (+) 5.0% to (-) 10.0% in steps of 2.5%.
(3) Tap changing shall be carried out by means of an externally operated self position switch and when the transformer is in de-energized condition. Each tap change shall result in variation of 2.5% in voltage. Provision shall be made for locking the tapping switch handle in position. Suitable Aluminum anodized plate shall be fixed for tap changing switch to know the position number of the tap.
(1) The transformer shall be mounted on a single pole, H pole structure or on a plinth depending upon site requirements, size and weight of the transformer.
(2) Direct single pole mounting shall be used for transformers upto 25 kVA only.
(3) The transformers of more than 25 kVA and upto 250 kVA can be mounted on H pole structure or on plinth. Transformers above 250 kVA shall be mounted on plinth only.
(4) The structures shall be provided with anti-climbing devices and danger board.
(5) The plinth shall be higher than the surroundings. The plinth foundation shall be of concrete.
(6) Plinth mounted distribution sub-stations shall be adequately protected by fencing so as to prevent access to the equipment by
(1) Surge arresters shall normally be installed on the high voltage side of the transformer connected to overhead lines. Surge arrester shall also be provided on the low voltage side in areas of high isoceraunic activity.
(2) Surge arresters of rating 9 kV on 11 kV, 20 kV on 22 kV and 30 kV on 33 kV outdoor type shall be used for diverting the lightning surges to earth.
(1) LT distribution box consisting of breaker and fuse cutouts conforming to relevant IS shall be provided from where distribution feeders shall be taken out.
(2) The size of the box shall be suitable for accommodating moulded case circuit breaker (MCCB), fuse cutouts, cable connectors, bus-bars etc.
(3) The distribution box shall be mounted at a height of 1.5 to 2 metres for pole mounted distribution transformers while the feeder pillar box can be installed at ground level, with adequate clearance.
(4) The capacity of lugs for cables, connecting strips, bus bars shall be as per requirement.
(1) 33/ 0.4 kV DSS and 22/ 0.4 kV DSS
(a) Suitable high rupturing capacity cartridge fuse or moulded case circuit breakers (MCCB) or miniature circuit breakers (MCB) or air circuit break switch (ACB) shall be provided on low voltage side.
(b) The high voltage side of these transformers shall be protected by circuit breakers or drop out fuses.
(2) 11/ 0.4 kV DSS
(a) Suitable high rupturing capacity cartridge fuses or moulded case circuit breakers (MCCB) or miniature circuit breakers (MCB) or air break switch shall be provided on low voltage side for transformers of 100 kVA and above. The high voltage side of these transformers shall be protected by drop out expulsion type fuses or circuit breakers.
(b) Hor
(1) Pipe earthings or rod earthing shall be provided for the distribution sub- station complying with relevant IS. Three (3) Nos. earth pits with three grounding electrodes shall be provided. Adequate quantity of charcoal and salt shall be used to keep the earth resistance low.
(2) Earth connections shall be made as under:
(a) To one of the earth electrode:
One direct connection from the high voltage surge arrester and another direct and separate connection from low voltage surge arrester if low voltage surge arrester is provided.
(b) To each of the remaining two electrodes:
(i) Separate connection from the neutral side of the transformer.
(ii) Transformer body
(1) The XLPE cables shall be used for connecting LT supply from transformer bushings to the LT circuit breaker in the distribution box and for taking out outgoing feeders from the fuse units to the overhead lines. All cables shall be as per relevant IS and IS marked.
(2) The LT cables may be armoured or unarmoured for transformers rated less than 100 kVA and shall be armored for transformers of 100 kVA and higher ratings.
(3) The cables shall be properly clamped to the support without damaging the insulation.
(4) A loop arrangement shall be made at the connecting end and laying of cables shall be in such a way that rain water does not enter.
(1) Meters shall be provided on the distribution transformer (LV side) for energy audit purposes of the corresponding LV network.
(2) The installation of meters shall be in conformance to the Central Electricity Authority (Installation and Operation of Meters) Regulations, 2006.
(1) Where the power factor is low, reactive compensation shall be provided on the distribution transformers by fixed or automatic switched type capacitors of adequate rating.
(2) In case of fixed capacitors it shall be ensured that the rating of the capacitors is such as to prevent over compensation during off peak period.
(3) In cases where loads fluctuate very fast, a suitable dynamic compensation like static compensator (STATCOM)/ thyristor switched capacitors shall be considered.
(4) In loads which are rich in harmonics, suitable harmonics filters or detuned filter banks shall be considered.
Part - A: Electric Lines (66 kV and above)
Part - B: Electric Lines (33 kV and below)
(1) Whenever a new transmission line is planned and constructed, the Owner shall ensure that the proposed new installation is compatible with the existing power system and is suitable for becoming, on commissioning, a natural and integral part of the power system. The overall performance and output as well as detailed operating characteristics and specifications of the installation shall conform to the rest of the power system i.e. the design and construction features shall be compatible with the system to which the new installation will be connected.
(2) The Owner shall ensure tie-up arrangements which are necessitated by the proposed installation and which must be carried out simultaneously by other entities before the new installation is commissioned and connected to the power system. The owner connecting his new installation shall abide by the Central Electricity Authority (Tec
(1) The transmission system shall be planned in an integrated manner and optimized considering the total network under central transmission utility (CTU) and state transmission utility (STU).
(2) The adequacy of the transmission system shall be tested for one or more load generation scenarios comprising of peak and off peak conditions in summer, winter and monsoon seasons.
(3) Right of way for transmission lines shall be optimized keeping in view the corridor requirement for the future by adopting suitable alternative of multi-circuit or multi-voltage lines as applicable.
The transmission line route shall be selected keeping in view the following:
(1) Routing of a transmission line through protected or reserved forest shall be avoided. In case it is not possible to completely avoid the forests or areas having large trees, keeping in view the overall economy, the route shall be aligned in such a way that cutting of trees is minimum. Routing of a transmission line through National Parks or Wild Life sanctuaries should also be avoided.
(2) Restricted areas such as civil and military airfields shall be avoided. Care shall also be taken to avoid aircraft landing approaches.
(3) The line routing should avoid large habitations, and densely populated areas.
(4) It shall be ensured that all statutory requirements stipulated u
(1) Salient technical particulars and requirements of transmission lines
(a) Electrical Design Parameters of the Transmission Lines
(i) The electrical design parameters of the transmission lines for altitude upto 1000 m above mean sea level (MSL) shall be as indicated in Table 16 below:
Table 16
Parameter 66 kV AC 132 kV AC 220 kV AC 400 kV AC 765 kV AC 500 kV DC
Nominal voltage (kV) 66 132 220 400 765 500
Highest system voltage (kV) 72.5 145 245 420 800 525
Full wave impulse withstand voltage (1.2/50 micro sec.) (kVpeak) 325 650 1050 1550 2400 1800
Power frequency withsta
(1) The lines shall be constructed keeping in view the prime factors of safety as well as electrical and mechanical design considerations.
(2) The Owner shall ensure tie-up arrangements which are necessitated by the proposed installation and which shall be carried out simultaneously by other entities before the new installation is commissioned and connected to the existing power system network. The Owner who is connecting his new installation has to abide by the Central Electricity Authority (Technical Standards for Connectivity to the Grid) Regulations, 2007.
(1) The electrical design parameters of the electric lines for altitude upto 1000 m above MSL shall be as indicated in Table 19 below:
Table 19
Parameter 33 kV 22 kV 11 kV 0. 415 kV
Nominal system voltage (kV) 33 22 11 0.415
Highest system voltage (kV) 36 24 12 0.450
System earthing Solidly earthed system Solidly earthed system Solidly earthed system Solidly earthed system
Frequency (Hz) 50 50 50 50
Lightning impulse withstand voltage (kVpeak) 170 125 75 -
Power frequency withstand voltage (kVrms) in dry condition 75 50 28 3
(2)
(1) The system shall be constructed so as to ensure:
(a) voltage conditions are within permissible levels;
(b) improvement of reliability and security of power supply;
(c) improvement in quality of supply;
(d) adequate capacity for load growth for next 5 years.
(2) Independent feeders shall be provided for essential loads of 5 MVA and above such as water works, hospitals, defence, railways, airports and other sensitive installations and for selected consumers on request.
(3) Separate rural feeders for feeding irrigation load and domestic load shall normally be provided.
(4) Composite lines (i.e. lines having differen
(1) The route of the electric line shall be as short as possible.
(2) The routing of an electric line through protected and reserved forest shall be avoided. In case it is not possible to completely avoid the forests or areas having large trees, keeping in view the overall economy, the route shall be aligned in such a way that cutting of trees is minimized.
(3) The routing of an electric line through National Parks and Wild Life Sanctuaries shall be avoided.
(4) Restricted areas such as civil and military airfields shall be avoided. Care shall be taken to avoid aircraft landing approaches.
(5) The 33 kV or 22 kV line route shall be such as to avoid large habitations, and densely populated areas.
(6) The l
(1) The electric lines shall be designed and constructed complying with the requirements mentioned in this standard, applicable Indian Standards as well as other rules and regulations as per latest amendments. The design and construction of the electric lines shall be such that they perform their intended functions.
(2) Extension of existing lines shall be carried out after ensuring that the limits of voltage variations on the lines are not exceeded.
(3) The reliability and security of supply shall be improved by use of sectionalizers, auto re-closers, ring main units (RMUs) and fault passage indicators as per techno economic considerations.
(1) The supports shall be poles or narrow based lattice towers with fully galvanised structure as per site requirement.
(2) Poles may be used for 33 kV, 22 kV, 11 kV and LT lines (lines below 500 V) as per requirement. The poles shall be pre-cast concrete (PCC) pole, pre-stressed cement concrete (PSCC) pole, rolled steel joist, rail pole or steel tubular pole as required, provided PCC and PSCC poles shall not be used at cut-points and as end poles.
(3) Poles shall conform to relevant IS as the case may be.
(4) Concrete poles shall be preferred in plain areas.
(5) In hilly areas appropriate snow or ice loading shall be considered for design of poles and towers.
(6) For locations involving long spans or hig
(1) Line span shall be decided taking into consideration topography, wind pressure, type of support, conductor configuration and ultimate tensile strength of conductor.
(2) The span shall be within the range specified by IS.
(3) Uniform span shall be maintained as far as possible between consecutive pole structures.
(4) While constructing a line, if a road crossing occurs at mid span, then a pole shall be placed on one side of the road so as to avoid mid span at the road crossing.
(5) While crossing another power line, the lower voltage line shall be underneath. The lower line shall normally not cross at mid span of the upper line.
(6) While placing poles on high ground, shorter poles can be used while ma
Erection of poles shall be carried out in accordance with the provisions of relevant IS.
The supports shall be suitable for the wind loads as per relevant IS. The minimum factor of safety for supports shall be as per Central Electricity Authority (Measures Relating to Safety and Electricity Supply), Regulations as and when these are notified by the Authority.
(1) All metallic supports shall be permanently and effectively earthed. The earthing arrangement shall conform to relevant IS.
(2) Metal cross arms and insulator pins for PCC and PSCC poles shall be bonded together and normally earthed at every pole for 33 kV or 22 kV or 11 kV lines and at every 5th pole for lines below 500 volts.
(3) The support on each side of a road crossing, railway crossing or river crossing shall be earthed.
(4) Normally coil earthing shall be provided except for locations involving railways, telegraph line, power line crossings and special structures where pipe/rod type earthing shall be provided. Whenever the electric lines pass close to a well or a permanently moist place, an earth should be provided in the well or the marshy place and connected to the electric line p
(1) To prevent tilting of a pole from its normal position due to abnormal wind pressure and deviation of alignment, the pole shall be kept in position by stays. The stays shall be provided at:
(a) angle locations;
(b) dead end locations;
(c) tee off points;
(d) steep gradient locations;
(e) cut - point;
(f) along the straight run at minimum two locations in 1 km.
(2) Galvanized iron stay wires and stay rods of adequate size shall be used. The individual wire used to form "stranded stay-wire" shall have a minimum tensile strength complying with relevant IS. For double pole structure, four stays along the line, two in
Guard wire shall be used where an overhead line crosses or is in proximity to any telecommunication line or any other overhead line and in populated localities. Every guard wire shall be connected to earth wherever its electrical continuity is broken. The minimum factor of safety for stay wires, guard and bearer wires shall not be less than 2.5 based on ultimate strength of the wire.
Anti climbing devices shall be provided on the supports. For this purpose barbed wire conforming to relevant IS for a vertical distance of 30 to 40 cm. at a height of 3.5 to 4 meters from ground level or clamps with protruding spikes at a height of 3 to 4 meter shall be used.
Danger Plates shall be provided on electric lines in accordance with Central Electricity Authority (Measures Relating to Safety and Electricity Supply), Regulations as and when these are notified by the Authority.
(1) Pin insulators shall generally be used on the straight stretch of a line. The pin insulators shall conform to relevant IS. The pin insulators may be used on lines up to 33 kV voltage level. The pin insulator shall consist of a single piece of porcelain mounted rigidly on a supporting structure on a pin.
(2) Shackle insulators shall be used in lines below 500 volts and these shall conform to IS. Strap type fittings shall be used for a dead end location, while U-clamp fittings shall be used at tangent locations.
(3) Requisite type of suspension and tension insulator strings with disc insulators or long rod insulators offering equivalent performance shall be used on 33 kV or 22 kV or 11 kV lines. The number of insulators and creepage distance shall be selected based on electrical system parameters taking into account altitude of site, e
Cross arms shall be provided in accordance with the requirement. In case, they are made of mild steel, the cross-arms and the clamps shall be hot dipped galvanized conforming to relevant IS, after completion of fabrication. Welding at site should be avoided as far as possible, in case welding becomes necessary, the joint shall be covered with cold galvanizing paint.
(1) The size of the conductor shall depend upon the voltage regulation, factor of safety, power to be transmitted, length of line, line voltage and mechanical strength desired.
(2) Aluminum conductor steel reinforced (ACSR) or equivalent all aluminum alloy conductors (AAAC), all aluminum conductor (AAC), aluminum alloy conductor steel reinforced (AACSR) complying with relevant IS shall be used according to requirement.
(3) Required accessories for conductor and earthwire viz. mid-span compression joints, repair sleeve, T-connector, flexible copper bond, vibration dampers, spacer/ spacer-dampers, earthwire clamps etc. shall conform to relevant IS.
(4) The configuration of conductors on the line can be triangular, horizontal or vertical depending upon the voltage level of the lines, terrain, rig
To avoid clashing and accidental mutual touching of bare overhead conductors on LT lines, spacers, which can be either spiral or composite shall be provided in between conductors at appropriate locations in different spans (particularly for lines having longer spans or lines having large sags encountering high winds).
(1) Underground cables or aerial bunched cables (ABC) of adequate rating can also be used for supplying power. Cables shall conform to relevant Indian Standards.
(2) PVC cables shall not be used in systems other than LT system.
(3) Aerial bunched cables shall be used in the theft and accident-prone areas.
(4) Direct burying of underground cables shall not be adopted except where cables enter and take off from a trench.
(5) The underground cables shall be segregated by running in separate trenches or on separate racks.
(6) The cable trenches shall be properly sloped so as to drain freely any water, which may enter.
(7) Cable trenches shall not be run through oil
(1) The service line shall be provided with insulated conductor, armoured cable or underground cable. The service line shall have adequate margin to take care of load growth for at least five years.
(2) Over head service connection shall be provided either through independent service connection or through LV box. No tapping of service line shall be permitted for supplying power to any other consumer. Feeder pillar-box shall be used for providing under ground service connection through cable to more than three or four consumers.
(3) The supplier shall provide and maintain on the consumer's premises for the consumer's use a suitable earthed terminal in an accessible position at or near the point of commencement of supply in accordance with Central Electricity Authority (Measures Relating to Safety and Electricity Supply), Regulations as an
(1) The surge arresters (SAs) shall be placed at the terminal points of the lines and also at the junction points of cables and bare overhead conductor lines.
(2) For 33 kV, 22 kV and 11 kV lines, surge arresters having rated voltage of 30 kVrms, 20 kVrms and 9 kVrms and discharge current rating of 10 kA, 7.5 kA and 5 kA, complying with relevant IS, shall be used respectively.
(3) The earthwire of appropriate size to take care of predicted/design fault currents and lightning complying with relevant IS shall be used. The earth wire shall be either of galvanized stranded steel (GSS) or alternatively ACSR/ AACSR conductor.
(4) The earthing lead for the surge arrester shall not pass through any iron or steel pipe, but shall be taken directly to a separate earth electrode.
(1) The protection scheme shall be finalized by the Owner based on prudent utility practice.
(2) An earth leakage protective device shall be provided at consumer premises as per requirement of Central Electricity Authority (Measures Relating to Safety and Electricity Supply), Regulations as and when these are notified by the Authority.
(l) Over-fluxing protection for generator (99G) To be provided for units of 500 MW and above in duplicate.
(m) Overload protection for generator (51G)
(n) Back- up impedance protection, 3 pole (21G)
(o) Overheating (winding and/ or bearing) (49G) Alarm only.
(p) Instantaneous and time delayed over current protection on high voltage side of excitation transformer (51)
(q) Generator pole slipping protection (98G)
(r) Accidental back energisation protection (50GDM)
(s) Generator circuit breaker failure protection (50ZGCB) To be provided for GCB scheme only.
Note: In
[See Regulation 12 (3)]
Design Requirements for Ash Handling System
A. Design Requirements for Ash Handling System of Pulverised Fuel Steam Generators
1. The capacity of ash handling systems, as a percentage of maximum ash generated corresponding to firing of worst coal or lignite at BMCR, shall not be less than the following:
(a) Fly ash system
(i) ESP fly ash and chimney ash : 90%
(ii) Air preheater ash : 5%
(b) Bottom ash system
(i) Furnace bottom ash : 25%
(ii) Economiser ash : 5%
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[See Regulation 33 (7)]
The minimum Load for Continuous Operation for Various Types of Hydraulic Turbines
SI. No. Type of turbine Minimum load for continuous operation (percent)
(a) Pelton or Kaplan or Bulb 30
(b) Deriaz 40
(c) Francis 50
(d) Propeller 85
[See Regulation 37 (12) (f)]
Minimum Protections to be provided for Hydro- electric Generating Units
1. Generator
SI. Protection functions Size of generating unit
No. Small (<10 MVA) Medium (10-100 MVA) Large (>100 MVA)
(a) Differential (87G) Y Y Y
(b) 95 % stator earth fault (64G1) Y Y Y
(c) 100 % stator earth fault (64G2) N Y Y
(d) Backup impedance (21G) N Y Y
(e) Voltage controlled over current (51) Y N N
(f) Negative phase sequence (46G) Y Y Y
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[See Regulation 43 (4) (c)]
Protection Details of Transmission Lines, Transformers, Reactors and Bus Bars
1. Transmission Line Protection
SI. No. Protection 765 kV 400 kV 220 kV 132 kV or 66 kV
(a) Main I- Distance protection Y Y Y Y
(b) Main II- Distance protection or directional comparison protection or phase segregated line differential protection Y Y Y/N N
(c) Directional instantaneous definite minimum time (IDMT) type earth fault relay Y Y 'Y' if both Main-I & Main-II are distance protections otherwise 'N' N
(d) Directional IDMT over current and earth fault back up protection N N 'Y' if Main-II is not provided o
(See Regulation 44)
Technical Details of HVDC Terminals/ Stations
1. System Studies- HVDC control parameters and equipment shall be designed by carrying out the following studies at different stages of the project:
(a) Main circuit parameters;
(b) Short circuit studies;
(c) Insulation co-ordination;
(d) AC and DC filter design, rating and performance;
(e) Reactive power studies, switching arrangement & logic;
(f) Temporary overvoltage;
(g) Transient overvoltage, surge arrester stress;
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