Some important Safety Rules from I.E.1956

A) Rule:60 Where supply line for use at low medium voltage has been disconnected from a system for the purpose of repair, line shall not be reconnected to the system until the supplier or the owner has applied the test prescribed (such as I.R and HV test.)
B) Neutral conductors of 3 phase, 4 wire system and the middle conductor of a 2 phase, 3 wire system shall be earthed by not less than two separate and distinct connections with a minimum of two different earth electrodes or such large number as may be necessary to bring the earth resistance to a satisfactory value both at the generating station and at the sub station. The earth electrodes so provided may be inter connected to reduce earth resistance. It may also be earthed at one or more points along the distribution system or service line in addition to any connection with earth which may be at the consumer’s premises.
C) In the case of system comprising electric supply lines having concentric cables, the external conductors shall be the one to be connected with earth.

D) Where a supplier proposes to connect with earth an existing system for use at high or extra high voltage which has not higher to been so connected with earth, he shall give not less than fourteen days notice in writing together with particulars to the telegraphic authority of the proposed connection with earth.

E) Where the earthling load and earth connection are used only in connection with earthling guards erected under high or extra high voltage overhead lines where they cross a telecommunication line or a railway line and where such lines are equipped with earth leakage relays of type and setting approved by the Inspector the resistance shall not exceed 25 Ohms.

F) If so far as the provisions of rule 61 are consistent with the provisions of this rules, all connections with earth shall also comply with the provisions of that rule.

Rule 69 Pole type sub stations:- Where platform type construction is used for a pole type sub station and sufficient space for a person to stand on the platform is provided, substantial hand rail shall be built around the said platform and if the hand rail, is of metal. It shall be connected with earth.

Provided that in the case of pole type sub station on wooden support and wooden platform the metal hand rail shall not be connected with earth.

Rule 74:- Material and strength :- (1) All conductors of overhead lines other than those specified in sub rule (1) of rule 86 shall have a breaking strength of not less than 317. 51 Kg (700 1bs)

3) Where the voltage is low and the span is of less than 15.24 meters and is on the owner’s consumer’s premises a conductors having an actual breaking strength of not less than 136.08 Kg (300 1bs) shall be used.

Rule- Clearance above ground of the lowest conductor:-

1) No conductor of an overhead line, including service lines, erected across a street shall at any part thereof be at a height less than

a) for low and medium voltage lines 5.791 meters.
b) for high voltage lines 6.096 meters


2) No conductor of an overhead line, including service lines erected along any street shall at any part thereof be at a height less than.

a) for low and medium voltage lines 5.485 meters
b) for high voltage lines 5.791 meters

3) No conductor of an overhead line including service lines erected elsewhere than along or across any street shall be at a height less than.

a) for low, medium and high voltage lines upto and including 11,000 volts, if bare 4.572 meters.

b) for low, medium and high voltage lines upto and including 11,000 volts, if insulated 3.963 meters.

c) for high voltage lines above 11,000 volts 5.182 meters.

4) for extra high voltage lines the clearance above ground shall not be less than 5.2 meters plus 0.305 meters for every 33,000 volts or part thereof by which the voltage of the line exceeds 33,000 volts.

Provide that the minimum clearance along or across any street shall not be less than 6.1 meters.

Rule: 78: Clearance between conductors and trolley wires

Rule: 79. clearance from building of low and medium voltage line and services lines.
1) Where a low or medium voltage overhead line passes above or adjacent to or terminates near any building, the following minimum clearance from any accessible point on the basis of maximum sag shall be observed.

2) for any flat roof, open balcony, verandah roof and loan to roof.

Standard

i) When the line passes the building a vertical clearance of 2.439 meters from the nearest point and

ii) when the line passes adjacent to the building a horizontal clearance of 1.219 meters from the nearest point and

iii) for pitched roof:-

i) when the line passes above the building a vertical clearance of 2.439 meters immediately under the line and

ii) when the line passes adjacent to the building horizontal clearance of 1.219 meters.

2) Any conductor so situated as to have a clearance less than that specified in sub rule shall be adequately insulated and shall be attached by means of metal clips at suitable intervals to a bare earthed bearer wire having a breaking strength of not less than 317.51 kg.

3) The horizontal clearance shall be measured when the line is at maximum deflection from the vertical due to wind pressure.

Rule 80: Clearance from building of high and extra high voltage lines:-

1) Where a high extra – high voltage overhead line passes above or adjacent to any building or part of a building it shall have on basis of maximum sag a vertical clearance above the highest part of the building immediately under such line or not less than:-

a) for high voltage lines upto and including 33,000 volts 3.658 meters.

b) for extra high voltage line 3.600 meters plus 0.305 meters for every additional 33,000 volts or part thereof.

2) The horizontal clearance between the nearest conductor and, any part of such building shall on the basis of maximum deflection due to wind pressure, be not less than:-

a) for high volt age lines above 11,000 volts. and up to and including 33,000 volts 1.829 meters.

b) for high voltage, lines upto and including 11,000 volts 1.219 meters

c) for extra high voltage line 1.829 meters plus 0.305 meters for every additional 33,000 volts or part thereof.

Rule 81: Conductors at different voltage on same supports- where conductors forming parts of systems at different voltage are erected on the same supports, the owner shall make

standard
adequate provisions to guard against danger to lineman and other from the lower voltage system being charged above its normal working voltage by leakage from or contact with the higher voltage system and the methods of construction and the clearance between the conductress of the two systems shall be subject to the prior approval of the inspector.

Rule 88: Guarding:-
1) Where guarding is required under these rules the provision of sub rule (2) to (4) shall apply.

2) Every guard wire shall be connected with earth at each point at which its electrical continuity is broken.

3) Every guard wire shall have an actual breaking strength of no less then 635 kg and if made of iron or steel shall be galvanized.

Construction of 33KV substation

IE rule permits following limits of service voltage :-


LV........................ -6 to +6 %


Upto 33 KV......... -9 to +6 %


Above 33 KV....... -12.5 to +10 %


132 KV transformers have on load tap changers with -15 % to +5 % tap range. Tap changing is not provided in 33 KV distribution transformers.


Protection Scheme:-


132 KV:- Busbars ( Not protected ), Transformers ( Biased diff. with harmonic restraint for HV/LV windings, Inst. REF for LV windings, Overfluxing , IDMT OC and EF for backup,Buccholz, WT, OT), Feeders ( Dist with accelerated zone2, PLCC backup IDMT OC and EF).


33 KV:- Busbars (Not protected), Transformers 7.5 and 12.5MVA ( Biased diff., Inst REF, IDMT OC and EF), Feeders(IDMT OC and EF).

Then the system layout is designed in which ring main ( main and transfer bus) is decided for HV and LV side of 132 KV substation and single bus open ring for 33KV and double bus on 11 KV side ( indoor switchgear ) is decided for 33 KV substation. 11 KV line is erected on 9m PCC poles.

Service connection of 132 KV is given for 5MVA+ consumers. For 1.5 to 5 MVA consumers, 33 KV and for upto 1.5 MVA, 11 KV connection is given.

Fault level:- 11 KV:- S.C.Current ( 18KA), S.C.MVA ( 350MVA), 33 KV:- S.C.Current (18KA), S.C.MVA (1000MVA), 132 KV:- S.C.Current ( 32 KV ) , S.C. MVA ( 7200 MVA)

The transformer rating on 132/33 KV are 12.5, 20 and 25 MVA , on 132/11 KV are 6, 10, 12.5, 31.5 MVA and on 33/11 KV are 0.63, 1.6, 3.15, and 5 MVA .

The switchgear ratings for 132 KV are 1250 A or 2000 A with S.C. current rating of 12.5 KA to 31.5 KA ( i.e. rupturing capacity 2500 MVA to 7200 MVA). For 33 KV side, CBs are of rating 630 A to 1250 A with S.C. current rating of 12.5 KA to 18 KA.( i.e. rupuring capacity of 660 MVA and 750 MVA). 11 KV CBs are rated 400, 800 and 1250 A with rupturing capacity 250 MVA and 500 MVA.

The distribution transformers are of 500 KVA ( urban) and 40 KVA ( rural).

For conductors and cables, 125 sq.mm ACSR or 300 sq.mm XLPE cable is used for 33 KV. For 11 KV, 80 sq.mm. ACSR or 185 sq.mm XLPE cable is used. 50 sq.mm ACSR or 3 1/2 core PVC cable of 70 to 300 sq.mm is used on 415 V side.

Indian Power Sector buzzing with activities

• India has a large generation capacity . (4 % of the world capacity). Not bad, isn't it ? But thanks to our teeming billions, this is really little. Our per capita consumption is not even 1000 KWH/year. World average is close to 3000 KWH/year.
• Transmission scenario is even more worrysome than generation. Only 13 % of the generated power can be transmitted at present. Plan is to increase this to 20% by 2012.
• Tough time ahead for Chinese suppliers? With majority of orders in recent past going to China, govt has proposed 10% import duty, just to bail out BHEL. But one govt body is protesting this import duty. Guess whom? Competition Commision of India ( CCI) ! Here the catch is India can't survive without China as Indian power equipment suppliers dont have the capacity to serve massive orders coming for UMPPs.
• So, its official now. Govt alone cant take ahead nuke power projects. But being a sensitive issue, we now hear what is termed as "minor" private partnership in nuke power sector.
• The new baseline for CO2 emmission has come. CEA has declared it as 0.82 t CO2 / MWh.
• One of our neighbours has realised that they depend upon us for power sector growth. Yes, its the Bangladesh.We are poised to hear more Indo-Bangla power transmission agreements.
• This five year plan could add only 62000 MW against the target of 78000 MW. But current year was super duper hit. Compared to not even 10,000 MW added in each of the last 3 years, this year added good 22,000 MW.
• Despite above, 57 % of our rural houses and 12 % of urban houses are dark. Reason? I think its coal shortage. 75 of our power plants run on coal which consume most of 400 mT produced by CIL. What about gas? Well, picture is even more grim there. Only 144 mscmd is produced in India. So, coal is, and will remain king fuel in Indian power sector.

What's hot in Indian power sector?

• Power trading is "ON" in India. Companies such as Jindal Power and states like Chhattisgar, J&K and MP have sold power on short term basis through the grid.
• India is the 6th largest consumer of power. That is roughly 4 % of global consumption.
• Solar India is shining bright:- Karnataka Power Corp. has set up 3 MW solar power plant. This is just the begining.
• Private power players have cropped up in Hydel sector. KSK of Karnataka has bagged 2000MW contract from Arunachal govt., ousting....guess? ( NHPC !!)
• What happens in multibillion dollar procurements in Indian power sector ? NTPC's bulk order of boilers is yet to be finalised as L&T was decalred invalid in round#1. NTPC plans to add 32000 MW in 12th plan.
• Chinese power sector manufacturers have hit the first road block as Power Grid has put up a condition that they must have set up manufacturing facility in India !
• Guess which neighbor of India is being helped this time? Its Afghanista ! Their engineers first batch completed Transformer training in Ahmedabad.
• How much Indian metros consume? A back of envelop calculation goes like this:- Assuming 7 metros like Delhi ( @ 5000MW each) , our metros only need 35000 MW power. Imagine how much is left for rest of the country !
• Boom boom time. Thats it for power sector in India. You know who is coming up with mega projects? Reliance,Aditya Birla and Hirananadanis. Jobseekers, be ready !
• Many a slip between the cup and the lip. Dismal Indian nuke power generation plan is again in limbo after initial hopes generated after Indo-US civil nuke deal. This time Ministry of Environment has returned 4 new proposals of NPCIL.

Power Sector Snippets

• Large hydro potential is available in India. ( In north and north-east of the country). 25 GW is already used, 20 GW is under implementation and further 66 GW is still available.



• Purnea and Gorakhpur are Indias biggest FACTS projects.



• HTSC ( High Temperature Super Conduction) is stioll to come to India.


• At present only 3 % of the total volume of electricity handled by grid ( = 15000 GWh) is traded in India. Power trading is growing @ 6 % per annum.


• Power trading improves capacity utilisation, reduces unit costs, raises farm and industrial output and cuts down need for new projects.

Some issues in Indian power sector

• Generation Capacity addition during last 2 years has been far below the targets. Target for 2007 -08 was 16,000 MW , actual aws only 9,000MW. Target for 2008-09 was 11,000 MW , actual was 3,000 MW. We are slipping in the year 2009-10 also. Anybody held responsible?
• T&D revenue losses are increasing unabated. The loss is huge. Every year Rs.50,000 crore are lost in T&D.
• Untapped potential in Small Hydropwer is 80%. Most of this is in North-east.
• Gas based power plants operate on best PLF. India has adequate gas reserves, yet the contribution of Gas based plants in total generating capacity is only 10 %

Some plans for Indian Power Sector

• Inter-reginal power capacity planned for the national grid:- 40,000 MW by 2012.
• Performance of Electricity ( as one of the six infrastructure industries) this year(2009-10):-expansion of 6.5 %.
• Part of total cost of power distribution projects towards cables:- 10 %
• Gas based power plants capacity plannedin XII plan :- 10,000 MW.
• Investment outlay for Generation in XII plan:- Rs 500,000 Crore
• Size of Indian Transformer Industry :- Rs 12,000 Crore.
• Investment required during XIth plan in power sector :- Rs. 10 Billion ( Rs. 1000,000 Crore)

Power and India

• Present installed generating capacity is 1,30,000MW.
• Plan to add generating capacity of 60,000 MW during 2007-2012.
• Projected investment in power generation:- USD 70 billion.
• Projected inestment in power transmission and distribution :- USD 60 billion.
• India is growing consistently @ 7%.
• In 90s India's exports were of USD 20 billion , today they are of USD 100 billion.
  India has forex reserves of USD 150 billion.

Huge manpower required in Indian Power sector

To sustain 9% GDP growth rate, India needs to add more power generation capacity in the next 10 years than it did in last 50 years.
This means an investment of $300 billion in next 5 years alone and planning commission has estimated a requirement of 5 lakh additional skilled professional by 2017 .