ECBC Transformers Guidelines

Aiming to stop wasteful use of energy and bridge the power demand-supply gap, the Government of India enacted the Energy Conservation Act(EC Act) and established Bureau of Energy Efficiency under Ministry of Power. One of the important provisions of the EC Act relates to the enforcement of Energy Conservation Building Codes for efficient use of energy and its conservation in the buildings or building complexes.

As defined in the EC Act, “Energy Conservation Building Codes” (ECBC) means the norms and standards of energy consumption expressed in terms of per square metre of the area where the energy is used and includes the location of the building.

The EC Act mandates the ECBC for buildings with a connected load of 500 kW or contract demand of 600 kVA and above and are intended to be used for the commercial purposes and are constructed after the rules relating to ECBC have been notified by the States Governments under section 15 (a).

Features of ECBC

The ECBC will set minimum energy efficiency standards for design and construction of a nonresidential building. Energy performance standards for the following building systems are included in the ECBC

•       Building Envelope.

•       Lighting.

•       Heating Ventilation and Air Conditioning.

•       Service Water Heating.

•       Electric Power and Distribution.

However, the broad requirements of the Code with respect to the building envelope are the same for new buildings as well as for extensions and modifications.

All over the world, ECBCs have a proven track record of significantly reducing energy use in buildings in a highly cost effective way. The ECBC benefit both individual building owners and the people and government at large. Benefit to property owners include reduced energy costs and improved comfort (both thermal and visual). The benefits to society include the following:

•       Reduced capital investments in energy supply infrastructure.

•       Reduced environmental impacts.

•       Improved electricity reliability.

•       More efficient use of resource (It is cheaper to save energy than it is to build new power plants).

It is estimated that buildings that are ECBC compliant have a potential of savings to the tune of about 30%-35%.

Road Map to make ECBC Mandatory

Given the fact that the capacity in the country required to effectively implement this code is inadequate, the implementation of the codes will be on voluntary basis initially. Incentives to promote its use in the voluntary phase will be provided. Only when there is sufficient availability of both technical expertise and complaint material, will the codes be made mandatory. The Government will launch an effective awareness campaign to promote ECBC all over the country

Compliance Requirements

All the buildings or building complexes with a connected load of 500 kW or greater or a contract demand of 600 kVA or greater^* have to comply with the Code. Buildings with 1,000 m² or more of conditioned area are likely to fall under the above load conditions. The following sections which deal with mandatory and prescriptive requirements of new and existing buildings are related to this specified threshold area. It is important to mention here that these mandatory and prescriptive requirements are applicable only where the building has a connected load of 500 kW or more or contract demand of 600 kVA or more..

The Code is presently under voluntary adoption in the country.

This Code would become mandatory as and when it is notified by the Central and State government in the official Gazette under clause (p) of §14 or clause (a) of §15 of the Energy Conservation Act 2001 (52 of

2001)

Basics of Transformers

Transformer is a static device, which is used to either increase (Step up) or decrease (Step down) the input supply voltage depending on the application and requirement. Transformers consist of two or more coils that are electrically insulated, but magnetically linked (see Figure 8.1). The primary coil connected to the power source and secondary coil connects to the load.

Power transmitted from power plants, is in the form of high-tension voltage (400 kV - 33 kV). The reasons for transmitting HT voltage are:

•     Reduced conductor size and investment on conductors

•     Reduced the transmission losses and voltage drop.

At the user end, equipment with various voltage rating is used for different applications. Hence, the transmitted voltage is first stepped down (11 kV - 230V) through distribution transformers and then the power supply is distributed to the various sections and equipment. Distribution transformers are used normally in all commercial buildings. They are kept energized around the clock providing power to the building’s electrical equipment.

8.2.1.1  Maximum Allowable Power Transformer Losses

Transformers are of two types - Dry type and Oil filled. Fire safety and environmental concerns associated with transformers are important. There is a misconception that oil filled transformers are not installed at fire hazardous places. It all depends on the Thermal Capacity and Ignition temperature of the insulating materials used. If the thermal capacity of the oil used is higher than the insulating materials used in the Dry type transformers then they are more hazardous as compared to oil filled transformers.

Distribution transformers consume energy even when the building is not occupied or its equipment are not operating, resulting in energy loss.

Transformers losses are discussed in Box 8-A.

The efficiency of transformers normally varies anywhere between 96 to 99 percent.The efficiency not only depends on the design, but also, on the effective operating load. Transformer losses consist of two parts: No-load Loss and Load Loss

No-load Loss (also called core loss) is the power consumed to sustain the magnetic field in the transformer's steel core. Core loss occurs whenever the transformer is energized; and it does not vary with load. Core losses are caused by two factors: hysteresis and eddy current losses. Hysteresis loss is that energy loss caused by reversing of the magnetic field in the core as the magnetizing alternating current rises and falls and reverses direction. Eddy current loss is a result of induced currents circulating in the core.

Load Loss (also called copper loss) is associated with full-load current flow in the transformer windings.

Copper loss is power lost in the primary and secondary windings of a transformer due to the ohmic resistance of the windings. Copper loss varies with the square of the load current. (P=I²R).

Transformer losses as a percentage of load is given in the Figure 8.2.

                                                                                                                                                        

 For a given transformer, the manufacturer can supply values for no-load loss, P_No-load, and load loss, P_Load. The total transformer loss, P_Total, at any load level can then be calculated from:

P_Total = P_No-load+ (% Load/100)² × P_Load

Source: Energy Efficiency in Electrical Utilities, Bureau of Energy Efficiency, 2005.

As per the Code:

Power transformers of the proper ratings and design must be selected to satisfy the minimum acceptable efficiency at 50% and full load rating. In addition, the transformer must be selected such that it minimizes the total of its initial cost in addition to the present value of the cost of its total lost energy while serving its estimated loads during its respective life span.

ECBC lists various transformer sizes of dry-type and oil-filled transformers and their associated losses at 50% and full load rating 

(Table 8.1 and Table 8.2 of ECBC).

Total loss value given in the above table are applicable for thermal classes E,B and F and have component of load loss at refrence.
Temperature according to clause 17 of  IS 2026:Part 11 i.e, average winding temperature rise as given in coloumn 2 of Table 8.2 Plus.
30°C. An increase of 7% on total for thermal class H is allowed.

Total loss value given in the above table are applicable for tharmal classes E,B and F and have component of load loss at refrence.
Temperature according to clause 17 of  IS 2026:Part 11 i.e, average winding temperature rise as given in coloumn 2 of Table 8.2 Plus.
30°C. An increase of 7% on total for thermal class H is allowed.

CALCULATIONS DEPICTING THE PAYBACK PERIOD:

Return On Investment (ROI) for Transformer Of 1500KVA with 100% Loading.

From above it can be concluded that we can approx. Rs. 3.25Lac on our electricity bill and additional cost price paid by us shall be returnable after 18Months, this is will be a huge saving on the electricity bills.
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