Additional Information for JCM Methodology“Installation of energy-saving conductors for transmission lines in the Bangladeshgrid”
1. Eligibility criteria
In this methodology, “The type of conductor used by the project is a family of HTLS” is set as one ofeligibility criteria. High-temperature low-sag conductors (HTLS) are defined as conductors which have lesssag at high temperatures, higher capacity and less energy loss compared to conventional aluminum
conductor steel reinforced (ACSR) cables with cores made of steel alloys, composite-reinforced metal, orcarbon fiber composite material. Examples of “a family of HTLS conductorsi” is as follows;
GTACSR = Gap-type thermal aluminum conductor steel reinforced,
ACIR = Aluminum conductor invar reinforced,
TACIR = Thermal Aluminum conductor invar reinforced,
STACIR = Super thermal Aluminum conductor invar reinforced,
ZACIR = Super aluminum conductor invar reinforced,
ACSS = Aluminum conductor steel supported,
ACCR = Aluminum conductor composite reinforced,
ACCC = Aluminum conductor composite core, andACFR = Aluminum conductor fiber reinforced

iSource: Aniket V. Kenge, Sagar V. Dusane and Joydeep Sarkar (2016) Statistical Analysis &Comparison of HTLS Conductor with Conventional ACSR Conductor
12. Conservativeness of reference emission: Conductor temperature
Conductors are used in major high voltage transmission lines in Bangladesh, being selected to meetrequired transmission load. Bangladesh has a common design requirement for steel lattice towers, on
which standard ACSR has been installed. Since such design requirement is applicable to all types oftransmission line conductors, HTLS must be designed to have same mechanical characteristics (overalldiameter, nominal weight and minimum tensile strength) as conventional ACSR used in Bangladesh,
to be able to be installed on Bangladesh standard steel lattice towers without any modification andreinforcement of steel tower members and/or tower foundation.
When calculating difference of transmission losses between reference and project scenarios inBangladesh, the only factor that needs to be considered is the resistance of the conductors themselves;
there is no need to consider the difference in reactance and admittance caused by different diameter anddistance between the conductors. This is because, as described above, the mechanical characteristics(overall diameter, nominal weight, and minimum tensile strength) are required to be the same in
Bangladesh regardless of the type of conductors.
Therefore, the transmission loss of reference conductors can be calculated as a product of transmission
loss of energy-saving conductors (which is monitored) and ratio of resistance between reference andenergy-saving conductors, as follows:

LOSSRE,L,y = LOSSPJ,L,y ×

R RE,L
R PJ,LWhere:
LOSSRF,L,y=Reference transmission loss of transmission line L in the year y [MWh/y]

LOSS PJ,L,y=Project transmission loss of transmission line L in the year y [MWh/y]R RF,L=R PJ,L=Resistance of transmission line L using currently of reference transmission
conductors. [Ω/km]
Resistance of transmission line L using project conductors. [Ω/km]

In addition, the ratio of direct current resistance between ACSR and HTLS at the same conductor
temperature (20 deg. C) is applied in this methodology. Resistance of transmission lines is positively
correlated with conductor temperature, which in turn is affected by the ambient conditions (temperature,wind velocity and solar radiation). For all type of conductors, the relationship between conductor
temperature t and direct current resistance RDC can be denoted as follows according to the standard IEC60889-1987 (Hard-drawn aluminium wire for overhead line conductors) where the constant-masstemperature coefficient is at 20 deg. C:
R DC (t) = R DC (20 deg. C) × (1 + 0.00403 × (t − 20))

2

3. Conservativeness of reference emissions: Overall diameterTo establish the reference emissions conservatively, this methodology predetermines the RDC_RF,L(direct current resistance of transmission line L using reference ACSR at 20 deg. C [Ω/km]) as aparameter fixed ex ante, by using ASTM B232 with some adjustment. The RDC_RF,L is set bydiscounting the direct current resistance of ACSR as prescribed in the ASTM B232 with 2% discount,based on the assumption as follows.
It is assumed that the diameter of each strand for reference conductor is 1% larger than its specification,
which is the maximum allowable tolerance of major international standard such as the International
Electrotechnical Commission (IEC). Since the resistance is inversely proportional to the crosssectional area, the resistance of ACSR decreases by 2% (1% larger diameter results in 2% larger crosssectional area).

If overall diameter of a conductor is 1 % smaller than that of the specification of corresponded
ASTM code (X mm), its larger cross-sectional are 2 % larger than that of ASTM code specification.
When overall diameter of corresponded ASTM code is X mm, its cross-sectional area is1
πX 2 .
41
11
X × X × π = πX 2224
When overall diameter of a conductor is 1 % larger than that of corresponded ASTM code, cross1sectional area is 4 πX 2 × 1.0201. Namely, 1% larger diameter results in 2.01% larger crosssectional area.
111(1.01X) × (1.01X) × π = πX 2 × 1.0201
224Resistance of conductor (R Ω) is in inversely proportional to its cross-sectional area. Thus, whencross-sectional area is 2.01% larger, its resistance is discounted by 1.97 %.
R×1= 0.9803R
1.0201In this methodology, this discount is set as 2 % to avoid more complicated calculation.

As a result of the discount, the RDC_RF,L values are determined as shown in Table 2 for six typical sizes(overall diameter) of ACSR conductors in Bangladesh. For instance, if the diameter of project conductor
is 28.96 mm, Code “Mallard” is selected and RDC_RF,L = 0.0702 (Ω/km at 20 deg. C) is used for
calculation of reference emissions.
In case that the overall diameter of the conductor to be used in a project does not match any of the sizes3

in the Table 1, the logic explained above can be applied for other ASTM codes to determine theappropriate RDC_RF,L for the project. In case that the overall diameter of project HTLS is not same as thatof any ASTM code, a code with the most similar and smaller overall diameter than that of project
conductor can be selected to set RDC_RF,L for the project.
Table1: Example of default reference direct current resistance values
ACSR Code which has
Overall diameter
Direct current resistance
RDC_RF,L (conservativesame overall diameter(mm)standardized in ATSM
direct current resistance)
as one of project HTLS
B232 (Ω/km at 20 deg. C)(Ω/km at 20 deg. C)ii
Flamingo
25.34
0.08560.0838Crow
26.28
0.07990.0783
Mallard28.96
0.07170.0702
Canary29.52
0.06330.0620
Cardinal
30.42
0.0596
0.0584
Bluejay
31.98
0.05110.0501ii

The 98% of direct current resistance of reference ACSR

4