Additional information for the proposed methodology“Installation of energy efficient transformers in a power distribution grid”
1. Overview of the technology applied
This proposed methodology focuses on energy efficient transformers in a power distribution grid
which have amorphous metal core. There are two sources of power loss in transformers: load losses
and no-load losses. Load losses are losses of electricity due to resistance in the electrical winding of
the transformer. These losses include eddy current loss in the primary and secondary conductors of
the transformer. These losses occur when the electricity flows through the transformer.
No-load losses are losses of electricity due to transformer core magnetizing or energizing. Theselosses occur whenever a transformer is energized and remain constant regardless of the amount ofelectricity flowing through it.
Amorphous metal core reduces the no-load losses and improves energy efficiency of transformers
with its crystal architecture. Compared with the conventional steel type (i.e. silicon steel) with aregularly arrayed structure, amorphous metal has a random arrangement of crystals. Whenamorphous metal is used for transformer core, it reduces hysteresis loss and eddy current loss andrealises energy efficiency improvement.

2. Market share of transformers in Lao PDR
Although there is no official market data of transformers installed in Lao PDR, based on theinterview with one of the world largest producers and suppliers of amorphous metal, the market oftransformers has been dominated by the transformers with silicon steel

3. Standards for load losses and no-load losses set by the power companies
The EDL who is a power company in Lao PDR has the own standard for load losses and no-loadlosses for transformer procurement. The suppliers of transformers are required to meet the standard
set by EDL. It is expected that the specification values for load losses and no-load losses are in1

decreasing trend (i.e. efficiency of the transformers are improving). The specification values are set
for different capacities and numbers of phase of the transformer. Following table 1 and table 2 are
the examples of NLL (no-load loss rate) and LL (load loss rate) for the standard set by EDL in LaoPDR.

Table 1 No-load loss rate for the transformers[Three-phase]
No-Load loss rate [W]Capacity [kVA]

Silicon steel core

Amorphous metal core

50

210

56100

340

75

160

480

95250

670

125315

750

145

400

900

165

500

1,000

2206301,200270

Table 2 Load loss rate for the transformers[Three-phase]
Load loss rate [W]Capacity [kVA]

Silicon steel core

Amorphous metal core

50

1,320

650

100

2,100

1,258

160

2,350

1,940

250

3,250

2,600

315

3,900

3,330

400

4,600

3,818

500

5,500

4,810

630

6,500

5,570

4. Blackout rate in Lao PDR
The System Average Interruption Duration Index (SAIDI) of EDL was analyzed based on available
data of 2016 and 2017. The blackout rate on yearly basis can be calculated as SAIDI divided by the
total minutes of the year. It is, however, difficult to calculate the blackout rate on monthly or daily
basis, considering that the transformers are often introduced in the midstream of the year. As shown2

in the table below, the average blackout rate is improving year by year from 2016 to 2017and it isexpected that the average blackout rate will continue to improve year by year in the future. Therefore,
selecting the worst (the highest) blackout rate during 2016 amongst all areas, which is 1.55%, wouldensure the conservativeness, and reduce the burden to identify the blackout rate for individualtransformers, considering that transformers are generally introduced in large numbers and indifferent regions.

2016No.

2017

AreaSAIDI [min]%SAIDI [min]%1North

8,142

1.55

926

0.18

2

Vientiane Capital

3,094

0.59

1,161

0.22

3South

2,872

0.55

1,976

0.38

Average

0.89 Average

30.26