Abstract: Global warming is a critical issue for modern world. Many countries try to reduce their emission by various ways. This paper analyses the benefit when using amorphous transformers in Danang city, Vietnam for energy loss reduction in electrical network and CO2 emission reduction. Thanks to the advantage of this solution, amorphous transformers are being used widely in Vietnam.
Da Nang Power Company, Ltd. (DNPC) electrical network include a large number of distribution transformers that have been operated for a long period (over 15 years) under different types and manufacturers, thus reducing the operation quality (based on IEEE C57.91-1995 standard , the normal life expectancy of distribution transformer is 20.55 years). These transformers are due to be replaced in order to ensure the safety of operation and reliability of power supply for customers. With the standard and technology in the old period, these transformers are manufactured with the high values of no-load loss, causing the increase the power losses through transformers (see “Comparison of no load loss values between old generation transformers and low loss transformers in Table 1). High no-load loss increases the energy generated by power plants causing the increase of global CO2 emission.
Amorphous distribution transformer (AMT) (Figure 1) using new technology (the core of transformer using amorphous steel instead of normal silicon steel core) significantly reduces no-load loss (to 1/5 compared to the normal transformers in old standard - see Table 1).
Table 1 – No-load losses between 3-phase standard transformers and amorphous transformers
(*) Source: Distribution Network Standard of PC3 (former EVN CPC) issued with Decision No. 1545EVN/DDL3-4 dated 7th May 2001.
(**)Source: Technical Notification No. 937/TB-DNPC dated 9th April, 2015 on the application of Amorphous Transformers.
Kyoto Protocol  on reducing global greenhouse gas emission, signed in 1997 by many developed countries, has been effective since 16th February 2005, in order to implement the solutions and mechanisms to reduce global greenhouse gas emission. With this agreement and the “Memorandum of Cooperation on Low Carbon Growth between the Japanese side and the Vietnamese side” , signed on 2nd July 2013, the Japanese Government was funding the JCM projects up to 50% of the purchasing cost of amorphous transformers used in the power networks of Vietnam. This was a valuable opportunity for DNPC to achieve the targets of power loss, reliability, network standardization and reduce green house gas emission.
Figure 1: Amorphous transformer
2. PILOT PROJECT
With the support from the government of Japan and guide of Overseas Environmental Cooperation Center (OECC), Japan, DNPC deployed the pilot project Use of low loss transformers at Danang PC in 2016 . This project was to purchase 282 AMTs for investment and overhaul sub-projects in 2016, together with replacing over-15-year of operation transformers. The other extra costs required for installing new transformers and auxiliary equipment (MCCBs, CTs, cables, withdrawing old transformers, designing, project management…) were excluded in this project. The total budget for this project was VND 57.5 bil. (~ USD 2.5 mil.).
The pilot project was kicked off in February 2016 and finished in November 2016. Benefits of the pilot project and subsequent projects are analyzed in the following parts.
3. EFFICIENCY ON POWER LOSS REDUCTION
With the use of AMTs in the investment and overhaul projects in the year 2016 – 2019 and replacing transformers with operation time over 15 years, the efficiency on power loss reduction in DNPC power network is significant. The power savings due to reduced power losses in project cycle (18 years) are 78,890,458 kWh (compared with the use of standard transformers), which are equal to VND 128.983 bil. (~ USD 5.61 mil.), respectively. Electricity loss rate of the DNPC power network reduces to 2.67% (with AMTs) in comparison with 2.77% (w/o AMTs) of the year 2019. Detailed calculation of power savings is as Table 2.
Table 2 – Energy saving when using AMTs instead of CSTs (investment period 2016-2019)
(*) Source: Statistical value of DNPC, 2020.
- Electricity loss rate of DNPC distribution network when using AMTs (year 2019): 2.67% (2.77% w/o AMTs)
- Savings due to energy loss reduction in project life cycle: 128.946 Bil. VND (~ 5.61 mil. USD)
- Project life cycle is: 18 years
- No load loss of CSTs complied with PC3 standard (Decision number 1545EVN/ĐL3-4 dated 07/5/2001).
- No load loss of AMTs complied with Notification number 937/TB-DNPC, dated 09/4/2015 of PC Danang.
- Electricity purchasing tariff for calculation of savings is 1,634.5 VND/kWh (year 2019).
4. EFFICIENCY ON ENHANCEMENT OF RELIABILITY OF POWER SUPPLY
The solution also contributes in enhancing the power supply reliability for customers by reducing the failure rate caused by old, poor quality transformers. The replaced transformers are operated for over 15 years, closing to the average life expectancy of transformer, and then the probability of fault and damage occurrence is very high. The statistic figures show that nearly 80% of Danang PC’s transformer failures are from old transformers with operating time over 10 years (Table 3). This solution contributes to decrease SAIDI (System Average Interruption Duration Index) for faults of DNPC network from 32.71 minutes (in year 2016) to 5.76 minutes (in year 2019).
Table 3 – Failure rate of distribution transformers in DNPC network from 2014 – 2016
(*) Source: DNPC statistical figures, 2014-2016. Total distribution transformers in DNPC network by the end of 2016 was 2975 units.
5. FINANCIAL EFFICIENCY
At the premature phase of AMTs, the unit price difference between AMTs and conventional standard transformers (CSTs) was about 40% higher, but this difference has been reduced dramatically to approximately 16% until now. Because of cheaper unit price and advantage in energy loss reduction and emission mitigation, AMTs become a feasible solution to gain financial targets for power utilities.
With the financial aid from Japanese Government for the pilot Joint Crediting Mechanism (JCM) project in the year 2016 (up to 50% of total transformer purchasing price, excluding the consulting fee of 5%), DNPC saved a total amount of VND 25.8 million (~ USD 1.13 million). The detailed summary of pilot JCM project’s financial efficiency is as Table 4.
Table 4 – Summary of pilot JCM project’s financial efficiency
After the completion of the pilot project, AMTs have been used till now without any financial aids because of their benefit on financial aspect. The payback periods of all projects are within 8 to 10 years. The total cost for purchasing AMTs from 2016 to 2019 is approx. VND 191 billion (~ USD 8.3 million).
6. SOCIAL AND ENVIRONMENTAL BENEFITS
With the use of AMTs since the year 2016, DNPC has contributed to reducing the global warming and climate change due to CO2 emission reduction, therefore limiting the negative impacts of global climate change on Vietnamese people’s lives and on all humanity. The data in Table 5 shows that the CO2 emission reduction volume in the project period is 1,301 tCO2/year.
Table 5 – Emission reduction calculation
In this paper, the benefits of using AMTs instead of CSTs are analyzed, regarding technical, financial, social and environmental aspects. The use of AMTs instead of CSTs in Danang power network is timely and necessary to achieve DNPC strategic objectives. Not only helping the company to achieve the strategic objectives, it also benefits the company, customers and global environment in combating global climate change.
With the advantages of AMTs, they are used widely now in Vietnam power distribution network for energy loss reduction and CO2 emission elimination.
 IEEE Standards Board, IEEE Std C57.91-1995 - IEEE Guide for Loading Mineral-Oil Immersed Transformers, 1995.
 United Nations, Kyoto Protocol to the United Nations Framework Convention on Climate Change, 1997.
 Minister of Economy, Trade and Industry of Japan and Minister of Natural Resources and Environment of the Social Republic of Vietnam, Memorandum of Cooperation on Low Carbon Growth between the Japanese side and the Vietnamese side, 2nd July 2013.
 DNPC, Proposal report – Project: Use of low loss transformers at Danang PC in 2016, 2015.
||Le Van Phu received his Engineer degree in Electrical Engineering from the Danang University of Technology in 1995 and his M.E. in Electrical Power System Management from the Asian Institute of Technology in 2004. He has worked for Danang Power Company, Ltd. since 1995. He is now working as Deputy Head in charge of the Technical Division, Danang Power Company, Ltd. His research interests are in the fields of power distribution network management, energy efficiency, and renewable energy.
Le Van Phu, M.E.
Danang Power Company, Ltd.