What Is an Energy Efficient Transformer?

Power transformers have been invented in 1881 for more than a century. At present, in most cases, the voltage level of electrical energy from the power station to the user must pass at least a 5-level transformer before it can be transmitted to low-voltage electrical equipment (380V / 220V). Although the transformer itself is very efficient, the total loss is still very large due to its large number and large capacity. It is estimated that the total loss of transformers in China accounts for about 10% of the system's power generation. For each 1% reduction in losses, tens of billions of kilowatt-hours of electricity can be saved each year. Therefore, reducing transformer losses is an imperative energy-saving measure.

Energy-saving transformer

No-load loss in transformer losses, ie

From the perspective of some new energy power generation industries in China, the development trend of energy-saving transformers is very clear.

In 1979, the Massachusetts Institute of Technology used 2605SC to make a 15kVA dry-type transformer. In July 1981, Japan used 2605S2 to trial-manufacture a 10kVA transformer, and in August 1982, it trial-produced a 30kVA high-voltage oil-immersed transformer. In February 1983, it also trial-produced a 35kVA three-phase five-pillar model transformer as a research object. In the early 1980s, China conducted research on amorphous alloy transformers, and in 1986 developed a 30kVA amorphous iron core transformer by the Shanghai Transformer Factory. In the 1990s, the research and development of amorphous iron core transformers has entered the practical stage. Several domestic manufacturers have successively introduced foreign technologies to produce larger capacity amorphous iron core transformers.

Calculation formula of energy-saving transformer

(1) Active power loss: P = P0 + KT2PK (1)

(2) Reactive power loss: Q = Q0 + KT2QK (2)

(3) Comprehensive power loss: PZ = P + KQQ (3)

Q0I0% SN, QKUK% SN

In the formula: Q0No-load reactive power loss (kvar)

P0No-load loss (kW)

PKrated load loss (kW)

SNrated transformer capacity (kVA)

I0% % of transformer no-load current.

UK%-short circuit voltage percentage

average load factor

KTload fluctuation loss coefficient

QK rated load magnetic leakage power (kvar)

KQreactive economic equivalent (kW / kvar)

Calculation conditions

(1) Take KT = 1.05;

(2) Transformer capacity SN = 800kVA connection group is Y · yno;

(3) When the minimum load of the 6kV 10kV step-down transformer of the urban power grid and industrial power grid is taken, the reactive power KQ = 0. 1kW / kvar;

(4) The average load factor of the transformer can be = 20% for agricultural transformers; for industrial enterprises, three shifts can be used, = 75%, which is calculated in the following two cases;

(5) The price of transformer (800kVA) is S7 = 76000 yuan, S9 = 91,000 yuan, and SH12 = 118300 yuan;

(6) Transformer operating hours T = 8760h, maximum load loss hours: t = 5500h;

(7) Electricity fee is RMB 0.60 / kWh for comprehensive electricity fee (not calculated according to two electricity prices);

(8) No-load loss P0, load loss PK, I0%, UK% of the transformer are shown in Table 2.

Calculation example

According to the calculation formula and calculation conditions, according to the analysis of = 20% and = 75%, the calculation process and results are shown in Table 3.

Payback period of investment spread

There are generally two calculation methods for the payback period of investment spreads:

(1) Static investment payback period: irrespective of the time value of money of the investment, the calculation formula: =;

(2) Dynamic investment payback period: Considering the time value of money in the investment, the current investment and future returns are discounted to the present value at the discount rate of the funds. The calculation of this method is complicated. It involves the inflation rate, the interest rate of funds and banks, and the discount rate. Therefore, there are many uncertain factors. It is recommended not to use this method, and it is advisable to use a static investment payback period.

SH12 with SN = 800kVA has more investment than S7:

CS7 = 11830076000 = 42300 yuan

SH12 invests more than S9:

CS9 = 11830091000 = 27300 yuan

At = 20%, the payback period for multiple investments is:

TS7 === 4.49 (year)

TS9 === 3.79 (year)

At = 75%, the payback period of multiple investments is:

T'S7 === 2.59 (year)

T'S9 === 3.99 (year)

The SH12 of other capacities is more than S7 and S9 in terms of investment payback years. The above calculation methods and steps can be used.

Transformer energy saving is a higher requirement based on product quality requirements and safe and reliable performance. This will bring additional cost investment such as design and manufacturing to meet users' needs to reduce more energy losses. Therefore, this not only requires the concept of life-cycle management as the premise to calculate the long-term economic benefits of investment and recovery, but also needs to establish an effective mechanism for market and policy support such as fair competition, effective supervision and management, and energy-saving fiscal and tax benefits.

At present, the competition in the distribution transformer industry is fierce. In the face of the pressure of high raw material costs, and the lack of energy conservation assessment system construction and market supervision and management, the relatively high initial investment in the selection of energy-saving transformers has caused certain difficulties in the promotion of energy-saving transformers. .

(1) Cost pressure of transformer raw materials

The high price of transformer raw materials, including silicon steel sheets, copper and other materials, is the main difficulty and problem facing the development of energy-saving transformers. The reduction of transformer loss mainly comes from the reduction of no-load loss and the reduction of load loss of transformer windings driven by the advancement of cold-rolled oriented silicon steel sheet technology. Due to the expansion of Baosteel's production capacity and technological level in the past two years, together with Wuhan Iron and Steel, it has gradually met the domestic market requirements for cold-rolled oriented silicon steel sheets, so the market price of silicon steel sheets will gradually stabilize. "For the electromagnetic wire, there is no more economical technological innovation based on material properties." This makes transformer manufacturers and electromagnetic wire supply companies difficult to control costs in the high copper price and sharp price fluctuations. The profit margin of the enterprise is reduced, and the willingness to further reduce the load loss is reduced.

China is a copper-deficient country, and refined copper is mainly imported. Copper prices are affected by international supply and demand and international hot money. In the face of such an environment and resource demand, it is even more important to consider the impact of copper resource utilization on the industry and analyze the reasonable application range that promotes the maximization of socio-economic value.

Resources can be solidified into social wealth and also a sustainable driving force for economic development. For the use of metal materials with certain financial attributes, it should analyze its long-term resource utilization value and the value of the equipment used, adjust foreign exchange use and investment policies, and pay attention to the recycling and recycling of recyclable resources that make full use of existing equipment. Utilize and adjust the energy-consuming industrial structure, make full use of foreign resources, improve domestic resource utilization efficiency and promote the development of circular economy, and bring into play the long-term economic value of resource utilization.

(2) Lack of life-cycle management of transformers

Many power users have not established active asset life-cycle cost management, environmental impact assessment and lack of effective assessment and energy service personnel. Among the distribution transformers, the purchaser has insufficient knowledge of the economic operation and comprehensive cost evaluation of energy-saving transformers, or can only consider short-term investment costs, and has to ignore long-term operation and maintenance costs with limited funds.

(3) Policies and regulations need more detailed implementation and effective supervision. Due to the manufacturing characteristics of transformers, it is difficult for users to determine whether the quality, performance and calibrated loss levels of newly purchased transformers truly meet the standards. Coupled with the lack of energy measurement in operation management, it is impossible to assess the actual operation loss and propose more effective economic operation and management measures.

At present, grid users are actively seeking ways to adopt sampling and temporary inspection methods to ensure that newly purchased transformers meet the requirements of safe operation and actual losses, and prevent the inflow of fake and shoddy products.

(4) Strengthen the coordination of energy-saving information communication and policy standards. Development of energy-saving transformer policies and technical information includes all aspects of transformer design, production, procurement, operation, service, and financing. Therefore, strengthening information exchange throughout the supply chain is beneficial to the upstream. Grasping downstream needs and strengthening technological upgrades will also help users understand the overall cost of the burden and actively seek good projects for energy-saving investment to maximize the economic benefits of energy-saving procurement and transformation.

On the other hand, due to the differences between the current product standards and the national energy efficiency standards for loss requirements, which are described in individual clauses, users have also questioned the loss indicators. At present, in the revision of the energy efficiency standards for distribution transformers, the requirements of various national standards and other standards for various indicators will be better coordinated, and they will promote each other to facilitate the development of overall industry technology.

(5) Evaluation of transformer energy saving benefits and lack of financing services

In non-power-supply companies, the amount of energy saved by a transformer is also related to the way electricity is charged. In the promotion of energy-saving transformers, the situation that may cause energy saving but not save money when calculating the basic electricity cost according to the transformer capacity will not be conducive to the selection of energy-saving transformers, and will not play its due role.

In the energy-saving transformation of some old transformers, due to the lack of transformation funds and a long investment recovery period, without the support of preferential policies, energy-saving transformation of enterprise transformers will be difficult.

At present, although there are many financing services, such as contract energy management models, transformer CDM or PCDM projects, rarely provide services for transformer transformation of small and medium-sized enterprises. Although there are certain difficulties in financing services, with the deepening of government departments' ability to save energy, energy-saving transformers may enter the Huimin Project and enjoy preferential tax policies in the future, which will further promote energy-saving transformers.

In the "Interim Provisions on the Feasibility Study of Energy-Saving Capital Construction Projects" promulgated and implemented by the State Planning Commission in 1983, it was pointed out that the calculation period of investment recovery should generally not exceed 5 years, and the longest should not exceed 7 years. And energy efficiency policies.

Based on the above calculation results, the following conclusions can be drawn:

(1) Compared with S7 and S9, the investment of SH12 is recovered within the period specified in the policy. Therefore, the current promotion and application of SH12 is in line with the national policy of energy conservation;

(2) In rural areas, the average load factor is 15% to 20%. SH12 has a slightly longer payback period than S7, but it has a shorter payback period than S9. This means that the SH12 and S9 investments are weighed in rural areas. And energy saving benefits, the decision to promote and apply SH12 instead of S9 should be made;

(3) In industrial and mining enterprises, the three shift system is implemented, and the load rate is generally 50% to 80%. The payback period of SH12 multi-investment is shorter than that in rural areas, and the investment benefit is more significant;

(4) Widely promote the application of amorphous alloy iron core transformers, whether in rural areas in rural areas, or in factories and mines, especially in new power distribution room substations, SH12 should be used, such as a one-time investment in place , To avoid short-term repeated investment.