How Can I Reduce Losses in Distribution Transformer?

Jens Pan

By Jens Pan

Hi, this is Jens. I am an engineer with ten years of experience in transformer design. I have worked in Daelim, a manufacturer with more than 16 years of experience in the production and design of distribution transformers, for 7 years. In this article, I will introduce to you seven ways to reduce the Losses in distribution transformers.

If you think this article is beneficial to you, please share it with more people.

If you need to purchase a distribution transformer, please contact Daelim.

Daelim has a number of transformer design patents, and their products have been successfully applied in Canada, the United States, Russia, Germany, and other countries.

Table of Contents

Method 1: Choose the capacity of the distribution transformer reasonably

The basic principles of correct and reasonable selection of the capacity of distribution transformers:

The power Losses of the distribution transformer itself is minimal;

The distribution transformer has a higher utilization rate;

The capacity of the distribution transformer is adapted to the low-voltage power supply range.

Mainly consider the following points:

  •  The rated capacity of the distribution transformer should be able to meet the needs of all electrical loads, and the transformer should not be operated under long-term overload.
  • The transformer capacity should not be too large or too small. For power distribution rooms with two or more transformers, it should be considered that when one of the transformers fails, the capacity of the remaining transformers can meet the requirements of all the loads of Category I and II.
  • The daily load of the transformer should be greater than 60% of the rated capacity of the transformer.

Method 2: Use energy-saving distribution transformers as much as possible

At present, more distribution transformers use products of the S9 series and above.

The no-load Losses of the S9 series is 8% lower than that of the S7 series, and the load Losses is reduced by 24% on average.

The no-load Losses of the S11 series is about 20% lower than that of the S9 series.

In addition, amorphous alloy iron core transformers have the effect of reducing Losses and energy saving.

The no-load Losses of amorphous alloy iron core transformers is reduced by 70% to 80% on average compared with S9 series products.

Its load Losses is equal to that of S9 series transformers.

It is the development of distribution transformers. direction.

Method 3: Install reactive power compensation equipment appropriately

In the distribution network, the day and night load changes greatly, and the late-night distribution transformer is basically in a light-load or no-load state.

In order to effectively compensate the reactive power of the transformer itself and avoid overcompensation at light load or no-load, resulting in reactive power reverse transmission.

Follow-up compensation is generally carried out for distribution transformers with a capacity below 100kVA at about 5% of the capacity.

For distribution transformers with a capacity above 100kVA, 7% to 10% of the capacity is used, and automatic switching is used.

Method 3: Install reactive power compensation equipment appropriately

In the distribution network, the day and night load changes greatly, and the late-night distribution transformer is basically in a light-load or no-load state.

In order to effectively compensate the reactive power of the transformer itself and avoid overcompensation at light load or no-load, resulting in reactive power reverse transmission.

Follow-up compensation is generally carried out for distribution transformers with a capacity below 100kVA at about 5% of the capacity.

For distribution transformers with a capacity above 100kVA, 7% to 10% of the capacity is used, and automatic switching is used.

Method 4: Choose the appropriate installation location of the distribution transformer

  • Under the condition of ensuring that the power supply radius does not exceed 500m, try to be as close to the load center as possible.
  • The distribution transformer is fully utilized. That is to say, it is better for one distribution transformer to carry several types of loads of different natures, and use the difference in the power consumption time of various loads to increase the load rate of the distribution transformer.

However, special transformers for drainage and pumping wells are not allowed to be connected to other loads.

So that they can be stopped during non-use seasons to reduce the no-load Losses of distribution transformers.

Distribution transformer installation

Method 5: Adjust the tap of the distribution transformer in time

The total Losses of the distribution transformer is: P∑=Pk+Po=(P2+Q2)/U2R+(U/U1 )∑P’o

Where: Pk—short-circuit Losses of the transformer, kW;

Po—transformer no-load Losses, kW;

P—The active power of the transformer, kW;

Q—Reactive power of transformer, kvar;

U—The operating voltage of the distribution network;

U1—the rated voltage of the distribution network;

P’o—Equivalent resistance of each transformer winding;

R—The equivalent resistance of the windings of the distribution transformer.

It can be seen from the above formula that the fixed Losses of the distribution transformer are proportional to the operating voltage of the distribution network, and the short-circuit Losses are inversely proportional to the square of the operating voltage of the distribution network.

Since the no-load Losses of the distribution transformer accounts for 80% of the total Losses, the operating voltage can be appropriately reduced during the low power consumption period or the low load period, and the operating voltage can be appropriately increased during the peak power consumption period and the heavy load period, but the end user’s The voltage offset is within the allowable range.

Method 6: Efforts to balance the three-phase load of the distribution transformer

When the three-phase load current is unbalanced, it not only affects the voltage quality, but also increases the Losses of the distribution transformer.

Therefore, in the daily operation of the distribution transformer, it is necessary to frequently measure the three-phase load current and the neutral line current on the secondary side, and perform the work of balancing the three-phase load current.

The unbalance of the outlet current of the distribution transformer should not be greater than 10%.

Specially configured personnel to monitor the three-phase load of the distribution transformer, analyze the user’s current situation, and issue early warnings to the production department on a regular basis.

Method 7: Do a good job in the economic operation of distribution transformers

  • The operating unit adjusts the operation mode in time according to the change of the load, and disables the no-load or light-load transformer.
  • When the user has 2 or more transformers, adjust the number of transformers put into operation according to the change of load to reduce power Losses.

For example, two distribution transformers of the same capacity can be operated in parallel when the load is greater than the critical load. When the load is less than the critical load, they can be operated individually.

The actual power of the distribution transformer is:

actual power of the distribution transformer

Where: SN—the rated capacity of the transformer;

Po—the no-load Losses of the transformer, kW;

Pk—short-circuit Losses of transformer, kW;

Qo—reactive power Losses when the transformer is no-load, kvar;

QN—reactive power Losses when the transformer is fully loaded, kvar;

Kq—reactive power economic equivalent (the average value is 0.1).

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