Seven ways to combat losses in overhead electrical networks

The electrical network consists of at least 3 key components:

• Generator;
• Consumer;
• Network of wires or power line.

This is an ideal scheme, but in reality it consists of many thousands of wires, several kilometers long, equipment and numerous substations. All of them connect network participants with each other. At the same time, electricity losses occur at each link. As a result, the consumer receives electricity not in the quantity supplied, but in the quantity actually transferred. To prevent these losses from reaching large values, suppliers are constantly looking for solutions, using different methods and techniques. But to select them, it is necessary to determine the cause of the loss of electricity.

They are conventionally divided into:

• Production;
• Technological;
• Commercial.

Development of measures to prevent losses (using the example of a retail chain)

One of the problems of retail chains, which may become the main one for the retail industry in the coming years and even decades, is the fight against losses. With the increase in the share of self-service stores, the consolidation of retail enterprises, the growth of staff and the complication of the organizational structure of retail enterprises, the problem of losses has come to the fore. According to Western European trade statistics, the amount of losses is comparable to 50% of the profits of retail enterprises from trading activities [1]. Losses in their essence can be divided into two very large groups: Known and unknown (see Fig. 1).

Rice. 1. Types of losses

Let us consider in detail the known losses. Known losses are losses caused by partial or complete loss of quantitative or qualitative characteristics of a product in physical terms that can be controlled per unit of time. Known losses include write-offs of expired products, write-offs of low-quality products, losses due to shrinkage, cracking, spraying, crumbling of products, etc. In accordance with Western European and American statistics, identified (known) losses account for 41% of the total losses. In Russia there are norms of natural loss, which stores still rely on in their work. But they were developed not just a long time ago, but in a completely different business situation and are only some kind of third-party guideline, and not numbers reflecting the real state of affairs [1].

How to deal with so many losses? First of all, it is necessary to analyze in which product groups and in what proportion the dynamics of known losses manifest themselves. Next, identify the causes of known losses and develop an action plan to prevent them. A well-designed loss prevention program is not just a plan to keep the store running safely, but is part of daily operations [2].

Loss prevention is the lever that will ensure that targets and plans are met to achieve the main goal - profit. Analyzing the results of inventory in stores of one of the large retail chains of the Ural Federal District, we observe the dynamics of losses for 2011 by region (Fig. 2):

Rice. 2. Dynamics of losses for 2011 in the Urals Federal District by region.

In the regional analysis of losses (known and unknown), presented in Figures 3, 4, 5, we see how the trend lines change during 2011:

Rice. 3. Dynamics of losses for 2011 Perm.

Rice. 4. Dynamics of losses for 2011 Ekaterinburg

Rice. 5. Dynamics of losses for 2011 Chelyabinsk

Since we are talking about known losses, we are interested in the trend line for write-offs. Over the course of the year, the write-off rate is rapidly going down. The main reasons for known losses are write-offs due to expiration date, write-offs due to combat, spoilage, write-offs due to pre-sale preparation (see Fig. 6).

Rice. 6. Losses by cause for 2011

Next, let’s look at the dynamics of product-forming groups in %, which is presented in Table 1.

Table 1

Dynamics of losses by product groups for 2011 in %

The largest share of losses is made up of the “Vegetables and Fruits” and “Meat and Meat Products” product groups. The dynamics can be visually represented in the form of a diagram (see Fig. 7).

Rice. 7. Dynamics of losses for 2011 by product groups.

Thus, at the end of the year, more than 40% of losses are from the group of goods “Vegetables and fruits”, 20% from “Meat and meat deli”.

According to the data presented above, we can conclude that the main problem in stores is working with perishable products. There are many factors influencing the known loss rate. This includes work on pre-sale preparation, work with defects, work on monitoring expiration dates and maintaining rotation of products on the shelf, monitoring temperature conditions for storing equipment in stores, working with complaints, working with product suppliers.

The company has developed a number of measures to reduce losses by product group:

1) A business process (BP) has been developed for filing and reviewing claims regarding the quality of goods to the supplier, which is successfully applied and in the event of receiving a low-quality product from the supplier, the store makes a claim, which is reviewed by the other party and a decision is made;

2) “Quality Hour” was introduced. Every day (before opening and closing the store), sellers must check the expiration dates of the goods that are on the shelf, maintain the rotation of goods, check all labels, the appearance of the goods and remove low-quality goods;

3) The company conducts internal audits of stores aimed at identifying and suppressing violations, in accordance with current legislation;

4) The temperature of the refrigeration equipment is recorded three times a day, thereby checking the compliance of the storage conditions of the products;

5) Cartograms (schemes) for displaying goods have been developed in compliance with the product neighborhood. Especially in the “Fruits and Vegetables” group, where product proximity is very important, since most of the products in this group of products are sensitive to ethylene emissions, and vice versa.

6) Orders of products, mainly perishable ones, are controlled.

7) Upon acceptance of products, all products must undergo incoming inspection for the presence of documents confirming quality and safety, organoleptic characteristics and appearance are checked.

In operation, maintaining all of the above measures is supported by training store personnel and certifying employees before starting work.

Having carried out a number of the above measures, we can observe how the situation has changed based on the results of the 1st quarter of 2012 (see Fig. 8). The dynamics of product-generating groups for the 1st quarter of 2012 is as follows (see Fig. 9).

Rice. 8. Losses by cause for the 1st quarter of 2012

Rice. 9. Dynamics of losses by product-generating groups for the 1st quarter of 2012.

The trend line shows the positive dynamics of reducing losses during 2012. If we compare the loss indicators of the 1st quarter of 2012 with the 1st quarter of 2011, we see that the dynamics are positive, which means that the measures taken really have a positive effect on reducing known losses. The developed program of measures to reduce known losses has yielded positive results.

Literature:

1. Kramarev A. N. Trading Solutions // https://www.ippnou.ru/article.php?idarticle=000423

2. Information portal // https://www.znaytovar.ru/new1142.html

Let's take a closer look at each of them.

Commercial losses occur for the following reasons:

• Errors in calculations and indications;
• Illegal use of electricity;
• Wrong tariffs.

Special calculations and determination of the loss category allow you to reduce non-target costs. For example, technological ones are the task of the electricity consumer. It is possible to reduce losses by adjusting tariffs or upgrading equipment.

Commercial losses affect the supplier’s profit, so special control is carried out over illegal connections, control departments are working, and automatic data collection systems are being introduced.

Technological losses occur during the transmission of electricity through power lines.

Types and structure of losses

Losses mean the difference between the electricity supplied to consumers and the energy actually received by them. To normalize losses and calculate their actual value, the following classification was adopted:

• Technological factor. It directly depends on characteristic physical processes, and can change under the influence of the load component, semi-fixed costs, as well as climatic conditions.
• Costs spent on operating auxiliary equipment and providing the necessary conditions for the work of technical personnel.
• Commercial component. This category includes errors in metering devices, as well as other factors causing under-metering of electricity.

Below is an average graph of losses for a typical electric company.

Approximate loss structure

As can be seen from the graph, the highest costs are associated with transmission via overhead lines (power lines), this accounts for about 64% of the total losses. In second place is the corona effect (ionization of air near the overhead line wires and, as a consequence, the occurrence of discharge currents between them) – 17%.

Corona discharge on a power line insulator

Based on the presented graph, it can be stated that the largest percentage of non-targeted expenses falls on the technological factor.

Main causes of electricity losses

Having understood the structure, let's move on to the reasons that cause inappropriate expenditure in each of the categories listed above. Let's start with the components of the technological factor:

1. Load losses occur in power lines, equipment and various elements of electrical networks. Such costs directly depend on the total load. This component includes:

• Losses in power lines are directly related to current strength. That is why, when transmitting electricity over long distances, the principle of increasing it several times is used, which contributes to a proportional reduction in current and, accordingly, costs.
• Consumption in transformers of a magnetic and electrical nature (1). As an example, below is a table that shows cost data for substation voltage transformers in 10 kV networks.

Losses in power transformers of substations

Non-target consumption in other elements is not included in this category due to the complexity of such calculations and the insignificant amount of costs. For this, the following component is provided.

1. Category of semi-fixed expenses. It includes costs associated with the normal operation of electrical equipment, these include:

• Idle operation of power plants.
• Costs in equipment providing reactive load compensation.
• Other types of costs in various devices, the characteristics of which do not depend on the load. Examples include power insulation, metering devices in 0.38 kV networks, measuring current transformers, surge limiters, etc.

1. Climatic component. Inappropriate consumption of electricity may be associated with climatic conditions characteristic of the area where power lines pass. In networks of 6 kV and higher, the magnitude of the leakage current in the insulators depends on this. In main lines from 110 kV, a large share of the costs falls on corona discharges, the occurrence of which is facilitated by air humidity. In addition, during the cold season, our climate is characterized by the phenomenon of icing on the wires of high-voltage lines, as well as conventional power lines.

   
   Ice on power lines

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Taking into account the last factor, the energy costs for melting ice should be taken into account.

Costs for supporting the operation of substations

This category includes the cost of electrical energy for the operation of auxiliary devices. Such equipment is necessary for the normal operation of the main units responsible for the conversion of electricity and its distribution. Costs are recorded using metering devices. Here is a list of the main consumers belonging to this category:

• ventilation and cooling systems for transformer equipment;
• heating and ventilation of the technological room, as well as internal lighting fixtures;
• lighting of areas adjacent to substations;
• battery charging equipment;
• operational circuits and monitoring and control systems;
• outdoor equipment heating systems, such as air circuit breaker control modules;
• various types of compressor equipment;
• auxiliary mechanisms;
• equipment for repair work, communication equipment, as well as other devices.

Commercial component

These costs mean the balance between absolute (actual) and technical losses. Ideally, such a difference should tend to zero, but in practice this is not realistic.

This is primarily due to the characteristics of electricity meters and electricity meters installed at end consumers. It's about error.

How to reduce power transmission losses?

There are 2 options: reduce the resistance of the wires or the current in the power line. For the first option, wires made of copper and aluminum are used and their cross-section is increased. It is important that the wires are light in weight and the use of perforated cable trays is recommended. Busbar trunking is also used to reduce losses. Its use allows you to save a considerable amount.

In order to reduce the current in a power line, a transformer or station is used.

You can also reduce costs using the following effective methods:

• Optimization of the circuit and operation of the electrical network;
• Equipment modernization;
• Decrease in total power;
• Transformer load optimization.

The selection of the method is carried out by specialists individually for each specific case.

Conclusion

Reducing electricity losses during transmission is a complex work. Of course, this process is very difficult and often financially expensive, but if you achieve the desired result, all your efforts will quickly pay off. The main thing is to do it correctly, competently, and take into account all the details and features. Both parties should be interested in this issue, since only with this approach it is possible to reduce losses and at the same time significantly reduce costs. It is impossible to avoid losses, but it is possible to minimize them. To do this, it is worth using modern equipment, an innovative approach and the experience of leading specialists.