Structure, types of power losses ...
Electricity losses in power grids are the most important indicator of the efficiency of their work, a clear indicator of the state of the electricity metering system, the efficiency of power sales activities of energy supplying organizations. This indicator is more and more indicative of the accumulating problems that require urgent solutions in the development, reconstruction and technical re-equipment of power grids and means of their operation and management, in increasing the accuracy of electricity metering, the effect Nost cash collection for electricity supplied to consumers, etc. According to international experts, the relative losses of electricity during its transmission and distribution in the electrical networks of most countries can be considered satisfactory if they do not exceed 4-5%. Losses of electricity at the level of 10% can be considered as the maximum permissible from the point of view of physics of transmission of electricity through networks. It is becoming increasingly obvious that a sharp exacerbation of the problem of reducing electricity losses in electrical networks requires an active search for new ways to solve it, new approaches to the selection of appropriate measures, and most importantly, to organizing work to reduce losses. In connection with the sharp reduction in investment in the development and technical re-equipment of electrical networks, in improving the management systems of their modes, electricity metering, a number of negative trends have appeared that negatively affect the level of losses in networks, such as: outdated equipment, physical and moral obsolescence of electricity metering , inconsistency of installed equipment transmitted power. From the aforementioned, it follows that, against the background of the ongoing changes in the economic mechanism in the energy sector, the economic crisis in the country, the problem of reducing electricity losses in electric networks has not only not lost its relevance, but rather has become one of the tasks of ensuring the financial stability of energy supplying organizations.
Some definitions are:
Absolute loss of electricity - the difference between the electricity released into the electrical network and useful released to consumers.
Technical losses of electricity - losses due to physical processes of transmission, distribution and transformation of electricity, are determined by calculation. Technical losses are divided into semi-permanent and variable (dependent on the load).
Commercial losses of electricity are losses defined as the difference between absolute and technical losses.
STRUCTURE OF COMMERCIAL LOSSES OF ELECTRIC ENERGY
In the ideal case, the commercial loss of electricity in the electrical network should be zero. It is obvious, however, that in real conditions the supply to the network, the productive supply and technical losses are determined with errors. The differences of these errors are in fact the structural components of commercial losses. They should be minimized wherever possible by implementing appropriate measures. If this possibility is not available, it is necessary to amend the readings of electricity meters, compensating for the systematic errors of electricity measurements.
Measurement errors of the network power supplied and useful to the consumers.
The measurement error of electricity in the general case can be divided into many components. Consider the most significant components of measurement systems (IR) errors, which may include: current transformer (CT), voltage transformer (TN), electricity meter (ESS), connection line to tn. The main components of the measurement errors released into the network and the useful electric power are:
- errors of measurement of electricity in normal operating conditions of IC, determined by the accuracy classes of TT, TN and SC;
- additional errors of measurement of electricity in real operating conditions IC, due to;
- underestimated against the normative power factor of the load (additional angular error);
- the influence on the FE of magnetic and electromagnetic fields of various frequencies;
- underloading and overloading of TT, TH and FE;
- asymmetry and level of voltage supplied to the IR;
- the operation of solar cells in unheated rooms with unacceptably low temperatures, etc .;
- insufficient sensitivity of solar cells at their low loads, especially at night;
- systematic errors caused by excess of the service life of the IC;
- errors associated with incorrect connection diagrams of electricity meters, current transformers and voltage transformers, in particular, violations of the phasing of the connection of meters;
- the errors caused by faulty electricity metering devices;
- errors of meter readings due to;
- errors or deliberate distortions of the testimony records;
- non-simultaneity or non-compliance with the established deadlines for meter readings, violation of counters bypass schedules;
- errors in determining the conversion factors of meter readings into electricity.
It should be noted that with the same signs of the components of the measurement errors of the supply to the network and the productive supply, the commercial losses will decrease, and for different, they will increase. This means that from the point of view of reducing the commercial loss of electricity, it is necessary to pursue a coordinated technical policy for improving the accuracy of measuring the supply to the grid and the effective supply. In particular, if we, for example, unilaterally reduce the systematic negative measurement error (modernize the accounting system) without changing the measurement error, commercial losses will increase, which, by the way, is the case in practice.
Commercial losses due to underestimation of productive supply due to shortcomings in energy sales .
These losses include two components: losses in billing and losses from electricity theft.
This commercial component is due to:
- the inaccuracy of data on consumers of electricity, including insufficient or erroneous information about the concluded contracts for the use of electricity;
- errors in invoicing, including non-exposed invoices to consumers due to the lack of accurate information on them and continuous monitoring of the actualization of this information;
- lack of control and errors in billing customers using special rates; .
- lack of control and accounting of adjusted accounts, etc.
Losses from electricity theft
This is one of the most significant components of business losses, which is a concern of power engineers in most countries of the world. Experience in combating the theft of electricity in various countries is summarized by a special Expert Group on the study of issues related to the theft of electricity and unpaid bills (defaults). The group is organized within the framework of the research committee on economics and tariffs of the international organization UNIPEDE. According to a report prepared by this group in December 1998, the term “electricity theft” is used only in cases where electricity is not taken into account or is not fully recorded through the consumer’s fault, or when a consumer opens the meter or disrupts the power supply to reduce the meter’s consumption of electricity consumed. A synthesis of international and domestic experience in combating the theft of electricity has shown that mainly household consumers are involved in these thefts. There are electric power thefts carried out by industrial and commercial enterprises, but the volume of these thefts cannot be considered decisive. Electricity thefts have a fairly clear upward trend, especially in regions with poor heat supply to consumers during cold periods of the year. And also in almost all regions in the autumn-spring periods, when the air temperature has already greatly decreased, and the heating has not yet been turned on. There are three main groups of ways of theft of electricity: mechanical, electrical, magnetic.
Mechanical methods of theft of electricity
Mechanical intervention in the work (mechanical opening) of the counter, which can take various forms, including:
- drilling holes in the bottom of the case, the lid or glass counter; insertion (into the hole) of various objects such as 35 mm wide films, needles, etc. in order to stop the rotation of the disk or reset the counter;
- moving the counter from the normal vertical to the semi-horizontal position in order to reduce the speed of rotation of the disk;
- unauthorized breakdown of seals, a violation in the alignment of the axes of the mechanisms (gears) to prevent the full registration of power consumption;
- rolling out glass when inserting a film that will stop disc rotation.
Usually, mechanical intervention leaves a mark on the meter, but it is difficult to detect if the meter is not completely cleaned of dust and dirt and inspected by an experienced technician. The mechanical method of theft of electricity can be attributed to the rather widespread in Russia intentional damage to an AOC by household consumers or theft of meters installed on the stairwells of residential buildings. As the analysis showed, the dynamics of deliberate destruction and theft of counters practically coincides with the onset of cold weather with insufficient heating of the apartments. In this case, the destruction and theft of the counters should be considered as a peculiar form of protest of the population against the inability of local administrations to provide normal housing conditions. The aggravation of the situation with the heat supply of the population inevitably leads to an increase in commercial losses of electricity, which is already confirmed by the sad experience of the Far Eastern and some Siberian energy systems.
Electric ways of theft of electricity
The most common in Russia, the electric method of electricity theft is the so-called "surge" on an air line made with bare wire. Methods such as are also widely used:
- inverting the phase of the load current;
- the use of various types of “hawsers” to partially or fully compensate the load current with a change in its' phase;
- shunting the current circuit of the meter - installation of the so-called "short circuit";
- grounding the zero load wire;
- violation of the alternation of phase and zero wires in the network with a grounded neutral supply transformer.
If the meters are connected via metering transformers, the following may also be used:
- disconnect current circuits TT;
- Replacement of normal fuses for TN fused, etc.
Magnetic methods of theft of electricity
The use of magnets on the outside of the meter may affect its performance. In particular, it is possible with the use of a magnet to slow down the rotation of the disc when using old types of induction counters. Currently, new types of counters manufacturers are trying to protect from the influence of magnetic fields. Therefore, this method of theft of electricity is becoming increasingly limited.
Other ways of electricity theft
There are a number of ways of theft of electricity of purely Russian origin, for example, theft through frequent changes of owners of a company with a permanent re-issuance of contracts for the supply of electricity. In this case, energy sales are not able to keep up with the changes in the owners and to receive electricity charges from them.
Commercial losses of electricity due to the presence of ownerless consumers
Crisis phenomena in the country, the emergence of new joint-stock companies led to the fact that in most power systems in recent years, residential houses, shelters, entire residential settlements that are not on the balance of any organizations have appeared and have been for quite some time. Electricity and heat supplied to these houses, tenants do not pay anyone. Attempts by the power systems to shut down defaulters do not give results, since residents once again unauthorizedly connect to the networks. Electrical installations of these houses are not serviced by anyone, their technical condition threatens with accidents and does not ensure the safety of life and property of citizens.
Commercial losses due to non-simultaneous payment for electricity by household consumers - the so-called “seasonal component”.
This very significant component of commercial energy losses occurs due to the fact that household consumers are not objectively able to simultaneously take meter readings and pay for electricity. As a rule, payments are lagging behind the real electropower, which, of course, introduces an error in the determination of the actual productive supply by the household consumer and in the calculation of the actual unbalance of electricity, since the lag can be from one to three months or more. As a rule, in the autumn-winter and winter-spring periods of the year there are underpayments for electricity, and in the spring-summer and summer-autumn periods these underpayments are compensated to a certain extent. In the pre-crisis period, this compensation was almost complete, and the loss of electricity for the year rarely had a commercial component. Currently, autumn-winter and winter-spring seasonal underpayments for electricity are much higher in most cases, the total payment in other periods of the year. Therefore, commercial losses occur by months, quarters and for the year as a whole.
Errors in the calculation of technical losses of electricity in electrical networks
Since the commercial loss of electricity can not be measured. They can be calculated with one or another error. The value of this error depends not only on the measurement errors of the volume of electricity theft, the presence of "orphan consumers" and other factors discussed above, but also on the error in the calculation of technical losses of electricity. The more accurate the calculations of technical losses of electricity will be, the more obviously the estimates of the commercial component will be, the more objectively you can determine their structure and outline measures to reduce them.