Electrical distribution networks with a voltage of 6-10 kV are one of the oldest technological solutions in Russia. Many lines have a venerable age and a multi-stage history of modernization. Despite the planned reduction in the share of such overhead lines in the country’s overall power grid, the length of medium-voltage overhead lines amounts to thousands of kilometers. There are common cases when the length of overhead lines exceeds standard values. All this does not contribute to increasing the reliability of the electrical grid infrastructure.
According to available data in Russia, the duration of power outages ranges from 70 to 100 hours per year [1]. This figure is almost 2 times higher than in Western countries [1]. According to experts, for every 100 km of overhead power lines, up to 26 outages are recorded annually [1]. This article discusses the main causes of emergency outages of 6-10 kV high-voltage power lines.
Fig.1. High-voltage power lines (VL) 10 kV
Automation systems and devices in 6-10 kV networks
Overhead lines are made for the most part using steel-aluminum and aluminum wires, supports made of reinforced concrete or wood. Today, the following automation systems and devices are used in 6-10 kV networks:
- restart devices;
- devices for switching on backup power;
- sectioning devices;
- control and signaling devices.
Power lines are connected in an extensive network through an automatic transfer point. When the network load is from 10 to 100 kVA, pole-type substations are used, which are installed on a support. For loads from 160 kVA, closed or kiosk substations are most often used. In 6-10 kV electrical networks, the installation of external vacuum switches and fuses-disconnectors is provided.
Rice. 2. Closed transformer substation
Voltage drops
Causes
Voltage surges in the network (increase and decrease) can be caused by:
- disconnecting several powerful devices from the network (the load drops sharply and the voltage rises sharply);
- unstable operation of transformer substations;
- zero break or weakening of grounding;
- accidents;
- overload;
- the use of poor materials, poor-quality installation of electrical house wiring;
- welding work.
What is acceptable and what is not
Any service must be provided with high quality, including electricity supply services. The power supply organization must provide:
- uninterrupted 24/7 power supply throughout the year;
An interruption in the provision of public electricity supply services is not allowed if it may lead to the disconnection of networks and equipment that is part of the common property in an apartment building, including pumping equipment, automatic process protection devices and other equipment that ensures trouble-free operation of in-house engineering systems and safe conditions residence of citizens.
- constant compliance of voltage and frequency of electric current with the requirements of the legislation of the Russian Federation on technical regulation (GOST 32144-2013).
How to compensate for damage due to a power surge
If there is a strong surge in voltage, household appliances may burn out. Each device is designed for rated voltage with small deviations, and if there is a surge, insulation breakdown and breakdown may occur. Washing machines, routers, computers and other electronics are quite expensive items, so it's useful to know what to do to repair the damage.
The first step is to call the emergency dispatch service
or directly to the management organization, explain that there was a power surge and the equipment was out of order, submit a request to call an electrician.
When the representatives of the management authority and the electrician arrive, you need to make sure that a report is drawn up about the power surge
and which devices are out of order. It is good if a representative of the electricity supply organization is also present when drawing up the act.
Then you need to assess the extent of the damage caused.
. To do this, you can take the equipment to a service center or to a specialized organization involved in examination. Experts will determine the cause of equipment failure and give an opinion on maintainability.
The price of a new device that you buy to replace a broken one, if it cannot be repaired, or the cost of repairing the device will be the amount of compensation. You can also demand compensation for the costs of the examination, for the services of a lawyer (if you turned to him to resolve this situation), and demand compensation for moral damage. True, in most cases, compensation for costs of legal services and moral damage is carried out only in court.
Next, submit an application for compensation for damage caused
, attach a certificate and an expert opinion to the application. You can contact a consumer protection organization - they will help you prepare a claim and fill out the requirements correctly.
If the power supply organization does not want to resolve the situation peacefully, you can contact Rospotrebnadzor, the prosecutor's office, or file a lawsuit.
As a consumer, you are in a weak position, unable to prove the fact of a voltage drop (you simply do not have the necessary measuring equipment for this). The RF Supreme Court ruled that the burden of proof in this case lies with the supplier. The electricity supply organization must prove that the damage to the property of the electricity consumer was caused not due to a voltage drop in the electrical network, but for other reasons.
In addition to compensation, the court will impose a fine in your favor in the amount of 50% of the compensation amount for failure to voluntarily meet the consumer’s requirements. This is provided for in paragraph 6 of Article 13 of the Law of the Russian Federation of 02/07/1992 No. 2300-1 “On the Protection of Consumer Rights”.
How to protect equipment during power surges
It is difficult to predict the outcome of a case in court, and obtaining compensation takes a lot of time and effort. Therefore, it is best to protect the equipment in your apartment from voltage surges.
The most common technical solution to this problem is the installation of a relay, UPS (uninterruptible power supply) or stabilizer. You can choose the appropriate option by looking at the relevant forums on the Internet to see the experiences of those who have already installed protection. You can also consult with electricians.
Malfunctions in control systems of automated systems
Automated telecontrol and telesignaling tools provide the ability to monitor the correct operation of installed restart devices, backup power switching devices, and automated sectioning devices. However, when introducing such functionality into the existing medium voltage overhead line infrastructure, certain problems arise. Let's highlight the main ones:
- distortion of the received data due to the impact of adverse meteorological conditions;
- the need to use special encoding and decoding equipment;
- the need to invest significant funds in the process of introducing technology and operating such systems.
Rice. 3. Modernization of medium voltage overhead lines
alternative energy
This includes solar panels and wind generators. Alternative energy can be a good option for a private home. Firstly, you can always find a place on the roof of a house or on a site for installing equipment. Secondly, the cost of energy production is zero, i.e., apart from periodic simple maintenance, the owner of a country property will not incur any costs for electricity. There is no noise during operation. But these systems also have their disadvantages:
- Low power. The accumulated energy will provide backup, emergency power supply to the home, but you should not count on powering all consumers, especially powerful ones.
- Dependence on weather factors. The absence of sunlight or wind immediately limits the possibilities of alternative energy - in bad weather conditions, you can only use the reserve accumulated in the batteries.
- High price. Solar panels and wind generators are expensive, and not every country house owner can afford to buy them. Installation and commissioning will also require financial costs.
Reasons for shutting down power lines
According to information from power grid companies, overhead power lines with a total length of more than 1.1 million km are currently in operation in Russia. In the European part of the country, overhead lines are mostly made of AC wires with a cross-section of 35 -70 square meters. mm. Up to 60% of the lines were put into operation before 1975. Most of these power grids have exhausted their standard operational life.
Rice. 3. Recommended distances between overhead line supports
New overhead power lines are being put into operation in insufficient quantities. At the same time, with an increase in the number of consumers, it is used, as a necessary measure, to exceed the distance between support pillars. The excess reaches two or more times [1]. These factors lead to an increase in the number of outages in power grids and reduce the quality and reliability of lines. An analysis of recorded emergency shutdowns shows that for the most part, stable shutdowns prevail. This parameter continues to show steady growth, especially in rural areas.
The increasing number of trips has a significant impact on the performance of connected automatic reclosers (ARs). It is worth noting that autorecloser devices are not installed on all circuit breakers. This is explained by the fact that drives of outdated models are often used.
The main causes of accidents leading to disconnection of overhead lines with voltage of 6-10 kV:
- wire break;
- mechanical damage to supports and insulators;
- physical wear and tear of materials and equipment;
- ground fault;
- tripping of fuses in transformer substations;
- exposure to natural precipitation and factors;
- relay protection tripping
- other extraneous influences.
According to statistics, the most common causes of power outages are the activation of relay protection and automation systems, the negative impact of natural phenomena (sharp gusts of wind, the formation of ice and snow cover on wires.
Despite the fact that power grid companies are in some places carrying out reconstruction work and modernizing existing networks, the number of outages is significantly higher than in Western countries. In addition, electricity losses in 6-10 kV distribution networks have increased. To correct the situation, it is necessary to increase the volume of capital expenditures for the reconstruction of existing infrastructure.
Ways to improve the efficiency of medium voltage overhead lines
In the medium term, overhead lines with low losses and high throughput along with a long line length will become effective. To improve the efficiency of existing and newly introduced overhead lines, network operators have a number of options:
- conducting regular technical audits and diagnostics of the technical condition of existing infrastructure;
- development of a balanced program for the development of electrical distribution networks for the coming years;
- modernization and replacement of infrastructure elements whose standard service life has been exceeded;
- use of protected wires in rural areas and forested areas;
- ensuring the adaptability of networks to increased electrical loads, the introduction of new technologies and automation of electrical networks.
