Substation 110-10 kV, electric network. 110 kV

Introduction

Agricultural areas can be supplied from district power systems (centralized power supply) or from district or village power plants (local or decentralized power supply).

Currently, agricultural consumers mainly have centralized electricity supply, carried out from the tires of stations and transformer substations (TPs) of power systems or traction TPs of electrified railways. Local electricity supply is characteristic of sparsely populated and inaccessible areas.

The main peculiarity of agriculture power supply compared to the power supply of industry and cities is the supply of electricity to a large number of relatively low-power dispersed facilities.

Currently, in connection with the transition of agriculture to an industrial basis, the construction of large livestock complexes, an increase in electricity consumption in production and in everyday life, the unit capacity of electric consumers is growing. But the structure of the organization of agricultural production, the low density of the population of rural areas determine the low density of electric loads and the significant length of electric networks.

The basis of the rural power supply system is 0.38-110 kV electric networks, from which mainly (more than 50% of the design load) agricultural consumers, including household utilities, land reclamation and water management facilities, as well as enterprises and organizations designed for household and cultural services to the rural population, are supplied with electricity.

Agricultural electric networks are divided into two types: feed and distribution.

Power supply networks are used to transfer electricity from the buses of stations and TC power systems to intermediate transformer TC. These networks consist of lines 35 and 110 kV and MS 35110/10 kV.

Distribution networks consist of 6, 10, 20 kV and 6/0.4 PS lines; 10/0,4; 20/0.4 kV.

A voltage of 6 kV is allowed only when the existing networks of this voltage are expanded. Distribution networks of 20 kV were used only in a number of areas of the country (for example, in the Baltic States).

When agricultural facilities are located near 35 kV lines and if they are significantly removed from 35/10 kV substations, it is advisable to supply consumers with power from 35/0.4 kV PS ("deep input" substations).

Low voltage distribution networks consist of 0.38 kV lines and directly supply electricity to the electric receivers connected to them.

Currently, a three-stage 110/35/10/0.4 kV power distribution system with two-stage 110/35/0.4 kV and 110/10/0.4 kV subsystems is mainly used.

The main problem that can be encountered when considering the power supply of agricultural consumers is the reliability of the power supply. Improving the reliability of power supply is a technical and economic task. The selection of means to provide reliable power supply can be carried out based on the minimum of the reduced costs, taking into account damage from power interruptions or in the absence of damage data - according to the permissible standardized time for disconnection of consumers.

To ensure the reliability of power supply to agricultural consumers, the following technical measures are provided; improving the reliability of individual elements of electrical networks, including through the use of new materials; partitioning of networks with the help of circuit breakers with automatic disconnectors, automatic separators and disconnectors; both network and local, energy and technology redundancy; approximation of voltages 35 - 110 kV to consumers, decompression of AR 35 - 110 kV, which allows to reduce the length of electric networks 10 kV; increase in the number of double-transformer IR 35 - 110 kV and two-way substations; decompression of 10/0.4 kV TP and separate power supply from them of industrial and municipal consumers; use of static capacitor batteries to compensate for reactive power.

VL partitioning, reducing the network length that is disconnected in case of accidents, reduces the number of disconnections of the lowering IR. Non-automatic and automatic partitioning is used. Non-automatic partitioning primarily reduces the number and duration of intentional disconnections; it is performed using line disconnectors in addition to automatic partitioning. The presence of sectionalizing disconnectors facilitates the detection of ground faults, reduces the number of consumers that are disconnected during repair work. On distribution lines with voltage up to 35kV inclusive, it is necessary to install disconnectors on all branches whose length is more than 1.52km, and on VL 35 kV supplying TPs 35/10 kV, on all branches with length more than 0.5km. If the length of the branches to the consumer TP 100200m, it is recommended to install substation disconnectors at the beginning of the branches.

During automatic partitioning, the VL is divided into sections, at the beginning of which special partitioning devices are installed that disconnect the damaged sections, without disrupting the normal operation of the rest of the line. The optimal installation locations for sectionalizing devices are determined based on the condition of maximum reduction of damage to agricultural consumers from power interruptions. For efficient use of automatic partitioning, a partition map is drawn up, which is used to identify suitable places for installing partitioning devices, determine the sequencing of individual lines, as well as to calculate equipment requirements.

The use of network redundancy implies a fairly high reliability of the networks themselves. The most expedient is an open circuit of normal operation of the lines with automatic connection of intact sections to another power source in case of accidents. Along with network redundancy, local redundancy is used, since under adverse atmospheric conditions (ice, hurricane, thunderstorm, etc.), two lines can be damaged simultaneously.

Backup power plants are intended for selective redundancy of consumers of categories I and II.

In order to improve the reliability of power supply, organizational and technical measures are also of great importance, especially with regard to the reduction of intentional disconnections.

Repair and other types of work in networks should be subject to the requirement of minimum damage to consumers, coordinating them with the operating modes of agricultural consumers. To reduce the number of disconnections of consumers, it is necessary to combine work carried out at different voltages in time.

An effective means of improving the reliability of power supply is the rational organization of the operation of electrical networks and installations. Since the accuracy of the technical and economic calculations of the reliability of the power supply depends on the reliability of the initial data, the most important task of the operation is to organize an information collection and processing system for assessing the reliability of the power supply and the damage values ​ ​ from power interruptions for specific consumers (based on a thorough economic analysis of the actual data).

An important factor in improving the reliability of power supply is strict compliance of maintenance personnel with technical operation rules. In particular, this applies to mandatory regular rounds of distribution VL and inspections of mast TPs.

Historical reference

Overhead transmission lines using self-supporting insulated wires have been known for more than 50 years and are in increasing use.

For the first time, low-voltage insulated wires were used in the USA and Canada, and later in Western Europe: Sweden, Finland, Norway and France. Since the 1980s, these countries have seen a significant increase in the length of overhead power lines made by isolated and protected wires. For the first time, PIS began to be used in the early 1960s.

The use of self-supporting insulated and protected wires is by far the most progressive and promising way to develop electric distribution networks.

Compared to traditional overhead power transmission lines (VL), lines using self-supporting insulated (PIS) and protected (VL) wires have a number of design features - the presence of insulation cover on current-carrying conductors, increased mechanical strength, progressive coupling and branch fittings, etc. These features lead to a significant increase in the reliability of power supply to consumers and a sharp decrease in operating costs, which, in turn, determines the high economic efficiency of using insulated wires in distribution electric networks.

Design of 620 kV overhead power transmission lines with protected wires shall be carried out in accordance with the requirements of the "Electrical Installation Rules" (PUE) [8], seventh edition, chapter 2.5. Overhead transmission lines above 1 kV.

5.2 General information on 620 kV overhead transmission lines with protected wires

To date, the following options can be considered as a more promising and progressive alternative to non-insulated wires for 620 kV HVs:

- secure wires of PIS;

- power cables for VL 620 kV;

- universal cables.

The protected wire (grade SIP3, SAX, SAXW) is a single-core multi-conductor coated with a protective coating. The conductor is made of aluminum alloy, a protective layer of light-stabilized crosslinked polyethylene. The wire may be manufactured with a water-swelling layer under a containment to protect the aluminum core from atmospheric moisture.

The 620 kV overhead power cable (SAXKAW grade) is a bundle of three single-phase power cables twisted around the carrier cable. Current-conducting cores are made of compacted aluminium carrying steel rope. Cables have longitudinal and transverse protection against moisture penetration.

The universal cable (MULTIWISKI brand) consists of three single-phase twisted cables. Designed for installation on VL 620 kV supports, for laying in the ground in the form of an underground cable line, as well as for laying on the bottom of artificial reservoirs and natural water barriers in the form of an underwater cable line. Power cables for 620 kV AC and universal cables are less common in practice, their use is advisable in some cases with increased technical and/or environmental requirements for power transmission lines in specific conditions.

The use of secure wires is the most acceptable and common technical solution for 620 kV HF.

Types of wires of PIS grade

There are three main systems of self-supporting insulated wires:

- Finnish "AMKA" system, where the non-insulated zero conductor is a carrier wire. The modified system "AMKA T," with an isolated carrier zero conductor, this system is used in Finland, the Far and Middle East, South America.

- French system. In terms of technical characteristics it resembles "AMCU T," the systems differ in the cross section of the carrying zero conductor. In addition to France, this system is used in Belgium, Spain, Italy and Greece.

- a four-wire system where all four conductors carry a mechanical load, all phase and zero conductors are isolated, and the mechanical load is equally distributed between them. The four-wire system is mainly used in Sweden, Germany, Austria, Great Britain, Ireland, Portugal, Poland and is becoming increasingly popular in other countries.