Development of district electrical networks diagrams - drawings

1. Introduction

The purpose of the course design in the discipline "Electric Power Industry" is to systematize, expand and deepen the knowledge obtained during the study of the course materials, as well as acquire skills for independently solving engineering problems.

Selected design solutions should be clearly and competently justified. Reference materials shall be used in the course design process. Design design shall comply with GOST:

Project includes explanatory note - 3040 sheets of A-4 format

and a graphical portion of the A-1 format.

Each section of the explanatory note shall contain:

- setting of the task,

- calculation procedure,

- solution of the problem,

- conclusions and their justifications;

The explanatory note includes:

- task cover sheet,

- table of contents,

- introduction,

- main part,

- list of used literature.

The graphic part of the project contains:

- variants of district electric network diagrams,

- diagrams of selected PI.

Assignment for Course Engineering

Perform the design of the district electrical network for power supply to consumers of substations 1-4. The source data is specified in Table 1.

When executing a project, consider the following:

- electric power supply is provided from two independent sources of unlimited power A and B;

- location of source A coincides with origin of CCS coordinate system;

- the scale of the network plan is 1:1000000 (1 cm in the plan is 10 km. on the ground);

- power factor of consumers of all substations is taken equal to 0.9;

- power supplies A and B have switchgears with rated voltages of 35, 110, 220 kV;

- in the minimum load mode, the load value is 30% of the maximum (specified in Table 1);

- secondary voltage of consumers substations is 610 kV (at the discretion of the project author);

- consumers of electricity of all substations have 70% of the load of the 1st and 2nd categories and 30% - of the 3rd category;

- electric network is designed for II district of Russia in ice and III district in wind.

General guidelines for the implementation of the course project

The basis for the course project is the background data given in section 2, as well as the reference materials contained in the literature (111).

The following issues should be considered during the project:

1. Development of district electric network diagrams, substantiation of structural execution of power transmission lines. Selection of two options for technical and economic comparison.

2. Define the preliminary power allocation in the two selected circuit variants.

3. Selection of rated voltage of electrical network and design of lines.

4. Selects sections and wire tags.

5. Determination of power losses in lines.

6. Selection of number and power of transformers.

7. Determination of power losses in transformers.

8. Balance of active and reactive capacities in the system.

9. Selection of external connection diagrams of substations and their design.

10. Technical and economic comparison of variants of circuits of the district electric network.

10.1. Determination of capital costs for construction of district electric network.

10.2. Determination of annual operating costs.

10.3. Define total estimated costs for each of the two variants. Select the most rational circuit option.

11.Electrical calculation of the selected circuit variant for the main operation modes of the network (maximum, minimum, post-accident).

11.1.Representation of load capacities to HV buses. Definition of design loads.

11.2.Determination of power flow distribution without taking into account power losses, as well as taking into account power losses.

11.3.Define the actual power flow distribution for all three modes.

11.4.Determination of voltage on high voltage buses of substation.

11.5.Selecting branches from transformers; real voltage on LV buses of substations.

11.6. Determination of power of compensating devices.

12. Mechanical calculation of wires.

12.1.Determination of design conditions, stresses in the wire, slewing boom, dimensions of power transmission line.

12.2.Selection of supports type.

Main steady-state modes of network operation

The state of the electrical network at any time is called the network mode and is characterized by the following mode parameters:

- active and reactive capacities in the network elements;

- frequency;

- voltage at consumers and at nodal points of the network;

- value of currents flowing through the sections;

- divergence angles of E.D.S. vectors and stresses;

- power losses and voltage drops in the network elements.

The task of calculating the mode is to find its parameter in order to determine the conditions under which the network equipment operates, effective methods are proposed to reduce power losses, voltage levels at substations are set and measures to maintain them within acceptable limits.

The nature of the network mode is determined by three main factors:

- load schedules of individual substations;

- operating modes of generating sources;

- conditions of power exchange of the considered power system with neighboring ones.

In general, network mode is a complex function of all these factors, but for a number of systems the influence of one determining factor can be distinguished. So in the considered district electric network, the determining factor will be considered the loads of the network.

To determine the state of the electrical network, let us limit ourselves to considering the following characteristic normal modes:

- maximum loads in winter days, when power flows occur associated with the greatest electricity consumption;

- minimum loads in summer days.

The modes of greatest and least loads of the power system in many cases can be considered quite indicative, since the parameters of the remaining modes must be between the calculated limit ones.

To determine the maximum values of power flows, it is necessary to consider a particularly heavy post-accident mode that occurs when either the busiest line or significant generating power is disconnected. The substation loads correspond to the maximum mode.

Thus, in the course project it is proposed to calculate three modes of the network - the maximum, minimum and most severe post-accident.

The initial data for the calculation of any mode are the capacities of consumers and power plants - for maximum and post-accident power modes are specified in the table of options, for minimum - are determined by load schedules, or are accepted within 30-60% of the nominal.

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