Sawmill power supply

Contents

CONTENTS

DESIGN ASSIGNMENT

PAPER

LIST OF GRAPHIC DOCUMENT SHEETS

LIST OF SYMBOLS AND SYMBOLS

INTRODUCTION

1 ANALYTICAL OVERVIEW

1.1 Overview of modern power transformers and KTP

1.1.1 Classification of TP

1.1.2 10/0.4 kV transformer classification of distribution networks

1.2 Overview of switchgear, switching and protection equipment

1.3 Relay Protection Automation

2 PROCESS PART

2.1 General characteristic of the power supply object

2.2 Existing power supply scheme

2.3 Analysis of existing problems

RESEARCH PART

3.1 Calculation of electrical loads

3.2. Reactive power compensation

3.3 Selection of number and power of power transformers

3.4. Selection of substation switching and distribution electrical equipment

3.5 Cable Line Selection

3.6 Selection and calculation of protection devices

3.7 Calculation of grounding device of electrical installations

CONCLUSION

LIST OF LITERATURE

Paper

This diploma project is a study of the possibility of reconstructing the power supply system in accordance with the current capacity.

The project considered the current power supply system, analyzed the current problems, proposed ways to solve them.

Based on the calculation of electrical loads, taking into account the consumed reactive power, power transformers are selected. Taking into account the calculations, the substation electrical equipment was selected: circuit breakers, 0.4 kV switches, disconnectors, 0.4 kV buses in 10/0.4 kV TP, current transformers.

The explanatory note contains 65 pages of typewritten text.

The graphic part contains 5 drawings of A1 format.

List of symbols and symbols

ALT - Automatic reserve entry

APV - Automatic repeated switch-on

HV - High voltage

GZ - Gas protection

DZ Remote protection

DFZ - Differential phase protection

KTP - Complete transformer substation

Short circuit - Short circuit

Switchgear - package switchgear

CP - Compensating device

Power transmission line

LV - Low voltage

Switchgear - Switchgear

RP - Distribution Point

TP - Transformer substation

SHRA - Distribution busbar

SCH - Lighting Shield

Introduction

The electric power industry is one of those industries that form the material basis of technological progress in all spheres of economic and social life of society, the basis of its normal functioning and life support. That is why, in economic and socially developed countries, electricity is one of the priority sectors of the economy.

The electric power industry is one of those industries that form the material basis of technological progress in all spheres of economic and social life of society, the basis of its normal functioning and life support. That is why, in economic and socially developed countries, electricity is one of the priority sectors of the economy.

Under present conditions, it is difficult to imagine the functioning of any sphere of the economy without the use of electricity, regardless of its consumption. The previous, current and upcoming developments and changes in the economy of the country have necessitated a reorganization of the electricity complex, which consists in improving the reliability and efficiency of energy systems as a whole.

As a result, the reliability of electricity supply in recent years is practically unchanged, remaining low compared to similar indicators of foreign countries. These and other problems require their solution in the development of a distribution electric grid complex, the creation of a new generation of networks corresponding to the world level.

The object of the study in the presented work is a sawmill. The subject of the study is the power supply of the workshop.

The purpose of the study is to develop a project for the reconstruction of the power supply system in accordance with the current capacity .

In accordance with the goal, the following tasks are defined:

- calculation of power equipment power of the pump station;

- selection of substation power transformers;

- selection of protection devices;

- selection of cable lines;

- earthing calculation.

To solve the tasks, the work is divided into three chapters.

The first chapter provides an analytical overview of power transformers, transformer substations and relay protection and automation equipment.

Chapter 2 of work is devoted to the analysis of the power supply system of the enterprise. The shop plan, list of electrical equipment is given. The group on fire hazard, explosion safety, the degree of reliability in electrical safety is determined. The power supply center of the power supply system is selected. Grounding degree, climatic design of electrical receivers, degree of protection of electrical equipment is selected.

The power supply system is designed in the third chapter. Based on the calculation of electrical loads, taking into account the consumed reactive power, power transformers are selected. Taking into account the calculations, the substation electrical equipment was selected: circuit breakers, 0.4 kV switches, disconnectors, 0.4 kV buses in 10/0.4 kV TP, current transformers.

The practical importance of the work is the development of a project for the reconstruction of the power supply system for the sawmill.

Overview of switchgear, switching and protection equipment

For the most part, the operation of electrical hardware devices is not limited to the performance of one particular function, but, on the contrary, is associated with the implementation of a whole set of actions. This creates some difficulty in dividing such devices into specific types and groups.

In order to classify electrical devices, it is important to distinguish the main functional features of specific types of electrical equipment:

Switching devices. Such equipment serves to open and close electric current circuits. Various knife switches, switches, disconnectors belong to such devices.

Security devices. Devices protect conducting elements of electric circuits from voltage drops, increased load of the network and short circuits. The presented protection functions can be implemented in various types of fuses and relays.

Devices regulating the starting of electric machines. Devices of this kind are designed to ensure a smooth start and stop of industrial electric current consumers. The devices control the speed of rotation of the engine armature. Such devices include starters, rheostats, contactors.

Limiting sets. Such devices are called reactors and dischargers, they have the function of limiting short-circuit currents and overvoltage.

Devices providing control of various parameters of electrical circuits. The most common types of such devices are sensors and relays.

Devices allowing adjustment and modification of various parameters of electrical equipment. Such devices include regulators and stabilizers.

Measuring devices. The function of this equipment is to insulate the primary switching line from the circuits of measuring instruments and protective devices.

Devices for mechanical works. The main element of such devices is an electromagnet designed to fulfill specific functions: a lifting electromagnet, an electromagnetic brake.

Switching electrical devices are widely used in various industries. It is difficult to imagine how various tasks of operating and performing operations related to electrical equipment would have been performed without this functional device.

The switching electrical device is used to disconnect and close the electrical circuit using a contact group. Simply put, such a device can be called a switch. The main types of the presented device include: choppers, switches, contactors, relays. Despite the fact that these devices have almost the same principle of operation, they all have a number of differences from each other.

The chopper refers to the simplest switching device. The apparatus is manually operated by means of a handle. This type of device is designed for large current values.

Switches have different modifications. In industrial applications, the most common types of such devices include oil switches. Such switches are designed for voltage up to 220 kV. The oil, in this case, serves to suppress/suppress the current arc passing through it. Air and electric gas switches deserve special attention. Arc quenching, that is, the interruption of electric current supply, occurs due to the supply of a jet of compressed air or electronegative gas.

A fundamentally new method of opening a conductive line is embodied in electromagnetic switches. The principle of operation of such a device is as follows: the electric arc burns under normal conditions at atmospheric pressure - the circuit is turned on. As soon as it is necessary to open the circuit, a strong magnetic field is supplied towards the arc. Due to the effect of the magnetic field, the arc begins to stretch and ultimately splits, thereby opening the conductive line.

The relay is designed to open and close the electrical circuit. The main characteristic property of this switching device is a fundamentally new way of operating the contact pair. The electromagnetic relay, as in the contactor, under the influence of electric current, drives the electromagnet core with contacts installed on it, which leads to closure of the circuit. The method of acting on the relay contact pair can be not only electric, but also thermal or acoustic.

Contactors are a kind of electromagnetic relay. The main purpose is to turn on and off the conductive line of power circuits. Contactors can be used in both AC and DC circuits. Contactor operation principle is based on electromagnetic effect. The core of the electromagnet of the contactor, under the influence of electric current, engages a movable contact, which, due to such a movement, is pressed against the fixed contact and the circuit closes. Once the current supply is stopped, the core returns to its original position and the contacts open.

High voltage electrical devices include various devices that perform the functions of controlling, protecting and monitoring electrical circuits and systems. The list of types of high-voltage electric devices is similar to the above-mentioned list of electric devices. These types of devices include:

switching devices;

earthing devices for separate sections of the electric current circuit (earthing terminals);

devices for circuit closing under load (short circuits);

equipment for disconnection of electric current circuit in case of short circuit, limiting devices.

Relay protection and automation

The relay protection device is a circuit of the following parts:

Starting elements - voltage, current, power relays. Designed to monitor the operation mode of electrical equipment, as well as detect violations in the circuit.

Measuring elements - can also be located in starting elements (current, voltage relays). The main purpose is to start other devices, send a signal as a result of detection of abnormal operation, as well as instantaneous disconnection of devices or with a delay in time.

Logical part. It is represented by timers, as well as intermediate and pointing relays.

Executive part. Directly responsible for disconnecting or enabling switching sets.

Transmitting part. It can be used in differential phase protection.

As for the types of RPA themselves, there are many of them:

Maximum current protection (MTZ) is triggered if the current reaches the manufacturer's specified current.

Maximum current protection is directed, in addition to the installation, the power direction is controlled.

Gas protection (HZ) is used to shut off the transformer power as a result of gas release.

Differential, application - protection of busbars, transformers, as well as generators due to comparison of input and output currents. If the difference is greater than the specified setting, the relay protection is activated.

Remote (DZ), turns off power if it detects a decrease in resistance in the circuit, which happens if a DC current occurs.

Remote protection with high-frequency interlocking, used to turn off the VL when a short circuit is detected.

Remote with blocking on the optical channel, a more reliable version of the previous type of protection, since the effect of electrical interference on the optical channel is not so significant.

Logical bus protection (LPC) is also used to detect short circuit, only in this case on buses and feeders (supply lines leaving substation buses).

Arc. Purpose - protection of complete switchgears and complete transformer substations from fire. The principle of operation is based on the operation of optical sensors as a result of increased illumination, as well as pressure sensors during pressure increase.

Differential-phase (DFZ). Used for phase control at the two ends of the feed line. If the current exceeds the setting, the relay operates.

Modern RZA uses automation of the following type:

Automatic reserve entry (ATS). Such automation is often used when connecting the generator to the network, as a backup power source.

Automatic re-actuation (ACS). Field of application - power lines with voltage of 1 kV and above, as well as substation busbars, electric motors and transformers.

Automatic frequency unloading, which disables third-party devices when the frequency in the network decreases.

Analysis of existing problems

The bulk of the TP10/0.4 kV electrical equipment was commissioned in 1971. More than 30 years have passed since then. Obviously, the life of most electric receivers is coming to an end, and some have already completed it. Consequently, most of the electrical equipment is mentally and physically obsolete, which means that its energy indicators have deteriorated.

In addition to the outdated design, old devices have lower electrical and resource characteristics, as well as a constant need for revision. It is necessary to constantly ensure that mechanical parts do not coke. After switching, the main contacts must be removed and cleaned. The switching life of these devices is 10 times lower, and the shutdown time is ten times higher than that of modern ones.

For inclusion and shutdown of power electrical circuits in an operating mode (under loading), overloads and also in cases of short circuits on the line of 10 kV, the substation is equipped with the oil VMG10/630 switch which are recommended to be replaced with modern - BHP10/630.

Conclusion

As a result of writing the final qualification work, a solution to the goal was proposed - the development of a project for the reconstruction of the enterprise's power supply system.

At the initial stage of work, the facility's power supply system was analyzed, the main requirements for the designed power supply system were calculated, according to which all further calculations were made.

So, taking into account electrical loads, power transformers with a capacity of 630 kVA of the TMG series were chosen.

The compensating device will be connected to the 1SSh TP. The CV voltage must be 0.4 kV. The compensating device is a capacitor device of the UKRM type. According to the obtained value of reactive power, which requires compensation, we select the device UKRM-0.4-125, power QKY = 125 kVar, with control stages of 25 kVar, voltage 0.4kV.

For protection of the equipment in RU10 of kV the PKE1071031,540125U2 safety lock is chosen.

RPZ10/400 disconnectors are taken to the cells of supply lines to create a visible rupture when 6/0.4 kV TP is put out for repair.

The input circuit breakers are a BA8840 type switch with a 1000A disconnector current.

Busbars are selected in RU0.4kV of transformer substation - aluminum busbars with size of 60x6 mm. The long-term allowable current for 120x8 mm aluminum buses is 1900A.

Also, cable lines and circuit breakers were selected to protect the lines from RU0.4 kV to RP and from RP to electrical equipment.