变压器冷却系统设计 - 图文

内蒙古科技大学

本科生毕业设计说明书（毕业论文）

题 目：变压器冷却系统设计 学生姓名：郝燕杰 学 号：200540501310 专 业：自动化 班 级：自05-3班 指导教师：王臣

内蒙古科技大学毕业设计说明书（毕业论文）

变压器冷却系统设计

摘 要

对于现在电厂中运行的电力变压器冷却控制系统中存在的自动化程度不高、电气控制中存在的可靠性低、故障率高、控制误差大等故障以及冷却中无法达到节能这一问题，本文提出并研制了一种新型的变压器强迫油循环风冷控制装置。

系统以西门子S7－200（CPU224）型PLC 作为控制器，并控制西门子MM430变频器拖动风机和油泵电机，以此构建了变压器冷却控制系统；系统以变压器顶层油温为被控量，提出了PLC检测变频控制风机的变频器的工频信号是否到达以控制是否投入其他风扇电动机，通过检测变频控制风机的变频器的0频信号是否到达以控制是否切出其他风扇电动机的控制策略；此外装置还具有故障定位，报警显示等功能。此外，变频器的使用使冷却系统能够跟随温度的变化连续平滑调整,有利于变压器的安全运行。

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关键词：变压器；冷却控制系统；可编程序控制器；变频器；负反馈控制

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内蒙古科技大学毕业设计说明书（毕业论文）

The design of Transformer cooling system

Abstract

Nowadays, the power transformer cooling system which is running in electric power plant exists numerous problems , for instance, the low degree of automation, the low reliability, high failure rate in electrical control, the large control errors, as well as energy-inefficient cooling control , all the thorny issues mentioned above can not meet the modern control requirements , this dissertation proposed and developed a new type of system called forcing transformer oil circulation and cooling by air system.

This system used Siemens S7-200(CPU224)-based PLC as the controller, moreover, it also controlled Siemens MM430 frequency converter to drag fan and pump motor, which could be regarded as building a transformer cooling control system. This system considered the top-level temperature of transformer oil as controlled variable, the dissertation simultaneously put forward the control strategy that letting PLC detect industrial frequency access signal coming from the frequency converter which drag fan motor in order to control whether or not putting into operation of other fan motors; next, letting PLC detect zero frequency access signal coming from the frequency converter which drag fan motor in order to control whether or not ceasing other fan motors; in addition , the system comprised the function of fault location and alarm display. Last, the utilization of frequency convertor can make the cooling system always keep pace with changes of temperature for a smooth adjustment, which is conducive to the safe operation of the transformer.

Key words: Transformer; Cooling control system; PLC; Frequency converter;

Negative feedback control

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内蒙古科技大学毕业设计说明书（毕业论文）

目录

摘 要............................................................................................................................ I Abstract ......................................................................................................................... II 目录.............................................................................................................................. III 第一章 引言.............................................................................................................. 1

1.1电厂变压器冷却系统设计背景....................................................................... 1 1.2系统的工艺流程及冷却装置简介 ........................................................................... 2

1.2.1变压器散热方式..................................................................................... 2 1.2.2变压器冷却原理..................................................................................... 3 1.2.3.冷却系统简介......................................................................................... 3 1.3 冷却系统的技术目标...................................................................................... 5 1.4 本章小节.......................................................................................................... 5 第二章 系统的控制方法和方案设计.......................................................................... 7

2.1 电力变压器运行规程中关于冷却控制的规定.............................................. 7

2.1.1 对变压器的冷却装置的要求................................................................ 7 2.1.2 变压器温度限值.................................................................................... 7 2.1.3 强迫油循环冷却变压器的运行条件.................................................... 7 2.2变压器油温自动控制的控制方法................................................................... 8

2.2.1综合投、切控制策略............................................................................. 8 2.2.2 PLC变频控制的基本原理 .................................................................... 9 2.2.3 PLC变频控制的PID参数整定 ............................................................ 9 2.2.4 变压器冷却自动控制系统框图.......................................................... 12 2.3 系统组成........................................................................................................ 13 2.4本章小结......................................................................................................... 15 第三章 冷却控制装置的硬件设计.......................................................................... 16

3.1 开关器件的选择............................................................................................ 16

3.1.1 继电器的选择...................................................................................... 16 3.1.2 接触器的选择...................................................................................... 16

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