Transmission & Distribution Program

Introduction to Substation DesignTADP 542

Introduction

Instructor: Mike Nissley

Module 1 Outline

Presentation 1: General System Overview

Presentation 2: Definitions

Presentation 3: Components

Presentation 4: Components (cont.)

Presentation 5: Utilization of Substation Equipment and Glossary

General System Overview

Generation Systems– Fuels & Philosophy

Transmission Systems– Voltages & Fundamentals

Distribution Components– Fundamentals & Utilization

Generation Types

Thermal Generation: Burns fuel to create heat which either boils

water for steam (to spin a turbine), or burns to directly spin a generator.

Nonthermal Generation: Fuel mechanically powers a turbine to generate

electricity.

Thermal Generation

Nuclear, coal, diesel, natural gas, landfill gas, and biomass are considered thermal fuel resources.

Thermal resources characterized by fuel consumption and associated generation of heat and waste by-products.

Natural Gas Fired Plant

Thermal Power Plant

Nonthermal Generation

Hydro, wind, solar, and wave energy are considered nonthermal fuel sources.

Nonthermal fuels are characterized by the fact that the fuel that enters the generator system leaves it unaltered -using mechanical methods to generate electricity.

Hoover Dam

Box Canyon Dam

Renewable Fuels

Renewable fuels are not easily classified, with many states developing their own definition. For example, some states consider landfill gas as renewable because it uses a by-product of a waste stream to generate electricity even though the waste stream itself is not renewable in the natural sense.

Stateline Wind Farm

Generation Size & Role

Plants can range in size from 0.25 MW’s to over 2000 MW’s.

Size determined by individual utility needs and operational efficiencies gained by appropriately sizing the plant.

Base Load plants provide constant power output to meet minimum needs.

Peaking Plants vary power output to follow load.

Transmission System

Used to transport large quantities of electricity efficiently over long distances.

Operates at very high voltages (as high as 750 kV) to reduce line losses associated with current flow.– As current increases the energy dissipated as

heat due to conductor line resistance increases.

Transmission Rule of Thumb

Calculating transmission voltage efficiency:

– Generally; 10 MW of electricity can be transported 10 Miles for every 10 kV.

– Example: A 115 kV line could efficiently move 115 MW of energy approximately 115 miles.

AC vs DC

Transmission lines typically operate with AC due to its low operating costs. However, there are situations where DC may be a better solution.

DC lines have lower line losses and therefore are most efficient at distances in excess of 500 miles (verify).

Transmission Costs

Higher voltage lines are more expensive per mile.

– Typical 115-kV line on wood poles approximately$250,000/mile.

– Typical 345-kV line on lattice steel in excess of $1,000,000/mile

A Substation with a View

Distribution Voltages

Primary voltages can range from 2 - 50 kV

Typical voltage classes are 15 kV (12.47 kV, 13.2 kV, or 13.8 kV) and 25 kV. The different values have a lot of history behind them.

Secondary voltages are 120/240 V for residential, and 120/208 V or 480 V for commercial.

Distribution Construction

Can be overhead or underground.

Includes components for transformation of voltage, regulation of voltage, protection from overvoltage excursions, and isolation of faults.

Distribution Customer Classes

Residential – single or multi-family housing regardless of size.

Small Commercial – less than 50 kW and single phase.

Large Commercial – larger than 50 kW and possibly three-phase

Industrial – Usually in excess of 3000 kW

Irrigation – Can be divided by size

Load Types

Heating/Cooling/Refrigeration – typically simple motor loads

Lighting/Cooking – Typically resistive load

Manufacturing/Irrigation – can be simple motors or variable frequency drives (non-linear)

Each load type has different electrical characteristics

Project Scope

Who is the customer?– Organizations receiving electrical service from a

Substation

What is the scope of a project?– Function, location, etc.

Purpose of a Project Scope: – Communication