Today, we will explain the following:
- Voltage Regulators Data,
- Transformers Data,
- Switchgear data.
|
Interpreting Single-Line
Diagram – Part Two
|
|
The interpretation of single-line diagrams
is explained in this section under the following major subject headings:
|
|
D.1- Informational Elements
The following informational elements of a single-line
diagram are explained in this section:
|
|
We will use the below single-line diagram throughout these articles
for explaining how to interpret this type of electrical diagrams. You can
download a PDF copy of this single-line diagram by following the link.
Fig.1
|
|
D.1.4 Voltage Regulators Data
|
Function:
The automatic voltage regulator (AVR) is a device designed to regulate voltage automatically – that is, to take a fluctuating voltage level and turn it into a constant voltage level
Why would we
need a voltage Regulator?
Variation of
voltage can have detrimental effects on Utilities and their customers so; we
use AVR to prevent customer complaints, loss of revenue due to sub-normal
voltage, and increased costs due to higher line losses.
Types:
The difference in their operation and design clearly demonstrate that their applications are not the same as follows:
AVR Regulation range
AVR units connection Arrangements with supply and loads:
Automatic voltage regulators can be
designed for single-phase or three-phase AC applications as per the following
arrangements:
A- Single phase AVR with 3-phase Supply& Three
phase Loads
It is common for utilities to use single
phase automatic voltage regulators ganged together to provide voltage
regulation for three phase. These are often “can-type” units pole-mounted
outdoors.
B- Single phase AVR with 3-phase Supply &
single phase Loads
Single
phase automatic voltage regulators may also be used where a three phase
source is used to supply three single phase loads.
C- Three phase AVR with 3-phase Supply &
single phase Loads
Most three
phase AVRs may also be used to feed single phase loads.
Notes:
Single phase
AVR units power connection
The single
phase AVR units can be connected as a single phase or 3- phase circuit as per
the following connection diagram:
3 nos. of single
phase AVR units can be connected as Delta or Y bank as shown in the above connection
diagram.
Notes:
AVR data:
On Fig.1, the following information is noted:
|
D.1.5 Transformers Data |
Function:
A transformer is a device that converts electrical power in an AC system from one voltage or current into another voltage or current.
Principle of operation:
Method of classifications:
Transformers are identified with symbols according to their function as per the above figure and are classified according to:
For more information about transformer construction, classifications and types, please review our course “EP-3: Electrical Procurement – Transformers Course”
Where the following topics were/will be explained:
Power Transformer Data
For each power transformer symbol that appears on a one-line diagram, the following information is printed next to the symbol:
On the below Figure, the following information is noted:
On the below Figure, the following information is noted:
|
D.1.6 Switchgear data |
|
Definition:
Switchgear is a
generic term. The industry uses it to cover “assemblies of switching and
interrupting devices, along with control, metering, protective and regulating
equipment.”
Function:
Types:
Switchgear can
be divided to many types according to many classification factors like these
included in the below image.
The most
important classifications are as follows::
1- According To
Their Voltage Level:
2- According To
Their Location:
3- According To
Their Function:
|
|
Construction
of Switchgear
First: Medium
Voltage Switchgear
A typical medium
voltage switchgear assembly has:
Metal-Clad vs. Metal-Enclosed Medium Voltage Switchgear
|
|
Second:
Low Voltage Switchgear
The
low voltage switchgear can all be used as service entrance electrical
distribution equipment or as a load
center or that is feeding power to a number of smaller circuits. It is
divided to:
|
|
1- Switchgear
Low
voltage switchgear provides centralized control and protection of low voltage
power equipment and circuits in industrial, commercial and utility
installations involving transformers, generators, motors and power feeder
circuits.
Low
voltage switchgear features the following components:
Switchgear
is generally installed at the highest level of the power system. Cables or
conduits can be used to feed power from the switchgear into other
switchboards, panelboards or main loads.
|
|
2- Switchboards
For
larger scale buildings or sites, a large single panel, frame, or assembly of
panels can be used for mounting the overcurrent switches and protective
devices, buses and other equipment. These floor-mounted, freestanding solutions
are known as switchboards. Switchboards are most often accessible from the
front, mounted on the floor and close to the wall.
The
primary components of a switchboard include:
There
are four main structure types common to all switchboards, but all
switchboards do not use all of these structure types:
A- The
Main Switchboards Structure:
It contains
the main disconnects or main lugs. It often contains surge protection, utility
and/or customer metering equipment.
B- The
Pull Structure:
It
is a blank enclosure containing empty space through which cabling can be pulled.
It is commonly used with service entrance switchboards where the utility feed
comes through the floor. Service can be fed from the top without any exposed
conductors.
C- A
Distribution Structure:
It divides
and sends power to branch circuit protection devices and then to branch
circuits to power downstream loads. Power moves from the incoming structure to
the distribution structure via cross bus.
D- The
Integrated Facility System (IFS) Switchboard Structure:
It
includes panelboards, dry-type transformers, transfer switches and blank back
pans for field mounting other equipment. The IFS is helpful when panelboards
and dry-type transformers are used in the same room as switchboards as it can
reduce the need for linear wall space and area required for equipment. A key benefit
of the IFS is that it significantly reduces the installation and wiring time
and the number of pieces of equipment to be handled.
|
|
3- Panelboards
A
panelboard is a component of an electrical distribution system that divides
an electrical power feed into branch circuits while providing a protective
fuse or circuit breaker for each circuit in a common enclosure. In essence,
panelboards are used to protect against electrical overloads and short
circuits while distributing electricity throughout a building or facility.
The
main components of a panelboard typically include:
Panelboards
can be installed using one of two common approaches; flush mounted or surface
mounted. When flush mounted, the panelboard is placed in a recessed area between
the wall studs. When surface mounted, the panelboard projects out from the
wall.
Panelboards
are often categorized by their general application to:
Lighting and appliance panelboards contain overcurrent protection and
a means to disconnect lighting, appliances, receptacles and other small load
circuits. All other panelboards are used for power and may also feed other
panels, motors and transformers in the building’s or site’s overall power
distribution systems.
|
|
Switchgear
Rating Data
The switchgear
rating data that must appear on the Single-Line diagram will be as follows:
In our example,
the following data are provided for Low voltage switchgear MCDS:
|
As per the above switchgear definition,
it can be break up to different parts as follows:
- “Control devices” check and/or regulate the flow of power.
- “Switching and interrupting devices” are used to turn power on or off.
- “Metering devices” are used to measure the flow of electric power.
- “Protective devices” are used to protect power service from interruption, and to prevent or limit damage to equipment.
In the next article, we will explain the data
required on a single lie diagram for each switchgear part from the above list. So,
please keep following.
The
previous and related articles are listed in the below table:
|
Subject
of Previous Article
|
Article
|
|
1- Overview for the articles/courses that give a preliminary explanation for the different Types of
Electrical drawings.
2-
Electrical Drawings Glossary.
|
|
|
3- Resources used to Read and Interpret Electrical Drawings.
|
|
|
4-
Electrical Symbols and Abbreviations
5-
Electrical Abbreviations
6- Device
Function Numbers
7-
Drafting Practices Using Graphical Symbols and abbreviations
|
|
|
8- Basic Elements of Electrical Drawings 9- Types of Electrical Drawings 9.1- Electrical Diagrams 9.1.1- Single-Line /One-Line Diagram A- Characteristics of Single-Line Diagram B- Purposes of Single-Line Diagram C- Arrangement of Components on Single-line Diagrams D- Interpreting Single-Line Diagrams D.1- Informational Elements D.1.1 Point of Connection to the Utility Company D.1.2 Identification of buses, substations, generators, motors and other equipment D.1.3 Ring Main Units data |
|
|
Back To
Electrical
Shop Drawings Course
|
No comments:
Post a Comment