A substation is part of an electrical distribution system that transforms voltage from high to low levels or vice versa. There are four main types: generating station switchyards, customer substations for large customers, system substations that transfer bulk power, and distribution substations that directly supply most customers. Substations contain equipment like transformers, circuit breakers, and bus bars arranged in different configurations depending on factors like system voltage and flexibility needs.

2.  What is substation?
 Equipment used in substation.
 Type of substation.
 Bus bars arrangement in substation

3.  A substation is a part of an
electrical generation, transmission, and distribution system.
 Substations transform voltage from high to low, or the
reverse, or perform any of several other important functions.
Between the generating station and consumer.
 Electric power may flow through several substations at
different voltage levels. A substation may
include transformers to change voltage levels between high
transmission voltages and lower distribution voltages, or at
the interconnection of two different transmission voltages.

4.  The substation is an assembly of the following major electrical
equipments:
1. Electrical Power transformers.
2. Instrument transformer
3. Conductors & Insulators.
4. Isolators.
5. Bus bars.
6. Lightning arresters.
7. Circuit breakers.
8. Relays.
9. Miscellaneous equipment

5.  There are four major types of electric substations.
1. switchyard at a generating station
2. customer substation
3. system sub station
4. distribution sub station

6. 1. Generating Station Switchyards
 The first type is the switchyard at a generating station.
These facilities connect the generators to the utility grid
and also provide off-site power to the plant.
 Generator switchyards tend to be large installations that
are typically engineered and constructed by the power
plant designers and are subject to planning, finance, and
construction efforts different from those of routine
substation projects.
 Because of their special nature, the creation of power plant
switchyards will not be discussed here, but the expansion
and modifications of these facilities generally follow the
same processes as system stations.

7. Customer Substations
 The second type of substation, typically known as the customer
substation, functions as the main source of electric power supply for
one particular business customer.
The technical requirements and the business case for this type of
facility depend highly on the customer’s requirements, more so than
on utility needs.
System Substations
 The third type of substation involves the transfer of bulk power
across the network and is referred to as a system station. Some of
these stations provide only switching facilities (no power
transformers) whereas others perform voltage conversion as well.
 These large stations typically serve as the end points for transmission
lines originating from generating switchyards and provide the
electrical power for circuits that feed transformer stations.

8. Distribution Substation
 The fourth type of substation is the distribution station. These
are the most common facilities in power electric systems and
provide the distribution circuits that directly supply most
electric customers.
 They are typically located close to the load centres, meaning
that they are usually located in or near the neighborhoods that
they supply, and are the stations most likely to be encountered
by the customers.
 Depending on the type of equipment used, the substations
could be
◦ Outdoor type with air-insulated equipment
◦ Indoor type with air-insulated equipment
◦ Outdoor type with gas-insulated equipment
◦ Indoor type with gas-insulated equipment
◦ Mixed technology substations
◦ Mobile substations

9.  There are many different electrical bus system schemes
available but selection of a particular scheme depends upon
the system voltage, position of substation in electrical
power system, flexibility needed in system and cost to be
expensed.
a) Single bus bars system
b) Single bus bars system with Bus Sectionalize
c) Double breaker Bus bars
d) Main and Transfer Bus bars system

10.  Simplicity of system.
 Easy maintenance of different equipments.
 Minimizing the outage during maintenance.
 Future provision of extension with growth of demand.
 Optimizing the selection of bus bar arrangement scheme so
that it gives maximum return from the system.

11.  ingle Bus System is simplest and cheapest one. In this scheme
all the feeders and transformer bay are connected to only one
single bus as show.

12.  Advantages of Single Bus System
 This is very simple in design.
 This is very cost effective scheme.
 This is very convenient to operate.
Disadvantages of Single Bus System
 One but major difficulty of these type of arrangement is
that, maintenance of equipment of any bay cannot be
possible without interrupting the feeder or transformer
connected to that bay.
 The indoor 11 KV switchboards have quite often single bus
bar arrangement.

13.  Some advantages are realized if a single bus bar is
sectionalized with circuit breaker. If there are more than one
incoming and the incoming sources and outgoing feeders are
evenly distributed on the sections as shown in the figure,
interruption of system can be reduced to a good extent.

14. Advantages of Single Bus System with Bus Sectionalize
 If any of the sources is out of system, still all loads can be fed
by switching on the sectional circuit breaker or bus coupler
breaker.
 If one section of the bus bar system is under maintenance, part
load of the substation can be fed by energizing the other
section of bus bar.
Disadvantages of Single Bus System with Bus Sectionalize
 As in the case of single bus system, maintenance of equipment
of any bay cannot be possible without interrupting the feeder or
transformer connected to that bay.
 The use of isolator for bus sectionalizing does not full fill the
purpose. The isolators have to be operated ‘off circuit’ and
which is not possible without total interruption of bus – bar. So
investment for bus-coupler breaker is required.

15.  In double bus bar system two identical bus bars are used in
such a way that any outgoing or incoming feeder can be taken
from any of the bus.
 Actually every feeder is connected to both of the buses in
parallel through individual isolator as shown in the figure.

16. Advantages of Double Bus System
 Double Bus Bar Arrangement increases the flexibility of
system.
Disadvantages of Double Bus System
 The arrangement does not permit breaker maintenance
with out interruption.

17.  This is an alternative of double bus system. The main
conception of Main and Transfer Bus System is, here every
feeder line is directly connected through an isolator to a
second bus called transfer bus.
 The main bus is as usual connected to each feeder through a
bay consists of circuit breaker and associated isolators at both
side of the breaker.
 There is one bus coupler bay which couples transfer bus and
main bus through a circuit breaker and associated isolators at
both sides of the breaker.

18. Single line diagram