ENGLISH FOR INDUSTRIAL
ELECTROTECHNOLOGY
STUDENTS
Department of JUBE
IESTP JOSE CARLOS MARIATEGUI
MOQUEGUA
English Teacher: Yenny Geyddy Gutierrez Machaca
Chapter 1
Substations
Overview
 Basic terminology

Major equipments in a substation
3
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Transformers
Circuit breakers
Air disconnect switches
Lightning arresters
Electrical buses
Capacitor banks
Reactors
Static VAR compensators
Control building
Transformer: Boost or Decrease voltage
4
Transformer - Details
5
2. Magnetic Core
7. Radiator
8. Windings
10. Load Tap Changer (LTC)
On-load Tap Changer (OLTC)
Transformer Cooling Methods
6

Air Cooling For Dry Type Transformers:
Air natural Type (A.N.)
Air Forced type (A.F.)

Cooling For Oil Immersed Transformers:
Oil Natural Air Natural Type (O.N.A.N.)
Oil Natural Air Forced Type (O.N.A.F.)
Oil Forced Air Natural Type (O.F.A.N.)
Oil Forced Air Forced Type (O.F.A.F.)

Oil immersed Water Cooling:
Oil Natural Water Forced (O.N.W.F.)
Oil Forced Water Forced (O.F.W.F.)
Transformer Cooling Methods
7

Air Cooling For Dry Type Transformers:
Air natural Type (A.N.): transformer is cooled by nature surrounding
air.
Air Forced type (A.F.): air is forced on to the tank surface to increase
the rate of heat dissipation.
Apply for dry type transformer
A dry type transformer is one which does not employ a liquid as a
cooling or insulating medium.
Transformer Cooling Methods
8
Tap Changing System
9

Insulation requirements: tap points is placed at the low voltage
end of the winding:
Near the star point in a star connected winding.
 In delta connected windings: the tapings are usually at the center of
the winding.
Tap Changing System
10
On-load Tap Changer Mechanism
Tap Changing System
11

Switching sequence
Tap Changer - Fitted
12
Tap
changer
External
control box
Other type of transformer: Autotransformer
13

In an autotransformer:
A portions of the same winding act as both
the primary and secondary: common
winding.

An autotransformer:
Smaller size
Lighter & cheaper

However: does not provide electrical
isolation.
Transformer - Bushings
14


Bushings are used on transformers, circuit breakers... as
connection points
Bushings connect outside conductors to conductors inside
equipments
Transformer – Bushings CTs Location
15
Bushing CT
Circuit Breaker
16


Switchgear: combination of electrical disconnects, fuses and/or
circuit breakers used to isolate electrical equipment.
Switchgear: used both to:
De-energize equipment to allow work to be done
To clear faults downstream.
Type of Circuit Breaker – Based on Interrupting Media
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Bulk Oil Circuit Breakers (BOCBs)
Minimum Oil Circuit Breakers (MOCBs)
Air Circuit Breakers (ACBs)
Air Blast Circuit Breakers (ABCBs)
SF6 Gas Circuit Breakers
Vacuum Circuit Breakers (VCBs)
Type of Circuit Breaker – Based on Interrupting Media
18

Bulk Oil Circuit Breakers (BOCBs)
Contacts is immersed in oil
Oil as insulation: live part & earthed metal tank
Type of Circuit Breaker – Based on Interrupting Media
19

Minimum Oil Circuit Breakers (MOCBs) (low oil)
Use oil as interrupting media
Interrupting unit in insulating chamber at live potential  reduce
requirement of oil
Type of Circuit Breaker – Based on Interrupting Media
20

Air Circuit Breakers (ACBs)
Contacts open & close in air at atmospheric pressure
Normally, apply for low voltage system only
Type of Circuit Breaker – Based on Interrupting Media
21
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Air Blast Circuit Breakers (ABCBs)
Type of Circuit Breaker – Based on Interrupting Media
22
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Air Blast Circuit Breakers (ABCBs)
Type of Circuit Breaker – Based on Interrupting Media
23
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
SF6 Gas Circuit Breakers
Contacts open & close in Sulphur Hexafluoride (SF6)
Type of Circuit Breaker – Based on Interrupting Media
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Advantages over oil and air circuit
breakers:

Due to property of SF6 : very short
arcing time

Dielectric strength of SF6 gas is 2 to 3
times that of air  can interrupt much
larger currents.

Noiseless operation due to its closed
gas circuit

No risk of fire as SF6 is non
inflammable
Low maintenance cost, light
foundation requirements and
minimum auxiliary equipment

Disadvantages:

SF6 breakers are costly due
to high cost of SF6
Type of Circuit Breaker – Based on Interrupting Media
25

SF6 Gas Circuit Breakers
Type of Circuit Breaker – Based on Interrupting Media
26

SF6 Gas Circuit Breakers
Type of Circuit Breaker – Based on Interrupting Media
27

Vacuum Circuit Breakers (VCBs)
Arc interruption takes place in vacuum
Type of Circuit Breaker – Based on Interrupting Media
28

Vacuum Circuit Breakers (VCBs)
Arc interruption takes place in vacuum
Type of Circuit Breaker – Based on Interrupting Media
29

Vacuum Circuit Breakers (VCBs)
Arc interruption takes place in vacuum
Air Disconnect Switches - Isolator
30
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Isolate or de-energize equipment for maintenance purposes
(isolator)
Transfer load from one source to another in planned or
emergency conditions
Provide visual openings for maintenance personnel
Being normally gang operated (or group operated)
Have low current interrupting ratings compared to circuit
breaker
Air Disconnect Switches - Types
31

Vertical break type
Air Disconnect Switches - Types
32

Horizontal break type
Air Disconnect Switches - Types
33

Operating Mechanism
Lightning Arrester
34

Designed to limit the L-G voltage in the event of lightning or
other excessive transient voltages
For substation
Lightning Arrester
35

Designed to limit the L-G voltage in the event of lightning or
other excessive transient voltages
For lines
36