High-Tension (HT) substations play a pivotal role in electricity transmission, serving as crucial nodes in power distribution networks. These substations step up voltages for efficient long-distance transmission and step them down for local distribution. Through state-of-the-art equipment and meticulous maintenance, HT substations ensure reliable and uninterrupted power supply to meet the growing energy demands of modern society.

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Introduction to HT Substation

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Agenda
1. Introduction
2. Single Line Diagram/Circuit Configuration
3. Safety
4. References

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HT means voltage ranges from 11 KV and
above which has allowable variation +6% and
-9%.
HT substation are points in the power system
where power can be pooled from generating
sources, distributed and transformed, and
delivered to the load points.
1. Introduction

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The key steps in the substation designing include switching-system, Planning
and placing of equipment, selection of components as well as ordering, support
of engineers, structural design, the design of electrical layout, protection of relay
, and major apparatus ratings.

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The HT substation is composed of the following equipment and devices:
1. Power Transformer
2. Instrument Transformer
3. Protective Relay
4. Power Fuses
5. Circuit Breaker
6. Busbar
7. Disconnecting Switch
8. Lightning arrestor
5

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The main purpose of this is to step-up the
transmission voltage at the generation unit &
step-down the transmission voltage at the
distribution unit. Generally, for rating up to
10MVA (Mega-volt-Amperes) oil immersed,
naturally cooled and 3-phase transformers are
used. Similarly, for more than 10MVA (Mega-
volt-Amperes), air blast cooled transformers
are used.
1.1 Power Transformer:

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The main purpose of an instrument transformer is to decrease high current as well as
voltages for a secure & realistic value. These values can be calculated with
conventional devices. This transformer is also used for triggering the protective relay
(AC type) by providing the current as well as voltage. These are classified into two
types namely a voltage transformer and a current transformer.
A. Voltage Transformer (VT) or Potential Transformer (PT)
Voltage transformers are used mainly in high-voltage distribution equipment to step-
down voltage in measurement circuit for safe measurement; single-phase and three-
phase types are manufactured.
B. Current Transformer (CT)
Current transformers are used for stepping down current to be measured safely. It is
also applied to protective relays. The typical secondary current of the current
transformer is 5 Amp or 1 Amp.
1.2 Instrument Transformer:

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Protective relays should detect electrical faults promptly, isolate the faults from system
and activate alarms when there is a faulty condition sensed in the electrical supply to
the circuits or electrical equipment (short circuit, earth fault, single-phase, reverse
power flow etc.)
1.3 Protective Relay:

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Circuit breakers are Switches that open/close electric-circuits in normal and
abnormal conditions (especially in short circuit). Circuit breakers for high voltage
are categorized into the following types according to their techniques of
eliminating arcs:
A. Air Circuit Breakers (ACB)
B. Vacuum Circuit Breaker (VCB)
C. Inert Gas Method (SF6)
1.4 Circuit Breaker:

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The function of a power fuse is to sense and prevent flow of excess current in electrical
devices and electrical wire by melting the fuse element and thereby breaking the
electric circuit when subjected to a short-circuit.
1.5 Power Fuses:

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The bus bar is a very important component in an electrical substation. It is a kind of
current carrying conductor where many connections are made. In other terms, it can be
defined as it is one type of electrical connection where the incoming current and
outgoing current take place.
1.6 Bus Bar:

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Disconnecting switches are devices to open/close a high voltage circuit when high-
voltage equipment are inspected, tested or cleaned. The devices are capable of safely
breaking no-load current but not load current.
1.7 Disconnecting Switch:

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This is the first component in an electrical substation, and the main function of these
components is to protect the components of the substation from passing high voltage as
well as stops the amplitude and duration of the flow of current. The light arrestor
components are connected among the earth as well as a line which mean parallel to the
components under defense at the electrical substation.
1.8 Lighting Arrester:

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The single line diagram makes the
system easy, and it provides the
facilitates reading of the electrical supply
and connection.
The high voltage substation is critical
component in the power system, and
the reliability of the power system
depends upon the substation. Therefore,
the circuit configuration of the high
Voltage substation must be selected
carefully.
2. Single Lien Diagram/Circuit Configuration:

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Safety is one the major issue in HT SUBSATION. Safety practices stem out of common
sense and practical learning. Important safety measures that can minimize high-risk
security threats commonly encountered in substations.
Securing Perimeter Area
Restricting or Prohibiting Visitor Access
Monitoring/ Guiding Vehicular Traffic
Prohibiting Equipment Storage
Securing Battery Stores
Training Personnel
Installing Security Equipment etc.
3. Safety :

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1) Article written by Mr. Vignesh
2) SIEMENS Substations Guide Andreas Goutis, ‘Electrical drawing, Part 1’
3) https://electrical-engineering-portal.com/high-voltage-substations-overview-1
4) https://circuitglobe.com/single-line-diagram-of-11kv-substation
5) https://www.substation-safety.com/latest-news/safety-practices-substations/
4. Referenec:

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We deliver End-to-End Engineering Design and Construction Management
Projects in Food and Beverage Industry.
Meeting Global Benchmarks
In ENGINEERING DESIGN and PROJECT MANAGEMENT
for FOOD and BEVERAGE Industry with SINGLE POINT ACCOUNTABILITY
Process Engineering | Project Management | Mechanical | Electrical | Automation | Food Safety
Key Clients
We deliver End-to-End Engineering Design and Construction Management
Projects in Food and Beverage Industry.
Meeting Global Benchmarks
In ENGINEERING DESIGN and PROJECT MANAGEMENT
for FOOD and BEVERAGE Industry with SINGLE POINT ACCOUNTABILITY
Process Engineering | Project Management | Mechanical | Electrical | Automation | Food Safety
Key Clients
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