Types of Electrical Substations | A Complete Introduction to Transmission, Sub-Transmission, Distribution, and Building Substations

Subject: Electrical Substation — suitable for electrical engineers, contractors, and students"

An electrical substation is one of the most important components of the power transmission and distribution network. The primary function of substations is voltage transformation, protection, control, and reliable distribution of electrical energy. In this article, we provide a comprehensive and technical yet easy-to-understand explanation all types of electrical substations while examining the differences, equipment, and applications of each type.

Table of Contents

What is an Electrical Substation?

An electrical substation is a facility where the following operations are performed:

  • Voltage Transformation (Step-Up / Step-Down)
  • Distribution of Electricity to Different Lines"
  • کنترل و مانیتورینگ شبکه
  • Equipment Protection Against Faults

Key equipment in substations includes Transformer، Power Switchgear، Isolator and Protective Relays are included.

Types of Electrical Substations by Voltage Level

Low Voltage (LV) Substation

Voltage: 230/400 V — Application: Buildings and residential consumers.

Medium Voltage (MV) Substation

Voltage: Approximately 6 to 33 kV — Application: Urban distribution, factories, and kiosk substations.

High Voltage (HV) Substation

Voltage: 63 to 132 kV — Function: Step down voltage from transmission to distribution networks."

Extra High Voltage (EHV) Substation

Voltage: 230, 400 kV and above — Used in the national grid and for connecting power plants.

Types of Electrical Substations by Structure and Equipment

AIS — Air-Insulated Substation

Equipment is installed outdoors. Advantage: lower cost and easy maintenance. Disadvantages: requires more space and is sensitive to environmental pollution.

GIS — Gas-Insulated Substation

Equipment is housed in SF6 gas-filled enclosures. Advantages: requires less space, suitable for urban environments, and offers high safety; Disadvantages: higher cost and requires specialized maintenance.

Types of Electrical Substations by Installation Location

Ground-Mounted Substation

The most common type; requires dedicated space and proper foundation.

Compact / Kiosk Substation

Prefabricated and suitable for urban areas and projects with limited space; allows for quick and safe installation.

Building-Mounted Substation (Indoor)

Suitable for complexes, high-rise buildings, and hospitals; typically includes transformers and MV/LV panels indoors.

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  • تابلو فشار متوسط (RMU یا تابلو جداکننده)
  • تابلو فشار ضعیف
  • سیستم ارت و حفاظت

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Compact (Kiosk) Substation

A compact substation is a prefabricated room or enclosure containing transformers, panels, and control systems, designed for installation in urban or industrial spaces. Its advantages include quick installation, minimal space usage, and adequate protection against environmental conditions.

Main Equipment of Different Types of Electrical Substations

  • Power Transformer
  • Power Switchgear (Circuit Breaker)
  • Isolator and Sectioning
  • Protective Relays
  • Busbar
  • CT and PT (Current and Voltage Transformers)
  • MV and LV Panels
  • Grounding and Lightning Protection System

Comparison Table of Different Types of Electrical Substations

نوع پستسطح ولتاژمحل نصبهزینهکاربرد
انتقال230–400 kVزمینیزیادشبکه سراسری
فوق‌توزیع63–132 kVهوایی / زمینیمتوسطتغذیه پست‌های توزیع
توزیع6–33 kVزمینی / هواییکممصرف‌کننده‌ها
GIS20–400 kVداخل ساختمانزیادمناطق شهری با فضای محدود
کمپکت20 kVپیش‌ساختهمتوسطپروژه‌های کوچک و شهری

Frequently Asked Questions (FAQ)

What is an Electrical Substation?

A facility for voltage level conversion and network protection, which includes transformers, switchgear, protective relays, and panels.

What is the difference between GIS and AIS substations?

GIS دارای تجهیزات داخل محفظه گازی و مناسب فضای محدود است؛ AIS روباز و اقتصادی‌تر ولی فضای بیشتری لازم دارد.

What is a Kiosk Substation?

یک پست پیش‌ساخته و کامپکت که شامل ترانس و تابلوها داخل یک کیوسک آماده است و مناسب مناطق شهری و کارخانجات است.

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