Save 50% on all EEP Academy courses with Enterprise Membership Plan and study specialized LV/MV/HV technical articles & guides.

# Substation Design Guidelines

## Consider open loop MV network as an example

The rating of substation equipment as well as the connections must be decided.

### Selection of substation equipment

#### Switchgear

1. Selection of transformers
2. Ratings of circuit breakers
3. Ratings of switch disconnecters (Load-break switches)
4. Ratings of isolators (Disconnecters)

#### Measurement

1. Characteristics of voltage transformers (VTs)
2. Characteristics of current transformers (CTs)

### Selection of Transformers

1. Transformer size/s must be selected according to the maximum expected load and possibility of future expansions.
2. The size of transformer may be selected from power ratings given below to supply present and future loads.

### Commonly available ratings for substation transformers

Rated powers:

25 kVA, 50 kVA, 100 kVA, 250 kVA, 400 kVA, 630 kVA, 800 kVA, 1000 kVA, 1250 kVA, 1600 kVA, 2000 kVA

Primary voltages (line-to-line):

6 kV, 7.2 kV, 10 kV, 12 kV, 22 kV, 24 kV, 31.5 kV, 33 kV, 34.5 kV, 35 kV, 36 kV

Secondary voltages (line-to-line): 380 V, 400 V

## Example:

### Substation Design

Consider that you would like to choose a transformer to supply power to a factory which requires maximum of 270 kVA of power at 400 V on the LV side and no expension is considered for near future.

The power will be provided by connecting the factory to 33 kV MV voltage level. Choose the transformer.

### Solution:

Powers:

25 kVA, 50 kVA, 100 kVA, 250 kVA, 400 kVA, 630 kVA, 800 kVA, 1000 kVA, 1250 kVA, 1600 kVA, 2000 kVA

Primary Voltages (line-to-line): 6 kV, 7.2 kV, 10 kV, 12 kV, 22 kV, 24 kV, 31.5 kV, 33 kV, 34.5 kV, 35 kV, 36 kV

Secondary Voltages (line-to-line): 380 V, 400 V

Selected transformer size for the factory:

400 kVA, 33 kV/400 V

50% Discount 💥 - Save 50% on all 90+ video courses with Enterprise Membership plan.

1. Charlotte Fleet
Jan 27, 2023

Thanks for your explanation of how you should select a transformer for your substation based on the maximum expected load. I imagine that it would be beneficial to hire a high-voltage electrician to help with transformer selection. That way, you can use their expertise and experience to determine the best option.

2. Peter McCoy
Jul 20, 2022

some interesting points and good articles.

3. SAM
Apr 06, 2022

wish to know the space requirement for 1600kva and 2000kva to design substation

4. ELISIO JANEIRO
Sep 09, 2020

I like so.much this site.

5. Louis.Low
Dec 31, 2018

That’s really comprehensive

6. Leninkumar
Nov 01, 2018

Can you please share the detailed specification of double pole structure substation?

7. Herman makaya
Nov 09, 2017

I need to purchase an electrical substation isolated in 24 kV with a tfo intention 20/6,6/0,4 kV 500 kva 3 cellules MT + cellule of counting MT .side BT: TGBT with DGBT 800 .Disjonctor BT adjustable :160 to 250 A

8. Subodha Ranaweera
Jan 13, 2015

Can i have the design details of closed ring operated MV network?

9. ADOLFO PONCE DE LEON PE
Jul 05, 2014

SWBD APPEARS TO BE INDOOR. TRNS CAN NOT BE OIL OR AN EXPENSIVE VAULT WILL BE REQUIRED IF IS LOAD CENTER THE TFRM WILL HAVE TO BE DRY, DIFFERENT TYPES,. ASSUMED THE SYSTEM FREQUENCY IS 50 HERTZ. IF DRAW OUT BREAKERS
ASSUMED NOT POWER BREAKERS, PROBABLY INSULATED CASE. A DECISION WILL HAVE TO BE MADE FOR THE CLEARANCE IN FRONT OF THE SWITCHBOARDS. INDICATE UNITS, METRIC, OR ENGLISH TO ESTABLISH IF THE COUNTRY HAVE AN ELECTRICAL CODE.I ILL STOP HEAR.
THANKS AND REGARDS