How to Select Automatic Voltage Regulator (AVR) for Power Distribution System?

Automatic Voltage Regulator:

Automatic Voltage Regulator, is basically a mechanically or electronically operated device which is used in the power distribution system to compensate the voltage drop in a feeder or distribution system. Based on the application, there are two type of Automatic Voltage Regulator. They are: 

1. Medium Voltage Regulator 

2. Low Voltage Regulator 

Medium voltage regulator is always mechanically operated and Low voltage regulator may be mechanically or electronically operated. In this blow we learn, how to select the proper Medium Voltage AVR for the distribution system. 

Single Phase 11KV AVR

Sizing of Automatic Voltage Regulator:

Let,
System Configuration 3 Phase, 4 Wire.
Transformer Ratting = 2500 KVA (Select as per load)

Transformer Load Current Calculation in HT Side:

Transformer Rating            = 2500kVA

Line Voltage                     = 11kV

Load Current (I_L)              = KVA Rating of Transformer / √3 X System Voltage

                                       = 2500KVA / 1.732 X 11KV

                                       = 132.21 A

Required Automatic Voltage Regulator (AVR) Size:

Voltage Regulation Range       = ±10% (Manufacturer data sheet of AVR)

Phase Voltage                       =11KV/ √3 = 6.351 kV

Voltage Regulator Size (KVA) = Volt. RegulationXPhase Volt.XMax. Line Current

                                           = 10% x 6.351 kV x 131.21 A

                                           = 83.33KVA