# Why CT secondary should not Open condition- Live Test Demo

### Why CT secondary should not Open condition-:

Basically CT nothing but current transformer. It works like a step up transformer.

As the diagram said

V1= primary voltage of the current transformer
V2= Secondary voltage of the current transformer

I1= Primary current

I2= Secondary current

L= length of the conductor (main CT secondary core length)

A = cross section of the conductor

CT ratio: 4000/1 amps.

Any type of load inductive or resistive

V1 x I1 =V2 x I2

Generated EMF in Sec side if it’s in open

• V2= V1 x I1/I2————————————–1
• Consider V1=pL x I1 /A
• HERE p=RESISTIVIE OF THE CONDUCTOR
• L= LENGTH OF THE CONDUCTOR
• A= CROSS SECTION OF THE CONDUCTOR
• Approximately p=1.72 x 10-8Ω.m.
• Length= 1 mtr
• Area= 180 Sqmm
• V1=1.72 x 10-8 x 1×4000/180 x 10^-6
• V1=0.382 V
• Put V1 in Equ 1
• V2= 0.382 x 4000/1
• V2=1528V
• CT secondary Voltage goes very high when it is in open condition. there is a chance of flash over or insulation failure.

To avoid that it must be kept short .