Why CT secondary should not Open condition-:
As the diagram said
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.
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
- 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 .