ISA T1000 PLUS - Second Harmonic Restraint Test

DOC. MIE91093 Rev. 1.34 Page 124 of 145
)(
33
21
1
II
I
I
I
I
B
A
D

 Therefore, applying current Iac only (from T1000 PLUS)
may result in a trip even when the current generated
by the D1000 is zero: you must increase D1000 current
until the relay contact drops out
 If transformer Taps have to be taken into account, the
above formulas become a little more complex:
o Restraint Current:
2
)(
3
2
3
2
21
1
1
2
1
Tap
II
Tap
I
Tap
I
Tap
I
I
BA
R





o Differential Current:
2
21
1
1
2
1
)(
33
Tap
II
Tap
I
Tap
I
Tap
I
I
BA
D


1.15.8 Second harmonic restraint test
This test requires that you generate a distorted waveform:
The only way to generate such current waveform is to parallel
the main and auxiliary currents, having selected an 100 Hz
-1.5
-1
-0.5
0
0.5
1
1.5
0 0.005 0.01 0.015 0.02 0.025
50 Hz 2nd Harm 50 Hz + 2nd Harm