ISA T1000 PLUS - Page 95

DOC. MIE91093 Rev. 1.34 Page 95 of 145
SUPPLY
FAULT
PHASE 1
PHASE 2
PHASE 3
3 PHASE
ANY
Φ(I-V)
Φ(I-V)
Φ(I-V)
1 PHASE
PHASE 1
Φ(I-V)
Φ(I-V) +
240°
Φ(I-V) +
120°
PHASE 2
Φ(I-V) +
120°
Φ(I-V)
Φ(I-V) +
240°
PHASE 3
Φ(I-V) +
240°
Φ(I-V) +
120°
Φ(I-V)
3) Zone limits test
Given the fault impedances Z1, Z2, Z3, Z4 of the zone limits,
compute as follows the corresponding fault voltages V1, V2,
V3, V4:
Vf = Z*If*(1+KoL)
For instance: KoL = 1; If = 10 A
Vf = 20 * Z
These voltages are the limits between following zones, as
follows:
VOLTAGE
<
V1
>
V1
<
V2
>
V2
<
V3
>
V3
<
V4
> V4
TIMING
T1
T2
T2
T3
T3
T4
T4
NO
TRIP
ZONE
LIMIT
1
2
3
STARTER
Where: T1, T2, T3, T4 are respectively the time settings for
zones 1, 2, 3, 4 (case of three zones plus the starter).
Once fault current and pre-fault voltage amplitudes have been
adjusted to VN, stop the test and start again. Adjust the fault
voltage of the selected phase at a value slightly less than V1,
VT11: the trip time should be the one of zone 1. Slightly
increase the fault voltage and start again with value VT12: trip
time should become T2. The procedure can be repeated at
will, until the first zone is checked with the desired accuracy:
the result is