AZT-9
ZPrAE Sp. z o.o.
13
t = TMS * { k/[(I/I
S
)
α
-1] + c }
where:
t – time between energising and trigger of selected protection stage,
I – present value of measured current,
I
S
– set energising current of a given stage,
α, k, c
– constants defining a given characteristic,
TMS = tdel [s] – multiplier of a given characteristic.
Table below shows the values of constant α, k and c for available ID
MT
characteristics. Values of constants, except for the first characteristic, are defined in
accordance with the requirements of IEC, IEEE and C0 standards.
IDMT characteristics
k
α
c
Extremely Inverse ZPrAE
80
3
0
Standard Inverse IEC
0.14
0,02
0
Very Inverse IEC
13.5
1
0
Extremely Inverse IEC
80
2
0
Long Time Inverse IEC
120
1
0
Moderately Inverse IEEE
0.0515
0.02
0.114
Very Inverse IEEE
19.61
2
0.491
Extremely Inverse IEEE
28.2
2
0.1217
Inverse C08
5.95
2
0.18
Short Timer Inverse C02
0.02394
0.02
0.01694
Reset time for characteristics that comply with IEC standard is defined the same as
for DMT independent mode. For characteristics that comply with IEEE and CO standards
reset time is calculated based on the following equation:
t = RTMS * { t
r
/[(1-(I/I
S
)
α
]}
where:
t – time between the disappearance of energising signal and resetting of the calculated
delay time,
I – present value of measured current,
I
S
– set energising current of a given stage
α, t
r
– constants defining a given characteristics,
RTMS = tres [s] – multiplier of a given characteristics.
Table below shows the values of constant α and t
r
for available IDMT characteristics
to be applied in the equation for reset time.
IDMT characteristics
t
r
α
Moderately Inverse IEEE
4.85
2
Very Inverse IEEE
21.6
2
Extremely Inverse IEEE
29.1
2
Inverse C08
5.95
2
Short Timer Inverse C02
2.261
2
