Areva MiCOM P441, Техническое руководство

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P44x/EN TD/E33 Technical Data
Page 20/30 MiCOM P441/P442 & P444
6.3 Back-up Overcurrent Protection
6.3.1 Threshold Settings
Setting Stage Range Step size
I>1 Current Set 1st Stage
0.08 - 4.0
In
0.01
In
I>2 Current Set 2nd Stage
0.08 - 4.0
In
0.01
In
I>3 Current Set TOR/SOTF protection
0.08 - 32
In
0.01
In
I>4 Current Set Stub bus protection
0.08 - 32
In
0.01
In
6.3.2 Time Delay Settings
Each overcurrent element has an independent time setting and each time delay can be
blocked by an optically isolated input:
Element Time delay type
1st Stage Definite Time (DT) or IDMT(IEC/UK/IEEE/US
curves)
2nd Stage DT or IDMT
3rd Stage DT
4th Stage DT
6.3.3 Inverse Time (IDMT) Characteristic
IDMT characteristics are selectable from a choice of four IEC/UK and five IEEE/US curves
as shown in the table below.
The IEC/UK IDMT curves conform to the following formula:
t = TMS
×
K
(I/I
s
)
α
–1
The IEEE/US IDMT curves conform to the following formula:
t=
TD
7
×
( )








+
−
L
1 I/I
K
S
α
Where
t = operation time
K = constant
I = measured current
I
S
= current threshold setting
α
= constant
L = ANSI/IEEE constant (zero for IEC/UK curves)
TMS = Time Multiplier Setting for IEC/UK curves
TD = Time Dial Setting for IEEE/US curves