ABB Relion 670 series - Page 1189

[ ]
= ×
-
+
æ ö
ç ÷
ç ÷
ç ÷
æ ö
ç ÷
ç ÷
ç ÷
è ø
è ø
P
A
t td
i
C
Pickupn
s B
EQUATION1640 V1 EN (Equation 195)
where:
p, A, B, C are constants defined for each curve type,
Pickupn is the set pickup current for step n,
td is set time multiplier for step n and
i is the measured current.
For inverse time characteristics a time will be initiated when the current reaches the set
pickup level. From the general expression of the characteristic the following can be seen:
( )
- × - ×
æ ö
æ ö
× ç ÷ =
ç ÷
ç ÷
è ø
è ø
P
op
i
t B td C A td
Pickupn
EQUATION1642 V1 EN (Equation 196)
where:
t
op
is the operating time of the protection
The time elapsed to the moment of trip is reached when the integral fulfils according to
equation 197, in addition to the constant time delay:
- × ³ ×
æ ö
æ ö
ç ÷
ç ÷
ç ÷
è ø
è ø
ò
0
P
t
i
C dt A td
Pickupn
EQUATION1643 V1 EN
(Equation 197)
For the numerical protection the sum below must fulfil the equation for trip.
1MRK505222-UUS C Section 22
Inverse time characteristics
1183
Technical reference manual