ABB Relion 670 series - Page 1390

[ ]
= ×
-
+
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-US (Equation 228)
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-US (Equation 229)
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
230, 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-US
(Equation 230)
For the numerical protection the sum below must fulfil the equation for trip.
Section 26 1MRK 502 066-UUS B
Inverse time characteristics
1384
Technical manual