ABB RELION 670 Series Technical Manual page 1390

Section 26
Inverse time characteristics
æ
ç
ç
[ ]
s =
t
ç
æ
ç
ç
ç
è
è
EQUATION1640 V1 EN-US
where:
p, A, B, C
Pickupn
td
i
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:
(
- ×
t B td
op
EQUATION1642 V1 EN-US
where:
t
op
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:
t
æ
æ
ò i
ç
ç
ç
è
Pickupn
è
0
EQUATION1643 V1 EN-US
For the numerical protection the sum below must fulfil the equation for trip.
1384
ö
÷
A ÷
+
B ×
td
÷
P
ö
i
÷
-
÷
C ÷
ø
ø
Pickupn
æ ö
P
)
æ ö
i
× ç ÷ =
-
ç ÷ C A td
ç ÷
è ø
Pickupn
è ø
is the operating time of the protection
ö
P
ö
÷
- × ³ ×
÷
C dt A td
÷
ø
ø
are constants defined for each curve type,
is the set pickup current for step n,
is set time multiplier for step n and
is the measured current.
×
1MRK 502 066-UUS B
(Equation 228)
(Equation 229)
(Equation 230)
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