ABB Relion Technical Manual page 743

1MRK 502 048-UUS A
Technical manual
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
P
( ) æ ö
i
× ç
- ×
ç ÷
t B td
op ç
è ø
Pickupn
è
EQUATION1642 V1 EN
where:
t is the operating time of the protection
op
The time elapsed to the moment of trip is reached when the integral fulfils according to
equation 118, in addition to the constant time delay:
t
æ ö
P
æ ö
ò i
ç ÷
- × ³
ç ÷ C dt A td
ç ÷
è ø
Pickupn
è ø
0
EQUATION1643 V1 EN
For the numerical protection the sum below must fulfil the equation for trip.
æ ö
( )
n
P
æ ö
å
i j
ç ÷
D × - ³
t ç ÷ C
ç ÷
è ø
Pickupn
è ø
=
j 1
EQUATION1644 V1 EN
where:
j = 1
Dt
n
i (j)
For inverse time operation, the inverse time characteristic is selectable. Both the IEC and
ANSI/IEEE standardized inverse time characteristics are supported.
Time inverse characteristics
ö
÷ =
- ×
C A td
÷
ø
×
×
A td
is the first protection execution cycle when a fault has been detected,
that is, when
i
>
1
Pickupn
EQUATION1646 V1 EN
is the time interval between two consecutive executions of the
protection algorithm,
is the number of the execution of the algorithm when the trip time
equation is fulfilled, that is, when a trip is given and
is the fault current at time j
Section 21
(Equation 117)
(Equation 118)
(Equation 119)
737