ABB Relion 670 series - Breaker Failure Protection

a This factor depends on the design of the protection function and can be a function
of the primary DC time constant of the close-in fault current.
k This factor depends on the design of the protection function and can be a function
of the primary DC time constant of the fault current for a fault at the set reach of
zone 1.
The a- and k-factors have the following values for the different types of distance
function:
High speed distance: (ZMFPDIS and ZMFCPDIS)
Quadrilateral characteristic:
a = 1 for primary time constant Tp £ 400 ms
k = 3 for primary time constant Tp £ 200 ms
Mho characteristic:
a = 2 for primary time constant Tp £ 400 ms (For a = 1 the delay in operation due
to saturation is still under 1.5 cycles)
k = 3 for primary time constant Tp £ 200 ms
Quadrilateral distance: (ZMQPDIS, ZMQAPDIS and ZMCPDIS, ZMCAPDIS and
ZMMPDIS, ZMMAPDIS)
a = 1 for primary time constant Tp £ 100 ms
a = 3 for primary time constant Tp > 100 and £ 400 ms
k = 4 for primary time constant Tp £ 50 ms
k = 5 for primary time constant Tp > 50 and £ 150 ms
Mho distance: (ZMHPDIS)
a = 1 for primary time constant Tp £ 100 ms
a = 3 for primary time constant Tp > 100 and £ 400 ms
k = 4 for primary time constant Tp £ 40 ms
k = 5 for primary time constant Tp > 40 and £ 150 ms
25.1.6.2 Breaker failure protection
The CTs must have a rated equivalent limiting secondary e.m.f. E
al
that is larger than or
equal to the required rated equivalent limiting secondary e.m.f. E
alreq
below:
sn
R
al alreq CT L
2
pn n
op
I
S
E E 5 I R R
I I
³ = × × + +
æ ö
×
ç ÷
è ø
EQUATION1677 V1 EN
(Equation 538)
where:
I
op
The primary operate value (A)
I
pr
The rated primary CT current (A)
I
sr
The rated secondary CT current (A)
I
n
The nominal current of the protection IED (A)
R
ct
The secondary resistance of the CT (W)
R
L
The resistance of the secondary cable and additional load (W). The loop resistance containing the
phase and neutral wires, must be used for faults in solidly grounded systems. The resistance of a
single secondary wire should be used for faults in high impedance grounded systems.
S
R
The burden of an IED current input channel (VA). S
R
=0.020 VA/channel for I
r
=1 A and S
R
=0.150 VA/
channel for I
r
=5 A
1MRK 506 369-UUS - Section 25
Requirements
Line distance protection REL670 2.2 ANSI 921
Application manual