ABB ret650 - Page 373

k max sr
R
al alreq ct L
2
pr
r
I I
S
E E a R R
I
I
×
æ ö
³ = × × + +
ç ÷
è ø
EQUATION1080 V2 EN-US (Equation 61)
kzone1 sr
R
al alreq ct L
2
pr
r
I I
S
E E k R R
I
I
×
æ ö
³ = × × + +
ç ÷
è ø
EQUATION1081 V2 EN-US (Equation 62)
where:
I
kmax
Maximum primary fundamental frequency current for close-in forward and
reverse faults (A)
I
kzone1
Maximum primary fundamental frequency current for faults at the end of zone 1
reach (A)
I
pr
The rated primary CT current (A)
I
sr
The rated secondary CT current (A)
I
r
The rated current of the protection IED (A)
R
ct
The secondary resistance of the CT (W)
R
L
The resistance of the secondary wire and additional load (W). In solidly earthed
systems the loop resistance containing the phase and neutral wires should be
used for phase-to-earth faults and the resistance of the phase wire should be
used for three-phase faults.
In isolated or high impedance earthed systems the resistance of the single
secondary wire can always be used.
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
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
1MRK 504 169-UEN A Section 19
Requirements
Transformer protection RET650 2.2 IEC 367
Application manual