2.5 Distance Protection
129
7SD5 Manual
C53000-G1176-C169-1
Current Transformer 600 A / 5 A
Voltage Transformer 110 kV / 0.1 kV
The resulting minimum load impedance is therefore:
This value can be entered as a primary value when parameterizing with a personal
computer and DIGSI
®
. The conversion to secondary values is
when applying a security margin of 10 % the following is set:
primary: R load (Ø-Ø) = 97.98 Ω or
secondary: R load (Ø-Ø) = 10.69 Ω.
The spread angle of the load trapezoid ϕ load (Ø-E) (address 1542) and ϕ load
(Ø-Ø) (address 1544) must be greater (approx. 5°) than the maximum arising load
angle (corresponding to the minimum power factor cosϕ).
Calculation Example
:
Minimum power factor
cos Ï•
min
= 0.63
Ï•
max
= 51°
Setting value ϕ load (Ø-Ø) = ϕ
max
+ 5° = 56°.
Overcurrent, U/I
and U/I/Ï• p i c k u p
Depending on the ordered version, the 7SD5 distance protection, if configured as the
main or backup protection function, features a range of fault detection modes, from
which the appropriate type for the particular system conditions can be selected
(7SD5***-*****-*D** and 7SD5***-*****-*G****).
If the device does not feature an explicit pickup function or if during configuration of
the protection functions (Section 2.1.1.3) you have selected as pickup type Dis.
PICKUP = Z< (quadrilat.) (address 117), the mentioned settings are not relevant
and cannot be accessed.
Available pickup modes are described in Section 2.5.1 in detail. If the device has
several alternative pickup modes, one option has been selected when configuring in
address 117. Below, parameters are given and discussed for all pickup modes. With
the following settings, only those parameters will appear that apply for the selected
pickup mode.
With the U/I(/Ï•) pickup mode you can determine the voltage measurement and, if ap-
plicable, the phase-angle measurement for phase-to-earth measuring units, and for
phase-to-phase measuring loops separately. Address 1901 PROGAM U/I indicates
which loop voltages apply to phase-to-earth and which to phase-to-phase:
In networks with earthed starpoint, a selection using U
Ph-E
with earth faults and U
Ph-
Ph
with non-earthed faults is often preferred (address 1901 PROGAM U/I =
LE:Uphe/LL:Uphp). This mode has a maximum sensitivity for all fault types; howev-
er, it requires the unambiguous detection of earth faults via the earth-fault detection
function (also see Section 2.5.1). Otherwise, a mode using U
Ph-E
for all fault types may
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