78
FUNCTION CHARACTERISTICS
The relay residual rated voltage U
En
must be indifferently estimated by means of the following ge-
neral formula:
U
En
= √3 · U
ng
/K
VT
= √3 · 6000 / (√3 · 60) = 100 V
or by means the following streamlined formula:
U
En
= 3 · U
ns
= 3 · 100 / 3 = 100 V
Case B
The relay residual rated voltage U
En
must be estimated by means of the following general formula:
If a VT with primary rated voltage equal to the grid voltage divided by √3 is connected from star neu-
tral to ground, the following streamlined calculus may be used:
U
En
= VT secondary rated voltage [V]
Example B1
The relay residual rated voltage U
En
may be estimated by means of the following formula:
U
En
= (U
ng
/√3) /K
VT
= (10000 /√3) / (110/ √3) = 91 V
Example B2
The relay residual rated voltage U
En
may be estimated by means of the following general formula:
U
En
= (U
ng
/√3) /K
VT
= (6000 /√3) / (60/ √3) = 100 V
Case C
The relay residual calculated rated voltage U
ECn
is estimated automatically by means of the formula:
U
ECn
= √3∙ U
n
Example C1
For the example 2 U
n
= 100 V. U
ECn
is estimated automatically by means of the formula:
U
ECn
= U
n
∙ √3
= 100 ∙ √3
= 173 V
VT ratio K
VT
ng
where the VTs [V] / √3 are connected
U
En
=
EsB1-UEn.ai
K
VT
=
/ V
V
11000
3
3
100
= 110 /
K
VT
=
/ V
V
11000
3
3
100
= 110 /
Grid nominal voltage U
ng
= 10 kV
Ratio of VT connected from star neutral to ground:
U
ng
= 10 kV
U
En
XMR-x
EsB2-UEn.ai
K
VT
=
/ V
V
6000
3
3
100
= 60 /
K
VT
=
/ V
V
6000
3
3
100
= 60 /
Grid rated voltage U
ng
= 6kV
Ratio of VT connected from star neutral to ground:
U
ng
= 6 kV
U
En
XMR-x
U
ECn
= 173 V
U
n
= 100 V
Es4-UEn.ai
K
VT
=
/
/
V
V
6000
3
100 3
= 60
/
/
V
V
6000
3
100 3
= 60
Grid rated voltage U
ng
= 6 kV
Ratio of line VTs K
VT
= U
np
/U
ns
=
U
ng
= 6 kV
52
XMR-x
XMR-D EQUIPMENT MANUAL
Ed. 2.9 - 02/2021
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