Table of Contents
Advertisement
Table 5.19 – Per Unit [pu] Scaling of Zero Sequence Voltage
Voltage measurement mode
= "2LL+Uo", "1LL+Uo/LLy"
U
secondary
=
SEC
U
⇒ per
PU
U
unit
0
SEC
per unit
=
U
U
⇒
SEC
PU
secondary
Example 1 – Secondary to per unit. Voltage measurement
mode is "2LL+U
"
0
U
= 110 V (This is a configuration value corresponding to U
0SEC
at full earth fault.)
Voltage connected to the device's input Uc is 22 V.
⇒ Per unit voltage is
U
= 22/110 = 0.20 pu = 20 %
PU
Example 2 – Secondary to per unit. Voltage measurement
mode is "3LN"
VT = 12000/110
Voltage connected to the device's input U
U
= U
= 0.
a
b
⇒ Per unit voltage is
U
= (66+0+0)/(3x110) = 0.20 pu = 20 %
PU
Example 3 – Per unit to secondary. Voltage measurement
mode is "2LL+Uo"
U
= 110 V (This is a configuration value corresponding to U
0SEC
at full earth fault.)
The device displays U
0
⇒ Secondary voltage at input Uc is
U
= 0.20x110 = 22 V
SEC
Example 4 – Per unit to secondary. Voltage measurement
mode is "3LN"
VT = 12000/110
The device displays U
0
⇒ If U
= U
= 0, then secondary voltages at U
b
c
U
= 0.2x3x110 = 66 V
SEC
Measurement Functions
Zero-sequence voltage (U
) scaling
0
Voltage measurement mode
= "3LN"
1
=
U
PU
VT
SEC
⋅
+
+
U
U
U
U
0
SEC
a
b
is 66 V, while
a
= 20 %.
= 20 %.
a
5-17
+
+
U
U
U
a
b
c
⋅
3
=
⋅
⋅
3
U
VT
c
PU
SEC
0
0
is
857-UM001A-EN-P – July 2009
Advertisement
Table of Contents
