ERL L-PRO 4000, User Manual

Page: 69 / 406

4 Protection Functions and Specifications
D02706R02.30 L-PRO 4000 User Manual 4-19
Line
Energization
Supervision
Logic
Figure 4.13: Line Energization Supervision Logic
Note: Vpos is the present positive sequence voltage.
VposOld is the positive sequence voltage at two cycles before.
The Logic shown in “Line Energization Supervision Logic” on page 4-19 has
been introduced in order to prevent potentially erroneous operations of the 21
upon energizing of T-tapped transmission lines that have transformers connect-
ed and the PT connected on the line side of the breaker. This logic does not re-
quire any user setting.
In this logic, the present positive sequence voltage is compared with the posi-
tive sequence voltage of 2 cycles previously. In an energization situation, the
VposOld would be near zero V and the present Vpos would be approximately
the nominal. As time goes by the old Vpos gets updated with the nominal volt-
age and would eventually equal the present. When it gets within 10 V second-
ary the top input to the AND gate would reset, go to zero, and reset the blocking
function.
The second input is the previous 2 cycle positive sequence voltage and has an
undervoltage setting of 30 V. This input goes high to block the distance relays
only if the positive sequence voltage from 2 cycles back was less than 30 V
(approximately 50% nominal), so, for a line that has been previously energized
and now experiences a fault, no distance relay blocking takes place.
The third input (the bottom one) produces an output only if the positive se-
quence line current is less than 4% nominal or 4.0% of 5 A secondary = 0.20
Outer (R4) R3 to 100.0 ohms secondary (5A)
R3 to 500.0 ohms secondary (1A)
Top Blinder
Outer (X4) X3 to 100.0 ohms secondary (5A)
X3 to 500.0 ohms secondary (1A)
Inner (X3) X2 to X4 ohms secondary
Bottom Blinder
Inner (X2) X1 to X3 ohms secondary
Outer (X1) -100.0 to X2 ohms secondary (5A)
-500.0 to X2 ohms secondary (1A)
Table 4.6: 68 Power Swing Function Details
Vpos - VposOld > 10 volts
1 sec.
20 ms
VposOld < 30 volts
Ipos < 4% of Norminal Current
Block all 21 devices