Siemens 7SA511 사용자 설명서

7SA511 Line Protection Relay

Reference A

Table A-7. Selected Measurement Quantities in Grounded Systems, with
Impedance Fault Detection

L1-E
L2-E
L3-E

L1-E
L2-E
L3-E

irrelevant

L1-L2
L2-L3
L3-L1

L1-L2
L2-L3
L3-L1

irrelevant

L1-E, L2-E
L2-E, L3-E
L1-E,

L3-E

L1-L2
L2-L3
L3-L1

2PH-E FLTS =
PHASE-PHASE

L1-E, L2-E
L2-E, L3-E
L1-E,

L3-E

L1-E
L2-E
L3-E

2PH-E FLTS =
LEADING PH-E

L1-E, L2-E
L2-E, L3-E
L1-E,

L3-E

L2-E
L3-E
L1-E

2PH-E FLTS =
LAGGING PH-E

L1-L2, L2-L3
L2-L3,

L3-L1

L3-L1,

L1-L2

L1-L2
L2-L3
L3-L1

irrelevant

L1-E, L2-E, L3-E
L1-L2, L2-L3, L3-L1

L3-E
L3-L1

3PH FAULTS =
E/F CONTROL

L1-E, L2-E, L3-E
L1-L2, L2-L3, L3-L1

L3-L1
L3-L1

3PH FAULTS =
PH-PH ONLY

L1-E, L2-E, L3-E
L1-L2, L2-L3, L3-L1

L3-E
L3-E

3PH FAULTS =
PH-E ONLY

A.3.3  Fault Loop Determination in Ungrounded Systems (Optional)
In isolated or compensated networks, currents resembling a short circuit are not present in the
case of a single-phase ground fault. Only a displacement of the voltage triangle occurs, as
illustrated in Figure A-7, and this condition does not represent any immediate danger to network
operation. In this case, the distance protection must not trip since the phase-to-ground voltage of
the faulty phase is zero throughout the network. A trip would lead to, at each measuring point, a
measured impedance equal to zero for the faulty phase-to-ground loop. Therefore, pickup of one
single phase-to-ground fault detector is avoided in the 7SA511 relay.