Cross-Country Fault Example - GE L90 Instruction Manual

9.5 SINGLE-POLE TRIPPING
Assume a single pole operation application where L90 relays are used to protect a two terminal line, (terminals T1 and T2)
using phase and ground distance zone 1, 2 and 3 elements in a permissive over-reaching transfer trip scheme. The perfor-
mance of the system with one- two and four-bit communications channels is outlined for a mid-line phase A-to-ground fault
and a co-incident phase B-to-ground fault just behind terminal T2. Assume also that the reclosers are enabled and reset.
At T1 the following protection elements will pickup:
• Ground Distance Zone 1, 2, and 3 for an AG fault
• Ground Distance Zone 2 and 3 for a BG fault
• Phase Distance Zone 2 and 3 for an AB fault
At T1 the phase selector will determine the fault is type ABG. This response is independent from the distance elements –
the Phase Selector sees two forward faults.
At T2 the following protection elements will pickup:
• Ground Distance Zone 1, 2, and 3 for an AG fault
At T2 the phase selector will determine the fault is type AG. The reverse BG fault is likely to be ignored.
If a one-bit channel is used, terminal T1 will trip three poles but terminal T2 will trip phase A only, (see the Tables below)
which is undesirable.
TERMINAL
BIT PATTERN RECEIVED
T1
T2
If a two-bit channel is used both terminals will trip phase A only, (see the Tables below) which is the desired outcome.
TERMINAL
BIT PATTERN RECEIVED
RX1
T1 1
T2 1
If a four-bit channel is used both terminals will trip phase A only, (see the Tables below) which is the desired outcome.
TERMINAL
BIT PATTERN RECEIVED
RX1 RX2
T1 0
T2 1
9
9-48
REMOTE DATA
REMOTE DETERMINATION
OF FAULT TYPE
RX1
1
1
REMOTE DATA
REMOTE DETERMINATION
OF FAULT TYPE
RX2
0
1 ABG
REMOTE DATA
REMOTE DETERMINATION
OF FAULT TYPE
RX3 RX4
0 0 1
0 0 0 ABG
L90 Line Current Differential System

9.5.6 CROSS-COUNTRY FAULT EXAMPLE

LOCAL DETERMINATION
OF FAULT TYPE
Any MULTI-P (ABG)
Any AG
LOCAL DETERMINATION
OF FAULT TYPE
AG ABG
AG
LOCAL DETERMINATION
OF FAULT TYPE
AG ABG
AG
9 THEORY OF OPERATION
LOCAL DATA
TRIP OUTPUT
Trip Three Phases
Trip Phase A
LOCAL DATA
TRIP OUTPUT
Trip Phase A
Trip Phase A
LOCAL DATA
TRIP OUTPUT
Trip Phase A
Trip Phase A
GE Multilin