Section 5
Bay protection functions
5.1
Distance protection 21 (DIST)
5.1.1
Mode of operation
GUID-3308DD58-A1A9-4B83-8EAA-20A7460EF61B v1
Distance protection for the high-speed discriminative protection of long or short overhead
lines or cables, double-circuit lines, heavily loaded lines, lines with weak infeeds and what are
referred to as short-zone lines.
The protection is applicable to solidly or low-resistance grounded systems, systems with
Petersen coils or to ungrounded systems.
All kinds of faults are detected including close-in three-phase faults, cross-country faults,
evolving faults and high-resistance ground faults. The protection remains stable in the
presence of power swings and reversal of energy direction. Switching onto an existing fault
results in instantaneous tripping of the circuit-breaker.
The distance function can also act as backup protection for the power transformer and
neighboring lines. Most of the logic described in this section (for example, the transmission of
signals) is not used for these applications.
5.1.2
Features
GUID-C6B602BB-E3EC-46F4-9602-3BF51C578BEE v1
•
Overcurrent or underimpedance starters (polygon characteristic)
•
Directional or non-directional (configurable) underimpedance starters
•
5 distance stages (independently set polygon characteristics)
•
Polygon characteristic with adjustable load discrimination
•
6 concurrently computed measuring loops (L1E, L2E, L3E, L1L2, L2L3, L3L1)
•
Definite time overcurrent backup protection also applicable for protecting short zones (T
zone in 1½ breaker schemes)
•
VT supervision
•
Power-swing blocking
•
Tripping logics for:
•
Switch-onto-fault protection
•
Overreaching zone
•
Permissive underreaching transfer tripping (also for weak infeed and
communications channel failure)
•
Permissive overreaching transfer tripping (also for weak infeed, communications
channel failure and reversal of energy direction)
•
Blocking scheme (also for reversal of energy direction)
5.1.3
Inputs and outputs
5.1.3.1
CT/VT inputs
GUID-27BEC646-2633-467C-8159-5E680C7F3C12 v1
•
Three-phase currents
•
Three-phase voltages
•
Neutral current
1MRK 505 406-UEN B
Section 5
Bay protection functions
Bay protection functions REB500
25
Technical manual
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