7UT51 v3
Description of Relay
2
PRIM-2330C 23
2.9 Phase Differential Protection of a Bus (87B)
Table 2.6
Specifications for Phase Differential Protection of a Bus (87B) (details in Chapter 6)
Settings
Operational status Active, inactive, or block
-
contacts; can be temporarily changed
using binary
-
signal inputs
Minimum differential current required for pickup (87B) 0.30 to 2.50 times
I
n
(steps 0.01)
Restraint based on total current level Characteristic with two sloped segments (see Figure 6.3)
Restraint for through
-
fault causing CT saturation Through fault current restraint minimum 5.00 to 15.00 times
I
n
(step 0.01); duration of restraint 2 to 250 cycles, or ∞; relay can
detect an evolving internal fault and release this restraint.
Time delay before trip 0.00 to 60.00 s (step 0.01 s), or ∞
Time delay before reset 0.00 to 60.00 s (step 0.01 s)
Events that can control signal contacts or trip contacts Change in operational status; pickup, dropout, trip, and reset
events, start of time delay before trip; start and end of restraint.
All events are logged, as are the differential and restraint current
levels at the time of a trip.
Inherent Operating Times
Pickup time with single
-
ended infeed: 60 Hz 50 Hz 16
-
2/3 Hz
I
DIFF
≥ 1.5 times 87B pickup threshold level (approx.) 25 ms 25 ms 70 ms
I
DIFF
≥ 5.0 times 87B pickup threshold level (approx.) 16 ms 17 ms 25 ms
Dropout (approximate) 25 ms 30 ms 90 ms
Dropout Ratio
87B dropout ratio (dropout/pickup; approximate) 0.7
Operating Tolerances (with default settings)
Pickup characteristic ±5% of characteristic value (for
I
< 5×
I
n
)
Set time delays ±1% of setting value or 10 ms, whichever is greater
Effect of Environmental Influences on Times and Tolerances
Supply power voltage ≤ 1% if between 80% and 115% of nominal voltage
Ambient temperature ≤ 0.5% / 10 K if between 0°C and 40°C (32°F and 104°F)
System frequency ≤ 1% if between 80% and 120% of nominal frequency
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