Siemens 7UT51 User Manual

7UT51 v3
Description of Relay
2
PRIM-2330C 21
2.7 Phase Differential Protection of a Transformer
(87T and 87HS)
Table 2.4
Specifications for Phase Differential Protection of a Transformer (87T and 87HS) (details in Chapter 4)
Settings
Operational status Active, inactive, or block
-
contacts; can be temporarily
changed using binary
-
signal inputs
Minimum differential current required for pickup (87T) 0.15 to 2.00 times
I
n
(0.01 steps)
Maximum differential current allowed before pickup (87HS) 0.5 to 20.0 times
I
n
(0.01 steps)
Restraint based on total current level Characteristic with two sloped segments (see Figure 4.9)
Restraint for through
-
fault causing CT saturation Through current 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.
Inrush restraint based on 2nd harmonic current 10% to 80% of fundamental current (step 1%); option to
crossblock other phases for a selectable duration (in
cycles); is released when the differential current exceeds
87HS.
Restraint based on 3rd, 4th, or 5th harmonic current 10% to 80% of fundamental current (step 1%); option to
crossblock other phases for a selectable duration (in
cycles); is released when the differential current exceeds a
set value (0.5 to 20.0 times
I
n
, step 0.1)or 87HS.
Time delay before trip (separate settings for 87T and 87HS) 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 events, start of time
delay before trip; start and end of restraint; trip events. 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 87T pickup threshold level (approx.) 35 ms 35 ms 85 ms
I
DIFF
≥ 1.5 times 87HS pickup threshold level (approx.) 25 ms 25ms 55 ms
I
DIFF
≥ 5.0 times 87HS pickup threshold level (approx.) 17 ms 18 ms 25 ms
Dropout time (approximate) 25 ms 30 ms 90 ms
Dropout Ratios
87T and 87HS dropout ratios
(dropout/pickup; approximate)
0.7
Operating Tolerances (with default settings)
Pickup characteristic ±5% of characteristic value (for
I < 5× I
n
)
Inrush restraint ±5% of setting value (for
I
2nd harmonic
≥ 15% of
I
fundamental
)
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 95% and 105% of nominal frequency.
Note:
87T function is blocked when frequency is less
than about 85% of the nominal frequency, or more
than about 120%; see Figure 4.12.

Siemens 7UT51 Specifications

General

Brand	Siemens
Model	7UT51
Category	Relays
Language	English