4.8 Differential Protection for Transformers (ANSI 87T)
419
7UM62 Manual
C53000-G1176-C149-3
4.8
Differential Protection for Transformers (ANSI 87T)
Setting Ranges/
Resolutions
Differential Current
I
DIFF
>/
I
N transf
0.05 to 2.00
(Increments 0.01)
High-Current Stage
I
DIFF
>>/
I
N Transf
0.5 to 12.0
(Increments 0.1)
or
∞
( stage ineffective)
Pickup
Characteristic
see also Figure 4-8
Slope 1
0.10 to 0.50
(Increments 0.01)
Base Point 1
I
/
I
N Transf
0.00 to 2.00
(Increments 0.01)
Slope 2
0.25 to 0.95
(Increments 0.01)
Base Point 2
I
/
I
N Transf
0.00 to 10.00
(Increments 0.01)
Start Detection
I
/
I
N Transf
0.00 to 2.00
(Increments 0.01)
Factor for Increase of Characteristic
at Start
1.0 to 2.0
(Increments 0.1)
Max. Permissible Starting Time
0.0 to 180.0 s
(Increments 0.1 s)
Add-On Stabilization
I
/
I
N Transf
2.00 to 15.00
(Increments 0.01)
Inrush Stabilization
I
2fN
/
I
fN
10 % to 80 %
(Increments 1 %)
Harmonics)
see also Figure 4-9
Stabilization (nth harm.)
I
nfN
/
I
fN
10 % to 80 %
(Increments 1 %)
(n = 3rd or 5th Harmonics)
see also Figure 4-10
Release of Blocking
I
/
I
N Transf
0.5 to 12.0
(Increments 0.1)
by Higher-Order Harmonics
Tripping Delay Time
0.00 s to 60.00 s
(Increm. 0.01 s)
for
I
DIFF
> and
I
DIFF
>>
or
∞
(ineffective)
Duration of Add-On Stabilization
(2 to 250)
⋅
dur. of period (system frequ.)
or
∞
(ineffective)
Time for Cross-Blocking
(0 to 1000)
⋅
dur. of period (system frequ.)
for 2nd, 3rd or 5th Harmonics
or
∞
(continuous)
Pickup Times
without parallel operation of other protection functions
Dropout/Pickup Ratio
Approx. 0.7
Tolerances
With Preset Transformer Parameters
– Pickup Characteristic
±
3 % of setpoint value (for I < 5
⋅
I
N
)
– Inrush Restraint
±
3 % of setting value (for
I
2fN
/
I
fN
≥
15 %)
– Additional Delay Times
±
1 % of setting value or 10 ms
50 Hz
60 Hz
−
with
≥
1.5
⋅
Setting
I
DIFF
>/
I
N Transf
, approx.
35 ms
35 ms
−
with
≥
1.5
⋅
Setting
I
DIFF
>>/
I
N Transf
, approx.
25 ms
22 ms
−
with
≥
5
⋅
Setting
I
DIFF
>>/
I
N Transf
, approx.
18 ms
17 ms
