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1MAC050144-MB C
Section 4
Protection functions
615 series ANSI
207
Technical Manual
t[s]
Reset time in seconds
a
set Cooling time
b
percentage of pickup time elapse (
PICKUP_DUR
)
When the reset period is initiated, the time for which
PICKUP
has been active is saved.
Now, if the fault reoccurs, that is, the negative-sequence current rises above the set value
during the reset period, the trip calculations are continued using the saved values.
However, if the reset period elapses without a fault being detected, the trip timer is reset
and the saved values of pickup time and integration are cleared.
Inverse Curve Type B
The inverse time equation for curve type B is:
t[s]
Trip time in seconds
k
Machine time Mult
I
2
Negative-sequence current
I
S
Set Pickup value
I
r
Rated current
If the fault disappears, the negative-sequence current drops below the
Pickup value
setting
and the
PICKUP
output is deactivated. However, the function does not reset
instantaneously, but instead it depends on the equation or the
Cooling time
setting.
The timer can be reset in two ways:
• With a drop in the negative-sequence current below pickup value, the subtraction in
the denominator becomes negative and the cumulative sum starts to decrease. The
decrease in the sum indicates the cooling of the machine and the cooling speed
depends on the value of the negative-sequence current. If the sum reaches zero
without a fault being detected, the accumulation stops and the timer is reset.
• If the reset time set through the
Cooling time
setting elapses without a fault being
detected, the timer is reset.
The reset period thus continues for a time equal to the
Cooling time
setting or until the
operate time decreases to zero, whichever is less.
4.1.9.6
Application
In a three-phase motor, the conditions that can lead to unbalance are single phasing,
voltage unbalance from the supply and single-phase fault. The negative sequence current
damages the motor during the unbalanced voltage condition, and therefore the negative
sequence current is monitored to check the unbalance condition.
t s
a
b
[ ]
= ×⎛
⎝⎜
⎞
⎠⎟
100
t s
k
I
I
I
I
r
S
r
[ ]
=
⎛
⎝
⎜
⎞
⎠
⎟ −
⎛
⎝
⎜
⎞
⎠
⎟
2
2
2
Содержание 615 Series ANSI
Страница 1: ...Relion Protection and Control 615 series ANSI Technical Manual ...
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Страница 29: ...1MAC050144 MB C Section 615 series ANSI 22 Technical Manual ...
Страница 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
Страница 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
Страница 635: ...Section 10 1MAC050144 MB C Other functions 628 615 series ANSI Technical Manual ...
Страница 707: ...Section 15 1MAC050144 MB C Applicable standards and regulations 700 615 series ANSI Technical Manual ...
Страница 711: ...Section 16 1MAC050144 MB C Glossary 704 615 series ANSI Technical Manual ...
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