1MAC050144-MB C
Section 4
Protection functions
615 series ANSI
309
Technical Manual
Figure 147:
Thermal behavior
The required overload factor and negative sequence current heating effect factor are set by
the values of the
Overload factor
and
Negative Seq factor
settings.
In order to accurately calculate the optimal thermal load, different time constants are used
in the above equations. These time constants are employed based on different motor
running conditions, for example starting, normal or stop, and are set through the
Time
constant start
,
Time constant normal
and
Time constant stop
settings. Only one time
constant is valid at a time.
Table 307: Time constant and the respective phase current values
The
Weighting factor p
setting determines the ratio of the thermal increase of the two
curves
Θ
A
and
Θ
B
.
The thermal level at the powerup of the IED is defined by the
Initial thermal Val
setting.
The temperature calculation is initiated from the value defined in the
Initial thermal Val
setting. This is done if the IED is powered up or the function is “disable” and “enable” back
or reset through the Clear menu.
The calculated temperature of the protected object relative to the operate level, the
TEMP_RL
output, is available through the monitored data view. The activation of the
BLOCK
input does not affect the calculated temperature.
The thermal level at the beginning of the startup condition of a motor and at the end of the
startup condition is available through the monitored data view at the
THERMLEV_ST
and
THERMLEV_END
outputs respectively. The activation of the
BLOCK
input does not have
any effect on these outputs.
Alarm and tripping logic
The module generates alarm, restart inhibit and tripping signals.
Time constant (tau) in use
Phase current
Time constant start
Any current whose value is over 2.5 x I
r
Time constant normal
Any current whose value is over 0.12 x I
r
and all
currents are below 2.5 x I
r
Time constant stop
All the currents whose values are below 0.12 x I
r
Содержание 615 Series ANSI
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