Micom P631 - Readiness of Thermal Overload Protection; Tripping Characteristics

3.24.2 Readiness of Thermal Overload Protection
Thermal overload protection will issue the THRM1: Not ready signal if one of
the following conditions applies:
●
Thermal overload protection is disabled.
●
Thermal overload protection is blocked because of a fault in the coolant
temperature (ambient) acquisition.
●
Thermal overload protection is blocked because of an incorrect setting.
●
The thermal replica is blocked via an appropriately configured binary signal
input.
64Z5190A
THRM1:
Not ready
[ 039 154 ]
THRM1:
Enabled
[ 039 129 ]
THRM1:
Replica block EXT
[ 039 150 ]
THRM1:
Setting error,block.
[ 039 126 ]
THRM1:
Block. by CTA error
305 221
Fig. 3-111: THRM1: Not ready
3.24.3 Tripping Characteristics
The maximum phase current IP,max.y of the selected transformer end is used to
track a first-order thermal replica according to IEC 255-8. The following
parameters will govern the tripping parameters:
●
The set thermal time constant (τ) of the protected object
THRM1: Tim.const.1,>Ibl PSx
●
The tripping threshold Δϑ
trip
set at THRM1: Rel. O/T trip PSx
●
The accumulated thermal load Δϑ
0
●
The updated measured coolant temperature Θ
c
for the protected object
●
The maximum permissible coolant temperature Θ
c,max
set at
THRM1: Max.perm.cool.tmpPSx
●
The maximum permissible object temperature Θ
max
set at
THRM1: Max.perm.obj.tmp.PSx
The object temperature is calculated from the current I
P,max.y
and can be
displayed at THRM1: Object temperat.,TH1. The coolant temperature is
either measured via the PT 100 input or via a 20 mA input, or a default
temperature value is used instead. This choice is governed by the setting at
THRM1: Select CTA PSx. The coolant temperature is displayed at
THRM1: Coolant temp. TH1. The difference between the settings for the
maximum permissible temperatures of the protected object and the coolant can
be displayed at THRM1: O/T f.Iref persist 1.
The tripping characteristics are then defined by the equation:
t = τ ⋅ ln
(
I
I
ref
)
2
− Δϑ
0
(
I
I
ref
)
2
− Δϑ
trip
⋅
(
1 −
Θ
c
− Θ
c,max
Θ
max
− Θ
c,max
)
The setting for the operating mode selects an “absolute” or “relative” replica. If
the setting is for “Absolute replica”, the P631 will operate with a fixed trip
threshold Δ
trip
of 100 %.
P631
3 Operation
3-146 P631/EN M/R-11-C // P631-310-650