AEG ME09 Installation, Operation And Maintenance Manual page 50

2.2.7
--
--
--
"
12
2.2.8
2.11
LT
ST
100 %
I
Gf sum
LT
ST
63 %
I
Gf sum
LT
ST
50 %
I
Gf sum
LT
ST
0 %
I
Gf su
2.2-08
INTRO BREAKER
TRIP UNIT
"
100%
100%
100%
100%
63 %
63%
63%
63%
50 %
50%
50%
50%
0%
0%
0%
0%
LOCKS ACCESSORIES
2.2.7 Thermal Memory
The thermal memory is a means to simulate temperature rise
and cooling caused by changes in the ow of current in the
conductors.
These changes may be caused by:
-- Repe ve motor star ng;
-- Loads uctua ng near the protec on se ngs;
-- Repeated circuit breaker closing on a fault.
Even very short overloads or short circuits can produce a certain
temperature rise. During normal opera ons these event are
tracked and stored in thermal memory resul ng in a reduc on in
the total circuit breaker tripping me.
If the Circuit Breaker has tripped on a over current event the
thermal e ects of the current previously running in the circuit
will be taken into account. (remembered). This can result in a
preven on of breaker re-closure onto a circuit running in 'Hot
condi ons' or cause the men oned reduc on in the total
tripping me a er re-closure.
The trip unit tracks these occurrences across a
me frame of 12 minutes.
2.2.8 Neutral Protec on
Four pole ME09 circuit breakers are equipped with a neutral
pole located on the le , when viewed from the breaker front.
The Mpro trip unit allows the neutral pole to be op oned with
or without a full set of protec on devices. When neutral
protec on is chosen the LT (overload) protec on device in the
neutral pole can be set at on of three di erent values. Choosing
neutral protec on and the value thereof depends on the
network and installa on con gura on.
The following op ons are available:
-- Neutral unprotected (0%)
-- Neutral protected and the LT protec on set at one of three values.
-- 50% Half Neutral protec on
-- 63% Neutral Protec on
-- 100% Full Neutral protec on)
Se ng the LT device in the Neutral pole in uences other
installed protec on devices (if present) as indicated in table
2.11:
Table 2.11
Protec on Device
Neutral se ng
LT
ST
100 %
I
Gf sum
LT
ST
63 %
I
Gf sum
LT
ST
50 %
I
Gf sum
LT
ST
0 %
I
Gf su
TESTS APPENDIX
Device se ng in Neutral pole
100%
100%
100%
100%
63 %
63%
63%
63%
50 %
50%
50%
50%
0%
0%
0%
0%