MICROENER MM30-DK, Operation Manual

Page: 5 / 36

MM30-DK
Doc. N° MO-0050-ING
Rev. 2
Pag. 5 of 36
Copyright - 2010 - Microener
2.2
– Operation and Algorithms
2.2.1
– Reference input variables
Display Description Setting Range Step Unit
NodAd 1 Identification number for connection serial communication 1 - 250 1 1
Fn 50 Hz Mains frequency 50 - 60 10 Hz
In 500 Ap Rated primary current of the phase C.Ts. 1 - 9999 1 A
On 500 Ap
Rated primary current of the C.Ts. or of the tore C.T.
detecting earth fault current
1 - 9999 1 A
Im 1.0 In Motor full-load current (p.u. of phase C.Ts. rated current) 0.1
– 1.5
0.01 In
Ist 6 Im Motor starting current (p.u. of motor full load current) 0.5
– 10
0.1 Im
tst 5 s Motor starting time 1
– 120
1 s
Itr 0.5 Ist
Switch-over current for control of two-step motor starter
(p.u. of motor starting current)
Dis
– 0.1 – 1
0.1 Ist
tTr 6 s Max switch-over time from start-up 0.5
– 50
0.1 s
2.2.2
– Input quantities
2.2.2.1
– Mains Frequency
The relay can operate either in 50Hz or 60Hz systems.
The rated Mains Frequency “ Fn “ must be set accordingly.
2.2.2.2
– Phase Current inputs
The relay directly displays the r.m.s. value of the Phase Currents “
IA
“, “
IB
”, “
IC
” flowing in the
Primary of the input Current Transformers and refers all its measurements to that value.
To make the relay properly working with any C.T., when programming the relay settings we have
to input the value of the Rated Primary Current “ In “ of the phase C.Ts.
For the Phase Current inputs, 1A or 5A configuration can be selected by moving the jumpers J1
and J2 provided on the C.T. input card (See § 19).
Example :

Phase CTs 1500/5A and Core Balance CT 100/1A

Set In = 1500A and On = 100A

Configure CT input card with jumpers J1, J2 in the 5A position.
Only phase A and C currents are measured, whereas the current of the phase B is computed as
vector summation of the currents of the other two phases.
The algorithm is based on the following considerations coming from well-known vector relations
among the three-phase currents and the zero sequence current.
- In any circumstance
– currents balanced or not, sinusoidal or not – it is always true that:
 
0 I I I I 1
0 C B A
   
-
When no Earth Fault exists (I
0
= 0)
 
 
C A B C B A
I I I 0 I I I 2
     
The earth fault protection element is independently supplied by the residual current coming either
from the residual connection of the 3 system C.Ts. or from the core balance C.T.
If any Earth Fault is experienced (I
0

0) the Earth Fault Protection Element trips independently
from the phase current measuring elements.