Mitsubishi Electric C Series Handling And Maintenance page 85

(7) Operation by wrong wire connection
Failure in passing the neutral wire through the ZCT
for the lines of single phase 3-wire or 3 phase 4-
wire is a simple mistake. In this case, the ELCB is
operated by single phase load current.
On the other hand, the common earth wire shall
not go through the ZCT as it can be cause mal-
function at leakage.
(8) Operation by inadequate earth
Though the wire is grounded at the earth side,
the wire shall not be earthed at the load side. By
the voltage of voltage drop in the line at the earth
side, a part of the load current is diverted as
shown by I' , and the ELCB is operated.
T
(9) Operation of sound circuit at ground fault of shunt circuit
Not only the ELCB in the ground fault circuit but also the one in the sound circuit is operated in some cases
through the circuit as illustrated below. This can be avoided by keeping sensitive current suitably for the leak
current by static capacity to ground.
(10) Operation by overload and short-circuit
It is natural that the devices having overload or short-circuit operation elements operate at short-circuit. However, ELCB is commonly
used for many other purposes, and it tends to be overlooked that ELCB operate even at an overload and a short-circuit failure.
Moreover, even the one dedicated to ground fault is sometimes operated by an excessive overload and short-circuit because
balance performance of ELCB is limited. In these cases, however, overload and short-circuit can be noticed if they are significant.
(11) Environment of vibration, impact, high temperature etc.
These factors may be taken almost equal to those of Mitsubishi's MCCB. Heat resistivity of electronic circuits tends to be fell
unreliable. To Mitsubishi's ELCB, enough allowance is given to ratings of the parts, the parts which can withstand high tempera-
ture operation are used, and the ICs incorporating tempereture compensation circuits are used to ensure stable operation even
in varying temperature environment.
83
Operation of sound circuit by static capacity to ground
Wrong wire connection of 3 phase 4-wire line
Common earth wire
Wrong connection of common earth wire
Inadequate double ground
Fault circuit
Sound circuit
ZCT
Load
M
ZCT
M
I
T
I'
T