Mitsubishi Electric MELPRO-A Series Instruction Manual page 12

Operation value settings and using condition settings
1. Operation value settings
The operation value settings should be set with due
consideration given to various conditions of the systems,
such as residual voltage and current, and protection
coordination.
In regard to V setting, set it more than V
0
in order to avoid unwanted operation.
Precautions for design and installation
＜Connection＞
(1) Test terminals of ZCT: The test terminals of ZCT (kt
and ℓt) are used only for the operation test and
keep them open after the test. (Do not short the
test terminals.)
(2) Wiring material: Since the MDG-A4V relay is a high
sensitivity digital type relay, it is necessary to
suppress surge and noise from the main circuit and
other lines.
Therefore, use 2-core shielded cables with a
2
diameter of 0.75mm
terminals of the relay (ZCT circuit), and connect
the shield to E terminal of the relay or D-class
grounding. The cable burden shall be 5Ω or less for
both ways. (In the case of 0.75mm
100 meters.)
(3) Secondary wiring of ZCT: The secondary terminal (k,
ℓ), and the test terminal (kt, ℓt) are double nuts.
The wiring is connected between the nuts. When
connecting, do not loosen the inner side (ZCT side)
nut.
(4) Polarity: Polarity is very important to this relay.
Please pay attention to polarity for connecting from
ZCT and ZVT, and grounding point is also important.
(5) Shield grounding of power cable: When an electric
power cable is used at the primary side of ZCT, pay
attention to the shield grounding as shown in
JEAC8011 regulations.
measured value
0
or more to connect to the Z1-Z2
2
, one way is about
2. Using condition settings
For all using condition setting switches, factory settings
are set to a default of OFF.
(1) Frequency (SW1):
50Hz = ON, 60Hz = OFF
(2) Output contact (SW2):
Self-hold = ON, Auto-reset = OFF
(6) Handling of power cable: Please handle with care not
to damage the outer sheath of ZCT primary cable.
The bending radius should be more than 10 times the
conductor outer diameter. Please locate the three-
phase cable symmetrically in the ZCT through hole.
(7) Grounding of EVT: Please connect the "O" terminal
and "E" terminal of EVT to A-class grounding.
(8) Grounding of MDG-A4V relay: Because the Z2 terminal
and f+ terminal are internally short-circuited,
ground only one point of the V
(9) Connection to ZCT: Only one ZCT can be connected to
one MDG-A4V relay. If two or more ZCTs are connected
in parallel, correct detection may not be possible.
＜Caution on withstand voltage test＞
(1) After the relay is mounted into the panel, when the
test is performed between the high-voltage circuit
and the earth/the low-voltage circuit, be sure to
check that the secondary side of VT and ZCT are
grounded.
(2) When the test is performed between the low-voltage
circuit and the earth, be sure to disconnect the
secondary side of VT and ZCT from the earth.
12
circuit.
0
JEP0-IL9559