INDICATORS
Pre-fault alarm ...........................................................… Red indicator
Leakage trip delay time .............................................… Red indicator
Leakage trip ..............................................................… 7-segment display and red indicators
Manual test trip .................................................……......….. 7-segment display and red indicators
ZCT connection fault ................................................…….... 7-segment display and red indicators
Trip records .................................................................. 7-segment display
Real-time leakage current ............................................ 7-segment display
ZERO-PHASE CURRENT TRANSFORMERS
To operate with Mikro's ZCT series of current transformers
NX300A & NX300EA Earth Leakage Relay
User’s Manual
A BRIEF OVERVIEW
MECHANICAL
Mounting....................................................................… Standard DIN 96x96mm panel mount
Approximate weight....................................................... 0.58kg (excluding ZCT)
9.
CONNECTION DIAGRAMS
AUX
L1 L2 L3 N
PE
N
L
MIKRO
ZCT
The EARTH wire
NX300A
must not pass
1
2
3
4
5
6
7
8
through the ZCT
SHUNT
TRIP
CONTACT
TRIP
NC
NO
C
9
10
11
12
13
14
15
16
LOAD
AUX
REMOTE
L1 L2 L3 N
PE
N
L
RESET
MIKRO
ZCT
NX300EA
The EARTH wire
must not pass
1
2
3
4
5
6
7
8
through the ZCT
CONTACTOR
TRIP
ALARM
POSITIVE SAFETY
CONTACT
CONTACT
CONTACT
NC
NO
C
NO
C
NC
NO
C
9
10
11
12
13
14
15
16
LOAD
a - DATA display
b - Trip status indicator
c - Alarm status indicator
d - DP2 indicator
e - Decrement button
f - Increment button
g - RESET button
h - TEST button
i - Model
j - DP1 indicator
k - FUNC display
1.
DESCRIPTION
Symbols
I
n
- Sensitivity setting
t
- Time delay setting
Flt 1 - Fault record #1 (Most recent)
Flt 2 - Fault record #2
Flt 3 - Fault record #3 (Oldest)
The NX300A and NX300EA are microprocessors based earth leakage relays designed for measure
the low-level current flowing from the live part of the installation to the earth in the absent of the
insulation fault. A zero phase current transformer is connected to the relay and function as the sensor
for sensing the leakage current. All conductors of the circuit to be protected shall go through the ZCT.
For better fault preventive control of the system or equipment to be protected, NX300EA series comes
with a pre -fault alarm contact and a positive safety contact. The pre-fault alarm contact is activated
whenever the leakage current exceed 50% of the sensitivity setting. While the positive safety contact
is activated if the relay is power up and function correctly. The NX300EA series also built-in a digital
input port for remotely reset the relay after leakage fault trip, manual test trip or ZCT connection fault.
10. CASE DIMENSION
* Applicable to NX300EA series only
90mm
70mm
96mm
96mm
SIDE
FRONT
PANEL
CUTOUT
91±0.5mm
91±0.5mm
∆
∆
EARTH LEAKAGE RELAY
NX 300A
TEST
RESET
TRIP
ALARM
a
b
c
d
e
f
g
h
k
j
i
