Mikro MK231A User Manual
MK231A Earth-fault Relay User's Guide
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1. DESCRIPTION
The MK231A is a microprocessor based numerical
current measurement for excellent harmonic current rejection. The relay provides two- element (low-set
and high-set) earth-fault protection with definite time characteristic.
MK231A
setting of the relay.
allows the
display of
present load current; recorded fault current for last tripping; and all
earth-fault relay. It uses fundamental frequency
The 4-digit panel display on
the
2. LIGHT INDICATORS
The indicators display the status of the system as follow:
Indicator
Aux l> l>> FUNC DT Status
0 0 0 0 0 No Auxiliary power supply.
1 0 0 X X Normal condition, no tripping.
1 1 0 X X Low-set overcurrent triggered,
time delay countdown started.
1 0 1 X X High-set overcurrent triggered,
time delay countdown started.
1 B 0 B B Low-set tripped,
DT LEDs show tripped value.
1 0 B B B High-set tripped,
DT LEDs show tripped value.
1 X X B 1 Programming mode.
Step 1:
Press RESET key until the function digit
shows required function.
Step 2:
Press the UP and DOWN key
simultaneously to enter programming
mode. The function digit will blinks to
indicates the relay is in programming
Step 3:
Use the UP or DOWN key to select the
desired value.
Step 4:
To save the selected value, press the
UP and DOWN key simultaneously again.
It will exit the programming mode with the
data digits displaying new setting.
To exit programming mode without saving the
selected setting, press the RESET key once.
Table 1: System Status
1 = ON 0 = OFF X= don’t care, not blinking
B = blinking DT = DATA FUNC = FUNCTION
Indicator
FUNCTION DP DATA
. 0 off Earth fault current.
0 blink Previous tripped current.
4 off Low-set current setting.
5 off Low-set delay time setting.
6 off High-set current setting.
7 off High-set delay time setting.
8 off Soft switch setting.
Table 2: FUNCTION Code
Note:
Under normal operating condition, The 4-digit
is off. When the RESET key is pressed,
display will light up. The display will
automatically after 6 minutes if no further key is
pressed.
switch
the
display
4-digit
off
3. PUSH-BUTTONS OPERATION
a) Trip test
Press the “TEST” button to simulate a trip
b) Trip reset
Press the “RESET” button to reset the relay when
tripped.
c) View setting
When the relay is not under tripped condition,
pressing the “RESET” button will scroll through the
various functions.
4. OUTPUT CONTACTS
The MK231A has two set of output contact:
(i) CONTACT R1 - linked to trip signal.
(i) CONTACT R2 - linked to trip or start signal.
The output contact can be programmed to be either
auto reset type or manual reset type.
For auto reset type, the contact remain activated until
the fault current is removed.
For manual reset type, the contact remain activated.
5. SOFT SWITCHES
The MK231A incorporates 3 soft switches for system
configuration. When the function digit shows “8”, the
relay is in soft switch setting mode.
“ ”
switch value (SVL)
switch number (SW)
SW
1
2
SVL
00
Contact R1 linked to trip signal auto reset type.
01
Contact R1 linked to trip signal manual reset type.
00
Contact R2 linked to trip signal auto reset type.
01
Contact R2 linked to trip signal manual reset type.
10
Contact R2 linked to signal auto reset type.
11
Contact R2 linked to signal manual reset type.
System configuration
Figure 1: Scroll sequence
d) Program setting
Only function codes from 4 to 8 can be programmed.
3
High-set disabled.
00
High-set enabled.
01
Table 3: Soft switch setting
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