C&S MRN3 Manual Download Page 19

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1 9

Relay testing and commissioning

The following test instructions should help to verify the
protection relay performance before or during
commissioning of the protection system. To avoid a relay
damage and to ensure a correct relay operation, be sure
that:

the auxiliary power supply rating corresponds to the
auxiliary voltage on site.

the rated frequency and rated voltage of the relay
correspond to the plant data on site.

the voltage transformer circuits are connected to the
relay correctly.

all signal circuits and output relay circuits are
connected correctly.

6.1 Power-On

Note!

Prior to switch on the auxiliary power supply, be sure that
the auxiliary supply voltage corresponds to the rated data
on the type plate.
Switch on the auxiliary power supply to the relay and
check that the message “CSPC” appears on the display
and the self supervision alarm relay (watchdog) is
energized (Contact terminals D7 and E7 closed). It may
happen that the relay is tripped because of under- voltage
condition after power-on. (The message “TRIP” on the
display and LED L1, L2, L3 and U< light up red). An
undervoltage condition has been detected after power-
on, because no input voltages are applied to the relay. In
this case:

Press the push button <ENTER>, thus entering into
the setting mode. Now set the parameters U< and
U<< to “EXIT” to block the undervoltage functions.
After that, press the <SELECT/RESET> for app. 3 s
to reset the LEDs and “TRIP” message.

The undervoltage tripping after power on can also be
eliminated by applying three phase rated voltages
after power-on and reset the LED and “TRIP”
message.

Apply auxiliary voltage to the external blocking input
(Terminals E8/D8) to inhibit the undervoltage
functions (refer to 6.5) and press the <SELECT/
RESET> for app. 3 s to reset the LEDs and “TRIP”
message.

6.2 Testing the output relays

NOTE!

Prior to commencing this test, interrupt the trip circuit to
the circuit breaker if tripping is not desired.
By pressing the push button <TRIP> once, the display
shows the first part of the software version of the relay
(e.g. “D08-”). By pressing the push button <TRIP> twice,
the display shows the second part of the software version
of the relay (e.g. “4.01”). The software version should be
quoted in all correspondence. Pressing the <TRIP> button
once more, the display shows “PSW?”. Please enter the
correct password to proceed with the test. The message

“TRI?” will follow. Confirm this message by pressing the
push button <TRIP> again. All output relays should then
be activated and the self supervision alarm relay
(watchdog) be deenergized one after another with a time
interval of 1 second. Thereafter, reset all output relays
back to their normal positions by pressing the push button
<SELECT/RESET>.

6.3 Checking the set values

By repeatedly pressing the push button <SELECT>, all
relay set values may be checked. Set value modification
can be done with the push button <+><-> and
<ENTER>. For detailed information about that, please
refer to chapter 4.3 of the description “MR - Digital
Multifunctional relays”.
As relay input energizing quantities, three phase voltage
should be applied to MRN3 relay input circuits. Depending
on the system conditions and the voltage transformer
used, three voltages can be connected to the relay input
circuits with either star or delta connection. In case of a
star connection the phase-to-neutral voltage will be
applied to the voltage input circuits, while the phase-to-
phase voltageswill be connected to the voltage input
circuits in case of a delta connection. The voltage input
connection must be set as a parameter, and should
correspond with the actual voltage input connection:
Star connection