3
Due to the lack of wearing components
electronic devices need no preventive
maintenance. The slow ageing of the
components is not perceivable in practice.
Cleaning of the contacts of the PC board
connectors may, however, prevent possible
contact faults.
Maintenance The best results with regard to preventive
measures are obtained by controlling the
ambient temperature and the relative humidity
in order to keep these within given spec-
ifications. Further, the environment should be
free from dust and corrosive gases.
When the auxiliary voltage is connected to the
relay, the measuring relay modules perform a
self-testing program including the testing of
e.g. the contents of the microprocessors’
program memories and the displays of the
measuring modules, though the operator has
to inspect the function of the displays visually.
The matching transformers and the contacts of
the output relays are not included in the test.
The measuring relay modules also perform
self-testing in normal service situations. If a
permanent fault is detected by the self-testing,
when connecting operating voltages or in a
normal service situation, the driver circuits of
the output relays of the concerned module are
blocked, the red IRF indicator starts glowing
and the protective relay releases a self-
supervision alarm. The indicator starts glowing
and the alarm is activated approx. 1.5 minute
after the fault was discovered.
Testing In most fault situations a fault code, indicating
the nature of the fault, appears on the display
of the faulty relay module. The fault code,
which consists of one red digit and a green
code number, cannot be removed from the
display by resetting. The fault code should be
recorded and stated when ordering service.
The self-supervision system output contact of
the relay assembly operates on the circuit-
opening principle. Thus an auxiliary voltage
failure also leads to an activation of the self-
supervision alarm.
Mostly, a fault can be eliminated by changing
one of the modules of the relay assembly.
For complete operational testing of a protective
relay ordinary relay testing equipment is to be
used. Such a test includes the matching
transformers, the output relays and the
accuracy of the operating values.
If the self-supervision alarm of a protective
relay assembly is activated, the following
measures can be taken to locate the fault:
- If none of the IRF indicators of the measuring
relay modules glows, neither does the green
U
aux
indicator on the system front panel, the
power supply module of the protective relay
assembly is defective or the auxiliary voltage
supply fails. Check and repair the auxiliary
supply or change the auxiliary power module.
- If the IRF indicator of only one measuring
relay module glows, and the display of the
module shows the fault code 1004, the
concerned module or the output relay module
is defective. Change the measuring relay
module or the output relay module.
- If the IRF indicator of each measuring relay
module glows, and the fault code 1004 is
indicated on the display, the auxiliary relay
module is defective, or the flat cable between
the mother PC board and the auxiliary relay
module has got loose, or the cable terminals
are defective. Check the terminals and the
connection of the flat cable. Change the
output relay module.
- If the IRF indicator of a measuring relay
module glows and the display shows a fault
code other than 1004, the relay module is
defective. Change the module, record the
fault code and state it when ordering service.
Trouble-shooting
To Next Page
Loading...
