53
5.2.1.
Relay verification
The relay maintenance verification contains:
1. Verifying measurements
–
can be performed according to the instructions in
Section 5.3. Measurements verification.
2. Verifying output contacts operation
–
can be performed according to the
instructions in Section 5.4. Function test.
The circuit breaker tripping circuit should be disconnected from the
relay during this verification, in order to avoid unwanted operation in
the system. Interlocking signals should also be disconnected from the
relay during the verification in order to avoid dangerous situations
from occurring in the system.
3. Verifying digital inputs operation
–
can be performed according to the
instructions in Section 5.5. Digital input test.
4. If there is a reason to believe that the optical fiber or the lens sensor for the arc
protection may have been damaged, for example due to heavy arcing inside the
switch gear cubicle, correct operation of the arc detection can be verified
according to the instructions in section Arc detection test.
5.2.2.
Preventive parts replacement
When being used for real-time clock and recorded data functions, the battery should
be changed every five years. Refer to Section 4.4.3. Inserting and changing the
battery.
5.3.
Measurements verification
As most of the protection functions in the protection relay are based on the phase
currents and ground-fault current measured by the relay, it is important to verify that
the relay is measuring proper values.
This measurements verification can be performed by examining the current readings
on the display while injecting a pure sinusoidal current into the current input. If the
reading on the display corresponds to the calculated value, taking the relay accuracy
and display resolution into account, the relay is measuring proper values.
Rated current for the energizing input that is being verified is shown on the relay
label under the lower handle of the relay.
When verifying phase currents measured by the relay, the value to be shown on the
display is calculated as follows:
Value on LCD
Injected current
energizing input rated cu
CT
( )
=
rrrent
×
CT
(1)
Feeder Protection Relay
Operator's Manual - ANSI Version
REF 610
REF 610
1MRS755539
