The recommended periodical testing interval is between three and five years, depending on the following factors.
Installation environment
REX615 relays which are installed in harsh environments, we recommend applying the three years interval. The harsh conditions can be due to temperatures and/or humidity near to the maximum specified for the product, or it can be due to dust, salt, chemicals, or other corrosive agents.
Infrequent operations
If the relay has performed very few operations during the observation period, which is typical for spare feeders, we recommend applying the three years periodical testing interval. The long inoperative time is not typically a problem for the relay, if the auxiliary power is turned on continuously, but it might be more problematic for the circuit breaker operation mechanism.
Frequent operations
When the relay performs several operations during the observation period, specially initiated by the protection functions, and the relay’s performance during the faults are analyzed we recommend applying the five years periodical testing interval. The analyzing can be based on relay’s events, fault records and disturbance records.
Utilization of relay’s external and internal supervision features
REX615 contains several supervision features, both for relay’s internal functionality and for relay’s external circuitry. For external circuitry there are many supervision features. Whether the features are activated depends on the relay configuration and settings. It’s highly recommended to take an advantage of these features, since they will cover a large part of the complete protection circuitry offering continuous supervision. The following features are included:
- Trip (and close) coil supervision
- Circuit breaker condition monitoring
- Motor operated disconnector supervision
- Current transformer secondary circuit supervision
- Fuse failure supervision
- Protection (point-to-point) communication supervision
- Station communication supervision
When in use and configured correctly, these supervision features will activate events and alarms, both on local HMI and on remote systems.
The protection relay’s self-supervision function monitors the relay’s performance and indicates possible problems on two levels: internal warnings and internal faults. Internal warnings effects only the concerned part of the relay’s functionality, for other parts the relay will continue normal operation. The internal warnings are indicated as events and as alarms, if enabled in the configuration, on the HMI and on remote systems.
In case of internal faults, the relay operation will be disabled, IRF output relay will be de-energized and corresponding events and alarms issued. REX615 has a mechanism for recovering from internal fault situation by activating a controlled restart of the relay. Depending on the root cause, the restart can happen several times and if successfully the relay will resume full operational status.
When these supervision features are utilized and actions taken in case any of the supervision functions activates itself, we recommend applying the five years periodic testing interval.