Flipping the switch

The Natref petrol refinery, has been at the cutting edge of refining technology ever since its inception. Because the local market for heavy fuel oil is limited, Natref is designed to get the most out of crude oil. Optimising its use of the bottoms upgrading refining process, Natref can produce 70% more white product than refineries which rely on heavy fuel oil.

Automatic circuit breakers are used to protect circuits from damage in the event of a system overload. They do this by interrupting current flow if a fault is detected. Unlike a fuse, circuit breakers are reset to resume normal operation. However, they have a finite operating life and can only be reset a certain number of times.

Monitoring circuit breakers at substations is a problem for engineers since they traditionally had no way of knowing if one went off and had automatically reset. Existing on-site alarms showed the current state of the circuit breakers so, if reset, they would present as normal. Engineers were unaware of underlying issues at the substations because all circuit breakers were showing as normal, and incidents went undetected.

Being unable to detect and record faults in the system led to increased maintenance costs. To overcome problems, the plant managers at Natref engaged Omniflex to provide a way of monitoring breaker activity.

Omniflex implemented alarm annunciators monitoring circuit breaker operations, logging recorded events to 1 millisecond. The data is recorded on a built-in SD card to produce an electronic data repository for auditing purposes, improving fault finding performance.

From each monitored switch, the signal is split so it goes to the annunciator and the sequence of events record in parallel. The contact from the circuit breaker is monitored, open or close, and the annunciator traps the momentary alarm caused by the circuit breaker tripping and maps it to the alarm status. This enables engineers to see if there has been an incident, even if the circuit breaker has automatically reset.

Each substation has a GPS time synchronisation module, updating and synchronising time across the system, allowing comparisons to be made across the plant on a unified time-base.

By adopting this technology, plant managers can reduce maintenance, implement a predictive programme, replacing circuit breakers and minimising downtime. By tracking all circuit breaker trips, problem areas in the system can be identified by looking at repeated circuit breaker.

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