Petrokimia Gresik: ABB PLC repair

Background

The electrical team of the coal unit used an ABB system to monitor 6 kV and 20 kV switchgear. The PLC panel had been installed around 2010 and had not worked since 2018. The CPU battery was faulty, the engineering workstation (EWS) was no longer in the control room and the operator workstation (OWS) was off.

Existing system

Two redundant ABB AC 800F controllers with ABB Freelance, I/O, Ethernet, serial and Profibus DP communication modules, an electrical mimic panel, Schneider PowerLogic ION6200 power meters, ABB UniGear switchgear and ABB protection relays.

Scope of work

• Controller troubleshooting. Each CPU was tested on its own, together with the redundant configuration, power supply, communication modules and field connections. Both CPUs still worked.

• Communication module failure. Tracing found a short circuit at a terminal connection and two damaged communication modules.

• EWS recovery. The engineering software was reinstalled. The existing backup could not be downloaded because the controller firmware had been upgraded, so a newer ABB Freelance version was installed on the EWS. The old EWS hard disk had failed, so the last program was no longer available.

• Re-programming. Review of the existing backup, re-programming of equipment that was out of date, tags that did not appear, and checks of process logic and display mapping.

• Workstation recovery. The EWS and OWS functions were combined on one workstation because the old hardware was faulty.

• Power meter communication. Modbus query and response tests on each Schneider ION6200, communication address checks, and identification of meters that were off or not communicating.

• 6 kV bus I and II. Breaker status, digital power meters, communication status and load measurement, cross-checked between field equipment and the HMI. Most measurements returned to the operation page, as long as the field power meter still worked.

• Feeder monitoring. The system shows generator power, Plant II, Plant III, the outgoing transformer, 6 kV feeders, bus measurements and breaker status again.

• Switchgear and protection interface. From site photos, checks of the ABB UniGear switchgear, ABB REF610 protection relays, medium-voltage feeder panels, the mimic panel, field terminations and communication interfaces.