My Bizarre Experiences

Experience – 1

7 o’ Clock Shut down Syndrome

This happened while I was working at an Off Shore Oil Processing platform. There are three gas turbine driven generating units, for powering the platform, with two of them are running in parallel and the third one in stand by. Suddenly the platform started experiencing a power shut down at 7 O’ Clock in the morning even though there was no process upset or starting or stopping of any equipment. It was observed that this was happening only when the third unit is running in parallel with one of the other units. The control system of the unit is checked thoroughly for any fault but nothing abnormal is noticed. On close observation, it is found that the third unit is tripping due to fuel system malfunction and through the full load on the other unit, causing the second unit also to trip causing total black out. The load shedding unit could not get enough time to limit the load and avoid total shut down.

All the process were closely monitored and operators were advised to avoid starting/stopping of any load from 6 am to 8 am. Still it is found that the unit is tripping at 7 am. The platform is the central location from where personals are transported by helicopter to well head platforms for operation and maintenance in the morning and brought back in the evening. The operation starts at 7 am and the communication system is switched on at that time.

Operators in the power control room are advised to be vigil while the communication system is switched on. The reported there is a fluctuation in the fuel supply-demand indicator while the communication unit is switched on and the unit trips there after. On inspection it is found that the communication unit and the third GT genset control unit are connected to a common battery bank. The other two units are supplied from another battery bank. While the communication unit is switched on, the radio signal travels to the GT control unit also through the DC Power cable and caused disturbances in fuel control system and subsequent shut down.

The GT control and communication power supplies were, then, isolated and the signal path is interrupted so that the signal cannot reach the GT control through the power cable. Also earthing of all equipments in the control panel is redone. The problem never recurred after that!