It was a SMART wellhead platform controlled by a PLY. The platform included a HP & LB power system for utilizing 6. Xv power Ewing supplied to the platform through subset power cable. Additionally, the HP switchgear system also supplied power to the subset cable connected RSI-1 5 platform. The subset power cable system was designed such that, a 6. Xv subset cable would terminate in the incomer of the HP switchgear system. And then from the outgoing switchgear, a separate subset cable would carry power to RSI-1 5 platform.
The HP switchgear system would require a numerical relay system for providing Control & Monitoring on the wellhead platform. There was also a requirement for serial communication between the relay system and the PLY based littoral control system. The client had envisaged the requirement of monitoring the status of the switchgear and hence only a serial communication link was provided between the systems. The client had, at the bidding stage, provided a basic cause and effect chart containing the philosophy of carrying out a shutdown on the SMART wellhead.
During the engineering stage of the project, it was our company’s responsibility to carry out a safety study, to finalize on and get approval of the shutdown philosophy of the safety ; control system of the platform. This Is carried out In accordance with the safety guldens provided by the client. As I was in-charge of the control ; safety system, I was part of the study. During the study, I noticed that there was an issue that had been overlooked in the shutdown of power systems.
As per the client’s documents, when an emergency alarm is triggered on RSI-1 6 platform, the power system of RSI-1 6 is shutdown. Since both platforms had their own control systems, the Individual control system was responsible for shutting down the power supply of their respective platform. And this was being implemented by switching off the outgoing power supply from the HP switchgear system to their respective platform transformer system. So since both the control systems were standalone, the shutdown philosophy was also individual to each platform.
But because power to RSI-1 5 platform was being transferred from RSI-16 platform, there were conditions defined for the shutdown of the power flowing between the platforms.. And also as the power system between RSI-16 to RSI-1 5 had switch, a protection between the platforms had not been identified by the client. I brought up this concern to my superiors attention; They had agreed with my opinion that even though the client had not specifically asked for such a requirement, to keep p with the safety guidelines we would require to provide such a protection.
This special condition was then informed and discussed with the client. The client on noticing the forethought, and that this protection would be critical and beneficial to the safety system gave the go ahead to implement our proposal. I was asked to identify a method that would enable and implement such a protection with minimal additional costs and technically viable option. C. E. 2. 3 PERSONAL ENGINEERING ACTIVITY C. E. 2. 3. 1 Before commencement of the activity, I made a plan outlining a sequence of steps to e taken, and discussed the same with my superiors so get their inputs and make them aware of the timeliness.
My tasks involved identifying all the causes for which the differential protection would be required, method of implementing the protection and getting the approval on the philosophy. The first task I listed was to determine the communication mode that would be utilized for the safety protection signals. Although a serial communication between the control & power system had already been envisaged as per the communication system plan, the client’s safety guidelines denied the use of serial immunization for safety related signal transfer.
Hence my next option was to consider an additional signal transfer between the control and power system through a dedicated standard pair cable. This was a robust solution which complied with the safety guidelines. There were already signals being transferred from the control system to power system that would be used to control the internal switch gears of the platform. And hence an addition could be easily accommodated with limited increment in the engineering for hardware expansion. C. E. 2. 3. 2 The second step required me to identify signals from the numerical relay system that loud be used to implement the protection.
On reading through the numerical relay catalogues, I identified that the numerical relay detects the breaker status signal, which could be used for the purpose. The breaker status signal would be active when the respective breaker in the switchgear is opened. Also each numerical relay had the facility to use inputs to configure the action of the particular breaker. With the information I had learnt, I had an input output list prepared to indicate the signals that would be utilized to implement the protection.
An output signal from the erasers in RSI-16 platform, indicating the status of the breaker, would be utilized as an input to the breaker at RSI-1 5 platform. Was thinking of writing more if required, taking some inputs from you. ; C. E. 2. 3. 3 Once I had the list of causes and the respective inputs and outputs identified, I noticed that the earlier determined hardware connection method would not be able to implement the differential protection for all causes. This can be attributed to the was lost, the differential protection will not be executed.
Although during communication loss between platforms, the control systems in themselves still kept heir respective platforms safe from any internal shutdown causes, but since the control system’s had no knowledge of the status of the other platform, it will not be able to implement the required protection. This led me to revisit the communication mode that I had earlier decided upon. Now I had to come up with a method that would bypass the present communication network units whilst still providing a dedicated communication between the power systems. I decided to use the envisaged optical fiber communication link.
At this stage, On reading the client requirements for the numerical relays, I noted that for this project it was required to apply optical fiber enabled numerical relays. This was a huge advantage and benefit, else we would have had to provide optical converters at both the power supply systems and implement a copper cable communication between the converter and numerical relays. This method would keep the differential protection independent of the communication units presently being utilized between the control systems, and maintain a dedicated link for the safety protection.
The client requirement was to provide an optical fiber cable having 24 cores, from which only 6 cores were required for control system communication. This enabled me to use a people of cores from the 18 spare available for use. . C. E. 2. 3. 4 After having identified the communication mode and listed the causes, my next task was to realize the above concept. And to realize the dedicated communication link and still be able to use to optical fiber subset communication link, I had to understand the planned communication architecture.
The communication architecture indicated that the subset cable that contained both the power and optical fiber link would have it’s first termination at special Junction box. On reading about these Junction boxes from vendor catalogues, I noted that their purpose was to low for the termination of the power cables coming from subset. But the optical fiber link would only be allowed to pass through the box after separation from the subset cable. And to maintain a separate optical cable for subset and on the platform, we would then terminate this cable into a temporary communication termination box.
After which an optical fiber cable will be laid between the temporary communication termination box and the main communication unit. From the architecture I found that there were two ways of connecting the optical fiber cable from the power system through to the subset cable link. I decided that an additional optical fiber cable from the power system needs to be laid to the temporary communication termination box close to the subset Junction box. The individual cores of the optical fiber link from power system will then be spliced with the spare cores available in the subset cable link.
This implementation provided independence from the communication unit. Though if the power optical cable used for power protection was spliced in the communication unit, it would not be dependent on power loss in the communication unit, since the splicing cassettes for the optical cable do not require power. The method benefited from the independence of the optical cable used for power in the communication system unit was required, it would not affect the differential protection between the power systems. C. E. 2. 3. Finally the complete proposal including the cause and effect chart, the communication architecture modification, configuration required in the numerical relays and the final control ; shutdown philosophy was brought out to my team and superiors. Once it was approved internally, I was asked to explain the same to the client and third party in-charge of the safety study. The client having been informed of the steps at every stage were pleased with our progress. And the third party team did a run through on the causes and effects to check if any safety requirements have been overlooked.
After this thorough investigation, the procedure and method was finalized for implementation. C. E. 2. 4 SUMMARY 2. 4. 1 The control and emergency shutdown philosophy on any offshore platform is very important in maintaining both continuous production and safety of human personnel and assets. Hence the implementation of the differential protection in the power yester, although not having been indicated by the client, was critical to maintain the safety standards of the offshore environment.
Therefore the client was very happy with our company’s forethought in having noticed and suggesting an implementation philosophy. We executed this successfully with complete safety checks and in line loop checks by the Client though the third Party investigator. I was recognized for being the lead of this initiative as a part of the Project team. Picks required 1. Communication architecture 2. Cause & Effect chart 3. Modified communication architecture 4. Maybe numerical relays and subset cable etc.