WO1998041730A1

WO1998041730A1 - Arrangement in a subsea production control system

Info

Publication number: WO1998041730A1
Application number: PCT/NO1998/000094
Authority: WO
Inventors: Bendix Hansen; Knut Asskildt; Anne Elisabeth Vallestad; Svein Tryti
Original assignee: Abb Research Ltd.
Priority date: 1997-03-20
Filing date: 1998-03-20
Publication date: 1998-09-24
Also published as: NO971312L; NO305042B1; NO971312D0

Abstract

The present invention relates to an arrangement in a subsea production control system, especially for production of oil and/or gas, which system comprises controllable devices necessary for the maintenance and operation of said system and being controlled through interconnected cables transferring signals and/or power to and/or between said devices, and in order to avoid the full retrieval of a subsea valve tree in case of an error in the control system and rather substitute this by component retraction or subsea maintenance and repair, it is according to the present invention suggested that said arrangement comprises means for making one or more cable harnesses and related one or more devices retrievable, especially means for making said retrieval operation possible by a remotely operated vehicle (ROV).

Description

ARRANGEMENT IN A SUBSEA PRODUCTION CONTROL SYSTEM

Field of the Invention

The present invention relates to an arrangement in a subsea production control system, especially for production of oil and/or gas, which system comprises controllable devices necessary for the maintenance and operation of said system and being controlled through interconnec- ted cables transferring signals and/or power to and/or between said devices.

Background of the Invention

As stated above, the present invention relates to subsea production control systems for oil and gas production. In such systems the controlling functions and/or the controllable devices, such as sensors, actuators, valves and control modules, are interconnected via electrical, opti- cal and/or hydraulic cables which transfer signals and power between said devices.

Errors which are due to component wear out, water ingress and a lot of other factors, may lead to so-called "fail- safe" or "controlled" shut-down of oil and/or gas production, such shut-downs being very costly due to loss in production and expensive maintenance and repair work. In order to correct or minimize such errors, precautions are taken in the design of the overall system, such that errors may be repaired by retrieving and substituting any device in error by means of a remotely operated vehicle (ROV) or by any other appropriate means, and then in the shortest possible time in order to restart the production. Additionally, several of the critical components may be made redundant. Prior Art

In current electro-hydraulic control systems the subsea control modules are usually retrievable, but the local cable harness connecting the control module to the system in order to control the elements involved therein, for example X-mas trees, manifolds or separators, is often not retrievable and not redundant. The same applies to the hydraulic valves, actuators, sensors and cables be- tween the control module and the controlled devices . In case of non-recoverable errors in components that are not individually retrievable it may be necessary for the much larger structure, to which the component (s) in error is (are) attached, for example a X-mas tree, to be retriev- ed, but this involves a very high cost and a long break in the oil and/or gas production.

From EP-0545551 -A2 (Petroleo Brasileiro) there is known a multiplexed electro-hydraulic control system for an un- derwater production installation, which system comprises inter alia a control unit arranged at the top of each X- mas tree, and wherein the control unit is connected by means of a short conduit to an electric distribution module (EDM), which connection takes place by means of a remotely controlled vehicle (ROV) .

GB-2174442-A (British Petroleum Company) discloses a subsea oil production system, wherein a complete well frame design is to be installed without any help from divers or guiding lines, but by means of a remotely operated vehicle (ROV).

N0-166458-C (Elf Aquitaine) discloses a subsea well frame, wherein the components are lowered by means of guiding poles and lines. Further, there is used a lowering and connection tool for installation of the relevant components, instead of by means of a remotely operated vehicle (ROV), which is different from the concept as suggested by the present invention. Said patent publication also discloses a module or chamber having a control unit and a multi-channel flexible loop.

NO-136112-C (Akers mek. verksted) discloses a pipe box, i.e. a "closed" structure for protecting pipes which extend between valve trees and to a riser pipe. The connection between valve trees and said pipe box is made by means of flexible pipe extensions from the valve tree, said extensions having a connection element at the end thereof, which is connected to a corresponding connection element of said pipe box. However, this pipe box does not comprise any control unit, let alone any control module.

GB-2194980-A (British Petroleum Company) discloses a control system for subsea oil production, which system can be adapted to fit into a modular three-dimensional template. The control system is installed without any help from divers or guiding lines, but by means of a remotely controlled vehicle (ROV) . The control system comprises, inter alia, a conventional control pod which is substituted by a control unit and a cable network within a closed structure. From the structure there pro- trude connection points, said connection points and connection conduits having a certain flexibility. The connection can take place by means of a remotely controlled vehicle (ROV), said control pod being adapted to be brought to top level for maintenance.

Objects of the Invention

An object of the present invention is to provide an arrangement in a subsea production control system which in a more efficient manner and at a substantially lower cost will reduce installation time, production interruption and maintenance and replacement time to a minimum. Another object of the present invention is to provide a subsea production control system wherein retraction of a X-mas tree is avoided, and rather suggest a component retraction procedure or subsea maintenance and repair.

Still another object of the present invention is to provide a subsea production control system wherein such retrieval operation of controllable devices, for example sensors, actuators, valves and control modules can take place preferably by means of a remotely operated vehicle (ROV), but without eliminating any appropriate other retraction system.

Yet another object of the present invention is to provide a modular retrievable system which is relevant for system architectures wherein the number of components that need power and/or communication is high, and wherein the communication system is based on a distributed principle, for example a field bus based system.

Another object of the present invention is to provide a subsea production control system which is specifically attractive to so-called all electric control systems based on distributed control, but which is also attrac- tive to conventional electro-hydraulic systems or systems based on subsea hydraulic power generation, it being understood that such systems could be build with horisontal X-mas trees or vertical ones.

Summary of the Invention

The above objects are achieved in an arrangement as stated in the preamble, which according to the present invention is characterized in that said arrangement comprises means for making one or more cable harnesses and related one or more devices retrievable, especially means for making said retrieval operation possible by a remotely operated vehicle (ROV) .

An appropriate embodiment of this arrangement can be to the fact that said cable harness comprises one or more mateable connection elements, especially wet mateable half-connectors allowing mating and demating in relation to corresponding half-connectors of one or more devices, so as to allow elements of said devices to be connected for necessary supply of communication and/or power, one by one or possibly in any practical combination of multiple connection.

More specifically, said cable harness may be attached to a harness carrier adapted to be transported and installed as one unit during retrieval and installation.

More specifically, said cable harness may be adapted to a harness carrier comprising one or more parking dummies for each respective mateable half-connector of a harness cable in question.

Further features and advantages achieved by the present invention will appear from the following description taken in connection with the enclosed drawings, as well as from the attached patent claims.

Brief Disclosure of the Drawings

Figures 1 and 2 show some of the principles of the pre- sent invention when applied to a typical X-mas tree in a subsea production system. The X-mas tree may be one of, say, four X-mas trees of a four-well template where free ROV access is limited to the front side of the top of the X-mas tree .

This application will only serve as an example of the principles of this invention and other more advanced examples of higher complexity, and more demanding control tasks would benefit even more from the current invention principles .

Figures 3 and 4 illustrate some possible solutions for the cable harness for local distribution of power and signals when applied to a X-mas tree. Similar approaches should be applicable for more demanding applications.

Detailed Description of Embodiments

In connection with Figures 1-4 there is illustrated an embodiment of an arrangement according to the present invention, which arrangement is used in a subsea produc- tion control system, especially for production of oil and/or gas. Such a system comprises controllable devices necessary for the maintenance and operation of said system and being controlled through interconnected cables transferring signals and/or power to and/or between said devices.

As discussed in the preamble, one of the major tasks of the present invention is to be able to replace such devices and possibly a part of or the complete cable net- work associated with a subsea production valve tree, and then specifically by means of a remotely operated vehicle (ROV) . In other words, the invention devises an arrangement comprising means for making one or more cable harnesses and related one or more devices retrievable, espe- cially by means for making said retrieval operation possible by an ROV.

Figure 1 is a top view and Figure 2 is a front view of an embodiment according to the present invention, comprising a Control System Package, CSP, consisting of the control module 1, the harness carrier 2, cables and connectors and parking dummies. In this application the control module 1 is much simpler than its equivanlent in a conventional electro-hydraulic control system and may only consist of one or two printed circuit boards, and the normally nitrogen filled 1 bar enclosed control module 1 will therefore become a small device.

According to the invention the control module 1 , which is the active part, remains essentially identical for all applications while the harness carrier 2 with associated harness and half-connectors, that are all passive, are tailored to each application.

The control module 1 may perform or be prepared for the following main functions:

1. A long distance modem for communication with the (distant) topside installation and other (distant) subsea installations .

2. A local (short distance) serial drop (fieldbus) unit managing (mastering) all controllable devices on the X- mas tree (or other localized set of devices).

3. A local power supply to stabilize local power dis- tribution.

In some cases the funtion 3. may be distributed to each local user, reducing the size of the control module 1 even further, such an arrangement also being devised according the the present invention.

It may also be attractive in some cases to include the electronics of the control module 1 into one of the devices on the X-mas tree that is equipped with a (retriev- able) electronics enclosure for its own functions anyway. Such an arrangement is according to the present invention as well, but no drawings are presented. The control module 1 and the harness carrier 2 can be installed or de-installed independently by ROV. The harness carrier 2 is lowered vertically onto its guiding posts 3 during installation and the control module 1 and the connectors 9 and 10 each consisting of one half-connector fixed to the control module 1 and one half-connector fixed to the harness carrier 2, will automatically mate during the installation or de-installation procedure. Alternatively, the cable harness may be connected to the control module 1 by ROV, i.e. with no automatic mating or de-mating process during intallation or de-installation.

The control module 1 and the harness carrier 2 may be placed under a protection plate 12 which is often a part of the load carrying structure of the X-mas tree. Access is ensured via suitable hatchways or similar structures that can be opened and closed by the ROV.

The connector 9 connects the control module 1 to different devices on the X-mas tree to be controlled and/or monitored via the cable harness 11. The connector 10 is duplicated and connects the control module 1 to the power and signal lines of the umbilical via two separate cab- les, 13 and 14.

These duplicated cables may be permanently attached to the connector 10, in which case the other ends of the cables are ROV mated to umbilical extension half-connec- tor 10A. They may alternatively be part of the template signal and power distribution cabling system and not permanently attached to the harness carrier 2 (e.g. during ROV transportation of the harness carrier) . In this case the control module half-connector of 10 is mated to its cable half-connector by ROV after the control module 1 is ROV installed, or vice versa for de-mating. Then the half-connector 10A may simply constitute a cable guiding arrangement .

Parking dummies 4, 5, 6, 7 and 8 are attached to the harness carrier 2 and all the half-connectors of the cable harness 11 are inserted into these parking dummies during ROV transportation of the harness carrier 2. Mating and de-mating is done by ROV, preferably one by one, in the following manner.

The ROV swims into position and fixes itself to the X-mas tree in a suitable position for reaching all the half- connectors that are accessible from the front. The arm of the ROV grabs the first cable harness half-connector situated in parking dummy 4, moves the connector to the corresponding device half-connector 4A and mates the two. Then the ROV moves its arm to the next cable half-connector in its parking dummy and moves and mates it to its counterpart device half-connector, and so on, until the final half-connector in parking dummy 8 is mated to 8A. Then the ROV moves to a suitable position for reaching the remaining half-connectors in parking dummies 5, 6 and 6 that are accessible from the top of the X-mas tree after having opened possible hatchways or the like. The mating of half-connectors in the dummies 5, 6 and 7 to their corresponding device half-connectors 5A, 6A and 7A are performed one by one as above.

The de-installation procedures are performed in the reverse order.

One or more of the controllable devices on the X-mas tree may not be retrievable and the associated connecting cable may be a pigtail sealed to the device. For instance the sensor connectors 6A and 7A may be pigtailed to a sensor, and it may then be simpler to let the parking dummies 6 and 7 be substituted by the half-connectors 6A and 7A arranged so that they are automatically mated or de-mated, during installation or de-installation of the harness carrier 2, to the corresponding cable harness half-connectors that are fixed in relation to the harness carrier in this case.

The local cable harness may also be equipped with one or more spare half-connectors placed in their own parking dummies for repair or for future or non-planned use . These are not shown in the Figures .

The Figures 3 and 4 show a few possible electrical configurations of the local cable harness. Both figures illustrate how the control module 101, the N devices, #1 , #2, ... #N, and one or more 'spare' half-connectors are interconnected. The control module 101 will often master the bus and the devices 'hooked up' to it, but different schemes are possible depending on which fieldbus ' standard' is chosen. All the N devices and the 'spare' connectors are hooked up to the bus cable 104 via spurs 109 that are electrically connected in 'Y-splices' 106 wire by wire, as shown in the details of Figure 3.

The maximum physical length of such a spur 109 is usually limited in most fieldbus 'standards', being several meters at low speed (in the order of kbit/s) to essentially 0 at high speed (in the order of Mbit/s). This and other factors may motivate the designer to move the Y- splice close to the device, for instance into the cable harness half-connector (not shown in the Figures) or even into the device itself, as shown in Figure 4.

The reliability of Y-splices is from time to time questioned, when being part of a subsea cable harness. This fact may as well motivate the designer to move the splices 106 into the device as in Figure 4, however, at the expense of more connectors and or more pins in each connector. In Figure 4 there are shown two connectors 107 and 108 per device, each of the same type as in Figure 3. The two connectors may possibly be collapsed into one connector with twice as many pins, of course.

The configuration with two connectors 107 and 108 per device opens up for a different way of retrieving the cable harness, compared with what has been described above, in that the cable 104A between two devices can be installed or de-installed independently of the others. The corresponding parking dummies may then be fixed to the harness carrier or to a simple tool carried by the ROV. This may in some cases involve the advantage of easy exchange of a faulty cable/connector/device.

The common bus cable 104 may consist of different numbers of single wires depending on the application and on the fieldbus 'standard' chosen. Two wires are possible in a few 'standards' where signal is superimposed onto power lines, whereas four wires are applicable in all fieldbus 'standards' (separate signal and AC or DC power). Five wires may be attractive when (high power) 3-phase AC power is needed in one or more devices in addition to signal superimposed on (low power) DC or AC power lines. Even 7 wires may be attractive when there are reasons to separate the (low power) DC needed for electronics from the AC lines in addition to separate signal lines. Other combinations may of course be possible.

The dashed 'return cable' 105, in Figures 3 and 4 may have certain advantages with respect to error tolerance. Suppose the bus transceiver in the control module is duplicated such that one transceiver can drive the bus 104 and the other can drive bus 105 if errors in devices and/or in the bus cable itself occur. In Figure 3 for instance an open circuit error in the bus cable between devices #1 and §2 would imply that all communications to devices §2 to #N would stop if only one transceiver and no 'return cable' were implemented. If, however, the 'return cable' and a second transceiver are available, the system can be reconfigured such that communication to all devices are re-established without any external intervention.

In Figur 4 the 'return line' 105 and the dual transceiver may ensure, by careful design, that both an open and a short circuit error in a cable segment between any two devices can be taken care of without loss of communication (or supply of power), according to this invention.

It is to be understood that the invention also can be implemented in connection with other types of control systems than what has been discussed in connection with the specific embodiment illustrated in connection with Figures 1-4.

The invention will be most relevant for system architec- tures wherein the number of components that need power and/or communication, is high and/or wherein the communication system is based on a distributed principle, e.g. a field bus based system. The present arrangement is specifically applicable in connection with all electric con- trol systems based on distributed control.

However, it is to be understood that the invention may also find application in connection with conventional electro-hydraulic systems or systems based on subsea hydraulic power generation, possibly involving local hydraulic power generators, if such systems are based on a distributed fieldbus architecture and/or for systems build with horisontal X-mas trees that are much more expensive to retrieve than vertical ones. The invention also finds application in deepwater applications, wherein the cost associated with retrieving of large modules is specifically high. Specifically in cases based on all-electric control systems based on distributed control, the arrangement according to the present invention gives instruction for how to make the cable harness or harnesses and the related devices, or parts thereof, that are connected to the harness, retrievable in a most efficient manner. More specifically the invention defines means and principles which make the harness and the control module retrievable, preferably by ROV.

The cable harness, harness carrier, connectors and control module may be arranged in any degree of redundancy and any combination of conductor routing to achieve this redundancy and the principles described are claimed to be equally applicable at least in principle. (Of course, the more redundancy that is to be implemented the higher the complexity and the more practical difficulties with the retrieving process will result. )

The cable harness may, as non-limiting examples, be configured in the following variety of ways:

1. In case of electrical signalling and electrical power distribution, the power and signals may (for some fieldbus protocols) share the same pair of wires (2-wire bus configuration) .

2. In case of electrical signalling and electrical power distribution, the power and signals may be carried on separate wires ( 4-wire or 5-wire or even 7-wire bus configuration) .

3. Configuration as in 1. and 2. , the necessary Y- splices may be placed internal of the device that shall be connected to the bus or in the bus cable itself, as shown in Figures 3 and 4. 4. configuration as in 1. to 4., the bus wires may be terminated in the "last" component or may be taken "back" to the control module (which is the master of the field- bus in question), as shown in Figures 3 and 4.

5. Configuration as in 1. and 2., the cables may be housed in a pressure compensated oil-filled tube.

6. The cable bus may be configured in a physical ring from one device to the next (with the Y-splice internal to the device) and with two connectors per device as shown in Figure 4.

7. The cable harness may be configured as a point-to- point "star" type power and signal distribution (as is usual in current electro-hydraulic control systems). This is not shown in any Figure. In this case the connections between the control module and the harness may be a multi pin connector (with as many pins as there are single wires to all the devices in the "star") or separate connectors for each of the device cables. Automatic stabbing of connector (s) during installation or retrieval, or ROV mating or demating may both be feasible. This "star" configuration may be used both for non-fieldbus and fieldbus architectures. In case of fieldbus the Y-splices of the bus may be internal to the control module, in which case the external "star-arms or -cables" are called spurs (in fieldbus terminology) and their maximum length differs in different fieldbus protocols and decreases normally with increasing bit-rate of the protocol.

8. The power lines of the harness may be electrical or hydraulical, and the signal lines may be electrical or optical, and all combinations will be possible for field- bus and non-fieldbus architectures.

9. Configuration as in any of 1. to 8., the cable har- ness may be made in any degree of redundancy.

10. The configurations 1. to 9. may be intermixed.

11. Communication and power between control modules or between a (distant) topside installation and control modules may as well be obtained in a variety of ways including electric or optic signal distribution in a star or a ring based configuration. For this invention it is sufficient to state that the control module is equipped with one or more wet mateable half-connectors for the purpose of "global" signal and power distribution. The corresponding connections are as well made by ROV or by automatic mating or demating during mounting or demoun- ting of the control module.

It may be advantageous to incorporate cable guiding/attachment structures on the relevant structures so that the cable harness is placed in a determined and desirable position. This may be necessary to ensure ROV access to other parts of the relevant structures (e.g. for device retrieval) without interfering with the cable harness.

Each of the features 1 to 11 , possibly except feature 7, supports a system approach that leaves the control module with a fixed (once the degree of redundancy has been chosen) and small number of half-connectors irrespective of the number of devices that shall be controlled and monitored. Hence, it is possible to obtain a control module that is identical for all applications. In all- electric control systems the control module then becomes a small unit that can be retrieved, installed and carried by a work class ROV. The harness and harness carrier will usually need to be tailored to the application.

Claims

P a t e n t c l a i m s

1. Arrangement in a subsea production control system, especially for production of oil and/or gas, which system comprises controllable devices necessary for the maintenance and operation of said system and being controlled through interconnected cables transferring signals and/or power to and/or between said devices, c h a r a c t e r i z e d i n that said arrangement comprises means for making one or more cable harnesses and related one or more devices retrievable, especially means for making said retrieval operation possible by a remotely operated vehicle (ROV) .

2. Arrangement as claimed in claim 1 , c h a r a c t e r i z e d i n that said cable harness comprises one or more mateable connection elements, especially wet mateable half-connectors allowing mating and demating in relation to corresponding half-connectors of one or more devices, so as to allow elements of said devices to be connected for necessary supply of communication and/or power, one by one or possibly in any practical combination of multiple connection.

3. Arrangement as claimed in claim 1 or 2, c h a r a c t e r i z e d i n that said cable harness is attached to a harness carrier adapted to be transported and installed as one unit during retrieval and installation.

4. Arrangement as claimed in claim 1, 2 or 3, c h a r a c t e r i z e d i n that said cable harness is adapted to a harness carrier comprising one or more parking dummies for each respective mateable half-connec- tor of a harness cable in question.

5. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that said harness carrier is provided with installation means matching with corresponding receiving means on the structure in ques- tion, for example guiding posts and/or other appropriate guiding/attachment devices, for installation or retrieval by ROV or possibly wirelines.

6. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that said arrangement comprises at least one control module being equipped with at least one half-connector fixed to the control module and being adapted for automatically mating or demating the corresponding harness half-connector(s) fixed to the harness carrier unit during mounting or demounting of the control module on its guiding posts or equivalent.

7. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that one or more cable harness half-connectors to be connected or de-connected to the half-connectors of the corresponding control module, is adapted for being placed in one or more relevant parking dummies fixed on the harness carrier, and connected or de-connected to the corresponding half-connector (s) of the control module by an ROV.

8. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that said arrangement comprises stabbing process/guide post assemblies adapted for the harness carrier and the control module to be retrieved independently or as one integrated unit, poss- ibly depending on the detection of an error which has occured in said unit.

9. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that said retrievable cable harness comprises one or more devices which are classified as non-retrievable, said device comprising for example a pigtail sealed to the device and ending in a half-connector at the other end, said half-connector being permanently fixed to the relevant subsea structure, e.g. the X-mas tree, an ROV, then, mating the correspond- ing harness half-connector to said pigtail half-connector after having demated the harness half-connector from its parking dummy fixed to the harness carrier, and vice versa for demating the two half-connectors.

10. Arrangement as claimed in claim 9, c h a r a c t e r i z e d i n that said arrangement comprises a dedicated parking dummy fixed to the relevant subsea structure, e.g. the X-mas tree, in the proximity of a harness carrier, so that an ROV can mate the pigtail half-connector to the harness half-connector that is permanently fixed to the harness carrier in this case, after having demated the pigtail half-connector from its parking dummy.

11. Arrangement as claimed in claim 9, c h a r a c t e r i z e d i n that said arrangement comprises a pigtail half-connector which is fixed to the relevant subsea structure, such that the harness half- connector automatically mates or demates during mounting or demounting of the harness carrier.

12. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that said arrangement comprising one or more cable harnesses comprise spare half-connectors fixed to the harness carrier unit, such that an ROV can connect devices that are normally not hooked up to or planned for the system, such spare half- connectors also being used for repair of a faulty device or device connection, all of which being adapted to the relevant fieldbus protocol .

13. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the arrangement comprises at least one cable harness, at least one har- ness carrier, at least one connector and control module, all of which may be arranged in any degree of reduncancy and any combination of conductor routing for achieving such redundancy .

14. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the arrangement is adapted to an all-electric control system based on distributed control, or possibly adapted to a conventional electro-hydraulic system based on subsea hydraulic power generation, possibly based on a distributed fieldbus architecture.

15. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the arrangement is adapted to a control system based on electrical signalling and electrical power distribution, the power and signals sharing the same pair of wires in a 2-wire bus configuration, possibly the power and signals being carried on separate wire pairs in a 4-wire bus configuration, or even three wires for 3-phase power distribution and two wires for signals.

16. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that in case of electri- cal signalling and electrical power distribution said arrangement comprises Y-splices placed internal of said devices to be connected to the bus, or in the bus cable itself, or in the cable harness half-connectors said bus wires possibly being terminated in the last component or being routed back to said control module which possibly is the master of the fieldbus in question.

17. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the arrangement comprises cables which are housed in a pressure compensated oil-filled tube.

18. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that said arrangement comprises a cable bus configured in a physical ring from device to the next, and possibly comprises Y-splice in- ternal to said device and having preferably two connectors per device.

19. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the arrangement comprises a control system communicating through a cable harness configured as a point-to-point "star" type power and signal distribution system, the connections between the control module and the harness being provided by a multi-pin connector wherein the number of pins are adapted to the number of single wires to all devices included in said "star" or possibly comprising separate connectors for each of the device cables.

20. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that said arrangement comprises a control system communicating with a "star" configuration which is adapted to be used both for non- fieldbus and fieldbus architectures, the fieldbus architecture defining Y-splices of the bus to be arranged internal of said control module, in which case the arms or cables of said "stars", also called "spurs", and their maximum length, will differ in different fieldbus protocols and normally decrease with increasing bit-rate of the protocol .

21. Arrangement as claimed in any of the preceding claims, c h a r a c t e r i z e d i n that the arrangement comprises at least one control module with a fixed and small number of half-connectors irrespective of the number of devices which are to be controlled and monitored, for thereby achieving a standard control module for a large number of applications, substantially based on the degree of redundancy related to such plurality of appli- cations.