№4 April 2012Table of contents Issue Archive
№4 April 2012Table of contents Issue Archive
№ 11 (November 2010)
Variety of offshore drilling platforms and berth-connected ships, taking into account both the scope of tasks fulfilled and the purposes intended, and design versions by simultaneously variable range of the processing equipment determine the necessity of adaptation to conditions and fields of application with regard to switchgear assemblies used within the power supply system of offshore facilities in question.
By Igor Trusov, director of Design Engineering Department NE OJSC / Alexander Morozov, head of Research & Development Division NE OJSC
Nowadays, concrete switchgear assemblies are developed for each offshore drilling platform (berth-connected or delivering ship) being under construction. Such kind of approach to the construction of power distribution and control systems in facilities under examination is supposed to be quite unprofitable in the context of an economic analysis, it requires considerable amount of product designers, developers, rearrangement of process lines and readjustment of production equipment, as well as wastes time provided for test operation and certification of electrical products supplied. It is evident, that some other technologies for arrangement of design, development and manufacture of electrical equipment intended for some unique offshore drilling platforms and berth-connected ships of the type under consideration are required for solving similar problems.
NE Open Joint Stock Company having a 17-year experience in the sphere of design and manufacture of switchgear assemblies for offshore drilling platforms and berth-connected ships and arranging their activities on the basis of a concept used while engineering switchgear assemblies offers an advanced technology for designing switchgear assemblies of universal modular cells (cabinets) of units involved. The cells’ (cabinets’) design flexibility makes it possible to apply them both in incoming sections and distribution parts used for power supply of electric consumers.
The structure and the circuit design of medium-voltage cells (cabinets) enable their application within 6-15 kV distribution systems both with an insulated and earthed neutral. Protection equipment based on application of relays allows to provide all kinds of electrical protection of the equipment, buses and cables, both discrete and digital intercommunication with the central control system and the electrical consumers’ equipment connected. Vacuum or SF6 power high-voltage circuit breakers can be optionally installed in a cell (cabinet). Universal medium-voltage cells (cabinets) should have a one-side access to minimize servicing zones and limit the total area (volume) of the space assigned for a switchgear. All bulky parts should be installed on drawout tracks to provide convenient operation of the facility.
Regarding low-voltage three-phase AC distribution systems rated for 50 Hz, up to 690 V inclusive, NE suggests to develop a line of typical cells (cabinets) for feeding electrical consumers and combining both switching and protection and control and indication equipment. Therefore, switchgear assemblies should have a modular structure, incoming and intersectional cabinets should have general unified circuit designs, and distribution sections should be assembled from the cells (cabinets) belonging to a standard product line. The standard product line should cover both fixed and withdrawable cells. Cells used for feeding the consumers of high power (rated for currents exceeding 100 A), cells for specific application as well as power supply cells for feeding of secondary group switchgear assemblies should be designed as fixed units. Special attention should be paid to the fact, that switching units should be designed as removable parts in fixed cells to facilitate the servicing. An advantage of the modular structure in switchgear assemblies rated for medium voltage (6-10 kV) and low voltage (0.38 (0.4) kV and 0.66 kV) is expressed in the possibility to provide connection of an electric consumer to any appropriate free cell (cabinet) and consumers’ process teams can be formed while connecting when switchgear assemblies rated for medium voltage (6-10 kV) and low voltage (0.38 (0.4) kV and 0.66 kV) are completed and commissioned. The actions proposed make it possible to provide considerable increase of upgrading of the power system at offshore facilities during the whole service life. At that, the structure used for feeding the consumers becomes more flexible and convenient in service.
In addition, the modular structure of switchgear assemblies rated for medium voltage (6-10 kV) and low voltage (0.38 (0.4) kV and 0.66 kV) enables to shorten the period required for elimination of a failure (defect) up to minutes. It is achieved by simple replacement of a faulty drawout cell by a similar one taken from the set of spare parts without complete de-energizing of switchgear assemblies rated for medium voltage (6-10 kV) and low voltage (0.38 (0.4) kV and 0.66 kV) and disconnection of adjacent cells designed for feeding the consumers. The structure of modular switchgear assemblies rated for medium voltage (6-10 kV) and low voltage (0.38 (0.4) kV and 0.66 kV) should provide both double-side and one-side access to arrange switchgear assemblies on the “back-to-back” principle.
The problem concerning the construction of switchgear assemblies designed for offshore drilling platforms and berth-connected ships taking into account their similar intended use and operation algorithm, but different functional content and applicable processing equipment, is suggested to be solved by means of a technology for forming and construction of a modular structure used in cells (cabinets) of a typical standard product line regarding the products under consideration. A constructive and process method elaborated for designing modular switchgear assemblies that provide application of a rational structure for connection and switching of their components, as well as technical and process compatibility in accordance with the specified requirements are assumed as a basis of the aforementioned technology. Creation of such modular system enables to arrange the necessary structure for a concrete switchgear intended for use at offshore drilling platforms by selecting and joining defined modules (modular cells or cabinets) depending on the functionality required and process equipment used. Having such system of modules at our disposal and having solved the problem of the optimization of functions required as for an offshore drilling platform, it is assumed to be possible to design a switchgear without any design expenses by integration of modular cells (cabinets) of a typical standard product line both for different processing units and various operating conditions.
The technology for forming and construction of a modular structure used in cells (cabinets) of a typical standard product line of standard switchgear assemblies is based on the following basic principals:
System approach to the development of technical equipment;
Step-by-step and sequential development and mastering of a typical standard product line of modular cells (cabinets) and base load carrying structures;
Unification and standardization of functional modular cells (cabinets);
Integration of functions on the basis of uniform modular cells (cabinets);
Focus on manufacture of Russian components used in industrial facilities and switchgear assemblies.
System approach to the development of technical equipment in accordance with the technology presented consists in the following algorithm to be used at the initial stage of switchgear development.
а) Analysis of the facility at which the switchgear assemblies are installed. The following data are to be determined while analyzing:
characteristic of application conditions of offshore drilling platforms and berth-connected ships (climatic, mechanical, presence of corrosive mediums, fire-save conditions, personnel safety conditions, availability and qualification of the personnel to be in charge of operation, maintenance and repair of electrical equipment, and other externally acting factors);
characteristic of the power supply system (sources of electric power, groups of power consumers, consumers’ load conditions, their power consumption, voltage ratings, necessity for using of start-control devices, test and diagnostic and protection equipment, requirements stated in standard technical documents).
b) Analysis of existing switchgear assemblies that have been installed and commissioned at offshore drilling platforms and berth-connected ships, and are operated according to the functions assigned. The following initial data with regard to each voltage rating must be determined while analyzing:
the list of functions performed by switchgear assemblies;
circuit designs, structural and process solutions and layout decisions that ensure the implementation of functions required;
interconnection of components installed in a switchgear to be considered as a part of the general ship’s electric power system.
c) Elaboration of a standard series of typical modular cells (cabinets) for switchgear assemblies concerning each voltage rating on the basis of functions assigned:
determination of a total amount of typical modular cells (cabinets) being representatives of each standard product line;
ranking of typical modular cells (cabinets) in order of importance of their application within the ship’s electric power system and the community of functions performed;
determination of a minimally required quantity of typical modular cells (cabinets) sufficient for the integration of the ship’s electric power system;
development of the technical documentation (namely, design and process documents) for the minimally required quantity of typical modular cells (cabinets) and base load carrying structures;
manufacture of prototype models for typical modular cells (cabinets) and base load carrying structures required for them, testing and product certification;
introduction of amendments into technical documentation on the basis of test results.
d) Elaboration of guidelines for designers from the staff of design departments involved in forming and construction of typical switchgear assemblies to be fitted with modular cells (cabinets).
e) Determination of measures taken at future stages of forming and constructing the modular structure used in cells (cabinets), that belong to typical standard product line of switchgear assemblies.
Stepwise and sequential development and mastering of a standard product line of modular cells (cabinets) and base load carrying structures used in switchgear assemblies means successive adaptation of results received at the previous stage to the next one, and stepwise solving of problems that results in elaboration of a standard product line comprising unified, standard and specific modular cells (cabinets) of switchgear assemblies, and is based on the principle of unification and standardization of functional modular cells (cabinets).
The algorism for application of this principle includes the following major stages at which the standard product line of modular cells (cabinets) is developed and created:
а) an extension stage for a standard product line of modular cells (cabinets);
b) a unification stage for a standard product line of modular cells (cabinets);
c) a standardization stage for a standard product line of modular cells (cabinets);
d) a development stage for special standard modular cells (cabinets).
Having a minimally required quantity of standard modular cells (cabinets) to be developed and used for construction of an abstract ship’s power electric power system as a base, then standard product lines fitted with other required functions are extended and design versions for each standard product line of modular cells (cabinets) that are in compliance with the specified requirements established for switchgear assemblies of some concrete offshore drilling platforms and berth-connected ships are developed. Thereby, each standard product line is supplemented with new modular cells (cabinets), and the developed cells (cabinets) are unified taking the design version of one standard modular cell (cabinet) into account. Their difference includes as follows:
output and distribution capacity applied and other indexes to functionality;
conditions for intended use;
reliability and safety indexes, protection criterion and other quality factors.
Measures taken at the stage of standardization of modular cells (cabinets) comprise the elaboration of unified modular cells (cabinets) concerning their compliance with the strictest requirements set for exposure factors, reliability and protection indexes, protection criterion and other quality factors, and the development of a standard modular cell (cabinet) for each standard product line that must start the batch production and be certified.
Versions proposed for intended application of unified models of a concrete modular cell (cabinet) and a standard modular cell (cabinet) are almost equivalent and similar, although they differ by methods used for problem solving. Two methods can be used when the switchgear for concrete offshore drilling platforms and berth-connected ships is designed:
select efficient design versions for concrete unified modular cells (cabinets), upgrade their interconnection between each other on the one hand and the protection and control cells (cabinets) on the other hand, assemble a switchgear in accordance with the factors required. Thereafter, they must be manufactured, tested and certified, if required;
take finished standard modular cells (cabinets) and use them as a base for assembling of switchgear for concrete offshore drilling platforms and berth-connected ships.
The first version is acceptable for facilities that belong to the group of a low or medium complexity. At that, more designers’ resources and more time resources are required respectively. Cost saving is determined by quality factors not excessively exceeding the required values for each concrete offshore drilling platform and berth-connected ship. The second version is characterized by tending to zero, when a tendency to requirement strengthening is exhibited. By doing so, designers’ expenditures are minimized and their errors are excluded. Therefore, when the complexity of switchgear in offshore drilling platforms and berth-connected ships is low, it is reasonable to follow the first version, and when the switchgear is complicated, the second version for application of modular cells (cabinets) is assumed to be applicable.
The development of special standard modular cells (cabinets) used for implementation of defined unique functions to be assigned for a concrete product is considered as an important stage. It is achieved by a close cooperation of the customer, developer, manufacturer and consumer at all stages of the life cycle of this modular cell (cabinet) and the switchgear designed on its base.
The basis of the function integration principle is formed, in the first place, by the unified integrating environment in the form of single-type interface communication of modular cells (cabinets) between each other and with protection and control modular cells (cabinets), in the second place, by limitation of quality of strictly defined overall and connection dimensions of cells (cabinets) and base load carrying structures, in the third place, by application of similar modular cells (cabinets) for expansion of recurring functions.
Focus on manufacture of Russian components used in industrial facilities and switchgear assemblies is determined by the state interest and political and economic significance. The principal problem being solved by the Federal Target Program “Development of the Civil Marine Engineering” for the period 2009-2016 is the elaboration of competitive domestic civil marine equipment. The problem concerning the shipbuilding development must be solved by realization of special-purpose programs as the ship’s components and materials required for realization of prospective offshore projects are manufactured not only for the shipbuilding, but also for some other branches of Russian industry. The majority of technical marine equipment needed in the market is manufactured in accordance with foreign projects. All pieces of sophisticated components are practically imported from both CIS and non-CIS countries.
Low technological potential of the Russian shipbuilding is also determined by a significant delay in the development of Russian production technologies in comparison with those in foreign countries. It results in the fact, that unit man-hours in the Russian shipbuilding industry are three to five times higher than they are abroad. In this connection, the development of advanced production technologies applied for elaboration of marine equipment, technologies and labor saving appliances, as well as processes used while manufacturing the ship’s electrical equipment is assessed as an extremely urgent issue.
The principle mentioned contemplates the maximum possible application of Russian components currently manufactured. To eliminate the problem expressed in the absence of some Russian components, there is an objective necessity to provide introduction of foreign components. This action is regarded as a coercive measure. Alongside with research and development activities performed for designing of power supply systems for offshore drilling platforms and berth-connected ships, the necessity for parallel development and manufacture of missing components followed by the replacement of foreign components with domestic ones.
With this aim in view, some issues must be reviewed while developing electric power systems, namely: lists of missing Russian components should be determined, requirements to them should be substantiated paying special attention to mass and dimensions parameters, connection dimensions and functionality appearing from the development of ship’s power supply systems, which is considered to be of great importance for the replacement of parts in future without any modifications of elements from the structure of power supply systems.
The development of technology for forming and construction of a modular structure used in cells (cabinets) of a typical standard product line of switchgear assemblies is to be divided into 2 main stages. The stages for this technology are given in Table 1.