B kv Gas-insulated Substations

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1 kv Gas-insulated Substations The increasing demand for electrical power in cities and industrial centres requires the installation of a compact and efficient distribution and transmission network. High voltage gas-insulated substations (GIS) are ideal for such applications. The GIS is single-phase, SF 6 gasinsulated, high voltage metal enclosed switchgear, which is continuously being upgraded to the state-of-the-art. Alstom Grid has been actively involved in SF 6 technology for several decades and our GIS have been in operation worldwide since 1965 with proven success. Excellent field experience confirms the soundness of our technical concepts. Proven design concept The single-phase enclosure of the live parts, consisting of cast aluminium alloy housings, is systematically applied. Operational aspects govern the segregation of the gas compartments by barrier insulators. The busbars are always segregated at each bay. The circuit breaker is horizontally arranged and together with the mechanical operating mechanism constitutes the heart of the system. The busbars are located above the horizontal breakers providing convenient access to all important components. Telescoping busbars between the bays expedite assembly and enable implementation of planned and unplanned extensions, as well as maintenance work with minimal disruption to normal operations. The switchgear is delivered in bay modules. A light-duty hall or boom crane is sufficient for assembly and maintenance work. The height adjustable bay frames are bolted directly to the floor. The local control system cabinet can be attached directly to the switchgear, or set up separately. The open interfaces of the switchgear, operating mechanisms, instrument transformers, monitoring elements and local control system simplify the integration into various station control systems. Customer benefits Flexibility Space saving, high compactness Increased safety and reliability Modularity and adaptability Easier operation Accessibility of components GRID

2 Gas-insulated switchgear Highly experienced Alstom Grid has many years of experience in the design of gas-insulated, high voltage switchgear rated up to 800 kv. The buildings that house the switchgear can be very simple: the static and dynamic floor loads, for example, are low and a level floor is sufficient for erection. Thanks to the flexibility of the concept and the small number of single-phase modules, any substation layout can be easily designed. In case of restricted access to and within existing buildings, the switchgear is shipped as single or 3-phase components and assembled with little extra effort and cost. The compact modular system also generally allows the extension of earlier generation SF 6 switchgear. The long life of the switchgear and the extended maintenance intervals result in low lifecycle costs and high availability. The latest generation of mechanical circuit breaker operating mechanisms, with trip and reclose energy storage in compression springs, ensure constant circuit breaker readiness. 2

3 Cross section view Double busbar bay with cable feeder 1 Earthing switch 2 Busbar disconnector 3 Circuit breaker 4 Spring-operated mechanism 5 Current transformer 6 Feeder disconnector 7 Cable termination enclosure 8 Voltage transformer

4 GIS components Accessible circuit breakers The latest developments in self-blast technology are engineered into these modern circuit breakers. This keeps switching energy levels low and allows the optimised integration of spring-operated mechanisms. The customer benefits are high availability, reduced maintenance and low dynamic floor loads. A new generation of spring-operated mechanism operates the circuit breaker. Together with the breaker, it constitutes a unit and operates the three poles via a linkage. The energy required for an OPEN/CLOSE/OPEN cycle is stored permanently and free of losses by two built-in compression springs. The recuperation of the surplus closing energy and the dashpot integrated in the mechanism result in low shock switching operations. This generation of operating mechanisms is characterised by a fast rewind action and high reproducibility of switching times. The circuit breakers and operating mechanisms are easily accessible from the operator aisle for inspection, servicing and manual emergency activation in the event of an auxiliary power loss. The interrupters can slide into the operator aisle when maintenance work is required. Reliable disconnectors Disconnector modules with push-pull contacts are accommodated in standard enclosures. The three poles are mechanically linked and connected with the position indicators and the common motor drive mounted on one of the poles. They reliably switch capacitive currents, which occur when switchgear sections are energised or de-energised, as well as commutation currents caused by busbar transfers. The disconnector drives are motors with gear units and mechanically coupled auxiliary switches for control and signalling purposes. They are also equipped as standard for manual emergency operation and mechanical locking. The disconnectors have viewing windows for status and switching-position verification. Flexible, installable earthing switches Maintenance or make-proof earthing switch modules can be installed at any location in the substation. The 3-pole drive of maintenance earthing switches is of the same design as the drive used for disconnectors. For make-proof earthing switches, the drives are equipped with springs for fast make/break action. Accordingly, make proof earthing switches master closing on short circuits as well as switching Class B induced currents to IEC The standard scope of delivery includes manual emergency operation elements and mechanical locking. An insulated version of earthing switches also enables access for measurements of the main circuit. Simple bolted bars provide safe earth connections for normal service. The contact position and the status of the moving contact rod can be observed through a window in the housing. 4

5 Customised instrument transformers The ratings for voltage and current transformers are according to customer specifications for metering and protection systems. The current transformer cores are accommodated in standardised housings outside the gas compartments. The film-insulated voltage transformer cores are integrated in a sealed housing. This always constitutes a separate gas compartment. The transient overvoltages transmitted by current and voltage transformers into secondary circuits comply with the latest IEC requirements. Electronic instrument transformers have been developed as an alternative to inductive types. The current transformers are based on the Rogowski coil, the voltage transformers on the capacitive divider principle. The characteristics of these highly advanced instrumentation devices are described in a separate publication. Interconnecting components The individual SF 6 system components are assembled directly, or with the aid of connection modules. All elements have standardised flanges and symmetrical gasket grooves for the installation of the proven 3-way seals. Telescoping coupling elements with sliding sleeve joints on the conductors allow the removal and installation of components for assembly, extension and maintenance work, without dismantling further switchgear parts. Expansion bellows are provided to equalise thermal expansion movements and positioning tolerances. Interfaces & options Standard modules are available for connection of the switchgear to the high voltage grid: SF 6 air bushings for transmission lines SF 6 oil bushings for direct transformer connections Buses with solid insulation Standardised permanent or plug-in cable terminations In many cases, plug-in cable terminations make it possible to install and test cables without opening the feeder gas compartment of the switchgear. For condition monitoring purposes, Alstom Grid provides densimeters, optical arc monitors, electronic transducers and partial discharge measuring sensors. In conjunction with suitable electronic control monitoring and evaluation systems, these components allow the periodic or permanent supervision of key GIS parameters. 5

6 Layouts Double busbar Line bay with double busbar and SF 6 to air bushing Transformer bay with double busbar and cable connection Coupling bay for a double busbar arrangement Line bay with double busbar and cable connection 6

7 Layouts Single busbar with dual busbar section disconnectors Line bay with single busbar and SF 6 to air bushing Transformer bay with single busbar and cable connection Line bay with single busbar and cable connection Dual busbar section disconnectors 7

8 Technical data Rated voltage kv 145 Rated frequency Hz 50/60 Rated lightning impulse withstand voltage kv 650 Rated lightning impulse withstand voltage, across disconnector contacts kv 750 Rated power frequency withstand voltage kv 275 Rated power frequency withstand voltage, across disconnector contacts kv 315 Rated current A Rated short-circuit breaking current ka 40 Rated peak withstand current ka 100/104 Rated short-time current ka/s 40/3 Rated short-circuit making current ka 100/104 Rated operating sequence of circuit breaker O 0.3 s CO 3 min CO CO 15 s CO Min. SF6 gas operating pressure (gauge at 20 C) bar 5.5 Permissible ambient temperature C 25/+40 Enclosure single-phase Application indoor/outdoor Operating system circuit breaker spring operated Bay dimensions (W x D x H) m 1.2 x 3.4 x 2.9 Bay weight, approx. kg 3200 Other values on request Alstom Grid Worldwide Contact Centre Tel: +44 (0) GRID Grid-Products-L3-_Range _12 - EN Copyrights Alstom 2010, the Alstom logo and any alternative version thereof are trademarks and service marks of Alstom. The other names mentioned, registered or not, are the property of their respective companies. The technical and other data contained in this document are provided for Information only. Neither Alstom, its officers nor employees accept responsibility for or should be taken as making any representation or warranty (whether express or implied) as to the accuracy or compieteness of such data or the achievements of any projected performance criteria where these are indicated. No liability is accepted for any reliance placed upon the information contained in this brochure. AIstom reserves the right to revise or change these data at any time without further notice. Printed of paper made with pure ECF (Elemental Chlorine Free) ecological cellulose produced from trees grown in production forests under responsible management, and selected recycled three-layer fibres.