CAPÍTULO I. APROXIMACIÓN CONTEXTUAL AL PATRIMONIO CULTURAL
1.5 Comentarios finales
Due to the limited let-through current of the HRC fuse, block-type C.T.s with lower thermal rating can be used. Depending on the protection scheme used, C.T.s with one or two secondary windings are installed.
All commonly used feeder cables up to 300 mm2 can be terminated and connect-
ed at the lower C.T. terminals. Grounding switches or surge-voltage limiters are installed optionally below the current transformers.
Reduced-voltage nonreversing (RVNR) with starter (reactor starting)
Full-voltage nonreversing (FVNR)
Reduced-voltage nonreversing (RVNR) with external reactor autotransformer ”Korndorffer Method“
Air-insulated Switchgear
Type 8BK30
Siemens Power Engineering Guide · Transmission & Distribution 2/19 Interlocking system
Contactor, truck and low-voltage plugs are integrated into the interlocking system to guarantee the following safeguards:
■The truck cannot be moved into the ”Connected“ position before the LV plug is inserted.
■The LV plug cannot be disconnected with the truck in the ”Connected“ posi- tion.
■The truck cannot be moved with the contactor in the ON position.
■The contactor cannot be operated with the truck in any other but the locked ”Connected“ or ”Disconnected/Test“ position.
■The truck cannot be brought into the ”Connected“ position with the ground- ing switch engaged.
■The grounding switch cannot be en- gaged with the truck in the ”Connect- ed“ position.
Degrees o protection
Degree of protection IP 4X:
In the ”Connected“ and the ”Disconnect- ed/Test“ positions of the truck, the starter is totally protected against contact with live parts with objects larger than 1 mm in diameter.
Optionally, the starters can be protected against harmful internal deposits of dust and against dripping or spray water in the ”Operating“ position (IP 51).
Installation
Identical to the procedures outlined for 8BK20 switchgear. Only the HRC fuses are shipped outside the enclosure, separately packed.
Fig. 23: Cross section through switchgear type 8BK30
Air-insulated Switchgear
Type 8BK30
Fig. 24 Rated voltage Width Height Depth Approx. weight incl. contactor 3.6Weights and dimensions
2 x 400 2050 1650 700 7.2 12 [kV] [mm] [mm] [mm] [kg] 2 x 400 2050 1650 700 2 x 400 2050 1650 700
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Air-insulated Switchgear
Type 8BK40
Metal-clad switchgear 8BK40,
air-insulated
■From 7.2 to 17.5 kV■Single- and double-busbar (back-to-back or face-to-face)
■Air-insulated
■Type-tested
■Metal-enclosed
■Metal-clad
■Withdrawable vacuum breaker
■For indoor installation
Specific features
■General-purpose switchgear for rated feeder/busbar current up to 5000 A and short-circuit breaking current up to 63 kA
■Circuit breaker mounted on horizontally moving truck
■Cable connections from front
Safety of operating and maintenance personnel
■All switching operations behind closed doors
■Positive and robust mechanical interlocks
■Complete protection against contact with live parts
■Line test with breaker inserted (option)
■Maintenancefree vacuum circuit breaker
Tolerance to environment
■Sealed metal enclosure with optional gaskets
■Complete corrosion protection and tropi- calization of all parts
■Vacuum-potted ribbed epoxy-insulators with high tracking resistance
Generator vacuum circuit breaker panel ■Suitable for use in steam, gas-turbine,
hydro and pumped-storage power plants
■Suitable for use in horizontal, L-shaped or vertical generator lead routing
Fig. 26: Cross section through type 8BK40 generator panel
Fig. 25: Metal-clad switchgear type 8BK40 with vacuum circuit breaker 3AH (inter-cubicle partition removed)
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Air-insulated Switchgear
Type 8BK40
General description
8BK40 switchboards consist of metal-clad cubicles of air-insulated switchgear with withdrawable vacuum circuit breakers. The breaker truck is fully interlocked with the interrupter and the stationary cubicle. It is manually moved in horizontal direction from the ”Connected“ position behind the closed front door and without the use of auxiliary equipment. A fully isolated low- voltage compartment is integrated. All commonly used feeder circuits and aux- iliary devices are available.
The switchgear cubicles and interrupters are factory-assembled and type-tested as per applicable standards.
Stationary part
The cubicle is built as a self-supporting structure, bolted together from rolled gal- vanized steel sheets and profiles. Cubicles for rated voltages up to 17.5 kV are of identical construction. Each cubicle is divided into three sealed and isolated compartments by partitions, i.e. the bus- bar, cable connection and circuit-breaker compartment.
The fixed contacts of the primary discon- nects are located within insulating breaker bushings, effectively maintaining the com- partmentalization in all operating conditions of the switchgear. The bushings are cov- ered by automatic steel safety shutters upon removal of the circuit-breaker element from the ”Connected“ position. Each compartment in every model has its own pressure-relief device. To reduce inter- nal arcing times and thus consequential damages, pressure-switches can be in- stalled that trip the incoming-feeder circuit breaker(s) in less than 100 msec. This is an economic alternative to busbar differential protection.
Interrupter truck
The truck normally supports a vacuum circuit breaker with the associated operat- ing mechanism and auxiliary devices. By manually moving the truck with the a spindle drive it can be brought into a dis- tinct ”Connected“ and ”Disconnected/ Test“ position. To this effect, the front door remains closed.
Inspection can easily and safely be carried out with the circuit breaker in the ”Discon- nected/Test“ position. All electrical and mechanical parts are easily accessible in this position.
Mechanical spring-charge and contact-posi- tion indicators are visible through the closed door. Local mechanical ON/OFF pushbuttons are actived through the door as well.
For complete remote control, the circuit breaker carriage can be equipped for motor operation.
Low-voltage compartment
All protective relays, monitoring and con- trol devices of a feeder can be accommo- dated in a metal-enclosed LV compartment on top the HV enclosure. Device-mounting plates, cabling troughs, and the central LV terminal strip(s) are located behind a separate lockable door. Full or partial plexiglass-windows, or mimic diagrams are available for these doors.
Main enclosure
The totally enclosed and sealed cubicle permits installation in most equipment rooms. With the optional dust protection, the switchgear is safeguarded against internal contamination, small animals and rodents, and naturally against contact with live parts. This eliminates the usual rea- sons for arc faults. Should arcing occur,
nevertheless, the arc can be guided towards the end of the lineup, where dam- ages are repaired most easily. For the lat- ter reason, partitions between individual cubicles of the same bus sections are nor- mally not used.
Busbars and primary disconnects
Rectangular busbars drawn from pure copper are used exclusively. They are mounted on ribbed, cast-resin post insula- tors which are sized to take up the dyna- mic forces resulting from short circuits. The movable parts of the line- and load- side primary disconnects have flat, spring- loaded and silver-plated hemispherical pressure contacts for low contact resist- ance and good ventilation. The parallel con- necting arms are designed to increase con- tact pressure during short circuits. The fixed contacts are silver-plated stubs within the circuit-breaker bushings.
Instrument transformers
Up to three multicore block-type current transformers plus three single-phase potential transformers can be installed in the lower compartment; PTs optionally on withdrawable modules.
Siemens Power Engineering Guide · Transmission & Distribution 2/22 7.2 Technical data Rated voltage Lightning- impulse test voltage Power- frequency test Rated short- circuit- breaking current/ short time current kA [rms] Rated short- circuit- making current [kA] Rated feeder current 1250 [A] 2500 [A] 3150 [A] 5000 [A] 5000 [A] 50 63 20 28 36 38 60 75 95 95 12 15 17.5 125 160 [kV] [kV] Rated busbar current 50 63 50 63 50 63 125 160 125 160 125 160 [kV]
Air-insulated Switchgear
Type 8BK40
The C.T.s carry the cable-connecting bars and lugs, and the fixed contacts of the (op- tional) grounding switch. All common bur- den and accuracy ratings of instrument transformers are available. Busbar meter- ing PTs with their current-limiting fuses are installed on a withdrawable truck, identical to the breaker truck.
Cable and bar connections
Cables and bars are connected from below; entrance from above requires an auxiliary structure behind the cubicle. Single-phase or three-phase solid-dielectric cables can be connected from the front of the cubicle; stress cones are installed con- veniently inside the cubicle.
Regular and make-proof grounding switch- es with manual operation can be installed below the C.T.s, engaging contacts behind the cable lugs. Operation of the fully inter- locked grounding switch is possible only with the breaker carriage in the ”Discon- nected/Test“ position.
Interlocking system
A series of sturdy mechanical interlocks forces the operator into the only safe oper- ating sequence of the switchgear, prevent- ing positively the following:
■Moving the truck with the breaker closed.
■Switching the breaker in any but the locked ”Connected“ or ”Disconnected/ Test“ position.
■Engaging the grounding switch with the truck in the ”Connected“ position, and moving the truck into this position with the grounding switch engaged.
Degrees of protection
Degree of protection IP 4X:
In the ”Connected“ and the ”Disconnect- ed/Test“ position of the truck, the switch- gear is totally protected against contact with live parts by objects larger than 2 mm in diameter.
Optionally, the cubicles can be protected against harmful internal deposits of dust and against drip water (IP 51).
Installation
The switchboards are shipped in sections of one cubicle on stable wooden palletts which are suitable for rolling and forklift handling. These sections are bolted or spot-welded to channel iron sections em- bedded in a flat and level concrete floor.
Front-connected types can be installed against the wall or freestanding. Double- busbar installations in back-to-back configu- ration are installed freestanding.
Cable feed-in is through corresponding cut- outs in the floor; plans for which are part of the switchgear supply. Three-phase (armored) cables for voltages above 12 kV require sufficient clearance below the switchgear to split up the phases (cable floor, etc.). Circuit breakers are shipped mounted on their trucks inside the switch- gear cubicles. For preliminary dimensions and weights, see Fig. 28.
Fig. 29 Fig. 28 7.2 1100 2500 2300 2800 Rated voltage Width Height Depth Approx. weight incl. breaker
Weight and dimensions
12 15 17.5 [kV] [mm] [mm] [mm] [kg] 1100 2500 2300 2800 1100 2500 2300 2800 1100 2500 2300 2800
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Air-insulated Switchgear
Type 8BK40
Fig. 30: Available circuit options for switchgear/generator panel type 8BK40 8BK40 switchgear up to 17.5 kV
Panel
Withdraw- able parts
Fixed parts Metering
panel Busbarmodules
Sectionalizer Bus riser panel
8BK40 generator vacuum c.b. panel
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