نمونه مشخصات یک تابلو فشار متوسط
- Working voltage 6.6 kV ± 8%
- Rated voltage: 7.2 kV
- Rated insulating level: 12 kV
- 60 sec. Test voltage at 50 Hz: 31 kV
- impulse test voltage 1.2/50 micro s: 81 kV
- frequency: 50 Hz + 5% - 2%
- symmetrical short-time current: 31.5 kArms for 1 s (at 6.6 kV)
- maximum value of the instantaneous short circuit current: 90 KA
- rated main bus bar current in continuous duty: 630 A
- current rating for branches bus bars in continuous duty: 630 A
These values shall be in compliance with the maximum capacity of the switchgear of the panel in question.
Auxiliary circuits and services
- auxiliary voltage for closing and warning circuits: 230VAC + 10% - 15%
- auxiliary voltage for breaking circuits: 230VAC + 10% - 30%
- protecting relay supply circuits: 230VAC + 10% - 20%
- internal lighting , sockets
and heating resistor circuits: 230 V AC 50 Hz
- test voltage for auxiliary 2000 V – 50Hz
- For electronic/digital apparatus (i.e. Protection relays) the testing voltage will be according to the relevant standards
5- DESIGN AND CONSTRUCTION
-The boards shall be of air insulated, metal-clad and shall be of prefabricated self supporting type for indoor installation in industrial plants and shall be designed for mounting on structural steel base embedded in concrete construction. The boards shall consist of independent, standardized easily assemble cubicles provided with front door.
-Moreover it shall be such as to allow the addition of other cubicles without major mechanical modification to the existing cubicles.
-The switchgear shall have circuit breakers and earthing switches and also vacuum contactor for 6.6KV transformers. The circuit breaker shall be of the horizontal draw-out indoor type and units with equal rated currents shall be readily interchangeable with another. Circuit breakers shall be of vacuum and draw-out type.
- The switchgear shall be of flush fronted design having a neat and clean appearance and readily extensible. The front doors shall be swinging type and provided with locking device.
- All components shall be accessibly mounted in the switchgear and shall not impede access to wiring or terminals.
-On the back side , the cubicle shall be closed with removable steel sheet to ensure accessibility for inspection or maintenance.
-Moreover, every casual contact between HV gears and LV gears shall be absolutely prevented by suitable means such as screening.
No readily inflammable material shall be used in the construction of the frame supports or enclosure.
-The boards shall have the following protection degree:
IP 42 with closed door
IP 20 with open door
-Each cubicle shall have sufficient strength to withstand all accidental damages due to transportation, storage, erection, operating conditions, short circuit etc. Without suffering deformation or other damages of any kind. The cubicles shall be provided with lifting lug.
-The front doors shall have mimic diagram.
-Unless otherwise specified, the cable inlets and outlets shall be from the bottom (6.6kv ,control, auxiliary cables) . The auxiliary connection between the panels shall be located on the top of the board. All necessary cable glands, lug & terminals shall be provided.
-Each board section shall consist of one bus system and shall withstand the same value and duration of short-time withstand current as specified for the bus-bar in this section.
-The switchgear shall be constructed from sheet steel of the thickness not less than 2.5mm and the finish shall consist of two coats of anticorrosion prime and two coats of final.
-All cubicles shall be fitted with metal rustproof nameplate in English to be fixed by screws.
Moreover, for each cubicle a circuit identification label shall be provided rating plate, marking and labeling for all components of the switchgear shall be according to IEC.
-All metal parts for the switchgear not belonging to the current carrying components and equipment but which might come in contact with energized part due to failure or to striking of an electric arc will be interconnected by means of an earthed conductor.
-Access to energized part when the equipment is will not be possible unless suitable equipment is used.
-Removal of draw-out equipment will be possible only through a sequence of specific mechanically inter-locked operations, by which the equipment is de-energized.
- Equipment under possible electro static induction (such as capacitors etc.) shall be duly earthed before access is provided.
- The draw-out unit normally earthed shall remain so during the draw- out operations until the distance from the live components is less than the isolation distance.
- All necessary and special tools, hardware, etc, required for the satisfactory installation, commissioning , shall be provided.
- All faults occurring with any individual unit shall be contained with the unit , an except for bus-bars fault shall not cause shut-down of any section board other than the unit itself .
- All equipments shall be constructed of non-hygroscope and non-flammable material.
-The supply shall include all the material necessary for anchoring at the floor (i.e. base frame etc.)
-Each C.B. and M.V. cable compartment shall be fitted with proper heating resistors M.C.B. controlled by adjustable thermostat (for each panel: No. 2 heating resistors and No. 1 thermostat).
-Special precautions shall be taken to prevent corrosion between different metals
-Internal lighting in aux cell shall be considered. The lamp shall be controlled by end-switch.
-One 230 V a.c. socket in each aux. Cell must be provided.
-the metal clad switchboard shall be designed for mounting on a structural steel base embedded in concrete
-Each compartment shall be provided with a door. Each door shall be provided with a dedicated lock (n. 2 keys)
-The sequence of phases shall be R-S-T from left to right when operator see the panel from the front.
The auxiliary wiring shall have the following cross section:
Ammeter circuit: ≥ 4 sqmm
Internal board feeders (between panels): ≥ 4 sqmm
Other circuits: ≥ 2.5 sqmm
Requirements on terminal strips:
For the ammeter circuit shall be short circuit able type;
For the voltmeter circuit shall be sectionalizing type;
At least the 10% spare terminals for each type shall be provided.
Each section of the D.C and A.C distribution system shall be provided with an individual supply which shall be protected by a 2 pole automatic circuit breaker provided with thermo magnetic trips. Circuit breakers or fuse of auxiliary circuit terminals and other auxiliary apparatus requiring attention while the equipment is in service shall be accessible without exposing high- voltage.
7- BUS-BAR AND CONNECTIONS
Bus-bars and connection between the several pieces of apparatus forming the equipment of a cubicle shall be of high conductivity 99.9% electrolytic copper.
Buses in the cubicles shall be sized to carry their maximum load continuously without exceeding the allowed temperature limits stated in IEC recommendations at voltage 5% lower than the rated value. The bus-bar system shall be according to electrical characteristics which mentioned in this specification. The buses shall withstand the electrodynamics stresses caused by short-circuits without undergoing permanent deformation.
Main and branching-off buses shall be covered with an insulation material of non-hygroscopic type.
The bus shall be segregated and arranged in a separate special metal duct into the back compartments.
- Bus Supporting shall be insulating diaphragm type and shall be made of non-hygroscopic insulating materials. Bus supporting installed between the compartments shall also of non-flame propagating type.
- Bus - bars connections and their supports shall be of an approved type designed to withstand all normal and abnormal conditions arising in the system. They shall be capable of carrying the short circuit rating, for period of not less than 1 s.
- The bus-bars connections in individual units shall have a continuous current rating of not less than that of the equipment the unit.
- All the points where connections or joint occur the bus-bars and connecting pieces shall be silver plated, clamps where used, shall be phosphor bronze and bolts for joints shall be of stainless steel.
- Main bus-bars shall have rounded edges to protect against "point effect"
8- CIRCUIT - BREAKERS
- The circuit breakers shall be of horizontal withdraw able type for indoor installation. They shall be housed into the front compartments.
- All circuit breakers of equal rated current shall be interchangeable.
- Circuit breakers shall be able to remain in three different positions within the cubicles.
Normal operating, position. In which main and auxiliary circuit are connected.
Main circuits isolated and auxiliary circuits are connected.
Both main and auxiliary circuits isolated
- It shall be possible to close the front door of the cubicles whatever the position of the circuit breaker is.
- In the connected and isolated positions, the circuit breakers remain inside the compartment with door closed.
- A series of mechanical interlocks are provided to prevent wrong operation.
- Movement of the withdraw able module from isolated to service position is possible only with the earthing switch in open position.
- The earthing switch can be closed only the withdraw able module is in isolated position.
- The circuit breaker cannot be inserted or drawn-out in closed position.
- The circuit breaker cannot be closed with the withdraw able module being in between isolated and service positions.
- Automatic shutters are closed when the circuit breaker is moved from the service position; totally avoid any accidental contact with the live parts.
- Movement of the withdraw able module from isolated to service position or vice versa cannot be done with the front door open.
- It is possible to lock circuit-breaker truck in service and isolated positions.
- The circuit breaker actuating mechanism shall be of spring loaded type, and the spring loading motor shall be of D.C type.
- Circuit breakers shall be provided with independent opening and closing circuits, individually protected by two-pole circuit breakers equipped with thermo magnetic trips.
- The closing circuit shall also supply the spring loading motor, a lamp shall permit remote supervision of the spring loading.
- Positively driven mechanically operated indicating device shall be provided to indicate whether a circuit breaker is in the open or closed, service, isolated or earthed position.
A visual mechanical indicating device shall also be fitted to show the state of the mechanism closing spring.
- Alarm circuits shall always be electrically independent of control and indicating circuits. A lamp shall be provided to permit supervision of the circuit breaker opening circuit.
- 23OVAC power shall be provided from external source and double pole MCCB shall protect the circuit where entering the switchgear. A loss of power 230 VAC relay shall be used at load side of MCCB, with adequate number of contacts for alarm and tripping purpose in the switchgear and for remote. Minimum two N.C voltage free contacts shall be provided for remote alarming of loss of A. C supply.
- Each cubicle shall be equipped with a thermostatically. Controlled space heater minimum for separate 230V AC. External power lines shall feed the 230V AC circuits of switchgear, two for cubicles space heaters and two for others. One line of each of them shall feed the odd and the other line shall feed the even cubicles the space heater circuit in each cubicle shall be protected by single pole MCB.
- The circuit breaker shall be provided with a, hand-operated emergency control which shall allow opening and closing operations also in the case of loss of control supply. Breaking and making capacities shall be ensured also by hand operation.
- Moreover, the circuit breaker shall be provided with safe mechanical interlocks to avoid faulty connecting operations when the breakers are in the open position. Closing electrical control shall be provided with an antidumping device and a short pulse actuation.
- The normally closed and normally open auxiliary contacts used for external connections shall be electrically independent.
- The rated operating sequence shall be 0-0.35 Co-3min - Co.
- The rated voltage (Y) of spring- loading motor and related upper and lower limits : 230V+10%-15% AC .
- Rated voltage (V) of closing coil, opening coil and related upper and lower limits.
Closing coils 230V+10%-15% AC
Tripping coil 230V+10%-30% AC
9- CURRENT TRANSFORMER
All current transformers shall have the following characteristics
- Type: solid resins insulation
- Insulation reference voltage 12 kV
- 1 min test voltage 31 kV at 50 Hz (rms)
- impulse test voltage 1.2/50 micro s 81 kV pk
- maximum permanent thermal current 1.2 times the primary rated current
- rated short-circuit current 31.5 kA – 1 s
- No. of cores as indicated in the enclosed drawings
- Rated secondary current 5 A (unless otherwise specified in the enclosed drawings)
- Where specified on the diagrams 5/1 correctors shall be provided
- Rated output (VA) must be suitable for connected instruments and relays
- The measuring core shall have a 0.5 % class of accuracy
- Accuracy class of protection core 5P
- Accuracy limit factor:
- For protection 10
- Rated primary current values as single line diagram
- Secondary windings shall be earthed
10- POTENTIAL TRANSFORMR
All potential transformers shall have the following characteristics:
- Type Insulation in solid resins
- Insulation reference voltage 12 kV
- 1 min test voltage 31 kV at 50 Hz (rms)
- Impulse test voltage 1.2/50 micros 81 kV pk
- Primary connection normally between phase and earth
- Primary voltage 6.6/ sq.3 kV
- Secondary voltage 100/ sq.3 V
- Rated voltage factor 1.2 for unlimited time
- Accuracy class 0.5%
- Rated output (VA) must be suitable for connected instruments and relays .
- All potential transformers shall be mounted in a normal PT compartment and mounted in a draw-out type carriage, protected by:
- M.V. side: fuses