Main technical specifications for low-voltage distribution equipment
GB 4942.2-85 Degrees of Protection Provided by Enclosures
GB 7251-97 Low Voltage Switchgear Sets
JB/T 9.661-1999 Low voltage withdrawable switchgear complete set
GB14048 Low voltage switchgear and control equipment
TECHNICAL INDEX
(l) Environmental conditions
l) Environmental temperature: -15 ℃ to+40 ℃, daily temperature difference<25 ℃.
2) Environmental humidity:>95%.
3) Seismic resistance: horizontal acceleration<0 165g ， Vertical acceleration<0 83g , Safety factor=2.
(2) Operating conditions
l) Working voltage: 380V ± 10%.
2) Working frequency: 50Hz ± 5%.
3) Protection system: TN-S.
(3) Overall requirements for switchgear
l) The circuit breaker between the two incoming lines should be equipped with electrical and mechanical interlocking, and the circuit breaker between the two incoming lines and the busbar should be equipped with electrical interlocking to prevent the parallel operation of the two power sources
2) Circuit breakers with 600A and above are frame type circuit breakers. Circuit breakers with 600A and below are plastic shell switches, and comply with the IEC157-1 standard, but not lower than GB 1497-87 "Standard for Low Voltage Electrical Installations".
3) The main incoming line of the low-voltage switchgear in the substation adopts a closed busbar incoming line method, while the feeder cabinet adopts a cable outgoing line method. The incoming cabinet is equipped with an incoming circuit breaker, closing indicator light, ammeter, voltmeter, voltage conversion switch (five positions), and current conversion switch.
4) All equipment should have a label after installation and operation, which should indicate the capacity, operating characteristics, type, and serial number. All equipment should have reliable safety measures to prevent accidents and equipment damage.
5) The dimensions of the components inside the switchgear and the isolation room are modularized, and the side panels and doors are made of cold-rolled steel sheets with a thickness of not less than 2mm. The electrical equipment of the unit circuit is installed in the pull-out functional unit and can be flexibly combined according to various required unit circuit schemes. In the event of a failure, the unit can be quickly extracted and replaced with a backup unit for continued use. The same unit can be interchanged on any cabinet.
6) Each outgoing unit of the low-voltage switchgear has a "running" indicator light, a "stopping" indicator light, and an ammeter.
(4) Structure of switchgear
l) By interlocking the mechanism, each extraction unit is equipped with a moving position, a testing position, and a breaking position.
2) Connection (working) position and separation position.
3) It should be ensured that drawers of low-voltage circuit breakers of the same specifications can be interchanged.
4) Sufficient contact pressure (contacts) should be ensured.
5) The dynamic and thermal stability of a single isolation contact should not be lower than the requirements of the corresponding capacity knife switch.
6) There should be a grounding contact position between the extraction unit and the screen (cabinet) body, with a contact resistance of<1000m Ω.
7) The connection method between multiple cable busbars and circuit breakers should be considered for incoming and outgoing wiring. The depth and total width of the cabinet must not exceed the dimensions indicated on the plan, and the positions of the incoming and outgoing lines must not be misaligned to avoid affecting the reserved holes.
8) The switchgear should operate safely during the maximum short-circuit fault and be able to withstand the electrical and mechanical stress caused by it. The gas generated under fault conditions should be discharged through the pressure release port, and the position of the pressure release port should not face the operator. Functional units of 800A and above should have separate exhaust or jet ports, and smaller functional units can share one jet port.
9) The top of the cabinet is equipped with lifting rings for easy hoisting. When the product leaves the factory, the bottom of the cabinet is equipped with a wooden base, which is easy for forklifts to shovel and transport the bottom.
10) The cabinet is fully partitioned, and the partitions of the device compartment, busbar compartment, and cable compartment are all halogen-free, flame-retardant, and self extinguishing. The entire cabinet is fully enclosed, with a protection level of IP40.
11) The metal structural components inside the cabinet, except for the exterior door panel which is made of aluminum zinc plate, have been galvanized. The paint on the surface of the switchgear door panel and sealing plate should be degreased, derusted or phosphated first. A layer of anti-corrosion primer should be sprayed on both the inner and outer surfaces, and then electrostatic epoxy powder should be sprayed with a thickness of 4O ц m to ensure that the surface coating of the switchgear does not peel off throughout the entire service life. The coating color should be approved by the construction unit and design unit.
(5) Technical parameters
l) Main circuit of switchgear
a) Rated working voltage of the main circuit: AC 660V.
b) Rated frequency: 50Hz.
c) Rated working current of busbar.
d) Horizontal busbar (main busbar): 4000A *.
e) Vertical busbar (branch busbar): 1000A *.
f) Rated short-time withstand current (3-second effective value)
Horizontal busbar (main busbar): 80kA *.
Vertical busbar (branch busbar): 50kA *.
Protective conductor (grounding busbar): 48kA *.
Neutral busbar (neutral main busbar): 48kA *.
g) Rated peak withstand current
Horizontal busbar (main busbar): 176kA *.
Vertical busbar (branch busbar): 105kA *.
h) Power frequency withstand voltage of switchgear 2 5kV ， Impulse withstand voltage 8KV
i) The reduction factor of this product is 0 8.
Projects marked with * are determined by the designer based on the project situation.
2) Low voltage circuit breaker
a) Performance parameters of frame circuit breaker.
·Connection and disconnection cycle components (effective value):>80kA (3s).
·Maximum on-off cycle component (effective value): 100kA.
·Closing time:<0.04s.
·Inherent opening time:<0.04s.
·Fully open (energized) time:<0.006s
·Operation mode: Electric motor operation, direct manual/electric.
·Protection method: Electronic type - with three-stage protection characteristics, with an adjustable delay of 0.5s for undervoltage offline.
·Long delay: Set current range: 0 9-1 25In., continuously adjustable from 5 to 30 seconds.
·Short delay: Setting current range: 2Ih, 4 Ih, 6 Ih, continuously adjustable from 0.5 to 0.8s.
·Instantaneous: Setting current range: 8 Ih, 12 Ih, 16 Ih.
·Overvoltage multiplier: (at maximum on/off)<2 5.
·Current limiting coefficient: (actual peak breaking current/expected peak short-circuit current) 0 6.
·Electric lifespan:>10000 cycles.
·Mechanical lifespan:>20000 cycles.
The operating mechanism of the frame type circuit breaker should be of the spring energy storage type, which can be manually or electrically stored. Under normal circumstances, the circuit breaker can be manually closed and opened using buttons. There should be ON/OFF status indication and spring energy storage.
State indication of spring release, while providing necessary locking devices to prevent: pushing and pulling out when the circuit breaker is in the closed position; The circuit breaker cannot be closed without complete insertion and isolation; The circuit breaker cannot open the cabinet door without being completely isolated. Each circuit breaker is allowed to be replaced, tested, and repaired under isolated conditions in the form of a drawer.
b) The series of plastic shell switches are strictly configured according to the requirements of the bidding documents and drawings. The rated current of the switch must be at least two levels higher than the set current.
3) Terminal block
The rated current of the terminal block shall not be less than 10A, 380V, and the markings of each terminal block shall be consistent with the design drawings.
The wiring inside and outside the cabinet of each functional unit or component must be connected to the terminal block interface, and soldering or plugins cannot be used. There should be no less than 15% of spare terminals left in the cabinet, and each wire will be fixed to a dedicated terminal. Composite terminals are connected using connecting pieces.
4) The current transformer, voltage transformer, current, voltage, power, watt hour meter, sensor, bus and signal secondary components installed in the low-voltage cabinet can be joint venture products (Great Wall logo certification).
5) Monitoring requirements for low-voltage cabinets in building automation systems:
a) Incoming line current, voltage, active power, power factor, and active energy;
b) Mother current and switch status;
c) The status and operating temperature of the transformer feed out switch, as well as the switch status and switch faults of the low-voltage main circuit breaker and the bus circuit breaker.
The above requirements require the manufacturer to leave contacts in the cabinet and lead them to the upper opening of the terminal block for construction by the hard building company.
6) Fire protection requirements for power distribution systems:
For all circuit breakers with additional excitation and tripping, lead out terminals should be left for the convenience of fire protection companies to connect them, which can be used to cut off non fire power sources in case of fire accidents.
(6) Capacitor cabinet
l) Low voltage capacitor compensation screen
The low-voltage capacitor compensation cabinet adopts an automatic step-by-step compensation capacitor method, and its cabinet structure is the same as that of the low-voltage switchgear. An automatic compensation device is installed on the cabinet. When installed side by side with the low-voltage switchgear, the cabinet size and color should be consistent with the low-voltage cabinet.
2) Dry type full film low-voltage metalized capacitor
a) Technical symbol: IEC70/70A;
b) Rated voltage: 400/230V;
c) Frequency: 50Hz;
d) Environmental temperature: upper limit+50 ℃, lower limit -25 ℃;
e) Performance: Capacitors should have advanced indicators such as no oil immersion, no leakage, no combustion, no explosion, no environmental pollution, long service life, low loss, etc. At the same time, they should be compatible with the technical parameters of supporting equipment and meet the allowable conditions for voltage fluctuations. Capacitors should have self-healing properties (se lf healing). When a capacitor is permanently broken down, only the faulty component exits operation, while other components can still operate normally. Equipped with a discharge resistor, the voltage between the terminals drops below 50V within 1 minute. An automatic switching low-voltage capacitor device should be equipped to maintain the power factor at 0 When switching between groups of 9 or above, resonance should not occur. Type test reports (including indicators such as lifespan and capacity degradation rate) should be provided.