Çavkantî û Pirastinên li Ser Darkevekirina Qutelên Daştanî

Daxweşên elektrîkî ya bi tenzîlê (li serberê dike navkirin "daxweşan") daxweşên elektrîkîn ên bi tenzîl û têkilîn li ser sisteman da 380/220V de bikaranîn ji bo derketina û tevabûna energiyê. Wan yê bêyîn hatine çavkerandin ji dilalî şerê nîvekên transformasyonê. Di navnetevî de herî lê zêde kirîne anîyarên parastîn wê gotarên fuses, pêşînên rîkardina sarkirîn, û pêşînên qefilbûn; anîyarên kontrola wê gotarên contactors, circuit breakers, load switches, û disconnectors; anîyarên pîvan wê gotarên current transformers û energy meters; û anîyarên kompensasyonê wê gotarên capacitors. Bi împlementasyonê projeyên binçeya vê qadrê û rejînekirina gridên elektrîkîya şar û tarî, serkarîn wekîn daxweşan, û serkarîn berbiyayîn elektrîkî yên cîhazî, pir wan çewtî û karîgerînên operasyonî yên din dikarin bigihînin ku hewce ne.

1. Dega Werda Xwerû Qadimîn Cîhazan Elektrîkîyan Di Navnetevî Daxweşan De

Temperatûra ambiyantî ya herî ya daxweşan bi tenzîl û têkilîn da ku ji alîyê standartên nasîyonî têkilîn, di dema operasyonê de divê nekin wek 40°C. Lekin, ji bo daxweşan bi tenzîl û têkilîn da ku bi rûnya xorekî re çalak in, di dema girîngîya hewlê, ji bo rûnya direk, bingehêna çiçekan, û dega werda ji anîyarên navnetevî, temperatûra navnetevî divê wek 60°C bibin. Ev temperatûra herî ya daxweşan dikare insulation aging û breakdown burning dibike. Dega werda ya herî ya daxweşan dikare resistance-yên contactan elektrîkîyan biderbasibîne, ku heta dibe dega werda ya herî ya daxweşan dikare stability-yên protection characteristics, reliability-yên operasyon, û accuracy-yên metering biderbasibîne. Ji ber vê yekê, piştgirî dike:

(1) Daxweşan bi vents louvered di du pêşeya de bikar bînin û partition navnetevî nekomplet bikar bînin ji bo facilitekirina air convection for heat dissipation.

(2) Body-ya box dikare ji stainless steel natural-color bikar bîne, ku nekîne li ser corrosion û reflect heat. Ji bo apply kirina periodik coatingan heat-insulating ji bo reduce heat radiation, effect better bikin.

(3) Ji bo ensure ventilation, box dikare position bikar bîne ji bo avoid midday sunlight direct, û ground beneath dikare non-gravel bikar bîne.

(4) Overloading equipment during high-temperature seasons and minimize heat generation from devices inside the box.

2. Lightning Protection Limited by Installing Surge Arresters Only on the Incoming Line Side

Typically, fuses or other devices are installed between the incoming/outgoing lines and the busbar inside the distribution box. If an outgoing line is struck by lightning, causing the incoming line fuse to blow first, the entire box loses lightning protection. Many distribution boxes are damaged by lightning strikes every year. It is recommended to install zinc oxide surge arresters on all incoming and outgoing line sides of the distribution box.

3. Use of Inappropriate Products Increasing the Failure Rate of Distribution Boxes

It is advisable to select high-quality, low-resistance products (e.g., low-resistance fuses), which can not only reduce losses but also decrease heat accumulation within the box, extending equipment service life. Additionally, the safety margin for some components should be appropriately increased. Due to the high internal ambient temperature, the current-carrying capacity margin for conductors should be increased by at least one specification. Without changing the rated current of the fuse element, selecting a slightly larger physical size for the fuse holder can reduce the probability of its base burning out.

4. Improper Installation Techniques Causing Overheating and Burnout of Connections

Some electricians, when replacing leads, fail to use crimped lugs, instead twisting stranded wires to form a lug for screw connection, leading to burned-out leads shortly after replacement. In boxes produced by some manufacturers, branch lines are overlapped and screw-connected directly onto the main bus, leading to poor heat dissipation and frequent failures under heavy loads. It is recommended to add a distribution block on the load side of the main bus, with branch lines connected from this block. This improves heat dissipation, appearance, clarity, and facilitates secure wiring.

5. Commissioning Without Inspection, Creating Safety Hazards

Although products provided by manufacturers undergo strict factory inspections, transportation bumps and handling vibrations can cause some connection bolts to loosen upon arrival. This leads to overheating of wire connections shortly after operation. It is recommended to perform inspection and re-tightening before commissioning.

6. Other Issues

• Improper Installation Location: Improper placement affects the urban  landscape and makes the box susceptible to external damage. Choose an appropriate location considering all factors.

• Inadequate Grounding System: Some TN-C systems (protection neutral connection) still use      the three-phase four-wire supply method. The neutral wire in the low-voltage network is often long with significant impedance. Under  unbalanced three-phase loads, zero-sequence current flows through the neutral. Furthermore, due to environmental factors, conductor aging, and moisture, leakage currents can also create a loop through the neutral,causing it to carry a potential, which is detrimental to safe operation. Adopting a TN-S system (three-phase five-wire supply) is recommended.      Here, the working neutral and protective earth conductor are separate,effectively isolating the hazardous voltages possible in the TN-C system and keeping equipment enclosures at "earth potential," thereby eliminating the risk.

• Inadequate Spacing and Features: Insufficient clearance between devices and between phases, sometimes without visible disconnection points, poses risks for electricians and prevents live replacement of fuses during rain or fog.

• Lack of Phase-loss Protection: The absence of phase-loss protection leads to motor  burnouts due to single-phasing.

• Use of  Non-electronic Meters: Some boxes lack electronic energy meters,preventing remote centralized meter reading.

• Lack of  Maintenance: Some boxes remain closed year-round without routine inspection and maintenance.

The author believes that in locations requiring high power supply reliability and/or having poor environmental conditions, the distribution box specifications should be appropriately increased to facilitate maintenance; forced cooling measures or high-temperature resistant electrical components should be used where necessary to reduce failure rates; and intelligent equipment should be installed for remote monitoring and dynamic management to achieve safe, high-quality, and reliable power supply.