What I have learned about Distribution cabinet

Table of Content

(Last Updated On: 2020年12月7日)

Introduction of distribution Boxes and Cabinets

The distribution box and distribution cabinet are the general name of motor control center. According to the electrical wiring requirements, the switchgear, measuring instruments, protection appliances and auxiliary equipment are assembled in closed or semi-enclosed metal cabinets, which composed of the low-voltage power distribution devices and are used to control and protect lines and equipment.

Distribution cabinet

For the purpose, the distribution box is generally used in the household, while the distribution cabinet is used in the centralized power supply, such as industrial electricity and construction electricity, etc. The distribution box and the distribution cabinet belong to the complete equipment, the distribution box belongs to the low-voltage complete equipment, and the distribution cabinet has high-voltage and low-voltage.

The most basic difference from the appearance is the size. The switchboard is placed on the ground, and the volume is as large as a refrigerator model. The distribution box is small as a box stapled to the wall, the function of the two roles are the same.

Distribution cabinet

Applications and selection of Power Distribution Box

The distribution box and the distribution cabinet distribution panel are complete sets of devices that are centrally installed with switches, instruments, etc., to facilitate the measurement and judgment of stopping and sending power when the power is stopped or sent, and to facilitate overhaul and maintenance when the circuit fails.

Application of distribution cabinet on lighting
Application of distribution cabinet

Generally speaking, the power distribution cabinet has the distinction of high-voltage power distribution cabinet and low-voltage power distribution cabinet. the internal structure and technical parameters are different. For the requirement of the customer, we should to consider the questions while we choose the distribution box.

First, you need to identify your needs and choose the most suitable type of distribution cabinet according to your actual situation. This is the basic principle that you should have to follow in terms of selection.

Secondly, we should preferably adopt the cabinet type of the domestic distribution armature and distribution box manufacturer’s domestic distribution cabinet that is well-known by people, and do not blindly choose the imported brand cabinet with high technical reference, which not only wastes resources, and also may not be applied in actual life. Because the brand of the main components used in the imported distribution cabinet may not be the same as the cabinet, when choosing the imported distribution cabinet, special attention needs to be paid to the parameters of the main components. If the parameters of some components do not meet the demand, it is inappropriate to select the imported one.

Components of distribution cabinet.

About the components inside the electrical cabine, which according the usage to choose the right devices. Usually a complete distribution cabinet have the following necessary components.

I. Circuit Breakers

Circuit breaker: a switch, the main component of the distribution cabinet, Usually the air switches. Leakage switch. Double power automatic changeover switch are widely used.

  1. Air Switch.
  2. Air switches, also known as air circuit breakers, are used to switch on, off and carry the rated operating current and fault current such as short-circuit and overload in a circuit, and can quickly break the circuit for reliable protection in the event of overload, short-circuit or under-voltage in the circuit and load.
  3. Leakage protection switch.
Leakage Circuit Breaker

It is the main function of the Leakage Protector to ensure the safety of human beings, as it has the function of leakage protection; if the electricity-using equipment is not well insulated and leaks into the shell, the Leakage Protector will also trip to avoid human touching and electrocution. At the same time with the current flow interruption function, overload protection and short circuit protection function.

2.-dual power automatic changeover switch.

The dual power automatic changeover switch is an automatic two-to-one switching system for the power supply, the dual power supply automatic transfer switch automatically switches to the second circuit to supply power to the load when the first circuit fails, and the dual power supply automatic transfer switch automatically switches to the first circuit to supply power to the load when the second circuit fails.

dual power automatic changeover switch

3.-Surge protector.

Surge protector, also known as lightning protection, is a variety of electronic equipment, instruments and meters, communication lines to provide safety and protection of electronic devices. When the electrical circuit or communication lines because of external interference in the sudden generation of spikes in current or voltage, the surge protector can turn on the shunt in a very short period of time, thereby avoiding surge damage to other equipment in the circuit.

Surge protector

4.-Meters.

The meter commonly used by electricians to measure electrical energy is commonly known as an electric meter.

When a watt-hour meter is connected to an electric circuit, the voltage and current coils generate magnetic fluxes through the disk that are different in time and space and induce eddy currents on the disk.

Due to the interaction between the magnetic flux and eddy current, the rotating moment is generated to make the disk rotate, and due to the braking action of the magnet, the rotation speed of the disk reaches a uniform motion.

As the magnetic flux is directly proportional to the voltage and current in the circuit, the disk moves at a rotation speed directly proportional to the load current, and the rotation of the disk is driven to the meter by a worm.

Digital meters

5.-Ammeter 

Current meters are made according to the action of the magnetic field on an energized conductor in a magnetic field. When an electric current is passed through the magnetic field along the spring and shaft, the current cuts the inductance line, so the magnetic field force deflects the coil and drives the shaft and pointer.

Since the magnitude of the magnetic field force increases as the current increases, it is possible to observe the magnitude of the current by the degree of deflection of the pointer. 

Ammeter 

6. Voltmeter.

A voltmeter is an instrument for measuring voltage, commonly used voltmeter – voltmeter symbol: V. Inside the sensitive ammeter there is a permanent magnet, and between the two terminals of the ammeter a coil made of wire is connected in series, the coil is placed in the magnetic field of the permanent magnet, and is connected to the hands of the meter by a transmission device. The voltmeter is a fairly large resistor, ideally considered to be disconnected, and by the relationship of Ohm’s law, it is known that the current displayed by the ammeter is proportional to the external voltage, so it is possible to measure the voltage.

Voltage Meter

However, the above-mentioned components are the most basic components in the distribution box, and other components are added in the actual production process according to the different uses of the distribution box and the requirements for the use of the distribution box, such as: AC contactors, intermediate relays, time relays, buttons, signal indicators, KNX intelligent switch modules (with capacitive load) and background monitoring system, intelligent fire evacuation lighting and background monitoring system, electrical fire/leakage monitoring detectors and background monitoring system, EPS power supply batteries, and so on.

Appreance of the distribution Cabinet

The causes and precautions of the burnout for distribution cabinet

1.-the cause of burn out of distribution cabinet

Burn out of the disctribution box
Burn out of distribution cabinet

(1) There is no insurance on the high and low voltage side of the mating transformer, and some of them are equipped with drop fuse and sheep’s horn fuse, but the fuse is replaced by aluminum or copper wire, so that the fuse cannot fuse normally and burn out the mating transformer when the low voltage short circuit or overload occurs.

(2) The high and low voltage fuses are improperly configured and are generally oversized, resulting in serious overload and burning of the distribution substation.

(3) Due to the large number of rural lighting lines in country, and mostly supply with single-phase power, coupled with the arbitrariness of jumper wires during construction and inadequate management, which cause the load of the distribution substation out of phase, and also make a phase coil insulation green aging and burned for longtime usage.

(4) The lightning arrester is not timely or not installed 10kV surge protector, which cause the destruction of the transformer while the lighting strike.

(5) Some of the substation is not configured with a level of protection, or configured with a level of protection but because of its mobility, low reliability, or even can not move at all, which make the low protection of the distribution cabinet.

(6) The lack of daily management of the distribution cabinet which cause the aging of the device

2.-The precautions of the burnout for distribution cabinet

(1) A high voltage fuse and low voltage fuse should be installed in the new construction. In operation, when the fuse is found to be burnt out or burnt out, it should be replaced in time.

(2) Strengthen electrical load measurement work, to measure the load of each distribution cabinet in the peak period with a clamp-on ammeter and adjustment of load reasonable , to avoid three-phase unbalanced partial load operation.

(3) As for the voltage error of the low-voltage side of the 10kV distribution substation in the range of +7% to 10%, it is generally not allowed to adjust the tap changer.

(4) Before the thunderstorm season every year, all the lightning arrester should be sent to the repair test gate for testing and timely installation after passing the test.

(5) For the new distribution cabinet, it is forbidden to run the network without passing the field test by the repair and test department, so as to avoid burning the new device due to quality problems or improper transportation.

In short, the quality of the distribution cabinet, has direct contact with the management.Choosing the right and safe components is the basic for the distribution cabinet and the after maintenance is also important.It’s not just about human life , but also the workplace, everywhere in our life, how to avoid the accidents is an important lesson.

The installation of the distribution Cabinet

Installation, commissioning and maintenance of low-voltage distribution cabinet equipment

1.-Installation and commissioning of low voltage distribution cabinet equipment

The Low-voltage distribution cabinet should carried out for trial operation debuggingafter its installation, debugging is divided into mechanical debugging and electrical debugging two parts.

(1) electrical component debugging

Commissioning of electrical components mainly includes electrical operation test, interlocking function test, insulation test, etc. The electrical operation test is a simulation test according to the design system diagram, which simulates the power-on test, that is, to simulate the power on test, mainly to test the circuit breaker, contactor, relay, air switch and other electrical components of the split, if the the gate close is normal, the control button is correct, the indicator light is normal, the manual operation is normal, the protection action is sensitive and accurate.

(2)mechanical component debugging

Mechanical parts debugging is mainly manual operation part and drawer type function test, to check whether the operation mechanism is flexible and reliable, especially the check of the drawer connection, the reliability of its disconnect position is particularly important, the merits of its performance directly affect whether the distribution cabinet can run normally or not.

① Drawer should be flexible in pushing and pulling, no jam collision phenomenon, centerline consistent of , close contact of the dynamic and static contact, the forward put into use of grounding contact than the main contact, and exit than the main contact after disengagement.

② The switching joints and mechanical interlocks of the secondary circuit should operate flexibly and reliably.

Installation and commissioning of low voltage distribution cabinet
Installation and commissioning of low voltage distribution cabinet

2.-The maintenance of Low voltage distribution cabinet

① check whether the drawer switch is flexible to push in or pull out, its mechanical locking is reliable, the contactor contacts are good.

② check whether the circuit breaker blade elasticity is normal, the arc extinguishing device is intact.

③ check whether the cable head wiring nuts are tight.

④After the disconnecting of the main switch of the the receiving cabinet and contact cabinet , it should be flexible with a special shake out or shake out, the secondary terminals such as the mutual inductor contact good fastening without loosening, a second line,with no mildew.

maintenance of Low voltage distribution cabinet

Conclusion

From the era of a single oil lamp to the present time, it seems that people can no longer accept to live without electricity. We often see power distribution cabinets, such as throughout commercial buildings, residential areas, power plants, mining plants or construction sites, etc. In order to ensure the safety of electricity, power distribution boxes must be used in everywhere in our life.

Any related with electricity, the most important is the safety. Everyone will know this point that the distribution cabinet can not use combustible material production,. Distribution cabinet must ensure the safe use in a certain situation,, even if the accident should also be able to keep in a certain control range.

distribution cabinet

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