Low-voltage distribution cabinets play a vital role in the power system, mainly including the following aspects:
- Power distribution
Reasonable distribution of electric energy
Distribute the low-voltage electric energy from the transformer and deliver it to each power circuit according to the needs of different power equipment. For example, in a factory, the electric energy is distributed to different production lines, lighting systems, ventilation equipment, etc.
Through various switching devices and protection devices, ensure that the electric energy is distributed according to the predetermined path and capacity to avoid problems such as overload and short circuit caused by unreasonable distribution.
Improve power supply reliability
The low-voltage distribution cabinet can realize the switching of multiple power supplies and the automatic input of backup power supply. When the main power supply fails, it can quickly switch to the backup power supply to ensure the continuous power supply of important equipment.
The design of segmented busbar is adopted. When a certain section of the busbar fails, the faulty part can be isolated without affecting the normal power supply of other parts.
- Control function
Equipment start and stop control
Through the control elements such as contactors and relays installed in the low-voltage distribution cabinet, the start and stop control of various electrical equipment can be realized. For example, in the motor control circuit, the start and stop of the motor can be controlled by controlling the contactor’s attraction and release.
According to the requirements of the production process, complex control logic such as sequential start and reverse stop of the equipment can be realized.
Operation status monitoring
Various instruments and indicator lights are usually installed in the low-voltage distribution cabinet to monitor the operation status of the power system. For example, the voltmeter and ammeter can display the values of voltage and current in real time, and the power factor meter can reflect the power factor of the power system.
The indicator light can intuitively understand the operation status of the equipment, such as operation, stop, fault, etc.
- Protection function
Short-circuit protection
When a short-circuit fault occurs in the circuit, the short-circuit protection device (such as fuse, circuit breaker, etc.) in the low-voltage distribution cabinet will act quickly to cut off the fault circuit and prevent the fault from expanding.
The short-circuit protection device can cut off the fault current in a very short time (generally a few milliseconds to tens of milliseconds) to protect power equipment and lines from damage caused by short-circuit current.
Overload protection
When the load of the electrical equipment exceeds its rated capacity, the overload protection device in the low-voltage distribution cabinet will start, send out an alarm signal or cut off the power supply. The overload protection device can be adjusted according to the characteristics and load conditions of the electrical equipment to ensure that the equipment can be protected in time when the equipment is overloaded.
Overload protection usually uses thermal relays, electronic overload protectors and other devices, which can determine whether an overload fault occurs based on the magnitude and duration of the current.
Leakage protection
For some places with high requirements for personal safety, leakage protection devices will also be installed in the low-voltage distribution cabinet. When a leakage fault occurs in the circuit, the leakage protection device will quickly cut off the power supply to prevent people from electric shock.
The operating current of the leakage protection device is generally tens of milliamperes to hundreds of milliamperes, which can be adjusted according to different places and requirements.
- Metering function
Energy metering
Energy meters can be installed in low-voltage distribution cabinets to measure the power consumption of power systems. Energy meters can accurately record the power consumption of electrical equipment and provide a basis for billing and energy management of power departments.
Modern energy meters are usually high-precision and multi-functional, and can realize functions such as time-sharing metering and remote meter reading.
Power metering
In addition to energy metering, power meters can also be installed in low-voltage distribution cabinets to measure the active power, reactive power and apparent power of power systems. Power metering can help users understand the power factor of power systems and provide a basis for improving the efficiency and energy saving of power systems.
- Other functions
Improving power quality
Reactive compensation devices, such as capacitor banks, can be installed in low-voltage distribution cabinets to improve the power factor of power systems and improve power quality. The improvement of power factor can reduce line losses and improve the efficiency of power systems.
Equipment such as harmonic filters can also be installed to suppress harmonic pollution in power systems and protect power equipment and lines.
