Functional Overview

The JLB-HPU automatic phase-switching device for three-phase unbalance compensation (an automatic low-voltage load phase-switching system) consists of an intelligent phase-switching terminal (responsible for load monitoring and automatic control) and multiple phase-switching switch units (actuators responsible for executing load phase switching). The intelligent terminal monitors the three-phase currents of the distribution transformer's low-voltage output in real time. If the three-phase load unbalance exceeds limits within a specific monitoring period, the terminal collects real-time data—including currents and phase sequences—from the transformer's low-voltage output and the individual load branches of the switch units. It then performs optimization calculations and issues optimal phase-switching commands. The switch units execute the switching operations according to the prescribed procedure, thereby adjusting user load phase assignments and balancing the three-phase load across the distribution area.

Applicable Conditions

①　Three-phase load unbalance in the distribution area is caused by the random fluctuation of specific loads and is difficult to rectify through routine operation and maintenance measures.

②　The power factor on the low-voltage side of the distribution transformer is greater than 0.85.

③　The low-voltage main lines and primary branch lines of the distribution area utilize a three-phase power supply configuration.

④　There are no sensitive loads requiring high reliability within the power supply coverage of the phase-switching switches.

Performance indicators

①　The measurement accuracy of the device's current transformers is Class 0.5 or better.

②　During the commutation process of the commutation switch unit, the voltage interruption time does not exceed 20 ms; the rated operating current is at least 100 A, and the total power loss of the unit is no more than 10 W. The unit features a mechanical interlock across phases A, B, and C to prevent phase-to-phase short circuits.

③　The commutation switch unit has a mechanical lifespan exceeding 100,000 operations and an electrical lifespan exceeding 50,000 operations.

④　The commutation switch unit supports both networked operation with a commutation control terminal and standalone operation.

Product Features

It offers high reliability and utilizes zero-crossing, arc-free switching technology to easily handle heavy loads. It supports manual on-site phase switching and circuit disconnection, and features comprehensive protection functions against short circuits, overcurrent, overvoltage, undervoltage, and earth leakage. The device acquires on-site data—including three-phase input/output voltages, current, phase, and switch status—and transmits this information in real time. It supports multiple communication methods, such as RS485, short-range wireless, and power line carrier (PLC), and allows for the remote configuration of protection and phase-imbalance adjustment parameters.