I. Equipment Overview

The BHG-CHE series microcomputer harmonic suppression device is a new intelligent harmonic suppression device developed and produced by our company to address the severe accidents of voltage transformers (PT) burning or even exploding due to ferromagnetic resonance in neutral point grounding systems without ground or through resistance and arc suppression coils at voltage levels of 66KV, 35KV, 10KV, 6KV, 3KV, and below. The device utilizes DSP as the core component for detection and control; employs high-power, non-contact elements for harmonic suppression; features a liquid crystal display (LCD) and signal indicator lights; and is equipped with intelligent software for more reliable operation, simpler handling, greater intuitiveness, and accuracy.

The device can monitor and display the voltage components of PT opening at four frequencies: 17Hz, 25Hz, 50Hz, and 150Hz in real-time. It can differentiate between overvoltage, ferromagnetic resonance, and single-phase grounding during faults and provide corresponding alarm signals; in case of resonance faults, it can quickly activate the detuning element to suppress the resonance; and it is equipped with a communication interface to transmit fault information to relevant departments, enabling remote control.

The current power system equipment is increasingly automated, demanding higher accuracy in timekeeping. In response, our company has developed the B-code time synchronization interface, featuring high timing accuracy, simple connectivity, and strong anti-interference capabilities. This interface allows for the synchronization of the device with the automated equipment's time within the station.

II. Working Principle

The device uses a DSP as its core to cyclically detect the PT open delta voltage (i.e., zero sequence voltage). Under normal operating conditions, this voltage is below the set value, and the high-power anti-resonance elements within the device remain blocked, having no impact on the system. When the PT open delta voltage exceeds the set value, it indicates a system fault. The device collects, analyzes data from the voltage transformer's open delta voltage, and determines the current fault status; if it's a ferromagnetic resonance at a certain frequency, it quickly activates the anti-resonance elements to eliminate it. In case of overvoltage or grounding, the device emits the corresponding alarm signal.

For various malfunctions, the device can separately provide alarm signals, display them, automatically record and store the relevant malfunction information, and report it to the superior computer.