WLD8801 Power Quality Online Monitoring Device. The Power Quality Online Monitoring Device is an intelligent device used for real-time monitoring, analysis, and evaluation of power quality in power systems. Its core functions include harmonic analysis, voltage sag/swell monitoring, flicker detection, and three-phase unbalance assessment. It is widely used in industrial, new energy, and smart grid fields. Type A: WLD8801A; Type B: WLD8801B.