Abstract
This paper studies the tolerance of electromagnetic relay (EMR) under voltage sag and short interruptions on the basis of response mechanism analysis and the extensive tests. First, it introduces the structure of EMR and proposes response mechanism of EMR under voltage sag. Then, a detailed test plan is presented, including the information of test platform, testing condition, EMRs used in test, list of test, test procedure, and the measured waveforms. Magnitude and duration of the sags are not only the characteristics to be considered to investigate EMR’s tolerance. The other factors, which may have significance influence on tolerance of EMR, are considered here, including point-on-wave (POW), phase angle jump (PAJ), harmonic, magnitude variation in pre- and post-sag segments, two-stage sag, and slow recovery sag. Extensive tests results are presented in the form of voltage-tolerance curves (VTCs). Besides magnitude and duration, POW, PAJ, and two-stage sag have a significant influence on the tolerance of EMR. Other factors only have a tiny impact on the tolerance of EMR. The results show that the magnitude tolerance of EMR is 48–74% of Unom, and duration tolerance is 5–28 ms; they are useful for the technical assessment of EMR’s tolerance to voltage sags and short interruptions, and for the economic assessment of the industry process trip due to its disengagement. Test results also benefit for choosing proper EMR and mitigation device in the complicated operating environment.
Highlights
Electromagnetic relay (EMR) is widely applied in industrial control system and communication as a kind of basic electric component, playing a role in switching circuits, transferring signals, and eliminating interference
Though there is a slight difference in voltage-tolerance curves (VTCs) of 45°, 135°, 225°, and 315° POW, they are almost coincident of the shape
When the sag magnitude is less than 48% of Unom, electromagnetic relay (EMR) will trip when the sag duration exceeds 28 ms
Summary
Electromagnetic relay (EMR) is widely applied in industrial control system and communication as a kind of basic electric component, playing a role in switching circuits, transferring signals, and eliminating interference. When a short-circuit fault occurs in the power system, it causes power quality issues, such as voltage sag and short interruption (Nagata et al, 2018; Wang et al, 2019; Ye et al, 2019), which affect the normal operation of EMR. Voltage sag even causes the malfunction and damage of EMR in severe cases (Wu and Fan, 2015; Jianbo and Qi, 2018), leading to the failure of the whole industrial process and resulting in the huge economic losses (Mohammadi et al, 2017; De Santis et al, 2018; Gambôa et al, 2019). (Bollen, 2000) records that the tripping of EMR under one voltage sag event “cause the shutdown of a large chemical plant, leading to perhaps $100,000 in lost production.”. It is important to understand the tolerance of EMR under voltage
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