Usage conditions for insulation coordination of low-voltage complete equipment

Release time:

2021-10-18

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Abstract

Insulation coordination refers to the selection of electrical insulation characteristics based on the operating conditions and surrounding environment of low-voltage complete equipment. Insulation coordination can only be achieved when the design of the equipment is based on the strength it will endure during its expected lifespan. The issues of insulation coordination arise not only from external factors related to low-voltage complete equipment but also from internal factors, involving multiple aspects that need to be considered comprehensively. The key points are divided into three parts: first, operating conditions; second, operating environment; and third, selection of insulation materials.

Insulation coordination refers to the selection of electrical insulation characteristics based on the usage conditions and surrounding environment of low-voltage complete equipment. Insulation coordination can only be achieved when the design of the equipment is based on the strength it will endure during its expected lifespan. The issues of insulation coordination arise not only from the external factors of low-voltage complete equipment but also from internal factors, involving multiple aspects that need to be considered comprehensively. The key points are divided into three parts: first, usage conditions; second, usage environment; third, selection of insulation materials.Low-voltage complete equipment的使用条件和周围环境来选择电气绝缘特性，只有当设备的设计基于其在预期寿命内所承受的作用强度时，才能实现绝缘配合，绝缘配合的问题不仅来自低压成套设备的外部，也来自自身，涉及到多方面的因素，需要综合考虑。其要点分为三个部分:一是使用条件;二是使用环境，三是绝缘材料的选择。

1. The relationship between insulation coordination and voltage. When considering the relationship between insulation coordination and voltage, it is necessary to consider the possible voltages in the system, the voltages generated by low-voltage complete equipment, the required continuous voltage operating level, as well as personal safety and accident risks.

1. Classification and waveform of voltage and overvoltage.

A. Continuous power frequency voltage of constant r, m, and s.

B. Temporary overvoltage, power frequency overvoltage with a longer duration.

C. Transient overvoltage, which lasts for a few milliseconds or shorter, usually high-damping oscillation or non-oscillation.

2. The relationship between long-term AC or DC voltage and insulation coordination should consider rated voltage, rated isolation voltage, and actual working voltage. During normal long-term operation of the system, both rated isolation voltage and actual working voltage should be considered to meet standard requirements while also paying attention to the actual situation of China's power grid. Currently, the quality of China's power grid is still not high; therefore, when designing products, the actual possible working voltage is more important for insulation coordination.

The relationship between transient overvoltage and insulation coordination is related to the conditions for controlling overvoltage in electrical systems. There are various overvoltages present in both high and low-voltage complete equipment that need to be considered. In low-voltage power systems, overvoltages may be influenced by various variable factors; thus, assessing overvoltages in the system through statistical methods reflects the concept of occurrence probability, and whether protection control is needed can be determined through probability statistics.

 

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