Issues with strong and weak electricity

Conceptually, strong electricity and weak electricity are generally easy to distinguish, with the main difference lying in their different applications. High-voltage electricity is used as a power source, while low-voltage electricity is used for information transmission. Specifically, they differ in the following ways: (1) Different alternating frequencies. The frequency of high-voltage electricity is generally 50 Hz, known as the \"power frequency,\" which refers to the frequency used in industrial applications; whereas the frequency of low-voltage electricity is usually high or very high, measured in KHz (kilohertz) and MHz (megahertz). (2) Different transmission methods: High-voltage electricity is transmitted via power lines, while low-voltage electricity can be transmitted either wirelessly or through wires. Radio transmits via electromagnetic waves. (3) Different values for power, voltage, and current: Electrical power is measured in KW (kilowatts) and MW (megawatts), voltage is measured in V (volts) and KV (kilovolts), and current is measured in A (amperes) and kA (kiloamperes) ； Low-power electrical quantities are measured in W (watts) and mW (milliwatts), voltage is measured in V (volts) and mV (millivolts), and current is measured in mA (milliamps) and uA (microamps); therefore, such circuits can be constructed using printed circuits or integrated circuits. Of course, in high-voltage applications there are also high-frequency (hundreds of KHz) and medium-frequency devices, but the voltage is higher and the current is larger as well. Similarly, although flashlights and electric shavers have very low voltages as well as low power and current, they are still considered high-voltage devices. Due to the development of modern technology, low-voltage systems have penetrated into the field of high-voltage systems, such as power electronics devices and wireless remote control. However, these can only be considered as parts of high-voltage systems that are controlled by low-voltage signals; they remain distinct from the high-voltage systems they control. Low-voltage electricity is in contrast to high-voltage electricity; its focus is on information, namely the transmission and control of information. It is characterized by low voltage, low current, low power, and high frequency. For example, low-voltage electrical systems include communication network systems, television systems, fire protection systems, security systems, video systems, as well as the integrated cabling systems that serve these systems.

When rewiring the strong and weak electrical systems, a certain distance between them is required; there is no requirement that they cannot be placed in the same cabinet, and in most cases it is the weak electrical systems that control the strong electrical systems.

It is better to separate the control cabinets for high-voltage and low-voltage systems. Although national standards do not require such separation, there are requirements regarding electromagnetic interference; therefore, it is advisable to keep the low-voltage circuits separate in order to avoid electromagnetic interference from high-voltage systems.

Separating the strong from the weak is a concept among us engineers, yet it is very difficult in reality. For example, the grounding system – Siemens has not managed to achieve this despite working on it for decades.

National standards do not require separation; in engineering projects, separation is mainly done to address interference issues.