Instrument grounding issue

Two cores are sufficient for armored cables; the PE conductor can be connected to the armor layer. If there is no armor, it is better to use three cores. For details, refer to clause 7.2.7 of SHT-3082-2019

In the installation of electrical equipment, grounding (also known as ground protection or shock protection) is a very important safety measure. For analytical instruments powered by 220VAC, it is indeed proper to use a 3-core cable with a PE (protective earth wire) to ensure safety. The following are the specific details: 1. The PE wire in a 3-core cable (the yellow-green colored wire, which is usually the protective ground wire) is used to connect the device’s casing to the ground, thereby preventing the casing from becoming charged in the event of a device failure and thus protecting human safety. 2. If a 2-core cable is used (i.e., only the phase wire L and the neutral wire N, without a protective earth wire PE), it is indeed necessary to run a separate cable dedicated to connecting the PE, in order to ensure that the equipment’s enclosure is properly grounded. This is also to meet the requirements of electrical safety regulations. 3. The instrument enclosures on site should also be grounded as close as possible, which means that in addition to the PE wire brought in from the control room, the instrument enclosures should also be connected to the on-site grounding system (if available) in order to provide a reliable grounding path along the shortest path. 4. If only a 2-core cable is installed on site without a protective ground wire, an additional cable must be installed to ensure the grounding continuity of the equipment. This is the right thing to do, as it complies with the safety installation standards for electrical equipment. Conclusion: The approach you described is correct. For safety reasons, it is necessary to ensure that analysis instruments powered by 220VAC are supplied via a 3-core cable, and that the equipment enclosure is properly grounded. If the cable wiring on site does not meet the requirements, measures must be taken to address it in order to ensure the safety of personnel and equipment. Safety is always the top priority in electrical installations; therefore, it is essential to follow relevant safety regulations and standard operating procedures. .

The shielding layer itself must be grounded, but it cannot be used as a substitute for the device’s PE wire; it is difficult to ensure reliability in terms of connection and cross-sectional area.

There is no separate PE wire; the instrument enclosure can be grounded nearby.

It's fine as long as your cable has a shielding layer

Temporary power supply can suffice for short-term use, but for equipment that will be used on a long term basis, it’s better to follow the relevant standards. There are no trivial matters when it comes to safety. In the event of a liability-related accident, if it is caused by non-compliance with regulations, the person responsible for the actual implementation cannot evade their responsibilities

Is a shielded cable suitable for three-core use?

With our previous 220VAC analyzer, we used a 2*1.0 shielded cable, where L and N were connected together and the shield served as the PE conductor; we found that the induced voltage was very high