How to distinguish between secondary and primary grounding

1. The working principle is different: repeated grounding.

is at the neutral point.

In a direct grounding system, a grounding device is connected with a metal wire at one or more points of the zero trunk. Secondary grounding, for strong electricity, the transformer has been grounded, if there is another ground wire indoors, it is called secondary grounding.

2. The wiring position is different: repeated grounding, the construction unit should ground the terminal of the zero trunk line and the branch line of the distribution line during installation, and the zero trunk line should be grounded every 1 km. Secondary grounding, from the perspective of electronic circuits, the circuit board can only be grounded at the thickest ground end, and cannot be grounded at a distance away.

3. The resistance limit is different: repeated grounding, the resistance should not be greater than 10 ohms. Secondary grounding, less restrictive.

Primary and secondary equipment include: generators (motors), transformers, circuit breakers, isolation switches, automatic switches, contactors, knife switches, busbars, transmission lines, power cables, reactors, etc., secondary equipment includes: transformers, measuring instruments, control devices, relay protection devices, etc.

The so-called primary and secondary grounding may be the grounding of these devices.

There is also the first grounding, and the second grounding. For example, in lightning protection grounding, some pipelines or structures are required to be grounded at a certain distance, and the concept of secondary grounding will appear.

It is impossible and unnecessary to distinguish because secondary grounding means repeated grounding. For safety reasons, connect the ground wire to the electrical housing part again.

Today, the technology of secondary grounding has gone far beyond the original concept of safe grounding. The reason is the "common ground" technology, which plays an immeasurable role in equipment safety, lightning protection, electromagnetic compatibility, etc. Especially the city.

TN-S zero-connection protection system.

In addition to repeated grounding at the distribution room or main distribution box, the protection neutral line must also be repeatedly grounded at the middle and end of the distribution line. That is, in the construction site, the repeated grounding device should not be less than three, and the grounding resistance value of each repeated grounding device should not be greater than 10.

Repeated grounding when the phase wire hits the shell can reduce the ground voltage on the neutral line; Repeated grounding in the event of a zero line break reduces the risk of electric shock; When the neutral line is broken and the three-phase load is unbalanced, repeated grounding can reduce the degree of damage to the electrical equipment.

Primary and secondary equipment include: generators (motors), variable trapped voltages, circuit breakers, isolation switches, automatic switches, contactors, knife switches, busbars, transmission lines, power cables, reactors, etc., secondary equipment include: transformers, measuring instruments, control devices, relay protection devices, etc.

The so-called primary and secondary grounding may be the grounding of these devices.

There is also the first grounding, and the second grounding. For example, in lightning protection grounding, it is required that some pipelines or poor pickpockets are built in a certain distance to be grounded at certain intervals, and the concept of secondary grounding will appear.

I don't know if your primary and secondary grounding are in that situation, it depends on the specific situation!

What is repeated grounding and secondary leased grounding:

1. Repeated grounding: In the system of direct grounding at the neutral point, the grounding device is connected with a metal wire in one or more places of the zero trunk line. In the low-voltage three-phase four-wire system neutral direct grounding line, the construction unit should ground the terminal of the zero trunk line and branch line of the distribution line during installation, and the zero trunk line should be grounded every 1 km.

For distribution lines that are more than 50 meters away from the grounding point, the neutral line at the access user should still be repeatedly grounded, and the repeated grounding resistance should not be greater than 10 ohms.

2. Secondary grounding: For strong electricity, the transformer has been grounded, if you play a ground wire indoors, it is called secondary grounding. In terms of electronic circuits:

The circuit board can only be grounded at the thickest ground end, and not at a distant distance, otherwise, there will be a voltage drop between the two virtual ground terminals, which will cause self-luck, interference and other problems.

There are two functions of repeated grounding: 1. In order to prevent the potential drift caused by the disconnection of the working zero line, the electrical equipment in different phases can form a loop with each other when the zero line is broken, and it becomes a series circuit. The equipment with low power burns out because of the high resistance and high voltage, and the equipment with high power cannot work because of the low voltage obtained by the small resistance; 2. In the protection zero connection system, if the zero wire is broken, all the zero connection equipment shells will be electrified.

Repeated grounding can reduce the chance of an electric shock.

Repeated grounding is to grounding the ground wire at an interval of a distance, it should be noted that repeated grounding is to protect the grounding wire or protect the neutral wire PEN wire, N wire is not allowed to be grounded again after the transformer is grounded, except for the PEN line, the PEN wire repeated grounding is also for PE repeated grounding, not for n repeated grounding.