How are N1 and N2 faults defined in the grid, respectively

The n-1 mode of operation refers to the power system.

After any of the independent components (generators, transmission lines, transformers, etc.) in n components fail and are removed, they should not cause power outages due to overload tripping of other lines, do not destroy the stability of the system, and do not cause accidents such as voltage collapse;

N-2 operation mode means that after any two independent components (generators, transmission lines, transformers, etc.) in the N components of the power system are faulty and removed, they should not cause power outages due to overload tripping of other lines, do not destroy the stability of the system, and do not cause accidents such as voltage collapse.

It is clear that the N-2 operates more securely and reliably than the N-1.

Within a certain range of the power grid, for a certain type of equipment or a certain type of component, when only one of them is allowed to fail (or return) so as not to affect the power supply to the user or the subordinate power grid (one more will affect the normal power supply), this operation mode is called the N-1 mode of the equipment (or components) in the range. N-2 is the one that allows the failure or return of 2 pieces of equipment or components without affecting the continued supply of power to the consumer or the lower grid. And so on n-3, n-4,。。

As a simple example, there is a double-circuit connection line between two substations, which is n-1 for the line, because one of them fails, and the other can still maintain power; In the case of a three-circuit line, it is n-2 for the line, because even if two of the lines lose power, the electrical connection between the two substations remains uninterrupted.

Of course, this is just a simple explanation, and there should be a concept of capacity in the strict sense. Taking the above line example, strictly speaking, the transmission capacity of the three lines should be the same, and the capacity of one of the lines should be the premise. If the capacity is not the same, the situation is complicated, and each piece of equipment should be numbered, and the conditions of n-1 and n-2 should be given separately for each line when it is out of service.

Of course, it is also possible to simply set the conditions according to the minimum capacity of the device, so that any equipment failure can be satisfied.

Your question is a bit problematic, whether it's n-1 or n-2 or even n-n, put it on the grid, that's a description of risk tolerance. It said that when building a power grid, it should be designed in such a way that n power sources operate together, and when one power supply fails, the other power sources can ensure the safe operation of the power grid.

N-1 operation mode means that after any independent component (generator, transmission line, transformer, etc.) in the N components of the power system is faulty and removed, it should not cause power outages due to overload tripping of other lines, do not destroy the stability of the system, and do not cause accidents such as voltage collapse;

N-2 operation mode means that after any two independent components (generators, transmission lines, transformers, etc.) in the N components of the power system are faulty and removed, they should not cause power outages due to overload tripping of other lines, do not destroy the stability of the system, and do not cause accidents such as voltage collapse.

It is clear that the N-2 operates more securely and reliably than the N-1.

n-1 is commonly used in power system stability analysis calculations. The n-1 mode refers to the operation mode of the power system when it loses any line or transformer. It can be used as an operation mode to consider the thermal stability and transient stability of the power system.

N-1 principle.

A criterion for judging the safety of the power system. Also known as the Single Fail-Safe Criterion. According to this criterion, after any one of the n independent elements of the power system (generators, transmission lines, transformers, etc.) is removed due to failure, it should not cause power outages due to overload tripping of other lines; It does not destroy the stability of the system, and there are no accidents such as voltage collapse.

It can be seen that the N-1 criterion contains two meanings: one is to ensure the stability of the power grid; The second is to ensure that users get continuous power supply that meets the quality requirements. Judging from the current situation, ensuring the stability of the power grid involves the security of the entire power grid, and sufficient attention has been paid to the capital investment, operation mode and technical measures, but there are still deficiencies in understanding to ensure the continuous power supply of users, especially users in remote areas, resulting in a long-term passive situation in the production and operation of local power grids.

Power system.

The types of faults are divided into:

Attack: 1, broken line (open circuit) and neutral point.

Single-phase grounding that does not directly ground the system.

2. Single-phase short circuit, two-phase short circuit and three-phase short circuit of neutral point direct grounding system.

3. The frequency or voltage of the power grid exceeds the specified range.

4. The power system oscillates and the stable operation state is destroyed. Wait.