Time overcurrent protection#
Block appearance in REPEAT VISION#
Time overcurrent protection (TOP) is a type of relay protection, the action of which is associated with an increase in the current strength in the protected circuit when a SC occurs in a section of this circuit. This type of protection is used almost everywhere and is the most common in electrical networks.
The operating principle of TOP is similar to the operating principle of IOP. If the current in the protected network increases, the protection system begins operating. However, while the IOP operates instantly, the overcurrent protection system only signals a trip after a certain period of time, called the time delay. The time delay depends on the location of the protected area. The shortest time delay is set at the area furthest from the source. TOP of the adjacent (closer to the energy source) section operates with a longer time delay, differing by a value called the selectivity stage. The selectivity level is determined by the protection’s operating time. In the event of a short circuit in a section, its protection is activated. If for some reason the protection does not work, then after a certain time (equal to the selectivity stage) after the start of the SC, the TOP of the section closer to the source will work and will disconnect both the damaged section and its own section. For this reason, it is important that the selectivity stage be greater than the protection response time, otherwise the protection of the adjacent section will disconnect both the damaged and the working section before the damaged section’s own protection has time to operate. However, it is also important to make the selectivity stage small enough so that the protection can operate before the SC current causes serious damage to the electrical network.
The setting (or the current value at which the protection is triggered) is selected based on the lowest value of the current SC in the protected network (for different faults, the currents SC differ). However, when selecting the setting, the nature of the protected network’s operation should also be taken into account. For example, when electric motors restart after a power outage, the current in the network may be higher than the nominal value, and the protection should not disconnect it.
1. Properties#
Property |
Default Value |
Description |
Units of measurement |
|---|---|---|---|
Operation current |
800 |
– |
А |
Response time |
0.5 |
– |
s |
2. Inputs and outputs#
Parameters |
Input/Output |
Description |
Units of measurement |
Port type |
|---|---|---|---|---|
Current |
Input |
– |
А |
Automation |
Protection triggered(0/1) |
Output |
– |
– |
Automation |
In order to see the connection capabilities of the block, you need to go to page Description of block ports