Overcurrent protection relay function
1 inverse time over current protection
The setting of the inverse time overcurrent protection includes the setting of the curve shape, the starting value, and the inverse time time factor.
2 short delay overcurrent protection
The short delay fault protection function corresponds to the short circuit condition fault, and the setting items are current start value setting and delay setting. The former protects the overcurrent current level at the beginning of the timing, and the latter is the time from the start of the timer to the trip of the action.
3 instantaneous action protection
The instantaneous action protection corresponds to a large fault current situation, and the response time to the fault is generally designed to be two cycles.
4 Ground fault protection
Ground fault protection generally has the following three protection settings
1. Inverse time overcurrent curve, starting value, time setting;
2. Short delay overcurrent protection startup value and time setting;
3. Instantaneous action protection start value.
5 overload warning
When the load current reaches a certain value of the phase element reverse time overcurrent start value, the overload function starts timing and monitors and controls.
6 Phase-to-phase ground inverse time/short delay protection has an area selection interlock function.
Overcurrent protection action principle
The overcurrent protects the component by an overcurrent protection action.
The overcurrent protection is generally divided into definite time and inverse time overcurrent protection, current fast breaking protection, and single phase grounding protection of the neutral point ungrounded system.
It consists of measuring components, which are used to judge whether the line current exceeds the standard. The time relay is a delay element. It uses appropriate delay to ensure that the device operates selectively. The signal relay is used to send a protection action signal.
In normal operation, both the current relay and the time relay are disconnected. When the protected area is faulty or the current is too large, the current relay acts, and the time relay is activated through its contact. After a predetermined delay, the time relay contact Closed, the circuit breaker is tripped, the circuit breaker trips, the fault line is cut off, the signal relay is activated, the signal board is dropped, and the light or sound signal is turned on.
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