7.2 Simulation result within the protected zone

Figures 14–23 show the results of an internal fault for the protected zone. The relay sends a trip signal to the circuit breaker under a faulty condition, and the circuit breaker isolates the zone relay from the rest of the protection scheme.

Innovative Differential Protection Scheme for Microgrids Based on RC Current Sensor DOI: http://dx.doi.org/10.5772/intechopen.85473


#### Figure 24.

The difference between the occurrence of a fault and a breaker signal.


#### Table 3.

Specifications of the proposed relay.

Figure 24 shows the time differences between the moment of a fault and signal of the breaker during and after the occurrence of the fault (Table 3). Displays the output of our proposed relay measurements; compared with the traditional behaviour in normal operation, the speed of our proposed scheme is less than one cycle.

#### 8. Summary

phase, namely, red, green, and blue for phases A, B, and C, respectively. The signal to Trip is represented as a binary (0, 1) measurement depending on the difference between the signals of the two ends for sending the signal to the circuit breaker. In Figures 10–23, two types of status are shown: for current differential and the

Figures 10 and 11 show the results of an external L-G fault on protection

Similarly, the results of external fault on the protection scheme in various fault conditions, that is, that mean the relay No sending trip signal to the circuit breaker.

Figures 14–23 show the results of an internal fault for the protected zone. The relay sends a trip signal to the circuit breaker under a faulty condition, and the circuit breaker isolates the zone relay from the rest of the protection scheme.

voltage differential, with the fault occurring at t = 0.3 ms.

Micro-Grids - Applications, Operation, Control and Protection

scheme. That is differential relays without sending tripping signal.

7.1 Simulation result outside the protected zone

Figure 22.

Figure 23.

128

3LGF voltage waveform.

3LGF current waveform.

7.2 Simulation result within the protected zone

The reliability of the relay protection system can be described in two respects: dependability and security. The reliability of the relay protection system detects and disconnects all faults in the protection zone. The safety of the relay protection system is capable of rejecting all events and transients that are not faulty so that the healthy part of the power system is not unnecessarily disconnected. Differential protection is the preferred solution for widespread use; fault protection for multiterminal systems becomes very difficult, and fast fault detection of systems becomes very important. This result provides different solutions for transmission line protection. This method is better than distance protection because differential protection requires fewer input data and reduces computation time.

The performance of this algorithm is more efficient than distance relay protection. The disadvantages of the distance on the transmission line and the directional over-current relay are as follows:

1. If a fault occurs at the end of the line, the relay cannot be disconnected immediately at both ends of the line.

2. Coordination is achieved by adjusting the time delay of the relays installed on the power line beside the primary protection and backup protection. Therefore, the delay time of the relay operating in each protection zone will slow down the termination of the interference.

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The differential protection principle is based on Kirchhoff current law, which has been widely used in the primary equipment protection of the power systems. The general objective of the protection system is to quickly isolate the areas that contain unrest while preserving the rest of the system. The method of protection must meet five criteria to perform successfully: (1) reliability, (2) selectivity, (3) speed, (4) simplicity, and (5) economy.
