# Optimization of Distribution Network Current Protection for Inverter-Based Distributed Power Access
## 6 Calculus Analysis
### Simulation Analysis of the Effect of IIDG Access on BC and CD Segments of Stage Current Protection  
1.1 Analysis of the Effect of Different Outputs of IIDG on the Protection of Electrical Flow Rate Disconnection  
In the event of a fault on line L1, the inverter-based distributed generation system (IIDG) is to be situated downstream of the protection device. The results of the simulation experiments provided further confirmation that the current impact of the inverter-based distributed generation system (IIDG) at different power output states on the Protection Device 1 is negligible in the event of a single-phase ground or two-phase short circuit fault occurring at several critical locations along the line BC (e.g., at 30%, 50%, and 80% of the line length). This finding is of significant importance in the evaluation of the influence of IIDG grid integration on the functionality of distribution network protection systems. The findings of this study indicate that the impact of inverter-based distributed generation systems (IIDGs) on the current interruption protection function of upstream protection devices is minimal and largely inconsequential.  
1.2 Analysis of the Effect of Different Outputs of IIDG on the Protection of Time-Limited Electric Flow Rate Disconnection  
Through simulation, the RMS value \(I_{protect1\_rms}\) of the fundamental current at Protection 1 is measured to evaluate the specific impact of different PV power plant output levels on the performance of time-limited flow current disconnection protection. The objective of this experimental design is to conduct a quantitative analysis of the impact of inverter-type distributed generation (IIDG) power fluctuations on the sensitivity of the flow current disconnection protection system. The findings will then be used to inform the optimization of distribution network protection strategies.  
The current flowing through Protective Device 1 demonstrates a declining trend as the output power of the inverter-based distributed generation system (IIDG) reaches its rated value. The time-limited current-failure protection of Protection Device 1 demonstrates high sensitivity in the absence of IIDG integration into the grid. This observation suggests that IIDG access may have a significant potential impact on current protection performance [24; 25; 27], providing a new perspective for understanding the impact of IIDG on the performance of distribution network protection systems. The sensitivity in the absence of IIDG access is as follows:  
\[K_{sen.1}^{II}=\frac{I}{I_{set.1}^{II}}=1.30 \tag{26}\]  
Following the establishment of a connection with IIDG, the alteration in the sensitivity of Protection 1 in the event of a fault at the BC end of the line is illustrated in Figure 6. Figure 6 presents the sensitivity curve of Protection 1, which is a fixed-time overcurrent protection.  
Figure 6: Comparison of minimum three-phase short circuit currents at different output levels (at the end of line BC).  
The analytical results presented in Figure 7 clearly indicate the effect of the output power of the inverter-based distributed generation system (IIDG) on the fault current and its protection sensitivity at Protection Device 1. This study reveals that the IIDG output power enhancement leads to decreasing sensitivity of time-limited current-failure protection at Protection Device 1, with a significant problem when the sensitivity is below the 1.3 threshold, and it continues to decrease. This phenomenon indicates that the IIDG output power enhancement has a significant negative impact on the sensitivity of the protection device, which emphasizes the need for further optimization of the protection system to ensure that it maintains its effectiveness under all operating conditions.