Tham khảo tài liệu 'power quality monitoring analysis and enhancement part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Power Quality Monitoring in a System with Distributed and Renewable Energy Sources 63 Fig. 2. Power grid with the nodes at which it is possible to combine protection functions with power quality analysis 2. Integrating power quality analysis and protection relay functions The main issue in the development of protection relay integrated with power quality analyser is the necessity to elaborate efficient algorithms for line voltage and current signals frequency spectrum determination with harmonic and interharmonic content up to 2 kHz. The mass use of power quality monitoring postulated in the previous paragraph demands that incorporation of power quality analysis functions into protection relay comes at a negligible additional cost to the end user. The cost of the additional hardware has thus to be as low as possible with the burden of extra functionality placed on the software. Modern microprocessor controlled protection relays employ sampling of analogue current and voltage signals and digital signal processing of the sample sequences to obtain signal 64 Power Quality - Monitoring Analysis and Enhancement parameters like RMS which are then used by protection algorithms. In this respect they are similar to stand alone power quality analysers that also carry out the calculations of signal parameters from sample sequences. The availability of fast and high resolution analogue to digital converters enables cost effective signal front end design suited equally well for protection relay and power quality analyser. Fig. 3. Block diagram of combined protection relay and power quality analyser The architecture of combined protection relay and power quality analyser has been shown in Figure 3. The architectures of power quality analyzer and protection relay are very similar. They differ only in the transient voltage surge measurement module which has been marked by a different colour in Figure 3. while the basic signal parameterization software implemented in both devices .
