# Design of Micro-Phasor Measurement System to Identify Phasor of Distribution Transformers
## 6 Conclusions  
The DMMS is the essential data system of the Taipower distribution system. However, because the data contained are digitalized from conventional blueprints, the phasor of distribution transformers marked in the database is often inconsistent with that identified on site, creating difficulties in system operation, maintenance, and planning for the Taipower. In addition, the prevalence of the underground distribution system and the elevated complexity of the distribution framework caused by increasing loads have incurred the difficulty for Taipower staff when conducting phasor identification. Therefore, this paper designed and developed a micro-phasor identification system and DMMS database property updating system to enhance convenienceness for the Taipower in phasor identification and data updating. A total of 102 distribution transformers in 15 underground distribution rooms in Kaohsiung Meishuguan area were selected as the targets for measurement, and the master station was established in Gushan Substation. After the on-site measurement and phasor identification of the 102 distribution transformers, conspicuous inconsistency was identified between the measurement results and the marked phasors provided by the DMMS. Specifically, only 29 distribution transformers exhibited phase consistency with that marked in the DMMS database, yielding a correct marking rate of 28.43%. Once phasor identification was completed, the content in the DMMS database was simultaneously updated. Overall, the inconsistency between the on-site and database measurements causes unsatisfactory operation efficiency of distribution system, suggesting a three-phase imbalance, excessive neutral currents, and increased loss in transmission lines.  
This paper also developed an APP to serve as an interface for the phase-measuring system. Phasor identification could thus be performed by connecting to the server through mobile communication network. Regarding the safety of on-site measurement, voltage sampling device was designed and installed at the secondary side of the distribution transformer to avoid operations under high-voltage environments. Moreover, voltage measurements were adopted as samples to prevent errors of phase angle offset caused by the load. Concerning time synchronization, because of the prevalence of underground distribution, GPS signals could not be received on site when Taipower staff performed basement measurements. A TCXO that underwent adjustments and compensation was adopted as the source of sampling signals in the system. The coordinated universal time provided by the GPS served as a reference time for the measuring units at both the reference and on-site measurement, and the empirical results demonstrated that the error subsequently produced was within the tolerance range of the Taipower. After the measurement was completed, the phase identification results were returned to the Taipower offices for subsequent DMMS database property updates.  
Conceptualization, T.-T.K.; Resources, Y.-R.C. and Y.-D.L.; Validation, C.-S.L.; Writing--original draft, T.-T.K.; Writing--review & editing, C.-H.L. This work was supported in part by the Ministry of Science and Technology of the Republic of China under the Contract MOST 108-3116-F-042A-004-CC2. The authors declare no conflict of interest.