GPRS Mobile Information Application of Distribution Transformer Comprehensive Tester

1 Introduction

Distribution transformers are the main electrical equipment that directly supplies power to customers in the distribution area. They are the key link in determining whether high-quality and reliable electricity can meet the needs of ordinary power customers. As the urban power grid meets the peak summer period, a large number of distribution transformers are damaged by overload, power loss increases, voltage anomalies, three-phase load imbalance, and low power factor. In addition, the growing awareness of power supply quality service among residents and commercial customers in the distribution area requires the application of mature GPRS communication-packet switching technology on the basis of the mature product-distribution transformer comprehensive tester that has been put into operation in recent years, forming a cost-effective solution-GPRS mobile information distribution transformer comprehensive tester system. Realize the main functions of remote and online distribution transformer monitoring, alarm, working condition statistics, analysis, etc., to eliminate power supply hazards, adjust the load of the distribution area, timely discover and locate distribution transformer faults, rectify abnormal line losses, and improve the economic operation level of the distribution network.

2 System Introduction The GPRS mobile information distribution transformer comprehensive tester can be integrated into the power consumption field service and management system together with large user terminals, residential meter readings, and substation meter readings (see Figure 1). It can also be a separate distribution transformer information management system, consisting of the GPRS distribution transformer terminal installed on the low-voltage side of the distribution transformer, the public communication network (GSM/GPRS), and the master station system.

Figure 1 Electricity field service and management system

2.1 Composition of GPRS distribution transformer monitoring system

The system consists of application server, database server, front-end machine and terminal, among which application server, database server and front-end machine constitute the main station, and the front-end machine consists of external communication part, manufacturer decoding analysis module and front-end machine communication service program (see Figure 2). The main station is set up in the provincial power company information center, and the main station and the mobile company's data center use optical fiber to exchange data. Power supply companies in various cities set up workstations to create files, inquire and statistical data through the web.

Figure 2 GPRS distribution transformer monitoring system

2.2 System software features

(1) Unified architecture and strong compatibility: The GPRS distribution transformer integrated meter, large user terminal, residential meter reading, and substation meter reading system use the same COM+/J2EE architecture. The system has strong scalability and can support a large number of terminals, which is convenient for the power marketing information system to integrate the processing of electric energy information from residents, public transformers, special transformers, and dedicated lines at all levels of the power grid.

(2) Supports a variety of other public communication methods, such as: SMS, CDMA, Ethernet , CMPP dedicated lines, program-controlled telephones, etc.

(3) Accurate power metering: In order to meet the performance assessment of line losses in the substation area, the terminal power metering part uses a dedicated metering chip and has passed the CMC certification (manufacturing metering equipment license).

(4) Abnormal information alarm and fault elimination management: The system classifies the abnormalities reported by the terminal according to content and importance, manages the defect handling process in a streamlined manner, and tracks and supervises the entire process.

2.3 Main functions

(1) Real-time data Measurement : three-phase voltage, current, neutral current; instantaneous active power (total, split phase) (secondary side), instantaneous reactive power (total, split phase) (secondary side), power factor; total forward active energy, total reactive energy, one-quadrant, four-quadrant reactive energy; total distortion rate of abc three-phase voltage; total harmonics of abc three-phase voltage split phase, and harmonic components of 3, 5, and 7 split phases; total harmonics of abc three-phase current split phase, and harmonic components of 3, 5, and 7 split phases; current unbalance (definition: (imax-imin)/imax).

(2) Cumulative daily data statistics: daily voltage, current, zero-sequence current, active power, reactive power, power factor, voltage distortion rate, maximum and minimum values ​​of 15-minute average current; maximum and average values ​​of total current harmonics, apparent power, and current imbalance; minimum and average values ​​of total power factor; daily active power and reactive power; average voltage; monthly cumulative value of power outage time; monthly cumulative qualified rate of daily voltage.

(3) Cumulative monthly data statistics: monthly voltage exceeding upper and lower limits, voltage qualified rate, average voltage, number of voltage phase failures, operating time and total time of each phase, number of relay inputs, total power outage time, monthly active and reactive power.

(4) Hourly data records: hourly voltage, current, total active and reactive power, active and reactive power per phase, power factor, total active energy (base), voltage distortion rate.

(5) Real-time alarm function: power failure and power supply alarm. The monitor is equipped with a rechargeable battery. After a power failure, it can send at least three alarm messages to the main station; phase failure and phase loss alarm; reactive compensation failure alarm; overload limit alarm (judgment duration 3 to 5 minutes).

(6) SOO event records such as phase loss, power failure, capacitor switching records: record relevant information before and after phase loss, power failure, and capacitor switching (such as reactive power, voltage, action reasons, etc.).

(7) Data preservation: It can save the daily and monthly statistical data of the last two months and the hourly record data of 40 days. The data will not be lost after power failure.

(8) LCD panel display : The LCD panel of the distribution transformer monitor has a menu mode and can display the following contents: communication parameters, communication status (preferably with LED display status), signal strength; current working power supply working status, output circuit (reactive compensation signal) working status, real-time calendar clock ; real-time electrical parameters, power failure time of the month, and voltage qualification rate of the month.

(9) Monitoring and control of reactive compensation capacitors: The distribution transformer monitoring instrument has two groups of three-phase and one group of phase capacitor switching command output interfaces , which can realize group and phase/three-phase switching of capacitors by controlling external contactors or composite switches . The monitoring instrument can monitor the operating status of each group of capacitors, and optimize the switching of capacitors according to the set parameters and control strategies based on the real-time reactive power and voltage.

(10) Advanced application functions: Interface with the power marketing information system, calculate the power supply of the substation area according to the meter reading date of the substation area, and calculate and analyze the line loss rate of the substation area; Distribution transformer operating condition analysis: It can manage the extreme values ​​and over-limit time of indicators such as current, voltage, power, power factor, load rate, three-phase imbalance rate, power supply reliability, etc. in any period of time; Abnormal information alarm and fault elimination management: The system classifies the abnormalities reported by the terminal according to content and importance, manages the defect handling process in a streamlined manner, and tracks and supervises the whole process, and generates monthly distribution transformer defect handling monthly reports.

2.4 Communication Network

The system uses GPRS as the main communication method. Its data Communication is charged according to the amount of data sent and received. By signing a strategic cooperation agreement with a mobile company, a monthly fee is charged based on traffic volume, so that the distribution transformer comprehensive tester terminal is online 24 hours a day, just like the distribution maintenance personnel on duty around the clock. It also has the following advantages:

(1) Quick login: After the terminal is powered on, it will automatically complete the connection with the GPRS network and quickly log in to the main station.

(2) High-speed transmission: Due to the application of packet switching technology, the maximum theoretical value of data transmission is 171.2kb/s.

(3) Automatic switching: The communication method between the terminal and the main station can automatically switch between the GPRS and SMS (short message) channels to ensure unimpeded network operation.

3 Conclusion This paper discusses the composition and main functions of the GPRS mobile information distribution transformer comprehensive tester system, and provides a set of mature systems that conform to the actual work to improve the automation level of urban distribution networks and the performance evaluation management of platforms and lines. After more than a year of operation, it has been proved that the development and application of the GPRS mobile information distribution transformer comprehensive testing instrument system can effectively strengthen the online monitoring, alarm, defect handling of distribution transformers and the work of reducing losses and increasing efficiency of distribution networks.