GPRS Based Networking (IEC 101-104) Utility in Distribution Automation

Modernized Distribution Automation System Communication is a part of Smart Grid (Internet of Electricity). Distribution Automation (DA) refers to a system that enables an electric utility to remotely monitor, coordinate, and operate distribution components in a real-time mode.  In a DA system, there are feeder automation options that include: demand side management (DSM), remote switch control, integrated voltage control, service restoration, feeder configuration, trouble call, fault location/isolation, load and safety checks.

Distribution Automation System can communicate via:

• Fiber
• UHF/VHF Radio
• PSTN
• Cellular (GPRS/3G).
• Microwave, WiFi, Satellite, and any others

For Power Distribution, there are advantages to use cellular mobile network:

• No need to consider geographic condition, easy for customers to deploy, saving time and construction costs
• Capable in harsh EMC circumstances
• IP based, easy deployment and remote management, diagnose and maintenance
• Always online to ensure reliability
• Low communication costs
• Fast transmission speed
• Low Consumption Cost

Different from SOHO cellular devices, for power system, cellular devices must be:

• Industrial Grade -- Robust in harsh outdoor environments (wide temperature/humidity range, vibration, harsh electromagnetic conditions )
• Auto-Recovery -- Reliable in unattended remote sites
• Safe -- Secured remote applications (support private APN, VPN, Firewall etc.)
• Intelligent -- Support various protocols, local data process, alarming

The project introduced below was about one of the biggest system integrator in China who needed a reliable and flexible networking method for power distribution system.

In this project, the big power system integrator who provided power companies with control system had got a new requirement from the power company that requested a smarter communication system for distribution lines. The power company wanted to build a control system with over 20,000 control units dispersed everywhere in the city, including above 5,000 distribution substations and over 10,000 on-pole switches. Besides, there were other automation equipments such as FTU (Feeder Terminal Unit). The whole system requested a highly reliable and flexible communication system for quick response and easy maintenance.

However, traditional cable-network method could not meet the requirement because to install cable in thousands of field sites was a costly way. Besides, this project allowed a response time within only 3 seconds for these dispersed units which made radio system an unrealistic solution. Additionally, the project must be finished before winter (only 3 month left), therefore the communication system should be easy for construction work.

With deep understanding of the project requirements, InHand Networks proposed GPRS based solution. At the remote field of on-pole switch, InHand Networks provided embedded GPRS modem InDTU332GS55 which was a customized chip and could be installed within the RTU of integrator. At the remote field of substation, we used standard model of InDTUGS55 GPRS modem which was compact designed and could be installed in the electric cabinet in the substation. All the control units were connected with InDTU332GS55 with RS232/485 serial, and then , with universal GPRS coverage, SCADA center could get access to any field without additional network construction (to realize this, there should be private APNs which enable your devices within the same virtual private network or VPN, and your devices and SCADA center could access to each other through internet, the private APN could be get by using special SIM card get from local mobile operator).

InHand products InDTU332 fully meet the requirements of power distribution automation on both networking side and working condition side:

1.Robust in harsh outdoor environments:

• Wide operating temperature:-25-70℃, Humidity: 95% RH
• Strict EMC features specially designed for Power System
• Support wide power input: 5-35V DC, both with power terminal
• Long MTBF (over 30 years!) with high reliability, significantly reducing maintenance costs for customers

2.Reliable link with link detection and auto-recovery

3.Low power consumption design specially for renewable energy system, help to cut energy costs and reduce failure rate of monitor system:

• InDTU 332: Peak/Operating < 0.5 W; Standby < 0.8 W

4.Compact design, DIN-rail mounted, easy fit into control cabinet;

5.Proven by high-end customers including ABB, Siemens, Schneider Electric, China State Grid, etc.;

6.Easy configuration for installation works;

7.Centralized management service via InHand Device Manager Platform makes communication costs under control (learn more at:http://g.inhandnetworks.com).

8.VPNs provide with high-secured tunnel for UP/DOWN data flow;

9.Support IPSec/PPTP/GRE/L2TP/OpenVPN;

10.Firewall prevent hackers’ attacks.

InDTU332 series industrial serial to GPRS modem