IEC62056 | Communications Protocols | Interface (Computing)

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  ACTA ELECTROTEHNICA 238  IEC 62056-21 protocol based, Energy  Meter Integration on OPC Data Access environment  Florin DRĂGAN, Romul COPÎNDEAN and Rodica  HOLONEC     Abstract: The International Electrotechnical Commission’s IEC 62056-21 standard suite describe direct local connections physical layer and communication protocols used for Electricity energy metering -Data exchange for meter reading, tariff and load control. This article describe a simple meter reading example, using optoisolated serial readout circuit and a software application using OPC Client/Server environment solution. The system contains an energy meter (Actaris ACE 5000 family), one optoisolated serial adapter connected to a process computer via serial communication port. The computer runs an application developed under OPC Server environment, used for interface, channel protocol and device configuration and data acquisition reasons. OPC server environment can integrate different devices interfaces and communication protocols and provides different parameter values as abstract information. These information may be transferred to another computer station and used to be displayed by hardware or software based HMI device, as can be see below. Some tricks and configuration details are also presented.   Keywords:  Energy meter reading, DLMS/COSEM, OBIS codes, Data exchange, OPC platform, HMI    1.   INTRODUCTION   There are many energy meter applications based on devices equipped with communication interfaces  providing measurement information. Interfaces, either simple direct wired / optical isolated serial, or complex wired / wireless network types, enable suppliers to  periodically read and/or control remotely, using appropriate devices and applications. In some cases, continuous measuring and monitoring are needed, at customer’s premise. A simple solution is based on serial and IEC 61107 optical port connected to a computer running OPC.[1] 2.   S ERIAL COMMUNICATION CIRCUITS Some energy meters are equipped, either optical isolated open collector and emitter transistor, or infrared output LED. Both solutions are similar, there are only few differences, as shown in figure 1. Fig. 1. Optoisolated serial port readout circuit Based on RS-232 (EIA/TIA) serial port status and control output signals, some tricks can be used to supply simple data communication circuit. The +Vcc and –Vcc power are supplied by computer’s RS232 DTR=ON and RTS=OFF signals, respectively.[2] Serial port and communication test The power meter used in this example (Actaris ACE5000 family) need following serial communication settings, according to ISO/IEC 1177:1985 [1]:  baud rate 1200 bps; 7 data bits;  parity even; 1 stop bit. After plugging the cable adapter and powering up the computer and energy meter, it is possible to test the connection by using DOS emulated command line (on Windows command prompt). Pressing Start> Run>cmd and typing mode command line with appropriate  parameters, a message is printed on screen. C:\ ..default folder >mode com1: baud=1200 data=7 parity=e sto p=1 dtr=on rts=off <ENTER>Status for device COM1: ----------------------- Baud: 1200 EnergyMeter Data AcquisitionComputer  + outputpulse port -- DTRDSR, DCDRXDCTSRTS 2k2 ACE5000a) EnergyMeter Data AcquisitionComputer outputopticalportDTRDSR, DCDRXDCTSRTS 2k2 ACE5000b)  Volume 55, Number 3-4, 2013 239 Parity: Even Data Bits: 7 Stop Bits: 1  Timeout: ON XON/XOFF: OFF CTS handshaking: ON DSR handshaking: OFF DSR sensitivity: OFF DTR circuit: ON RTS circuit: OFF After com1 port configuration session, we can read the exported frame, containing energy meter  parameters. The device automatically transmits (periodically about 10s time stamp) the user configurable, clear readable ASCII text, information frame, as show below. C:\..default folder>copy com1: con <ENTER> C.1( 00083115) C.1.1( ) 169.1(009-015-014-102-010-000) C.50.2(02) 11.35.1(008*A) 1.0(0 11-06-0212:32:47) 15.8.1(000002.318*kWh) 15.8.2(000000.000*kWh) 15.8(000002.318*kWh) 15.8.1*1(000002.318*kWh)(0 11-06-0112:45:53) 15.8.2*1(000000.000*kWh)(0 11-06-0112:45:53) 15.8.0*1(000002.318*kWh)(0 11-06-0112:45:53) 2.8.1(000000.000*kWh) 2.8.2(000000.000*kWh) 2.8(000000.000*kWh) 2.8.1*1(000000.000*kWh)(0 11-06-0112:45:53) 2.8.2*1(000000.000*kWh)(0 11-06-0112:45:53) 2.8.0*1(000000.000*kWh)(0 11-06-0112:45:53) 3.8.1(000001.005*kvarh) 3.8.2(000000.000*kvarh) 3.8(000001.005*kvarh) 3.8.1*1(000001.005*kvarh)(0 11-06-0112:45:53) 3.8.2*1(000000.000*kvarh)(0 11-06-0112:45:53) 3.8.0*1(000001.005*kvarh)(0 11-06-0112:45:53) 1.6.1(000.000*kW)(0 11-06-0112:45:53) 1.6.2(000.000*kW)(0 11-06-0112:45:53) 1.6.1*1(000.540*kW)(0 11-05-1016:30:00) 1.6.2*1(000.000*kW)(0 11-05-0619:30:07) 1.6(000.000*kW)(0 11-06-01 12:45:53) 1.6.0*1(000.540*kW)(0 11-05-10 16:30:00) C.8.1(00000872*min) C.8.2(00000000*min) C.8(00000872*min) 32.7(216*V) 52.7(222*V) 72.7(215*V) 32.26(239*V) 52.26(238*V) 72.26(240*V) 31.7(000*A) 51.7(000*A) 71.7(000*A) 31.6.1(002*A) 31.6.2(000*A) 51.6.1(002*A) 51.6.2(000*A)  ACTA ELECTROTEHNICA 240 71.6.1(002*A) 71.6.2(000*A) 31.6(002*A) 51.6(002*A) 71.6(002*A) 15.7(000.000*kW) 1.16(002.440*kW) 9.7(000000*VA) 9.14(000000*VA) 13.7(+1.00) 33.7(+1.00) 53.7(+1.00) 73.7(+1.00) C.2(00005) C.66(00005) C.7(043) C.5(000000) ! This message contains the short OBIS code (as defined by [3, 5]), of a parameter, value and measure unit, separated by special characters. Each parameter is  printed in separate line, ended by a pair of <CR><LF>characters. 3.   IEC 62056-21 PROTOCOL FORMAT IEC 62056-21 international standard provides electrical, mechanical and data exchange specification support. There is a few protocol versions described in this standard, but this device uses protocol format D. Data exchange is unidirectional in protocol mode D and permits readout only. The information flows from the tariff device to the HHU. Data transmission is initiated, for example by operating a push button or other sensor on the tariff device [1]. In this case, the device transmits data periodically, without any other action. The readout data message is a simple line based  parameter sequences string, with start/end delimiter characters. To avoid data errors during transmission, a  block check sequence is also used. The general message frame format is show in table 1. Table 1. name STX Data  block ! CR LF ETX BCC code 0x02 variable 0x21 0x0D 0x0A 0x03 0x?? Data block contain a variable number of data sets, depending on user configurable device settings. A data set can be represented in one or more lines, separated  by <CR> and <LF> characters, if needed. Each data line can contain maximum 78 characters (80 with <CR> and <LF>). The data set format is show in table 2. Table 2. OBIS code  ( Param. Value * Unit ) CR LF variable 0x28 variable 0x2A Var. 0x29 0x0D 0x0A To extract interested parameters, provided by measure device, the received data message must be split into data sets and each data set into parameter value and measurement unit. This paper describes a sample solution, based on OPC DA environment, which solve the desired problem.[1] 4.   OPC DA IMPLEMENTATION OPC (OLE for Process Control) was developed to allow devices with different interfaces, channels and  protocols, to be integrated in a single remote data acquisition and monitoring virtual system. There are many application packages provided by software developer companies, in this paper Kepware’s OPC Server product is used.[6] The main parts are KEPServerEX with U-CON (User Configurable) driver, for connection support and data acquisition, and Infilink HMI (Kessler Ellis Products) for “user friendly” graphic interface.[8] To create an application project, several tasks must be performed. OPC Server configuration involve channel (interface and appropriate protocol), device and tags properties configuration, as shown in figure 2-4. User Configurable Driver allows programmers to create the script according to dedicated protocol to be used. Because energy meter device transmits  periodically data frames, without any external command, the unsolicited mode must be selected.[7] Fig. 2. OPC Server configuration, main window Serial port communication parameters must be configured according to the energy measurement device  Volume 55, Number 3-4, 2013 241 specifications (baud rate, parity, data bits etc.). The readout circuit, as shown in figure 1, must be electrical supplied by using unusual DTR flow control. Fig. 3. OPC Server channel configuration. Device configuration requires to setup some  parameters like name, device identification and different time stamps indispensable to accommodate reading sequences to energy meter data transmission. One of the most important piece is the transaction editor. In the left window, it is necessary to create a read tag block, containing each parameter (tag) exported by meter device. All this tags are read together in a single data frame.[7] Fig. 4. OPC Server device configuration After defining all tags and their parameters, the next step is to create the chat script, that mean a sequence of write, read, conditional and processing commands. The script allows drawing out each  parameter (tag), as shown in figure 5-6. Fig. 5. OPC Server device configuration. Transaction editor main window Fig. 6. Transaction editor’s chat script Fig. 7. OPC Quick Client tags table window For testing reason or simple reading interface.  prior to make the graphic interface, OPC Quick Client can be used. OPC Server application can starts and automatically configures the Quick Client that can display parameters (tags values) in table format, as shown in figure 7. 5.   R ESULTS   Infilink environment allows creating many graphical objects attacked to imported tags from OPC Server. As an OPC client, this application can communicate with server running on same computer, or on another one, using network through OPC and TCP/IP protocols.
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