Load Shedding Controller-ILD Datibase Monogement 四型回w The refinery facility power plant is an isolated GTG S power plant with four GTGs.Each GTG's full load is D Infnrmation ED Numbor GTG1 I0 Type GTG Leading(MW)0 00 around 40 MW.The actual output and rated output FNr DIF IP Addre车s Tel N am Mask are determined by online monitoring of out-going CB Status 100 192320g100 0000011 CB status,output,and ambient air temperature. CB-Commend 2 12p 201 0000000 GAII Normal operation condition is such that there is Da Nr DiF IP Address Poit Nr Puwer (MW) 100123203100380 4 always one generator serving as spinning reserve Temp (Deg C) 10012320100300 576 0T0 About 44 loads at 33/6.6 kV in 16 substations can CCPrnt Pesition in Priority List IED Nimber be controlled by the LSC.Their CB statuses are GIGI reported to the LSC by exception reporting.The CB GTG Ut21■Ust61■Ut101wt141■ status is then registered by the LSC.Subsequent A中 L3■u7目■t1■t5 load-shedding logic will exclude those CBs that are S5-0166kV94PM211C L41■851■t21■m161 SS-0166KV 94PMZ21A currently in an open position. Hoip DIUs send a life-sign signal to the LSC at a preset interval (normally 10 s).This signal is used to moni- tor the health of the communication link.If more Figure 5.LSC IED database than 6 life-signs are missing,the LSC will treat this connection as "down."Load-shedding logic also network might be critical for the system control deci- excludes those CBs that indicate a failed communica- sion-making.Monitoring the operating status of the tion link whole network and reporting the network communica- When communication is reestablished,a general tion failure becomes an essential function. request will be sent to DIUs to request update for all relat- In the LSC design,the simple network management ed CB status.The same applies to all GTG parameters. protocol (SNMP)is employed to monitor the LAN communication status.Network management of the LSC Configuration LAN consists of network management stations (man- The LSC application is running on a industrial PC with agers)communicating with network elements (IEDs). dual power supply and dual NIC.The operating system is The software in the network element that runs the Windows NT.SQL Server is used as the backend sup- management software is called an agent.The manager porting database.The application on the LSC PC is com- can ask the agent for a particular value,or the agent piled using C++.The SCADA server is running on Unix can report to the manager that something important Solaris with Siemens Spectrum SCADA software. happened (e.g.,an IED has failed);through this two- way communication,the status of all LAN communica- LSC PMI tion can be monitored.When a network component is The LSC person-machine interface (PMD)consists of dis- down,an error or warning message is sent to the con- plays that give the operator a current system situation trol center immediately to avoid system malfunction. overview as required for load shedding.It enables inter- action by input of selected parameters,such as priority Database Operation numbers,deactivation of sequences. A local database is used by the LSC to store power plant Device parameters are stored in the LSC local data- equipment parameters as well as historical event data. base.New devices (such as GTG.load.feeder)can be When the LSC starts,power plant information (including dynamically added or deleted through the IED data- IED name,DIU IP address,data communication telegram, base management display shown in Figure 5.The data mask,etc.)is transmitted from the SCADA server to the contains loads and generations,IED number,associat- LSC database.Different load-shedding priority lists and ed gateway number,load value,telegram number,and the current active list is stored in the LSC database as mask for the signal control.System parameters are well.In case communication with SCADA server is lost, also set up in this display.Using this screen,opera- the LSC will shed loads according to the information in tors can manually set and change and IED parameters. the database.During operation,important messages LSC parameters (such as the life-sign checking inter- (such as system alarms,communication abnormal,load- val,overload response time,and overload scan inter- shedding events)will be stored for future historical data val)are also configured in this display.LAN retrieval.Open database connectivity (ODBC)is used as connection parameters can also be modified for differ- a bridge between the LSC and the local database. ent systems. Figure 6 shows the main load-shedding active pri- Implementation Experience ority list display.The load IED number,gateway num- The LAN-based LSC design has been successfully imple- ber,IP address,and load value are listed.The priority mented in an oil refinery facility power plant. list is downloaded from the main SCADA server and 42 IEEE Computer Applications in Powernetwork might be critical for the system control deci￾sion-making. Monitoring the operating status of the whole network and reporting the network communica￾tion failure becomes an essential function. In the LSC design, the simple network management protocol (SNMP) is employed to monitor the LAN communication status. Network management of the LAN consists of network management stations (man￾agers) communicating with network elements (IEDs). The software in the network element that runs the management software is called an agent. The manager can ask the agent for a particular value, or the agent can report to the manager that something important happened (e.g., an IED has failed); through this two￾way communication, the status of all LAN communica￾tion can be monitored. When a network component is down, an error or warning message is sent to the con￾trol center immediately to avoid system malfunction. Database Operation A local database is used by the LSC to store power plant equipment parameters as well as historical event data. When the LSC starts, power plant information (including IED name, DIU IP address, data communication telegram, mask, etc.) is transmitted from the SCADA server to the LSC database. Different load-shedding priority lists and the current active list is stored in the LSC database as well. In case communication with SCADA server is lost, the LSC will shed loads according to the information in the database. During operation, important messages (such as system alarms, communication abnormal, load￾shedding events) will be stored for future historical data retrieval. Open database connectivity (ODBC) is used as a bridge between the LSC and the local database. Implementation Experience The LAN-based LSC design has been successfully imple￾mented in an oil refinery facility power plant. The refinery facility power plant is an isolated power plant with four GTGs. Each GTG’s full load is around 40 MW. The actual output and rated output are determined by online monitoring of out-going CB status, output, and ambient air temperature. Normal operation condition is such that there is always one generator serving as spinning reserve. About 44 loads at 33/6.6 kV in 16 substations can be controlled by the LSC. Their CB statuses are reported to the LSC by exception reporting. The CB status is then registered by the LSC. Subsequent load-shedding logic will exclude those CBs that are currently in an open position. DIUs send a life-sign signal to the LSC at a preset interval (normally 10 s). This signal is used to moni￾tor the health of the communication link. If more than 6 life-signs are missing, the LSC will treat this connection as “down.” Load-shedding logic also excludes those CBs that indicate a failed communica￾tion link. When communication is reestablished, a general request will be sent to DIUs to request update for all relat￾ed CB status. The same applies to all GTG parameters. LSC Configuration The LSC application is running on a industrial PC with dual power supply and dual NIC. The operating system is Windows NT. SQL Server is used as the backend sup￾porting database. The application on the LSC PC is com￾piled using C++. The SCADA server is running on Unix Solaris with Siemens Spectrum SCADA software. LSC PMI The LSC person-machine interface (PMI) consists of dis￾plays that give the operator a current system situation overview as required for load shedding. It enables inter￾action by input of selected parameters, such as priority numbers, deactivation of sequences. Device parameters are stored in the LSC local data￾base. New devices (such as GTG, load, feeder) can be dynamically added or deleted through the IED data￾base management display shown in Figure 5. The data contains loads and generations, IED number, associat￾ed gateway number, load value, telegram number, and mask for the signal control. System parameters are also set up in this display. Using this screen, opera￾tors can manually set and change and IED parameters. LSC parameters (such as the life-sign checking inter￾val, overload response time, and overload scan inter￾val) are also configured in this display. LAN connection parameters can also be modified for differ￾ent systems. Figure 6 shows the main load-shedding active pri￾ority list display. The load IED number, gateway num￾ber, IP address, and load value are listed. The priority list is downloaded from the main SCADA server and Figure 5. LSC IED database 42 IEEE Computer Applications in Power