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Remote Alarming for Power Grids
Interior view of remote alarming system BSC50.
By Stew Thompson, CAS DataLoggers, Inc., Chesterland, OH
An electrical utility company needed to send alarms from remote stations in the event that the local power grid went down, and in other special cases including operational faults and security breaches. The entire time a substation was off the grid, an area was without power, so an advanced warning system for ground fault events was critical. CAS DataLoggers provided the datalogging solution. Management saw the need for a remote alarming system with SMS alarm messaging to warn personnel in case of a fault event and which would also send data to activate LEDs on a mimic to pinpoint the exact spot at which the power failure occurred. This system also needed to be cost-effective and have a long battery life for years of worry-free operation.
The utility company installed 200 Infinite BSC-50 Remote Alarming Systems in the immediate vicinity of its power substations, connecting these dataloggers with an Infinite SCOM-100 GSM/GPRS controller to receive their data and alarm messages. The BSC-50 devices were ideal for supervising substation operational status, featuring 4 user-configurable digital inputs to identify the binary status of operations/faults in the form of Push/Pull or 0-1 and 1-0 transition. An optional version was available with 2 digital inputs along with 2 analog inputs to measure and alarm on threshold and limit breach and an excitation output for powering external transducers.
Low Power Microcontroller
An ultra low power microcontroller enables alarm condition detection, subsystem power switching and overall system control. Both versions provide quad-band GSM network compatibility and a serial port for PC connection. Each logger has an uninterruptible power supply from one or more built-in lithium thionyl power cells providing more than 10 years of operation. The devices can operate on normal power and in the event of a power loss, they can be powered from the battery completely.
Infinite SCom-100 GSM/GPRS Controller exterior.
The user-friendly SCOM-100 DIN rail-mounted controller provides the power station with alarming and remote control using SMS. The main unit incorporates a quad band (850/900/1800/1900MHz) GSM/GPRS modem, 2 analog inputs, 4 digital inputs, 4 power relay outputs and a serial RS-232 port. Front panel LED indicators monitor control and digital I/O states, and a variety of I/O expansion units (digital and analog I/O) can be cascaded on the serial I/O expansion bus if needed. The device has several operation modes, including emergency stop, and low power operation. All setup and control functions have been simplified by using a mobile phone; personnel simply insert a SIM card with a name and phone number in the phone list and press the start up button as the controller powers on. Simple ASCII configuration commands handle unit setup and control, and several commands can be packed in one SMS. In addition, the controller's RS-232 interface can be used to both set up and test the unit using a PC or an ASCII terminal.
Configuring Alarm Parameters
The rich command set contains commands for configuring input alarm parameters, setup of irrigation and time scheduled programs, control functions like on/off and PID control, defining user groups, and controlling system outputs with time-related parameters. The unit includes free bundled SCOM Configurator PC software for convenient setup and commissioning complete with easily upgradeable firmware. An OPC driver is also available for connecting the SCOM-100 controller to common SCADA systems in a wide variety of industries and applications. Again, a few SMS ASCII commands are all that are needed for quick, convenient setup and control of the GPRS functionality. The OPC server can support several distributed SCOM-100 units, limited only by the total I/O number. All SMS functionality remains intact during GPRS operation.
Fault Detection Relay
At each substation, a special fault detection relay is installed that detects earth ground faults and provides a plain contact as an alarm in the case of a fault. The BSC-50 GSM/GPRS dataloggers monitor these faults and limits breaches and then transmit respective coded messages via SMS to a control center. The BSC-50s were also programmed to transmit "I am alive" messages at regular schedules to the control center to relay their operational status, with a maximum of 20 users/recipients.
When an earth ground fault is detected in a substation, that substation is then automatically taken offline, and manual or remote operations are then needed to place the substation back on the grid. If the fault persists, then the substation's local automation ensures that the station is not placed back on the grid.
At the control center, a PC is installed to run the monitoring software that logs, monitors and reports the operational status of the remote alarming dataloggers. The PC runs Windows
XP Pro executing WA Manager software, and is also connected to a GSM modem. Also in the control center, a mimic diagram showing the geographic location of the substations and their BSC-50 devices is installed, with built in red-colored LEDs at each substation. These LEDs are cabled to the M2M (machine to machine) SCOM100 alarm receiver device, connecting to the controller's digital outputs. When an alarm occurs at a BSC-50, two messages are immediately sent: one to the control center monitoring station running WA Manager, and one to the receiver device to switch on an LED at the mimic diagram. As soon as the fault is rectified, the LED can be switched off by flipping a switch on the base mimic diagram.
The utility company benefited immediately from installing the Infinite BSC-50 remote alarming system to monitor ground current at its power substations. The SCOM controller received SMS from the remote dataloggers and lit the LED lamps on a mimic diagram so that users at the control center could now both visualize the location of the faults and see the sequence of failing substations in order to perform remote operations if possible or to order a maintenance crew to visit a specific point on the grid to reroute power and maintain power in the areas which had been taken off the grid. The system is very cost-effective, with one product handling all the remote monitoring and sending the data back to the SCOM receiver and the control room mimic.
Estimated time reduction in identifying and rectifying problems on the grid is very high. The only procedure used previously was to send a maintenance crew to visit the substations and see which station's outdoor lamp was off and report back to the control center. Then operations to reroute power had to be made on a time-intensive trial-and-error basis. Using the new remote alarming system, management can instantly see the LEDs on the mimic and know just where to send the crew, which keeps the time substations are off the grid to a minimum by improving problem detection and response times.
Contact: CAS DataLoggers, Inc., 12628 Chillicothe Road, Chesterland, Ohio 44026
800-956-4437 or 440-729-2570 E-mail: firstname.lastname@example.org Web:
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