April, 2012
www.us-tech.com Remote Alarming for Power Grids By Stew Thompson, CAS DataLoggers, Inc., Chesterland, OH
that the local power grid went down, and in other special cases including operational faults and security breach- es. The entire time a substation was off the grid, an area was without power, so an advanced warning sys- tem for ground fault events was criti-
A
n electrical utility company needed to send alarms from remote stations in the event
variety of I/O expansion units (digi- tal and analog I/O) can be cascaded on the serial I/O expansion bus if needed. The device has several oper- ation 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 com- mands handle unit setup and control,
and several commands can be packed in one SMS. In addition, the con- troller’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, con- trol functions like on/off and PID con- trol, defining user groups, and con- trolling system outputs with time-
related parameters. The unit includes free bundled SCOM Con - figurator PC software for convenient setup and commissioning complete with easily upgradeable firmware. An OPC driver is also available for con- necting 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, con- venient setup and control of the GPRS functionality. The OPC server can
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Page 55
Interior view of remote alarming system BSC50.
cal. 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 fail- ure 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 Alar - ming Systems in the immediate vicinity of its power substations, con- necting these dataloggers with an Infinite SCOM-100 GSM/GPRS con- troller to receive their data and alarm messages. The BSC-50 devices were ideal for supervising substation operational status, fea- turing 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 exter- nal transducers.
Low Power Microcontroller An ultra low power microcon-
troller enables alarm condition detection, subsystem power switch- ing 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. The user-friendly SCOM-100
DIN rail-mounted controller pro- vides the power station with alarm- ing 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 con- trol and digital I/O states, and a
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