The function of emergency alarm systems is to produce an alarm in the event of danger and to remain passive when there is none. The malfunction of these systems, either no alarm sounding if there is danger, or an alarm sounding unnecessarily, is not just a nuisance; it can also be dangerous and can result in expensive call-out fees.
False alarms have the following consequences:
• Personnel start ignoring the alarm messages.
• Emergency staff is unnecessarily called out.
• The triggering of fire extinguishing systems can cause interruption of operations.
All these factors cause unnecessary costs and can be prevented if possible causes of false alarms are recognised at an early design stage and are eliminated by taking suitable preventive measures. Lightning strikes are one such cause, and given the profusion of summer storms in South Africa, this is a real threat.
Coordinated lightning and surge protection prevents false alarms and increases the availability of the systems.
Many of today’s emergency alarm systems have an increased immunity to transients on the primary lines, secondary lines and mains voltage cables according to IEC 61000-4-5. Nevertheless, only external and internal lightning protection measures provide comprehensive protection against damage resulting from lightning strikes and surges.
Monitoring principles
Different monitoring principles are used for emergency alarm systems:
Pulse polling technology:
• Information from the sensor which has triggered the alarm is digitally transmitted. This allows the identification of the sensor and its exact location.
• DC circuit technology: According to the closed circuit principle, every alarm line is permanently monitored. If a sensor in a line is triggered, the line is interrupted and an alarm is produced in the alarm panel. However, only the alarm line, but not the individual sensor can be identified.
Irrespective of the monitoring principle used, all cables extending between the different areas of the emergency alarm system must be integrated in the lightning and surge protection concept of the overall system.
Recommended protection
Dehn’s Blitzductor XT, type BXT ML2 BE, must be installed to protect two-wire alarm lines and connect the earth drain wire by means of an EMC spring terminal. For cables with more than two wires, a four-wire version, BXT ML4 BE, is available. Surge protective devices are selected according to the voltage of the alarm lines, which is typically between 12 and 48 V. The low internal resistance is also a clear advantage of arresters since the maximum resistances of the alarm lines must not be exceeded. For the outputs of the alarm panels (acoustic and visual) it must be ensured that the nominal current of the surge protective devices is not exceeded.
Read more...Why utilities must prioritise maintenance of SA’s remote data Schneider Electric South Africa
Electrical Power & Protection
The story of power generation is more than meets the eye. Beyond energy distribution and the infrastructure are invisible, point of presence data centres located the remotest parts of our country that play a fundamental role in keeping systems running
Read more...The house that revolutionises substations WEG Africa
Electrical Power & Protection
Traditional substations have major drawbacks in terms of their construction and resilience. One solution is the E-house, a prefabricated, customised and transportable steel structure designed to house a range of electrical and automation equipment.
Read more...Localised inverter-integrated transformer
Electrical Power & Protection
ACTOM, South Africa’s largest manufacturer, repairer and distributor of electromechanical equipment, is launching a breakthrough in renewable energy integration with its localised inverter-integrated transform
Read more...ABB innovation for energy efficiency and sustainability
Electrical Power & Protection
The application of sensor technology to reduce the operational and standby power losses of traditional current and voltage transformers can lead to energy savings of 181 MWh over a 30-year period, the lifetime of a typical switchboard in the African environment.
Read more...UPS systems are key to keeping SA’s automotive industry up and running Schneider Electric South Africa
Electrical Power & Protection
During loadshedding, PLCs and OT systems often fail, not because they are directly tied to the factory’s core manufacturing process, but because they are now an integral part of IT infrastructure. When an IT system shuts down, the impact is far more complex than simply restarting machinery.
Read more...ACTOM advances energy infrastructure
Electrical Power & Protection
At this critical juncture where South Africa is poised to modernise its power infrastructure, ACTOM’s Engineering Projects and Contracts (EPC) Division showcased its capabilities for the first time at Enlit Africa 2025.
Read more...Advanced contactor solution to revolutionise motor management Schneider Electric South Africa
Electrical Power & Protection
Schneider Electric South Africa has launched the TeSys Deca Advanced, an advanced contactor solution designed to revolutionise motor management with unparalleled efficiency, reliability, simplicity and sustainability.
Read more...Steaming ahead with boiler skills development
Electrical Power & Protection
As an expert in steam and boiler operations and maintenance, AES is very focused on safety, quality, technology advancement and the development of human capital. The company invests heavily in training and the promotion of talented people on an equal opportunity basis into the industrial operations environment.
While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.