A Power-Line-Based Sensor Network for Proactive Electrical Fire Precaution and Early Discovery? for seminar.?

Fire alarm systems are often wired in a special high temperature wire called pyrotenax (mineral insulated cable). This is a copper sheath, and inner copper conductor and a mineral powder insulator between, so can operate up to about 1000C. This is required by regulation in some installations. You need to make the distinction between say a hotel, workplace, factory, hazardous location, domestic or residential. PVC insulated power cable operates up to maybe 120C before the insulation melts. This needs to be understood first. It would make more sense to use wireless communication, so long as regular automatic checks occurred. The same applies to electrical cable, if there is regular checking a sudden loss of signal could indicate a loss of insulation, so this in itself could represent a sensor of some sort. I would think to be effective the checking would have to be continuous as fires can be hazardous within a short time like one minute. It seems likely that any zone location information will be lost if the insulation fails before an alarm from other sensors, which is entirely possible. If there is an alarm this needs to be remembered, as users might well think that it was a communications failure, with no alarm. It has to be recognised that a communications failure is a possible high energy fire. The first link below might help a little, remembering it applies to residential accommodation. I guess you will not find such systems in use, but you could make one up. Some sensors are able to communicate using RS485 by wire which means they can share the same pair of wires. This is similar to RS232. These could be connected to an AC power line modem of some type. Nowadays power line networks (LAN) are usually for ethernet connections, so there is a need for an serial to ethernet adaptor, but maybe a design including a simple power line modem incorporated into the sensor would work. The second and third links lead to ideas for the power line modem. The third link shows the X10 system for home automation, though this has defined zones, the speed may be too slow for larger installations. Read the weak points and limitations topic, as there are many issues with such devices, and appliances that could attenuate signals etc. Personally I think the potential for PLC systems causing interference is high - meaning spectrum pollution - so they are not the best way to do anything. Just because HF radio is mainly obsolete is no argument to allow wide spread pollution of the HF radio spectrum. It still has important uses. Also reliability and incoming interference can be an issue. Best to look for wired (expensive) or wireless (radio) fire alarms.