PRE-FIRE ALARM SYSTEM

Introduce the composition principle of the electrical fire monitoring system, share the design concept and specifications in monitor application. Here introduces the residual current electrical fire monitoring system in super factory, you can know more about function of this system and its advantage.

The Super Factory project has a total of 340pcs ESSL902 residual current fire detectors, installed in plant power distribution room. The L902 residual fire detector is connected to the ESS9000-A electrical fire monitoring host. to the fire control center by Comm-Bus. This system integrates in iron enclosure, wall mount design, convenient for installation, transportation and maintenance.

System Topology

Electrical fire monitoring system includes three basic components:

Site monitoring host;

Residual current sensor;

Temperature sensor.

Residual current electrical fire monitoring system adopts a hierarchical distributed structure， it’s composed of a station control management layer, network communication layer and field equipment layer.

The electrical fire monitoring detectors are connected to the wall-mounted host through the shielded twisted pair RS485 cable (MODBUS communication protocol).

1) Station control management

This level is aimed at dispatcher consists of monitor software and necessary hardware to provide human-computer interface. Monitoring software can process all kinds of on-site data in real time, and reflect on-site operation conditions to the dispatcher.

Monitoring host: Data collection, processing and data forwarding. Provide data interfaces support for system management, maintenance and analysis.

UPS: Ensure power supply for all system, avoid system disconnect when power off.

2) Network communication layer

System mainly adopts shielded twisted-pair cable, real-time communication between field equipment and host with RS485 interface and MODBUS protocol.

3) Field equipment

The field equipment layer is the data acquisition terminal, mainly use ESSL902-A/B residual electrical fire monitoring detector.

ESSL902 detector designed for TT and TN systems below 0.4kV. It monitors and manages the residual current, wire temperature, overcurrent, overvoltage and other important parameter related fire risk in distribution circuit, to prevent the occurrence of electrical fire.

ESSL902 detector is responsible for the basic data collection, distributed I/O controller connected with the field bus terminal, which can upload the detected data in real-time.

System feature and working principle The use of residual current monitoring is a pre-fire alarm system, main advantage is to “avoid” losses, while the traditional general fire automatic alarm system is to “reduce” losses. Therefore, no matter whether it is a new construction or reconstruction project, whether or not a general fire automatic alarm system is installed at the scene, it is still recommended to install an electrical fire monitoring system. The system measures the two key physical parameter: Residual current and Temperature. Let’s take an example via TN-S system. A/B/C/N wiring through residual current transformer, when there is no leakage in the system, the vector sum of the current flowing into and out of the CT is zero, CT secondary side current is also 0; when earth leakage occurs, the vector sum of the current flowing into – out CT is equal to the current flowing away from the earth, that is leakage current. Temperature sensor generally uses Pt100. It can achieve stable temperature measurement and a large range, in system for monitoring cable temperature and ambient temperature. If the two monitored physical parameter exceed the preset value, an audible and visual alarm signal will be issued and sent to the background electrical fire monitoring equipment.