【Electrical Fire Monitoring Series】PMC-T411 Fault Arc Detector Introduction

[Typical characteristics of fault arcs]

• The arc current is temporarily extinguished almost every time before the zero point, and then it will re-ignite, so that there is a "zero rest" phenomenon in every half cycle, that is, "flat shoulder";
• The rising rate of arc current is generally higher than that of normal current, and the current has a sudden change every half cycle, and the sudden change is random;
• Both voltage and current waveforms contain high-frequency noise;
• When arcing occurs, the line voltage drops sharply, and the waveform is close to a rectangle;

Arcs usually occur in sporadic, intermittent periods of normal current. For series arcs, due to the voltage drop across the arc, the loop current with arc is usually smaller than without arcing, and abnormal waveforms may occur. Since the series arc current is affected by the load, the arc current varies greatly under different loads, and even if the same load is in the same state, the arc current will vary with different times. So, when it comes to describing the universal nature, it refers to the waveform over any period of time. Figure 2-4 and Figure 2-5 show the series arc current waveforms for a purely resistive load and a computer load, respectively.

Electrical fires caused by short circuits, overloads, overvoltages, leakage, overtemperatures, etc., can be prevented and protected by fuses, circuit breakers, electrical fire monitoring detectors with residual current and temperature.

However, there are still some electrical faults at the end of the line that have not been detected in time, such as line aging, insulation damage, loose electrical connection, poor contact, etc., these abnormal conditions produce fault arcs, ignition phenomenon, will continue to produce high temperatures of more than 3000 degrees, and accompanied by metal melt splashing, when there are combustibles around, it is easy to cause fire.

Therefore, it is very important to monitor and warn the fault arc of the terminal electrical circuit due to various abnormal conditions.

Common fault arcs are:

• Human operation error, resulting in the rupture of the insulating skin and the potential danger of arc;
• The cable is bent and clamped, resulting in the rupture of the insulating skin and the potential danger of arc;
• Connectors and cables are kinked and fractured, causing arc failures;
• Poor terminal contact, resulting in arc hazards;

Common causes of faulty arcs:

• Poor insulation
• Poor contact
• The wiring harness is broken
• Aging of wires

【Product Introduction】

CET independently developed PMC-T411 fault arc detector, which is used in lighting circuits and installed in terminal distribution boxes, which can detect fault arcs in the line at an early stage, monitor and warn fire hazards such as loose connection, poor insulation, poor contact, aging and damage of electrical lines, and provide preventive protection for fires caused by fault arcs.

【Product Features】

• Real-time monitoring and alarming

Real-time monitoring and alarm of fault arc supports line overvoltage, undervoltage, overload, leakage, and over-temperature monitoring and alarm functions;

• In-place operation display

LCD screen display, support local sound and light alarm, silencing and reset;

• Fault arc simulation function

It can simulate the occurrence of fault arcing, and can be tested in this machine;

• Communication features

Support RS-485/two-bus communication, optional wireless NB-loT and 4G communication mode;

• Data maintenance statistics

The number of arc, overvoltage, overload, leakage and over-temperature alarms can be counted, and the alarm threshold and delay time can be set;

【FAQs and Precautions】

1. Where is the fault arc detector installed?

The fault arc detector is suitable for the installation of electrical circuits of 10kV and below in industrial and civil buildings, mainly used in lighting circuits, and installed in the terminal lighting distribution box.

Main application occasions:

(1) Lighting and socket circuits for cultural relics buildings and new timber buildings;

(2) Lighting circuit in a space place with a height greater than 12m;

(3) Rental and sales shopping malls, wholesale markets, and home appliance shopping malls end distribution boxes;

(4) The terminal distribution box of the convention and exhibition center, subway station and warehouse;

(5) Terminal distribution boxes for elderly care facilities and collective dormitories.

2. What are the main national standards for fault arc detectors?

(1) GB 50116-2013 Code for the Design of Automatic Fire Alarm System, which requires: the electrical fire monitoring detector with the function of detecting the fault arc should be set up on the lighting line, and only the electrical fire detector with the function of detecting the fault arc can ensure the effective detection of the fire caused by the fault of the lighting line.

(2) "GB 51348-2019 Standard for Electrical Design of Civil Buildings", which requires: fault arc detectors should be set up at the end of distribution boxes in stall-type home appliance shopping malls and agricultural wholesale markets.

3. What is the length of the fault arc detector protection line?

The fault arc detector is installed at the lower end of the switch and is connected in series in the line. The length of the protection line should not be greater than 100m.

【Conclusion】

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