Is short circuit the cause of fires in Hospitals and buildings?
Unbalance plus triplen Harmonics (3rd, 9th, 15th ..) cause huge power loss and is Potentially a fire Hazard.
We have several news reports of fire in hospitals causing deaths and destruction of properties during the covid pandemic. Most of these fires have been nonchalantly dismissed as short circuits. But the facts can be different, aided by lack of awareness of Power quality.
Load Imbalance due to single phase non Linear loads like UPS, computers, Power supplies , medical devices, Solid state lighting and its controls, Inverter airconditioners, drives and expensive medical devices like scanners, Xray machines, ventilators and other life saving devices. These equipments most with power supplies all these put together becomes a Potential fire hazard. They also cause enormous Power losses, and damage equipments due to poor power quality.
These load imbalances added to the harmonic components (with 3rd harmonic being the dominant)is major factor of power losses, and are causes of inefficiencies and disruption to critical operations (Some of which are life saving)
If an ideal electrical system that?is perfectly balanced and is devoid of 3rd Harmonics the current in each Phase have the same magnitude and vectorally cancel out at the neutral, and hence no current flows to the neutral wire.
But however in realty they do not normally exist, when the system load per phase are different, and neutral current flows depending on the level of imbalance and presence of 3rd Harmonics, the neutral current can increase upt 1.7 times the Phase currents, necessitating a double neutral to prevent neutral burn outs.
The Power losses in each line are proportional to the square of the current, for the same total load power. Low losses occur when the current magnitude are the same in all the phases, besides in the case of a unbalance system, there is the other single Phase Harmonic loads that aggravate the problem of high neutral currents all with the unbalanced portion of residual currents flowing to the neutral. Consequently the neutral currents gets overloaded causing a burnout of neutral currents, and also snapping of neutral wire, causing high voltages above 350 V. These high voltage will damage all the expensive devices connected to the electrical system. It can also cause a flashover and consequently cause fire.
The single phase loads with Harmonics dominated by the 3rd, 5th and 7th, with the 3rd being the most dangerous and Harmful especially to digital equipments at home, hospitals and offices.
Some of the Harmonic loads are as follows:
1.????UPS
2.????Computers
3.????Inverter Airconditioners
4.????Led Lighting
5.????Medical devices like ventilators, patient monitors, CT scanners etc..
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6.????Lifts
7.????Refrigerators
8.????Induction stove
9.????Washing Machines
10. Chargers Includes EV chargers.
All these loads contribute to harmonics immensely.
These loads also cause high earth leakage currents which could damage sensitive digital equipments. Medical devices like scanners can be very sensitive to leakage currents. It can also elevate the neutral earth voltage beyond the safe voltage limit of 3 volts this can cause erroneous data in medical devices and computers.
If you ask if the short circuit cause for fire, the answer will be no, as the electrical circuits are protected by MCB and MCCB. It is invariably the heating caused by Harmonic Loads and high neutral current that can cause fire due to the phenomena of skin effect.
Now how do we prevent these fires?
A simple WAVEFORMS Triplen Elimintor will divert and cancel the Zero sequence currents (current s that flow in the neutral) and also balance the currents, making the electrical system safe, resilient, reliable and efficient.
some of the fire accident in hospitals in recent years;
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WAVEFORMS
Self Employed at Rash Electrical
2 年Most of the time Fire is Caused by Earth Leakage/Earth Fault in any distribution system
Energy Efficiency & Power Quality Professional
2 年In fact all fires will be due to short circuit, but the issue is all investigations stops at short circuit. Hardly anyone goes beyond it to investigate the cause of short circuit and one of the major reason would be still utilizing 3.5 core or half neutral conductor ( Which standard supports this?) where as it has to a minimum of 4 core, full neutral or 5 core, double neutral in non-linear loads like hospitals.
Director, Om Technical Solutions
2 年Sometimes yes I believe as we have few cases in India for fire due to short circuit in Buildings and Hospitals. If you have any other views then pl. share and advise.