Can Phase Loss Cause A Building Fire?

One of most dangerous situations in power distribution can be the loss of a phase in a 3 Phase Power network, known as "Single Phasing".

This can be caused by a failed conductor, lightning, a transformer winding opening up, or even a mechanical switching event.

An induction load dropping a phase can experience longer term initial starting current to 600% as it attempts to start and continues to stall, the winding insulation can begin to melt from the heat and short out.

Any existing motors may still be running but with an increase in current on each of the existing operational phases. Reduction in torque capacity of these running motors can be inherent when exposed to a variable mechanical load which could bog them down to the point of stall.

Although overload protection devices can instigate shutdown for protection of the equipment and life safety, any weaknesses in the network due to age or faulty design will be detrimental.

Active monitoring of phase conditions, provides a proactive fire safety mechanism for infrastructure and occupants alike.

Understanding Phase Monitoring

Phase monitoring, (aka.. phase sequence or phase loss monitoring), is part of the electrical network management of modern building power systems.

The Basic Idea

Phase monitoring is the active observing the phase patterns in a three-phase electrical distribution system. The service provider monitors their own system to the point of site termination (often a MV/LV pad mount transformer), where it is up to the owner's equipment to monitor the electrical phases, ensuring a balanced load and consistent power integrity to the building systems.

Phase monitoring ensures that these phases are:

• Sequenced Properly: The phase order should remain consistent. A phase reversal can cause motors to run in reverse, leading to dangerous situations and equipment damage.
• Balanced Phases: The voltage across all three phases should be equal. Any significant imbalances, outside of normal conditions, can lead to inefficiencies and strain on the electrical equipment.
• Continuously Available: The removal of one or more phases, can cause equipment performance issues and premature failure.

Why Do It Anyway?

Phase monitoring safeguards against the potential risks associated with unexpected phase aberrations.

Phase aberrations monitored can include:

• Equipment Protection: Phase imbalances or phase drops can cause over heating in motors and transformers, resulting in premature life expectancy.
• Operational Continuity: Phase anomalies can lead to unscheduled shutdowns in production operational capacity, causing financial losses.
• Human Safety: Incorrect phase sequencing or phase loss can be a serious safety hazard, with risk of electrically related fires or mechanical incidences affecting both other equipment and operators (occupants).

Initiating Phase Monitoring

What Makes A Monitoring Systems?

• Sensors: These detect the voltage levels in each phase and provide real-time data.

• Control Unit/Relay: Interprets sensor information and triggers alarms or shuts down equipment if aberrations are detected, preventing damage.
• Interface (Remote/ local HMI): Systems often include an interface for users to monitor phase conditions, set thresholds, and configure responses to various aberrations.

Detected Issues

• Phase Loss: When one or more phases un-expectantly stops, due to external supply power grids or internal site distribution system failures. Phase loss can lead to inconsistent motor speeds, increased mechanical stress, and loss of torque capacity.
• Phase Imbalance: When the voltage in one or more phases differs significantly from the other phases. Causes can range from unsymmetrical loading to wiring or equipment issues.
• Phase Reversal: When the phase sequence is changed, potentially due to improper installation or maintenance wiring. Phase reversal can cause motors to run in reverse, risking major mechanical damage.

Improving For The Future

Cutting edge systems are pushing technology, with elements of AI and IoT connectivity to analyze phase conditions, predict potential issues, and make calculated maintenance procedures before system concerns escalate.

The progress toward more automated and interconnected infrastructure increases the importance of phase monitoring systems, will only increase it's presence.

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