Generator Condition Monitor for Air-Cooled Apparatus (GCM-A)

Generator hotspots can cause catastrophic failure

E/One Generator Condition Monitor for early detection and warning of overheating in air-cooled apparatus

Corrective action prompted by early warning of air-cooled generator overheating can mean the difference between a brief generator shutdown for minor repairs and a major overhaul involving weeks, or even months, of costly down-time.
 
Advancements in air-cooled generator designs have resulted in increasingly higher power ratings. The higher power densities place significantly greater stresses on materials and structures, making slight decreases in cooling efficiencies much more critical. Probability of overheating in these air-cooled machines becomes greater as designs are pushed closer to their critical limits.

Early Detection of Overheating — Beyond RTD's and Thermocouples

High concentrations of submicrometer particles (pyrolysis products) are released whenever any material within a generator is heated sufficiently to create thermal decomposition. These “hotspots” can lead to catastrophic failure if not caught in time. The GCM-A provides the warning time needed to react to these potentially devastating events.

The GCM-A warns of an impending failure much faster than RTD's or thermocouples. Why? Because RTD's and thermocouples need to be physically near the hotspot, or wait until overheating progresses to the point that the temperature near the RTD or thermocouple rises sufficiently for the sensor to detect it. This results in a significantly larger "fault," possibly a catastrophic one. The GCM-A detects the pyrolysis particles emitted into the cooling air as a result of overheating, arcing or vibration virtually anywhere in the generator.

How the Generator Condition Monitor Works

The GCM-A monitors two air sample lines using a submicrometer particle detector. One line monitors ambient air, which serves as a reference. The other line monitors generator cooling air, which is then compared against the particle level of the reference. High particle levels in the generator cooling air, without a corresponding increase in the ambient air, confirms the source of the pyrolysis particles is from within the generator.
 
Each sample line is monitored by the particle detector sequentially every 15 seconds using an electronically controlled selector valve. The detector operates at a cycling rate of once per second, and provides a continuous analog voltage corresponding to particle concentrations.
 
If overheating occurs, large numbers of pyrolysis products are created in the generator cooling air, and creating thermal decomposition and generator "hotspots." When the signal level corresponding to the difference between the generator cooling air and ambient air exceeds a predetermined (adjustable) set point, the result is a differential alarm, causing the alarm contacts to close. Individual contacts will also close if the outputs corresponding to the ambient air and/or generator cooling air exceed predetermined (adjustable) set points.

GCM-A Features and Benefits

• Continuous real time monitoring of overheating and arcing
• Continuous self-checking diagnostics, microprocessor-controlled
• Serial computer interface
• LCD Display - status indicator during normal operating mode; provides diagnostic and programming prompts when needed
• Bar Graphs - one provides continuous, real-time indication of ambient signal, while the second one provides real-time indication of generator signal
• Data retention provides average hourly readings that can be downloaded
• Alarm points and system sensitivity are adjustable
• Optional partial discharge monitoring
• Flexible system design tailored to individual situations
• GEN-NET - remote monitoring and control software

Generator Condition Monitor Specifications