Motors are often the most production-valuable assets at any site. Partial discharge (PD) degradation, caused by anything from void or delamination in the ground wall insulation to contamination or inadequate stress control, can contribute significantly to machine failure – and costly downtime. The unexpected failure of a production-critical motor usually incurs higher repair costs than the capital replacement and/or repair cost of MV/HV assets in an electrical network.
First developed for motors located in Ex/ATEX-rated hazardous zones, Monitra’s remote monitoring technique is a cost-effective solution for motor condition monitoring. Our Kronos Monitors can cover up to six motor circuits each, utilising PD sensors installed at the central switchgear – this not only monitors the condition of your critical motors, but also the associated power cables and switchgear panels.
Monitra’s split-core HFCT Sensors can either be installed around the cable phases with double earth loop or around the earth strap. They accurately measure the high frequency current signals of PD pulses occurring in the conductor of the associated MV/HV cable/plant without need for a direct galvanic connection to the HV conductor. It works by converting PD currents flowing in the earth connections of the motor to voltage output signals to the Kronos Monitor. For DOL-fed motors where an at-asset solution is more suitable, HVCC Sensors are galvanically connected to the motor terminal box, with cabling from the sensors being terminated from a Point of Attachment (POA) box. HVCCs detect current impulses from PD sites within the stator winding insulation which propagate from the motor's interior towards the sensors.
As well as DOL-fed motors, Monitra's Kronos units are able to monitor PD in motors driven by variable speed drives (VSDs). VSD-driven motors generate switching pulses when in operation that can appear very similar to PD pulses.
With our at-machine solution, we utilise a combination of HFCT sensors and our SMART-TB3™ sensor installed at both the VSD-end and motor-end of the asset being monitored. The SMART-TB3™ sensor has both a low frequency and high frequency output, which allows the simultaneous detection of high frequency PD signals and the VSD motor’s line frequency. This enables the Kronos Monitor to distinguish the noise from the VSD and genuine PD signals.
Our Kronos Monitors can be installed alongside Monitra PD sensors, or attached to pre-installed sensors, and is suitable for SCADA integration using MODBUS protocols. When utilised with our Atlas by Monitra™ interface, our complete network monitoring solution enables our customers to gather data-driven insights and our expert recommendations to keep their critical machines up and running whilst keeping maintenance costs down.
For further information, click here.
Alongside our Atlas by Monitra™ interface, our Kronos Ultimate Software provides effective denoising of PD readings, providing more enhanced measurements and reducing false alarms with our ML-42 machine learning algorithm.
Here, you can see an example of PD data captured from a motor being monitored both before and after the readings had been denoised. By removing the noise, slot discharge within the stator of the motor was detected.
To find out more about the capabilities of our software, click here.
If you have a requirement for the monitoring of your critical motors, please fill in our contact form below. You can also find out more about our work in the field by reading our case studies, which you can find here.