Introduction to Qualitrol’s Travelling Wave Fault Locator
When and Why to Monitor Partial Discharge
Successful Deployment of Qualitrol’s Dissolved Gas Analysis Monitor LT1
Qualitrol have recently deployed a suite of their latest low-cost wireless Dissolved Gas Analysis Monitor LT1 on the transformers at a utility scale solar farm in a southern US state.
Consisting of nine of our latest generation LT1 DGA sensors we are monitoring dissolved hydrogen, moisture and oil temperature on nine individual transformers spread throughout a 600-acre solar farm. These sensors provide invaluable information on the health of every transformer on the site. Each sensor transmits encrypted measurement data to a nearby Gateway device which then transmits that encrypted data over the 3G cellular network to secure cloud storage. The transformer owner is accessing the data by logging in to our QualConnex analytics platform.
What makes this installation unique and in a first for the industry, all of this has been done completely wirelessly! Installation of each sensor takes approximately 45 minutes meaning all 9 transformers could be monitored by the end of a single day of installation work.
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Figure 1 : This large solar fam as seen from above and as mapped and represented on the QualConnex platforms. Exact locations of DGA sensors can be defined. Traffic Light Colouring allows for immediate identification of transformer in alarm condition. In the case of this far all the transformers are healthy right now and all the sensors are reporting live data!
LT1 is a tri-part product
- An LT1 sensor, mounted on the drain valve of the transformer
- A Gateway to configure and communicate with the sensor and the cloud
- QualConnex, a platform to configure everything wirelessly and track your transformer health
LT1 is the first truly wireless online DGA monitor. Utilizing a high accuracy low power hydrogen and moisture sensors the LT1 is mounted directly onto the drain valve of the transformer where it samples the oil 4 times per day and report that date via an encrypted signal utilizing LoRa (Long Range) communications technique, which is a license free sub -Gigahertz radio frequency band. Because it occupies the access point to the oil the LT1 incorporates its own oil sampling valve so the user still has the ability to draw oil samples for laboratory analysis. Utilizing encapsulated batteries the sensor can operate for 5+ years on a single set of batteries such is the minute power consumption requirement it has been designed with.
QGateway continues the wireless feature of the product. A solar charged, battery powered gateway, this device listens for signals from any number of LT1 devices using a LoRa antenna and transmits that data to the cloud for access withing the secure area of the QualConnex website. In this site there are 4 gateways but in a more compact site such a substation, a single gateway could be used for all 9 sensors.
QualConnex is the user’s interface with the hardware. Sensor and gateway position for mapping purposes, Transformer nameplate data storage, alarming configuration are among just some of the features of the software. QualConnex is a web browser-based platform that is mobile, tablet and desktop accessible and is protected behind a log in window.
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Figure 2 : LT1 communicates wirelessly with Qgateway which then transmits the data to the Cloud. A single Q Gateway can relay information from up to 100 LT1 sensors (depending on distance form the sensor to the gateway)
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Figure 3: Drilling down from the Map view of the site we are presented with the most recent DGA, moisture and temperature for all 9 transformers on that site. We can immediately see that each sensor is operational and that none of the transformers are at an alarm threshold.
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Figure 4: At the individual sensor level, you see the trends and the measured data for a single transformer. In this case we appear to have low level of hydrogen with some very gradual increase. Overall, this one is a healthy transformer!
The convenience delivered by being wireless results in LT1 sensor batteries eventually draining and the sensor powering down giving the users a months’ notice of its shutdown. These LT1 sensors will deliver a very impressive five years operation from a single set of batteries after which the entire sensor will be replaced (being fully sealed and IP67 it’s not possible to open the sensor to replace the batteries themselves). The Gateway has rechargeable batteries that are being topped up with solar energy during daylight hours every day and so will never need to be replaced.
While its functionality is DGA monitoring on any type of oil filled transformer, the LT1 is designed especially for deployment where there is no instrument power available for traditional wired monitors. Its natural home is the distributed generation / renewables sector such as this deployment on a solar farm but it’s also well suited to industrial or even utility transformer monitoring where its market leading low cost will be appealing.
