Video: APD-LT

Video transcript

How the APDLT surveys cable heads, arresters, insulators and bushings in service, from the ground, and how every reading becomes a record. A partial discharge is a small breakdown inside an insulation, which does not bridge the conductors. In a cable head it starts where the field concentrates: voids under the insulation screen, rough screen ends, or cuts made when the screen was removed. Each one sends out very high frequency pulses.

The APDLT picks up those pulses between 30 and 47 megahertz, with 60 decibels of dynamic range and plus or minus two decibels of accuracy. The reading travels by Bluetooth Low Energy up to 30 metres, and the module runs 10 hours on 1 9 volt battery. The system has two parts. The measurement module, on the hotstick, faces the device under test with its capacitive sensor. It sends each reading by Bluetooth to the display module. From there, the saved measurements leave by Wi-Fi or a hotspot, as a spreadsheet.

The measurement module is sealed to IP 66 and weighs point 4 3 kilos. The capacitive sensor at its head turns to any angle, to suit the accessory. At the other end, the universal fitting takes any standard hotstick. On its face, the module shows its state. The on and off key, the battery level indicator, and the Bluetooth indicator, which shows the link to the display. At switch on, the module runs a complete self test of its analogue front end. The display module is a rugged 5 and a half inch touch screen,

readable in sunlight and usable with gloves. It is sealed to IP 68, meets MIL standard 8 10 G for shock, drop and vibration, and its battery lasts all day. Everything travels in one compact, semi rigid case: the measurement module, the display module, the USB cable and charger, and an arm band to wear the display while both hands hold the stick. Setting up takes a minute. Fit the 9 volt battery and switch the module on: it tests itself. Open the application on the display and check the Bluetooth link.

Mount the module on the hotstick, and turn the sensor to suit the accessory to be measured. The operator stays on the ground, or in a bucket, and brings the sensor to the accessory on the stick. There is no contact with the conductor and no outage. The reading appears on the display in real time, so the operator never has to approach the energised part. Observation mode measures a single device.

The level is plotted in decibels against time, so its behaviour can be followed at a glance. An audio cue follows the signal, and noise averaging and a timer delay can be set. Comparison mode puts several measurements side by side in a single test, for example the same accessory on each of the 3 phases. The difference between them is shown directly, and the one that stands out is the one to look at. Each recording can carry its evidence:

a picture or a video of the accessory, an audio note, text, tags, and the GPS coordinates of the site. 1000 of devices can be surveyed, and each one is easy to find again. To export, connect the display to Wi-Fi or a hotspot and choose a recipient. The saved measurements and their annotations arrive by email, as a link, in a standard spreadsheet. There is no software to install and no account to create. Four rules. The sensor never touches the conductor.

The stick is an insulated hotstick, and the site rules for live work apply. Keep within the 30 metre radio range. And replace the 9 volt battery when its indicator asks for it. It is used to build preventive maintenance programmes for overhead apparatus: cable heads, line arresters, insulators and bushings, on medium and high voltage, in substations and along the lines. Partial discharge detection, from Amperis.