Trinity Mirror – HV Condition Assessment
30 July 2020
‟“We were fortunate to find EA Technology who introduced us to PD technology, they surveyed all site HV switchgear within a day and submitted a detailed report, the survey was able to find failing CT which we have been able to change at our convenience rather than it fail in production. EA Technology are now carrying out a PD survey at our Oldham printing plant.” ”
Engineering Production Manager and Senior Authorized Person
UltraTEV Plus2 confirms and classifies Partial Discharge on Trinity Mirror HV Network
Client – Trinity Mirror Print, Watford Site
TMPW is the largest print site of Trinity Mirrors seven sites. By night it prints its national titles such as ‘The Mirror’, ‘The Racing Post’ and ‘The Independent’. During the day it carries out regional and contract printing. Its presses can produce newspapers at 86,000 copies an hour, equating to approx 45 million newspapers a month.
The Watford site has a 11kV, 7MVA, 50Hz private network consisting of seven 11kV substations across the plant and twelve dedicated 11kV transformers for its twelve printing presses fed via fifteen circuit breakers.
In Feb 2016 EA Technology performed a site Partial Discharge (PD) survey using the UltraTEV Plus and UltraTEV Locator. The report highlighted PD activity in the substation switchgear.
Garry Crask, Engineering Production Manager and Senior Authorized Person on the site requested a demonstration of the UltraTEV Plus2 in order to firstly confirm the location and subsequently use it to confirm that the service provider had fixed the issue.
An on-site demonstration was arranged for the UltraTEV Plus2. Using the magnetic ultrasonic contact probe the instrument found the PD associated with the HV cabinets, and determined the location of the discharge inside the cabinet. The on screen diagnosis and interpretation feature instantly identified the problem as ultrasonic discharge associated with degradation of the insulation surface.
On opening the HV cabinet for rectification work a Current Transformer (CT) was found to have significant electrical treeing on its surface (see Figure 1).
The CT was replaced and the UltraTEV Plus2 was used to confirm that the PD source had indeed been eliminated.
If the CT had not been replaced, it would have failed; at best the failure could have been the single 11kV switch tripping resulting in many weeks of press down time while a new CT was sourced, at worst it could have led to a fire resulting in multiply presses being out of action due to substantial switchgear damage.