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INEOS Online Cable PD Monitoring


  • 01 June 2021

Case Studies

SUMMARY


INEOS is a major multi-national group of companies specialising in petro-chemical production. Its largest manufacturing site is based at Grangemouth, Scotland, which is home to its Olefins and Polymers (O&P UK) business, as well as a crude oil refinery that produces the bulk of Scotland’s fuel. It owns and operates one of the
largest private electricity distribution networks in Europe. EA Technology specialises in providing technical services
and consultancy within the power industry worldwide. One of its key areas of expertise is the detection and
measurement of Partial Discharge (PD) in High Voltage (HV) switch gear and equipment.
This paper describes a joint Pilot Study between the two companies to install an online Cable PD monitoring system
on 18 critical 33kV XLPE cables that link the INEOS owned Combined Heat and Power (CHP) plant to the main
distribution substation at INEOS’ O&P UK manufacturing site at Grangemouth. The monitoring system, known as
the CableData Monitor (CDM), detects PD on the cable by means of Radio Frequency Current Transformers (RFCTs)
clipped non-intrusively around the earth screen terminations at one end of each of the cables. The system became
operational in October 2016 and has since detected and recorded PD activity on three of the 18 cables being
monitored. An analysis of the captured waveforms has located the PD sources to the vicinity of newly installed cable
joints. This paper explains how the PD levels (which vary with time) are being monitored using trending and
threshold alarms to manage the cables whilst they remain in operation. This monitoring may thus allow the
replacement of the joints at the next planned maintenance outage rather than having to undertake an earlier
intervention, avoiding unnecessary downtime of the CHP. Additionally, resources and personal safety measures have
been put in place to manage an outage should one occur in the meantime.
The results from the CDM are also compared to conventional off-line VLF measurements that were performed on the
same cables prior to energisation. The correlation was accurate enough to warrant not taking the cables out of service
for further VLF testing (instead relying on the on-line measurements) which again has resulted in further financial
saving by alleviating the CHP plant downtime required for traditional testing methods. As well as providing a unique
opportunity to study the behaviour of the PD with time, if the cable joints can be replaced and subsequently
forensically examined before failure occurs, this may provide valuable evidence (that might otherwise be destroyed
during a failure) that could identify the cause of the PD - thus allowing corrective action to protect against it
happening again in the future. In conclusion, the paper demonstrates how INEOS’ pro-active approach to managing
PD on its critical HV cables has helped to save money, whilst at the same time, enhance the reliability of its electricity
distribution network at its site at Grangemouth.


KEYWORDS


Partial discharge, continuous on-line monitoring, cable condition assessment, PD measurement, detection, location,
failure analysis, CableData Monitor, CableData Collector, CDM, CDC, 24/7

 

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