Electrical Safety

On-line Partial Discharge Monitoring & Location on a 33kV Offshore Wind Farm Export Cable

• Special thanks to Jordan Edmenson at HVPD for the kind permission to republish
  Link to the original article can be found here

Partial Discharge

Monitoring & Location on a 33kV Offshore Wind Farm Export Cable

Project

An offshore wind farm operator in the UK requested On-Line Partial Discharge monitoring and cable fault location on two 33kV XLPE land sea export cables to an offshore wind farm. The 33kV circuit began from a grid-connected onshore substation feeding a 2 km long land subsea transition joint, which in turn fed a 12 km 3-core cable directly to the offshore wind farm.

Solution

Short-term continuous monitoring was conducted using an HVPD diagnostic device connected to High Frequency Current Transformer (HFCT) and a Transient Earth Voltage (TEV) sensor.

• The HFCT and TEV sensors were installed at the cable terminations during a temporary outage
• The HFCT sensors are split core enabling them to be easily installed around the cable core and earth for detection of PD activity within the cable
• The TEV is a capacitive probe designed to detect local, high frequency PD pulses originating within the switchgear and terminations

Conducting short-term continuous monitoring over a number of days enables intermittent PD activity to be captured and correlated with other parameters such as load, temperature and humidity.

HFCT and TEV Sensors

Background Theory

If significant levels of PD activity were detected, fault location could be carried out using the cable mapping function of the HVPD diagnostic device. Cable mapping is conducted by detecting the an original PD pulse from the fault location as well as a reflected PD pulse (caused when the original PD pulse reaches the far end of the cable). Using the time delta between these pulses, and the signal propagation speed (which is provided in the cable data sheet) the approximate location of the PD source can be identified.

Results

During the short-term monitoring period, high levels of PD activity were detected with the HFCT on Phase L3 of Circuit 1. Cable mapping on this circuit was then carried out to confirm the location of the fault, with the results indicating that the source was located 800m from the onshore substation.

This result was then corroborated with the cable schedule which confirmed the presence of cable joint no.7 at this location. Based on these findings, it was recommended that the affected joint no.7 be replaced. Following this replacement a forensic analysis on the joints was conducted in which significant insulation damage and tracking within the inner insulation section was found.

Partial Discharge Map Showing PD Location

Forensic Examination of Cable Joint

PD Trend Line Before Replacement

PD Trend Line After Replacement

Conclusions and Recommendations

During the short-term monitoring period, high levels of PD activity were detected and cable mapping on this circuit then confirmed the location of the fault. The affected joint was able to be taken out of service and replaced during a scheduled outage, avoiding the risk of an in-service cable failure.

About HVPD

HVPD supplies a comprehensive range of equipment to detect and monitor On-line PD for the condition assessment of in-service power cables, switchgear, motors and generators, and transformers rated at 3.3kV and above. Our PD testing and monitoring technology provide you with an early warning of developing insulation faults, helping you to avoid costly failures and resulting unplanned network outages.

To find out how we can test and monitor your cable network for PD and locate any faults, terminations or joints, get in touch today at [email protected] or call us on 0161 877 6142.

Thorne & Derrick

Specialist Electrical Distributor

Established since 1985, T&D International based in the UK distribute the most extensive range of LV, MV & HV Cable Jointing, Terminating, Pulling & Installation Equipment – contact us today for a competitive quotation.

Key Products : MV Joints & Terminations, Access Chambers, Cable Cleats, Duct Seals, Cable Transits, Jointing Tools, Feeder Pillars, Cable Duct, Earthing & Lightning Protection, Electrical Safety, Cable Glands, Arc Flash Clothing Protection & Fusegear.

Distributors for : 3M, Pfisterer CONNEX, Nexans Euromold, Elastimold, Catu, Roxtec, Emtelle, Centriforce, Lucy Zodion, Alroc, Cembre, Prysmian, Ellis Patents, ABB & Furse.

T&D Providers Of Jointer Training Courses By Pfisterer CONNEX & Nexans Euromold

Reliable Voltage Testing | Pfisterer KP-Test 5 Capacitive Voltage Detector

Voltage Detectors Distributed from Stock | Approved Supplier | UK & Export Sales

Voltage Detectors

Pfisterer KP-Test 5

The KP-Test 5 capacitive voltage detector manufactured by PFISTERER and distributed by Thorne & Derrick can be used for indoor and outdoor medium voltage applications. It indicates the presence of operating voltage. The KP-Test 5 voltage detector is distinguished by its high level of user friendliness and user safety.

Voltage detectors in the KP-Test 5 series perform an automatic self-test when they are switched on. The detectors also give off a clear visual and audible warning to signal the presence of voltage.

Voltage detector provides wider range of application, easier handling, improved signal indication – KP-Test 5 keeps pace with increased market requirements and makes high-quality electrical safety equipment possible.

Pfisterer Voltage Detector

KP-Test 5 Voltage Detector

Tested to EN 61243-1 the capacitive voltage detector can be used in all weather conditions. As with any security-related tool, there are a few basic rules to follow:

The employers’ liability insurance association for energy, textiles, electronics and media products (BG ETEM) currently points out that the contact electrodes or test prods of voltage testers must have conductive electrical contact with the system part to be tested in order to reliably determine the absence of voltage.

Clear measuring conditions, which are covered by the IEC 61243-1 standard, only arise in direct contact with the conductive part of the system. Even the simplest adhesive strips from office supplies can cause voltage drops of a few kV on busbars and lead to incorrect test results.

In practice, busbars are often color-coded, and measurements should never be taken at these points. This fact is due to the principle and applies to devices from all manufacturers. Another important rule: Voltage testers must be checked for proper functioning both before and after the measurement. The built-in self-test function is used for this.

Voltage Detectors 11kV 33kV

The KP-Test 5 family offers the right voltage detector for every application. Medium or High Voltage, alternating or direct current for use on overhead power lines, switchgear, in substations or on railway systems. All devices are individually adapted to our customers’ requirements. PFISTERER offers solutions for all voltage levels from 1 to 420 kV AC.

The SEANEX inner cone solution is an offshore variant of the successful Connex HV connection system that is specially adapted for 66kV inter-array cabling.

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THORNE & DERRICK

Thorne & Derrick are national distributors of LV, MV & HV Cable Installation, Jointing, Substation & Electrical Equipment – servicing businesses involved in cabling, jointing, substation, earthing, overhead line and electrical construction at LV, 11kV, 33kV, 66kV and EHV. Supplying a complete range of power cable accessories to support the installation and maintenance of low/medium and high voltage cable systems:

• Slip-on Cable Terminations
• Cold-shrink Cable Terminations
• Heat-shrink Cable Terminations
• Cable Joints – Heat & Cold-shrink
• Separable Connectors (Euromold)
• Surge Arresters & Switchgear/Transformer Bushings

Key Product Categories: Duct Seals | Cable Cleats | Cable Glands | Electrical Safety | Arc Flash Protection | Cable Jointing Tools | Cable Pulling | Earthing | Feeder Pillars | Cable Joints LV | Joints & Terminations MV 

MV Connex Products | Ex Stock Thorne & Derrick | Inner Cone Cable Connectors 33kV

STRATA Workwear | Skanwear Arc Flash Clothing & Protection

STRATA Workwear Arc Flash Protective Clothing Range

Thorne & Derrick are the UK’s Leading Specialist Distributor of Electrical Safety Equipment to clients working in the Power Transmission & Distribution industry in the onshore and offshore wind, solar, rail, oil/gas, data centre, battery storage and utility sectors – we supply arc flash clothing from a range of brands including STRATA® Protection.

STRATA® Protection a the leading Arc & Flame Protective Clothing brand in the Energy Sector including switching suits for the protection of workers.

All of the garments in the range are globally tested and certified to both European and North American Arc Flash, Flame Retardant and Hi-Visibility standards. The garments not only protect the wearer from a potentially fatal hazard, but are highly robust to handle wear and tear. STRATA Workwear sizes range from ‘extra small’ (XS) all the way through to 4XL.

STRATA Workwear | Arc Flash Clothing Kits

A range of full certified Arc Flash Clothing Kits to provide total protection against arc flash risks for wearers working on or near live electricity (energised), at LV, MV HV power systems.

STRATA Arc Flash Garments

Arc flash garments including shirts, jackets, overalls and coveralls.

Accessories

STRATA workwear arc & flame protective accessories, holdalls and backpacks.

Gloves

The full range of electricians gloves, arc utility gloves, insulating gloves and engineers gloves ranging from ARC Class 00 – Class 4.

Helmets & Visors

Arc flash helmets and face shields/visors.

Arc Flash Garment Care

ELECTRICAL SAFETY PROVIDERS

We protect substation engineers, asset managers, SAPS, cable jointers, overhead linesmen and utility workers with PPE and safety equipment: this includes insulating gloves, arc flash clothing, voltage detectors, insulating matting and portable earthing to ensure worker safety when carrying out repair and maintenance on LV-HV switchgear, transformers, substations and turbines.

All of our Cable Connection & Energisation Accessories including Medium & High Voltage joints, terminations, connectors and cleats are tested to the latest international standards and supporting ranges of professional installation tools are stocked to reduce incident, accident and downtime to plant and people.

Arc Flash Polo Shirts | Coveralls | Sweatshirts | Helmets | Insulating Gloves

Providing Electrical Safety & PPE to Offshore Wind Farm Workers

Thorne & Derrick | LV HV Electrical Safety & PPE Stockists & Specialists

Thorne & Derrick have recently supplied Electrical Safety Equipment to a renewable energy company working on the construction of the worlds largest offshore windfarm project in UK waters. The Personal Protective Equipment (PPE) will provide mitigation against the hazards of impressed/induced voltages prior to and during the pull-in of subsea cables.

Liasing with the Works Manager (Subsea Cables & Flexibles) and the Quality, Health, Safety and Environmental (QHSE) management team a minimum level of PPE and electrical protection was ascertained to protect workers carrying out maintenance and construction tasks in and around exposed cables. Essentially this included robust dielectric footwear, commonly referred to as insulating boots, and hand protection to protect against electrical hazards. The PPE delivered from stock will protect both crews and technicians working at landfall location and onboard the offshore cable laying vessel.

Critical to the project was our rapid response delivery from stock in a mixture of sizes to suit the individual requirements of the offshore workers, engineers and technicians.

Gloves & Boots

For hand protection gauntlet type Class 1 electrical insulating gloves were specified in accordance with Standard EN 60903:2003 – additional mechanical outer protection and cotton inner gloves were supplied. Footwear for electrical protection in accordance with the Standard EN 50321-1:2018 (tested to 20kV) was selected and specified.

• BS EN 60903:2003 | Live Working. Gloves of Insulating Material

• BS EN 50321-1:2018 | Footwear Electrical Protection - Insulating Footwear & Overboots

Boots CATU MV-137 | these insulating boots are designed to protect offshore workers against the risks of step voltage on the ground, or against current circulating between the feet and the ground. The dielectric safety boots provide worker protection against electrical shock up to 20kV across the entire boot and up to 35kV on the sole. CATU’s MV-137 boots are made from high voltage-resistant dielectric compounds with slip-resistant vulcanised blue rubber sole and are available from stock at Thorne & Derrick.

Ex Stock

Gloves CATU CG-1 | Class 1 insulating gloves to provide electrical protection for live voltages up to 7,500V and are fully compliant with IEC 60903 and EN 60903 standards.

Ex Stock

Offshore Electrical Safety

Further Reading Arc flash accidents are not nearly as rare as you would think and the hazards they create are severe. In wind turbines, these hazards are magnified. Read our Electrical Safety Blog about safe wind turbine working. 

• MV HV Cable Laying, Installation & Support Products | Offshore Windfarms
• Pipe & Cable Seals for Onshore Windfarm, Enclosures, Foundation & Stations
• Pipe & Cable Seals for Offshore Windfarm Substations, Enclosures & Foundation
• Cable Cleats & Safe Cable Installations for the Wind Energy Industry
• 33kV v 66kV | A Wind Farm Collection Grid Technical Comparison
• Arc Flash Clothing & Protection For Safe Windfarm & Wind Turbine Working

Electrical Safety & Arc Flash Protection for Offshore Wind Farm Workers

CATU CL-7-4-18 | HV Single Pole Phase Comparator 33kV / 36kV

HV Single Phase Comparators

CATU CL-7-4-18

CATU has recently introduced a new single pole phase comparator, operating up to 36kV, to the Electrical Safety market. The CATU CL-7-4-18 is used to identify voltage differences between two points on 4kV and 18kV networks. Certified to IEC 61481-1 standards.

The new range of Phase Comparators are easy to use with user friendly features:

• Single-pole device with C, K, W end-fitting
• Storage of frequency and phase of distribution network voltages
• Push-button test of the device, which also resets the memory
• Class C: (maximum time for storing information in memory: 15 seconds when not connected to the line) . Non accordance (+110° to +250°)
• LED indicators:
  • Orange (M) indicating the storage of a phase and the mains frequency;
  • Green (C) indicating that the mains phase is identical to the one previously stored (match); + discontinuous beep buzzer.
  • Red (I) indicating that the phase of the network is of a different phase from that previously stored (mismatch) + continuous beep buzzer.
• Voltage difference between the two networks to be compared: +/- 15%.
• Angle difference between the two phases (networks) to be compared: +/- 10°
• The red ring indicates the physical limit to which the phase comparator can be inserted between live parts (57 cm from the red ring to the end fitting).
• Option: Antenna Magnefix with a U Max utilisation : 18 kV, Order Ref C-921545

IEC 61481-1:2014 

Live Working – Phase Comparators – Part 1: Capacitive type to be used for voltages exceeding 1kV a.c. Download IEC Standard.

CATU CL-7-4-18 HV Single Pole Phase Comparator with ‘K’ end fitting

CATU CL-7-4-18 Specification

CATU CL-7-4-18 is an HV single pole phase testing range with a buzzer and LED indicators.

These phase comparators are suitable to be used indoors and outdoors, where temperatures are between -25, and + 55°C (Climatic category – N). CL-7-4-18 is powered by a 6LR61 battery (9V).

High Voltage Electrical Safety

Further Reading

• Electrical Safety – Arc Flash Accidents & Electrocution In LV-HV Installations
  
• Arc Flash Calculation – Selecting Clothing & PPE To Protect Lives Against Arc Hazard
• IEC 61482-2:2018 – Get Up To Speed With The New Arc Flash Standard
• Arc Flash PPE | 7 Top Considerations
• Arc Flash The Basics

Insulating Matting | Voltage Detectors | Substation Kits | Phase Comparators

Arc Flash Clothing | Polo Shirts | Jackets | Coveralls | Trousers | Sweatshirts | Helmets

THORNE & DERRICK

Thorne & Derrick are national distributors of LV, MV & HV Cable Installation, Jointing, Substation & Electrical Equipment – servicing businesses involved in cabling, jointing, substation, earthing, overhead line and electrical construction at LV, 11kV, 33kV, 66kV and EHV. Supplying a complete range of power cable accessories to support the installation and maintenance of low/medium and high voltage power systems:

• Slip-on Cable Terminations
• Cold-shrink Cable Terminations
• Heat-shrink Cable Terminations
• Cable Joints – Heat & Cold-shrink
• Separable Connectors (Euromold)
• Surge Arresters & Switchgear/Transformer Bushings

Key Product Categories: Duct Seals | Cable Cleats | Cable Glands | Electrical Safety | Arc Flash Protection | Cable Jointing Tools | Cable Pulling | Earthing | Feeder Pillars | Cable Joints LV | Joints & Terminations MV