The document discusses partial discharge (PD) techniques for measuring the condition of aging high voltage and medium voltage switchgear. It provides 3 key points:
1) PD activity is a major cause of long-term degradation of insulation in switchgear. Measuring PD can detect defects before complete failure and allow targeted maintenance.
2) The latest PD measuring instruments use dual sensors to detect both surface and internal PD non-intrusively. Measurements of PD pulses externally can indicate the insulation condition.
3) Condition-based maintenance using PD measurements can improve safety, reliability and lower costs compared to time-based maintenance. Utilities like SP Powergrid in Singapore have seen significant benefits including reduced outages and savings of
Seminar for eight semester electrical engineering on Conventional and
Un-Conventional Partial Discharge Detection Methods in High Voltage XLPE Cable Accessories
High Voltage On-Site Testing with Partial Discharge Measurement (Cigre 502)AHMED MOHAMED HEGAB
During the life cycle of high voltage (HV) apparatus or systems many tests and measurements are performed to characterize the insulation condition. The results of these tests and
measurements should be compiled in a “life data record”, which supplies information on trends of diagnostic indicator values. The HV on-site test with partial discharge (PD) measurement has an intermediate position between routine tests and in-service monitoring measurements (on-line or offline)
PARTIAL DISCHARGES
IN TRANSFORMERS PARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERS
Partial Discharge Detection Products by EA TechnologyRyan McFallo
EA Technology is the global leader in MV Partial Discharge detection. EA’s unique technology allows real time partial discharge detection and monitoring without interrupting service, EA also provides on-site partial discharge surveys.
Would you like to learn more about partial discharge detection and monitoring products/services?
Visit Technical Sales-Northwest at http://www.techsalesnw.com
Seminar for eight semester electrical engineering on Conventional and
Un-Conventional Partial Discharge Detection Methods in High Voltage XLPE Cable Accessories
High Voltage On-Site Testing with Partial Discharge Measurement (Cigre 502)AHMED MOHAMED HEGAB
During the life cycle of high voltage (HV) apparatus or systems many tests and measurements are performed to characterize the insulation condition. The results of these tests and
measurements should be compiled in a “life data record”, which supplies information on trends of diagnostic indicator values. The HV on-site test with partial discharge (PD) measurement has an intermediate position between routine tests and in-service monitoring measurements (on-line or offline)
PARTIAL DISCHARGES
IN TRANSFORMERS PARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERSPARTIAL DISCHARGES IN TRANSFORMERS
Partial Discharge Detection Products by EA TechnologyRyan McFallo
EA Technology is the global leader in MV Partial Discharge detection. EA’s unique technology allows real time partial discharge detection and monitoring without interrupting service, EA also provides on-site partial discharge surveys.
Would you like to learn more about partial discharge detection and monitoring products/services?
Visit Technical Sales-Northwest at http://www.techsalesnw.com
Guidelines for Unconventional Partial Discharge Measurement (CIGRE 444)AHMED MOHAMED HEGAB
Several non-conventional PD detection methods based on acoustic and electromagnetic phenomenon have been used for some time for PD detection on power cables, transformers, GIS and generators. Up to now there have not been accepted procedures and guidelines for “non-conventional methods” compared to conventional methods. There are many open questions including: calibration or sensitivity verification procedures, techniques for noise suppression, methods of
fault location, and energy equivalency, among others. The authors of this guide believe that now is the time to prepare guidelines and international recommendations for these non-conventional PD detection methods in order to ensure reproducible and comparative PD measurements on high voltage equipment between users.
Lightning and Surge Protection Strategy for InstrumentationRekaNext Capital
When Sensors are deployed outdoor, they need to be protected from Lightning voltage Surges. These are basic simple devices used to protect expensive sensors as voltage surges can occur anytime. This increase longivity of sensors and instruments
Practical handbook-for-relay-protection-engineersSARAVANAN A
The ‘Hand Book’ covers the Code of Practice in Protection Circuitry including standard lead and device numbers, mode of connections at terminal strips, colour codes in multicore cables, Dos and Donts in execution. Also, principles of various protective relays and schemes including special protection schemes like differential,
restricted, directional and distance relays are explained with sketches. The norms of protection of generators, transformers, lines & Capacitor Banks are also given.
The following topics are covered: components of power distribution systems, fuses, padmounted transformers, pole mounted transformers, vault installed transformers, transformer stations protection, transformer connections, thermometers, pressure relief devices, restricted ground faults, differential protection current transformers connections, overexcitation, inrush current, percentage differential relays, gas relays, characteristics of CTs.
Cable sizing to withstand short circuit currentLeonardo ENERGY
In a cable a short circuit causes very extreme stresses which are proportional to the square of the current:
• A temperature rise in the conducting components subjected to current flow such as conductor, screen, metal sheath, armour. Indirectly the temperature of adjoining insulation and protective covers also increases,
• electro-magnetic forces between the current-carrying components.
The temperature rise is important for its effect on ageing, heat pressure characteristics etc., and should be limited to a permissible short-circuit temperature. The thermo-mechanical effects of the current shall also be considered.
For a given short-circuit duty therefore the short-circuit capacity of a cable installation is to be investigated with respect to all these parameters. For multi-core cables in most instances the thermal effect - related to the magnitude of fault current and clearance time - is the critical parameter, since the cable will normally have enough mechanical strength. With single-core cables however, in addition, the mechanical effect - related to the magnitude of the peak short-circuit current - is of such significance that, next to the thermal, the mechanical with- stand of both cable and its supports is to be investigated.
Also accessories must be rated with respect to thermal and mechanical short-circuit stresses.
The short-circuit withstand of a cable system is not quantitatively defined with regard to permissible number of repeated short circuits, degree of deformation or destruction or impairment quality. It is expected, however, that a cable installation will remain safe in operation and that any deformation remains within tolerable limits even after several short circuits.
Transformer vector group_test_conditionsSARAVANAN A
Test Conditions for various vector groups commonly under use are listed along with pictorial representation. Assuming the reader has sufficient exposure to transformer winding connections.
Transformer Vector Group Test conditions
YNd1, YNd11, Dyn11, YNyn0and more
Guidelines for Unconventional Partial Discharge Measurement (CIGRE 444)AHMED MOHAMED HEGAB
Several non-conventional PD detection methods based on acoustic and electromagnetic phenomenon have been used for some time for PD detection on power cables, transformers, GIS and generators. Up to now there have not been accepted procedures and guidelines for “non-conventional methods” compared to conventional methods. There are many open questions including: calibration or sensitivity verification procedures, techniques for noise suppression, methods of
fault location, and energy equivalency, among others. The authors of this guide believe that now is the time to prepare guidelines and international recommendations for these non-conventional PD detection methods in order to ensure reproducible and comparative PD measurements on high voltage equipment between users.
Lightning and Surge Protection Strategy for InstrumentationRekaNext Capital
When Sensors are deployed outdoor, they need to be protected from Lightning voltage Surges. These are basic simple devices used to protect expensive sensors as voltage surges can occur anytime. This increase longivity of sensors and instruments
Practical handbook-for-relay-protection-engineersSARAVANAN A
The ‘Hand Book’ covers the Code of Practice in Protection Circuitry including standard lead and device numbers, mode of connections at terminal strips, colour codes in multicore cables, Dos and Donts in execution. Also, principles of various protective relays and schemes including special protection schemes like differential,
restricted, directional and distance relays are explained with sketches. The norms of protection of generators, transformers, lines & Capacitor Banks are also given.
The following topics are covered: components of power distribution systems, fuses, padmounted transformers, pole mounted transformers, vault installed transformers, transformer stations protection, transformer connections, thermometers, pressure relief devices, restricted ground faults, differential protection current transformers connections, overexcitation, inrush current, percentage differential relays, gas relays, characteristics of CTs.
Cable sizing to withstand short circuit currentLeonardo ENERGY
In a cable a short circuit causes very extreme stresses which are proportional to the square of the current:
• A temperature rise in the conducting components subjected to current flow such as conductor, screen, metal sheath, armour. Indirectly the temperature of adjoining insulation and protective covers also increases,
• electro-magnetic forces between the current-carrying components.
The temperature rise is important for its effect on ageing, heat pressure characteristics etc., and should be limited to a permissible short-circuit temperature. The thermo-mechanical effects of the current shall also be considered.
For a given short-circuit duty therefore the short-circuit capacity of a cable installation is to be investigated with respect to all these parameters. For multi-core cables in most instances the thermal effect - related to the magnitude of fault current and clearance time - is the critical parameter, since the cable will normally have enough mechanical strength. With single-core cables however, in addition, the mechanical effect - related to the magnitude of the peak short-circuit current - is of such significance that, next to the thermal, the mechanical with- stand of both cable and its supports is to be investigated.
Also accessories must be rated with respect to thermal and mechanical short-circuit stresses.
The short-circuit withstand of a cable system is not quantitatively defined with regard to permissible number of repeated short circuits, degree of deformation or destruction or impairment quality. It is expected, however, that a cable installation will remain safe in operation and that any deformation remains within tolerable limits even after several short circuits.
Transformer vector group_test_conditionsSARAVANAN A
Test Conditions for various vector groups commonly under use are listed along with pictorial representation. Assuming the reader has sufficient exposure to transformer winding connections.
Transformer Vector Group Test conditions
YNd1, YNd11, Dyn11, YNyn0and more
This seminar will provide a comprehensive understanding of the various types of generators, exciters, automatic voltage regulators (AVR’s), and protective systems. This seminar will focus on maximizing the efficiency, reliability, and longevity of this equipment by providing an understanding of the characteristics, selection criteria, common problems and repair techniques, preventive and predictive maintenance. The emphasis in this seminar is on inspection methods, diagnostic testing, troubleshooting, modern maintenance techniques, refurbishment, rewind and upgrade options, and advanced methods for preventing partial discharge and other failures.
This seminar is a MUST for anyone who is involved in the selection, applications, or maintenance of generators, exciters, automatic voltage regulators (AVR’s), and protective systems because it covers how this equipment operates, the latest maintenance techniques, and provides guidelines and rules that ensure the successful operation of this equipment. In addition, this seminar will cover in detail the basic design, operating characteristics, specification, selection criteria, advanced fault detection techniques, critical components and all preventive and predictive maintenance methods in order to increase reliability of the equipment and reduce the operation and maintenance cost.
POWER SYSTEM PROTECTION
Protection Devices and the Lightning,. protection,
Lightning protection, Introduction
Air Break Switches
Disconnect switches
Grounding switches
Current limiting reactors
Grounding transformers
Co-ordination of protective devices
Grounding of electrical installations
Electric shock
Lightning protection
Lightning Arrestor
Inspection of Electrical Installations in HomesLeonardo ENERGY
* Focuses on the importance of carrying out measurements as well as visual inspections of Europe’s ageing housing stock.
* Describes main potential hazards of old domestic wiring. Defines verification, inspection, testing and maintenance.
* Suggests that verification should include an inspection and tests. Proposes that copper wiring should replace aluminium wiring.
PRINCIPLES OF Electrosurgery
Electrosurgery is the application of a high- frequency electric current to biological tissue to cut, coagulate, desiccate, or fulgurate tissue.
PRINCIPLE
• Understanding the principles of electricity is a strong foundation for best practices in electro surgical patient care.
• Electrosurgical equipment and accessories facilitate the passage of high frequency oscillating electric currents through tissue between two electrodes to fulgurate desiccate or cut tissue.
MONOPOLAR
Active electrode at surgical site.
Return electrode at another site.
Current flows through the body.
Tissue effect takes place at a single active electrode and is dispersed (circuit completed) by a patient return electrode.
BIPOLAR
Active and return electrodes within the instrument.
Current flows confined to tissue between electrodes.
Current flows are limited and contained in the vicinity of the two electrodes.
As current passes through the tissue from one electrode to the other the tissue is desiccated and the resistance increases, as resistance increases current flow decreases.
What is leakage current testing What is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testingWhat is leakage current testing
Isolation Procedures for Safe Working on Electrical Systems and Equipment by the JIB | solation Procedures for Safe Working on Electrical Systems and Equipment
This chart shows the safe isolation procedure that you should use when working on electrical systems and equipment.
You'll receive a printed copy of this from your Training Provider, but it's also here as a handy reference to keep electronically.
THE RULES OF SAFE ISOLATION ARE:
Obtain permission to start work (a Permit may be required in some situations)
Identify the source(s) of supply using an approved voltage indicator or test lamp
Prove that the approved voltage indicator or test lamp is functioning correctly
Isolate the supply(s)
Secure the isolation
Prove the system/equipment is DEAD using an approved voltage indicator or test lamp
Prove that the approved voltage indicator or test lamp is functioning correctly
Put up warning signs to tell other people that the electrical installation has been isolated
Once the system/equipment is proved DEAD, work can begin
Uploaded by THORNE & DERRICK LV HV Jointing, Earthing, Substation & Electrical Eqpt | Explosive Atmosphere Experts & ATEX IECEx.
THORNE & DERRICK based in the UK are international distributors of LV, MV & HV Cable Installation, Jointing, Substation & Electrical Equipment.
Since 1985, T&D have established an international reputation based on SERVICE | INTEGRITY | TRUST.
Contact us for 3M, ABB, Alroc, AN Wallis, CATU, Cembre, Centriforce, CMP, CSD, Elastimold, Ellis Patents, Emtelle, Euromold, Filoform , Furse, Lucy Electric & Zodion, Nexans, Pfisterer, Polypipe, Prysmian, Roxtec, Sicame, WT Henley.
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
Securing your Kubernetes cluster_ a step-by-step guide to success !KatiaHIMEUR1
Today, after several years of existence, an extremely active community and an ultra-dynamic ecosystem, Kubernetes has established itself as the de facto standard in container orchestration. Thanks to a wide range of managed services, it has never been so easy to set up a ready-to-use Kubernetes cluster.
However, this ease of use means that the subject of security in Kubernetes is often left for later, or even neglected. This exposes companies to significant risks.
In this talk, I'll show you step-by-step how to secure your Kubernetes cluster for greater peace of mind and reliability.
Generating a custom Ruby SDK for your web service or Rails API using Smithyg2nightmarescribd
Have you ever wanted a Ruby client API to communicate with your web service? Smithy is a protocol-agnostic language for defining services and SDKs. Smithy Ruby is an implementation of Smithy that generates a Ruby SDK using a Smithy model. In this talk, we will explore Smithy and Smithy Ruby to learn how to generate custom feature-rich SDKs that can communicate with any web service, such as a Rails JSON API.
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Transcript: Selling digital books in 2024: Insights from industry leaders - T...BookNet Canada
The publishing industry has been selling digital audiobooks and ebooks for over a decade and has found its groove. What’s changed? What has stayed the same? Where do we go from here? Join a group of leading sales peers from across the industry for a conversation about the lessons learned since the popularization of digital books, best practices, digital book supply chain management, and more.
Link to video recording: https://bnctechforum.ca/sessions/selling-digital-books-in-2024-insights-from-industry-leaders/
Presented by BookNet Canada on May 28, 2024, with support from the Department of Canadian Heritage.
Neuro-symbolic is not enough, we need neuro-*semantic*Frank van Harmelen
Neuro-symbolic (NeSy) AI is on the rise. However, simply machine learning on just any symbolic structure is not sufficient to really harvest the gains of NeSy. These will only be gained when the symbolic structures have an actual semantics. I give an operational definition of semantics as “predictable inference”.
All of this illustrated with link prediction over knowledge graphs, but the argument is general.
Smart TV Buyer Insights Survey 2024 by 91mobiles.pdf91mobiles
91mobiles recently conducted a Smart TV Buyer Insights Survey in which we asked over 3,000 respondents about the TV they own, aspects they look at on a new TV, and their TV buying preferences.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024
Partial Discharge Techniques For Measuring Condition Of MV & HV Switchgear
1. 3100 words with case studies (US)
Partial Discharge (PD) techniques for measuring
the condition of ageing HV/MV switchgear
By Neil Davies, Director, EA Technology International
Throughout the world, the electricity transmission and distribution industry is experiencing major
issues: pressure from governments and customers to keep their systems operating reliably,
pressure from shareholders to reduce overhead costs and pressure to replace ageing
equipment.
Owners and operators of high voltage (HV) and medium voltage (MV) networks are facing ever
increasing challenges to maximize utilization of existing equipment and reduce operational costs,
whilst maintaining and improving system performance. Yet they all have the same problem: an
ageing infrastructure of equipment that has been installed and in operation for 20, 30 and in most
cases 40 years.
Switchgear in general has a proven record of reliability and failures are rare. However, when
switchgear fails, the consequences are often catastrophic. Damage to switchgear itself can be
extremely expensive. The consequences can involve damage to plant and buildings: and on rare
occasions death or serious injury to people.
Undetected degradation of switchgear may lead to sudden, explosive failures – sometimes with
catastrophic results
Switchgear maintenance is usually considered low priority by most companies, but a solid
maintenance program is much less costly than the impact of switchgear failure. Giving
maintenance the thought and effort it deserves improves safety, reliability and profitability: and
the latest non-invasive maintenance procedures are proven to prevent switchgear failure.
2. One of the most valuable new methods for monitoring the condition of HV and MV switchgear
involves the use of instruments to measure Partial Discharge (PD) activity non-intrusively.
Causes of Switchgear Failure
PD activity is a major cause of the long term degradation of insulation in HV and MV switchgear.
EA Technology’s experience of working with switchgear operators for more than 30 years
indicates that PD activity is a factor in around 85% of disruptive substation failures.
Issues of the mechanical operation of switching equipment are relatively easy to address, using
tests and maintenance procedures prescribed by the manufacturer. But standard maintenance
procedures are unlikely to detect the degradation of insulating components, which are associated
with the ageing process and are the most common cause of unexpected failures, especially if
triggered by environmental or electrical stresses.
The majority of the degradation processes affecting insulating components, such as bushings,
cable termination, current and voltage transformers, are associated with PD activity. This can be
defined as a localised electrical discharge in an insulation system that does not completely bridge
the electrodes. PD activity associated with the ageing and degradation of insulation typically
increases with the evolution of the defect. Therefore, the measurement of PD activity can be used
as a diagnostic tool, to assess equipment condition and to locate the defect source, enabling
selective intervention to rectify or remove the ageing component prior to complete failure.
What is Partial Discharge (PD) Measurement?
The basis of PD detection and monitoring is that the most common failure mode for electrical
assets is insulation breakdown, leading to flashover. These types of breakdowns produce the
most dramatic failures of switchgear and transformers, often leading to explosions and fires in the
event that protection systems fail to operate.
Insulation and insulation systems do not usually break down quickly. They are more likely to
suffer progressive deterioration over time, manifested in the form of increasing PD activity.
Fortunately for the owners and operators of electrical assets, it is now possible to measure and
quantify PD activity in live switchgear with unprecedented accuracy. This non-intrusive approach
to assessing the condition of switchgear insulation has been adopted by many countries
throughout the world.
Taking PD measurements using portable, lightweight and simple-to-use instruments is an ideal
method for evaluating HV electrical assets with a range of insulation types, including oil,
compound (bitumen) and cast resin. During a temporary over-voltage, during a high voltage test,
or under transient voltage conditions during operation, partial discharges may occur on insulation
of this type, which includes gas, liquid, and solid materials. If these partial discharges are
sustained due to poor materials, design, and/or foreign inclusions in the insulation, degradation
and possible failure of the insulation structure may occur.
In practice, PD activity in HV and MV insulation takes two forms: surface partial discharge and
internal partial discharge.
Surface Partial Discharge
When surface PD Activity is present, tracking occurs across the surface of the insulation, which is
exacerbated by airborne contamination and moisture. Often moisture combines with the NOx
gasses to produce nitric acid which attacks the surrounding metalwork and leads to severe
corrosion of the equipment. Insulation surfaces affected by such an acid attack produce an ideal
surface for tracking to occur, leading to the creepage distance of the insulator being
3. compromised. Tracking is the result of carbonization of the surface of insulation, brought on in the
early stages by the breakdown of contaminates.
Surface PD leads to erosion of the insulation as illustrated in Figure 1 and tracking phenomena
as illustrated on the CT (Current Transformer) in Figure 2.
Figure 1 – Damage caused by surface PD activity
Figure 2 – Treeing surface erosion on a current transformer
Surface discharges tend to occur between the particles of a contaminant, producing heat, light,
smoke, sound, electromagnetic radiation and ozone and nitrogen gasses. In the early stages of
this type of degradation process, and if an air path from the discharge site to the outside of the
equipment is present, the high frequency sound waves generated by the partial discharge activity
are readily detected using sensitive ultrasonic detection equipment in the 40kHz range.
Surface discharges are best detected using an ultrasonic detection instrument. However, there
must be an uninterrupted air path between the discharge site and the instrument to allow the
sound pressure waves to be detected externally.
Internal Partial Discharge
Internal partial discharge occurs within the bulk of insulation materials and is most commonly
caused by age, poor materials or poor quality manufacturing processes. The current transformer
illustrated in figure 3 was known to be exhibiting internal partial discharge. When it was removed
and sectioned, the damage was seen to be at the top and is illustrated in the figure on the right.
4. Figure 3 – Internal partial discharge
Within all insulation material, however manufactured, microscopic voids or cracks are present.
When in use, the insulation has one end connected to high voltage and the other to ground,
causing these voids and cracks to charge up and discharge with the 60Hz cycle, like small
capacitors. Eventually, because the breakdown strength of air is less than that of the surrounding
insulation, the air breaks down with a (very small) arc and a partial discharge occurs. These arcs
produce heat, light, smoke, sound and electromagnetic radiation: but as the void is buried within
the insulation material, only the electromagnetic radiation is detectable externally.
This discharge action also erodes the voids, making them bigger: and as they get bigger, the
discharge energy dissipated with each discharge increases in magnitude. During this process,
carbonisation of the inner surface of the void occurs, which progressively builds up to make the
void conductive and increases the electrical stress on the next void. This causes the process to
be repeated throughout the insulation system, leading to enough conductive voids in the
insulation to cause it to fail. This occurs even under normal working voltages and particularly
following transient over-voltages caused, for example, by switching operations.
The electromagnetic pulses produced by internal partial discharges are conducted away in every
direction by the surrounding metalwork. This charge in motion gives rise to an electric current
which, when it impinges on the impedance of the metal casing, leads to a very high frequency
voltage pulse. These high frequency voltage pulses (between 0.1mV and a few volts) escape
through joints in the metalwork and pass from the inner to the outer surface of the equipment and
then down to ground. The voltage pulse will stay on the surface of the steelwork, as their high
frequency leads to a skin effect.
These pulses were first observed at EA Technology in 1974 by Dr John Reeves and were termed
Transient Earth Voltages (TEVs). They were given this description because they only last for a
very short time and are travelling down to earth (ground). It was found after extensive trials that
these TEV signals are directly proportional to the magnitude of any active partial discharge
activity and the condition of the insulation for switchgear of the same type and model, measured
at the same point. This produced a very powerful comparative field based technique for non-
invasively checking the condition of switches of the same type and manufacture, whilst the
equipment is live and in service.
When new switchgear is tested for partial discharge under factory conditions, very expensive
bench top test equipment is used and the reading is expressed in pico-coulombs (pC): a value
5. obtained by direct measurement with the switchgear out of service. Once the switchgear or other
equipment has been installed and in service for some time, pico-coulomb readings from direct
measurements become relatively meaningless, as the individual service history (fault operations,
maintenance history) of each item of HV/MV equipment will lead to variations in their individual
insulation systems. Furthermore, whilst partial discharge measurements on new switchgear are a
very reliable indication of the build quality as it leaves the factory, it is older switchgear that is at
more risk from failure due to partial discharge.
If allowed to continue unchecked, either mechanism (surface or internal partial discharge) will
lead to failure of the insulation system under normal working stress, resulting in catastrophic
failure of the equipment.
Interpretation of TEV Measurements
The pulses that are being measured on the outside of the equipment are represented in the
Lissojous Figures contained in Annex A of IEEE std 1291 – 1993, an example of which is shown
in Figure 4:
Figure 4 - Lissajous Figure of Internal Discharge in a Solid Dielectric Cavity
ref IEEE std 1291 – 1993
It can be seen from that for each type of activity, the pulses shown have two distinct features: the
size (or magnitude) of the individual pulse and the number of pulses per cycle. In all instances,
the underlying feature is that as the partial discharge activity increases over time, the magnitude
and number of pulses per cycle increases. The method of interpreting the TEV readings relies on
being able to combine two aspects in the manner shown in Figure 5.
6. Figure 5 – Analysis of Transient Earth Voltages (TEV’s)
As shown, a low number and low magnitude of pulses means that there is little risk of insulation
failure. Either a low number of high magnitude pulses or a high number of low magnitude pulses
means that the risk of insulation failure is increasing and more regular testing should be
undertaken. Finally, a high number of high magnitude pulses means that the risk of failure may be
unacceptable and intervention is required at the earliest opportunity.
EA Technology began making partial discharge measurements of switchgear using TEV
detection instruments in 1983. Since that time, EA Technology has assembled, with the co-
operation of all the UK power utilities, a database of partial discharge survey results, with over
100,000 entries, covering many different manufacturers and types of high-voltage switchgear and
associated equipment.
When a survey is undertaken, the TEV readings (in dBmV) are compared with the database
results. If the level of partial discharge is within the top 5% of the database values for comparative
equipment (of the same voltage level, insulation type and design), then it is deemed to be in the
‘red’ quadrant of Figure 5. If the readings are in the top 25% of the database values, then the
equipment is deemed to be in the ‘amber’ quadrant. Below this level, the equipment is deemed to
be in the ‘green’ quadrant.
PD Measuring Instruments
PD testing has been used to check the condition of insulation systems in MV/HV assets for many
years, so it is a well proven technology in its own right. However, it is only quite since the early
2000s that more lightweight, portable and effective monitoring tools have been developed and its
full potential as a strategic technique for asset maintenance and management has been realised
fully.
The latest developments in PD measuring instruments are based on building dual sensors into
single instruments: ultrasonic sensors principally to measure surface PD activity, plus TEV
sensors to measure internal activity. This has led to the launch of a whole family of new
instruments, each of which has a specific role in the detection, location, measurement and
monitoring over time of PD activity.
Amplitude of pulses (in dBmV)
Number
of pulses
per cycle
Low High
Low risk of
failure
Unacceptable
risk of failure
Some risk of
failure
Some risk of
failure
Low
High
7. Perhaps the most historically significant of the new PD tools is EA Technology’s UltraTEV
Detector™: the world’s first dual sensor handheld PD detection tool, which in 2007 won the
Queen’s Award for Industry: Innovation – one of Britain’s top industrial awards. It is now standard
issue for substation use with every electricity network operator in the UK and has been widely
adopted by operators worldwide.
The UltraTEV Detector™ has been compared to a Apple iPod because of its ease of use,
minimum training required and the user friendly interface, beneath which lies a great deal of
technological development. A single button turns it on and a simple traffic light system shows the
operator instantly if PD activity is at one of three levels: green indicates OK, amber indicates that
the asset require further investigation, and red shows that it requires immediate intervention
and/or that PD activity is at a dangerous level.
The latest handheld instruments measure PD activity as both ultrasonic and TEV emissions
Whilst the basic Detector is invaluable for taking ‘first pass’ PD readings quickly, it has spawned a
range of even more sophisticated dual sensor instruments of increasing versatility. The UltraTEV
Plus+™ (pictured above) for example, presents ultrasonic emissions as numerical decibel values
and audible signals, which engineers can listen to via headphones, with the option of a directional
dish microphone for measuring PD activity in overhead assets. Measurement of internal PD
activity in the form of TEV signals is presented as numerical values: and a continuous PD
measurement mode incorporates maximum level, pulse count per cycle and severity level.
Dual sensor alarm systems continuously monitor assets for critical PD activity
8. Dual sensors are also built into the UltraTEV Alarm™ system (pictured), which provides
permanent or semi-permanent monitoring for PD activity in multiple assets or whole substations.
When PD activity reaches critical levels, the system automatically generates alerts via SMS or
email.
The UltraTEV Locator™ features twin probes to locate the source of PD activity accurately, using
time of flight measurement of pulses, as well as quantifying the level of PD activity in single probe
mode. The UltraTEV Monitor™ uses multiple probes, networked to a central server, to monitor
PD activity over time in hundreds of assets simultaneously, and includes software which
automatically analyses and interprets activity in the form of condition reports. This has also been
joined by the PD Monitor GIS™, a system specifically designed to monitor the condition of
extreme high voltage gas insulated switchgear by measuring internal partial discharges in the
UHF range.
CONCLUSION
At its most basic level, the ability to detect and measure PD activity in live assets is an extremely
valuable technique for spotting faults in the early stages of their development, before they
become failures and outages. It is also a uniquely effective way of ensuring the safety of
personnel, to the extent that it is now standard practice for many engineers to check for PD
activity every time before they will enter a substation.
However, it is rapidly becoming apparent that the greatest commercial value of PD measurement
is the ability to use accurate data on the condition of assets to change fundamentally the way
they are managed. Instead of basing asset maintenance and replacement on time schedules,
assets can be managed more efficiently on the basis of their actual condition. The results of this
change include less needless invasive maintenance, less downtime, potentially longer asset life,
greater safety and lower operating costs. The availability of data on the condition of each asset
also leads to more intelligence-based (and cost effective) decisions on asset replacement and
refurbishment.
As the experience of SP Powergrid in Singapore shows, the bottom line is that condition
measurement pays rich dividends.
More information from Neil Davies:
t. +44 151 347 2308
e. neil.davies@eatechnology.com
w. www.eatechnology.com
9. CASE STUDY 1: SP Powergrid, Singapore
SP Powergrid’s network includes nearly 10,000 substations, 40,000 switchgear sets, 14,000
transformers and 30,000km of cable. Since incorporating condition monitoring into its systems, it
has dramatically improved an already excellent performance. The System Average Interruption
Duration Index (SAIDI) has averaged less than 1 minute pa over a recent three year period.
NB: The blip in 2004/5 was caused by a third party supply issue outside SP Powergrid’s control.
SP Powergrid estimates that over the last eight financial years, condition monitoring has enabled
it to avert 450 network failure incidents, with a net financial saving of US$29 million. In addition to
improving customer service, it has been able to pass cost savings on to them.
10. CASE STUDY 2: ESB Networks (Dublin Ireland)
In 2002, a post-fault forensic investigation revealed that insulation failure was the root cause of a
catastrophic failure of switchgear that occurred shortly after a switching operation. The failure was
on a cast-resin ring main unit (RMU) that had been installed on ESB Networks’ (Dublin, Ireland)
10kV distribution network for more than 20 years. This failure resulted in the need for the utility to
revisit the process and procedures it had developed to manage the ageing switchgear population.
As a result of the failure, ESB placed an immediate operational restriction on all 250 substations
equipped with the same type of switchgear. The restriction required that this type of switch only
be operated after it had been de-energized by switching further up the line. The restriction
resulted in severe disruption to customers’ supplies and led ESB to experience major difficulties
in managing network operations.
Following field trails, ESB has solved this problem by issuing all operational switching and
inspection staff with handheld partial discharge measuring instruments, to check that PD activity
is at a non-critical level prior to switching.
CSE STUDY 3: ABB (Italy)
ABB (Italy) conducted similar trials to assess the capability of commercial non-intrusive PD
measuring equipment to detect and locate different PD sources induced in a 17.5 kV
metalclad/internal arc switchgear assembly, comparing the performance with a conventional
electrical detection system.
ABB concluded that commercial equipment, based on TEV and ultrasonic methods, clearly
demonstrated the capability to identify the presence of PD sources. The UltraTEV Detector™
device by EA Technology was identified as the most versatile in terms of ease to use and clear
indications of PD levels.