Available Sessions

PRESENTED BY
Sanket Bolar
Megger

Power Factor (PF) testing has been a proven method when assessing the quality of insulation systems in transformers and bushings for many years. Single frequency power factor measurements, however, provide only pass/fail criteria and little to no diagnostic information about where the problem of the insulation is and what it might be.

Techniques like Dielectric Frequency Response analysis(DFR) and Narrow Band Frequency Response(NBDFR) have been developed that use information provided by tests performed at different frequencies which allow us to obtain a much better diagnostic analysis of the insulation under evaluation DFR uses mathematical modelling tools to estimate the condition of the insulation system and analyze the solid and liquid parts of the insulation separately. DFR measurements are non-intrusive and provide onsite information about the amount of moisture present in the solid insulation.

The length of the DFR test is dictated by the lower frequency limit which, in turn, depends on the temperature of the transformer. Testing at low temperatures involves longer measurement times.

A shorter version of the DFR test, known as Narrow Band DFR, which uses information from a narrower band of frequencies allows the user to perform a quick triage of the transformer and obtain information as to whether or not the transformer’s insulation needs further evaluation or if it is fit to be put back into service.

NBDFR can be considered as a complementary solution which doesn’t rely on database modelling for moisture assessment.    NBDFR provides valuable information that a traditional line frequency PF may miss due to  power factor’s increased sensitivity to moisture at low frequencies.  

This paper will provide a comparison between DFR and NBDFR as insulation assessment tools on transformers and bushings.  A comparative analysis of the information obtained through wideband DFR  and a narrowband DFR test will be performed.  DFR and NBDFR responses from various transformers and bushings will be shown to help the reader understand, review and differentiate a questionable insulation system from a healthy one. Additional case examples will be provided to highlight the importance of NBDFR as a tool in detecting problems in bushing insulation.

PRESENTED BY
David Morrisey
Asplundh Engineering Services, LLC

PRESENTED BY
Charles Nybeck
Megger

For many years the industry accepted method for evaluating medium and high voltage power cables was DC withstand testing. However, the DC method provided little, if any, diagnostic value and could be destructive to aged cables. New developments in the technology and industry standards have led to new testing techniques utilizing AC voltage that offer more diagnostic value without the risk of damaging aged cable. These methods include Very Low Frequency (VLF) and Tan Delta testing, where each test has its own unique advantages and disadvantages. VLF is performed as a withstand test similar to the DC method, but the test is commonly performed at a frequency of 0.1 Hz. Most industry standards, including the IEEE 400, no longer recommend DC hi-pot testing of XLP and EPR cables. It states that DC hi-pot testing of service-aged XLP and EPR cables may not provide meaningful information and may be destructive. The VLF withstand test can be conducted using sinusoidal or cosine-rectangular (CR) wave forms, where CR is used to mimic cable testing at line frequency during polarity changes. However, by testing in the frequency range of 0.01 to 0.1 Hz as opposed to line frequency, the power requirement is reduced and thus allows the use of a significantly smaller and lighter test device. An alternative, or complementary, diagnostic method is the Tan Delta testing method. Tan Delta, also referred to as Loss Angle or Dissipation Factor, is a diagnostic cable testing method to evaluate the condition of the insulation. The test results provide a “global” assessment into the condition of the cables insulation. Although the Tan Delta method provides a valuable non-destructive testing alternative, there are some disadvantages. For instance, what actions should be made based on questionable test results. While the test itself is simple to perform, in many cases experience and historical data is needed to evaluate test data. This presentation will cover the advantages and disadvantages of VLF and Tan Delta cable testing techniques and how to use these tests as part of a cable maintenance program. In addition, industry standards, field challenges, and best practices for these testing techniques will be discussed, as well as recommendations to produce reliable results for historical trending purposes.

PRESENTED BY
Albert Livshitz
Qualus Power Services

PRESENTED BY
Volney Naranjo
Megger

Bushings are an integral part of transformers, high voltage circuit breakers and other power system assets. Unfortunately, surveys and studies have shown that bushings are also a big contributor to power transformer failures. Any deterioration in the insulation condition of a bushing, especially if not diagnosed at an early stage, can develop rapidly and lead to catastrophic failure of not only the bushing, but also the associated apparatus, and its ancillary devices. Capacitance and Power Factor (PF) measurements are the most common tests conducted on condenser type bushings to assess the condition of the insulation. Performing these measurements requires proper instructions and specific procedures, the operator has to be careful and avoid common mistakes while carrying out the tests as part of a predictive maintenance strategy. Shortcuts or errors in the procedures and measurements can lead to incorrect assessment of the bushing insulation condition, case in which a potential problem can go unnoticed or cause false triggers.

This paper will focus on the best testing practices to follow and the common field errors that the operator should avoid to obtain reliable and repeatable measurements, minimizing any potential and costly user introduced mistakes. Topics such as effect of temperature and humidity, correct handling of capacitance tap for C1 and C2 measurements, best use of hot collar measurements, effective grounding and shorting techniques, utilization of guard circuit to eliminate surface leakage currents, alternative troubleshooting techniques for results validations, trending and analysis of test results and assessment of overall PF measurements with bushing results will be covered. Additionally, the paper will focus on variable frequency based PF testing, a technique also known as Dielectric Frequency Response (DFR), which expands the bushing PF measurements beyond the nominal frequency and provides an advanced diagnostic tool. DFR of bushing can provide a greater insight to the user with the ability to predict the health condition and be proactive in identification of moisture, contamination and losses that may be overlooked in nominal frequency PF testing. The paper will conclude with case examples highlighting the benefits of following best testing practices. It will also provide DFR field results that help in predictive assessment of bushing insulation failure.

PRESENTED BY
Joseph Aguirre
Megger

The correct operation of protection systems is crucial to identify and isolate fault conditions in order to maintain reliability of the power system. While relays are workhorses of these protection systems, the accurate delivery of actuating quantities (voltage and/or current) by voltage and current transformers is indispensable. In metering applications, instrument transformers assume the most significant role as they are used for revenue calculations. It is, hence, imperative to verify the integrity and functionality of such instrument transformers.

Capacitive Voltage Transformers (CVT) are often utilized in power systems to step down high voltage signals to suitable levels, for use by relaying and metering applications. Due to the nature of their application, CVTs are required to fulfill dual responsibilities of accurate signal reproduction and maintaining insulation levels to preclude faults to ground. Consequently, measurement of ratio error, phase angle deviation and polarity are important and so is testing the internal insulation of CVTs. 

This paper will concentrate on testing practices of CVTs, and common challenges experienced to be able to test the different capacitances, the transformation ratio and phase deviation, insulation of the inductive component and overall mechanical condition. Diagnostic testing techniques such as Tip up test and Narrowband dielectric frequency response will be discussed as well as the corresponding analysis of results. 

PRESENTED BY
Mathieu Lachance
OMICRON electronics Canada

Medium voltage (MV) distribution switchgear are a critical part of almost any industrial facilities. Their main functions can include interrupting fault currents, isolating feeders or section of a distribution network and providing metering data to different processes. Because of this, the reliability of those equipment is crucial. Unfortunately, little importance has historically been given to the assessment of the insulation of complete switchgear assemblies during maintenance [1] and at commissioning.

There is only a limited number of published surveys available regarding the causes of failure in MV metal-enclosed distribution switchgear. Probably the most notable example of such survey was published in the appendices of IEEE 493-1997 and dates back from the 1970s. However, some data from a smaller survey performed in 2008 was summarized a few years ago [2] and showed very similar results, at least for the identified causes of failure. In both surveys, approximately 25% of failures were deemed to be caused by partial discharges (PD) for MV switchgear. In addition, in the original survey, approximately 20% of failures were attributed to improper handling or improper installation as the principal root cause.

Conventional partial discharge measurement is a well-established sensitive measurement to detect anomalies during routine tests for almost every medium and high-voltage electrical apparatus. For metal-enclosed switchgear, guidance is provided by IEEE Std C37.301, IEC 62271-200 and CSA C22.2 No. 31-18. However, PD measurements are deemed optional for both IEEE and IEC standard, while it is a stringent requirement for CSA for switchgear that have a rated voltage of 15kV and above. For an unknown reason, the switchgear industry seems to rely mainly on voltage withstand test to assess the insulation of complete switchgear assemblies,

Usually, at the end of the factory tests, the switchgear is disassembled and shipped to site in different sections, where it is reassembled. Once again, the usual test procedures include an insulation resistance test and an AC voltage withstand test. Unfortunately, these will only detect major defects. If PD is present in the switchgear, deterioration will occur at a fast pace in organic insulation systems. Sharp edges from questionable assemblies, subtle damages from transportation and handling in addition to objects left behind such as tools and hardware can create surface and corona discharges. While the former can lead to failure over time, the by-products of corona discharges are corrosive and will deteriorate the switchgear mechanical parts.

This paper presents the results of an experiment that was performed in collaboration with a switchgear manufacturer in order to compare the sensitivity of conventional AC hipot and partial discharge measurements to detect anomalies in complete metal enclosed switchgear assemblies. Common onsite problems were simulated, and the switchgear was tested with both an AC Hipot and a PD measurement. The results are used to expose the advantage of using conventional PD measurement during the onsite commissioning of metal enclosed switchgear.

PRESENTED BY
Will Knapek
OMICRON electronics Corp USA

Current Transformers are in almost every power delivery circuit.  They are often over looked and ignored during maintenance activities.  This presentation will take a look at construction, operation, and tests of current transformers.  The theory of operation and equivalent circuit will be explained.  After attending this presentation you will understand the why of each test that is normally performed on current transformers and how to interpret the results.

PRESENTED BY
Sughosh Kuber
Megger

Directional Elements are at the core of protection schemes design and implementation helping provide secure, selective, and dependable protection systems by supervising and controlling distance and overcurrent elements.

In radial systems, conventional overcurrent relays (51/50) are sufficient to provide adequate protection from faults. However, for network systems like parallel lines or ring bus, directional overcurrent relays (67) are required to provide protection from faults. Due to the nature of these systems, an electrical fault can be seen in either the forward or reverse direction by the protective relay depending on the location of the relay in the system. Directional overcurrent relays use the direction of the power flow to provide the direction to the fault which is determined by the relay using the line impedance angle and the phase relationship between the fault current and a polarizing magnitude which can be a voltage or a current. Since directional overcurrent protection is more selective when compared to non-directional overcurrent it increases the reliability of power supply to critical loads. 

In this paper, different methods used to achieve directional overcurrent protection in electromechanical and microprocessor relays are discussed. Specifically, phase directional relay logic, ground directional relay logic, voltage polarization connections, and the calculations of test values associated with each logic and for different types of faults are discussed. Methods that use symmetrical components to achieve directional protection, in particular negative sequence directional protection, characteristics, and test values calculations are reviewed. Finally, the set of tests that need to be performed for an electromechanical directional relay as well as microprocessor based directional relay are discussed along with the testing procedure for each of those types of relays. Understanding the fundamentals of directional overcurrent protection and implementation of different methods used in directional relays will aid technicians in testing these types of relays efficiently and successfully.

PRESENTED BY
Dinesh Chhajer
Megger

Power Factor (PF) testing has been used for more than 50 years to identify and detect insulation related problems for various electrical assets. PF test when performed correctly provides valuable diagnostic information that can be analyzed and trended throughout the life of the insulation to detect any abnormalities and dielectric failures.

The paper will talk about the best recommended field practices to perform the test effectively and obtain reliable and accurate measurements. It will focus on field aspects that can impact the measurements such as selection of correct test voltage, effect of grounding and guarding, effective measurement of insulation oil temperature and temperature correction of PF readings, position of on load tap changer, effect of humidity and bushing surface contamination, adverse effect of electrostatic interference and noise present in HV stations and most common mistakes associated with measurement of bushing C1 and C2 tests.

The paper will discuss in detail how to analyze the results by correlating other parameters obtained such as leakage current, capacitance and watts loss during PF testing. It will describe in detail what can lead to negative PF values and how external factors and environmental conditions can lead to higher than normal values. Paper will also help user understand what to do when readings don’t make sense and advanced test techniques that could be used to further diagnose and troubleshoot for informed decision making. At the end, it will share the limitations of PF test highlighting what kind of problems it cannot detect and other alternate methods available to supplement PF testing.

The paper will provide users a detailed understanding of what to do and what not to do in the field environment when performing PF testing on HV apparatus. It will complement some of the recommendations through field measurements and case studies to further drive the best field practices.

PRESENTED BY
Robert Otal
METSCO

Through the introduction of online monitoring technologies in the field, including substation monitors capable of providing near-real-time data and readings on power transformers, switchgear and circuit breakers, along with line monitors for overhead conductor and monitors for underground cables, organizations now possess novel opportunities to integrate this data into their asset management frameworks such that decision-making can be enhanced.

This presentation will examine recent efforts to develop Asset Performance Management (APM) frameworks, leveraging available near-real-time data that is being retrieved from online monitoring devices. This presentation will touch upon the emerging field of analytics that can be applied to this data, including machine learning techniques, in order to detect specific signatures within the data that can be correlated to specific failure modes.

Robust APM frameworks are able to leverage this near-real-time data for the purposes of delivering dynamic health index results based upon the newest readings, as well as operational alerts that can detect possible failures that will occur in the next few weeks or months, providing organizations with enough time to take action. For complex substation assets, an APM solution can allow plant managers to manage and mitigate significant risks within their system.

This presentation will also present the results from specific case studies, where near-real-time data from field sensors was successfully leveraged and integrated into an APM such that the organization was able to enhance their risk management and asset management decision-making approaches.

PRESENTED BY
Stephen Hester
Saber Power Field Services, LLC

Safety and profitability both depend on how reliable your equipment is. Reliability is a competitive advantage; the costs resulting from an accident or unplanned downtime caused by poor equipment reliability can hit your company hard and affect your bottom line. Since people and equipment represent a substantial capital investment, it only makes sense to keep your equipment in optimum condition. Maintaining reliability and safety requires proper operation, regular inspection and maintenance to detect problems before they interrupt production. Equipment reliability refers to the activities required to sustain the equipment from commissioning through its life expectancy. While the process can be expensive, the benefits come from increased uptime, sustained production and higher profitability. This presentation will examine the various aspects of reliability management, including how sound preventive and predictive maintenance practices can help you and your customers reduce the risks of failure and maintain a safe operating environment for your employees.

PRESENTED BY
Abel Gonzales
Megger

The condition of the insulation of rotating machines is evaluated by performing high voltage tests typically during manufacturing, commissioning, maintenance, or repairs. These tests are typically referred to as static tests because they are performed while the machine is offline.

High voltage DC tests are used to evaluate the status of the ground wall insulation system with tests such as insulation resistance, polarization index, dielectric absorption ratio, step voltage, and dielectric voltage withstand tests (hipot). Other types of Static tests include application of high voltage AC to verify the dielectric withstand ability of the ground wall insulation or the measurement of the insulation’s power and dissipation factors. AC tests performed at low frequencies, known as VLF tests, are used in some cases to reduce the power requirements of test equipment while still providing accurate representation of the condition of motor insulation.

The paper will discuss the principles behind each of the different static tests used to evaluate the status of the insulation of rotating machines. The evaluation criteria used to determine the pass or fail outcome of each test will be reviewed along with best practices, applicable standards, benefits and challenges of each testing technique.

PRESENTED BY
Tom Sandri
Protec Equipment Resources

This presentation will show attendees how to use data and analytics to support asset management business decisions. Should you rent or purchase equipment? When should you sell used equipment? Learn some of the tools, methods and data points that Protec uses to answer these questions and more.

Learning Objectives:
--Understand tools and software available for asset management
--Learn what Yield and Utilization reports are, how they are created and how to use them for analysis
--Condition assessment and determining BER (Beyond Economic Repair)
--Better budgeting and risk management
--How to use this information to better negotiate with banks, vendors and manufacturers

PRESENTED BY
Karl Jakob and Alan Sbravati
Cargill Bioindustrial-Dielectric Solutions

PRESENTED BY
William Higinbotham
EA Technology, LLC

Partial Discharge Testing is Fun:
-Finding problems before they fail is fun.
-Solving customer problems is fun.
-Being able to diagnose issues without taking equipment out of service is fun.
-Being able to disprove the myths and misconceptions is fun.
But if we want to keep having this fun, we’re going to have to make money at it!
Hopefully this presentation will help.

PRESENTED BY
Charles Nybeck
Megger

Every high voltage (HV) asset in a substation requires an insulation system that is essential to it functioning properly. If the insulation system were to be compromised or fail, the HV asset would have to be taken out of service for expensive repairs or maybe even scrapped. Partial discharge (PD) is one of the first indications of a deteriorating insulation system and is the result of localized electrical stress. There are numerous standards that recommend performing PD testing as a method to find issues in an insulation before it compromises the whole system. This leads to the ability to plan outages around those assets seen with critical levels of PD before they result in faults and unscheduled outages.

Partial discharge emits energy in a number of ways and therefore there are several different methods that can be utilized to detect and quantify this energy. For instance, PD can be measured by use of ultra-high frequency (UHF) sensors, transient earth voltage (TEV) sensors, high frequency current transformers (HFCT), and coupling capacitors (CC). Each of these methods provide PD measurements by different means with advantages and limitations based on the application. Moreover, some of these methods are ideal for PD surveying where the objective is to quickly determine if there is the presence of PD in a substation or HV asset, where other methods provide a more in-depth analysis into the type and severity of PD.

This paper will discuss the fundamentals of PD in high voltage assets, the different methods of measuring PD activity, some advantages and limitations of these measurement methods, which methods apply to certain assets, and relevant standards that discuss PD measurements. It is the objective of this paper to provide a basic understanding of PD and which measurement techniques would best be suited for certain field applications. 

PRESENTED BY
Abel González Gómez
Megger

Induction motors are the workhorse of the modern age and they constitute up to 90% of the installed motor base. Motor protection is very important and when done properly can save companies hundreds of thousands of dollars a year in down time.

Modern motor protection devices can monitor all relevant operational variables like line voltages and currents, frequency, speed, temperature, etc. To configure and implement different sets of protection functions using these variables, adequate knowledge of the operational theory of the machine is required. However, proper design and configuration of the motor protection devices and systems is only the first step when it comes to their correct operation. A systematic approach to testing is equally important to detect design flaws, improper configurations, system reliability, and settings changes as well as device malfunctions or failures The ability to create tests that simulate normal as well as faulted motor operating conditions is key to properly evaluating the behavior of the relay.

In this paper a systematic approach for testing the most common induction motor protection functions, is presented. The protection functions presented in the paper are, current and voltage unbalance, under and over voltage, thermal overload, mechanical jam protection, sensitive ground protection, and motor starting elements. A proper approach to testing each of these different motor protection functions will be shared.  

Since proper testing of protection functions starts with the right understanding of their operation, the reasons behind the existence and the theory of operation of each of the motor protection functions is presented as well as how their settings can be related to the motor’s nameplate information. 
Testing motor protection is a very involved and work-intensive process that can become very complicated if it is not well prepared with basic information to get started as in motor nameplate information, settings files in the relays’ proprietary format, and drawings of the protection scheme for the protective relay under test. As previously mentioned, a review of a typical process will be covered to help outline what a technician might need to do in the field.

PRESENTED BY
Stephen Hester
Saber Power Field Services, LLC

Since the earliest days of the electrical industry both employers and employees have sought to identify electrical hazards and determine the best way to control them. This resulted in a cookie-cutter approach to electrical safety issues where the presence of a hazard resulted in the employment of uniform procedures. The hazard analysis concept has been formalized into a process used throughout the industry. The problem is that a hazard assessment by itself is not sufficient and may result in the selection of inadequate or incorrect control measures. The inclusion of risk in the 2015 edition of the NFPA 70E introduced another way to think about electrical hazard assessments as well as how we should conduct them. There is more to risk management than identifying hazards and choosing personal protective equipment. This paper will discuss the importance of understanding how hazards and risk differ, the importance of properly assessing risk, and the factors that influence our perception of risk.

PRESENTED BY
Justin Palmer and Luke Bendon
GasQuip

PRESENTED BY
Guillermo Falquez
Megger

Protection systems require extensive testing to ensure they operate as intended to protect the power system. Testing protection systems in the real world is a difficult task due to various challenges and situations that you might encounter. Those range from testing for commissioning or maintenance during a shutdown to testing and performing functional checks on equipment in a substation while it is energized. Do you have the substation one-line drawings, or do you have to figure out the connections yourselves? Are you testing a microprocessor relay or an electromechanical relay? Is the substation main locked out and tagged out so that testing can be performed safely? There are a series of questions that need to be answered in order to validate real world protection systems effectively, safely and in a timely manner.

This paper sheds light on various aspects of real-world testing such as challenges faced during testing of specific protection functions, substation one-line drawings, test switches, wiring checks, types of relays used in the implementation of protection schemes, test protocols and requirements, relay settings, testing standards, and safety protocols. Challenges associated with these aspects could differ depending on the type of testing being performed such as commissioning or maintenance testing. Real-world examples for these topics are presented in this paper along with suitable recommendations to overcome those challenges. Finally, a summary is provided that includes tricks and tips that could be beneficial for real-world testing of protection systems. This paper aims to provide a good overview of generic issues faced during real-world testing situations, which will help technicians gain adequate knowledge to handle such situations efficiently.

PRESENTED BY
Jason Aaron
Megger

Transformers in power distribution and transmission substations play a vital role and must function properly in order to avoid equipment damage or costly unscheduled system outages. Various international standards recommend performing several diagnostic tests in order to assess a transformers condition and possibly identify issues before they cause a fault. Several Of these diagnostic tests are designed to determine the condition of the transformer insulation system which plays a vital role by providing the electrical separation between the windings. A compromised insulation system can quickly lead to a transformer failure or even end of life.

One of the first tests used to determine the condition of an insulation system was DC insulation resistance. The insulation resistance test was first possible in the late 1800’s and allowed for the condition assessment of transformer insulation systems. There are several variants to the insulation resistance test, such as the spot test, time-resistance test method, step voltage test, and others that can be utilized for trending a decay in insulation resistance values that may indicate an issue with the insulation system.

Another valuable diagnostic test to assess the condition of transformer insulation systems is power factor at line frequency (PFLF), a standard test for assessment of liquid immersed apparatus. PFLF is a method to determine the overall condition of a transformers insulation system, where an increase in trending results indicates a deteriorating insulation system. Although beneficial, PFLF has limitations such as low sensitivity in the early stages, lack of data, and inaccurate temperature correction that may lead to an incorrect assessment or an inconclusive analysis.

More advanced diagnostic tests, Narrow Band Dielectric Frequency Response (NBDFR) and Dielectric Frequency Response (DFR), can be performed to offer in-depth analysis into a transformer's insulation condition. These techniques expand power factor measurements beyond line frequency, resulting in multiple power factor measurements across a spectrum of frequencies. This paper will discuss in detail transformer insulation testing, ranging from tests such as DC insulation resistance to advanced diagnostic techniques like NBDFR and DFR. It will cover the theory and benefits behind each measurement, as well as relevant standards defining the acceptance criteria used to evaluate test results.

PRESENTED BY
Alex Rangel
Saber Power Field Services, LLC

Large transformers are typically protected primarily by transformer differential protection (87). Although differential protection is outstanding at detecting and clearing internal faults at a fast speed, there are certain power systems conditions that will not be detected by this element. This paper provides the analysis of an event that happened on a 138 kV / 35 kV transformer being fed by solar inverters, in which the neutral connection (X0) was left disconnected by mistake after transformer testing and it caused extensive damage to the lightning arrestors, and how enabling overvoltage (59) protection could have avoided this situation.

PRESENTED BY
Daniel Carreno-Perez
Megger

Transformers are a crucial link in any power  system. When one fails, it can have long lasting ramifications on the power system it is connected to. One of the essential parts of extending the life of a transformer as much as possible, while ensuring proper performance during service, is maintaining its windings in optimal conditions. A full assessment of a transformer windings ’ condition in the field can be done using several  tests. The conductor resistance and connections to the bushings and tap changers can be assessed with winding resistance and transformer turns ratio (TTR); the geometry of the windings is evaluated with capacitance measurements, as well as leakage reactance and sweep frequency response analysis (SFRA); and a comprehensive insulation study can be done using tools such as TTR, excitation current, power factor, insulation resistance, dielectric frequency response (frequency domain spectroscopy), among others.

Understanding how those pieces fit together and how to interpret the data they provide allows to determine the condition of that piece of equipment, as well as to develop a thorough transformer maintenance plan. This paper will focus on understanding the results from the aforementioned tests. Knowing how to interpret individual results, perform trending, and understanding the correlation between these measurements is extremely important, both when assessing the overall condition of the windings as well as troubleshooting issues when unexpected values are obtained.