This guide presents a methodology based on standard PN-IEC 60354 to check overloading capacity of transformers. Main changes versus standard PN-71/E-81000 are discussed and step by step examples are given. An essential advantage of the recommended methods of verification of overloading capacity of transformers is that the size and cooling modes of transformers are considered.
Testing and Condition Monitoring of Substation EquipmentsSumeet Ratnawat
Testing and condition monitoring of substation equipments,Transformer specifications,Monitoring of Transformer,On-load Tap changer,Overhauling,Tan delta and capacitance,Thermal imaging,Sweep frequency response analysis,Oil analysis of Switchgear elements containing oil,tests on insulating oil,Breaker monitoring,Condition monitoring of CT,Condition monitoring of CVT,Surge Arresters,Condition monitoring of relays.
Testing and Condition Monitoring of Substation EquipmentsSumeet Ratnawat
Testing and condition monitoring of substation equipments,Transformer specifications,Monitoring of Transformer,On-load Tap changer,Overhauling,Tan delta and capacitance,Thermal imaging,Sweep frequency response analysis,Oil analysis of Switchgear elements containing oil,tests on insulating oil,Breaker monitoring,Condition monitoring of CT,Condition monitoring of CVT,Surge Arresters,Condition monitoring of relays.
Installation, Testing and Troubleshooting of TransformersLiving Online
This will provide you with practical knowledge (including tips, tricks and tools) covering the fundamentals of power transformers and their testing. It will greatly assist you in communicating more effectively with your electrical engineering colleagues. At the end of this workshop, participants will be familiar with the importance of transformer testing and their purpose, the different kinds of transformer tests and their procedures and the practical applications of principals applied in transformer operation and maintenance.
WHO SHOULD ATTEND?
This workshop will be appropriate for the following professionals:
Electrical engineers
Maintenance engineers
Maintenance supervisors
Power electricians
Power engineers
MORE INFORMATION: http://www.idc-online.com/content/installation-testing-and-troubleshooting-transformers-24
Design of substation (with Transformer Design) SayanSarkar55
This ppt is made for the subject Machine Design. Here the basic types, equipment, designs of substation is described with the preocess and calculation of designing a transformer also.
This directional over current relay employs the principle of actuation of the relay....It has a metallic disc free to rotate between the poles of two...
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.
This Presentation is about l.v switch gear design, presented during the graduation project final discussion 15/7/2018.
It presented a good summary of switch gear components and types and practicing on AL.HAMOOL W.T.P M.D.B design using SIEMENS SIVACON S8
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
Layer-Type Power Transformer Thermal Analysis Considering Effective Parameter...AEIJjournal2
Since large power transformers belong to the most valuable assets in electrical power networks it is
suitable to pay higher attention to these operating resources. Thermal impact leads not only to long-term
oil/paper-insulation degradation; it is also a limiting factor for the transformer operation. Therefore, the
knowledge of the temperature, especially the hottest spot (HST) temperature, is of high interest. This paper
presents steady state temperature distribution of a power transformer layer-type winding using conjugated
heat transfer analysis, therefore energy and Navier-Stokes equations are solved using finite difference
method. Meanwhile, the effects of load conditions and type of oil on HST are investigated using the model.
Oil in the transformer is assumed nearly incompressible and oil parameters such as thermal conductivity,
special heat, viscosity, and density vary with temperature. Comparing the results with those obtained from
finite integral transform checks the validity and accuracy of the proposed method
Installation, Testing and Troubleshooting of TransformersLiving Online
This will provide you with practical knowledge (including tips, tricks and tools) covering the fundamentals of power transformers and their testing. It will greatly assist you in communicating more effectively with your electrical engineering colleagues. At the end of this workshop, participants will be familiar with the importance of transformer testing and their purpose, the different kinds of transformer tests and their procedures and the practical applications of principals applied in transformer operation and maintenance.
WHO SHOULD ATTEND?
This workshop will be appropriate for the following professionals:
Electrical engineers
Maintenance engineers
Maintenance supervisors
Power electricians
Power engineers
MORE INFORMATION: http://www.idc-online.com/content/installation-testing-and-troubleshooting-transformers-24
Design of substation (with Transformer Design) SayanSarkar55
This ppt is made for the subject Machine Design. Here the basic types, equipment, designs of substation is described with the preocess and calculation of designing a transformer also.
This directional over current relay employs the principle of actuation of the relay....It has a metallic disc free to rotate between the poles of two...
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.
This Presentation is about l.v switch gear design, presented during the graduation project final discussion 15/7/2018.
It presented a good summary of switch gear components and types and practicing on AL.HAMOOL W.T.P M.D.B design using SIEMENS SIVACON S8
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
Layer-Type Power Transformer Thermal Analysis Considering Effective Parameter...AEIJjournal2
Since large power transformers belong to the most valuable assets in electrical power networks it is
suitable to pay higher attention to these operating resources. Thermal impact leads not only to long-term
oil/paper-insulation degradation; it is also a limiting factor for the transformer operation. Therefore, the
knowledge of the temperature, especially the hottest spot (HST) temperature, is of high interest. This paper
presents steady state temperature distribution of a power transformer layer-type winding using conjugated
heat transfer analysis, therefore energy and Navier-Stokes equations are solved using finite difference
method. Meanwhile, the effects of load conditions and type of oil on HST are investigated using the model.
Oil in the transformer is assumed nearly incompressible and oil parameters such as thermal conductivity,
special heat, viscosity, and density vary with temperature. Comparing the results with those obtained from
finite integral transform checks the validity and accuracy of the proposed method
Analysis of thermal models to determine the loss of life of mineral oil immer...journalBEEI
Hot spot as well as top oil temperatures have played the most effective parameters on the life of the electrical transformers. The prognostication of these factors is very vital for determining the residual life of the electrical transformers in the transmission and distribution systems. Thus, an accurate mathematical method is required to calculate the critical temperature such as hot spot and top oil temperature based on the different types of thermal models. In this study calculates the service life of the transformers based on an accurate top oil temperature. Accordingly, An approach solution is given for calculating the thermal model. Also, findings are validated with true temperatures. Finally, this method is implemented on 2500 KVA electrical transformer.
Experimental and Analytical Performance of Gas Gap Cryogenic Thermal Switch ...ijsrd.com
Heat switches are important devices in many cryogenic setups, especially in space applications and many systems have been used to allow a good ability to make or break a thermal contact. Among them, the so-called gas gap heat switches are known to be very reliable and simple due to the nonexistence of moving parts. The ON (conducting) state of the switch are obtained by varying the gas pressure and OFF (insulating) are obtained by creating vacuum in gap. In this paper, the gas gap cryogenic thermal switch is fabricated and tested using LN2 storage vessel. The thermal characteristics (Conductance in the ON and OFF state) of a "Gas Gap Heat Switch" are obtained experimentally and analytically using nitrogen as exchange gas. It is concluded that for both ON and OFF state, thermal conductance increases as heat load increases.
An Efficient High Gain DC-DC Converter for Automotive ApplicationsIJPEDS-IAES
This paper presents a high gain DC-DC converter which uses a clamp circuit
to achieve soft switching. The proposed converter is designed to supply a
high intensity discharge (HID) lamp used in automobile head lamps. The
converter operates from a 12V input supply and provides an output voltage
of 120V at 35W output power. A clamp circuit consisting of a clamp
capacitor, clamp switch and resonant inductor will help to achieve zero
voltage switching (ZVS) of the both main and clamp switches. The practical
performance of the converter was validated through experimental results.
Results obtained from the prototype hardware prove that the converter meets
the requirements of HID lamp application and can be a very good alternative
to existing converters.
carnot cycle (a theoretical thermodynamic cycle).pptHafizMudaserAhmad
The Carnot cycle, a theoretical thermodynamic cycle, serves as a fundamental concept in the study of heat engines. Named after the French physicist Sadi Carnot, this cycle provides insight into the maximum efficiency achievable by any heat engine operating between two temperature reservoirs. It consists of four reversible processes: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression. During the isothermal expansion process, the working substance (often a gas) absorbs heat from a high-temperature reservoir, expanding and doing work on the surroundings. The adiabatic expansion follows, during which the gas continues to expand without heat exchange, resulting in a decrease in temperature and pressure. Subsequently, the isothermal compression occurs as the gas is brought into contact with a low-temperature reservoir, releasing heat and contracting. Finally, the adiabatic compression completes the cycle as the gas is compressed without heat exchange, leading to an increase in temperature and pressure. The efficiency of the Carnot cycle depends solely on the temperatures of the reservoirs, with the maximum efficiency achievable when operating between two reversible isothermal processes. Despite being an idealized model, the Carnot cycle provides valuable insights into the principles of thermodynamics and serves as a benchmark for real-world heat engines.
Math cad effective radiation heat transfer coefficient.xmcdJulio Banks
This file demonstrates the use of radiation heat transfer coefficient, the calculation of the heat flux and subsequent heat transfer. The recommendation of estimating the relevance of using radiation heat transfer by comparing the radiation heat transfer coefficient to those of free or forced heat transfer coefficient.
A new generation of instruments and tools to monitor buildings performanceLeonardo ENERGY
What is the added value of monitoring the flexibility, comfort, and well-being of a building? How can occupants be better informed about the performance of their building? And how to optimize a building's maintenance?
The slides were presented during a webinar and roundtable with a focus on a new generation of instruments and tools to monitor buildings' performance, and their link with the Smart Readiness Indicator (SRI) for buildings as introduced in the EU's Energy Performance of Buildings Directive (EPBD).
Link to the recordings: https://youtu.be/ZCFhmldvRA0
Addressing the Energy Efficiency First Principle in a National Energy and Cli...Leonardo ENERGY
When designing energy and climate policies, EU Member States have to apply the Energy Efficiency First Principle: priority should be given to measures reducing energy consumption before other decarbonization interventions are adopted. This webinar summarizes elements of the energy and climate policy of Cyprus illustrating how national authorities have addressed this principle so far, and outline challenges towards its much more rigorous implementation that is required in the coming years.
Auctions for energy efficiency and the experience of renewablesLeonardo ENERGY
Auctions are an emerging market-based policy instrument to promote energy efficiency that has started to gain traction in the EU and worldwide. This presentation provides an overview and comparison of several energy efficiency auctions and derives conclusions on the effects of design elements based on auction theory and on experiences of renewable energy auctions. We include examples from energy efficiency auctions in Brazil, Canada, Germany, Portugal, Switzerland, Taiwan, UK, and US.
A recording of this presentation can be viewed at:
https://youtu.be/aC0h4cXI9Ug
Energy efficiency first – retrofitting the building stock finalLeonardo ENERGY
Retrofitting the building stock is a challenging undertaking in many respects - including costs. Can it nevertheless qualify as a measure under the Energy Efficiency First principle? Which methods can be applied for the assessment and what are the results in terms of the cost-effectiveness of retrofitting the entire residential building stock? How do the results differ for minimization of energy use, CO2 emissions and costs? And which policy conclusions can be drawn?
This presentation was used during the 18th webinar in the Odyssee-Mure on Energy Efficiency Academy on February 3, 2022.
A link to the recording: https://youtu.be/4pw_9hpA_64
How auction design affects the financing of renewable energy projects Leonardo ENERGY
Recording available at https://youtu.be/lPT1o735kOk
Renewable energy auctions might affect the financing of renewable energy (RE) projects. This webinar presents the results of the AURES II project exploring this topic. It discusses how auction designs ranging from bid bonds to penalties and remuneration schemes impact financing and discusses creating a low-risk auction support framework.
This presentation discusses the contribution of Energy Efficiency Funds to the financing of energy efficiency in Europe. The analysis is based on the MURE database on energy efficiency policies. As an example, the German Energy Efficiency Fund is described in more detail.
This is the 17th webinar in the Odyssee-Mure on Energy Efficiency Academy.
Recordings are available on: https://youtu.be/KIewOQCgQWQ
(see updated version of this presentation:
https://www.slideshare.net/sustenergy/energy-efficiency-funds-in-europe-updated)
The Energy Efficiency First Principle is a key pillar of the European Green Deal. A prerequisite for its widespread application is to secure financing for energy efficiency investments.
This presentation discusses the contribution of Energy Efficiency Funds to the financing of energy efficiency in Europe. The analysis is based on the MURE database on energy efficiency policies. As an example, the German Energy Efficiency Fund is described in more detail.
This is the 17th webinar in the Odyssee-Mure on Energy Efficiency Academy.
Recordings are available on: https://youtu.be/KIewOQCgQWQ
Five actions fit for 55: streamlining energy savings calculationsLeonardo ENERGY
During the first year of the H2020 project streamSAVE, multiple activities were organized to support countries in developing savings estimations under Art.3 and Art.7 of the Energy Efficiency Directive (EED).
A fascinating output of the project so far is the “Guidance on Standardized saving methodologies (energy, CO2 and costs)” for a first round of five so-called Priority Actions. This Guidance will assist EU member states in more accurately calculating savings for a set of new energy efficiency actions.
This webinar presents this Guidance and other project findings to the broader community, including industry and markets.
AGENDA
14:00 Introduction to streamSAVE
(Nele Renders, Project Coordinator)
14:10 Views from the EU Commission and the link with Fit-for-55 (Anne-Katherina Weidenbach, DG ENER)
14:20 The streamSAVE guidance and its platform illustrated (Elisabeth Böck, AEA)
14:55 A view from industry: What is the added value of streamSAVE (standardized) methods in frame of the EED (Conor Molloy, AEMS ECOfleet)
14:55 Country experiences: the added value of standardized methods (Elena Allegrini, ENEA, Italy)
The recordings of the webinar can be found on https://youtu.be/eUht10cUK1o
This webinar analyses energy efficiency trends in the EU for the period 2014-2019 and the impact of COVID-19 in 2020 (based on estimates from Enerdata).
The speakers present the overall trend in total energy supply and in final energy consumption, as well as details by sector, alongside macro-economic data. They will explain the main drivers of the variation in energy consumption since 2014 and determine the impact of energy savings.
Speakers:
Laura Sudries, Senior Energy Efficiency Analyst, Enerdata
Bruno Lapillonne, Scientific Director, Enerdata
The recordings of the presentation (webinar) can be viewed at:
https://youtu.be/8RuK5MroTxk
Energy and mobility poverty: Will the Social Climate Fund be enough to delive...Leonardo ENERGY
Prior to the current soaring energy prices across Europe, the European Commission proposed, as part of the FitFor55 climate and energy package, the EU Social Climate Fund to mitigate the expected social impact of extending the EU ETS to transport and heating.
The report presented in this webinar provides an update of the European Energy Poverty Index, published for the first time in 2019, which shows the combined effect of energy and mobility poverty across Member States. Beyond the regular update of the index, the report provides analysis of the existing EU policy framework related to energy and transport poverty. France is used as a case study given the “yellow vest” movement, which was triggered by the proposed carbon tax on fuels.
Watch the recordings of the webinar:
https://youtu.be/i1Jdd3H05t0
Does the EU Emission Trading Scheme ETS Promote Energy Efficiency?Leonardo ENERGY
This policy brief analyzes the main interacting mechanisms between the Energy Efficiency Directive (EED) and the EU Emission Trading Scheme (ETS). It presents a detailed top-down approach, based on the ODYSSEE energy indicators, to identify energy savings from the EU ETS.
The main task consists in isolating those factors that contribute to the change in energy consumption of industrial branches covered by the EU ETS, and the energy transformation sector (mainly the electricity sector).
Speaker:
Wolfgang Eichhammer (Head of the Competence Center Energy Policy and Energy Markets @Fraunhofer Institute for Systems and Innovation Research ISI)
The recordings of this webinar can be watched via:
https://youtu.be/TS6PxIvtaKY
Energy efficiency, structural change and energy savings in the manufacturing ...Leonardo ENERGY
The first part of the presentations presents the energy efficiency improvements in the manufacturing sector since 2000, and the role of structural change between the different branches and energy savings. It will compare the improvements in Denmark and other countries with EU average. This part is based on ODYSSEE data.
The second part of the presentation presents the development in Denmark in more detail, and it will compare the energy efficiency improvement, corrected for structural change, with the reported savings from the Energy Efficiency Obligation Scheme.
Recordings of the live webinar are on https://youtu.be/VVAdw_CS51A
Energy Sufficiency Indicators and Policies (Lea Gynther, Motiva)Leonardo ENERGY
This policy brief looks at questions ‘how to measure energy sufficiency’, ‘which policies and measures can be used to address energy sufficiency’ and ‘how they are used in Europe today’.
Energy sufficiency refers to a situation where everyone has access to the energy services they need, whilst the impacts of the energy system do not exceed environmental limits. The level of ambition needed to address energy sufficiency is higher than in the case of energy efficiency.
This is the 13th edition of the Odyssee-Mure on Energy Efficiency Academy, and number 519 in the Leonardo ENERGY series. The recording of the live presentation can be found on https://www.youtube.com/watch?v=jEAdYbI0wDI&list=PLUFRNkTrB5O_V155aGXfZ4b3R0fvT7sKz
The Super-efficient Equipment and Appliance Deployment (SEAD) Initiative Prod...Leonardo ENERGY
The Super-efficient Equipment and Appliance Deployment (SEAD) Initiative Product Efficiency Call to Action, by Melanie Slade - IEA and Nicholas Jeffrey - UK BEIS
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
Contact with Dawood Bhai Just call on +92322-6382012 and we'll help you. We'll solve all your problems within 12 to 24 hours and with 101% guarantee and with astrology systematic. If you want to take any personal or professional advice then also you can call us on +92322-6382012 , ONLINE LOVE PROBLEM & Other all types of Daily Life Problem's.Then CALL or WHATSAPP us on +92322-6382012 and Get all these problems solutions here by Amil Baba DAWOOD BANGALI
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CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
1. PowerQuality
Guide for electrical design engineers
Katarzyna Strzalka-Goluszka
Doctoral Student of Faculty of Electrical Engineering,
Automatics, IT & Electronics
AGH University of Science & Technology
kstrzalka@op.pl
Power Quality
Overload Capacity of Power
Transformers
Time of day
Loadfactor
t
24 h0
K2
K1
2. Power Quality
2
www.leonardo-energy.org
1. Introduction
For over three decades, since the early seventies, the principles of sizing oil-
immersed transformers and evaluation their overload capacity have been defined
in standard PN-71/E-81000 [1]. These principles are presented in the course
book [3], and examples of practical calculations and transformers sizing are
provided in the course book [4].
The basic criterion adopted in standard [1] for determining power transformers
loading limits is the thermal life of insulation. The standard defines transformer
overload capacity assuming nominal transformer insulation life and reduced
insulation life expectancy corresponding to overloading a transformer under
disturbed conditions.
The basis for consideration in standard [1] was a representative two-step load
cycle determined from the known or expected ordered 24-hour load curve of a
transformer, described by:
• equivalent initial load Sp,
• equivalent final load Sk,
• duration of the final load tk.
The above equivalent load values should be computed as a root mean square
average according to the relation:
(1)
where:
Si – load over the time interval Δti,
Δti – the considered time interval.
The initial and final equivalent loads are determined from the representative load:
(2)
nt
p
p
S
S
K =
nt
k
k
S
S
K =
∑
∑
Δ
Δ
=
i
ii
t
tS
S
2
3. Overload Capacity of PowerTransformers
3
www.leonardo-energy.org
where: Snt – transformer nominal power.
The permissible equivalent final load Kk = f(Kp, tk) is given in standard PN-71/E-
81000 [1] in the form of curves and tables, assuming the following parameters:
• ambient temperature ϑo = - 10, 0, 10, 20 and 30ºC
• equivalent initial load Kp = 0.25÷1.0
• duration of the final load tk = 0.5, 1, 2, 4, 8, 12 and 24h.
Standard PN-IEC 60354 [2] implemented in 1999 considerably alters the
principles of determining the overload capacity of oil-immersed transformers. The
most important changes are discussed further in this paper.
2. Main assumptions of the standard PN-IEC 60354
methodology
The normal service life of transformer is a conventional reference basis for
continuous operation in normal ambient temperature under nominal operating
conditions. Loading beyond nameplate rating and/or higher ambient temperature
involves a risk and results accelerated insulation ageing. Both the loading and
temperature rise above the rated values will result in risk of premature failure of a
transformer that may occur either immediately or after certain time, due to
deterioration of the transformer components. The standard gives guidelines on
transformer loading in relation to the operating temperature rise and thermal
ageing of insulation; the insulation relative ageing rate is assessed using the hot
spot temperature. Since the transformer sensitivity to overloading depends
evidently on its size, the standard specifies three categories of transformers:
• Distribution transformers (with maximum power of 2500 kVA), for which
only the hot-spot temperature and thermal deterioration have to be
considered;
• Medium power transformers (not exceeding 100 MVA), in which the cooling
modes shall be considered;
• Large power transformers (exceeding 100 MVA), where the effects of stray
leakage flux are significant and the consequences of failure are severe.
For each category the standard defines separate requirements.
Table 1 shows limit currents and temperatures for the above transformer
categories, applicable to loading beyond nameplate rating.
4. Power Quality
4
www.leonardo-energy.org
Table 1 : Currents and temperature limits applicable to loading beyond
nameplate rating
As can be seen from table 1, the standard recommendations apply to three types
of transformer loading:
• continuous loading,
• cyclic loading,
• long-time emergency cyclic loading.
Standard [2] provides the method for determining thermal behaviour of
transformers with various cooling modes and comprises computation results in
the form of thermal characteristics for adopted assumptions, among which the
most important are:
• ambient temperature Θa = 20ºC,
• hot-spot temperature rise ΔΘhr = 78ºC.
As the basis for analysis of transformer insulation thermal ageing the rule of 6ºC
is taken, i.e. the rate of insulation ageing doubles for every increment of
approximately 6ºC.
Assuming the relative rate of ageing V at the hot-spot temperature Θh = 98ºC
equals unity V = 1, thus at the temperature Θh = 104ºC V = 2, and at
Θh = 110ºC V = 4.
Standard [2] provides the method for calculation of transformer daily loss-of-
life, expressed in terms of "normal" days, i.e. equivalent days of operation with
rated power at the ambient temperature 20ºC.
TYPE OF LOADING DISTRIBUTION
TRANSFORMERS
MEDIUM POWER
TRANSFORMERS
LARGE POWER
TRANSFORMERS
Normal cyclic load:
Current [p.u.]
Hot-spot temperature [°C]
Top-oil temperature [°C]
1.5
140
105
1.5
140
105
1.3
120
105
Long-time emergency cyclic loading:
Current [p.u.]
Hot-spot temperature [°C]
Top-oil temperature [°C]
1.8
150
115
1.5
140
115
1.3
130
115
Short-time emergency loading:
Current [p.u.]
Hot-spot temperature [°C]
Top-oil temperature [°C]
2.0
-
-
1.8
160
115
1.5
160
115
5. Overload Capacity of PowerTransformers
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3. Method of representing an actual load by an equivalent
two-step load cycle
Fig. 1. Equivalent two-step load cycle
The load steps in figure 1 shall be K1 and K2, where K2 is the peak load. The
duration of the peak load is t hours. Standard [2] describes the method of
determining this duration for different shapes of actual load cycles. In the case
of a load cycle with one peak the value of t should be selected on the equal
areas basis as indicated in Fig. 2. For the off-peak portion of the load cycle, the
value of K1 is selected to correspond to the average off-peak load.
Fig. 2. Load cycle with one peak
In the case where there are two peaks of nearly equal amplitude but different
duration (Fig. 3), the value of time t is determined for the peak of a longer
duration and the value of K1 is selected to correspond to the average of the
remaining daily load.
Time of day
Loadfactor
t
24 h0
K2
K1
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Fig. 3. Load cycle with two peaks of equal amplitude and different duration
For the load cycle where two peaks occur in close succession (Fig. 4), the value
of t is made long enough to enclose both peaks, and K1 is selected accordingly to
the average load during the remaining portion of the day.
Fig. 4. Load cycle with peaks in close succession
4. Determining permissible transformer load for various
types of loadings
For a normal continuous loading, which shows no pronounced variation over
a day, the standard [2] recommends the use of a constant equivalent load
current. Table 2 gives an acceptable load factor K = K24 for continuous duty
and different ambient temperatures.
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Table 2 Acceptable load factor K24 for continuous duty at different ambient
temperatures (ON, OF and OD cooling)
For normal cycling loading and various types of transformers and eight
different ambient temperatures (Θa = -25, -20, -10, 0, 10, 20, 30 and 40°C)
standard PN-IEC 60354: 1999 [2] gives curves that can be used to determine the
permissible peak load K2 for a given duration t and a given initial load K1. If the
ambient temperature value falls between two values, the standard
recommends interpolation between the two nearest curves. Figure 5 shows an
example of relations K2 = f(K1, t) for distribution transformers with ONAN cooling,
and the ambient temperature Θa = +20°C.
Fig. 5. Permissible loading of distribution transformers at the ambient
temperature 20°C
AM BIENT TEM PERATURE, °C -25 -20 -10 0 10 20 30 40
Hot-spot temperature rise, °C 123 118 108 98 88 78 68 58
K24 Distribution
transformers
ONAN 1.37 1.33 1.25 1.17 1.09 1.00 0.91 0.81
Medium and large
power
transformers
ON 1.33 1.30 1.22 1.15 1.08 1.00 0.92 0.82
OF 1.31 1.28 1.21 1.14 1.08 1.00 0.92 0.83
OD 1.24 1.22 1.17 1.11 1.06 1.00 0.94 0.87
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If the supply voltage remains constant the curves K2 = f(K1, t) can also be used
for determining the rated power of a transformer (with normal life duration) for a
given rectangular load profile defined as the ratio K2/K1.
For this purpose it is necessary is to find the intersection of the curve
corresponding to the duration of the load K2 with the line of constant slope K2/K1,
which can be found by marking corresponding points on ordinate K2 = 1 and
abscissa K1 = 1. Figure 1 shows the line for K2/K1 = 1.75, which allows
determining the factors K2 = 1.15 and K1 = 0.66 for duration t = 8h.
For emergency cyclic loading the standard PN-IEC 60354: 1999 [2] gives
tables that can be used to ascertain whether a load characterized by particular
values K1 and K2 is permissible for a given ambient temperature, and
determine a daily loss of life expressed in "normal" days. These tables
correspond to six duration values t (0.5 to 24 h) and four types of transformers.
The below example table 4 determines relative ageing rates V and winding hot-
spot temperature rise ΔΘh for distribution transformers with ONAN cooling and
duration t = 4 h.
Table 3 Conversion factor related to the ambient temperature
In order to determine whether a daily load diagram characterized by particular
values of K1 and K2 is permissible and to evaluate the daily loss of life entailed,
the following steps should be preceded:
- From table 4 find the hot-spot temperature rise ΔΘh and determine the hot-spot
temperature Θh from the formula:
Θh = ΔΘh + Θa (3)
where: Θa - ambient temperature
- If the resulting hot-spot temperature exceeds the limit stated in table 1, the
loading is not permissible.
AMBIENT
TEMPERATURE°C
40°C 30°C 20°C 10°C 0°C -10°C -20°C -25°C
Conversion factor kp 10 3.2 1 0.32 0.1 0.032 0.01 0.0055
9. Overload Capacity of PowerTransformers
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- From table 4 find relative ageing rate V and determine the daily insulation loss
of life L from the formula:
L = V .
kp (4)
where: kp – the conversion factor related to the ambient temperature according to
table 3.
Table 4 relative ageing rate V (daily loss of life) and winding hot-spot
temperature rise Dqh for distribution transformers with ONAN cooling and
duration t = 4 h.
0.25 0.50 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 1.50
0.7 V
Δθh
0.003
43
0.080
46
0.032
48
0.8 V
Δθh
0.005
51
0.012
53
0.040
56
0.093
57
0.9 V
Δθh
0.010
59
0.020
61
0.056
64
0.117
66
0.292
67
1.0 V
Δθh
0.023
68
0.039
70
0.091
73
0.170
74
0.377
76
1.00
78
1.1 V
Δθh
0.056
77
0.091
73
0.178
83
0.294
84
0.566
86
1.32
87
3.72
89
1.2 V
Δθh
0.154
87
0.236
89
0.417
92
0.621
94
1.04
95
2.06
97
5.00
99
14.9
101
1.3 V
Δθh
0.455
98
0.677
100
1.12
103
1.56
104
2.36
106
4.02
108
8.13
110
20.5
112
64.7
114
1.4 V
Δθh
1.45
109
2.11
111
3.36
114
4.50
115
6.38
117
9.76
119
16.8
121
34.7
123
90.6
125
302
127
1.5 V
Δθh
4.94
120
7.09
122
11.00
125
14.4
127
19.7
128
28.2
130
43.7
132
76.1
134
160
137
431
139
1510
141
1.6 V
Δθh
17.9
132
25.5
134
38.8
137
50.1
139
66.8
140
93.7
142
135
144
211
146
371
149
790
151
2200
153
1.7 V
Δθh
69.0
144
97.3
147
146
149
187
151
246
153
334
155
470
157
694
159
110
161
1950
163
4190
166
1.8 V
Δθh
282
157
394
160
587
162
745
164
971
166
1300
167
1790
169
1560
172
3830
174
6110
176
+
179
1.9 V
Δθh
1220
171
1690
173
2500
176
3150
177
4080
179
5410
180
7370
183
+
+
+
+
+
+
+
+
2.0 V
Δθh
5540
184
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
K1
K2
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5. Conclusion
The standard PN-IEC 60354 implemented in 1999, introduced considerable
changes to the principles of assessing thermal effects of transformers
overloading under various types of load. An essential advantage of the
recommended methods of verification of overloading capacity of transformers is
that the size and cooling modes of transformers are considered.
The tables and curves, provided in this standard, being the result of thermal
calculations allow determining permissible loading of transformers under different
operating conditions.
References
[1] PN-71/E-81000 Transformers. Loading of oil-immersed transformers.
[2] IEC 60354: Loading guide for oil immersed transformers.
[3] Strojny J., Strzałka J.: Design of Electric Power Equipment, (in Polish),
SU1609, AGH-UST Publisher, Krakow 2001.
[4] Strzałka J.: Electric Power Equipment ― Problem Book, (in Polish), SU1674,
AGH-UST Publishers Krakow 2005.