Electromechanical relays are an excellent solution to separate electronic control circuitry and power circuitry. Electromechanical relays are not the best choice in high frequency switching applications and do have a limited life due to wear on the contacts inside the relay. When used in the a proper application, the electromechanical relay provides safe and reliable integration between power circuits and control circuits.
A switchgear or electrical switchgear is a generic term which includes all the switching devices associated with mainly power system protection. It also includes all devices associated with control, metering and regulating of electrical power system. Assembly of such devices in a logical manner forms a switchgear. This is the very basic definition of switchgear.
⋗To get more with details
https://www.youtube.com/channel/UC2SvKI7eepP241VLoui1D5A
Electromechanical relays are an excellent solution to separate electronic control circuitry and power circuitry. Electromechanical relays are not the best choice in high frequency switching applications and do have a limited life due to wear on the contacts inside the relay. When used in the a proper application, the electromechanical relay provides safe and reliable integration between power circuits and control circuits.
A switchgear or electrical switchgear is a generic term which includes all the switching devices associated with mainly power system protection. It also includes all devices associated with control, metering and regulating of electrical power system. Assembly of such devices in a logical manner forms a switchgear. This is the very basic definition of switchgear.
⋗To get more with details
https://www.youtube.com/channel/UC2SvKI7eepP241VLoui1D5A
Protection of transmission lines (distance)Rohini Haridas
This gives idea about necessity of protection of transmission line and protection based on time grading as well as on current grading. Also includes three step distance protection of transmission line
Power System protection and Metering,Types of Faults and effects,Symmetrical faults,Unsymmetrical faults,Fault Statics,Components of power System protection,Relay,Classification of Relay,Induction relay,thermal relay,Static Relay,Numerical Relay
EDS Unit 4 (Protection and Coordination).pptxDr. Rohit Babu
Protection:
Objectives of distribution system protection
Types of common faults and procedure for fault calculations
Protective devices: Principle of operation of fuses Circuit reclosures
Line sectionalizes and circuit breakers.
Coordination:
Coordination of protective devices: General coordination procedure
Residual current circuit breaker RCCB (Wikipedia).
An inverter is an electric apparatus that changes direct current (DC) to alternating current (AC). It is not the same thing as an alternator, which converts mechanical energy(e.g. movement) into alternating current.
Direct current is created by devices such as batteries and solar panels. When connected, an inverter allows these devices to provide electric power for small household devices. The inverter does this through a complex process of electrical adjustment. From this process, AC electric power is produced. This form of electricity can be used to power an electric light, a microwave oven, or some other electric machine.
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...
Protection of transmission lines (distance)Rohini Haridas
This gives idea about necessity of protection of transmission line and protection based on time grading as well as on current grading. Also includes three step distance protection of transmission line
Power System protection and Metering,Types of Faults and effects,Symmetrical faults,Unsymmetrical faults,Fault Statics,Components of power System protection,Relay,Classification of Relay,Induction relay,thermal relay,Static Relay,Numerical Relay
EDS Unit 4 (Protection and Coordination).pptxDr. Rohit Babu
Protection:
Objectives of distribution system protection
Types of common faults and procedure for fault calculations
Protective devices: Principle of operation of fuses Circuit reclosures
Line sectionalizes and circuit breakers.
Coordination:
Coordination of protective devices: General coordination procedure
Residual current circuit breaker RCCB (Wikipedia).
An inverter is an electric apparatus that changes direct current (DC) to alternating current (AC). It is not the same thing as an alternator, which converts mechanical energy(e.g. movement) into alternating current.
Direct current is created by devices such as batteries and solar panels. When connected, an inverter allows these devices to provide electric power for small household devices. The inverter does this through a complex process of electrical adjustment. From this process, AC electric power is produced. This form of electricity can be used to power an electric light, a microwave oven, or some other electric machine.
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...
Digital isolation plays a key role in designing industrial motor control systems. This presentation takes you through why, where and how for isolation designs that optimize system performance while meeting the ever stringent safety and efficient standards. Analog Devices, Nicola O'Byrne at PCIM 2015
Webinar: Fontes chaveadas digitais inteligentes com USB-PDEmbarcados
Simplificando a nova geração de fontes chaveadas com controlador ST-ONE e MasterGAN, propiciando: aumento de eficiência, evitando o uso de dissipadores de calor, implementando retificação síncrona / protocolo USB-PD e reduzindo o BOM da solução.
O crescimento do mercado de fontes chaveadas e conversores em geral tem aumento drasticamente ano a ano. Desta forma o uso racional e eficiente da energia disponível é fundamental, em muitos mercados níveis de eficiência mínimos já são mandatórios. Para atendermos esta demanda, a STMicrolectronics disponibiliza ao mercado o novo controlador digital ST-ONE para fontes chaveadas na topologia ACF “Active Clamp Flyback” possibilitando um controle inteligente para minimizar perdas nas chaves de potência. Somado a este controlador temos no estágio de potência nosso SiP “System-In-Package” baseado na tecnologia GaN que é nossa família MasterGAN. Este conjunto controlador digital inteligente com chaves GaN possibilita um aumento significativo da densidade de potência, redução das perdas e das temperaturas na fonte chaveada, trazendo confiabilidade e incrível redução no espaço necessário para implementação de uma fonte chaveada.
Siemens,
Catalog Thiết Bị Điện Siemens, Catalog Thiết Bị Điện,
Catalog Phụ Kiện Siemens, Catalog Phụ Kiện,
Catalog Siemens, Catalog,
http://dienhathe.com,
Chi tiết các sản phẩm khác của Siemens tại https://dienhathe.com
Xem thêm các Catalog khác của Siemens tại https://dienhathe.info
Để nhận báo giá sản phẩm Siemens vui lòng gọi: 0907.764.966
The project is designed to control the speed of a single phase induction motor in three steps by using cyclo convertor technique by thyristors. A.C. motors have the great advantages of being relatively inexpensive and very reliable.
Catalog thiết bị đóng cắt Fuji Electric - 07 - ELCB
*********************************************************************
CTY TNHH HẠO PHƯƠNG - Nhà phân phối chính thức các thiết bị điện công nghiệp và tự động hóa của hãng FUJI ELECTRIC JAPAN tại Việt Nam
Xem chi tiết các sản phẩm Fuji Electric tại
http://haophuong.com/b1033533/fuji-electric
The UNO-2.0-I and UNO-2.5-I are the latest single phase string inverters in the line. A new-look inverter but packed with ABB’s proven high performing technology. The new look inverter has new features including a special built-in heat sink compartment and front panel display system.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
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/
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Hybrid optimization of pumped hydro system and solar- Engr. Abdul-Azeez.pdffxintegritypublishin
Advancements in technology unveil a myriad of electrical and electronic breakthroughs geared towards efficiently harnessing limited resources to meet human energy demands. The optimization of hybrid solar PV panels and pumped hydro energy supply systems plays a pivotal role in utilizing natural resources effectively. This initiative not only benefits humanity but also fosters environmental sustainability. The study investigated the design optimization of these hybrid systems, focusing on understanding solar radiation patterns, identifying geographical influences on solar radiation, formulating a mathematical model for system optimization, and determining the optimal configuration of PV panels and pumped hydro storage. Through a comparative analysis approach and eight weeks of data collection, the study addressed key research questions related to solar radiation patterns and optimal system design. The findings highlighted regions with heightened solar radiation levels, showcasing substantial potential for power generation and emphasizing the system's efficiency. Optimizing system design significantly boosted power generation, promoted renewable energy utilization, and enhanced energy storage capacity. The study underscored the benefits of optimizing hybrid solar PV panels and pumped hydro energy supply systems for sustainable energy usage. Optimizing the design of solar PV panels and pumped hydro energy supply systems as examined across diverse climatic conditions in a developing country, not only enhances power generation but also improves the integration of renewable energy sources and boosts energy storage capacities, particularly beneficial for less economically prosperous regions. Additionally, the study provides valuable insights for advancing energy research in economically viable areas. Recommendations included conducting site-specific assessments, utilizing advanced modeling tools, implementing regular maintenance protocols, and enhancing communication among system components.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
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.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
2. 2
GE Consumer & Industrial
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Outline
• Bus arrangements
• Bus components
• Bus protection techniques
• CT Saturation
• Application Considerations:
High impedance bus differential relaying
Low impedance bus differential relaying
Special topics
3. 3
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1 2 3 n-1 n
ZONE 1
- - - -
• Distribution and lower transmission voltage levels
• No operating flexibility
• Fault on the bus trips all circuit breakers
Single bus - single breaker
4. 4
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ZONE 1
ZONE 2
• Distribution and lower transmission voltage levels
• Limited operating flexibility
Multiple bus sections - single breaker with
bus tie
5. 5
GE Consumer & Industrial
Multilin
29-Oct-22
ZONE 1
ZONE 2
• Transmission and distribution voltage levels
• Breaker maintenance without circuit removal
• Fault on a bus disconnects only the circuits being connected
to that bus
Double bus - single breaker with bus tie
6. 6
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ZONE 1
MAIN BUS
TRANFER BUS
• Increased operating flexibility
• A bus fault requires tripping all breakers
• Transfer bus for breaker maintenance
Main and transfer buses
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ZONE 1
ZONE 2
• Very high operating flexibility
• Transfer bus for breaker maintenance
Double bus – single breaker w/ transfer bus
8. 8
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Multilin
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ZONE 1
ZONE 2
• High operating flexibility
• Line protection covers bus section between two CTs
• Fault on a bus does not disturb the power to circuits
Double bus - double breaker
9. 9
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ZONE 1
ZONE 2
• Used on higher voltage levels
• More operating flexibility
• Requires more breakers
• Middle bus sections covered by line or other equipment
protection
Breaker-and-a-half bus
10. 10
GE Consumer & Industrial
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29-Oct-22
• Higher voltage levels
• High operating flexibility with minimum breakers
• Separate bus protection not required at line positions
B1 B2
TB1
L1 L2
L3 L4
TB1
Ring bus
11. 11
GE Consumer & Industrial
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29-Oct-22
Bus components breakers
SF6, EHV & HV - Synchropuff
Low Voltage circuit breakers
BUS 2
CB 1
BUS 1
ISO 1 ISO 2
ISO 3
BYPASS
12. 12
GE Consumer & Industrial
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-
+
F1a
F1c
Contact Input F1a On
Contact Input F1c On
F1b
ISOLATOR
1
ISOLATOR 1 OPEN
7B 7A
BUS 1
-
+
F1a
F1c
Contact Input F1a On
Contact Input F1c On
F1b
ISOLATOR
1
ISOLATOR 1 CLOSED
7B 7A
BUS 1
Disconnect switches & auxiliary contacts
BUS 2
CB 1
BUS 1
ISO 1 ISO 2
ISO 3
BYPASS
13. 13
GE Consumer & Industrial
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BUS 2
CB 1
BUS 1
ISO 1 ISO 2
ISO 3
BYPASS
Current Transformers
Oil insulated current transformer
(35kV up to 800kV)
Gas (SF6) insulated current
transformer
Bushing type (medium
voltage switchgear)
14. 14
GE Consumer & Industrial
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Protection Requirements
High bus fault currents due to large number of circuits
connected:
• CT saturation often becomes a problem as CTs may not be sufficiently
rated for worst fault condition case
• large dynamic forces associated with bus faults require fast clearing
times in order to reduce equipment damage
False trip by bus protection may create serious problems:
• service interruption to a large number of circuits (distribution and sub-
transmission voltage levels)
• system-wide stability problems (transmission voltage levels)
With both dependability and security important, preference is
always given to security
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GE Consumer & Industrial
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Bus Protection Techniques
• Interlocking schemes
• Overcurrent (“unrestrained” or “unbiased”)
differential
• Overcurrent percent (“restrained” or “biased”)
differential
• Linear couplers
• High-impedance bus differential schemes
• Low-impedance bus differential schemes
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Interlocking Schemes
• Blocking scheme typically
used
• Short coordination time
required
• Care must be taken with
possible saturation of feeder
CTs
• Blocking signal could be sent
over communications ports
(peer-to-peer)
• This technique is limited to
simple one-incomer
distribution buses
50
50 50 50 50 50
BLOCK
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GE Consumer & Industrial
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Overcurrent (unrestrained) Differential
• Differential signal formed by
summation of all currents feeding
the bus
• CT ratio matching may be
required
• On external faults, saturated CTs
yield spurious differential current
• Time delay used to cope with CT
saturation
• Instantaneous differential OC
function useful on integrated
microprocessor-based relays
51
18. 18
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59
Linear Couplers
ZC = 2 – 20 - typical coil impedance
(5V per 1000Amps => 0.005 @ 60Hz )
If = 8000 A
40 V 10 V 10 V 0 V 20 V
2000 A 2000 A 4000 A
0 A
0 V
External
Fault
19. 19
GE Consumer & Industrial
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59
Linear Couplers
Esec= Iprim*Xm - secondary voltage on relay terminals
IR= Iprim*Xm /(ZR+ZC) – minimum operating current
where,
Iprim – primary current in each circuit
Xm – liner coupler mutual reactance (5V per 1000Amps => 0.005 @ 60Hz )
ZR – relay tap impedance
ZC – sum of all linear coupler self impedances
If = 8000 A
0 A
0 V 10 V 10 V 0 V 20 V
40 V
2000 A 2000 A 4000 A
0 A
Internal Bus
Fault
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• Fast, secure and proven
• Require dedicated air gap CTs, which may not be used for
any other protection
• Cannot be easily applied to reconfigurable buses
• The scheme uses a simple voltage detector – it does not
provide benefits of a microprocessor-based relay (e.g.
oscillography, breaker failure protection, other functions)
Linear Couplers
21. 21
GE Consumer & Industrial
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29-Oct-22
High Impedance Differential
• Operating signal created by
connecting all CT secondaries in
parallel
o CTs must all have the same ratio
o Must have dedicated CTs
• Overvoltage element operates on
voltage developed across resistor
connected in secondary circuit
o Requires varistors or AC shorting
relays to limit energy during faults
• Accuracy dependent on secondary
circuit resistance
o Usually requires larger CT cables to
reduce errors higher cost
Cannot easily be applied to reconfigurable buses and
offers no advanced functionality
59
22. 22
GE Consumer & Industrial
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Percent Differential
• Percent characteristic used
to cope with CT saturation
and other errors
• Restraining signal can be
formed in a number of
ways
• No dedicated CTs needed
• Used for protection of re-
configurable buses
possible
51
87
n
DIF I
I
I
I
...
2
1
n
RES I
I
I
I
...
2
1
n
RES I
I
I
I ...,
,
,
max 2
1
23. 23
GE Consumer & Industrial
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29-Oct-22
Low Impedance Percent Differential
• Individual currents sampled by protection and summated digitally
o CT ratio matching done internally (no auxiliary CTs)
o Dedicated CTs not necessary
• Additional algorithms improve security of percent differential
characteristic during CT saturation
• Dynamic bus replica allows application to reconfigurable buses
o Done digitally with logic to add/remove current inputs from differential
computation
o Switching of CT secondary circuits not required
• Low secondary burdens
• Additional functionality available
o Digital oscillography and monitoring of each circuit connected to bus zone
o Time-stamped event recording
o Breaker failure protection
24. 24
GE Consumer & Industrial
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29-Oct-22
Digital Differential Algorithm Goals
• Improve the main differential algorithm operation
o Better filtering
o Faster response
o Better restraint techniques
o Switching transient blocking
• Provide dynamic bus replica for reconfigurable bus bars
• Dependably detect CT saturation in a fast and reliable manner,
especially for external faults
• Implement additional security to the main differential algorithm to
prevent incorrect operation
o External faults with CT saturation
o CT secondary circuit trouble (e.g. short circuits)
25. 25
GE Consumer & Industrial
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29-Oct-22
Low Impedance Differential (Distributed)
• Data Acquisition Units (DAUs)
installed in bays
• Central Processing Unit (CPU)
processes all data from DAUs
• Communications between DAUs
and CPU over fiber using
proprietary protocol
• Sampling synchronisation
between DAUs is required
• Perceived less reliable (more
hardware needed)
• Difficult to apply in retrofit
applications
52
DAU
52
DAU
52
DAU
CU
copper
fiber
26. 26
GE Consumer & Industrial
Multilin
29-Oct-22
Low Impedance Differential (Centralized)
• All currents applied to a single
central processor
• No communications, external
sampling synchronisation
necessary
• Perceived more reliable (less
hardware needed)
• Well suited to both new and
retrofit applications.
52 52 52
CU
copper
28. 28
GE Consumer & Industrial
Multilin
29-Oct-22
CT Saturation Concepts
• CT saturation depends on a number of factors
o Physical CT characteristics (size, rating, winding resistance,
saturation voltage)
o Connected CT secondary burden (wires + relays)
o Primary current magnitude, DC offset (system X/R)
o Residual flux in CT core
• Actual CT secondary currents may not behave in the same manner as
the ratio (scaled primary) current during faults
• End result is spurious differential current appearing in the summation
of the secondary currents which may cause differential elements to
operate if additional security is not applied
29. 29
GE Consumer & Industrial
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CT Saturation
Ratio Current CT Current
Ratio Current CT Current
No DC Offset
• Waveform remains fairly
symmetrical
With DC Offset
• Waveform starts off being
asymmetrical, then
symmetrical in steady
state
30. 30
GE Consumer & Industrial
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29-Oct-22
External Fault & Ideal CTs
• Fault starts at t0
• Steady-state fault conditions occur at t1
differential
restraining
t0
t1
Ideal CTs have no saturation or mismatch errors thus
produce no differential current
31. 31
GE Consumer & Industrial
Multilin
29-Oct-22
External Fault & Actual CTs
• Fault starts at t0
• Steady-state fault conditions occur at t1
differential
restraining
t0
t1
Actual CTs do introduce errors, producing some differential
current (without CT saturation)
32. 32
GE Consumer & Industrial
Multilin
29-Oct-22
External Fault with CT Saturation
• Fault starts at t0, CT begins to saturate at t1
• CT fully saturated at t2
differential
restraining
t0
t1
t2
CT saturation causes increasing differential current that
may enter the differential element operate region.
33. 33
GE Consumer & Industrial
Multilin
29-Oct-22
Some Methods of Securing Bus Differential
• Block the bus differential for a period of time (intentional delay)
o Increases security as bus zone will not trip when CT saturation is present
o Prevents high-speed clearance for internal faults with CT saturation or
evolving faults
• Change settings of the percent differential characteristic (usually Slope 2)
o Improves security of differential element by increasing the amount of
spurious differential current needed to incorrectly trip
o Difficult to explicitly develop settings (Is 60% slope enough? Should it be
75%?)
• Apply directional (phase comparison) supervision
o Improves security by requiring all currents flow into the bus zone before
asserting the differential element
o Easy to implement and test
o Stable even under severe CT saturation during external faults
34. 34
GE Consumer & Industrial
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29-Oct-22
High-Impedance
Bus Differential
Considerations
35. 35
GE Consumer & Industrial
Multilin
29-Oct-22
High Impedance Voltage-operated Relay
External Fault
• 59 element set above max possible voltage developed across
relay during external fault causing worst case CT saturation
• For internal faults, extremely high voltages (well above 59
element pickup) will develop across relay
36. 36
GE Consumer & Industrial
Multilin
29-Oct-22
High Impedance Voltage Operated Relay
Ratio matching with Multi-ratio CTs
• Application of high impedance differential relays with CTs of
different ratios but ratio matching taps is possible, but could
lead to voltage magnification.
• Voltage developed across full winding of tapped CT does not
exceed CT rating, terminal blocks, etc.
37. 37
GE Consumer & Industrial
Multilin
29-Oct-22
High Impedance Voltage Operated Relay
Ratio matching with Multi-ratio CTs
• Use of auxiliary CTs to obtain correct ratio matching is also
possible, but these CTs must be able to deliver enough voltage
necessary to produce relay operation for internal faults.
38. 38
GE Consumer & Industrial
Multilin
29-Oct-22
Electromechanical High Impedance Bus
Differential Relays
• Single phase relays
• High-speed
• High impedance voltage sensing
• High seismic IOC unit
39. 39
GE Consumer & Industrial
Multilin
29-Oct-22
Operating time: 20 – 30ms @ I > 1.5xPKP
P -based High-Impedance Bus Differential
Protection Relays
40. 40
GE Consumer & Industrial
Multilin
29-Oct-22
RST = 2000 - stabilizing resistor to limit the current
through the relay, and force it to the lower impedance CT
windings.
MOV – Metal Oxide Varistor to limit the voltage to
1900 Volts
86 – latching contact preventing the resistors from
overheating after the fault is detected
High Impedance Module for Digital
Relays
42. 42
GE Consumer & Industrial
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29-Oct-22
• Fast, secure and proven
• Requires dedicated CTs, preferably with the same CT ratio
and using full tap
• Can be applied to small buses
• Depending on bus internal and external fault currents, high
impedance bus diff may not provide adequate settings for
both sensitivity and security
• Cannot be easily applied to reconfigurable buses
• Require voltage limiting varistor capable of absorbing
significant energy
• May require auxiliary CTs
• Do not provide full benefits of microprocessor-based relay
system (e.g. metering, monitoring, oscillography, etc.)
High Impedance Bus Protection - Summary
43. 43
GE Consumer & Industrial
Multilin
29-Oct-22
Low-Impedance
Bus Differential
Considerations
44. 44
GE Consumer & Industrial
Multilin
29-Oct-22
P-based Low-Impedance Relays
• No need for dedicated CTs
• Internal CT ratio mismatch compensation
• Advanced algorithms supplement percent differential
protection function making the relay very secure
• Dynamic bus replica (bus image) principle is used in
protection of reconfigurable bus bars, eliminating the need
for switching physically secondary current circuits
• Integrated Breaker Failure (BF) function can provide
optimal tripping strategy depending on the actual
configuration of a bus bar
45. 45
GE Consumer & Industrial
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29-Oct-22
• Up to 24 Current Inputs
• 4 Zones
• Zone 1 = Phase A
• Zone 2 = Phase B
• Zone 3 = Phase C
• Zone 4 = Not used
• Different CT Ratio Capability for
Each Circuit
• Largest CT Primary is Base in
Relay
2-8 Circuit Applications
Small Bus Applications
46. 46
GE Consumer & Industrial
Multilin
29-Oct-22
• Relay 1 - 24 Current Inputs
• 4 Zones
• Zone 1 = Phase A (12 currents)
• Zone 2 = Phase B (12 currents)
• Zone 3 = Not used
• Zone 4 = Not used
CB 12
CB 11
• Different CT Ratio Capability for Each Circuit
• Largest CT Primary is Base in Relay
• Relay 2 - 24 Current Inputs
• 4 Zones
• Zone 1 = Not used
• Zone 2 = Not used
• Zone 3 = Phase C (12 currents)
• Zone 4 = Not used
9-12 Circuit Applications
Medium to Large Bus Applications
47. 47
GE Consumer & Industrial
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29-Oct-22
Large Bus Applications
87B phase A
87B phase B
87B phase C
Logic relay
(switch status,
optional BF)
48. 48
GE Consumer & Industrial
Multilin
29-Oct-22
Large Bus Applications
For buses with up to 24 circuits
49. 49
GE Consumer & Industrial
Multilin
29-Oct-22
Summing External Currents
Not Recommended for Low-Z 87B relays
• Relay becomes combination
of restrained and unrestrained
elements
•In order to parallel CTs:
• CT performance must be closely
matched
o Any errors will appear as
differential currents
• Associated feeders must be radial
o No backfeeds possible
• Pickup setting must be raised to
accommodate any errors
CT-1
CT-2
CT-3
CT-4
I
3
=
0
I
2
=
0
I
1
=
Error
IDIFF
= Error
IREST
= Error
Maloperation if
Error > PICKUP
50. 50
GE Consumer & Industrial
Multilin
29-Oct-22
Definitions of Restraint Signals
“maximum of”
“geometrical average”
“scaled sum of”
“sum of”
n
R i
i
i
i
i
...
3
2
1
n
R i
i
i
i
n
i
...
1
3
2
1
n
R i
i
i
i
Max
i ,...,
,
, 3
2
1
n
n
R i
i
i
i
i
...
3
2
1
51. 51
GE Consumer & Industrial
Multilin
29-Oct-22
“Sum Of” vs. “Max Of” Restraint Methods
“Sum Of” Approach
• More restraint on external faults;
less sensitive for internal faults
• “Scaled-Sum Of” approach takes
into account number of connected
circuits and may increase
sensitivity
• Breakpoint settings for the percent
differential characteristic more
difficult to set
“Max Of” Approach
• Less restraint on external faults;
more sensitive for internal faults
• Breakpoint settings for the percent
differential characteristic easier to
set
• Better handles situation where one
CT may saturate completely (99%
slope settings possible)
52. 52
GE Consumer & Industrial
Multilin
29-Oct-22
Bus Differential Adaptive Approach
differential
restraining
Region 1
(low differential
currents)
Region 2
(high differential
currents)
53. 53
GE Consumer & Industrial
Multilin
29-Oct-22
Bus Differential Adaptive Logic Diagram
DIFL
DIR
SAT
DIFH
OR
AND
OR
87B BIASED OP
AND
54. 54
GE Consumer & Industrial
Multilin
29-Oct-22
Phase Comparison Principle
• Internal Faults: All fault (“large”) currents are approximately in
phase.
• External Faults: One fault (“large”) current will be out of phase
• No Voltages are required or needed
Secondary Current of
Faulted Circuit
(Severe CT Saturation)
55. 55
GE Consumer & Industrial
Multilin
29-Oct-22
Phase Comparison Principle Continued…
BLOCK
OPERATE
BLOCK
p
D
p
I
I
I
real
p
D
p
I
I
I
imag
Ip
ID - Ip
External Fault Conditions
OPERATE
BLOCK
BLOCK
p
D
p
I
I
I
real
p
D
p
I
I
I
imag
Ip
ID - Ip
Internal Fault Conditions
OPERATE
OPERATE
56. 56
GE Consumer & Industrial
Multilin
29-Oct-22
CT Saturation
• Fault starts at t0, CT begins to saturate at t1
• CT fully saturated at t2
differential
restraining
t0
t1
t2
57. 57
GE Consumer & Industrial
Multilin
29-Oct-22
CT Saturation Detector State Machine
NORMAL
SAT := 0
EXTERNAL
FAULT
SAT := 1
EXTERNAL
FAULT & CT
SATURATION
SAT := 1
The differential
characteristic
entered
The differential-
restraining trajectory
out of the differential
characteristic for
certain period of time
saturation
condition
The differential
current below the
first slope for
certain period of
time
58. 58
GE Consumer & Industrial
Multilin
29-Oct-22
CT Saturation Detector Operating
Principles
• The 87B SAT flag WILL NOT be set during internal faults,
regardless of whether or not any of the CTs saturate.
• The 87B SAT flag WILL be set during external faults,
regardless of whether or not any of the CTs saturate.
• By design, the 87B SAT flag WILL force the relay to use
the additional 87B DIR phase comparison for Region 2
The Saturation Detector WILL NOT Block the Operation of
the Differential Element – it will only Force 2-out-of-2
Operation
59. 59
GE Consumer & Industrial
Multilin
29-Oct-22
CT Saturation Detector - Examples
• The oscillography records on the next two slides were captured from a
B30 relay under test on a real-time digital power system simulator
• First slide shows an external fault with deep CT saturation (~1.5 msec of
good CT performance)
o SAT saturation detector flag asserts prior to BIASED PKP bus
differential pickup
o DIR directional flag does not assert (one current flows out of zone),
so even though bus differential picks up, no trip results
• Second slide shows an internal fault with mild CT saturation
o BIASED PKP and BIASED OP both assert before DIR asserts
o CT saturation does not block bus differential
• More examples available (COMTRADE files) upon request
60. 60
GE Consumer & Industrial
Multilin
29-Oct-22
The bus differential
protection element
picks up due to heavy
CT saturation
The CT saturation flag
is set safely before the
pickup flag
The
directional flag
is not set
The element
does not
maloperate
Despite heavy CT
saturation the
external fault current
is seen in the
opposite direction
CT Saturation Example – External Fault
0.06 0.07 0.08 0.09 0.1 0.11 0.12
-200
-150
-100
-50
0
50
100
150
200
time, sec
current,
A
~1 ms
61. 61
GE Consumer & Industrial
Multilin
29-Oct-22
The bus differential
protection element
picks up
The saturation
flag is not set - no
directional
decision required
The element
operates in
10ms
The
directional
flag is set
All the fault currents
are seen in one
direction
CT Saturation – Internal Fault Example
62. 62
GE Consumer & Industrial
Multilin
29-Oct-22
Applying Low-Impedance Differential
Relays for Busbar Protection
Basic Topics
• Configure physical CT Inputs
• Configure Bus Zone and Dynamic Bus Replica
• Calculating Bus Differential Element settings
Advanced Topics
• Isolator switch monitoring for reconfigurable buses
• Differential Zone CT Trouble
• Integrated Breaker Failure protection
63. 63
GE Consumer & Industrial
Multilin
29-Oct-22
Configuring CT Inputs
• For each connected CT circuit enter Primary rating and
select Secondary rating.
• Each 3-phase bank of CT inputs must be assigned to a
Signal Source that is used to define the Bus Zone and
Dynamic Bus Replica
Some relays define 1 p.u. as the maximum
primary current of all of the CTs connected in the
given Bus Zone
64. 64
GE Consumer & Industrial
Multilin
29-Oct-22
Per-Unit Current Definition - Example
Current
Channel
Primary Secondary Zone
CT-1 F1 3200 A 1 A 1
CT-2 F2 2400 A 5 A 1
CT-3 F3 1200 A 1 A 1
CT-4 F4 3200 A 1 A 2
CT-5 F5 1200 A 5 A 2
CT-6 F6 5000 A 5 A 2
• For Zone 1, 1 p.u. = 3200 AP
• For Zone 2, 1 p.u. = 5000 AP
65. 65
GE Consumer & Industrial
Multilin
29-Oct-22
Configuration of Bus Zone
• Dynamic Bus Replica associates a status signal with each
current in the Bus Differential Zone
• Status signal can be any logic operand
o Status signals can be developed in programmable logic
to provide additional checks or security as required
o Status signal can be set to ‘ON’ if current is always in the
bus zone or ‘OFF’ if current is never in the bus zone
• CT connections/polarities for a particular bus zone must be
properly configured in the relay, via either hardwire or
software
66. 66
GE Consumer & Industrial
Multilin
29-Oct-22
Configuring the Bus Differential Zone
1. Configure the physical CT Inputs
o CT Primary and Secondary values
o Both 5 A and 1 A inputs are supported by the UR hardware
o Ratio compensation done automatically for CT ratio differences up to 32:1
2. Configure AC Signal Sources
3. Configure Bus Zone with Dynamic Bus Replica
Bus Zone settings defines the boundaries of the Differential
Protection and CT Trouble Monitoring.
67. 67
GE Consumer & Industrial
Multilin
29-Oct-22
Dual Percent Differential Characteristic
High
Breakpoint
Low
Breakpoint
Low Slope
High Slope
High Set
(Unrestrained)
Min Pickup
68. 68
GE Consumer & Industrial
Multilin
29-Oct-22
Calculating Bus Differential Settings
• The following Bus Zone Differential element parameters need to be set:
o Differential Pickup
o Restraint Low Slope
o Restraint Low Break Point
o Restraint High Breakpoint
o Restraint High Slope
o Differential High Set (if needed)
• All settings entered in per unit (maximum CT primary in the zone)
• Slope settings entered in percent
• Low Slope, High Slope and High Breakpoint settings are used by the CT
Saturation Detector and define the Region 1 Area (2-out-of-2 operation
with Directional)
69. 69
GE Consumer & Industrial
Multilin
29-Oct-22
Calculating Bus Differential Settings –
Minimum Pickup
• Defines the minimum differential current required for
operation of the Bus Zone Differential element
• Must be set above maximum leakage current not zoned off
in the bus differential zone
• May also be set above maximum load conditions for added
security in case of CT trouble, but better alternatives exist
70. 70
GE Consumer & Industrial
Multilin
29-Oct-22
Calculating Bus Differential Settings –
Low Slope
• Defines the percent bias for the restraint currents from
IREST=0 to IREST=Low Breakpoint
• Setting determines the sensitivity of the differential element
for low-current internal faults
• Must be set above maximum error introduced by the CTs in
their normal linear operating mode
• Range: 15% to 100% in 1%. increments
71. 71
GE Consumer & Industrial
Multilin
29-Oct-22
Calculating Bus Differential Settings –
Low Breakpoint
• Defines the upper limit to restraint currents that will be
biased according to the Low Slope setting
• Should be set to be above the maximum load but not more
than the maximum current where the CTs still operate
linearly (including residual flux)
• Assumption is that the CTs will be operating linearly (no
significant saturation effects up to 80% residual flux) up to
the Low Breakpoint setting
72. 72
GE Consumer & Industrial
Multilin
29-Oct-22
Calculating Bus Differential Settings –
High Breakpoint
• Defines the minimum restraint currents that will be biased
according to the High Slope setting
• Should be set to be below the minimum current where the
weakest CT will saturate with no residual flux
• Assumption is that the CTs will be operating linearly (no
significant saturation effects up to 80% residual flux) up to
the Low Breakpoint setting
73. 73
GE Consumer & Industrial
Multilin
29-Oct-22
Calculating Bus Differential Settings –
High Slope
• Defines the percent bias for the restraint currents IRESTHigh
Breakpoint
• Setting determines the stability of the differential element
for high current external faults
• Traditionally, should be set high enough to accommodate
the spurious differential current resulting from saturation
of the CTs during heavy external faults
• Setting can be relaxed in favour of sensitivity and speed as
the relay detects CT saturation and applies the directional
principle to prevent maloperation
• Range: 50% to 100% in 1%. increments
74. 74
GE Consumer & Industrial
Multilin
29-Oct-22
Calculating Unrestrained Bus Differential
Settings
• Defines the minimum differential current for unrestrained
operation
• Should be set to be above the maximum differential current
under worst case CT saturation
• Range: 2.00 to 99.99 p.u. in 0.01 p.u. increments
• Can be effectively disabled by setting to 99.99 p.u.
75. 75
GE Consumer & Industrial
Multilin
29-Oct-22
Dual Percent Differential Characteristic
High
Breakpoint
Low
Breakpoint
Low Slope
High Slope
High Set
(Unrestrained)
Min Pickup
76. 76
GE Consumer & Industrial
Multilin
29-Oct-22
NORTH BUS
SOUTH BUS
CT-8
B-5
B-6
CT-5
CT-6
S-5
S-6
B-4
CT-4
S-3
S-4
B-3
CT-3
S-1
S-2
B-2
CT-2
CT-1
B-1
C-1 C-2 C-4
C-3 C-5
CT-7
B-7
Protecting re-configurable buses
Reconfigurable Buses
77. 77
GE Consumer & Industrial
Multilin
29-Oct-22
NORTH BUS
SOUTH BUS
CT-7
CT-8
B-7
B-5
B-6
CT-5
CT-6
S-5
S-6
B-4
CT-4
S-3
S-4
B-3
CT-3
S-1
S-2
B-2
CT-2
CT-1
B-1
C-1 C-2 C-4
C-3 C-5
Protecting re-configurable buses
Reconfigurable Buses
78. 78
GE Consumer & Industrial
Multilin
29-Oct-22
NORTH BUS
SOUTH BUS
CT-7
CT-8
B-7
B-5
B-6
CT-5
CT-6
S-5
S-6
B-4
CT-4
S-3
S-4
B-3
CT-3
S-1
S-2
B-2
CT-2
CT-1
B-1
C-1 C-2 C-4
C-3 C-5
Protecting re-configurable buses
Reconfigurable Buses
79. 79
GE Consumer & Industrial
Multilin
29-Oct-22
NORTH BUS
SOUTH BUS
CT-8
B-5
B-6
CT-5
CT-6
S-5
S-6
B-4
CT-4
S-3
S-4
B-3
CT-3
S-1
S-2
B-2
CT-2
CT-1
B-1
C-1 C-2 C-4
C-3 C-5
CT-7
B-7
Protecting re-configurable buses
Reconfigurable Buses
80. 80
GE Consumer & Industrial
Multilin
29-Oct-22
Isolators
• Reliable “Isolator Closed” signals are needed for the Dynamic
Bus Replica
• In simple applications, a single normally closed contact may
be sufficient
• For maximum safety:
o Both N.O. and N.C. contacts should be used
o Isolator Alarm should be established and non-valid combinations
(open-open, closed-closed) should be sorted out
o Switching operations should be inhibited until bus image is recognized
with 100% accuracy
o Optionally block 87B operation from Isolator Alarm
• Each isolator position signal decides:
o Whether or not the associated current is to be included in the
differential calculations
o Whether or not the associated breaker is to be tripped
82. 82
GE Consumer & Industrial
Multilin
29-Oct-22
Isolator Open
Auxiliary
Contact
Isolator Closed
Auxiliary
Contact
Isolator Position Alarm Block Switching
Off On CLOSED No No
Off Off LAST VALID After time delay
until
acknowledged
Until Isolator
Position is valid
On On CLOSED
On Off OPEN No No
NOTE: Isolator monitoring function may be a built-in feature or user-
programmable in low impedance bus differential digital relays
Switch Status Logic and Dyanamic Bus
Replica
83. 83
GE Consumer & Industrial
Multilin
29-Oct-22
Differential Zone CT Trouble
• Each Bus Differential Zone may a dedicated CT Trouble
Monitor
• Definite time delay overcurrent element operating on the
zone differential current, based on the configured Dynamic
Bus Replica
• Three strategies to deal with CT problems:
1. Trip the bus zone as the problem with a CT will likely
evolve into a bus fault anyway
2. Do not trip the bus, raise an alarm and try to correct
the problem manually
3. Switch to setting group with 87B minimum pickup
setting above the maximum load current.
84. 84
GE Consumer & Industrial
Multilin
29-Oct-22
• Strategies 2 and 3 can be accomplished by:
Using undervoltage supervision to ride through the period
from the beginning of the problem with a CT until declaring a
CT trouble condition
Using an external check zone to supervise the 87B function
Using CT Trouble to prevent the Bus Differential tripping (2)
Using setting groups to increase the pickup value for the 87B
function (3)
Differential Zone CT Trouble
85. 85
GE Consumer & Industrial
Multilin
29-Oct-22
Differential Zone CT Trouble – Strategy #2
Example
• CT Trouble operand is used to rise an alarm
• The 87B trip is inhibited after CT Trouble
element operates
• The relay may misoperate if an external fault
occurs after CT trouble but before the CT trouble
condition is declared (double-contingency)
87B operates
Undervoltage condition
CT OK
86. 86
GE Consumer & Industrial
Multilin
29-Oct-22
Example Architecture for Large Busbars
Dual (redundant) fiber with
3msec delivery time between
neighbouring IEDs. Up to 8
relays in the ring
Phase A AC signals and
trip contacts
Phase B AC signals and
trip contacts
Phase C AC signals and
trip contacts
Digital Inputs for isolator
monitoring and BF
87. 87
GE Consumer & Industrial
Multilin
29-Oct-22
Phase A AC signals wired
here, bus replica configured
here
Phase B AC signals wired
here, bus replica configured
here
Phase C AC signals wired
here, bus replica configured
here
Auxuliary switches wired here;
Isolator Monitoring function
configured here
Example Architecture – Dynamic Bus
Replica and Isolator Position
88. 88
GE Consumer & Industrial
Multilin
29-Oct-22
Phase A AC signals wired
here, current status
monitored here
Phase B AC signals wired
here, current status
monitored here
Phase C AC signals wired
here, current status
monitored here
Breaker Failure
elements configured
here
Example Architecture – BF Initiation &
Current Supervision
89. 89
GE Consumer & Industrial
Multilin
29-Oct-22
Phase A AC signals wired
here, current status
monitored here
Phase B AC signals wired
here, current status
monitored here
Phase C AC signals wired
here, current status
monitored here
Breaker Fail Op command
generated here and send to trip
appropriate breakers
Trip
Trip
Trip
Example Architecture – Breaker Failure
Tripping Trip
90. 90
GE Consumer & Industrial
Multilin
29-Oct-22
IEEE 37.234
• “Guide for Protective Relay Applications to Power
System Buses” is currently being revised by the K14
Working Group of the IEEE Power System Relaying
Committee.