SIPROTEC 5 Transformerdifferentialprotection En

November 19, 2017 | Author: Ahmed Badr | Category: Electrical Grid, Transformer, Automation, Communications Protocols, Smart Grid
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SIPROTEC 5 Transformer differential protection...

Description

Protection

SIPROTEC 5 – Transformer Differential Protection 7UT85, 7UT86, 7UT87 Catalog SIPROTEC 5.04 · Edition 1

Answers for infrastructure and cities.

Device manuals

System catalog

Hardware manual

Operating manual SIPROTEC 5/DIGSI 5 Tutorial

Device catalogs

Communication protocol manuals

Product information

Engineering Guide

Online help DIGSI 5 Online help devices

Documentation overview SIPROTEC 5-System

Systemcatalog

Product information

The system catalog describes the SIPROTEC 5 system features.

The product information includes general information about device installation, technical data, limiting values for input and output modules, and conditions when preparing for operation. This document is delivered with each SIPROTEC 5 device.

Device catalogs The device catalogs describe device-specific features such as functional scope, hardware and applications. Device manuals The device manuals describe the functions and applications of a specific SIPROTEC 5 device. The printed manual and the online help for the device have the same informational structure. Hardware manual The hardware manual describes the hardware components and device combinations of the SIPROTEC 5 device family. Operating manual The operating manual describes the basic principles and procedures for operating and assembling the devices of the SIPROTEC 5 device family. Communication protocol manuals The communication protocol manuals include a description of specific protocols for communication within the SIPROTEC 5 device family and to higher-level control centers.

Engineering Guide The Engineering Guide describes the important steps for Engineering with DIGSI 5. The Engineering Guide offers information on how to load a configuration to a SIPROTEC 5 device and how to update the device functionality of a SIPROTEC 5 device. DIGSI 5 online help The DIGSI 5 online help contains a help package for DIGSI 5 and CFC. The help package for DIGSI 5 includes a description of the basic operation of software, the DIGSI principles and editors. The help package for CFC includes an introduction to CFC programming, basic examples of CFC handling, and a reference chapter with all CFC blocks available for the SIPROTEC 5 device family. Online help devices The online help for devices has the same information structure as the device manual. SIPROTEC 5 / DIGSI 5 Tutorial The tutorial on the DVD contains brief information about important product features, more detailed information about the individual technical areas, as well as operating sequences with tasks based on practical operation and a brief explanation.

2 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

Contents SIPROTEC 5 – Transformer Differential Protection 7UT85, 7UT86, 7UT87 Energy Automation

Introduction 5 Transformer Differential Protection

6

Overview 6 Transformer Differential Protection Devices

7

Two winding transformer 7UT85 Three winding transformer 7UT86 Multiple winding transformers 7UT87

7 12 16

Description of the Device Functions

21

Functional integration, protection 21 Controll, Automation 29 Monitoring 30 Data acquisition and recording 30 Communication, Cyber Security 33 Test 34

Catalog SIPROTEC 5.04 · Edition 1 www.siemens.com/siprotec

Overview of the standard variants

35

Notes

36

Legal Notice

39

The products and systems described in this catalog are manufactured and sold according to a certified management system (acc. to ISO 9001, ISO 14001 and BS OHSAS 18001).

SIPROTEC 5 – Transformer Differentail Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

3

Editorial SIPROTEC has been a recognized brand leader in digital protection and field devices on the energy market for decades. The Siemens high-performance SIPROTEC devices cover the entire power spectrum and can be implemented in a wide range of fields – from power generation to very high voltage transmission and distribution network applications. “Smart automation for transmission grids” is the Siemens response to the present and future challenges to achieve a reliable and efficient energy supply. SIPROTEC 5 is an active component of the energy-efficient smart grid and an important building block in the complex distributed energy supply systems and networks solutions. The next generation of SIPROTEC devices, SIPROTEC 5, is based on the proven features of SIPROTEC 4 to provide you with a new, modern platform including both hardware and software. This platform offers an excellent solution to the challenges associated with evolving grid structures and workflows. The quality, reliability and proven functions of the former system have been preserved. Innovative approaches including holistic workflow, safety and security, and network stability monitoring (PMU functionality) have been added. The pioneering system architecture places you in full control of switchgear communications. A powerful, reliable communication infrastructure, combined with the flexible engineering capabilities serves as the basis for monitoring and controlling of distributed, decentralized systems. Seamless communications is the central component of the SIPROTEC 5 system architecture to provide flexibility, safety and security in the automated distributed network solutions. With SIPROTEC 5, you are at the beginning of a new generation of intelligent, digital multifunction field devices. The new operating tool DIGSI 5 offers individual support for you – handles your specific workflow requirements, from system design to device selection and testing, covering the entire device lifecycle. The new tool offers cost savings over the entire lifecycle without compromising safety and system availability. With the new SIPROTEC 5 generation, you are well equipped to meet the growing economic and reliability demands imposed on your networks. The philosophy of SIPROTEC 5 is reflected in the modularity and flexibility of its hardware and software components. Perfectly tailored fit – the custom fit for your switchgear and specifications for the application and standardization of energy automation. Ingo Erkens General Manager Infrastructure and Cities Sector Smart Grid Division Energy Automation

4 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

Introduction SIPROTEC 5-Transformer Differential Protection SIPROTEC 5-Transformer Differential Protection is part of the modular system of SIPROTEC 5. It supports all SIPROTEC 5 system features, and can be used individually as well as universally in the framework of system solutions. In the following, the specific properties of the SIPROTEC 5-Transformer Differential Protection is described. The description of the SIPROTEC 5 system features is found in the system catalog. The following properties of SIPROTEC 5 are introduced there in detail: • The SIPROTEC 5 system Protection Systems

• Areas of use

SIPROTEC 5 – System Overview Protection, Automation and Monitoring

• Hardware

Catalog SIPROTEC 5.01 · V1.0

• Engineering

Answers for infrastructure and cities.

• Communication

SIP_5_01_2011_En_Kap_01.indd 1

29.03.12 11:55

SIPROTEC 5 System catalog Order-No. E50001-K4605-A011-A1-7600

• IEC 61850 – Simply usable • Test and diagnostics • Safety concept • DIGSI 5. The system catalog can be ordered free of charge from your Siemens contact partner under order number E50001-K4605-A011-A1-7600.

SIPROTEC 5 transformer protection devices are multifunctional devices whose main protection functions are based on the differential protection principle. They protect different types of transformers, such as two-winding, three-winding and multi-winding transformers with different numbers of measuring points and, besides standard power transformers, also autotransformers. The devices can be used in all voltage levels. The great number of protection and automatic functions permits use in all fields of electric power supply. The devices also contain important additional functions that are necessary for safe network operation today. This includes functions for protection, control, measurement and monitoring. The large number of communication interfaces and communicationprotocols satisfies the requirements of communication-based selective protection, as well as a automated operation. Commissioning and maintenance work can be completed safely, quickly and thus cost-effectively with high-performance test functions. Because of a modular structure design, the SIPROTEC 5-Transformer Differential Protection can always be flexibly adapted to specific requirements.

SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 5

Overview Definition of device types based on designation Function library and application templates Main protection functions

The extensive SIPROTEC function library is also available in the Transformer Differentail Protection devices. Thus, numerous protection functions such as overcurrent protection, overvoltage protection or frequency protection are available. These functions are truly the same for all devices. Once established, configurations can be transferred from device to device. This results in substantially reduced engineering effort.

Distinguishing features

7 XX

YY

Basic distinguishing features 7

UT

85

Two Winding Transformer Differential Protection (2 sides and max 4 measuring points)

7

UT

86

Three Winding Transformer Differential Protection (3 sides und max 5 measuring points)

7

UT

87

Multiple Winding Transformer Differential Protection (5 sides und max 7 measuring points)

In this catalog you will find predefined templates for standard applications. These templates already contain basic configurations, required functions and default settings for standard applications.

Features The device types are defined by their main protection functions and by essential distinguishing features. For devices with flexible configurability of the hardware quantity structure, you can select various standard variants when ordering. The device can be adapted by additional expansion modules individually to your specific applications (see “Overview of the standard variants”, page 35).

6MD8

7SL87

7SA87

7SS8*

7SD87

7KE85

7SJ86

7VK87

7SA84

7SA84

7SJ82*

6MD8

7SA86

7SD84

7SJ82*

7SA86

7SJ85

7SJ85

7SS8*

7SJ85

7SD86

7SJ85

7SD84

7SK82*

7UT8

7KE85

7SJ86

7SL86

7UT8

7SD86

7SK85

G * in preparation

Fig. 1  Application of SIPROTEC 5 devices

6 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

Visio-SIP503-002-us.

M

Transformer Differential Protection 7UT8 Two winding transformer 7UT85 Properties – 7UT85 Short description

Differential protection for two winding transformers for all voltage levels

Main protection

1 Differential protection (standard- or autotransformer) with add-on stabilizations; Up to 2 differential ground-fault protection

Useful measuring point

4 three-pole current measuring points 2 one-pole current measuring points 2 three-pole voltage measuring points

Inputs and outputs

2 predefined standard variants with 8 current transformers, 7 to 19 binary inputs, 7 to 23 binary outputs

Hardware flexibility

Flexible adaptable and expandable I/Oquantity structure within the scope of the modular SIPROTEC 5-building blocks

Width of housing

1/3 × 19“ to 1/1 × 19“

•  Transformer protection for two-winding transformers with versatile additional protection functions •  Universal usability of the admissible measuring points •  Usable from medium up to extra-high voltage Fig. 2  T  ransformer differential protection 7UT85 (1/3 device = standard variant O1)

•  Protection of standard power transformers and autotransformers •  Typical properties of a transformer differential protection such as flexible adaptation to the transformer vector group, consideration of inrush and overexcitation processes, safe behavior in the case of current transformer saturation with different degrees of saturation •  Increased sensitivity in the case of ground faults close to neutral through a separate ground fault differential protection •  Further current and voltage inputs can be added for standard protection functions such as overcurrent, voltage, frequency, etc. •  Two communication modules can be plugged and different protocols can be used (IEC61850, IEC 60870-5-103, DNP 3 (serial, TCP), Modbus RTU Slave) in the standard version •  Powerful automation with CFC (Continous Function Chart) •  Secure serial protection data communication, also over great distances and all available physical media (fiber-optic cable, 2-wire connections and communication networks) •  Measurement of relevant operational values •  Powerful fault recording

It is the main protection for the transformer and contains many other protection and monitoring functions. The additional protection functions can also be used as backup protection for protected downstream objects (e.g. cables, line). The modular expansion capabilities of the hardware support you here. The device supports all SIPROTEC 5 system characteristics. It enables future-oriented system solutions with high investment security and low operating costs.

Functions Table 1 on page 11 shows all functions that are available in the 7UT85. Basically, all functions can be configured freely with DIGSI 5. For the application of some of the functions, you require the appropriate number of free function points within the device. The function point calculator in the online configurator provides support in determining the required number of function points for your device.

•  Consistent monitoring concept •  Additonal functions for simple tests and commissioning.

Applications The transformer differential protection 7UT85 is a universal protection, control and automation device on the basis of the SIPROTEC 5 system. It is especially designed for the protection two winding transformers.

Application templates Application templates are available in DIGSI for standard applications. They comprise all basic configurations and default settings. You can use them directly or as a template for application-specific adaptations. Versatile applications are possible due to the available measuring points. Please, configure the application with DIGSI first before you order a device. Table 1 on page 11 shows the functional scope of the device. You ascertain the function point requirement about the configurator.

SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 7

Transformer Differential Protection 7UT8 Two winding transformer 7UT85 For typical standard applications the following application templates for 7UT85 are available:

Two winding in 1,5 circuit-breaker application (Fig. 5)

Two winding basic (Fig. 3)

•  Differential ground-fault protection on the star side

•  Differential protection (default setting for Yd),

•  Overload protection, backup protection for the downstreamed power system

•  Differential protection (default setting for Yd),

•  Overload protection, backup protection for the downstreamed power system

•  Circuit-breaker failure protection

Two winding basic with REF (restricted earth fault) (Fig.4) •  Differential protection (default setting for Yd),

Fig. 3 shows the typical structure of an application template, the used measuring points, the used function groups, whose intern circuiting and the predefined functions. The two winding transformer with differential ground-fault protection was exemplary select.

•  Differential ground-fault protection on the star side •  Overload protection, backup protection for the downstreamed power system •  Circuit-breaker failure protection

52 A-QA FG Transformer side 1

FG Circuit breaker A-QA

I-3ph

I-3ph 49

Ctrl

Measured values

MP I-3ph 2

FG Transformer side 2

I-3ph 50

FG Transformer 1

87

51

Measured values

52 B-QA

FG MP BI BO QA/ CB Ctrl

CB

Function group Measuring point Binary input Binary output Circuit breaker Control

FG Circuit breaker B-QA

I-3ph

Ctrl

CB

49 50/51 87

BI BO

BI BO

Overload protection Overcurrent protection Differential protection

Fig. 3  Application example: protection of a two winding transformer

8 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

Visio-Two_Wind_temp-01-us

MP I-3ph 1

Transformer Differential Protection 7UT8 7UT85 Application examples

52 A-QA

MP I-3ph 1

FG Transformer side 1

FG Circuit breaker A-QA

I-3ph

I-3ph 49

50BF Ctrl

87N

Measured values

MP I-1ph 1

CB

FG Transf. neutral point 1

BI BO

FG Transformer 1

I-1ph 50N

51N

87

Measured values

I-3ph

FG Circuit breaker B-QA

I-3ph 50

51

Function group Measuring point Binary input Binary output Circuit breaker Control

50BF Ctrl

Measured values

52 B-QA

FG MP BI BO QA/ CB Ctrl

FG Transformer side 2

CB

49 50BF 50/51 50N/51N 87 87N

Overload protection Circuit-breaker failure protection Overcurrent protection Overcurrent protection, ground Differential protection Ground-fault differential protection

BI BO

Visio-Two_Wind_temp-02-us

MP I-3ph 2

Fig. 4  Application example: two winding transformer basic with REF

SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 9

Transformer Differential Protection 7UT8 7UT85 Application examples

52 A-QA

MP I-3ph 1 MP I-3ph 2

FG Transformer side 1

FG Circuit breaker A-QA

I-3ph

I-3ph 49

50BF Ctrl

87N

Measured values

CB

FG Transformer 1

FG Transf. neutral point 1

I-1ph MP I-1ph 1

FG Circuit breaker B-QA

I-3ph 50N

87

51N

50BF Ctrl

Measured values

MP I-3ph 3 52 C-QA

FG MP BI BO QA/ CB Ctrl

CB

FG Transformer side 2

I-3ph 51

50BF Ctrl

Measured values

Function group Measuring point Binary input Binary output Circuit breaker Control

CB

49 50BF 50/51 50N/51N 87 87N

BI BO

FG Circuit breaker C-QA

I-3ph 50

BI BO

Overload protection Circuit-breaker failure protection Overcurrent protection Overcurrent protection, ground Differential protection Ground-fault differential protection

Fig. 5  Application example: Two-winding transformer in 1 1/2 circuit-breaker layout

10 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

BI BO

Visio-Two_Wind_temp-03-us

52 B-QA

Transformer Differential Protection 7UT8 7UT85 Functions, application templates

ΔI



87N T

Low impedance restricted ground-fault protection

ΔIN



25

Synchrocheck, synchronizing function

Sync



27

Undervoltage protection, 3-phase

V<



27

Undervoltage protection, positive-sequence system

V1<



27

Undervoltage protection, 1-phase, undercurrent, underpower

Vx<



32, 37

Power protection active/reactive power

P,Q



38

Temperature supervision

θ>



46

Negative-sequence system overcurrent protection

I2>; I2/I1>



46

Unbalanced load protection

I22 t>

49

Thermal overload protection

θ, I2t



50BF

Circuit-breaker failure protection

CBFP



50/51

Definite/Inverse time-overcurrent protection

I>, IP>



50N/51N

Time overcurrent protection, ground

IN>, INP>

50HS

High speed instantaneous overcurrent protection

I>>>

50

Overcurrent protection, 1-phase

50Ns/51Ns

2 winding transf. 1.5 CB (DIFFprotection,REF)

Abr.

Differential protection, transformer

2 winding transf. (DIFF-protection, BF, REF)

Function

87T

2 winding transf. basic (DIFFprotection)

ANSI

available

Application templates

















































I1ph>









Sensitive ground-current protection

IN>, INP>



59

Overvoltage protection, 3-phase

V>



59

Overvoltage protection, positive-sequence system

V1>



59

Overvoltage protection, negative-sequence system

V2>



59N

Overvoltage protection, zero-sequence system

V0>



59

Overvoltage protection, 3-phase, universal,

Vx>

67

Directional time-overcurrent protection, phase

I>,IP,

67N

Directional time-overcurrent protection for ground-faults

IN>, INP, (V,I)



67Ns

Sensitive ground fault detection for systems with resonant and isolated neutral

INs>, (V,I)



74TC

Trip circuit supervision

TCS









81O

Overfrequency protection

f>



81U

Underfrequency protection

f<



86

Lockout







PMU

Synchrophasor measurement









(V,I)





PMU



Standard measured values



Measured values, extended: min, max, medium



Switching statistic









CFC standard









CFC arithmetic



CFC switching sequences for control applications



Inrush current detection









External trip initiation









Control









Fault recording of analog and binary signals









Monitoring and supervision









Protection interface, serial









Circuit breaker









Disconnector/Grounding conductor









0

30

30

Function points

The configuration and function points for your application can be ascertained in the SIPROTEC 5 order configurator under: www.siemens.com/protection

Table 1  7UT85 Functions, Application templates

SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 11

Transformer Differential Protection 7UT8 Three winding transformer 7UT86 Properties – 7UT86 Short description

Differential protection for three winding transformers for all voltage levels

Main protection

1 Differential protection (standard) with add-on stabilizations; Up to 3 differential ground-fault protection For autotransformer applications 2 differential protection functions in a function group autotransformer can be used.

Useful measuring point

5 three-pole current measuring points 3 one-pole current measuring points 3 three-pole voltage measuring points

Inputs and outputs

2 predefined standard variants with 12 current transformers, 4 voltage transformers 11 to 23 binary inputs, 18 to 34 binary outputs

Hardware flexibility

Flexible adaptable and expandable I/Oquantity structure within the scope of the modular SIPROTEC 5-building blocks

Width of housing

1/2 × 19“ bis 1/1 × 19“

•  Transformer protection for three-winding transformers with versatile additional protection functions •  Universal usability of the admissible measuring points •  Usable from medium up to extra-high voltage •  Protection of standard power transformers and autotransformers •  Typical properties of a transformer differential protection such as flexible adaptation to the transformer vector group, consideration of inrush and overexcitation processes, safe behavior in the case of current transformer saturation with different degrees of saturation •  Increased sensitivity in the case of ground faults close to neutral through a separate ground fault differential protection •  Further current and voltage inputs can be added for standard protection functions such as overcurrent, voltage, frequency, etc. •  Two communication modules can be plugged and different protocols can be used (IEC61850, IEC 60870-5-103, DNP3 (serial, TCP), Modbus RTU Slave) in the standard version •  Powerful automation with CFC (Continous Function Chart) •  Safe serial protection data communication also across large distances and all available physical media (fiber optic, two-wire connections and communication networks) •  Measurement of all relevant operating variables •  Powerful fault recording •  Consistent monitoring concept •  Help functions for simple tests and easy commissioning

Fig. 6  Transformer differential protection 7UT86 (1/2 device = standard variant P1)

Applications The transformer differential protection 7UT86 is a universal protection, control and automation device on the basis of the SIPROTEC 5 system. It is especially designed for the protection of three winding transformers. It is the main protection for the transformer and contains numerous other protection and monitoring functions. In addition the protection functions can also be used as backup protection for following protected objects (for example cable, line). At this it supports also modular availablility of the hardware. The device supports all SIPROTEC 5 system characteristics. It enables future-oriented system solutions with high investment security and low operating costs. Functions Table 2 on page 14 shows all functions that are available in 7UT86. Basically, all functions can be configured freely with DIGSI 5. For the application of some of the functions, you require the appropriate number of free function points within the device. The function point calculator in the online configurator provides support in determining the required number of function points for your device. Application templates Application templates are available in DIGSI for standard applications. They comprise all basic configurations and default settings. You can use them directly or as a template for application-specific adaptations. Versatile applications are possible due to the available measuring points. Please, configure the application with DIGSI first before you order a device. Table 2 on page 14 shows the functional scope of the device. You ascertain the function point requirement about the configurator.

12 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

Transformer Differential Protection 7UT8 Three winding transformer 7UT86 The application templates for 7UT85 are also available in 7UT86.

•  Differential protection (default setting for YNdxdy)

In addition, the following templates are available:

•  Differential ground-fault protection on the neutral side

Three winding basic

•  Ground current-protection on the neutral side as backup protection for power systems

•  Differential protection (default setting for Ydxdy)

•  Overload protection

Autotransformer with delta winding

•  Circuit-breaker failure protection

•  Differential protection for complete transformer (auto transformer + delta winding)

•  Frequency- and voltage protection on the star winding side

•  Differential ground-fault protection (neutral point + max side current)

The application example (Fig. 7) is the template for the protection of a three-winding transformer in a 1 1/2 circuitbreaker layout. You can see the necessary three function groups for the transformer side, the integration of the ground fault differential protection and the internal wiring and selected functions. A voltage transformer is installed on the high voltage in addition. For example, voltage and frequency limits can be monitored here. The necessary protection settings have to be made specifically for the system.

•  Overload protection, backup protection for the downstreamed power system •  Circuit-breaker failure protection

52 B-QA

Three winding in 1.5 circuit-breaker application (Fig.7)

52 A-QA

FG Transformer side 1

MP I-3ph 1

I-3ph 49

MP I-3ph 2

I-3ph

V 3-ph 59 81

MP V-3ph 1

MP I-1ph 1

FG Circuit breaker A-QA

87NT

50BF Ctrl

Measured values

CB FG Transf. neutral point 1

FG Circuit breaker B-QA

I-1ph

I-3ph 50N

51N

50BF Ctrl

Measured values

MP I-3ph 3

FG Transformer side 2

BI BO

CB FG Transformer 1

I-3ph

BI BO

FG Circuit breaker C-QA

I-3ph

50BF Ctrl

Measured values

MP I-3ph 4

87T

FG Transformer side 3

I-3ph

CB

BI BO

FG Circuit breaker D-QA

I-3ph

50BF Ctrl

52 C-QA

FG MP BI BO QA/ CB Ctrl

Function group Measuring point Binary input Binary output Circuit breaker Control

Measured values

49 50BF 51N 59 81 87T 87NT

Overload protection Circuit-breaker failure protection Overcurrent protection, ground Overvoltage protection Frequency protection Transformer differential protection Ground-fault differential protection transformer

CB

BI BO

Visio-Kat-three-wind-us

52 D-QA

Fig. 7  Application example: protection of a three winding transformer in 1 1/2 circuit-breaker layout SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 13

Transformer Differential Protection 7UT8 7UT86 Functions, application template

ANSI

Function

Abr.

available

3 winding transf. basic (DIFF-protection)

3 winding transf. 1.5 CB (DIFF-protection BF, REF)

Autotransformer (DIFF-protection, BF, REF)

2 winding transf. basic (DIFF-protection)

2 winding transf. (DIFF-protection, BF, REF)

2 winding transf. 1.5 CB (DIFF-protection, BF, REF)

Application templates

87T

Differential protection, transformer

ΔI















87T Node

Differential protection, transformer (node protection)

ΔI (node)















87N T

Low impedance restricted ground-fault protection

ΔIN











25

Synchrocheck, synchronizing function

Sync



27

Undervoltage protection, 3-phase

V<



27

Undervoltage protection, positive-sequence system

V1<



27

Undervoltage protection, 1-phase, undercurrent, underpower

Vx<



32, 37

Power protection active/reactive power



38

Temperature supervision

P,Q θ>













46

Negative-sequence system overcurrent protection

I2>; I2/I1>



46

Unbalanced load protection

I22t>



49

Thermal overload protection

θ, I2t















50BF

Circuit-breaker failure protection

CBFP







50/51

Definite/Inverse time-overcurrent protection

I>, IP>









50N/51N

Time overcurrent protection, ground

IN>, INP>







50HS

High speed instantaneous overcurrent protection

I>>>







50

Overcurrent protection, 1-phase

I1ph>





50Ns/51Ns

Sensitive ground-current protection

IN>, INP>



59

Overvoltage protection, 3-phase

V>



59

Overvoltage protection, positive-sequence system

V1>



59

Overvoltage protection, negative-sequence system

V2>



59N

Overvoltage protection, zero-sequence system

V0>



59

Overvoltage protection, 3-phase, universal,

Vx>

67

Directional time-overcurrent protection, phase

I>,IP,

67N

Directional time-overcurrent protection for ground-faults

IN>, INP, (V,I)



67Ns

Sensitive ground fault detection for systems with resonant and isolated neutral

INs>, (V,I)



74TC

Trip circuit supervision

TCS





81O

Overfrequency protection

f>



81U

Underfrequency protection

f<



86

Lockout

PMU

Synchrophasor measurement



















































(V,I)





PMU

  

























Standard measured values



Measured values, extended: min, max, medium



Switching statistic















CFC standard















CFC arithmetic



CFC switching sequences for control applications



Inrush current detection















External trip initiation















Control















Fault recording of analog and binary signals















Monitoring and supervision















Protection interface, serial















Circuit breaker















Disconnector/Grounding conductor















0

50

30

0

30

30

Function points

The configuration and function points for your application can be ascertained in the SIPROTEC 5 order configurator under: www.siemens.com/protection Table 2  7UT86 Functions, Application templates 14 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

Transformer Differential Protection 7UT8 Multiple winding transformer 7UT87 Properties – 7UT87 Short description

Differential protection for multiple winding transformers for all voltage levels

Main protection

Up to 2 differential protection with add-on stabilizations (in different function group transformer); Up to 5 differential ground-fault protection functions For autotransformer applications two differential protection functions in a function group autotransformer can be used.

Useful measuring point

7 three-pole current measuring points 5 one-pole current measuring points 3 three-pole voltage measuring points

Inputs and outputs

2 predefined standard variants with 20 current transformers, 4 voltage transformers 15 to 27 binary inputs, 2 to 38 binary outputs

Hardware flexibility

Flexible adaptable and expandable I/Oquantity structure within the scope of the modular SIPROTEC 5-building blocks

Width of housing

2/3 × 19“ bis 1/1 × 19“

•  Transformer protection for multiple winding transformers with multifunctional, additional protection functions (Multiple winding transfomer are typical with power converter applications (e.g. HVDC)) •  Transformer protection applications where up to 7 3-pole current measuring point are necessary •  Concurrent differential protection for two parallel transformers (e.g. two two-winding transformers) •  Universal usability of the admissible measuring points •  Usable from medium up to extra-high voltage •  Protection of standard power transformers and autotransformers •  Typical properties of a transformer differential protection such as flexible adaptation to the transformer vector group, consideration of inrush and overexcitation processes, safe behavior in the case of current transformer saturation with different degrees of saturation •  Increased sensitivity in the case of ground faults close to neutral through a separate ground fault differential protection •  Further current and voltage inputs can be added for standard protection functions such as overcurrent, voltage, frequency, etc. •  Two communication modules can be plugged and different protocols can be used (IEC61850, IEC 60870-5-103, DNP 3.0 (serial+IP), Modbus RTU Slave) in the standard version •  Powerful automation with CFC (Continous Function Chart) •  Safe serial protection data communication also across large distances and all available physical media (fiber optic, two-wire connections and communication networks) •  Measurement of all relevant operating variables •  Powerful fault recording

Fig. 8  Transformer differential protection 7UT87 (2/3 device = standart varaiant Q1)

Applications The transformer protection device 7UT87 is an universal protection, control and automation device on the basis of the SIPROTEC 5 system. It is especially designed for protection of multiple winding transformers (up to 5 sides). Further it is to be used there, where a numerous of measuring points (up to 7 3-pole current measuring points) are required. Another application is simultaneously protection of two parallel transformers (additional fast backup protection). The 7UT87 is the main protection for the transformer and includes a numerous other protection and monitoring functions. In addition the protection functions can also be used as backup protection for following protected objects (for example cable, line). At this it supports also modular availability of the hardware. The device supports all SIPROTEC 5 system characteristics. It enables future-oriented system solutions with high investment security and low operating costs.

Functions Table 3 on page 20 shows all functions that are available in 7UT87. Other than in 7UT86, two transformer function groups can be used in 7UT87. Basically, all functions can be configured freely with DIGSI 5. For the application of some of the functions, you require the appropriate number of free function points within the device. The function point calculator in the online configurator provides support in determining the required number of function points for your device.

•  Consistent monitoring concept •  Help functions for simple tests and easy commissioning

SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 15

Transformer Differential Protection 7UT8 Application examples 7UT87 Application templates

The application example is the template for the protection of an autotransformer which is connected to a 1 1/2 circuit-breaker layout. The special feature of this application is that the neutralend currents can be detected directly per phase. A separate node point differential protection over the autotransformer winding detects safely ground faults and interturn faults. The classical differential protection is arranged over the entire transformer (autotransformer and delta winding). Both functions run in the function group autotransformer.

All application templates which are described for the devices 7UT85 and 7UT86 can be used in 7UT87. Autotransformer with delta winding in 1.5 circuit-breaker application •  Differential protection for complete transformer (auto transformer + delta winding) •  Node protection for autotransformer winding to the capture of ground faults (three-phase capture of the neutral-point current) •  Overload protection, backup protection for the downstreamed power system •  Circuit-breaker failure protection •  Frequency- and voltage protection on the upper voltage side.

52 B-QA

52 A-QA MP I-3ph 1 MP I-3ph 2 MP V-3ph 1

This design provides a redundant differential protection which is supplementary with regard to sensitivity. A separate ground fault differential protection is not required. A voltage transformer is installed on the high voltage in addition. For example, voltage and frequency limits can be monitored here. The necessary protection settings have to be made specifically for the system.

FG Auto transformer side 1

I-3ph

FG Circuit breaker A-QA

I-3ph

49 V-3ph

Ctrl

59 81

Measured values

CB FG Transformer 1

MP I-3ph 3

50BF

FG Auto transformer side 2

I-3ph

87T

BI BO

FG Circuit breaker B-QA

I-3ph

50BF Ctrl

87TNode 50

51

CB

BI BO

Measured values FG Circuit breaker C-QA

MP I-3ph 4

Auto transformer FG compensation side

I-3ph

50BF Ctrl

I-3ph 50

CB

51

BI BO

Measured values FG Circuit breaker D-QA

52 D-QA MP I-3ph 5

Auto transformer ground FG side

I-3ph

Function group Measuring point Binary input Binary output Circuit breaker Control

Ctrl

I-3ph Measured values

FG MP BI BO QA/ CB Ctrl

50BF

49 50BF 50/51 59 81 87T 87TNode Ctrl

CB

Overload protection Circuit-breaker failure protection Overcurrent protection Overvoltage protection Frequency protection Transformer differential protection Differential protection auto transformer Control

Fig. 9  Application example: protection of an autotransformer with delta winding (compensation side) in 1 1/2 circuit-breaker layout 16 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

BI BO

Autotrans-us

52 C-QA

Transformer Differential Protection 7UT8 7UT86 Application examples Example 1:

Since 7UT87 is designed for special applications, you have to create your own application template for your specific application. Save it together with your device. To make your work easier, you can use an existing template and modify it.

This example requires numerous three-phase current measuring points for a complex use in the field of power plant. The figure 10 shows a possible configuration.

The following examples shall help you:

52 B-QA

52 A-QA MP I-3ph 1

FG Transformer side 1

I-3ph 27

MP I-3ph 2 MP V-3ph 1

V-3ph

49

32

59

50

59N

51

87N

Measured values

81

FG Transformer 1

FG Circuit breaker A-QA

I-3ph

50BF Ctrl

87T CB

MP I-1ph 1

FG Transf. neutral point 1

I-1ph

FG Circuit breaker B-QA

I-3ph 50N

51N

50BF Ctrl

Measured values

MP I-3ph 3 MP I-3ph 4

MP I-3ph 5 MP I-3ph 6

MP I-3ph 7

F-QA 52

C-QA

D-QA

52

52

G

G

E-QA

CB

FG Transformer side 2

I-3ph 51

50BF Ctrl

Measured values

CB

FG Transformer side 3

I-3ph 51

50BF Ctrl

Measured values

CB

FG V, I standard 1

BI BO

FG Circuit breaker E-QA

I-3ph

I-3ph 50

BI BO

FG Circuit breaker D-QA

I-3ph 50

BI BO

FG Circuit breaker C-QA

I-3ph 50

BI BO

51

50BF Ctrl

Measured values

CB

52

BI BO

FG Circuit breaker F-QA

I-3ph

50BF Ctrl

FG MP BI BO QA/ CB Ctrl

Function group Measuring point Binary input Binary output Circuit breaker Control

27 32 49 50BF 50/51 50N/51N 59 59N 81 87T 87N

Undervoltage protection Power protection Overload protection Circuit-breaker failure protection Overcurrent protection Overcurrent protection, ground Overvoltage protection Overvoltage protection with zero-sequence voltage/residual voltage Frequency protection Transformer differential protection Ground-fault differential protection

BI BO

7 Messstellen_us

CB

Fig. 10  Possible 7UT87 application in a power station (up to 7 3-pole current measuring point) SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 17

Transformer Differential Protection 7UT8 Application examples 7UT87 Example 2

for the parallel transformer. For example, start here with an application template of the two-winding transformer and Another example (Fig.11) is a powerful functional redundancy with parallel transformers. This doubles the differential protection duplicate it. function. One protection device is provided per transformer. Two An alternative cost-optimized variant is the use of one device to differential protection functions run in every protection device. protect both transformers. The 2nd differential protection function is the backup protection

A-QA 52 MP I-3ph 1

FG Transformer side 1

FG Transformer 1

I-3ph

FG Circuit breaker A-QA

I-3ph

50BF Ctrl

87T

Measured values

CB

MP I-1ph 1

BI BO

FG Transf. neutral point 1

I-1ph

Measured values

Transformer 1

MP I-3ph 2

FG Transformer side 2

FG Circuit breaker B-QA

I-3ph

I-3ph

50BF Ctrl

Measured values

B-QA 52

CB

BI BO

C-QA 52 MP I-3ph 3

FG Transformer side 3

FG Transformer 2

I-3ph

FG Circuit breaker C-QA

I-3ph

50BF Ctrl

87T

Measured values

CB

MP I-1ph 2

BI BO

FG Transf. neutral point 2

I-1ph

Measured values

Transformer 2

MP I-3ph 4

FG Transformer side 4

FG Circuit breaker D-QA

I-3ph

I-3ph

50BF Ctrl

D-QA 52

FG MP BI BO QA/ CB Ctrl

Fig. 11

CB

Function group Measuring point Binary input Binary output Circuit breaker Control

50BF 87T

Circuit-breaker failure protection Differential protection

Protection of two parallel transformers with one 7UT87

18 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

BI BO Visio-2-transformer-us

Measured values

Transformer Differential Protection 7UT8 Application examples 7UT87 Example 3 The last example (Fig.12) shows the protection of a converter transformer. Four sides and six measuring points are required here.

Infeed 52

S1

S2

S4

S3

A-QA

Filter

DC CONVERTER

52 MP I-3ph 1

FG Transformer side 2

I-3ph Measured values

52 MP I-3ph 2

FG Transformer side 3

I-3ph Measured values FG Circuit breaker A-QA

MP I-3ph 3

FG Transformer side 4

FG Transformer 1

I-3ph

I-3ph

50BF Ctrl

Measured values

87T

52

CB

BI BO

Filter

MP I-3ph 5 MP I-3ph 6 FG MP BI BO QA/ CB Ctrl

Fig. 12

Function group Measuring point Binary input Binary output Circuit breaker Control

FG Transformer side 1

I-3ph Measured values

50BF 87T

Circuit-breaker failure protection Differential protection

Umrichter_Transformers-us

MP I-3ph 4

Protection of a converter transformer

SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 19

Transformer Differential Protection 7UT8 7UT87 Functions, application templates

ANSI

Function

Abr.

available

3 winding transf. basic (DIFF-protection)

3 winding transf. 1.5 CB (DIFF-protection, BF, REF)

Autotransformer (DIFF-protection, BF, REF)

Autotransformer + 1.5 CB (2 DIFF-protection, BF, V,f)

2 winding transf. basic (DIFF-protection)

2 winding transf. (DIFF-protection, BF,REF)

2 winding transf. 1.5 CB (DIFF-protection, BF, REF)

Application templates

87T

Differential protection, transformer

ΔI

















87T Node

Differential protection, transformer (node protection)

ΔI (node)

















87N T

Low impedance restricted ground-fault protection

ΔIN











25

Synchrocheck, synchronizing function

Sync



27

Undervoltage protection, 3-phase

V<



27

Undervoltage protection, positive-sequence system

V1<



27

Undervoltage protection, 1-phase, undercurrent, underpower

Vx<



32, 37

Power protection active/reactive Temperature supervision

P,Q θ>



38















46

Negative-sequence system overcurrent protection

I2>; I2/I1>



46

Unbalanced-load protection (thermal)

I22 t>



49

Thermal overload protection

θ, I2t

















50BF

Circuit-breaker failure protection

CBFP









50/51

Definite/Inverse time-overcurrent protection

I>, IP>











50N/51N

Time overcurrent protection, ground

IN>, INP>









50HS

High speed instantaneous overcurrent protection

I>>>









50

Overcurrent protection, 1-phase

I1ph>









50Ns/51Ns

Sensitive ground-current protection

IN>, INP>



59

Overvoltage protection, 3-phase

V>



59

Overvoltage protection, positive-sequence system

V1>



59

Overvoltage protection, negative-sequence system

V2>



59N

Overvoltage protection, zero-sequence system

V0>



59

Overvoltage protection, 3-phase, universal,

Vx>

67

Directional time-overcurrent protection, phase

I>,IP

67N

Directional time-overcurrent protection, ground

IN>, INP

67Ns

Sensitive ground fault detection for systems with resonant and isolated neutral

INs>, (V,I)



74TC

Trip circuit supervision

TCS



81O

Overfrequency protection

f>



81U

Underfrequency protection

f<



86

Lockout

PMU

Synchrophasor measurement













































(V,I) (V,I)

 



PMU













 



































Standard measured values



Measured values, extended: min, max, medium



Switching statistic

















CFC standard

















CFC arithmetic



CFC switching sequences for control applications



Inrush current detection

















External trip initiation

















Control

















Fault recording of analog and binary signals

















Monitoring and supervision

















Protection interface, serial

















Circuit breaker

















Disconnector/Grounding conductor

















0

50

30

40

0

30

30

Function points

The configuration and function points for your application can be ascertained in the SIPROTEC 5 order configurator under: www.siemens.com/protection Table 3  7UT87 Functions, application templates 20 SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

Description of the Device Functions Functional integration, protection Functional integration Due to the modular design of its hardware and software and the powerful engineering tool DIGSI 5, SIPROTEC 5 is ideally suited for protection, automation, measurement and monitoring tasks in the electrical power systems. The devices are not only pure protection and control equipment, their performance enables them to assure functional integration of desired depth and scope. For example, they can also serve to perform monitoring, phasor measurement, powerful fault recording, a wide range of measurement functions and much more, concurrently, and they have been designed to facilitate future functionality expansion. SIPROTEC 5 provides an extensive, precise data acquisition and bay level recording for these functions. By combining device functionality with communication flexibility, SIPROTEC 5 has the ability to meet a wide range of today's applications as well as the functional expansion capability to adapt to changing needs in the future. With SIPROTEC 5 you can improve the safety and reliability of your application. Fig. 13 shows the possible functional expansion of a SIPROTEC 5 device.

Table 1,2 and 3 give an overview of the protection functions available in the respective devices. Hereby, the transformer differential protection accesses the function library of the SIPROTEC 5 family, so that the individual functions have perfectly identical properties and parameters. Thus, you will orient yourself easily and fast in the SIPROTEC 5 family. In the transformer differential protection, a range of selected protection functions is available for application. Faster results with application templates: Application templates allow you to fast track your solution. A suitable template can be selected from a library of predefined application templates containing the specific functional scope for typical applications and the necessary logical operations. For each device a table gives an overview of the respective protection functions and pre-configured application templates. Adapting the application template to your specific application: You can adapt the application templates to your applications and create your own in-house standards. Additional functions can be loaded into the device directly from a comprehensive function library. Since the functions conform to a common design structure throughout the SIPROTEC 5 system, protection functions and even entire function groups including parameterization can be copied from one device to another. The short descriptions of the available functions are provided hereafter.

SIPROTEC 5

Transfromer differential protection (ANSI 87T) 52

Control Automation Monitoring Data acquisition and Recording Communication Cyber Security Test

The transformer differential protection is a selective short-circuit protection for power transformers with different types of design (standard transformers and autotransformers) and different connection designs. The number of protectable windings (sides) and the number of usable measuring points depends on the device type (see above explanations). The following properties are essential for the protection function: •  Restraint tripping characteristic with freely settable characteristic sections in accordance with Figure 14 Integrated adaptation to the transformer ratio with different rated currents of the current transformer (primary and secondary) taken into account •  Flexible adaptation to the different transformer vector groups •  Additional consideration given to neutral point currents with grounded winding and thus increase of the sensitivity by one third

Fig. 13 SIPROTEC 5 - Functional integration

Protection SIPROTEC 5 provides all the necessary protection functions to address reliability and security of power transmission systems. System configurations with multiple busbars and 1 1/2 circuit-breaker layout are both supported. The functions are based on decades of experience in putting systems into operation, including feedback and suggestions from our customers. The modular, functional structure of SIPROTEC 5 allows exceptional flexibility and enables the creation of a protection functionality that is specific to the conditions of the system while also being capable of further changes in the future.

•  Redundant stabilization procedure (2nd harmonic + curve wave analysis) to detect safely inrush procedures at the transformer •  Further stabilization options through the evaluation of the 3rd or 5th harmonic in the differential current. The 5th harmonic is suitable for detecting safely a steady-state overexitation of the transformer and thus for avoiding an overfunction •  Additional stabilization procedures against external faults with current transformer saturation. The first procedure responds to high-current faults and monitors the differential current curve (differential current detected outside the add-on stabilization characteristic for a limited time, see Figure 14). Changeover to an internal fault is safely detected.

SIPROTEC 5 – Transformer Differential Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1 21

Description of the Device Functions Protection The second procedure works with low-current faults. Phaseangle shifts can occur in the secondary current due to the DC component in the short-circuit current and remanence of the current transformer. If jumps occur in the stabilization current and if DC components are detected in the differential current at the same time, the tripping characteristic is increased for a limited time.

Idiff

_:11071:3

•  If asynchronous motors are connected to transformers, differential currents can occur due to the distorted transmission of the starting current. The start detection (jump in the stabilization current and DC component evaluation) will raise the tripping characteristic. •  High-power internal faults are detected safely and quickly with the high-current stage Idiff-fast (see Fig. 15). In order to avoid an overfunction due to q-axis currents (e.g. use in 1 1/2 circuit-breaker layout), the instantaneous values of the differential and stabilization current are evaluated. Internal and external faults are safely detected within few milliseconds.

Irest

Fig. 15 Characteristic of the function IDiff fast

The protection function was adapted to the special conditions of the autotransformer in order to ensure the protection of autotransformers. The pure node point protection can be used as an additional sensitive protection of the autotransformer winding. The node point protection works parallel to the classical differential protection. The autotransformer banks become highly sensitive to ground faults and interturn faults with it. Figure 16 shows the basic idea.

p MP I-3ph 1

87 t

MP I-3ph 2 MP I-3ph 3

Fault characteristic fed from one side

s

87Node

MP I-3ph 4

7 6

87 Differential protection 87Node Differential protection auto transformer MP Measuring point

_:11041:102 P

5

0.7

4

Fig. 16

3 2

_:11041:100 P

_:11041:3

0.3

1

Additional stabilization external fault

P 1

2

3

_:11041:101

4

5

6

7

8

9

10

11

_:11041:103

P

P 2.5

0.67

_:11041:128 P 2.0

Fig. 14

Restraint tripping characterisitc of the function IDiff

Differential ground-fault protection (87N T) Irest I/Irated

Visio-DwDifAus-_us

0.2

Protection of an autotransformer through two differential protection in one device

Ground faults close to the neutral of a grounded neutral winding can be detected by the longitudinal differential protection only to a limited extent. The ground fault differential protection will support you here. The neutral point current and the calculated zero sequence of the phase currents are evaluated in accordance with figure 17. An overfunction in the case of external ground faults is avoided with special stabilization measures. The phase angles of the zero sequence are monitored in addition to the differential current and stabilization current based on the zero quantities. The tripping quantity is the zero sequence in the neutral point. When used in autotransformers an additional measure was taken to avoid malfunction in the case of external ground faults. The protection function determines independently the side of the autotransformer winding which is required for the safe operation of the protection function. The measuring point is selected which will lead to the highest stabilization current (see also Fig. 18). This procedure is also used if there are several three-phase current measuring points at the star side, such as in 1 1/2 circuit-breaker layout (see Fig. 18).

22 SIPROTEC 5 – Transformer Differentail Protection 7UT8 · Siemens SIPROTEC 5.04 · Edition 1

Visio-Spartrafobank

Idiff I/Irated

Visio-DwIDfast-170712

P

Description of the Device Functions Protection

A

IA

A

B

IB

B

C

IC

C

Other protection functions are provided in the differential protection devices. These functions can be used as additional protection and monitoring functions and as backup protection for the upstream or downstream network. Monitoring of limit values is also possible. Thermal overload protection (ANSI 49)

IY

SIPROTEC

Visio-DwGrdpri--us

I0* = IY

I0** = IC + IB + IA

|I0*| IChar 4

A current and thermal alarm stage is provided for the thermal overload protection to initiate an alarm before tripping. The tripping time characteristics are exponential functions according to IEC 60255-8. The preload is considered in the tripping times for overloads.

2

1

Circuit-breaker failure protection (ANSI 50BF)

90°

80° φ(I0*;I0**)

Visio-DwAusken--us

100°

The thermal overload protection calculates the overtemperature from the measured phase currents according to a thermal single body model. The true RMS value is determined per phase from the highly sampled measured current values (8 kHz). All quantities which cause heating are taken into account through the wide frequency operating range. Stages

3

110°

The thermal overload protection function protects equipment (overhead lines, cables, motors, generators and transformers) from thermal overstraining by monitoring the thermal conditions.

The circuit-breaker failure protection incorporates a two-stage design. If the fault current is not interrupted after a time delay has expired, a retrip command or the busbar trip command will be generated.

Bild 17 Basic principle ground fault differential protection

3I0'' 3I0''

M2 M1

The correct circuit-breaker operation is monitored via current measurement and via auxiliary circuit-breaker contacts. The current detection logic is phase-segregated. The circuit-breaker failure protection can be initiated by all integrated protection functions as well as by external devices via binary input signals or by serial communication with GOOSE indication in IEC 61850 systems. To increase operational reliability, an external start can be applied with two binary inputs in parallel.

M2 M1

NP

-T

The breaker failure protection is breaker-related in the function group circuit breaker. Each circuit breaker has to be provided with its own breaker failure protection.

3I0'

External trip initiation

Visio-DwFehler--us

External fault (M1 side) IAng, REFM1 = >0, Δφ_M1 = 180° IAng, REFM2 = 0 Q>0

3I0active (capacitive)

α1 α1

3I0

P P

_:107 _:102 _:105 _:106

P Backward P
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