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Siemens Low-voltage – Power distribution
Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses

Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses

Product catalog summary

Preface: The document introduces Siemens' low-voltage circuit protection technology, emphasizing the importance of protecting electrical equipment against overload and short circuits. It serves as a guide for selecting appropriate fuses and switch disconnectors to ensure safe electrical systems.

1. Introduction to Electrical Protection: This section highlights the necessity of protecting electrical equipment from overloads and short circuits using suitable devices that automatically disconnect faulty circuits. It stresses the importance of preventing negative effects associated with electrical overloads and ensuring personal protection against electric shocks.

2. Technical Basics: This section covers the fundamental technical aspects of switch disconnectors and fuses.

2.1. Certification and Approval: Discusses the regulatory standards for electrical equipment, including IEC, EN, DIN, VDE, UL, and CSA, ensuring safety and compliance in different regions.

2.2. Utilization Categories: Defines utilization categories for switch disconnectors and fuses, which guide users in selecting appropriate devices based on their intended use and load requirements.

2.3. Selectivity: Explains the concept of selectivity in electrical systems, where only the protective device closest to a fault should trip, maintaining energy supply to unaffected circuits.

2.4. Basic Principles of a Fuse: Covers the design, function, technical specifications, and characteristic curves of fuses, essential for understanding their operation and application.

2.5. Basic Device Types and Application Examples: Describes various types of switch disconnectors and their applications, including those with fuses and transfer switching equipment.

3. General Technology Comparison: Compares fuses and circuit breakers, highlighting their respective advantages and applications.

4. Siemens Product Portfolio: Details Siemens' range of switch disconnectors, fuses, and transfer switches, including specific product lines like 3LD, 3KD, and 3KC.

5. Application Example: Provides a practical example of how Siemens products can be applied in electrical systems.

6. Appendix: Defines key features such as rated voltages, currents, and characteristics under load and short-circuit conditions.

Overview: The document provides a detailed analysis of the selectivity and functionality of fuses and circuit breakers, focusing on their application in electrical systems. It discusses the principles of selectivity, the design and function of fuses, and the types of switch disconnectors used in various applications.

Selectivity in Electrical Systems: Selectivity ensures that only the faulty section of an electrical system is disconnected during a fault, minimizing disruption. The document explains that selectivity is achieved when the current does not exceed the limit set by the combination of switching devices. Fuses are simpler to use for selectivity due to their parallel time-current characteristics, while circuit breakers require more complex considerations.

Fuses: Fuses protect against overcurrent and short circuits by melting a fuse element to interrupt the current flow. The document outlines different designs of fuses, such as LV HRC, cylindrical, and NEOZED/DIAZED fuses, and explains their construction and operation. It highlights the current-limiting effect of fuses, which reduces damage and danger during overcurrent events.

Fuse Characteristics and Standards: The document details the operational classes of fuses, indicating their application areas. It explains the time/current characteristics that determine when a fuse will blow, emphasizing the importance of understanding these characteristics for proper application. Various standards and codes for fuses are discussed, including those for specific applications like motor circuits and semiconductor protection.

Switch Disconnectors: Different types of switch disconnectors are described, including those with and without fuses. These devices are used for switching and protection in electrical systems. The document provides examples of applications for each type, such as emergency-stop switches, power distribution, and machinery protection.

Transfer Switching Equipment: The document briefly mentions transfer switches, which are used for switching between power sources or loads. It distinguishes between manual and motor-driven switches, highlighting their use in applications where power supply continuity is critical.

Overview of Transfer Switching Equipment: Transfer switching equipment (RTSE and ATSE) is designed for switching between two power sources, either manually, remotely, or automatically. RTSE allows remote control switching, while ATSE includes a control unit for automatic switching based on voltage or frequency changes.

Application Examples:

Switching between networks for critical loads like emergency power.
Manual switching to alternative power sources for maintenance.
Switching one feed-in to different loads.
Reversing motor direction.

Types of Transfer Switches: Transfer switches are categorized into load switching (one supply source) and transfer switching (two supply sources). They can be operated manually, remotely, or automatically, with options for integrated protection functions.

Selection Criteria for Switchover: Selection depends on load criticality: critical loads require automatic transfer switches, while important loads may use manual or remote switches. The sensitivity of loads also influences the choice, with highly critical loads needing uninterrupted power supply.

Comparison: Fuse vs. Circuit Breaker: Fuses offer good current-limiting capability and low costs but require longer outage times and qualified staff for replacement. Circuit breakers provide adjustable protection and quick commissioning but are more expensive and have higher power loss.

Siemens Product Portfolio: The portfolio includes various switch disconnectors, fuse systems, and transfer switching equipment. Key products include:

3LD and 3KD switch disconnectors for safe switching in industrial applications.
LV HRC, SITOR, cylindrical, and DIAZED/NEOZED fuses for different protection needs.
3NP fuse switch disconnectors for all-pole switching with integrated protection.

Overview: The document provides a detailed overview of various electrical components used in infrastructure and industry, focusing on low-voltage switchgear, motor control centers, and distribution systems. It emphasizes safety, compact design, and functionality.

1. LV HRC Fuse System: This system is designed for diverse electrical loads, offering high system protection and personal safety. It supports fuse sizes from LV HRC 000 to LV HRC 3 and includes integrated fuse monitoring for fault detection.

2. 3NJ4 Fuse Switch Disconnectors: These devices combine load switching and disconnection functions, suitable for low-voltage distributions in industry. They offer versions with integrated current transformers and electronic fuse monitoring.

3. Switch Disconnectors with Fuses: These are used for load protection and switching, offering higher switching capacity compared to fuse switch disconnectors. The 3KF and 3NJ6 models are highlighted for their compact design and flexibility.

4. Load Transfer Switches and Transfer Switching Equipment: These switches facilitate switching between different loads or power networks. The 3LD load transfer switches and 3KC transfer switching equipment are discussed, with options for manual, remote, and automatic operation.

5. Application Example: A schematic structure is provided, illustrating the integration of various components like 3WL, 3VA, and 3KD in a Siemens portfolio.

6. Appendix: Key features of switch disconnectors, fuse switch disconnectors, and transfer switches are defined according to IEC 60947-3 standards, including rated voltages and currents.

Specifications:
The document outlines key specifications for electrical devices, including operational voltage, rated frequency, rated load, utilization category, and ambient temperature. It emphasizes the importance of the rated uninterrupted current (Iu), which is the maximum permissible current for continuous operation under defined conditions.

Load and Overload Features:
Devices are designed to withstand motor switching overload currents, ensuring they are overload-proof. The rated making capacity is the maximum current a device can switch on, while the rated breaking capacity is the maximum current it can switch off, both dependent on utilization category and operational voltage.

Short-Circuit Conditions:
The document details the rated short-time withstand current (Icw), indicating thermal strength under short-term loads. The rated short-circuit making capacity (Icm) and breaking capacity (Icn) describe the maximum short-circuit currents a device can handle without damage. The conditional rated short-circuit current (Ig) is the prospective current a device can disconnect with a back-up fuse.

Additional Information:
Published by Siemens AG in 2020, the document includes a disclaimer about the availability of technical options and advises defining required features on a case-by-case basis. Comprehensive support is available through Siemens' online resources.

Catalog excerpts

Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses

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Contents Preface List oftables 1. Introduction to electrical protection 8 2.4. Basic principles of a fuse 18 2.4.2. Function, technical specifications, and characteristic curves 19 2.5. Basic device types and application examples 26 2.5.2. Switch disconnectors with fuses 28 2.5.3. Fuse switch disconnectors 30 2.5.4. Transfer switching equipment or load transfer switches 32 2.6. Basic principles of switchover 34 2.6.1. Types of transfer switches 34 2.6.2. Selection criteria for switchover 37 3. General technology comparison: Fuse versus circuit breaker 40 4. The Siemens product portfolio for switch...

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-3

4.2.4. DIAZED/NEOZED fuses 4.3. Fuse switch disconnectors 4.3.1.3NP fuse switch disconnectors 4.3.2. 3NJ4 fuse switch disconnectors 4.4. Switch disconnectors with fuses 4.4.1.3KF switch disconnectors with fuses 4.4.2. 3NJ6 switch disconnectors with fuses 4.5. Load transfer switches and transfer switching equipment 4.5.1. 3LD load transfer switches 4.5.2. 3KC transfer switching equipment 4.5.2.1.3KC0 manual transfer switching equipment (MTSE) 4.5.2.2. Transfer switching equipment with motor operator 4.5.2.2.1.3KC3 and 3KC4 remote transfer switching equipment (RTSE) 4.5.2.2.2. 3KC6 and 3KC8 automatic...

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-4

SENTRON Technology Primer | Preface Preface According to the requirements outlined in international standards and installation regulations (e.g. fire protection or escape stairs), electrical equipment must be effectively protected against overload and short circuits. Protection, switching, measuring, monitoring or power monitoring – Siemens low-voltage circuit protection technology offers a broad portfolio of devices and software solutions for all areas of electrical installation technology. This puts you in full control of all electric circuits – in industry as well as in non-residential and...

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-5

Table of Abbreviations | SENTRON Technology Primer ATC automatic transfer control device ATSE automatic transfer switching equipment CCC China Compulsory Association DC direct current fur Normung e.V. EN European standard I electrical current intensity Commission IEV International Electrotechnical LRS Lloyd's Register of Shipping MCC motor control center MCCB molded case circuit M effect mesomeric effect MTSE manually operated transfer switching equipment N neutral conductor NEC National Electrical Code NEMA National Electrical Manufacturers Association NFPA National Fire Protection Association...

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-6

SENTRON Technology Primer | List of Figures List of figures Figure 1: IEC and UL markets at a glance 11 Figure 2: Selective system vs. non-selective system 14 Figure 3: Combination of characteristic curves for full selectivity 16 Figure 4: Combination of characteristic curves for partial selectivity 17 Figure 5: Structure of a fuse (example: LV HRC fuse) 19 Figure 6: Short-circuit current limiting 20 Figure 7: Characteristic curve for gG, gR and gS 23 Figure 8: Time/current characteristic 25 Figure 9: Switch disconnectors as EMERGENCY-STOP, repair or main control switch of machinery and plants...

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-7

List of Tables | SENTRON Technology Primer Figure 12: Transfer switches for switching over between networks or loads 33 Figure 13: Types of transfer switches 34 Figure 14: Transfer switching with switch disconnectors and circuit breakers 35 Figure 15: Exemplary structure of transfer switching considering the criticality of the loads 38 Figure 16: Schematic application structure 58 List of tables Table 1: Utilization categories for switch disconnectors and fuse technology 13 Table 3: Operational classes and applications 22 Table 4: Comparison of fused solution and circuit breaker solution 40

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-8

SENTRON Technology Primer | Introduction to Electrical Protection 1. Introduction to electrical protection When dealing with electricity, safety has top priority. According to the requirements outlined in international standards and installation regulations, every qualified electrician must effectively protect electrical equipment, in particular cables and conductors, against overload and short circuits by implementing suitable (protective) measures. Preferably, such protection is achieved with the use of suitable switching/protective devices, which will automatically disconnect defective circuits...

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-9

Technical Basics | SENTRON Technology Primer 2. Technical basics Various factors play a decisive role in the selection of the right switching and protection device. First and foremost is the choice of a basic device from the various switch disconnectors, fuse switch disconnectors, switch disconnectors with fuses and changeover switches. In the next step, the technical data and specifications are most relevant. For better understanding, these key features are explained in more detail in the appendix. Finally, it must be ensured that the approval requirements of the respective country or area of...

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-10

SENTRON Technology Primer | Technical Basics 2.1. Certification and approval The use of electrical equipment for switchgear and controlgear assemblies is regulated by the legislation of the corresponding country. The most important technical features of low-voltage fuses and switchgear are codified in the standards of the International Electrotechnical Commission (IEC) based in Geneva. Even beyond Europe, devices in accordance with the IEC standard are used in Asia, South and Central America and Australia. The European standards (EN) are generally identical to those of the IEC. In some cases,...

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-11

Technical Basics | SENTRON Technology Primer Figure 1: IEC and UL markets at a glance

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Switch disconnectors Technology primer Protecting, switching and disconnecting with switch disconnectors and fuses-12

SENTRON Technology Primer | Technical Basics 2.2. Utilization categories Utilization categories are a “combination of specified requirements related to the condition in which the switching device or the fuse fulfills its purpose, selected to represent a characteristic group of practical applications” (International Electrotechnical Vocabulary – IEV 441-17-19). Utilization categories subdivide the various switching tasks (applications), whereby there are different test conditions for each category. Utilization categories provide the user with orientation in the selection of low-voltage controlgear...

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