Low voltage switchgear and controlgear assemblies are defined as assemblies that include devices for switching, protecting, and controlling electrical circuits and equipment at low voltage levels, typically below 1,000 V AC or 1,500 V DC.(Refer figure 1)
Control and switchgear panels in substations are assemblies of control devices, instruments, and monitoring equipment. They are used to control and manage electrical power systems, ensuring safe, reliable, and efficient operation. Control panels can include a variety of components, such as circuit breakers, relays, meters, switches, and communication interfaces. Their primary function is to provide operators with the means to monitor system parameters
Key Functions include
- Control: Regulating electrical flow to various equipment and systems.
- Protection: Safeguarding circuits against overloads, short circuits, and other electrical faults.
- Isolation: Providing safe disconnection of electrical equipment for maintenance or emergency situations.
- Distribution: Distributing electrical power to different loads in an efficient manner.
Common components found in low voltage switchgear and controlgear assemblies include:
- Circuit Breakers: Devices that automatically interrupt the flow of current in case of a fault.
- Contactors: Electromechanical switches used for controlling power circuits.
- Relays: Devices that control circuits based on input conditions.
- Busbars: Conductors that distribute power to multiple circuits.
- Fuses: Safety devices that protect circuits from overcurrent conditions. A typical switchgear and controlgear assembly in the substation is shown in figure 2.
Relevant Standards for Lv S&C Assemblies
Several standards govern the design, manufacturing, testing, and application of low voltage switchgear and controlgear assemblies. The most significant standards include:
IEC 61439 Series
The IEC 61439 series is the primary international standard for low voltage switchgear and controlgear assemblies, consisting of multiple parts:
- IEC 61439-1: General Rules This part outlines the general requirements and definitions applicable to low voltage switchgear assemblies. It covers topics such as design verification, performance characteristics, and documentation requirements.
- IEC 61439-2: Power Switchgear and Controlgear Assemblies This part provides specific requirements for power switchgear assemblies, including design, construction, testing, and performance criteria.
- IEC 61439-3: Distribution Boards for Electrical Installations This standard specifies requirements for distribution boards, focusing on safety, functionality, and performance.
- IEC 61439-4: Assemblies for Power Distribution in Public Networks This part outlines requirements for assemblies intended for public electrical distribution systems.
- IEC 61439-5: Assemblies for Power Distribution in Industrial and Commercial Installations This standard addresses requirements for assemblies used in industrial and commercial applications.
- IEC 61439-6: Assemblies for Low-Voltage Motor Control Centers This part specifies the requirements for motor control centers, including design and testing criteria.
- IEC 61439-7: Assemblies for specific applications such as marinas, camping sites, market squares, electric vehicle charging stations
IEC 60947 Series
The IEC 60947 series covers low voltage switching and control devices. Key components relevant to switchgear and controlgear assemblies include:
- IEC 60947-1: General Rules
- IEC 60947-2: Circuit Breakers
- IEC 60947-3: Switches and Disconnectors
These standards provide essential information on device performance, safety, and testing methods.
IEC 60204-1: Safety Of Machinery
This standard addresses electrical equipment of machines, providing safety requirements and guidelines that are often applicable to controlgear assemblies used in industrial environments.
IEC 61000: Electromagnetic Compatibility (EMC)
Critical for ensuring that devices meet regulatory requirements for operation in various environments without causing or being affected by electromagnetic interference.
IEC 60529: Degrees Of Protection
This standard specifies the degrees of protection provided by enclosures for electrical equipment against the ingress of solid foreign objects and moisture. It is useful in selecting enclosures for equipment based on environmental exposure.
IEC 60439 Series
IEC 61439, specifies requirements for low-voltage switchgear and controlgear assemblies. Compliance with these standards ensures products meet safety and performance regulations.
IEC 60255
This standard covers the measuring relays and protection equipment. It specifies the general requirements for the performance, testing, and reliability of relays used in electrical protection and control systems.
Iso 9001: Quality Management Systems
While not specific to electrical assemblies, ISO 9001 sets forth criteria for quality management systems. Compliance with this standard can enhance the reliability and quality of switchgear and controlgear assemblies.
Verification for Reliability & Safety
IEC 61439-1 is part of a broader set of standards aimed at ensuring the reliability and safety of electrical assemblies. The standard defines the requirements for design verification, which confirms that the assembly has been designed to meet specified requirements, including thermal, mechanical, electrical, and dielectric performance.
Importance of Verification
Verification is crucial for ensuring the integrity and safety of electrical systems. It helps in:
- Safety Assurance: Reduces the risk of electrical hazards.
- Regulatory Compliance: Ensures compliance with national and international regulations.
- Performance Consistency: Verifies that products perform as intended under specified conditions.
- Customer Confidence: Builds trust in the manufacturer’s quality assurance processes.
To be continued…
Dr. Rajesh Kumar Arora obtained the B. Tech. & Master of Engineering (ME) degrees in Electrical Engineering from Delhi College of Engineering, University of Delhi. He completed his PhD in grounding system design from UPES, Dehradun. He is also certified Energy Manager and Auditor. Among others, he has worked in 400kV and 220kV Substations for more than 14 years in Delhi Transco Limited (DTL). Presently he is working in D&E (Design and Engineering) Department of DTL. His research interests include high voltage technology, grounding system, protection system, computer application and power distribution automation.
