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What Is a Screened Separable Connector and Where Is It Used in RMU, Transformer, Switchgear and GIS Systems
Introduction
Power networks today run underground. Cables are buried beneath streets, industrial facilities, and substations. When these cables connect to switchgear equipment, the connection point must be safe, compact, and easy to maintain.
This is where the screened separable connector becomes important. It is a purpose-built accessory that joins medium-voltage cables to enclosed switchgear, such as Ring Main Units (RMU) and Gas Insulated Switchgear (GIS). Understanding what it is and how it works helps electrical engineers and procurement teams make better decisions.
What Is a Screened Separable Connector?
A screened separable connector is a plug-in termination device used on medium voltage cables. It connects a power cable to the bushing or spout of a switchgear unit. The term separable means the connector can be plugged in and pulled out. The term screened refers to the continuous metallic or semiconductive shielding that covers the connector body.
This shielding is critical. It ensures that the electric field is contained within the connector at all times. There are no exposed energised surfaces when the connector is correctly installed. This protects both personnel and equipment.
The connector is made of several layers working together. The conductor carries the current. The insulation layer, usually made from EPDM rubber, provides dielectric strength. The outer screen maintains field continuity. Together, these layers form a termination that behaves as an extension of the cable itself.
How Does It Work?
The screened separable connector is pushed onto a matching bushing on the switchgear. The EPDM body creates firm, intimate contact.
When energised, the electric field is evenly distributed throughout the connector body. The screen on the outside keeps the field from radiating outward. This makes the connector safe to touch even when the system is live, as long as correct insulation is maintained.
Disconnection is equally straightforward. Engineers can remove the connector from the bushing to isolate a cable from the switchgear without de-energising the entire system in case of load-break separable connectors & in case of dead-break separable connectors the system needs to be de-energised first. This reduces maintenance downtime significantly.
The connectors are rated by voltage class. Common ratings include 12 kV, 24 kV, and 36 kV. They also carry current ratings that match the cable and switchgear specifications.
Use in RMU Cable Termination
A Ring Main Unit is a compact switchgear assembly used in urban and industrial medium voltage distribution networks. It typically has three to five cable connection points. Each connection point uses a screened separable connector for the RMU cable termination.
Think of a residential development where underground cables loop from one substation to another and tap off to serve each building block. The cables terminate in RMUs located in small kiosks or basement rooms. Each cable end uses a screened connector to plug into the RMU bushing.
The advantage here is space. RMUs are compact by design. A traditional heat-shrink or cold-applied termination would need significant space and preparation time. A screened separable connector takes up less room and can be installed or removed in minutes.
Maintenance teams working on distribution networks benefit greatly. If a cable fault is isolated to a single section, the connector in that section can be unplugged, and the rest of the network can continue to run.
Use in GIS Cable Termination
Gas Insulated Switchgear uses pressurised SF6 gas or alternative clean air mixtures inside sealed metal enclosures. GIS is used in high-density installations such as city centre substations, airports, hospitals, and data centres where space is at a premium.
GIS cable termination using screened separable connectors follows the same principle. The cable end is fitted with the connector. The connector is then pushed onto the GIS bushing. Because both the GIS bushing and the connector are fully insulated and screened, the junction remains safe and field-controlled.
In GIS applications, the connectors must also be compatible with the gas-tight enclosure. The bushing penetrates the GIS tank wall and provides an external plug-in interface. The screened connector attaches to this external point without compromising the internal gas environment.
GIS installations benefit from the plug-in design because they are often located in confined basements or underground vaults. Performing a traditional cable termination in such tight conditions would be difficult and time-consuming.
Key Benefits at a Glance
- Touch-safe design with continuous electric field screening
- Quick plug-in and pull-out operation without specialist tools
- Compact form factor suited to RMU and GIS enclosures
- Reduced installation and maintenance time on site
- Standardised interfaces allow interchangeability across brands
- Available in elbow and straight T-body configurations for different installations
Standards and Compatibility
Screened separable connectors are manufactured to IEC 60502, IS 13573, and CENELEC HD 629 standards. These standards define the dimensions, test requirements, and electrical performance criteria. A connector built to these standards will be compatible with any compliant switchgear bushing of the same voltage class.
This standardisation is important for network operators. It means they are not locked into a single manufacturer for spares or replacements. The interface remains consistent across the industry.
Conclusion
The screened separable connector is a compact yet critical component in modern medium-voltage power systems. It provides a safe, field-controlled connection between underground cables and switchgear such as RMUs and GIS equipment.
For RMU cable termination in urban distribution and GIS cable termination in confined substations, these connectors offer speed, safety, and operational flexibility. As power networks continue to move underground, the demand for reliable screened connectors will only grow.
If you are sourcing screened separable connectors or related cable accessories, explore PCA Technologies now.
FAQs
What is a Screened Separable Connector?
A Screened Separable Connector is a plug-in medium-voltage cable connector that provides insulation, screening, sealing, and a removable connection to equipment such as switchgear, transformers, RMUs, and GIS systems.
Where is a Screened Connector commonly used?
It is commonly used in RMUs, GIS panels, transformers, switchgear, substations, industrial plants, and renewable energy installations.
Why is it called separable?
It is called separable because the connector can be disconnected from the equipment bushing when required, without cutting the cable.
What is the role of screening in the connector?
The screening provides a conductive outer layer that improves safety, supports touch safe performance, and helps control the electric field around the connection.
Is a Screened Separable Connector suitable for both RMU and GIS Cable Termination?
Yes. It is widely used in both RMU Cable Termination and GIS Cable Termination because it offers compact installation, reliable insulation, and ease of maintenance.
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