Screened vs Unscreened Separable Connectors: Key Differences and Applications

Screened and unscreened connections are two of the most prominent connection types when it comes to medium-voltage power distribution. And for most engineers and electrical professionals, there's always a choice to be made when it comes to these two and the appropriate options for their projects.

But, which of these two works best? And when should you make a distinction? Let's look into both options in this article to answer these burning questions.

Understanding Screened (Shielded) Separable Connectors

In electrical connection guides, screened separable connectors are accessories for MV cables that are built with an external conductive screen. This screen covers the connector's entire body, providing a stable earth potential for the outer surface and providing a touch-safe build for it.

For most applications, you'll find that the added screen provides some core functionalities for the screened connector. These include:

• A touch-safe operation, which prevents any accidental contact with any live components by keeping the external surface at ground potential

• Equalizing any electric potential around the connector, so you can reduce the risk of partial discharge

• Allowing you to mount multiple screened connectors closely together

Screened connectors can come in two major designs, which are elbow connectors (Type A/B) and T-connectors. The elbow connectors are especially prominent for compact switchgear terminations and loadbreak applications, while you can find the T-connectors in deadbreak applications where you need to loop or branch multiple cable circuits.

What Are Unscreened Separable Connectors?

On the other side of the screened vs unscreened separable connectors debate, we have the unscreened connectors. Also used for MV cables, these connectors don't have that conductive outer screen in their designs. This pretty much means that their surfaces can expose energized components, and that adds a need for extra care when handling and installing.

Unscreened separable connectors are usually found in older MV systems, and they're mostly used in tools where you need controlled access for their installation environments.

A few key features of these connectors include:

• The need for insulation distances and air clearance, where the ocnenctors need to be installed away from other live components and grounded surfaces

• Mostly used in indoor and restricted-access areas where safety measures are implemented

• The presence of potential in the outer surface, making direct contact potentially dangerous

Screened vs Unscreened Separable Connectors: Key Differences

Now, let's move into the screened vs unscreened connectors guide. Both options are incredibly similar, but the differences in their makeup can cause a few distinctions. Let's see how they stack up against each other.

Overall Safety

When it comes to electrical connections, one of the most important factors is safety. And on this front, screened connectors take the edge.

The build of screened connectors comes with a conductive outer screen that keeps the surface at earth potential. This means that you can touch the surfaces, and the risk of accidental contact is also considerably lower.

Compare this to unscreened connectors, which can expose some energized parts. Working with them requires a lot of care, as well as distance to ensure proper safety.

Where They Are Installed

You'll mostly find screened connectors in indoor, compact installations. Think transformers, RMUs, substations, and the likes. In environments like there, you can mount multiple connectors together without having the fear of any danger.

For unscreeend connectors, we'd recommend having them in outdoor environments where you can have enough space and separation to reduce any hazard and optimize their lifespan.

Space Requirements for Installation

Screened connectors come with a more compact build that can easily be installed in dense layouts without affecting their safety profile. On the other hand, you will need additional air clearance and a considerable insulation distance for unscreened connectors.

So, if you're working in a confined space, you might want to choose screened connectors instead.

Testing and Fault Location

The design of screened connectors makes them safer and easier for testing. They have outer surfaces that can be touched, and this design also reduces the risk of partial discharge.

Of course, this isn't to say that you can't test unscreened connectors as well - you just need to make sure to implement proper safety measures and avoid contact with any live parts.

Cost Considerations

If, like most professionals, you're concerned with cost, then you might want to go for unscreened connectors. The screened variants are usually more expensive, thanks mostly to the added conductive screen and a few other material options.

That said, we won't recommend making your choice based on the cost alone. As we've mentioned already, unscreened connectors usually come at a higher safety risk, and they're mostly built for older systems. So, there are cons to this as well.  

Applications and Typical Use

Screened connectors are commonly used in modern installations like indoor RMUs, pad-mounted transformers, and compact substations, particularly in areas with human activity. Unscreened connectors are more common in older installations, outdoor substations, or specific equipment types where controlled access is ensured.

Voltage Range and Designs

Both screened and unscreened connectors are usually rated for systems between 6kV and 36kV. You can find screened connectors in elbow and T-connectors, which are ideal for compact layouts. On the other hand, the design for unscreened connectors is usually simpler since they mostly come with older systems.

Screened vs Unscreened Separable Connectors: General Applications

Applications of Screened Separable Connectors

As we've mentioned, screened connectors are used mostly for their safety and reliability. Professionals also appreciate their compact installation, which makes them great for specific applications such as:

• Work in RMUs and compact substations, where you need to put multiple connections together

• Outdoor switchgears, where you need touch-safe applications

• Industrial plants that need optimal reliability and access to energized components

• Pad-mounted transformers and other types of enclosed switchgear

• Interconnections for solar and wind farms, where you need reliability and environmental exposure

• Underground cable networks, as well as dense urban distribution centers

Applications of Unscreened Separable Connectors

As for the unscreened connectors, you mostly use them in installations where you can manage safety by maintaining your distance and access. A few of these applications include:

• Older substations built before the advent of screened technology

• Installations with enough distance between energized parts

• Low-contamination indoor environments where you don't need to worry so much about touch safety

• Equipment built for unscreened interface bushings, as these are more compatible with the connectors

How to Choose Between Screened and Unscreened Connectors

So, now that you understand how both connectors stack up against each other, let's examine a few things that you can consider when choosing between them overall:

Consider the installation environment

First, you want to determine where you're installing the connectors as well as the level of access control. Screened connectors work well for indoor environments, but we won't recommend using unscreened connectors anywhere indoors.

Always prioritize safety and operator access

If the installation area is sensitive and accessible, then screened connectors are the ideal choice. The last thing you want is accidental access, so always keep safety above anything else

Will you need enough space?

Screened connectors work better for compact installations where you don't have much space. On the other hand, we'll only recommend working with unscreened connectors if you're installing them in an area with enough space available.

What's the equipment interface type?

Look into the compatibility of the connectors. For instance, screened connectors usually make use of Type A/B/C interfaces, while the unscreened connectors work better with older standards.

Conclusion

Screened and unscreened connectors are similar in many ways. However, the difference in their build can easily make all of the difference when you consider them as well.

To make the right choice, remember to follow our guidelines and prioritize safety and efficiency above all else. If you'd like any more assistance, feel free to contact us at Haivol Electrical.