Clēēr™ 600 A, 15kV Loadbreak Connector System: The new class of deadfront separable connectors
Release Date: April 12, 2012
As the size and scale of the electrical grid continues to grow, so does the increased demand for system reliability. One of the top priorities for utilities today is to provide uninterrupted service to their customers. In order to achieve this goal it is necessary to keep less of their systems off-line during operation, restoration, and expansion. This must also be accomplished while maintaining an emphasis on operator safety. In today’s underground distribution systems this can be quite challenging as utilities need to work around the limitations of the separable connectors available in the market.
While advanced technologies over the years for 200 A connectors have made things easier to keep customers on-line, 600 A separable connectors require complete de-energization of the system prior to operation or maintenance. In addition, with load requirements increasing, more utilities are adding 600 A circuits to their system – which at times can result in more system downtime. Let’s review the current deadfront separable connectors available and the benefits and limitations of each.
Dead-front Separable Connector Systems
There are three classes of dead-front separable connectors covered in IEEE Std 386™. They are the 200 A deadbreak, 200 A loadbreak, and 600 A deadbreak.
200 A Deadbreak Systems
The first dead-front separable insulated connector systems were of the 200 A deadbreak class. While a technological breakthrough when they were first introduced, 200 A deadbreak connectors have drawbacks which have made them nearly obsolete at most utilities in the United States today.
Operationally, deadbreak connectors limit the user because they cannot be separated while energized or while carrying load current. They also are somewhat more difficult to operate because they require threaded connections to hold the connectors together. The circuit must be confirmed to be de-energized prior to operating a deadbreak elbow. Therefore a visible break and/or visible ground are required prior to operation because deadbreak elbows have neither loadbreak switching nor fault-closure ratings.
How does one achieve that visible break and ground at the separable connector location? How does one know for certain the circuit is de-energized prior to operation? Most deadbreak connectors have capacitive test points, but these are not conclusive and should not be relied upon as they can easily give false de-energized readings. The IEEE Std 1215™ “Guide for the Application of Separable Insulated Connectors” gives the following warning: “A reading of no voltage from the test point should not be the only indication of a de-energized circuit obtained before touching the connector.
The above limitations of 200 A deadbreak connectors led to their eventual replacement by 200 A loadbreak connectors.
200 A Loadbreak Systems
200 A loadbreak systems address all the drawbacks of their 200 A deadbreak predecessors. 200 A loadbreak connectors can be operated while energized and carrying load current, are fault-closure rated, and do not require threaded connections or bails for mating. This makes the loadbreak design much faster and much safer. Even if one never intends to pull a 200 A connector energized, the ability to do so is always present in the event a line technician makes an error. The 200 A loadbreak connector is also less expensive than other rated switches such as under-oil loadbreak switches or pad-mounted switchgear.
600 A Deadbreak Systems
600 A deadbreak systems have the obvious advantage over 200 A deadbreak systems because the former has 3 times the continuous current rating (plus a 900 A overload rating). However, 600 A deadbreak systems have the same numerous safety and operational liabilities as 200 A deadbreak connectors. Utilities struggle with the 600 A deadbreak connector drawbacks today, just as they did with 200 A deadbreak connectors when they were prevalent on the system. Deadbreak is deadbreak. Visible break and/or visible ground are required before unbolting the connector and one cannot rely on the capacitive test point.
Deadbreak systems are widespread now because this is the only technology that has been commercially available at 600 A. Utilities have been dealing with the limitations because they have had no other options.
What is needed is a new 4th class of separable insulated connector: a 600 A loadbreak connector system. Utilities need connectors that can be separated safely without needing a visible break or visible ground, just like they have used regularly on their 200 A loadbreak systems for many years. It is conceivable that, in the long term, such a system could replace the 600 A deadbreak system and all of its safety and operational shortcomings similar to what 200 A loadbreak technology did for utilities many years ago.
In the past year, Cooper Power Systems introduced the first of this new class of separable connectors.
Introducing the 600 A, 15kV Class Clēēr Loadbreak Connector System
Like 200 A loadbreak connectors, this 600 A connector system can be operated while energized and carrying load current, is fault-closure rated, and does not require unbolting connections to separate. This makes this loadbreak connector much faster and much safer. Even if a utility chooses not to operate this 600 A connector energized, downtime is limited as disconnecting and reconnecting this connector is significantly faster than conventional 600 A deadbreak connectors. In addition, heavy cables do not have to be moved and terminations are not disturbed, eliminating the potential of re-installation errors. Safety is also improved as the loadbreak capability is always present in the event a line technician makes an error.
Separable insulated connector technology has come a long way since the introduction of the 200 A loadbreak elbow. This section introduces the 600 A loadbreak connector in its most basic configuration: Two hybrid 600 A loadbreak/deadbreak 2-way junctions connected by one C-shaped, live-line tool operable, removable connector called the LCN (Loadbreak Connector). The LCN mates with the loadbreak halves of the 2-way junctions as shown in Fig. 1. Standard 600 A deadbreak elbows connect cables to the deadbreak halves of the two hybrid loadbreak/deadbreak junctions. The connector system with mounting brackets and labeled components is displayed in Fig. 2.
Fig. 1. Line drawing of the 15 kV 600 A loadbreak connector shown without the brackets. Standard 600 A deadbreak elbows mated to two hybrid 600 A loadbreak/deadbreak 2-way junctions. The live-line tool operable C-shaped LCN connects the two junctions.
Fig. 2. Line drawing of the 15 kV 600 A loadbreak connector. Standard 600 A deadbreak elbows mate on the deadbreak sides of the two hybrid loadbreak/deadbreak junctions. The live-line tool operable C-shaped LCN connects the two junctions.
At the time of this writing, the basic 15 kV 600 A loadbreak connector is offered in two basic configurations: inline (shown in Fig. 3) and square (shown in Fig. 4).
Fig. 3. 600 A loadbreak connector system shown in the inline configuration with adjustable bracket and mated with 600 A deadbreak connectors.
Fig. 4. 600 A loadbreak connector system shown in the square configuration mated with standard 600 A deadbreak connectors.
The 600 A loadbreak connector system is the culmination of multiple breakthrough technologies in the field of medium voltage separable insulated connectors. Network vault applications for 600 A loadbreak connectors include replacement of vacuum switches or outdated oil fused cutout switches, or installed in line with them providing a visible open prior to performing maintenance. This is currently not achievable with vacuum or oil fuse cutout switches used today. Used in networks for separable splicing of long cable runs, they can provide a quick disconnect without the tedious task of disassembling terminations or cable joints requiring special tools. In sectionalizing cabinets on underground distribution systems they provide a convenient means of isolating circuits to perform maintenance and when used with fused loadbreak elbows provide a practical less expensive alternative for some switchgear applications. In the long term this system has the potential to replace 600 A deadbreak, just as 200 A loadbreak has largely replaced 200 A deadbreak separable connectors in the United States...for all the same reasons.
600 A loadbreak separable insulated connectors have the potential to form the backbone of future network and distribution 600 A systems.
Download the 15 kV 600 A Loadbreak Dead-front Separable Insulated Connector System white paper that includes detailed information regarding the technology described in this article.
Contact your Cooper Power Systems representative for additional information regarding our Clēēr loadbreak connector system and benefits – and learn how you can use this solution to accomplish your utility maintenance requirements.
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