Pluggable solutions have always been the preferred option for complex systems in which the power supply feeds multiple control cabinets. Phoenix Contact offers a range of solution that is complemented by a high-performance, pluggable terminal block that simplifies the power supply and the concatenation of complex systems.

Monitoring and controlling switching states and measured values in switching systems, local power supply stations, and infeed points is becoming increasingly important in smart grid technology. Control rooms need the current relevant switching states and measured values, particularly in decentralised power generation. Since low-voltage control cabinets in modern switching systems have limited space, simple and compact solutions are in high demand (Figure 1, lead image).

In Germany, the energy mix components are currently changing in a highly dynamic manner. The new German Renewable Energy Sources Act (EEG), which has been in effect since 1 January 2012, stipulates that, when future grid overloads are imminent, grid operators are able to pull the emergency brake and reduce the power supply at critical points to 60, 30, or even 0%. By the end of 2013, all operators of installations having a power output of 30kWp or greater must be able to implement this requirement via a ripple-control signal. Active intervention into the grid requires reliable monitoring of the loading conditions at the medium- and low-voltage levels. Switching systems are an important link in the chain for accomplishing this objective.

Four-level terminal blocks save space

Many sensors, current and voltage transformers, and actuators are used to record measured data and control the switching states. Remote monitoring permits detailed grid monitoring and control, which is an important step toward achieving a smart grid. The control cabinets, particularly the low-voltage cells in the switching systems, must reflect this enhanced functionality. System operators working at critical nodes or under difficult environmental conditions sometimes even require a redundant configuration in the control cabinet. However, this reduces wiring space, which sometimes makes it also necessary to install multiple-level terminal strips on cross beams. Wiring is thus becoming increasingly challenging for design engineers and planners.

Multiple-level wiring is now possible for applications that up until now have used one-level terminal blocks. With the new four-level Clipline complete line of terminal blocks (Figure 2), single-row terminal strips now occupy only a quarter of the space previously needed.

Three-dimensional signal routing

The new four-level push-in terminals have simple labeling and three-dimensional signal routing capability to facilitate bridging and maintain a clear arrangement. These features reduce the effort required for connecting signals by half. The x-axis connects the push-in connection contact to one or both plug contacts inside the terminal block. Signal connections along the bridge shafts connect to any adjacent terminal blocks on the y-axis at any level. Finally, the z-axis – and this is new – connects vertically between the levels using a flexibly pluggable vertical bridge. It is thus possible simply to plug a connection in all three dimensions.

Connections that cannot be made linearly are routed in a crisscross fashion and disappear as wiring in one of the plugs, which can be capped with a cover (Figure 2). These plugs have additional advantages compared to single-row terminal strips. The internal system wiring can be laid entirely on preconfigured, multi-pin, pluggable cable harnesses, which then only have to be plugged into their slots during installation. Alternatively, the slots are also suited for the final inspections on a production line or for test purposes during servicing. Users benefit every time they use the push-in contact to make a quick wiring connection without the need for tools. Orange-coded pushers prevent incorrect connections, and optional flanges ensure safe assembly and provide adequate space to label the connection diagram.

The four-level terminal blocks are the first to make it possible to transfer the functions of the one-level design completely onto the multiple levels using modern push-in technology and efficient verifiability.

Mechanically specified switching operations for greater safety

For some time now, Phoenix Contact has been offering its ME line of switchable terminal blocks with screwless separation points and plug-in jumpers for compact converter wiring. These devices have met the needs of many customers for more serviceability and clearer arrangement through the use of imprinted switching symbols and easy-to-identify, mechanically hinged switches. Neutral points and grounding can be easily implemented using plug-in jumpers. The new terminal blocks (Figure 3) provide systems engineers with additional options through a higher degree of decentralized production, higher modularity and pluggability, and preassembled cable harnesses. While mass production earlier made progress here, converter applications generally did not. There was too much skepticism with regard to forgotten or unclosed short-circuit jumpers and prewired current transformer sets. Pluggability represented more of a red flag than a solution.

Despite this, or perhaps because of it, the market requires new optimized solutions for this area. A new generation of pluggable transformer terminals (Figure 4) creates a leading short circuit in the plug using the plug-in and removal operation. The current transformer can be operated without risk with an unconnected plug, since the required short circuit is created internally by the mechanical design. This technology, which was developed by Phoenix Contact, is already used with smaller cross sections for meters, for example, in meter exchange panels. This functionality is now also available for switching systems and other measurement tasks requiring a 6 mm² connection.

Pluggable power supplies for modular system designs

Pluggable solutions have always been the preferred option for complex systems in which the power supply feeds multiple control cabinets. The bottleneck was usually created by the limited voltage and current ratings of the pluggable contacts. The “Combi” terminal block system from Phoenix Contact offers a new approach. The key figures for the pluggable power transfer are a 6 mm² cross section, 41A, and 1000V rated voltage. A four-lead terminal block with two pluggable outputs (Figure 5) makes it easy to implement power supplies. The load circuits are connected to hard-wired contacts installed in the control cabinet ceiling or floor area. For the overall system installation, the individual cabinets are then supplied in a concatenated ring circuit from one plug to the next. The plugs also have an optional housing and are mountable to provide users with a simple, compact, rugged solution.

Summary

Modern switching system designs use new wiring solutions to meet market demands, providing multiple-level capability without compromising clear arrangement and flexibility. The new four-level terminal blocks are easy to use and service. Converter wiring has the potential for modular production designs and increased system availability. Thanks to pluggability with integrated, automatically leading short-circuit capability, plug and play is now suitable for practical application. The solution package is complemented by a high-performance, pluggable terminal block that simplifies the power supply and the concatenation of complex systems. All of this provides space and flexibility in the low-voltage cabinets of state-of-the-art switching systems.