Table of Contents

4. Dimensioning of a cluster

When selecting the cluster configuration and cluster master it is important to know that with INCH Duo can handle power management of up to 36 electric vehicles. This is valid for the most unfavourable scenario with low power capacity available, meaning constant need for power management recalculations with inclusion of data obtained from Load Guard. INCH Duo could also control larger clusters, depending on the individual case.

Larger cluster (supply of up to 300 electric vehicles in most unfavourable scenario) is possible with use of industrial computer and connection to Etrel Ocean management software.

Main decision factor in cluster configuration is usually the available charging power at the location. Cluster of charging stations can be planned and configured to allow charging with maximal power to all connected vehicles. Another option is to plan to the limitation of capacity intended for charging and to maximal charging current of the cluster.

When a larger number of parking spots need to be covered with charging stations, the general proposal is to have a dedicated parking spot for each charging connector that can offer at least charging with minimum current of 6 A to connected electric vehicle.

For example:

1. Five INCH DUO charging stations can be configured to be able to charge with maximal charging current of 32 A per phase, per each charging spot. Five INCH DUO charging stations have 10 charging spots, with maximal charging current of 320 A per phase, meaning that maximal charging power is 220,8 kW.

2. Five INCH DUO charging stations can also be configured to be able to charge only with minimal charging current of 6 A per phase. These five INCH DUO charging stations will have maximal charging current of 60 A per phase, meaning that maximal charging power is 41,4 kW.

Normally the cluster is dimensioned for available power and power management limits the total current of the cluster to allowable levels. Also, possible future upgrades should be considered and could lead to decision to install cables with larger cross-sections.

In case of very large clusters and long distances, possible dedicated power transformers could be needed to provide low enough voltage drop.

Cabling Route for the Connection of Multiple Charging Stations

Charging station can be installed independently or combined in connection with other stations (the so-called clustering of charging stations).

When multiple charging stations are installed in a single area, the power supply cables can be routed in several different ways. The physical connection of a group of charging stations can be different than the setting of software grouping.

It is recommended, that the charging stations logically belonging to one cluster are also physically connected to the same cluster with common point of power supply.

The main reason would be possible power management of the cluster and limitation of charging power on basis of set and measured data. Also, avoidance of possible confusion during the maintenance or troubleshooting.

Cluster can be defined only on level of charging stations where one charging station is designated as cluster master. They can also be managed from charging infrastructure management system.

Power Cables Star network topology

Power cables of the charging stations are connected to the common point (electrical cabinet in the following figure).

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Figure 7: Cluster cabling route for multiple charging stations - star network topology

Power cables Point to Point Network Topology

Power cables are routed to the first station, which is then connected to the next station with a separate power cable and a separate communication cable. Each additional station is then connected in the same way with its preceding station.

In case that Point-to-Point communication is needed for the power supply, all INCH Duo’s of the cluster with exclusion of the last one, should be equipped with double terminal clamps.

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Figure 8: Cluster cabling route - point to point network topology (daisy chain)

Power cables Hybrid Network Topology

When considering large clusters, the power supply network topology will most often be a hybrid of star and point to point network topology.

Communication

Although charging without network connection is possible, to enable common charging scenarios, network connection is required. Larger clusters are usually also connected to control centre, enabling remote control and management.

Cluster of charging stations can be connected to the network with UTP cable or over Wi-Fi to the existing ethernet network, or ethernet network can be created only for the charging stations.

One of the charging stations is designated as a cluster master and represents one point of management for the complete cluster.

All the charging stations of the cluster need to be connected to the network. The communication cables should follow star network topology. Point-to-Point wiring of communication cables is not fully supported yet. When needed all INCH Duo’s of the cluster should be equipped with router.

Table 6: Power cables installation method

Open	A1 - Insulated single core conductors in conduit in a thermally insulated wall A2 - Multicore cable in conduit in a thermally insulated wall This method also applies to single core or multicore cables installed directly in a thermally insulated wall (use methods A1 and A2 respectively), conductors installed in mouldings, architraves, and window frames.
Open	B1 - Insulated single core conductors in conduit on a wall B2 - Multicore cable in conduit on a wall This method applies when a conduit is installed inside a wall, against a wall or spaced less than 0.3 x D (overall diameter of the cable) from the wall. Method B also applies for cables installed in trunking / cable duct against a wall or suspended from a wall and cables installed in building cavities.
Open	C - Single core or multi-core cable on a wooden wall This method also applies to cables fixed directly to walls or ceilings, suspended from ceilings, installed on unperforated cable trays (run horizontally or vertically), and installed directly in a masonry wall (with thermal resistivity less than 2 K·m/W).
Open	D1 - Multicore or single core cables installed in conduit buried in the ground D2 - Multicore or single core cables buried directly in the ground
Open	E - Multicore cable in free-air This method applies to cables installed on cable ladder, perforated cable tray or cleats provided that the cable is spaced more than 0.3 x D (overall diameter of the cable) from the wall. Note that cables installed on unperforated cable trays are classified under Method C.
Open	F - Single core cables touching in free-air This method applies to cables installed on cable ladder, perforated cable tray or cleats provided that the cable is spaced more than 0.3 x D (overall diameter of the cable) from the wall. Note that cables installed on unperforated cable trays are classified under Method C.
Open	G - Single-core cables laid flat and spaced in free-air This method applies to cables installed on cable ladder, perforated cable tray or cleats provided that the cable is spaced more than 0.3 x D (overall diameter of the cable) from the wall and with at least 1 x D spacings between cables. Note that cables installed on unperforated cable trays are classified under Method C. This method also applies to cables installed in air supported by insulators.

Cluster Cables Cross-Section

When INCH DUO is designated as cluster master, it is possible to connect 18 INCH DUO charging stations to this cluster, meaning that charging is supported to 36 electric vehicles simultaneously. If industrial computer is designated as cluster master, it is possible to connect 150 INCH DUO charging stations in the same cluster, meaning that charging is supported to 300 electric vehicles simultaneously.

Considering maximal charging current of Mode 3 AC conductive charging point of 32 A (three-phase), the maximal charging power is 22,08 kW, meaning 44,16 kW for one INCH Duo. In large clusters this number rise significantly and can be in a range of large industrial consumers.

The currents presented in the following table require additional considerations from the electrical works planning view, which should be determined in the electrical project. It is possible, that high charging current would require implementation of bus-bar systems and/or possible installation of power transformers and/or additional requirements from the view of electrical safety and documentation preparation.

Table 7: Considering maximal current in case of clusters

Main factor influencing the design of a cluster is the available charging power at the location of cluster installation. This limitation can also be expressed as maximal current.

When considering charging with full power the available capacity can quickly run out even with small numbers of simultaneously charged vehicles. INCH DUO has implemented power management functionalities with option of software limitation of maximal current of charging for individual charging station or for complete cluster.

Almost all vehicles require minimally 6 A of charging current. Considering that there are some vehicles that require higher minimal charging current, some reserve to the numbers in the following table should be added to ensure all connected vehicles can charge simultaneously.

Table 8: Considering minimal current in case of clusters (three-phase wiring)

In the previous table the numbers of minimal charging current are presented. Such system allows charging of individual electric vehicles with maximal power of 22,08 kW.

Power management can be used to set limitation of the maximal current of the complete cluster (determined by the location, e.g., main fuses). If this limitation is active, individual charging stations limit the charging power of the connected vehicles.

Considering that there are some vehicles that require higher minimal charging current, some reserve to the numbers in the following table should be added to ensure all connected vehicles can charge simultaneously.

All presented values are only indicative and are not a substitution for exact calculation of required cross-sections. Specified voltage drops are considering only voltage drop in a cable of defined cross-section and for specified current.

When calculating complete voltage drop of installation, the lowering of voltage across all the elements of the current path should be taken into consideration.

Continuous operating current

Determining the right cross-section of conductors, the method of installation need to be considered. Additional consideration is the material of the conductor and material of its isolation. The real current must also be determined using the selected planning temperature.

Informational values of minimal cables cross-section were selected using the following:

• Three-phase system with copper conductors with XLPE insulation

• Ambient temperature 35 °C

• Ground temperature 25 °C

• Thermal resistivity of the soil 2,5 K·m/W

Table 9: Minimal cables cross-sections under specified conditions (1/2)

Table 10: Minimal cables cross-sections under specified conditions (2/2)

Voltage drop

The requirement for the maximum voltage drop of the installation can be different across different countries. Usually, it is required that the voltage drop of the installation is below 4 % (or in some cases below 5 %).