Low-voltage connections

The connection agreement between the customer and Caruna defines the connection of equipment to the distribution network. When building and connecting a new electricity connection to the network, the general connection terms for electricity usage points (LE 2019), pricing methods for connection fees as determined by the Energy Authority, and Caruna’s connection fees and related terms apply.

The connection agreement specifies, among other things, the size of the connection, the point of connection, and the delivery time. The connection terms may also be supplemented with case-specific special conditions. The connection agreement for a new connection or an enlargement specifies the delivery time, which is a reservation for the network company’s practical measures to enable the connection to be linked to the network.

Based on the general information form submitted by the electrical contractor, Caruna connects the usage point to the electricity network. Electricity connection also requires that the customer has agreed on electricity purchase and network service.

For the electricity distribution network agreement, the network service terms VPE 2024 apply. According to these terms, electrical installations must be carried out, inspected, and connected to the network in compliance with electrical safety legislation, related regulations, and industry standards.

The use of certain electrical devices must be agreed upon in advance with the network company according to section 4.6 of the network service terms VPE 2024. These include motors or compressors with a starting current significantly higher than the main fuse size, as well as production plants and generators. In sparsely populated areas, the trouble-free operation of heat pumps must be ensured in advance. The feeding of electricity from backup generators into the distribution network must be effectively prevented by technical means.

The connection delivery boundary, or point of connection, is specified in the connection agreement and, for low-voltage connections, is most often the cable end located at the plot or building site boundary, a distribution cabinet, an overhead line pole (network-side connectors are included in Caruna’s delivery), a combination cabinet, or a substation.

The cable between the point of connection and the customer’s switchboard is not included in the connection fee. The customer agrees on its delivery and installation with an electrical contractor of their choice.

For new connections where the point of connection is at the plot boundary, the joint at the plot boundary is handled by the network company’s contractor, but when the customer’s contractor makes changes to the customer’s connection cable, the jointing is the responsibility of the customer’s electrical contractor.

Connecting the connection cable to the customer’s main switchboard is always the responsibility of the customer’s electrical contractor.

An SFS 6000-compliant main protective device must be installed for the electricity connection. The main protective device must be located in the main switchboard. Fuses are generally used as the main protective device. Circuit breakers are not accepted as the main protective device for the connection.

In the case of two or more parallel connection cables, both cables must be protected with their own fuses at both ends. The principle is shown in Figure 1.

The dimensioning of the distribution network affects the protection of the internal electrical network of the connection. The electrical planner of the connection must ensure that the protection of the internal network meets the protection time requirements and other requirements specified in the SFS 6000 standard series.

For new 3x25 A–3x50 A connections, the supplying distribution network is dimensioned so that the single-phase short-circuit current at the main fuses of the connection is generally at least 250 A. This short-circuit current level can be used for dimensioning the internal network protections of the connection, except in exceptional cases.

In individual exceptional cases where a 3x25 A connection is connected to an existing distribution network, it may be necessary to deviate from the 250 A design short-circuit current for special reasons. In these exceptional cases, the short-circuit current must still be at least 180 A. The designer of the internal electrical network of the connection must ensure compliance with the protection time requirements of SFS 6000.

For connections over 3x50 A, the distribution network is dimensioned so that the single-phase short-circuit current at the main fuse of the connection is at least as shown in Table 1. The short-circuit current in Table 1 must be used for dimensioning the internal network protections of the connection, even if the actual short-circuit current at the time of design is higher, because the supplying network and short-circuit current may change later. In the case of parallel main fuses, the design short-circuit current can be calculated using multiples of the short-circuit currents in Table 1, as shown in the two lowest rows of the table.

The connection cable must be sized and constructed according to the requirements of the network company. As a rule, 4-core cables (AXMK) are used as connection cables. The cable is sized according to the connection size. For new connections, the conductor cross-section must be at least 25 mm² for aluminum or 16 mm² for copper. The recommended total length of the connection cable is a maximum of 100 m.

In certain exceptional cases (e.g., when the connection cable is unusually long (>100 m) and/or the connection is located far from the supplying substation), even small connections of 3x25 A–3x35 A must use AXMK 4x50 mm² cable to ensure sufficient short-circuit current at the main fuse of the connection.

Recommended cable types for connection cables are AXMK-type underground cables with cross-sections of 25, 50, 95, 150, 240, and 300 mm².

Note: New connections of at least 3x600 A are generally implemented so that the customer connects directly to Caruna’s distribution substation.

When building a new connection or enlarging an existing one, it must always be checked and ensured that the fault, short-circuit, and overload protection of the connection cable complies with requirements. The customer must ensure that the sizing and installation of the connection cable section under their responsibility is carried out according to the requirements set by overload and short-circuit protection.

Table 2 shows the maximum permissible overload protection (gG fuse) for different cable cross-sections based on SFS 6000 standard load capacities for installation methods D1 (multi-core cables in conduit underground) and D2 (multi-core cables directly underground). Cable load capacity and overload protection have been defined using the variable values and standard sections listed below.

SFS 6000 load capacities for PEX-insulated aluminum conductor cables, cables in conduit (D1):

• SFS 6000-8-801 Table 801B.1
• SFS 6000-5-52 Table B.52.19
• Conductor temperature: +65°C, soil temperature: +15°C, soil thermal resistivity: 1.0 K·m/W
• Installation method D1 according to SFS 6000-5-52 Table B.52.1 (multi-core cables in conduit underground)
• Distance between conduits: 0 cm (conduits touching each other)
• SFS 6000-5-52 Table Y.52.1 Minimum load capacity values for different fuse ratings

SFS 6000 load capacities for PEX-insulated aluminum conductor cables, cables directly underground (D2):

• SFS 6000-8-801 Table 801B.1
• SFS 6000-5-52 Table B.52.18
• Conductor temperature: +65°C, soil temperature: +15°C, soil thermal resistivity: 1.0 K·m/W
• Installation method D2 according to Table B.52.1 (multi-core cables directly underground)
• Distance between cables: 0 cm (cables touching each other)
• SFS 6000-5-52 Table Y.52.1 Minimum load capacity values for different fuse ratings

When defining overload protection, all factors affecting load capacity must be considered, including different installation methods along the cable route. It must be noted that load capacity may be determined by an installation method other than D1 or D2 mentioned above.

If the connection right is increased or changes are made to the connection cable, this always requires a case-specific review to ensure compliance with requirements.

The customer must construct the connection cable at their own expense from the point of connection specified by the network company onward. The connection cable must be installed along its entire length in compliance with the requirements of the SFS 6000 standard series. Installation must consider different installation methods, such as underground installation and internal routing within the property. Each installation method must comply with its respective requirements, including mechanical and fire protection. The installation method also affects the load capacity of the connection cable. It must be ensured during installation that the cable’s load capacity is not exceeded.

The route and length of the connection cable inside the property building should be kept as short as possible. For the section of the connection cable installed inside the building, SFS 6000-8-801 section 801.42 Protection against thermal effects must be observed. For fire behavior, an unclassified cable or a cable of class Fca must be placed in its own fire compartment inside the building. In other fire compartments, the length of an unclassified or Fca-class cable must be as short as possible, and the total length inside the building must not exceed 5 m. Caruna’s cables are not classified for fire behavior.

For underground and underwater installations, the requirements presented in SFS 6000-8-814 (Supplementary requirements. Installing cables in soil or water) must be followed. The installation depth of the cable in the ground must be at least 0.7 m. If this depth cannot be maintained, additional protection for the cable must comply with the requirements in table SFS-6000-8-814.1. If a protective duct is used as additional protection, compatibility must be confirmed with the network company’s representative.

If the point of connection is at overhead line connectors on a pole, fastening the connection cable to the pole is handled by the network company or its authorized contractors for work requiring climbing the pole. In such cases, the customer’s contractor is responsible only for fastening the cable to the pole from ground level (including protective cable guard) and reserving approximately 10 meters of cable for network connection. The contractor fastens the cable to the pole up to 1.5 meters in height, or 2 meters along traffic routes. When installing the protective guard, ensure it extends at least 0.2 m below ground level. The same procedure applies in other situations requiring climbing the network company’s pole.

The recommended metering switchboard and its location is a yard cabinet placed at the plot boundary. This makes it suitable for both temporary and permanent use during construction. Other placement options include a well-protected exterior wall or a technical room with direct outdoor access (see locking details in the contractor guidelines under Locks).

The metering cabinet must not be mounted on a network company pole. It must also not be installed in a locked space such as a hallway, garage, storage room, or carport. During renovations where the metering cabinet is replaced, it should be placed as in new installations.

In multi-meter sites, metering must be arranged so that all meters are located in the same cabinet. If this is not possible, all meters belonging to one group must be placed in the same room, for example, by stairwell in apartment buildings.

The connectivity and point of connection for a temporary electricity connection must be confirmed with our contractor service before connection.

The connection cable for a temporary electricity connection must meet the requirements of SFS 6000 for temporary cables. The customer’s electrical contractor is responsible for building the temporary network from the point of connection to the customer’s switchboard. The temporary metering cabinet can be placed at a maximum distance of 200 meters from the point of connection. A temporary connection must have grounding built according to the requirements of SFS 6000-5-54.