When an electrical supply is laid on to domestic or similar premises, the host Distribution License Holder (DLH) will require the provision of a suitable meter cabinet at the service position to house the intake and metering equipment. Although this meter cabinet is provided with the property, the distributor will specify that only equipment belonging to the distributor and meter operator (MOP) should be installed therein.
The space within such cabinets is limited and therefore allocated for specific usages by the distributor and energy supplier, and therefore should not be used to house other equipment relating to the consumer's installation. Bimetal Cable Lugs
IPCs are not designed for use on insulated and sheathed meter tails. If encountered by Distribution Network Operators (DNOs) or MOPs when attending to carry out work, some will, with the customer’s permission remove the IPC and remake the connection with a more suitable method. In the event that the customer will not allow this replacement work to be carried out, the DNO or MOP may refuse to carry out their planned updating or improvement works.
Concerns relating to the use of insulation piercing connectors in meter cabinets
IPCs are a type of connector in which electrical contact with the conductor is made by metallic protrusions which pierce the insulation of an aerial bundled cable core. The relevant product standard for such connectors is BS EN 50483-4:2009 Test requirements for low voltage aerial bundled cable accessories - Part 4: Connectors.
The scope of BS EN 50483-4 states that the standard applies to connectors used for the electrical connection of aerial bundled cables (ABC) only.
A number of concerns have been raised in respect of the use of IPCs to provide a connection to types of cable other than ABC, and in particular meter tails.
Fig.1. Constructional differences between typical ABC and meter tail cables
When an IPC of the type seen being used in meter cabinets is tightened down onto an XLPE insulated conductor of an ABC, the core behaves like a solid conductor. However, when installed on a typical double insulated copper meter tail the individual circular shaped strands of the conductor spread under compression, reducing the effective contact area of the connection while increasing the termination resistance.
Where installed in the meter cabinet neither the meter tails nor the IPCs are fixed, which may allow movement in the connection. This could result in heat build-up, which may lead to joint failure.
Further, if the IPC is not correctly aligned with the conductor when installed, the IPC will not clamp down as intended which may also contribute to a poor connection.
These factors raise concerns as to whether the requirements of BS 7671 for effectiveness of joints and connections have been met (134.1.4, 134.1.5, 522.8.5 and Section 526).
The combined thickness of the insulation and sheath of a meter tail is noticeably thicker than the insulation on an ABC conductor. As a result, it is unlikely that the ‘teeth’ of the connector will engage fully. The IPCs are being employed outside of the scope of their product standard, but electrical contractors are not in a position to determine which IPCs might be suitable for use to provide a connection that is no less safe than using other recognised means of connecting into meter tails, as required by BS 7671 (See regulations 120.3, 133.1.3 and 511.2).
The possibility of poor connections is a particular concern, given the high currents that may be drawn by an EV during certain periods of its charging cycle.
BS 7671 states that a protective measure shall consist of:
An appropriate combination of a provision for basic protection and an independent provision for fault protection, or
An enhanced protective provision which provides both basic and fault protection (410.3.2).
Typically, the protective measure employed is automatic disconnection of supply (ADS), in which basic protection is provided by basic insulation, barriers or enclosures and fault protection is provided by protective earthing, protective equipotential bonding and automatic disconnection in the event of a fault (411.1). However, this protective measure is not typically applied to the meter tails situated before the first fault protective device of the electrical installation (434.3).
More typically, the protective measure of double or reinforced insulation is used for the meter tails, and other equipment between the service fuse and the first protective device of the installation. Double or reinforced insulation is a protective measure in which:
Basic protection is provided by basic insulation and fault protection is provided by supplementary insulation, or
Basic and fault protection are both provided by reinforced insulation between live parts and accessible parts.
Although the meter tails are insulated and sheathed, so meeting the requirements of regulation 412.2 for basic and fault protection for double insulation (412.2.4.1), the IPC is not. When IPCs are used in an aerial application the danger of inadvertent contact is minimal given the mounting height above ground effectively placing them out of reach. However, where IPCs are installed within a meter cabinet they are in a readily accessible enclosure to which it is not possible to prevent unauthorised access. As a result, the conditions for protection by double insulation are not met.
Currently, there are no IPCs designed specifically for use on double insulated meter tails. As it is not possible for a contractor to confirm that the use of IPCs in this manner is no less safe than using a recognised means of connecting to the meter tails, such use is a non-compliance with the requirements of BS 7671.
Attitudes of Distribution Network Operators (DNOs) or Meter Operators (MOPs) on encountering IPCs used to connect to meter tails may vary. Some will advise the customer of their concerns regarding the use of this means of connection and, with the customer’s permission may remove the IPC and remake the connection using a means recognised as suitable for such use. In the event that the customer refuses to allow this replacement work to be carried out, the DNO or MOP may issue an Electricity Deficiency Notice and decline to carry out their planned updating or improvement works.
In either case, the customer may raise complaints in respect of the original use of IPCs on the meter tails, causing reputational damage for the contractor who installed them initially.
As a result, NICEIC strongly recommends that electrical contractors do not use IPCs to provide a branch connection in meter tails.
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