How to install an accounting shield on a support without breaking the rules
First of all, it should be borne in mind that the electric grid company connects directly to the electric networks only if all the requirements for installing the metering board and all the necessary documents are met.
Therefore, the first step is to draft and approve it in the power grid organization. As a rule, the organization has standard designs for connecting to power grids and a list of requirements regarding the choice of protective devices rating, type of meter, cross-section of the lead-in wire (cable), type and design of the metering and distribution panel case, as well as requirements for mounting the panel itself on a support or in the other place. Perhaps, at the request of the supplying organization, it will be necessary to connect the meter to an automated system for the commercial accounting of electricity (ASKUE).
Often there are situations when, after acquiring an input cable, installing a switchboard, meter, and the necessary protective devices without prior approval, the power supply organization refuses to connect to the mains and you have to fix installation errors or re-purchase a new electric meter, protective devices, and other elements.
Therefore, if you already have a finished project, then before purchasing the necessary structural elements and proceeding with the installation of the electrical panel, you should coordinate the project with the supplying organization.
The metering panel can have various design: in the form of a small box designed for the installation of metering device and protective device or in the form of a full-fledged cabinet in which several protective devices and other auxiliary elements for electricity distribution can be installed (metering and distribution and group metering distribution plates).
Shin guards are also classified by degree of protection enclosures from the negative effects of moisture and foreign objects, including dust. In this case, the shield is mounted on a support (pillar), that is, outdoors, so the case of such a shield must have a degree of protection of at least IP54. Also, choosing the housing of the metering and distribution panel, it is necessary to take into account the possibility of its operation in the temperature range of local environmental conditions.
The case of the metering panel for outdoor installation must have a locking device, and the case itself must have a transparent window for the possibility of unhindered readings by energy sales representatives.
Rules for installing an accounting shield
Here are the norms for installing an electric switchboard according to PUE 7. According to chapter 1.5, p. 1.5.29, the distance from the surface of the earth (floor) to the terminals of the meter should be in the range of 0.8-1.7 m. The shield itself can be installed both on the support (pole) and on pipe rack - in this case, everything also depends on the requirements of the supplying organization.
The electric meter must be protected by fuses or circuit breakers. At the same time, the distance from the electric meter to the protective devices should not exceed 10 m.
Often, consumers do not comply with the requirements for choosing the rating of protective devices, which can lead to damage to the meter. And in case of exceeding the permissible power limit for several consumers, it can lead to undesirable overload on the supply line as a whole, which entails the occurrence of emergency situations in the electrical network.
Therefore, in most cases, the supplying organization installs metering panels with the ability to install a circuit breaker. Circuit breakerfirstly, it protects the electric meter itself from overload, and secondly, it limits the load in accordance with the contract for the power supply of the house, which, as a rule, indicates allocated power. The circuit breaker is installed and connected when connected to electrical networks, and the shield itself is sealed to prevent unauthorized replacement of the machine, as well as unauthorized interference with the operation of the measuring device.
The metering panel is installed only on a stable and reliable support with the help of a special bracket and other elements for installation, which are included in the kit for the panel or which must be purchased separately.
Also, in order to protect against damage or interference, the supplying organization can install the metering panel on a support (pole) at a height of more than 1.7 m.
Grounding electrical panel
Very often the question arises of how to ground the electrical panel. In this case, first of all, it is also necessary to be guided by the requirements of the supplying organization.
In the absence of requirements, it is necessary to ground the shield, taking into account the grounding system of the electrical network. Most consumer networks have a grounding system TN-C, which provides for the combination of the neutral and protective conductors in the PEN conductor along the entire length of the line. The point of separation of this conductor into protective grounding and neutral conductors is carried out in the shield until the meter itself, and after separation, the grounding system is called TN-C-S. According to the rules, the PEN conductor has several repeated groundings on the supports along the entire length of the line and at the end, in the metering board on the support (pole), it is also grounded.
The PEN conductor is connected to the metal housing of the electrical panel, and the shield, in turn, is connected to a pre-mounted ground electrode (ground loop) using a ground conductor. The cross-section of the ground wire must be no less than the cross-section of the input supply cable.
But it is important to consider that grounding the home wiring and the PEN conductor in particular can be not only useless, but also dangerous. If the supply line is in an unsatisfactory technical condition, and the repeated grounding of the PEN conductor on the supports (poles) of the line does not meet the requirements, then in case of a break in the PEN conductor, a dangerous potential may appear on the body of the grounded shield. In this case, an equalizing current will flow through the grounding conductor and along the ground loop, which can lead to damage to the input cable.
Therefore, if the grounding of the supply line does not meet the requirements for the declared grounding system of the electric network, it is better to use the combined PEN conductor of the input cable exclusively as a zero input wire. You can do it yourself TT grounding system, that is, mount an individual grounding wiring circuit and ground the metal housing of the electrical panel on it.
Finally, we recommend that you watch the video, which clearly shows the installed grounded shield on the post:
Here are actually all the recommendations that we wanted to provide you. We hope that now you know how the metering board is installed on the support according to the EMP and what requirements are presented for this type of work. We hope the information provided was useful and interesting for you!