Low voltage electricity metering. Scheme, description

ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Low voltage electricity metering. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric meters

define

Commercial metering of electricity is called the accounting of generated, as well as released to wholesale buyers and / or consumers of electricity for monetary settlement for it.

Commercial accounting counter - a technical device permitted for use in accordance with the procedure established by law, intended for commercial accounting of electrical energy and power control.

Commercial meters must perform the functions of accumulating, storing, encoding information and, at a specified time interval, automatically transmit commercial metering data and information about metered electricity recorded at each given moment of power measurement to the collection and storage devices.

Installation points for electricity meters

Commercial meters (including those included in commercial metering systems) must be installed at the interface between the network of the power supply organization and the consumer and at the points of purchase and sale of electricity by electricity market entities.

When used for commercial accounting of commercial meters that simultaneously account for active and reactive energy, the installation of separate reactive energy meters is not required.

When using microprocessor meters for commercial accounting of active energy, which simultaneously account for reactive energy, the installation of separate reactive energy meters is not required.

In other cases, reactive electricity meters should be installed:

1) on the same circuit elements on which active electricity meters are installed for consumers paying for electricity, taking into account the reactive power allowed for use;

2) at the connections of reactive power sources of consumers, if they are used to pay for electricity supplied to the grid of the power system, or the specified mode of operation is monitored.

Requirements for commercial meters

Electricity meterused as a commercial one must be certified and included in the register of the State System for Ensuring the Uniformity of Measurements of the Republic of Kazakhstan.

Each installed commercial meter must have seals with the verifier's mark on the casing attachment device, and on the clamping cover or other device that excludes access to a number of electric meter clamps, the seal of the power supply and (or) power transmission organization.

Newly installed meters must have verification seals with a prescription of no more than 12 months.

Accounting for active and reactive electricity of three-phase current should be carried out using three-phase meters.

Accuracy class of commercial metering meters for low voltage connections, active 2,0 and reactive 4,0 electricity

Accounting with the use of measuring transformers

The accuracy class of current transformers for low voltage connections of meters for commercial electricity metering must be at least 0,5.

It is allowed to use current transformers with an overestimated transformation ratio (according to the conditions of electrodynamic and thermal resistance or busbar protection), if, at the maximum load of the connection, the current in the secondary winding of the current transformer will be at least 40% of the meter's rated current, and at the minimum working load - at least 5 % for induction system meters and at least 1% for multifunctional microprocessor electricity meters.

The connection of the current windings of the meters to the secondary windings of the current transformers should be carried out separately from the protection circuits and together with electrical measuring instruments.

It is allowed to jointly connect current circuits if their separate connection requires the installation of additional current transformers, and joint connection does not lead to a decrease in the accuracy and reliability class of current transformer circuits used for accounting, and provides the necessary characteristics of relay protection devices.

The use of intermediate current transformers to turn on commercial meters is prohibited.

Installation of meters and electrical wiring to them

Meters should be placed in dry rooms that are easily accessible for maintenance, in a place that is sufficiently free and not cramped for work with a temperature not lower than 0 ° C in winter.

It is allowed to place meters in unheated rooms and corridors of switchgears of power plants and substations, as well as in outdoor cabinets. At the same time, their stationary winter insulation should be provided for by means of insulating cabinets, hoods with heating of the air inside them with an electric lamp or a heating element to ensure a positive temperature inside the hood, but not higher than + 20 ° С.

Meters should be installed in cabinets, chambers of complete switchgears (KRU, KRUN), on panels, shields, in niches, on walls with a rigid structure.

It is allowed to mount meters on plastic or metal shields.

Height from floor to meter terminal box should be within 0,8 - 1,7m. Allowed height less than 0,8 m, but not less than 0,4 m.

In places where there is a risk of mechanical damage to the meters or their contamination, or in places accessible to unauthorized persons (passages, stairwells, etc.), a lockable cabinet with a window at the level of the dial should be provided for the meters. Similar cabinets should also be installed for joint placement of meters and current transformers when metering on the low voltage side (at the input of consumers).

The design and dimensions of cabinets, niches, shields, etc., should provide convenient access to the terminals of meters and current transformers. In addition, it should be possible to conveniently replace the meter and install it with a slope of no more than 1 °. The design of its fastening should provide the possibility of installing and removing the meter from the front side.

Wiring for meters low voltage should be 2,5 mm2 for copper and 4 mm2 for aluminum

In electrical wiring to settlement meters rations are not allowed.

When installing electrical wiring for connection of meters of direct connection near the meters it is necessary to leave the ends of the wires length not less than 120 mm. The insulation or sheath of the neutral wire for a length of 100 mm in front of the meter must have distinctive coloration.

For safe installation and replacement of meters in networks with voltage up to 380 V it should be possible to turn off the meter installed before it on distance no more than 10 m switchgear or fuses. Voltage relief must be provided for all phases connected to the meter.

Current transformers used to connect meters at voltages up to 380 V must be installed after switching devices in the direction of power flow.

If there are several connections at the facility with separate electricity metering, there should be inscriptions on the names of the connections on the meter panels.

Publication: electro.narod.ru

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Comments on the article:

Viktor, viktor.smirnov.1943@mail.ru
The question is not idle. I would like to know exactly how the calculation of electricity for general house needs should be made according to the readings of the meter only, or should these readings be multiplied by the transformation ratio? If so, then why was it necessary to change induction electricity meters to electronic anyway, and both of them (according to our power engineers) show incorrect readings that need to be multiplied by the transformation ratio? For my part, I consider such actions of our electricity suppliers to be fraudulent.

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