Installation of the power meter
The electric counter - the electrical measuring instrument intended for accounting of the expense of electrical energy of the variable or direct current which is measured in kWh or And / h.
Power meters are used where legal electric power consumption is carried out and there is the opportunity to save money, monitoring its consumption for the certain period.
Power meters are issued single-phase or three-phase. Join in network via measuring current transformers (indirect inclusion) and without them (live broadcast). Counters on current from 5 to 20 are used to inclusion in network up to 380 V And. Now two types of power meters – induction and electronic are generally used. At the same time the first it is much bigger as they were established to the middle of the 90th years.
There is the question what counter is better - induction or electronic? To answer it, it is necessary to understand what tasks will be assigned to it, except simple writing off of indications. Whether the different functions put in the majority of electronic meters will be necessary.
The principle of operation of the induction power meter consists in interaction of magnetic forces of inductance coils of current and tension with magnetic forces of the aluminum disk, as a result of interaction disk speed in direct ratio reflects the electric power expense the calculating mechanism. Induction meters are outdated, do not support multitariff accounting and the possibility of remote transfer of indications.
Unlike induction meters, electronic meters are constructed on the basis of chips, do not contain the rotating parts and make transformation of the signals arriving from measuring elements to proportional sizes of power and energy. Electronic power meters differ in higher accuracy and reliability in comparison with induction power meters, have the bigger intertesting interval.
On the obverse of the counter disk speed (for the induction meter) or quantity of impulses (for electronic) is specified, to the corresponding 1 kW? h electric power. For example, 1 kW? h – 1250 turns of the disk. The quantity of the consumed electric power in this case is directly proportional to disk speed.
Accuracy class – the key technical parameter of the power meter. He points to the level of the error of measurements of the device. To the middle of the 90th years all counters installed in houses had the class of accuracy 2.5 (the most admissible level of the error was 2,5%). In 1996 the new standard of accuracy of the metering devices used in the household sector – 2.0 was entered. It became the push to universal replacement of induction meters on more exact, with the class of accuracy 2.0
Also important parameter of the power meter is the tarifnost. Until recently all power meters used in life were one-rate. Modern counters allow to keep account on zones of days and even years from time to time.
Double rate meters give the chance to pay for the electric power less - at the scheduled time they automatically switch to the night rate which is almost twice lower than day. The two-tariff system offers separate rates for day (from 7:00 till 23:00) and nights (from 23:00 till 7:00).
The most modern models can be reconstructed on any tariff policy. For example, if power engineering specialists decide to give discounts on days off, then only owners of the counters capable to support several rates will be able to use them. Rates and time of the modes are entered by the representative of the electrosupplying organization which register the power meter, seal up it and grant permission for use.
Today all new houses at the stage of construction are equipped with the automated systems of accounting of the electric power of ASKUE which give to inhabitants the opportunity to make accounting of the electric power differentially on time of day. Not only double rate meters, but also the equipment of automatic equipment which allows to program power meters enter this system and to take readings from them remotely. If the house is not equipped with the automated accounting system, then it is possible to install the double rate meter with the tasksetter.
Eventually, because of wear of materials, the class of accuracy of the power meter can change. There comes time when the power meter needs to be checked for the accuracy of indications repeatedly. The period from the moment of primary check (it is normal from date of issue) before the following check is called the intertesting interval. The intertesting interval is measured advanced in years and it is specified in the passport of the power meter. Duration of the intertesting interval is connected with the term of operation of the device and with the guarantee for it. The opportunity to make warranty and post warranty repair is important.
To check correctness of charge of payment in the modern power meter, it is not necessary to look for old receipts on payment any more, the counter with the corresponding function will show how many and in what month and on what rate it is spent the electric power. It is not necessary to calculate in the column the difference between indications in the month any more, the power meter is capable to make it.
Now there is the wide choice of power meters. Each of them has the characteristics, different functionality. Of course, not all need different functions, such, for example, as the mnogotarifnost, some want the simple, reliable and exact counter at reasonable price. Now there is the wide choice of power meters, it is possible to choose that which approaches more.
The power meter is single-phase induction one-rate
The power meter single-phase induction one-rate is generally intended for measurement and one-rate accounting of active electrical energy in single-phase two-conductor alternating current circuits.
Such power meters are chosen on the accuracy class, on climatic conditions, on combination of metering devices in ASKUE, on the telemetric exit or the certain type of the interface.
Single-phase double rate meters with the external tasksetter mean surely use of such tasksetter. The single-phase power meter has to be steady against electromagnetic influence.
Has high reliability and durability, it is made of the materials which are not sustaining combustion, service life not less than 30 years are issued both in the classical body of black color, and in the body from transparent material.
It is intended for operation in electric units of office, residential and public buildings, production rooms, cottages, dachas, trade booths, shops, garage cooperatives, etc. at supply of consumers of electricity from the single-phase power supply network.
The power meter is three-phase electronic multitariff
The power meter three-phase electronic multitariff has the built-in digital interface, the built-in tasksetter.
Provides accounting of the active and reactive electric power in one - or multitariff the modes totally on all phases or can carry out the accounting of active energy on each phase separately. On the liquid-crystal display are displayed - values of active and reactive electrical energy, measurement of instantaneous values of active, reactive and ultimate power on each phase and on the sum of phases, measurement on each phase - current, tension, frequency, cos ф, corners between phase tension.
Such power meter supports data transmission of measurements on power network, on interfaces - CAN, RS-485. All available information can be transferred. There is the opportunity to program the counter in the mode of summing of phases "on the module" for prevention of plunder of the electric power at connection phasing violation, there is the opportunity to adjust the internal clock of the power meter.
It is intended for operation in electric units of office, residential and public buildings, production rooms, cottages, dachas, shops, garage cooperatives, etc. at supply of consumers of electricity from the three-phase power supply network.
Calculation of power of loading
Sometimes there is the need to learn how many consume separate electric devices of time at present. For this purpose it is necessary to switch-off unnecessary devices, to include necessary. Further to count quantity of turns of the disk or quantity of impulses in one minute depending on the meter type and to calculate by the formula:
W = (N* 60) / (Imp * t), kW
where W — power consumption for the hour, n — quantity of impulses or turns of the disk for the certain period of time, Imp — quantity of impulses or turns of the disk, the corresponding 1 kWh, t — time in minutes.
Schemes of connection of the power meter
Scheme of connection of the single-phase (induction) power meter.
The phase wire and the current coil are designated in red color; the zero wire and the voltage coil are designated in blue color.
Scheme of connection of the three-phase power meter of direct action (connection).
The phase "A" is designated in yellow color, the phase "B" - green, the phase "C" - red, the zero wire of "N" - blue color; L1, L2, L3 - current coils; L4, L5, L6 - voltage coils; 2, 5, 8 - tension screw; 1, 3, 4, 6, 7, 9, 10, 11 - plugs for connection of the electrical wiring to the counter.
The scheme of connection of the three-phase power meter via current transformers.