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Frequently-asked questions

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Question no.1 (ask on 18/11/2014) : What are the advantages of multi-rating current transformers?

answered on 18/11/2014 :

Bi- or tri-rating models offer two advantages: they provide an upgradable solution capable of evolving with the requirements of an installation and help to simplify the management of the transformer models.

Question no.2 (ask on 18/11/2014) : What is the advantage of using 3.75 VA and 7.5 VA current measurement transformers rather than higher ratings?

answered on 18/11/2014 :

3.75 VA and 7.5 VA "low rated burden" transformers are ideal for low-consumption electronic meters and can be used to set up installations with reduced wiring, which are particularly suitable for today's metering requirements.

Question no.3 (ask on 18/11/2014) : What are the advantages of using a Class 0.2s current measurement transformer with a Class 0.5s or 0.2s tariff meter?

answered on 18/11/2014 :

The accuracy of the measurement depends on the accuracy of all the links in the measurement chain, from the transformer to the meter. Thus, the use of equipment with the lowest possible measurement error helps to reduce the global error of the measurement chain.

Global error = Square root of (CT error² + Meter error²)

The choice of Class 0.2s for a transformer helps to reduce measurement errors and improves billing accuracy: the dynamic range for measurement is significantly increased by an accuracy of 0.2% guaranteed from 20% to 120% of Irated.

Question no.1 (ask on 17/11/2014) : How should I install my measurement transformer?

answered on 17/11/2014 :

                                                                                   Towards installation

CAUTION: The power must be switched off when connecting the transformer or it must have its secondary short-circuited!
Prior short-circuiting of terminals S1 and S2 is essential when the secondary circuit has to be disconnected from the measuring instrument wired on this CT if there is a load on the feeder measured. If you have to work on a current transformer (CT) already installed and carrying a current, please short-circuit the CT secondary with a cable (1.5mm²).
The cable or busbar primary in the current transformer must respect the direction of the energy flow.
The energy should flow from the source (P1 side of the CT) towards the load (P2 side of the CT).
On TCR current transformers, 2 double S1 and S2 terminals allow you to short-circuit the secondary before opening the secondary measurement circuit.
If a split-core transformer is mounted on a feeder with a load on it, you should also short-circuit before installing the CT, unless you use TC CLIP current transformers which have a built-in short-circuiting switch.

Question no.1 (ask on 17/11/2014) : How can I check that my power monitor has been started up correctly?

answered on 17/11/2014 :
The on-screen current display helps you to ensure that all the CTs have been correctly connected in the right direction and that the right transformation ratio has been set. Ideally, you should compare these values with an estimate of the current which the load should consume.
The power factors can also be used to check whether the right current measurement was associated with the right voltage measurement when the instrument was connected, as long as you know the load and are in receiver mode.
From the Enerium 150 onwards, the Enerium range of power monitors enables you to display a Fresnel diagram for quick detection of any connection errors.

Question no.2 (ask on 16/11/2014) : What is partial metering?

answered on 16/11/2014 :

Partial metering epresses the quantity of energy measured since a zero reset of the "partial" register, like the daily mileometer on a car. For example, this function can be used to find out a camper's consumption during a stay at a camping site. Absolute metering is the consumptioon measured since the meter was put into service. It is not possible to reset this value to zero.

Question no.3 (ask on 16/11/2014) : What is a power monitor?

answered on 16/11/2014 :
Historically speaking, power monitors are characterized by their appearance: panel mounting and three-line data display. 
The ENERIUM range of power monitors now offers much higher-level functions, As electrical signals are much richer than the other energy utilities, they require high-performance equipment in order to save energy (active and reactive power, power overruns, etc.) and supervise installations (voltage, harmonics, voltage dips and and peaks, EN50160 standard, etc.).
The power monitor is not only the key element for energy measurement acquisition, but also centralizes process or on-off signals in the product's integration environment, which it can also act upon thanks to its possible multiple on-off or analogue outputs.
Power monitors must comply with the IEC 61557-12 reference standard.

Question no.4 (ask on 16/11/2014) : What does a negative power factor (-0.98) mean on my power monitor?

answered on 16/11/2014 :

This sort of behaviour indicates incorrect wiring unless you are producing energy. You should first check the direction in which the current transformers (CTs) are mounted. For mounting on a three-phase network, it is also important to check that the current measurement and voltage measurement made on a given channel of the instrument genuinely correspond to the same phase.

Question no.1 (ask on 17/11/2014) : How can I program my CT ratios on my ULYS meter?

answered on 17/11/2014 :
As the ULYS TT meter can be connected to any temperature sensor of any rating, the CT ratios must be programmed during startup to ensure that the current reading is right, which means the power calculation is also correct.
The CT ratio must be modified before adding the terminal covers and the seal because, to access the CT ratio modification menu, you have to press the SET button (on the upper cover) for 3 seconds.
When setting the parameter, the first information to be entered corresponds to the ratio of your CT's primary current over the secondary current, the second information corresponds to the type of connection and the third corresponds to the secondary current of your CT (1 A or 5 A).

Question no.2 (ask on 17/11/2014) : How can I connect my current and voltage inputs to my ULYS meter?

answered on 17/11/2014 :
The ULYS meter must be connected to each voltage and current of the load which you wish to control. The electrical connection diagrams are available in the operating manual and may vary according to the network, the required assembly and distribution or otherwise of the neutral.
You are strongly advised to install 0.5 A gG fuses on the V measurement inputs and a short-circuiting system on the I measurement inputs.

Question no.3 (ask on 16/11/2014) : Which metering or measurement solution is best for an existing installation?

answered on 16/11/2014 :

For integration on an existing installation, you should prefer systems capable of limiting installation downtime. This downtime can be limited by using non-intrusive current measurement technologies. It is therefore preferable to use ULYS meters of ENERIUM power monitors with 1/5A input alongside current transformers. The TCRO split-core sensor solutions up to 1,000 A and TC CLIP solutions up to 600 A are ideal for this type of installation.

Question no.4 (ask on 16/11/2014) : How should I connect the pulse outputs of ENERDIS meters to my pulse concentrators and how should I configure them?

answered on 16/11/2014 :
Connection: a pulse output should be connected by adding a low-level power supply to the loop of the output and the pulse concentrator. The pulse outputs of the Enerdis meters require polarization to operate, so be careful with the sign of the low-level voltage applied.
Configuration: make sure that the product's pulse weight matches the pulse weight on the pulse-concentrator side. See the meter's operating manual to find out the pulse weight.
Caution: on the Ulys TT meter, the pulse weight depends on the transformation ratios of the transformers - please see the operating manual.
The specifications of the pulse outputs are defined in the 62053-31 standard.

Question no.5 (ask on 16/11/2014) : How should I choose my power meter?

answered on 16/11/2014 :

The first criterion for choosing your meter is the type of electrical network on which it will be installed. For meters on single-phase networks, the MEMO, MD65 and MD80 solutions are all suitable, depending on the current flowing through the product (up to 80 A). For three-phase networks, ULYS TD80 meters can be used for metering and measurement up to 80 A, but for higher currents, it is preferable to use ULYS TT meters operating via remote current transformers. Outputs are available for the products listed above allowing them to communicate through pulses or industrial buses  (mbus, modbus, etc.)

Question no.6 (ask on 16/11/2014) : What is the tariff-change input on ULYS meters?

answered on 16/11/2014 :
The tariff-change input allows interfacing with an external signal corresponding to a tariff change or other modification. Depending on the voltage level imposed on the tariff-change input, a different metering index will be incremented. The index "Tariff 1" is incremented if there is no voltage present, whereas the index "Tariff 2" is incremented when a voltage is present (see operating manual). In this way, it is possible to monitor your consumption separately.
Note: the total indices are not affected by the tariff-input status change.

Question no.1 (ask on 16/11/2014) : What does "2-slope expanded output" mean for certain transducers?

answered on 16/11/2014 :
This means that the output signal from the transducer does not always have the form y = ax across the whole measurement range because a break point has been programmed. The first slope is slight and, beyond the break point, the second is steeper. This trick gives better output resolution near the end of scale because a small variation in the input signal causes a significant variation in the output signal.
Example with a transducer with 0...100 V input and 0...2...20mA output: from 0 to 80%Ue, i.e. 0...80Vac, the output varies from 0 to 2 mA; a one-Volt input variation leads to a 25 µA output variation. From 80% to 120%Ue, i.e. 80...120 Vac, the output varies from 2 to 20 mA; the output variation rises to 400 µA for 1 V.

Question no.1 (ask on 16/11/2014) : How can I install a shunt?

answered on 16/11/2014 :

A shunt must be mounted on the "chassis earth" side of the installation, particularly if the network voltage is higher than 500 V. The best ventilation by natural convection is achieved by mounting the shunt horizontally, with the plane of the blades positioned vertically. As cooling is largely achieved by conduction towards the current inlets, it is useful to make use of generously-dimensioned cables or busbars which are thoroughly tightened. For continuous operation, you are advised not to constantly apply more than ¾ of the rated current. It is advisable in all cases to avoid blade temperatures higher than 145 °C. If the operating conditions do not allow sufficient natural ventilation, you must provide backup ventilation or another cooling method.

Question no.1 (ask on 16/11/2014) : Secondary of a current transformer: 1 A or 5 A?

answered on 16/11/2014 :
A 1 A secondary current will cause fewer line losses than a 5 A current. It offers greater accuracy while reducing wiring costs.
However, for a given primary current, the transformation ratio is 5 times higher with a 1 A CT than with a 5 A CT. In opther words, there is much more winding, making it more expensive and heavier.

Question no.2 (ask on 16/11/2014) : What is the rated burden of a transformer?

answered on 16/11/2014 :
It is the apparent power, in voltampères (VA), which the transformer must supply to the secondary to remain within the accuracy class.
The power of a transformer for a given accuracy class must correspond to the sum of the power of the instrument which it powers and the power absorbed by the associated conductors. This power is chosen slightly higher than this sum to avoid inrush currents and ensure that the transformer remains within the accuracy class if the temperature rises.

Question no.3 (ask on 16/11/2014) : How should I choose a current transformer?

answered on 16/11/2014 :

In addition to its size, a current transformer (CT) is chosen according to the primary current of the installation, the required secondary current (usually 1 or 5 A), the type of primary conductor (cables or busbars, with their dimensions), the accuracy class for a specific application spécifique (e.g. supplying power to a measuring instrument: an accuracy class as close as possible to that of the instrument) and the rated burden. Note that CTs with wound primaries are used to measure low currents while maintaining high power and accuracy. Split-core CTs, meanwhile, are easy to set up on existing installations without cutting off the the power supply.

Question no.1 (ask on 16/11/2014) : Which equipment can be used by ELOG?

answered on 16/11/2014 :

All equipment with RS485 Modbus or Modus TCP digital output (meter, power monitor, transducer, sensor, probe, PLC, etc.)