Easily Capture Energy Data: 3 Methods Explained in a Practical Way!

The basis of any energy efficiency optimisation is the detailed collection of energy data. But there are different methods for this. We explain how to record energy flows using existing electricity meters, folding transducers and energy meters, how the recording works and what the decisive advantages and disadvantages are.

Recording by means of existing electricity meters

In the case of meters, it is usually possible to tap the energy consumption by means of pulses. Pulses are output via various interfaces, which have a certain value depending on the meter type and size.

These can be found on the type plate of the meter or in the operating instructions. Example: 1kWh/1000 pulses = 1000Wh / 1000 pulses = 1Wh/pulse

Counters typically offer the following interfaces:

• S0 interface, potential-free contact, weighted pulses via controllers (24V)
  Wiring: The respective pulses can be connected to the LineMetrics Box via a simple wiring (2 wires). As a result, the data logger counts the occurring pulses and assigns them the correct value.
• LED flashing pulse (special form of detecting pulses, similar to other interfaces): Some counters have visible LEDs that emit the pulses as light (not to be confused with IR interface!). By means of an LED receiver, the flashing pattern, which represents the value of the pulses, can be converted into an electrical signal. This is measured and implemented by the LineMetrics Box.
• Modbus RTU: Some counters use a specific bus protocol to transmit data. Using the LineMetrics Box, the following bus protocol can be used to collect values: MODBUS RTU (FC1, FC3, FC4). To do this, you will need the following interface: RS485.

Pros and cons of existing meters:

+ No installation work on the electrical installation necessary
+ Easy connection to the LineMetrics data logger via 2 wires

– An energy supply company (EVU) is required for sealing
– Interfaces often have to be purchased separately from the RU
– It may be necessary to inform the RU about the connection
– Only energy values can be transmitted and visualized

Acquisition by means of current transformers (folding core transformers)

Folding core converters are simply mounted (“folded”) over an existing cable – similar to the measurement with a current clamp. They are a cost-effective and simple method to infer the energy values by measuring current.

No contact with the live wires is necessary – the circuit does not necessarily have to be opened or interrupted.

The current transformers convert the measured alternating current into an analog signal (0V – 10V) that can be measured by the LineMetrics Box, which is displayed in the LineMetrics Cloud as current or power (note: measurement method only for apparent current and therefore only for apparent power).

Further calculations can be used to draw fairly accurate conclusions about the electricity and energy consumption. However, the mains voltage and the power factor must be assumed or determined in advance.

The right choice of current transformer:

The nominal current of the converters (5A, 10A, 25A, 100A, 250A, 500A) depends on the maximum current of the measured line. In most cases, it is sufficient to inquire about the amount of protection and choose the next higher value for the converter.

Eg. Fuse protection 160A → rated current converter 250A

Attention: The cable cross-section also plays a role in the use of the converters!

Ideal use case:

Simple current measurement and power recording, display of load curves and current peaks, traceability of electricity costs, temporary and mobile applications

Recommended Products: Folding Core AC Transformer VH Series (5A – 500A)

Note: Alternatively, Rogowsky coils can also be used for high currents or very large cable cross-sections or busbars.

Pros and cons of folding converters:

+ Quick installation without interruption of the mains (observe safety rules!)
+ Galvanic isolation of mains and measuring system
+ Lossless measurement of current
+ Continuous current curve and thus power curve/load curve
+ Very cost-effective

– No voltage sensing
– No recording of the power factor
– Recalculation is based on fixed assumed factors

Recording by means of energy meters

Depending on the type, energy meters are connected directly to a low-voltage system (400V, three-phase). Depending on the application, individual circuits or the entire system can be measured.

By correctly assigning the respective phases, an energy meter enables the display of many values of the circuits: apparent, active and reactive power, currents and voltages occurring, mains frequency, apparent, active and reactive energy.

The energy meters can be easily and quickly connected to a system by electrical engineers and configured to the correct grid systems. Via various interfaces such as S0 or RS485 (MODBUS RTU), the measured values can be recorded and transmitted from the LineMetrics Box .

No calculations are necessary by querying the values via MODBUS RTU. The required values can be easily read out and visualized in the LineMetrics Cloud.

The right choice of measuring device:

The rated current of the devices depends on the maximum current of the measured lines/system. In most cases, it is sufficient to inquire about the amount of protection and choose the next higher value for the measuring device.

Direct knives can usually be used up to a max. Current of 63A can be installed (Gavazzi), energy meters with transducer measurements can be designed for high currents depending on the type.

The cable cross-section and the space requirement in the distributor also play a role in the application.

Ideal use case:

Complete energy monitoring, load curves, power and current curves, voltage measurement, grid stability assessment, new installations, retrofits

Recommended Products: Energy Meter Gavazzi EM271, 3x Transducer Gavazzi TCD – Series

Pros and Cons of Energy Metering Devices:

+ Detailed analysis
+ Simultaneous measurement of multiple loads
+ Can be used for different types of mains (single-phase, two-phase, three-phase, three-phase)
+ Direct measurement or transducer measurement

– Short-term disconnection/shutdown necessary for installation