The Power Quality Meter that brings the Smart Grid within reach.

Capabilities that formerly required separate, expensive, specialized equipment and consultants – now available in a compact, affordable device.

OTELLO Vecto III Class A Multifunction Power, Power Quality & Synchrophasor Analyser



  1. Power supply
  2. Voltage Inputs
  3. Current Inputs
  4. Cellular Aerial
  5. Current Transformer
  6. Digital Inputs
  7. Wifi Connection
  8. Relay Outputs
  9. GPS Aerial
  10. Ethernet Ports
  11. Expansion Port

ANSI /IEEE Standard C37.2 – Standard for Electrical Power System Device Acronyms describing the OTELLO multi-function metering device

OTELLO records IEC 6100-4-30 Class A Edition 3 (2015) Power Quality standardized measurements of:

Meeting or exceeding the Class A requirements, plays an important role in providing accurate, reliable and comparable data. Access to this data facilitates accurate analysis and troubleshooting of power quality issues. Instruments lacking Class A compliance produce results that cannot be easily compared against each other. Class A compliant power quality metering instruments produce consistent data, giving technicians the confidence to accurately analyze complex power quality issues.

For both utility companies and large-scale, industrial energy users, it is critical to verify the quality of power and the source of non-compliance. Determining and solving the origination of power quality issues leads to a reduction of down-time, (lower cost) efficient energy use, fewer equipment failures and regulator compliance.

OTELLO Vecto III Class A Multifunction Power, Power Quality & Synchrophasor Analyser

Technical Specs

OTELLO is a comprehensive multi-function, single phase, dual-phase (split-phase), three-phase and Direct Current (DC) IEC 61000-4-30 Class-A Edition 3 (2015) Power Quality recorder with GPS-locked time synchronization.

The IEC 61000-4-30 Class-A standard defines the measurement methods, time aggregation, accuracy and evaluation, for each power quality parameter to obtain reliable, repeatable and comparable results. The standards are applicable in single-, dual- (split phase) and 3-phase AC power supply systems at 50 Hz or 60 Hz.

Additionally, the OTELLO instrument incorporates the IEC 62586-2:2017 definitions of the minimum set of parameters that must be implemented for Power Quality Instruments used in both portable and fixed installations. IEC 62586-2:2017 specifies functional tests and uncertainty requirements for instruments whose functions include measuring, recording, and monitoring power quality parameters in power supply systems, and whose measuring methods (class A or class S) are defined in IEC 61000-4-30.

It is a single feeder instrument with:

  • On-board GPS
  • 4 x voltage inputs
  • 4 x current sensor inputs
  • 4 x powered current transducer inputs
  • 2 x Gigabit Ethernet ports
  • On-board WiFi
  • 4 x digital inputs (5V power available)
  • 4 x digital outputs
  • Expansion port (USB2.0 High Speed)

Voltage inputs

  • Class A performance over all of the input range inclusive of 63.5 V (if L-N measurements are done in a 110 V line-line VT circuit)
  • 6 terminals are used for 4 voltage input channels with maximum input ratings of 600 V
  • The first 4 terminals connect 3 different phase voltages such as in a 3-phase system
  • Input channel 1-3 is referenced to a neutral (4th terminal) connection. This 4th terminal acts as a reference channel and can be any phase voltage if a 3-phase line-line voltage circuit is measured
  • If it is a 3-phase line-neutral voltage circuit, then the 4th terminal will be connected to the neutral voltage
  • The 5th and 6th terminal is the 4th channel and a fully differential (2 terminal) input channel

Number of channels: 4 x differential (3/4 Wire + 4th Diff) 

Measurement input range: 0-600VAC ±850VDC

Input impedance: > 1MΩ

Current inputs

  • 4 X 1/5 A CT inputs
  • 4 X 1 Vrms differential voltage transducer inputs with a 5 V power supply (to be used to power Rogowski coils)

Number of channels: 4 x galvanically isolated

Measurement input range: 0-6AAC ±8ADC

Max continuous current: 10ARMS

3 sec Overcurrent withstand: 50ARMS

VA burden @ 5ARMS: < 1VA

Galvanic isolation: 1kV

Current transducer inputs

Number of channels: 4 x differential 

Measurement input range: 0-1VAC ±1.5VDC 

Input impedance:  > 200kΩ

Digitisation of input signals

The question of sampling rates for Power Quality metering is an important one to consider.

Most power quality monitoring is reliably processed at sampling rates of 256 or 512 samples per cycle. However, fast transients can cause damage to sensitive equipment and malfunctions in manufacturing processes. Lower-end power quality meters cannot reliably detect these fast transients as they only sample dozens of times per cycle. A fast transient power problem can do damage in a few millionths of a second. In order to capture these transients, sampling rates in the order of millionth of a second would be required.

The European standard for Electrical Fast Transient (EFT) testing is EN-61000-4-4. The U.S. equivalent is IEEE C37.90. Both of these standards are similar.

Identifying very fast transients requires the use of specialized, portable monitoring equipment that costs up to $20,000—and frequently requires an outside consultant (plus travel & subsistence). Newer ‘next-gen’ power quality meters boast sampling rates up to 6MHz. But is this practical considering the fact that these fast transients can only be measured directly – typically on 400v networks?

With fixed installations, the bandwidth of Voltage Transformers (VT’s) and Current Transformers (CT’s) is way too low to correctly pass through fast transients. Unless broadband VT’s and CT’s are used, what is the use of a 6 MHz sampling rate, if the VT & CT only accurately passes through 2kHz data?

The other challenge with such high resolution data in fixed installations, is where does one store it – pushing that much data over a digital network is very resource intensive and costly.

The practical application for such high measurement frequencies is therefore very limited.

However; the way this functionality has been implemented on the OTELLO platform, the user can clearly identify the root cause of fast transients. The OTELLO device captures enough data to identify whether a fast transient originated from a switching event or from lightning. One can even detect whether it was a direct lightning strike or an indirect one (induced). This solves the high sampling rate question, as the primary goal of monitoring fast transients is the identification of the source.

Compliance with IEC 61000-4-30 Class-A, dips, swells and interruptions must be measured on a full cycle and updated every half cycle, enabling the instrument to combine the high resolution of half-cycle sampled data points with the accuracy of full-cycle RMS calculations.

Aggregation windows are when a power quality instrument compresses measured data at specified periods. A Class-A instrument must provide data in the following aggregation windows:

  1. The basic measurement time interval shall be a 10/12 cycle (~200 msec) at 50/60 Hz, note that the interval time varies with actual frequency.
  2. 150/180 cycles (~3 sec) at 50/60 Hz, note that the interval time varies with actual frequency.
  3. 10-min interval, synchronized with coordinated universal time (UTC) 2-hour interval for Plt flicker

OTELLO samples at 500 kHz on primary input signals. 50 kHz data is digitally retained and subjected to the IEC 61000-4-30 ED3.0 Class-A signal processing requirements.

Digital Inputs

Number of channels: 4 x galvanically isolated 

Max voltage input: 300VDC 

Digital Outputs

Number of channels: 4 x galvanically isolated 

Max voltage input: 300VAC, 100mAAC

Sampling Accuracy & Bandwidth

Overall accuracy: 0.1% on reading (10%-100%) 

Power frequency measurement range : DC, 40-60Hz, 50-70Hz

Harmonic & interharmonic bandwidth: 1-64th, 2-9kHz

Synchronised data sampling rate: 500kHz

Fast transient capturing: >20μs

ADC Resolution: 16-bit

Time Stamping

External time synchronization is required to achieve accurate timestamps, enabling accurate correlation of data between different instruments. IEC 61000-4-30 ED3.0 Class-A accuracy is specified with ± 20 ms for 50 Hz and ± 16.7 ms for 60 Hz instruments, regardless of the total time interval. The OTELLO multi-function metering device provides permanent ~100ns accurate to absolute-time clock-synchronisation using the built-in GPS. This provides industry leading accuracy when troubleshooting power quality issues and analysing grid wide data.

GPS clock sync accuracy: ±100ηs (from absolute time) 

PTP clock sync accuracy: ±1μs (from absolute time) 

NTP clock accuracy: ±1ms (from absolute time)

Built-in clock accuracy: ±1ppm (32 sec per annum)


  • Communication is via built-in Ethernet, WiFi or Cellular Data Networks.
  • Modbus over Ethernet
  • DNP3 over Ethernet
  • IEC 61850 – optional

The device also support open sFTP and REST server based protocols enabling them to be placed under control of other 3rd party software systems. OTELLO supports data imported from 3rd party devices using open formats like PQDIF, Comtrade and CSV files.

Security: Permanent 128-bit, end-to-end encryption

Ethernet: 2 x Gigabit ports 

WiFi: 802.11 a/b/g/n/ac (Hotspot or Client)

Cellular (Optional): Sierra Wireless HL series 

PTP support: IEEE1588

POE Plus support: IEEE802.3at (30W)(48V)

Data Storage

8GB on-board storage providing data storage of all IEC 61000-4-30 voltage and current 10-minute values up to the 64th harmonic

Advanced Triggering

User-configurable triggering between different instruments: the patented XrossTrigger® feature

Power Supply

Power consumption (max): < 20VA

Supply voltage: PoE and/or 90-300VAC, 100-300VDC power factor corrected power supply

Supply frequency: DC, 42-69Hz

On-board battery: LiFePO4 – 1/2 hour power failure ride-through

Charge/discharge cycles (min): 2,000


Electrical isolation class: 600V Class II

Dimensions: 250mm x 135mm x 65mm (L x W x H)

Mounting options: DIN rail & wall mount

USB2.0 expansion port (powered): High speed (480Mbit)



Download the spec sheet

For detailed information on OTELLO’s specs and capabilities, download the PDF now.

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