Portable Phasor Measurement Units

STER PMU portable phasor measurement unit is the integral part of the WAMSTER synchrophasor system.

STER PMU is an easy to use, portable (handheld) synchrophasor measurement unit (PMU) with a rechargeable battery backup and SD flash memory for more than 4 months of synchrophasor data. Contrary to a classic PMU unit, it needs no additional infrastructure to operate - it can use GPRS/UMTS to send data to a cloud server, or integrate with existing IEEE C37.118 equipment.

Portable PMU unit: Key features

Easy startup

For the end user, all the equipment necessary to start recording synchrophasors is included in a soft carrying bag: It takes only a couple of minutes to setup the wiring and signal ranges, as well as configure the SIM card settings and connect to the Internet. STER PMU can also be attached to the (optional) magnetic baseplate which is designed to pre-wire the device to the GPRS modem using as little area as possible, allowing instant attachment to switchboard doors and backplanes.

Simple setup

Equipped with a 3.5" backlit LCD display, all settings are easily visible and adjustable using the graphical user interface. This makes it simple to configure voltage and current transmission ratios, monitor real-time voltage and current synchrophasor measurements as well as diagnose and troubleshoot problems.

Battery operated

Wamster system is ideal for analyzing synchrophasor data during blackout conditions. Rechargeable battery can keep the portable PMU device operating for more than 4 hours without supply, including the supply for the GPRS modem. If the communication also breaks, device will continue storing measurements locally and report them to server when the connection is restored.

Up to 32 GB of SD flash memory

Without the SD card, internal flash memory is sufficient for storing around 2 hours of 4-phase synchrophasor data cyclically (at full reporting speed, 60Hz). If a 32 GB SD memory card is used, more than 4 months of synchrophasor measurements can be stored locally. This makes it even possible to use the device for offline scenarios and analyze data by retrieving it directly from the memory card.

Continuous Waveform Recording

Using a 32GB SD card, device can store 4 days of oscillograms (waveforms) for all channels, along with synchrophasor measurements at synchronous frequency. Additionally, the device records 10-min harmonic/THD aggregates (min/max/avg). Grouping multiple PMU devices into a single campaign using the WAMSTER system enables automatic retrieval of synchronized oscillograms from multiple locations in case of events, allowing detailed insight into the system operation.

Standard equipment

A single STER PMU measurement set (Fig. 3) includes:

Description	Quantity
PMU unit	1
3 phase 5A/1V measuring transformer	1
Test probe, red	3
Test probe, black	1
Crocodile clip, red	3
Crocodile clip, black	1
Voltage measurement lead, red	3
Voltage measurement lead, black	1
Voltage measurement lead, green	1
Power supply adapter	1
GPRS class 10 modem with connection cable	1
GPS unit	1
1.2 V NiMH rechargeable battery	6
Soft carrying bag	1
Instruction manual	1
Calibration certificate	1

Technical specifications

Measurement inputs	4 voltage inputs (3 phases, earth), 3 ranges: 150V, 300V, 1000V 4 current inputs: xx A /1V, 2 ranges: 100%, 10% default current sensor: 5A/1V A1037 measurement transformer optional current sensors: current clamps with nominal currents from 5A to 3000A, measurement class: 1 (high currents) or 2 (low currents).
Basic measurement accuracy	Voltage RMS accuracy: 0.2% of reading Current RMS accuracy: 0.5% of reading (using default current sensor)
Synchronized phasor measurements	Measurement result tagging according to C37.118 specification Accuracy: TVA < 1% with default current sensor Max. reporting rate: synchronous (50/60 synchrophasors frames per second)
Power quality measurements	8 channel 3.2kHz continuous waveform recorder, circular buffer (4 days with 32GB card) 10-min voltage and current harmonic/THD aggregates (min/max/avg)
Local non-volatile memory autonomy	32 GB, sufficient for 4.5 months of measurement results saved at synchronous reporting rate, or 32 GB, sufficient for 4 days of synchrophasor measurements and 4 days of waveforms, or 64 GB, sufficient for up to 9 months of measurement results saved at synchronous reporting rate, or Other capacities can be used on request, disabling certain channels can also increase max. capacity.
Communication reporting rates	50 Hz (1-2-5-10-25-50 fps) 60 Hz (1-2-5-10-12-15-20-30-60 fps)
Safety standards	EN 61010-1: 2001 Safety requirements for electrical equipment for measurement, control and laboratory use
Overvoltage protection	1000 V / CAT III; 600 V / CAT IV
Protection class	double insulation
EMC standard	EN 61326-2-2: 2006 Electrical equipment for measurement, control and laboratory use Emission: Class A equipment (for industrial purposes) Immunity for equipment intended for use in industrial locations
Communication link	GPRS modem class 10
Time source	GPS PPS – error < 3µs internal clock – error < 2s/day
Display	monochrome LCD, 320x200 with backlight
Battery backup	> 8 hours as a standalone device > 5 hours if supplying GPRS modem with power
Auxiliary power	80-260V, 50/60 Hz
Dimensions	220 x 115 x 90 mm
Weight	0.65 kg