Skip to content
Holt Systems

Lost a phase overnight? A 3 phase power failure alarm texts you

A phase relay at your switchboard and current sensors on four motors text the right people when supply or one phase drops.

  • WatchesEach phase and four motors
  • You getA text and email in minutes
  • Sends byStarlink or 4G, no site wifi
Price a plant power failure alarm See the SMS alerts or call 07 2150 3666
Plant power alerts

  1. 1:32 am

    Main board phase L2 lost for 2 min. L1 and L3 up. Effluent pump 16 A, up from 11 A. Check supply.

  2. 1:37 am

    Main board L2 still lost, no ack after 5 min. Sent to all nominated people.

  3. 5:35 am

    Main board supply restored and stable. L2 was out 4 h 03 min. Effluent pump 11 A.

Example alerts from this system

about 320,000

People were left without power when ex-tropical cyclone Alfred hit in March 2025, reported ESD News.

Source: ESD News

964 min

The yearly outage limit per customer on Ergon's long rural feeders, with up to 7.40 interruptions allowed.

Source: Business Queensland

28 Oct 2024

The day Telstra and Optus switched off 3G, which stranded older plug-in alarms.

Source: business.gov.au

One phase drops at 1:30 am and the lights stay on

A 3 phase power failure alarm matters most when the plant runs with nobody on site. Supply, or just one phase, can go at 1:30 am and nobody knows.

Lights and the PLC stay up. Three phase motors keep humming on the two phases left, and they run hot. Day shift finds stopped lines.

A plug-in alarm sees one outlet on one phase. It won't tell you a motor feeder has tripped.

  • Motors left single phasing overheat their windings, reports Macromatic, a US controls maker.

A six hour overnight outage, worked out

  • 120 kW average load and a 6 hour unplanned outage.
  • The Australian Energy Regulator's reported 2024 value for industrial businesses under 10 MVA, $33.49 per kWh.
120 kW x 6 h720 kWh
720 kWh x $33.49 per kWh$24,113

About $24,000 as a scale check. Your real figure is your own lost batches, labour, restart, cleaning and missed orders. An alarm won't stop the outage, but it cuts the time before someone acts.

What we fit at the switchboard

  • Phase monitoring relay

    Sits across L1, L2 and L3 at the incomer and opens a contact when any phase is lost.

    Alert after 1 to 2 min

  • Motor current sensors

    Clamp four motor feeders to show a tripped breaker, blown fuse or single phasing.

    4 motor circuits

  • Battery sensor node

    Reads the relay contact and keeps sending after supply drops.

    Heartbeat every 20 min

  • Gateway on battery

    Picks up every sensor by radio and passes it on, with its own battery.

    Offline alert at 10 min

  • Starlink or 4G backhaul

    Sends the text out, so you don't need site wifi.

    Starlink or 4G

How a 3 phase power failure alarm works at your switchboard

3 phase power failure alarm at a food plant main switchboard Single line diagram of a food plant main switchboard, with a night strip below. A three phase utility incomer feeds a motor control centre busbar. A phase monitoring relay across L1, L2 and L3 on the incomer side passes a dry contact to a sensor node with its own battery. Four motor circuits leave the busbar, each with a current sensor: a wash-down pump, an air compressor, a boiler feed pump and an effluent pit pump. A UPS or generator feeds the PLC and controls only, not the motors. The node and the four current sensors send LoRaWAN radio, shown dashed, to a gateway on its own battery, then by Starlink or 4G to SMS, email and a dashboard. The night strip runs from 6 pm to 6 am. In a total outage from about 9 pm to 11:30 pm, L1, L2 and L3 drop together, the pump motor current falls to zero, and an SMS reports supply lost. In a later event from about 1:30 am to 5:30 am only L2 drops while L1 and L3 stay up, the pump motor current climbs, and an SMS reports L2 lost. Heartbeat messages continue through both events, and 50 minutes without a heartbeat raises a site silent alert. Main switchboard and MCC Utility incomer Phase relay L1 L2 L3 Node own battery UPS or generator PLC, controls only M Wash-down pump M Air compressor M Boiler feed pump M Effluent pit pump Gateway on battery Backhaul Starlink or 4G SMS, email, dashboard Orange: monitoring we add LoRaWAN radio link One night, two events Total outage SMS: supply lost One phase lost SMS: L2 lost L1 L2 L3 Heartbeat Motor current Stopped Amps climb 6 pm 12 am 6 am 50 minutes without a heartbeat: site silent
Single line diagram of a food plant main switchboard, not to scale, with a night strip comparing a total outage with the loss of phase L2. Orange marks what we add. Dashed lines are LoRaWAN radio to a gateway on battery, then Starlink or 4G to your phones.
  1. 1

    A relay watches every phase

    A phase monitoring relay across L1, L2 and L3 at the incomer opens a dry contact when any phase goes.

  2. 2

    Sensors watch four motors

    Split core current sensors clamp the wash-down pump, air compressor, boiler feed pump and effluent pit pump.

  3. 3

    Radio to the gateway

    A battery node sends by LoRaWAN radio to a gateway on its own battery, so it keeps going when supply drops.

  4. 4

    Starlink or 4G sends the text

    The gateway texts and emails your nominated people. If it goes quiet for 50 minutes, a site silent alert follows.

What lands on your phone when a phase drops

Effluent pit pump current

Dashboard view

Phase L2
Lost
Effluent pump
16 A
Wash-down pump
12 A
11 13.6 16.2 Above the commissioned band 12:301:302:304:005:35 A
Example values for one motor. We set the band for each feeder at commissioning.

Today versus with a 3 phase power failure alarm

TopicTodayWith monitoring
One phase lostA plug-in alarm sees one outlet and misses itA relay across all three phases texts you
A tripped motor feederFound when the line stopsCurrent drops to zero and you get a text
Backup on the controlsThe panel looks healthy while motors sit stoppedIndependent of your PLC, so it still speaks up

What it costs

We set a fixed price after a short scoping call or a site visit. It depends on how many sensors, how far the switchboard is from the gateway, and how the site gets online. Ongoing support is available as a plan after handover.

Price a plant power failure alarm

The fixed price covers

  • Gateway, battery and Starlink or 4G backhaul
  • Installation and electrical work under QLD Electrical Contractor Licence 1513082
  • Alert set-up, recipients, escalation and a simulated supply loss test
  • An ongoing support plan: we keep it running, replace batteries and sensors, and tune alerts

On a food plant switchboard

We walk the switchboard with your maintenance lead and plan isolation around production.

Want to catch a failing bearing before the line stops? Add food conveyor bearing monitoring. Running bulk gas? See bulk LPG tank monitoring.

For the pump side, see pump motor current monitoring. Flour on site? Try flour silo level monitoring.

Stainless steel process valves and pipework in a food plant
Illustrative photo. Photo: Policarpo Brito on Pexels

What this alarm won't do

  • It supplements your PLC, SCADA and motor protection. It tells people, and it doesn't trip or restart anything.
  • It can't say why supply failed unless we monitor more points. Brownouts and flickers shorter than the debounce won't alert.
  • The gateway battery is finite and texts only reach phones with coverage, so we use two recipients and email.

With you every step

How the five stages go on a plant switchboard.

  1. 1

    Discovery

    We walk the switchboard and MCC with your maintenance lead, note the supply and motor feeders, and test radio, Starlink sky view and 4G.

  2. 2

    Design

    You get a written scope: the relay, the motor circuits, the debounce, who gets texts and the isolation windows.

  3. 3

    Build and test

    We bench test the relay, sensors, gateway and battery, including a simulated phase loss, before any work at your board.

  4. 4

    Install and commission

    We do the electrical work under licence 1513082, simulate a supply loss under safe isolation, and time the text on your phones.

  5. 5

    Ongoing support

    You get the alert list, test log and dashboard, a weekly test message is set, and we stay on for changes and support.

Why Holt Systems

We design, install and commission every system ourselves, then look after it with an ongoing support plan. Monitoring supplements the site's own control, protection, fire and safety systems; it does not replace them.

Alerts
SMS to any phone, no app
Based in
Brisbane, QLD
Electrical licence
QLD 1513082
After install
Ongoing support plans
Call
07 2150 3666

3 phase power failure alarm questions

Can the alarm tell me when only one of three phases has failed?

Yes. A phase monitoring relay across L1, L2 and L3 at the incomer opens its dry contact when any phase is lost, and the LoRaWAN node reports it. A plug-in alarm usually sees one outlet on one phase.

Will the alarm still work when the plant has no power?

The node has its own battery, and the gateway and backhaul run from a battery. On an assumed 1,280 Wh battery, 80 per cent usable, a 4G gateway drawing an assumed 8 W runs about 5 days.

Does it replace our PLC, SCADA or motor phase protection?

No. Your PLC, SCADA and any phase failure relays on the motors stay in place. A motor relay trips the motor; this alarm tells people. It's independent of the PLC, so a controller fault doesn't silence it.

Is a plug-in GSM power failure alarm enough for a plant?

It sees one outlet, usually on one phase, runs on a small internal battery and needs mobile coverage. Telstra and Optus switched off 3G on 28 October 2024, so check whether an old unit was 3G only. It can't see a tripped motor feeder.

How do we know the alarm itself is still working?

A weekly test message goes out at a fixed time and is logged. The node sends a heartbeat every 20 minutes, and 50 minutes without one raises a site silent alert. A gateway offline for 10 minutes does the same.

Sources

  1. Values of customer reliability: final report, 2024 VCR review (18 December 2024), Australian Energy Regulator
  2. What is a phase loss?, Macromatic Industrial Controls
  3. Minimum service standards reporting (SAIDI and SAIFI limits for Ergon Energy and Energex), Business Queensland
  4. More than 300,000 without power in wake of ex-TC Alfred (10 March 2025), ESD News
  5. Queenslanders urged to Get Ready for storm season (8 October 2018), Queensland Government statements
  6. Permanently connected generators, Queensland Electrical Safety Office
  7. The 3G network is closing down, business.gov.au

Price a plant power failure alarm

Tell us what you need to watch and where. We confirm the sensors, gateway location and alert recipients, then give you a fixed price.

Or email hello@holtsystems.com.au

Your details are handled in accordance with our privacy policy.

  1. 1

    Tell us about the site

    A few lines on the assets, distances and what you need to know about.

  2. 2

    A call to scope it

    We confirm the sensors, gateway location and alert recipients, and whether a site visit is needed.

  3. 3

    Fixed price

    You receive a defined scope and a fixed price before any work starts.

This problem in other industries

Related services