Regarding the "Phase V watchdog" settings of the HDPM6000 web interface

[T.Okada]

Hello,

I have a question about the "Phase V Watchdog" setting in the HDPM6000 web interface.
At our customer’s site, voltage measurement is not used.
When the "Phase V Watchdog" is enabled under this condition, the HDPM6000 reboots every minute, which appears to cause instability.

To prevent this, we would like to disable the "Phase V Watchdog."
Could you advise on the impact or potential risks of disabling this feature?
If there are recommended settings or best practices for systems without voltage measurement, please let us know.

Regards,
Okada

[Charles_Murison]

Hello @T.Okada ,

In the Head unit install guide there is a line on page 22

"Disable the voltage watchdog in the General Settings tab if the meter voltage inputs are zero, during commissioning or maintenance."

The watchdog is doing exactly what it was designed to do. Reboot the meter if voltage readings are zero.

given you know that no voltages are being used I would recommend disabling the watchdog.

Regards,

Charles

[Mehran_Mehrnia]

Hi @T.Okada 

The Phase V Watchdog is designed to monitor the voltage reference inputs (P1, P2, P3, N). When enabled, the watchdog will reboot the meter every minute if no voltage is detected on the voltage inputs.

The HDPM6000 is a power meter and designed to operate with three key connections:

1. Voltage reference inputs
2. Power supply
3. CT inputs

The installation guide states that all three components are required for normal system operation. The voltage reference is used for many core metering functions, including voltage, power, energy, power factor, frequency, voltage alarms, power quality measurements, and waveform capture functions.

For applications where no voltage reference is intentionally connected, leaving the Phase V Watchdog enabled will result in the behavior you are observing, namely a periodic reboot every minute due to the absence of detected voltage. The guide specifically instructs users to disable the voltage watchdog when voltage inputs are zero during commissioning, maintenance, or firmware upgrade activities.

If the watchdog is disabled:

• The HDPM6000 will no longer reboot when voltage is absent.
• The meter will not automatically detect and recover from voltage-reference-related issues such as:
  • Loss of source voltage
  • Blown voltage fuse or breaker
  • PT secondary failure
  • Disconnected voltage wiring
  • Voltage reference wiring faults

• Any measurements or functions requiring voltage inputs will remain unavailable or invalid.

Therefore, if the application is intentionally configured without voltage measurement, disabling the Phase V Watchdog is the practical recommendation to prevent unnecessary reboots. However, this is outside the normal metering configuration described in the installation guide, and the customer should be aware that voltage-dependent measurements and power quality functions will not be available.

Best Regards,

-Mehran

L3 Expert Advanced metering

[T.Okada]

Hi @Mehran_Mehrnia,

Thank you for your reply!

There is one thing I don’t fully understand.

I understand that the V watchdog operates when there is no voltage,

but even if the meter restarts as a result, the input voltage to the voltage measurement remains at 0.

Therefore, I don’t think measurements that rely on voltage can function properly after a restart, and I’m not sure what the benefit is. Do you know the reason?

As a non‑expert idea, if we have to toggle the V watchdog on and off for maintenance or updates,

it seems like leaving it off from the start wouldn’t make much difference.

In fact, I’m concerned that repeated restarts while the voltage is zero could affect the current measurements that are functioning and the communications with the central monitoring system,

which makes it feel like there are only disadvantages.

If turning off the V watchdog has a significant impact on the system,

I’m willing to keep it on; however, if there aren’t major downsides,

would it be acceptable to leave it off even in a system that performs voltage measurements?

One more clarification: regarding the watchdog, does the “restart” mean a software reboot inside the meter rather than a complete power-off of the control power supply?

Regards,

Okada

[T.Okada]

Hi @Charles_Murison,

Thank you for your response.

As you mentioned, if our customer does not need voltage measurements, we will disable the V watchdog.

By the way, starting from firmware version v0.66.0, we can display the current value even without a voltage input. In this case, if the customer does not need voltage measurements, is it acceptable to leave the voltage terminals unconnected?

Regards,
Okada

[Mehran_Mehrnia]

Hi @T.Okada 

The Phase V Watchdog is primarily intended to detect and recover from an unexpected loss of voltage reference in installations where voltage should normally be present. If the system is intentionally operated without voltage inputs, the watchdog cannot restore voltage-dependent measurements, so disabling it is typically the preferred approach to prevent continuous reboots.

The restart is an internal meter reboot, not a removal of external control power. For installations that use voltage measurement normally, it is generally recommended leaving the watchdog enabled.

Yes. Starting with HDPM6000 firmware v66.0, the behavior where current was reported as zero when the corresponding voltage input was zero was corrected. As a result, current measurements can now be displayed even when voltage inputs are not connected.

Therefore, if the customer's application only requires current monitoring and does not require voltage or other voltage-dependent measurements, it is acceptable to leave the voltage terminals unconnected. In this case, disabling the Phase V Watchdog is also recommended to prevent unnecessary reboots caused by the intentional absence of voltage inputs.

Best Regards,

-Mehran

L3 Expert Advanced metering

[T.Okada]

Hi @Mehran_Mehrnia ,

Thank you for your reply.

I understand about the "Phase V watchdog" settings under the system without using voltage measurements.

but I still don’t fully understand the intent of the statement that the Phase V Watchdog is designed to detect and recover from an unexpected loss of voltage reference in installations where voltage should normally be present. Even if the HDPM restarts after detecting an unexpected loss, I don’t see how that would change the fact that the measured voltage is still missing, so I’m not sure what the restart is meant to accomplish.

If I can’t understand that point, it seems cumbersome to toggle the setting on and off during maintenance when no voltage is applied, so I’m inclined to think there’s no particular need to keep it enabled. Would that be acceptable? Or could leaving it disabled cause any issues?

Regards,

Okada

[Mehran_Mehrnia · Accepted solution]

Hi @T.Okada 

Your understanding is reasonable. If there is intentionally no voltage connected to the HDPM6000, a restart by itself will not restore the missing voltage. Therefore, in that situation, the Phase V Watchdog is not expected to change the measurement result, since the voltage source is still absent.

The intent of the Phase V Watchdog is generally to provide a recovery mechanism for situations where voltage is expected to be present but the system encounters an unexpected condition that results in the loss of a valid voltage reference. In those cases, the watchdog attempts to recover normal operation automatically.

In our testing, with the Phase V Watchdog enabled and no voltage connected to the head unit voltage inputs, we observed that the device periodically entered a recovery cycle. During this process:

• Voltage measurements remained at 0 V.
• Current measurements briefly dropped to 0 A.
• Diagnostic messages such as PT wiring or phase setting errors appeared.
• The display then returned to normal operation.

However, because no voltage source was actually present, the recovery cycle did not restore a voltage measurement. This is consistent with your observation that a restart cannot create a voltage signal that is physically absent.

If your application does not use voltage measurements, and the voltage inputs are intentionally left disconnected, then leaving the Phase V Watchdog disabled would generally be a reasonable approach. Doing so would also avoid the periodic recovery cycles that occur when the watchdog continuously detects the absence of voltage.

Based on our testing, we are not aware of any adverse impact to current-only monitoring caused by disabling the Phase V Watchdog when voltage inputs are intentionally unused. The primary consequence is simply that the watchdog will no longer attempt to recover from a missing voltage condition.

Best Regards,

-Mehran

L3 Expert Advanced metering

[T.Okada]

Hello @Mehran_Mehrnia 

Thank you for your reply.
I understand that the "Phase V watchdog" setting is intended to prevent the head unit from malfunctioning.

Regards,
Okada