Detection of Sags, Swells, and Transients (PM8000 and ION9000)

[Tomohiro-Okada]

Hi,

I have two questions regarding sags, swells, and transients detection.

Question 1:
Regarding the detection of sags (and transients), I would like to clarify the following:
For example, when detecting a sag with a nominal voltage of 100V and a detection threshold of 90%, does the detection occur when the voltage reaches exactly 90V (e.g., 90.00000V)? Or does it only get detected when the voltage drops below 90V (e.g., 89.99999V)?
Since it is difficult to test this behavior using generators or other equipment, I am seeking confirmation regarding the internal specifications.
Additionally, I would like to know if the same detection logic applies to transients.

Question 2:
While reading the ION reference documentation on the Sag/Swell module, I found the following passage:

"T1: This is the beginning of the disturbance as well as the beginning of the first sub-disturbance. At 80%, the voltage is far below the necessary sag limit of 88% (considering the 2% hysteresis). At this point, the output registers are:"

This passage states that the necessary sag limit is 88%, considering the hysteresis. However, as part of the graph example mentioned in the text, I also found this description:

"In this example, the nominal voltage is 120V, the ChangeCrit setup register is set to 10%, the Sag Lim is set to 90%, and the Hysteresis is set to 2%."

Based on my understanding, with these settings, the system should detect a sag immediately once the voltage drops below 90%. However, is there a possibility that the hysteresis could influence the initial detection point of a sag?

Thank you in advance for your support and clarification.

Best regards,
@Tomohiro-Okada 

[Mehran_Mehrnia]

Hi @Tomohiro-Okada 

1- As already mentioned, for example, in the definition of 'Sag Lim' in the ION Reference:
"This register specifies what limit any of the inputs must fall below for the DistState output register
to change to TRUE."
Which means in your example, the Sag occurs when voltage drops below 90V (e.g., 89.99999V). If voltage is 90V, the Sag is not detected.

The same applies to the Transient Module.

2- It might be a bit confusing, but hysteresis is only considered when the meter is in a Sag or Swell state. This state ends when the voltage reaches the threshold plus hysteresis for a Sag, or the threshold minus hysteresis for a Swell. Therefore, meter detects a sag immediately once the voltage drops below 90%.

ION Reference -> Sag/Swell Module:

Best Regards,

-Mehran

L3 Expert Advanced metering

[Charles_Murison]

Hello @Tomohiro-Okada ,

One item to note for the PM8000 and ION9000 meters, the transient module is waveshape detection.

Regards,

Charles

[Tomohiro-Okada]

Hi @Mehran_Mehrnia,

Thank you for your prompt reply.

I understand the detection of sag/swells and transients.

I have one more question: Is the recovery process the same after detecting them?

For example, when detecting a sag with a nominal voltage of 100V and a detection threshold of 90%, with a hysteresis setting of 2%, the detection occurs when the voltage reaches 89.99999V (for example), and recovery happens when the voltage reaches 92.000001V.

Regards,
Okada

[Mehran_Mehrnia]

Hi @Tomohiro-Okada 

You're welcome.

No, once the voltage hits the limit for example for Sag which is Threshold + Hysteresis(in your example 92.0), the meter enters into non-Sag/Swell state (recovery process).

Best Regards,

-Mehran

L3 Expert Advanced metering

[Charles_Murison · Accepted solution]

Hello @Tomohiro-Okada ,

To the question "Is the recovery process the same after detecting them?" I take this question to mean does the voltage have to be greater than or equal to settings for the sag to be considered over? The answer is greater than.

Regards,

Charles

[Tomohiro-Okada]

Dear @Charles_Murison 

Thank you very much for your detailed explanation.
I now understand that the sag status is regarded as recovered when the voltage value surpasses the hysteresis threshold (specifically "greater than," not "greater than or equal to").

Best regards,
Okada

[Tomohiro-Okada]

Hello @Mehran_Mehrnia

Thank you for your reply!

I understand the threshold of sag/swells and transients.

Regards,

Okada

[Mehran_Mehrnia · Accepted solution]

Hi @Tomohiro-Okada 

You're welcome.

Here is the result of the test I did:

Nominal Voltage: 120, Sag Lim: 90, Hysteresis: 2 

1- When meter is not in Sag state and once voltage falls the Threshold(LESS than 108=0.9*120), meter enters the Sag state.

2- When meter is in Sag state and once voltage touches the Threshold+Hystersis(110.4=0.92*120), meter enters into none sag state.

Best Regards,

-Mehran

L3 Expert Advanced metering

[Sreemant_Roy]

@Tomohiro-Okada  : Once we have come to terms with the sag and if the client needs a resolution, then remember we have a solution for Sag Elimination.

Check out the Discover PowerLogic Dynamic Voltage Restorer ( DVR ) 

[Tomohiro-Okada]

I understand the test results now.

I can explain them to our customers.

Regards,

Okada

[Tomohiro-Okada]

Hello @Sreemant_Roy 

Thank you for your information!

Regards,

Okada