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What is Maximum Demand Measurement?

Demand is a measure of average power consumption over a fixed time interval. Maximum (or peak) demand is the highest demand recorded over the billing period. The billing period is mostly end of the month.

Non-domestic electrical power users often have to pay a maximum demand charge in addition to the charge for the consumed energy. This additional charge is based on the highest amount of power used over a period (e.g. 15 minutes) during the billing period.
Sometimes the surcharge can also be related to the load-factor.

CLOU meters can operate with a fixed window or with a sliding window. Please note that not all meters have this function.

What is the difference?

The fixed window is defined in certain steps (e.g. 15 minutes), starting at the full hour. It can be programmed for the following fixed intervals:

  • 5 minutes
  • 15 minutes
  • 30 minutes
  • 60 minutes
  • At the end of each fixed window period, the average power for that period is calculated. If this value is higher than the already existing value, it is stored as the MD (maximum demand).

The sliding window is the CLOU default setting. For sub integration period the default is 1 minute.

At the end of a sub integration period the average power is calculated for one integration period. If this value is higher than the already existing value then this is stored as MD. The integration period slides by a window of the sub integration period.

The maximum demand register MD will be reset at the set transferring time of each month (e.g. 1stof each month). The demand values measured with 6 digits, including 4 integers and 2 decimals.

What is the impact on using different intervals and sub-intervals?

In the example below we are generating a 24 hour load-profile. It’s based on values between 30% peak and peak. (1440 samples)
Then we run a evaluation of the MD (maximum demand) for various meter settings. All fixed windows starting at midnight (00:00).

What do we learn?

  • The shorter the integration period, the higher the MD value
  • The shorter the sub-interval in the integration period, the higher the MD value (except of some strange profile constellations, you might find them)

What are the right settings?
It depends on the purpose for the demand measurement.
If you want to give a penalty to customers exceeding a defined limit, you need to follow the utility rules (e.g. 30 minutes fixed window).

If you are operating with an AMI system, you want to do a load-prediction (forecast) for a period of time. Here it is very common to use a 15 minutes integration time with 1 minute sub-intervals.

new random load profile
MD Limit kVA
Peak load kVA
Integration period 5 minutes
Integration period 15 minutes
Integration period 30 minutes
Integration period 60 minutes

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12 Replies to “What is Maximum Demand Measurement?”

  1. Hello
    Thanks for the article.
    I have a question.
    How do meters calculate the maximum demand by Ampere in three phase meters.
    For an example :
    Va =220, Vb =220,Vc=0
    Ia=95, Ib=95,Ic=0
    The max demand by KW will be 41800 watt.
    But what is the max demand by Ampere in this example.
    Thanks in advance.

    1. Thank you for your question, Mahmoud. Maximum demand is always expressed as power. This power is recalculated from the consumed energy over a time period. Typical maximum demand periods are 15 minutes or 30 minutes. During these periods you have voltage fluctuations, different currents and different power factors.
      Less expensive energy meters will give you only the maximum demand value. Advanced meters have different registers to record the minimum-, average- and maximum values for voltages, currents, phase angles and frequency during the period.

  2. Hi sir, if i want to see % error of the maximum demand using test bench, so what need to do? let say for example, V=230V, I=20A. i need to set the integration time and sliding?

    1. It depends on how comfortable your test-bench is. The procedure is the same as for a register test. You read the maximum demand register of your meter. If the meter was already used, reset the register first. Then you inject with your test bench 230 V and 20 A for your meter integration period (usually 15 minutes). Once finished, you read the demand register again and compare with the power indicated at the reference standard.
      If your reference standard shows only the energy, you divide this value by the integration period.
      Now you use the common error calculation formula.
      error calculation
      Theoretical value is your reference standard reading, experimental value is your meter reading.
      Modern test benches can do this automatically. I suggest, you check with your manufacturers operation manual as well.

  3. So far I thought that MD is the peak or max instantaneous KVA which we draw from the system for the specified time period.
    But is it the average KVA value over a time period??

    1. It’s always the average power for the selected interval time (integration period). The shorter the time interval, the higher is the MD for the same load profile.

  4. Sir i have doubt that the meter is taking
    the value of KVA at 5 min or value obtained at 5min is integration of 1s value.

    1. The meter itself has a fixed integration time for energy recording. It’s typically 500 ms. This energy is incremented for the selected time period (in your case 5 minutes) and divided by the time period. Then we have the power (kVA) for this period.

    1. The maximum demand measurement is mainly implemented for big consumers. It’s helpful for utilities to avoid big peaks by giving a penalty for exceeding given limits. Now you can find many domestic meters in the market with this feature but it’s rarely used for home.
      Nevertheless, together with an AMI system the retrieved data are helpful for planning of power generation.

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