How to Calculate Maximun Demand

whats the meter used?

whats the tariff?

MD MVA or MD MW?

what about normal,peak and off-peak M.D?

Sounds to me like you are being billed on your maximum recorded peak demand.

It is common for utilities to record the "maximum" demand seen by a larger customer (such as one with a 22KV feed), and use that demand value as the "billing" for the entire year. Most utilities will "reset" the maximum demand to the current maximum once per year. At least that is the practice of most of the utilities here.

You can not calculate it. If you had a demand of 6347kw for 30 minutes, or what ever time period the utility uses, and demand dropped you would still be billed the 6347 kw. Utilities have different ways to bill demand.

GA!!

If I may, Most utility companies such as our provider out here PG&E has a free on line site. It is called inter-act, out here. They provide a login and Password so that you can view your utility consumption daily. They will also have the tariff list there for you to look at informing you of when and how much your demand charges are at any particular time.

Demands are usually rated "Peak" 6am to noon, Regular noon to 7 PM, and off peak 7 PM to 6 AM. However I am sure that it varies for each utility provider. Peak being the greatest charge monetarily.

The power consumption is graphed daily explaining the demand, and usages in the graphs. We have signed up a few of our customers for this system after we installed an automation system. The customer used to power up the AHU's (air handling units) chillers, boilers and the outer building packaged units at the same time. The demand as you can expect for the first 30 min of the day (start time was 6 am) was killing them during the highest peak time. They were just using a central time clock system to power the building. Once the automation system was installed the Demand charges were able to be controlled (as far as the meter not seeing a huge inrush of power). This scheduling of equipment start and run times resulted in a first year pay back ROI of $23,750 in utility savings. Since then we have completed lighting and other projects continuing their savings.

Hope that helps a bit and work with your provider.

Dear Mr. Aikhh,

Generally the Ht consumers are provided with two part tariff, i.e.,billed for consumption at the rate per KWh and for the maximum demand availed at rate per KW/KVA demanded at the maximum during the month.<p>

To arrive at the maximum demand , following procedure is adopted.<p>

Maximum demand is arrived from maximum demand availed by the customer,<p>

We cannot take instantaneous values of demand for this purpose, as this will be grossly erroneous. For example if you take the case of a 15hp/10 KW motor,the KVA demand for starting this motor may be as high as 75 KVA for short period, but it is not the true demand.<p>

To optimally decide on the demand by the customer following procedure is adopted.

The consumption for a selected period (say 15 minutes or 30 minutes) is summated and based on this data his demand is calculated.<p>

For example if you are operating 100 kw load for 15minutes, a consumption of 25 units will be recorded and for half an hour it will record 50 Units. Your demand can be arrived by multiplying your 15 minutes consumption by 4 (25 x 4 =100) or your 30 minutes consumption by 2 (50 x 2 =100)<p>

Suppose you are using 100KW for first half an hour and it is recorded in the maximum demand registry.During second half an hour if your demand is 75 KW, it will arrive at the demand and as it is less than already recoded demand, it will ignore the same.If during the third hAlf an hour you are using 105 KW, then the fresh higher demand of 105KW will be recoded replacing the old 100KW record <p>

In this way the maximum demand availed in any one half an hour during a month is reckoned for maximum demand billing and cannot be correlated to the consumptionfor the entire month.<p>

You acn appreciate how you may be forced to pay penalty for higher maximum demand on KVA ,if you failed to switch on capacitor bank depending on your load, or if the capacitor bank tripped/ gone out of control for more than half an hour

There are Maximum demand controllers available in market to raise alarm as well as to control the maximum demand by tripping the unimportant loads for a short duration

There is a good chance that your utility company records your demand for every period during the month. They may use a 15 minute interval or a 30 minute interval or some other length, but they should be able to tell you what your demand was for every interval during the month. Ask them to give you the interval data for the month. They may give you raw data or they may make a graph. Anyhow, this should show you what your maximum demand was and when it occurs. For one thing, no load is ever the same all the time, 24/7. Even a single piece of equipment will vary sometime during the month. Once you know when you hit the maximum demand you can look at what is happening at that time, such as a fire pump test or other short term application. Maybe you can schedule that to occur during a period when your demand is typically lower. Motor starts only last for a very short time and do not affect maximum demand, since they are not on long enough. If your interval data says your demand never exceeds 4850 kW (not kWh) and they are billing you for 6374 kW, then ask them to explain why. It might be that you have a contract or a rate that has a minumum demand level.

Guys, Maximum Demand is measured in kVA and not in kW. This is because it needs to encourage the user to improve his Power Factor to reduce his max demand for the same kW input.

I thing there is some confusion here from the OP. We need more clarity about what he is looking at.

- (4850 kWh all the time 24 hrs 7 52) this is meaningless! If he said kW constant fixed usage over the same 24x7x52, then we might understand and be able to work out something (not necessary solving the issue...).

- Maximum demand kVA is, as already said by others, a measurement made over a specific time interval, and accumulated during a billing period to give an average of the peak demand. etc.

LOL dude, kVA and kW are the same value.. look up ohm's law

Watts= Volts X Amperes

kW=kVA

Brian, Welcome to CR4, where one of things you'll find here are knowledgeable people who are fanatic about fact checking, so a little piece of advice, check your facts before posting.

In AC power circuits your statement that kW=kVA is only true under one circumstance; i.e., when the power factor (pf) is equal to one. This only occurs when an AC system is supplying a purely resistive load, a relatively rare event since power systems have lots of things with coils of wire and/or space between conductors.

So remember, dude, that kW=abs(kVA x pf), it makes a big difference....

M.D. cannot be calculated. It has to be measured (in fact recorded) with a Maximum Demand Indicator (MDI meter).

This meter constantly measures instant values of load in KW. The highest value measured over period of time, say 30 minutes, is shifted to M.D. register. If a value higher than that is recorded in any next period, then that replaces the KW recorded in M.D. register and so on. In this way, M.D. register always has the record of highest KW (load) applied by the user during a billing cycle.

The electricity supply company bills fixed charges based on this M.D. (in two part tariff). At the end of billing cycle, the meter reader "resets" this register to zero and fresh cycle of recording starts.

It is true that (actual) maximum demand cannot (readily) be calculated, but a person / engineer can consider what the maximum demand could be for a given electrical system, and consider ways to reduce it.

I mean, the absolute maximum demand possible on a system is the total demand that would occur if all loads connected to the system were running at maximum load at the same time.

So, you can think about your system--if the OP says that his load is 4850Kw all the time 24 hrs x 7 x 52, is that based on all the connected loads running full out?

Or are there other loads that are connected but he thinks (or assumes) are never turned on? They aren't? Is he sure?

On another note, I'm pretty sure maximum demand is measured in kva, not kw. Thus, the steady load in kw has to be adjusted for the power factor.

If the maximum demand is (a steady) 6347 kva, his (steady) power factor is 4850 / 6347 = 0.76 which is not an outrageously low power factor. I mean, it is quite possible that is the actual power factor for his system.

If the power factor is that low, he should consider means of power factor correction--there is probably a payoff.

I rate this GA, but not perfect. The OP said his utility bill said his MD was in KW. You raise a good point that if it is actually kVA and his own readings are kW then both are correct and he just needs to adjust his power factor. If both are kW then he still needs to find out what is wrong. I spent 30 years with one of the largest electric utility companies in the US and have been associated with another for over 9 years. MD is not always metered or billed in kVA. It depends upon the rate, the class of customer, and the jurisdiction of the regulatory agency. Many munis and coops bill only in kW, not matter how big their customers are. Some utilities bill in kW but charge a penalty for poor power factor. Some do bill in kVA. Some bill a kW demand and a kVAr demand. The OP should simply discuss this with the utility company for a better explanation.

dear,

Lot said.

But to cross check, the meter reading, only to take the judgement of the accuracy / correctness of the meter,

1. Measure the peak load current in the process, by maintaining the log book , & daily periodical recording of the current meter.

Then, MD = I amp max. recorded * 1.732 * 0.415 KV = ____ KVA MD

ALTERNATE :

Please furnish us the following details-

1. Connected load in factory in KW - all motors / lights / heaters

2. Average PF maintained in factory = 0.96 assumed , if no data available

Then, MD = connected load KW * (Load factor * Diversity factor)

___________________________________________ KVA
Powert factor

MD is not an average parameter. It is the maximum of average recorded for the period of 20 min. time intervals packets.