The maximum demand in kW/kVA, mean average kW/kVA supplied during consecutive 30/15 minutes period of maximum use.
MD : Maximum Power demand is the ratio of Accumulated energy during a specified period by Length of that period.
Diffenent Utility network follow different methods of Maximum Demand control methods. There are mainly 3 type of Power Demand Calculation methods :
- A : Block Interval Demand
- B : Synchronized Demand
- C : Thermal Demand
A: Block Interval Demand
Block interval Demand method, a specified period of time inteval – Block, that is used for Demand calculation. Block Interval demand method to calculate Maximum Demand can be further classified into 3 sub method, depending on how that time Block can be handled.
- A.1 : Fixed Window – Timed Block method
- A.2 : Sliding Window – Timed Sliding Block method
- A.3 : Rolling Window – Timed Rolling Block method
In all three methods, Maximum Demand value is the average demand for last comleted Block.
A.1 : Fixed Window – Timed Block method
In this Method, Maximum Demand is calculated at the end of each Fix Timed Block generally 15 minute block. It may be different for different Utility ranging from (1 to 60 minutes).
A.2 : Sliding Window – Timed Sliding Block method
In this Method, Maximum Demand is calculated at the end of each Interval defined for timed Block. A Timed Block keeps on sliding forward at the end of each interval defined. Maximum Demand is calculated and updated at the end of each Interval.
A.3 : Rolling Window – Timed Rolling Block method
In this method, Block is further divided into equal sub blocks. Eg. 15 Minute Block is divided in to 5 minuites of sub blocks. Maximum Demand is updted at the end of each sub Blocks. And Maximum Demand is the Average of each sub blocks. In this case Block keeps rolling every defined sub block.
B : Synchronized Demand
When Multiple Points of MD Calculations are there, or When MD Calculations in the Field are to be compared or varified with utility Meter, Blocks and Intervals defined in above mentioned methods of Maximum Demad calculation, further need to be Synchronized with each other, which can be done by following Ways:
- B.1 : Clock Synchronization Method.
- B.2 : Input Comand Synchronization Method.
B.1 : Clock Synchronization method
In this, Real time clock in each Maximum Demand Control Meters or Relay can be Synchronized with each other, so that, when Maximum Demand is calculated and updated at Either Utility Meter or Meter at Sub Distribution level each are calculate with same Reference Time.
B.2 : Input Comand Synchronization Method
In this method, each Maximum Demand Control Meters or Relay can be Synchronized by way of Either IO contact OR by Soft comand over Communication Bus on Modbus/Ethernet.
C : Thermal Demand
This method uses same principle similar Thermal over load Relays, where Thermal Element deflects depending current flow, In this case Electro-Mechnical Maximum Demand Control Meters gives command for Demand Power at the end of defined time block. This method is not relavant now a days.