Calculating Demand Values (MicroLogic E)

Presentation

The MicroLogic E trip unit calculates:

• The demand values of phase, neutral, and residual currents

• The demand values of the active, reactive, and apparent powers

Each maximum demand value (peak) is stored in memory.

The demand values update according to the type of window.

Definition

The demand value of a quantity is an average value calculated over a defined interval.

The demand value of a quantity can be called the:

• Average/mean value (over an interval)

• Demand

• Demand value (over an interval)

Demand Value Models

The demand value of a quantity over a defined interval (metering window) is calculated according to two different models:

• Arithmetic demand value for the powers

• Quadratic demand value (thermal image) for the currents

Metering Window

The specified time interval T is chosen according to three types of metering windows:

• Fixed window

• Sliding window

• Synchronized window

Fixed Metering Window

The duration of the fixed metering window can be set from 5 to 60 minutes in increments of one minute.

By default, the duration of the fixed metering window is 15 minutes.

At the end of each fixed metering window:

• The demand value over the metering window is calculated and updated.

• Calculation of a new demand value is initialized on a new metering window.

Sliding Metering Window

Set the duration of the sliding metering window from 5 to 60 minutes in increments of one minute.

By default, the duration of the sliding metering window is 15 minutes.

At the end of each sliding metering window and then once a minute:

• The demand value over the metering window is calculated and updated.

• Calculation of a new demand value is initialized on a new metering window:

  • By eliminating the contribution of the first minute of the previous metering window

  • By adding the contribution of the current minute

Synchronized Metering Window

Synchronization is done using the communication network.

When the synchronization pulse is received:

• The demand value over the synchronized metering window is recalculated.

• A new demand value is calculated.

Quadratic Demand Value (Thermal Image)

The quadratic demand value model represents the conductor heat rise (thermal image).

The heat rise created by the current I(t) over the time interval T is identical to the heat rise created by a constant current Ith over the same interval. Ith represents the thermal effect of the current I(t) over the interval T. If the period T is infinite, the current Ith represents the thermal image of the current.

The demand value according to the thermal model is calculated on a sliding metering window.

Arithmetic Demand Value

The arithmetic demand value model represents the consumption of electricity and the associated cost.

The demand value according to the arithmetic model can be calculated on any type of metering window.

Peak Demand Value

The MicroLogic E trip unit indicates the maximum value (peak) reached over a defined period for:

• The demand values of the phase, neutral, and residual currents

• The demand values of the active, apparent, and reactive powers

The demand values are organized into two groups:

• Current demand values

• Power demand values

Resetting Peak Demand Values

Reset the peaks in a group:

• By sending a reset command using the communication network (password-protected)

• On the FDM121 display