Alarm Monitoring of the cos ϕ and Power Factor

Managing the cos ϕ and Power Factor PF

Monitoring of the cos ϕ and power factor PF indicators depends on the sign convention selected for the power factor PF: IEEE or IEC convention.

NOTE: The alarm type associated with the indicators - for example, leading PF (IEEE) (code 31) or lead/lag PF (IEC) (code 33) - must be consistent with the sign convention selected (IEEE or IEC) for the PF indicator.

Select the sign convention for the PF indicator:

With EcoStruxure Power Commission software (password-protected)
By sending a setting command using the communication network (password-protected)

The IEEE convention is the factory setting.

Indicator Maximum and Minimum Values

The maximum value of the PF MAX or (cos ϕ MAX) indicator is obtained for the smallest positive value of the PF (or cos ϕ) indicator.
The minimum value of the PF MIN or (cos ϕ MIN) indicator is obtained for the largest negative value of the PF (or cos ϕ) indicator.

Electrical Distribution Monitored According to IEEE Convention

The following example describes monitoring of the energy quality by the cos ϕ indicator.

The following table gives the history of the cos ϕ values of the load of a workshop downstream of a ComPact NSX circuit breaker according to IEEE convention:

Time	Evolution of the load	IEEE convention
Time	Evolution of the load	cos ϕ	cos ϕ MIN	cos ϕ MAX
t1 = 8 h 00 min	Power startup	- 0.4	- 0.4	- 0.4
t2 = 8 h 01 min	Compensation system startup	- 0.9	- 0.4	- 0.9
t3 = 9 h 20 min	Power stops	+ 0.3	- 0.4	+ 0.3
t4 = 9 h 21 min	Compensation system stops	- 0.95	- 0.4	+ 0.3

Interpreting the cos ϕ MIN/MAX and the cos ϕ Values According to IEEE Convention

The cos ϕ MIN and cos ϕ MAX values correspond to the cos ϕ variation range for the load. This provides the user with information on how the equipment is performing from a cost point of view and allows the installation of compensation devices, if necessary. The cos ϕ MIN and cos ϕ MAX values can be accessed on the FDM121 display.

The load cos ϕ values indicate in real time any correction actions:

The absolute value of too low a negative cos ϕ (= - 0.4) indicates that capacitors need to be installed to increase the value of the equipment cos ϕ.
The value of too low a positive cos ϕ (= + 0.3) indicates that capacitors need to be removed to increase the value of the equipment cos ϕ.

The two alarms on the cos ϕ according to IEEE convention integrated in the MicroLogic trip unit are used to monitor the two critical situations automatically.

Electrical Distribution Monitored According to IEC Convention

The following table gives the history of the cos ϕ values of the load of a workshop downstream of a ComPact NSX circuit breaker according to IEC convention:

Time	Evolution of the load	IEC convention
Time	Evolution of the load	cos ϕ	cos ϕ MIN	cos ϕ MAX
t1 = 8 h 00 min	Power startup	+ 0.4	+ 0.4	+ 0.4
t2 = 8 h 01 min	Compensation system startup	+ 0.9	+ 0.9	+ 0.4
t3 = 9 h 20 min	Power stops	+ 0.3	+ 0.9	+ 0.3
t4 = 9 h 21 min	Compensation system stops	+ 0.95	+ 0.95	+ 0.3

Interpreting the cos ϕ MAX and the cos ϕ Values According to IEC Convention

The cos ϕ MAX value corresponds to the minimum value of the load cos ϕ, whether leading or lagging. This provides user information on how the equipment is performing from a cost point of view.

Do not use just the value of cos ϕ to decide whether to install inductances or capacitors to increase its value.

If a critical situation occurs, the alarm on the cos ϕ sends an alert according to IEC convention integrated in the MicroLogic trip unit. Use this alarm, associated with an alarm defining the type of load or the operating quadrant, to monitor the two critical situations automatically.

Setting the cos ϕ Alarms According to IEEE Convention

Monitor the cos ϕ indicator to manage the power:

When the power starts, too high a value of cos ϕ (lagging), for example higher than -0.6, results in penalties. The capacitive compensation value determines the value of the Qfund reactive power.
When the power stops, too low a value of cos ϕ (leading), for example less than +0.6, results in penalties. Disconnect the capacitive compensation element.

Two alarms monitor the indicators:

Alarm 124 (monitoring of the lagging cos ϕ) on an overvalue condition for operation in quadrant 1 (inductive reactive energy consumed)
Alarm 121 (monitoring of the leading cos ϕ) on an undervalue condition for operation in quadrant 4 (capacitive reactive energy consumed)

Set the parameters for monitoring the cos ϕ (alarms 121 and 124) according to IEEE convention with EcoStruxure Power Commission software.

Setting the SDx Outputs

The two alarms defined can each be associated with an SDx module output:

With output Out1, alarm code 124 (monitoring of the lagging cos ϕ)
With output Out2, alarm code 121 (monitoring of the leading cos ϕ)

On starting the power at t2, the inductive load (lagging) is too high and output Out1 is activated (the output must be configured in permanent latching mode). The MicroLogic trip unit display shows:

Acknowledging the Out1 Screen

The Out1 screen can only be acknowledged if the alarm is no longer active.

After startup of the capacitive compensation, the alarm is no longer active. Press the key twice (validation and confirmation) to acknowledge Out1 output.