ANSI protective functions

The ANSI protective functions are functions present in protective devices such as a relay. They are identified by the ANSI standard device numbers (ANSI / IEEE Standard C37.2 Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations). The objective of these functions is to protect electrical systems and components from damage when an unwanted event occurs.

27 Undervoltage

The 27 Undervoltage device provides protection against voltage sags or detection of abnormally low network voltage to trigger automatic load shedding or source transfer.

Table 1. 27 Undervoltage protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal line voltage [V] Undervoltage threshold [p.u.] Undervoltage trip delay [s] Execution rate [s]

Inputs and outputs

The 27 Undervoltage protection function needs 2 default and 1 optional inputs to operate.

The 27 Undervoltage protection function has 6 outputs.

Parameters

The 27 Undervoltage protection function has 4 general parameters and 4 advanced options.

32 Directional Power

The Directional Power device provides protection to limit the flux of power flowing in a determinate direction.

Table 2. 32Directional Power protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal power [W] Directional power threshold [p.u.] Directional power trip delay [s] Execution rate [s]

Inputs and outputs

The 32 Directional Power protection function needs 2 default and 1 optional inputs to operate.

The 32 Directional Power protection function has 3 outputs.

Parameters

The 32 Directional Power protection function has 4 general parameters and 3 advanced options.

32L Low Forward Power

The Low Forward Power device provides detection of a power flow below the defined threshold. Can be used to invalidate an operator's open breaker command when a generator is providing high power to the network.

Table 3. 32LLow Forward Power protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal power [W] Low forward power threshold [p.u.] Low forward power trip delay [s] Execution rate [s]

Inputs and outputs

The 32L Low Forward Power protection function needs 2 default and 1 optional inputs to operate.

The 32L Low Forward Power protection function has 3 outputs.

Parameters

The 32L Low Forward Power protection function has 4 general parameters and 3 advanced options.

50 Instantaneous Overcurrent

The 50 Instantaneous Overcurrent device provides instantaneous protection against high currents.

Table 4. 50 Instantaneous Overcurrent protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal current [A] Instantaneous overcurrent threshold [p.u.] Execution rate [s]

Inputs and outputs

The 50 Instantaneous Overcurrent protection function needs 2 default and 1 optional inputs to operate.

The 50 Instantaneous Overcurrent protection function has 5 outputs.

Parameters

The 50 Instantaneous Overcurrent protection function has 3 general parameters and 3 advanced options.

50N Neutral Instantaneous Overcurrent

The 50N Neutral Instantaneous Overcurrent device provides instantaneous protection against high neutral currents.

Table 5. 50N Neutral Instantaneous Overcurrent protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal current [A] Neutral instantaneous overcurrent threshold [p.u.] Execution rate [s]

Inputs and outputs

The 50N Neutral Instantaneous Overcurrent protection function needs 2 default and 1 optional inputs to operate.

The 50N Neutral Instantaneous Overcurrent protection function has 2 outputs.

Parameters

The 50N Neutral Instantaneous Overcurrent protection function has 3 general parameters and 2 advanced options.

51 AC Inverse Time Overcurrent

The 51 AC Inverse Time Overcurrent device provides protection against high currents based on a time vs. current curve.

Table 6. 51 AC Inverse Time Overcurrent protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal current [A] AC inverse time overcurrent threshold [p.u.] AC inverse time overcurrent time dial [p.u.] AC inverse time overcurrent curve type (combo) Reset dial position based on current magnitude (checkbox) Execution rate [s]

Inputs and outputs

The 51 AC Inverse Time Overcurrent protection function needs 2 default and 1 optional inputs to operate.

The 51 AC Inverse Time Overcurrent protection function has 3 outputs.

Parameters

The 51 AC Inverse Time Overcurrent protection function has 6 general parameters and 2 advanced options.

When the AC inverse time overcurrent curve type is set to Custom Curve a new tab named Curve Definition appears. The properties on this tab are used in the trip and reset curves.

Trip curve: $t_{TRIP}=TimeDial*\left(\frac{A}{\left(M^P-1\right)}+B\right)$

Reset curve: $t_{RESET}=TimeDial*\left(\frac{C}{\left(1-M^{Pr}\right)}\right)$

51N Neutral AC Inverse Time Overcurrent

The 51N Neutral AC Inverse Time Overcurrent device provides protection against high currents based on a time vs. current curve.

Table 7. 51N Neutral AC Inverse Time Overcurrent protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal current [A] Neutral AC inverse time overcurrent threshold [p.u.] Neutral AC inverse time overcurrent time dial [p.u.] Neutral AC inverse time overcurrent curve type (combo) Reset dial position based on current magnitude (checkbox) Execution rate [s]

Inputs and outputs

The 51N Neutral AC Inverse Time Overcurrent protection function needs 2 default and 1 optional inputs to operate.

The 51N Neutral AC Inverse Time Overcurrent protection function has 3 outputs.

Parameters

The 51N Neutral AC Inverse Time Overcurrent protection function has 6 general parameters and 2 advanced options.

When the AC inverse time overcurrent curve type is set to Custom Curve a new tab named Curve Definition appears. The properties on this tab are used in the trip and reset curves.

Trip curve: $t_{TRIP}=TimeDial*\left(\frac{A}{\left(M^P-1\right)}+B\right)$

Reset curve: $t_{RESET}=TimeDial*\left(\frac{C}{\left(1-M^{Pr}\right)}\right)$

59 Overvoltage

The 59 Overvoltage device provides protection against voltage swells.

Table 8. 59 Overvoltage protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal line voltage [V] Overvoltage threshold [p.u.] Overvoltage trip delay [s] Execution rate [s]

Inputs and outputs

The 59 Overvoltage protection function needs 2 default and 1 optional inputs to operate.

The 59 Overvoltage protection function has 6 outputs.

Parameters

The 59 Overvoltage protection function has 4 general parameters and 4 advanced options.

59N Neutral Overvoltage

The 59N Neutral Overvoltage device provides protection against voltage swells.

Table 9. 59N Neutral Overvoltage protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal line voltage [V] Neutral Overvoltage threshold [p.u.] Neutral Overvoltage trip delay [s] Execution rate [s]

Inputs and outputs

The 59N Neutral Overvoltage protection function needs 2 default and 1 optional inputs to operate.

The 59N Neutral Overvoltage protection function has 3 outputs.

Parameters

The 59N Neutral Overvoltage protection function has 4 general parameters and 3 advanced options.

81O Over Frequency

The 81O Over Frequency device provides protection against frequency swells.

Table 10. 81O Over Frequency protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal frequency [Hz] Over frequency threshold [p.u.] Over frequency trip delay [s] Execution rate [s]

Inputs and outputs

The 81O Over frequency protection function needs 2 default and 1 optional inputs to operate.

The 81O Over frequency protection function has 3 outputs.

Parameters

The 81O Over Frequency protection function has 4 general parameters and 3 advanced options.

81RF Fast Rate-of-Change of Frequency

The 81RF Fast Rate-of-Change of Frequency device provides protection against fast changes in frequency.

Table 11. 8RF Fast Rate-of-Change of Frequency protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal frequency [Hz] Frequency rate estimation interval [s] Minimum frequency difference [Hz] Frequency difference at rate = 0 [Hz] Minimum frequency rate [Hz/s] Frequency rate at difference = 0 [Hz/s] Pickup Delay [s] Dropout Delay [s] Execution rate [s]

Inputs and outputs

The 81RF Fast Rate-of-Change of Frequency protection function needs 2 default inputs and 1 optional to operate.

The 81RF Fast Rate-of-Change of Frequency protection function has 3 outputs.

Parameters

The 81RF Fast Rate-of-Change of Frequency protection function has 9 general parameters and 3 advanced options.

81U Under Frequency

The 81U Under Frequency device provides protection against frequency swells.

Table 12. 81U Under Frequency protective function in the Schematic Editor core library

component	component dialog window	component parameters
		Nominal frequency [Hz] Under frequency threshold [p.u.] Under frequency trip delay [s] Execution rate [s]

Inputs and outputs

The 81U Under frequency protection function needs 2 default and 1 optional inputs to operate.

The 81U Under frequency protection function has 3 outputs.

Parameters

The 81U Under Frequency protection function has 4 general parameters and 3 advanced options.

External Trip

The External Trip device provide a relay a feature to receive trip commands from an external protective function.

Table 13. External Trip function in the Schematic Editor core library

component	component dialog window	component parameters
		Pickup Delay [s] Dropout Delay [s] Execution rate [s]

Inputs and outputs

The External Trip function needs 2 default and 1 optional inputs to operate.

The External Trip function has 3 outputs.

Parameters

The External Trip function has 3 default parameters and 3 advanced options.

Example

Overall behavior and control methodologies can be better understood with the use of the given ANSI protective functions example:

Model name: protective_functions.tse

SCADA interface: SCADA_Panel.cus

Path: /examples/models/microgrid/protective_ansi_functions/