Directional Overcurrent Protection (ANSI 67)

Presentation

Due to its ability to detect the direction of a short-circuit current, directional overcurrent protection helps to protect an installation against short-circuit currents that could circulate in both directions through the circuit breaker.

There are two independent protections:

• Forward directional overcurrent

• Reverse directional overcurrent

Directional overcurrent protection helps to protect the installation against phase-to-phase, phase-to-neutral, and phase-to-earth short circuits with total selectivity.

The ANSI 67 - Directional overcurrent protection Digital Module is used to generate either an alarm or a trip.

Prerequisites

Directional overcurrent protection is available when the ANSI 67 - Directional overcurrent protection Digital Module is purchased and installed on the MicroLogic control unit.

Directional overcurrent protection requires an external 24 Vdc power supply.

Directional overcurrent protection is compatible with the following control units:

• MicroLogic 2.0 X, 5.0 X, 6.0 X, and 7.0 X control units for IEC standard

• MicroLogic 3.0 X, 5.0 X, and 6.0 X control units for UL standard

• MicroLogic X control units with firmware version greater than or equal to 004.000.000. Earlier firmware versions need to be updated.

Data from the Digital Module is available remotely through IFE/EIFE or IFM communication interfaces, if the IFE/EIFE or IFM firmware version is compatible with the Digital Module. For more information, refer to firmware compatibility of the communication interfaces.

Operating Principle

Directional overcurrent protection is based on the true RMS current of phases and neutral, up to harmonic 40.

Directional overcurrent protection is implemented independently for each phase and for neutral when neutral is present.

Directional overcurrent protection:

• Is an overcurrent time-independent protection.

• Detects the direction of the short-circuit current.

Directional overcurrent protection trips if the following conditions are met:

• The value of the current exceeds the setting (Ifw or Irv).

• The associated time delay (tfw or trv) is elapsed.

• The direction of the short-circuit current is detected:

  • From the top connection to the bottom connection of the circuit breaker: forward directional overcurrent protection trips

  • From the bottom connection to the top connection of the circuit breaker: reverse directional overcurrent protection trips

Inhibiting Protection

To inhibit the forward or reverse directional overcurrent protections, both the following conditions must be met:

• Inhibition is enabled by setting the Inhibition parameter to ON. Inhibition is enabled independently on each protection (forward and reverse).

• Inhibition of optional protections is activated by an input of the IO module. The function Inhibit Optional Protection must be assigned to an input of the IO module.

For more information about inhibiting optional protections, refer to Enerlin'X IO - Input/Output Application Module for One Circuit Breaker - User Guide.

Setting the Protection

The forward directional overcurrent protection settings are:

• Ifw mode: enables (ON) or disables (OFF) the forward directional overcurrent

• Ifw action: sets the result of forward directional overcurrent protection as trip or alarm

  • Trip: the circuit breaker trips and three events are generated (start, operate, and trip)

  • Alarm: two events are generated (start and operate)

• Ifw inhib: enables (ON) the forward directional overcurrent to be inhibited by IO module

• Ifw: forward directional overcurrent protection threshold

• tfw: forward directional overcurrent protection time delay

The reverse directional overcurrent protection settings are:

• Irv mode: enables (ON) or disables (OFF) the reverse directional overcurrent

• Irv action: sets the result of reverse directional overcurrent protection as trip or alarm

  • Trip: the circuit breaker trips and three events are generated (start, operate, and trip)

  • Alarm: two events are generated (start and operate)

• Irv inhib: enables (ON) the reverse directional overcurrent to be inhibited by IO module

• Irv: reverse directional overcurrent protection threshold

• trv: reverse directional overcurrent protection time delay

They can be set as follows:

• With EcoStruxure Power Commission software (password-protected)

• With EcoStruxure Power Device app (password-protected)

The dual settings function does not apply to directional overcurrent protection. When the dual settings function is enabled, directional overcurrent protection settings are the same whether set A or set B settings are activated.

Protection Settings

For more information, refer to the setting guidelines.

Operating Times at 10 x Ifw or 10 x Irv

The operating times of directional overcurrent protection depend on the tfw or trv time delay.

Protection Characteristics

The accuracy of Ifw and Irv is ±10%.

Characteristics of directional overcurrent protection:

• Time-independent

• Hysteresis: fixed 98%

Predefined Events

The function generates the following predefined events:

Predefined events cannot be modified by the user. For general information about events, refer to Event management.

Protection events are generated as follows:

• The start event is generated when the protection picks up.

• The operate event is generated when the protection time delay elapses.

  The operate event is not generated when the optional protection is inhibited.

• The trip event is generated when the circuit breaker tripping voltage release (MITOP) activates.

  The trip event is not generated when:

  • The optional protection is set in alarm mode

  • The optional protection is inhibited

Recommended Actions

Resetting a Trip Event

For information about resetting the circuit breaker after a trip due to an electrical fault, refer to the relevant document:

• MasterPacT MTZ1 - Circuit Breakers and Switch-Disconnectors - User Guide

• MasterPacT MTZ2/MTZ3 - Circuit Breakers and Switch-Disconnectors - User Guide