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:

oForward directional overcurrent

oReverse 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:

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

oMicroLogic 3.0 X, 5.0 X, and 6.0 X control units for UL standard

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

NOTE: On MicroLogic 2.0 X and 3.0 X control units, directional overcurrent protection has limited advantages due to the fact that the instantaneous protection cannot be set to OFF. For more information, refer to the setting guidelines.

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:

oIs an overcurrent time-independent protection.

oDetects the direction of the short-circuit current.

Directional overcurrent protection trips if the following conditions are met:

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

oThe associated time delay (tfw or trv) is elapsed.

oThe direction of the short-circuit current is detected:

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

oFrom 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:

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

oInhibition 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:

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

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

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

oAlarm: two events are generated (start and operate)

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

oIfw: forward directional overcurrent protection threshold

otfw: forward directional overcurrent protection time delay

The reverse directional overcurrent protection settings are:

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

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

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

oAlarm: two events are generated (start and operate)

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

oIrv: reverse directional overcurrent protection threshold

otrv: reverse directional overcurrent protection time delay

They can be set as follows:

oWith EcoStruxure Power Commission software (password-protected)

oWith 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:

oTime-independent

oHysteresis: 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:

oThe start event is generated when the protection picks up.

oThe operate event is generated when the protection time delay elapses.

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

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

The trip event is not generated when:

oThe optional protection is set in alarm mode

oThe 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:

oMasterPact MTZ1 - Circuit Breakers and Switch-Disconnectors - User Guide

oMasterPact MTZ2/MTZ3 - Circuit Breakers and Switch-Disconnectors - User Guide