Ground-Fault Alarm (ANSI 51N/51G) - MicroLogic X User Guide

Presentation

The ground-fault alarm and earth-leakage alarm functions operate as ground-fault and earth-leakage protections, using the same sensors. They are independent from these protections and have their own settings.

The ground-fault alarm is based either on the summation of the phases and neutral current or on the signal delivered by an external sensor, an external neutral current transformer (ENCT), or a source ground return (SGR) current transformer through the MDGF module.

The earth-leakage alarm function is a residual current alarm based on the current measured by a rectangular sensor encompassing the three phases or the three phases and the neutral.

Prerequisites

The ground-fault alarm function is available when the ANSI 51N/51G Ground-fault alarm Digital Module is purchased and installed on the MicroLogic control unit.

The ground-fault alarm function is powered by the current flowing through the internal current transformers of the circuit breaker and it does not require an additional external power supply.

The ground-fault alarm function is compatible with:

3-pole and 4-pole circuit breakers
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 002.000.002. 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.

NOTE: When installed on a MicroLogic 7.0 X control unit, the ANSI 51N/51G Ground-fault Alarm Digital Module activates the earth-leakage alarm.

External sensors can be used:

External Neutral Current Transformer (ENCT): measurement of the current on neutral. For information about the installation of ENCT, consult the instruction sheet on the Schneider Electric website: NHA14388.
Source ground return protection: including ground-fault protection and an SGR sensor installed around the connection of the transformer neutral point to ground. For information about the installation of the SGR sensor, consult the instruction sheet on the Schneider Electric website: NHA92405.
External rectangular sensor: measurement of the residual current. For information about the installation of the external rectangular sensor, consult the instruction sheet on the Schneider Electric website: NVE35468.

Operating Principle

Ground-fault alarm operates in the same way as ground-fault protection, except that an alarm is generated instead of a trip.

Setting the Function

The ground-fault alarm settings for MicroLogic 2.0 X, 3.0 X, 5.0 X, and 6.0 X are:

Ig alarm mode: enables or disables ground-fault alarm
Ig alarm: ground-fault alarm threshold
tg alarm: ground-fault alarm time delay

The earth-leakage alarm settings for MicroLogic 7.0 X for IEC Standard are:

IΔn alarm mode: enables or disables earth-leakage alarm
IΔn alarm: earth-leakage alarm threshold
Δt alarm: earth-leakage alarm 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 the ground-fault alarm function. When the dual settings function is enabled, ground-fault alarm settings are the same whether set A or set B settings are activated.

Function Settings

Ground-fault alarm settings on MicroLogic 2.0 X, 5.0 X, and 6.0 X IEC standard:

Setting	Unit	Range	Step	Factory setting	Accuracy
Ig alarm mode	–	ON/OFF	–	OFF	–
Ig alarm	A	0.2–1 x In	1	0.2 x In	±10%
tg alarm	s	1–10	0.1	1	±500 ms

Ground-fault alarm settings on MicroLogic 3.0 X, 5.0 X, and 6.0 X UL standard:

Setting	Unit	Range	Step	Factory setting	Accuracy
Ig alarm mode	–	ON/OFF	–	OFF	–
Ig alarm	A	120–1200	1	120	±10%
tg alarm	s	1–10	0.1	1	±500 ms

Earth-leakage alarm settings on MicroLogic 7.0 X IEC standard

Setting	Unit	Range	Step	Factory setting	Accuracy
IΔn alarm mode	–	ON/OFF	–	OFF	–
IΔn alarm	A	0.5–22	0.1	0.5	Complies with IEC 60947-2 Annex B
Δt alarm	s	1–10	0.1	1	±2%

NOTE: In order to differentiate between earth-leakage alarm and earth-leakage fault, it is recommended to set the earth-leakage alarm threshold below 75% of the earth-leakage fault threshold.

Predefined Events

The function generates the following predefined event for MicroLogic 2.0 X, 3.0 X, 5.0 X, and 6.0 X control units:

Code	Event	History	Severity
0x050C (1292)	Ig alarm	Protection	Medium

The Ig alarm event is not generated when the Ig alarm mode is OFF.

The function generates the following predefined event for MicroLogic 7.0 X control units:

Code	Event	History	Severity
0x050D (1293)	IΔn alarm	Protection	Medium

The IΔn alarm event is not generated when the IΔn alarm mode is OFF.

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

Recommended Actions

Code	Event	Recommended actions
0x050C (1292)	Ig alarm	Check insulation between phase/neutral and ground (earth).
0x050D (1293)	IΔn alarm	Check insulation between phase/neutral and ground (earth).